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Influence of preservative treatment on durability of ACA-treated white spruce poles Kim, Won Jang 1984

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INFLUENCE OF PRESERVATIVE TREATMENT ON DURABILITY OF ACA-TREATED WHITE SPRUCE POLES by WON JANG KIM B.Sc.F., University of Toronto, 1981 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n THE FACULTY OF GRADUATE STUDIES (FACULTY OF FORESTRY) We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA A p r i l , 1985 ® Won Jang Kim, 1985 In presenting t h i s thesis i n p a r t i a l f u l f i l m e n t of the requirements for an advanced degree at the University of B r i t i s h Columbia, I agree that the Library s h a l l make i t f r e e l y available for reference and study. I further agree that permission for extensive copying of t h i s thesis for scholarly purposes may be granted by the head of my department or by h i s or her representatives. I t i s understood that copying or publication of t h i s thesis for f i n a n c i a l gain s h a l l not be allowed without my written permission. Department of Forestry  The University of B r i t i s h Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date A p r i l 25, 1985 ABSTRACT In 1977, sixty-two white spruce pole sections were i n -s t a l l e d at the Western Forest Products Laboratory's Westham Island test f i e l d s i t e . They had been commercially pressure-impregnated with amirioniacal copper arsenate (ACA) or penta-chlorophenol (PCP). Twenty-four of the ACA-treated spruce poles were studied to determine the influence of preserva-t i v e penetration, retention, and nitrogen l e v e l on decay resistance of spruce poles a f t e r seven years of f i e l d t e s t i n g . Such information was considered of great value i n establishing treated spruce as viable pole material i n Canada. Studies using a 0.5% solution of chrome azurol S i n d i -cated that for the ACA-treated spruce poles a f t e r seven years in test, average preservative penetration of 1.14 i n . (2.90 cm) was generally greater than that required by Cana-dian standards. However, analysis using energy-dispersive X-ray spectrometry showed that the mean retention of 0.50 l b . / f t . 3 (8.06 kg/m3) was less than the l e v e l of 0.6 l b . / f t . 3 (9.6 kg/m3) for ACA, required by the CSA standard. It was also found that copper was present i n greater quantity than arsenic, i n spite of t h e i r equal presence i n the o r i g i n a l ACA treating solution. In microbiological studies, a t o t a l of seventy-one fungal i s o l a t e s belonging to seventeen genera and four taxa were i d e n t i f i e d to genus, with f i f t e e n of these i d e n t i f i e d as to species. Unlike the untreated control poles, true wood-decaying Basidiomycetes were not found associated with the ACA-treated spruce poles. Analysis employing an Orion ammonia-specific electrode coupled to an Orion Microprocessor ionalyser 901 revealed that nitrogen content due to ACA treatment was s i g n i f i c a n t l y increased i n the treated zone and also beyond the penetra-t i o n l i m i t of preservative. A l i n e a r r elationship existed between nitrogen content and chemical retention i n the f i r s t a n a l y t i c a l zone. Variation i n moisture content above the f i b e r satura-tion point produced marked changes i n e l e c t r i c a l resistance as detected by Shigometer measurements. The p r a c t i c a l application of the Shigometer for detection of i n t e r n a l decay i s limited by such inconsistences. i v TABLE OF CONTENTS Page ABSTRACT i i TABLE OF CONTENTS i v LIST OF TABLES v i i i LIST OF FIGURES X ACKNOWLEDGEMENTS x i i 1.0 INTRODUCTION 1 1.1 CHEMICAL DISTRIBUTION STUDY 5 1.2 BIOLOGICAL STUDY 6 1.3 NITROGEN ENHANCEMENT STUDY 8 1.4 SHIGOMETER STUDY 10 2.0 LITERATURE REVIEW 12 2.1 SUPPLY AND DEMAND FOR UTILITY POLES IN CANADA . 12 2.2 WHITE SPRUCE AS POTENTIAL POLE SPECIES 22 2.2.1 CHEMICAL, PHYSICAL AND MECHANICAL PROPERTIES OF WHITE SPRUCE 23 2.2.2 PROBLEMS ASSOCIATED WITH WHITE SPRUCE .... 30 2.3 FACTORS AFFECTING THE TREATABILITY OF SPRUCE ROUNDWOOD 35 2.3.1 MICROBIOLOGICAL STUDIES 35 2.3.2 PHYSICAL STUDIES 39 2.3.2.1 INCISING 39 Page 2.3.2.2 VARIATION OF THE TREATING CONDITIONS . 41 2.3.3 CHEMICAL STUDIES 43 2.4 PROTECTION OF POLES WITH WATERBORNE CHEMICALS . 45 2.4.1 CHROMATED COPPER ARSENATE (CCA) 47 2.4.2 AMMONIACAL COPPER ARSENATE (CCA) 51 2.4.2.1 CHEMICAL COMPOSITION AND FORMULATION . 51 2.4.2.2 MECHANISM OF FIXATION 53 2.5 FACTORS INFLUENCING THE EFFECTIVENESS OF PRESERVATIVE SYSTEMS ... 55 2.5.1 PENETRATION 56 2.5.2 RETENTION 59 2.5.3 TREATMENT RESULTS OF SPRUCE WITH AMMONIACAL WOOD PRESERVATIVES 61 2.6 BIODETERIORATION OF CHEMICALLY TREATED WOOD .. 69 2.6.1 DETOXIFICATION OR REMOVAL OF PRESERVATIVE CHEMICALS BY MICROORGANISMS 70 2.6.2 PRESERVATIVE TOLERANCE BY WOOD DECAYING FUNGI 73 2.7 NITROGEN ENHANCEMENT DUE TO ACA TREATMENT .... 76 2.8 FUNGAL METABOLISM OF NITROGEN 78 2.9 FUNCTION OF THE SHIGOMETER IN RELATION TO ELECTRICAL PROPERTIES OF INFECTED WOOD 85 3.0 MATERIALS AND METHODS 93 3.1 MATERIALS 93 3.2 METHODS 93 v i Page 3.2.1 SAMPLING METHODS 93 3.2.1.1 BIOASSAY 93 3.2.1.2 CHEMICAL ASSAY AND NITROGEN 97 3.2.1.3 SHIGOMETER 97 3.2.2 ANALYSIS OF CHEMICAL PENETRATION AND RETENTION 99 3.2.3 MICROBIOLOGICAL STUDIES 101 3.2.3.1 ISOLATION PROCEDURES 101 3.2.3.2 IDENTIFICATION AND GROUPING OF THE ISOLATES 106 3.2.4 DETERMINATION OF NITROGEN 108 3.2.5 SHIGOMETER MEASUREMENTS 109 4.0 RESULTS AND DISCUSSION I l l 4.1 CHEMICAL DISTRIBUTION STUDY I l l 4.1.1 PENETRATION I l l 4.1.2 RETENTION 115 4.1.3 DISTRIBUTION OF CHEMICAL COMPONENTS 123 4.2 BIOLOGICAL STUDY 127 4.3 NITROGEN ANALYSIS 138 4.4 EVALUATION OF THE SHIGOMETER 152 4.4.1 MOISTURE MEASUREMENTS 152 4.4.2 SHIGOMETER MEASUREMENTS 156 I. v i i Page 4.4.3 EFFECT OF MOISTURE CONTENT ON THE SHIGOMETER MEASUREMENTS 168 5.0 CONCLUSIONS 170 5.1 CHEMICAL STUDY 170 5.2 BIOLOGICAL STUDY 170 5.3 NITROGEN STUDY 171 5.4 SHIGOMETER STUDY 172 5.5 GENERAL 172 6.0 REFERENCES 174 APPENDIX A 195 v i i i LIST OF TABLES Table Page 1. Forest resources comparison (B.C. Ministry of Forests, 1979). 14 2. Trend i n u t i l i t y pole exports from B.C. (Sugden, 1979). 15 3. Trend i n t o t a l annual Canadian imports, exports, payments and receipts of u t i l i t y poles. 17 4. Chemical composition of six common co n i f e r -ous woods (Isenberg, 1980). 24 5. Physical properties of s i x common co n i f e r -ous woods. 26 6. Mechanical properties of s i x common conifers (Jessome, 1977). 28 7. Summary of pole strength t e s t s . 31 8. Composition of the CCA preservatives. 49 9. H i s t o r i c a l development of ACA composition. 52 10. Summary of n i t r a t e reduction (Nason, 1962; Nason and Takahashi, 1958; Nicholas, 1963). 81 11. Preservative penetration values determined for the ACA-treated spruce poles a f t e r seven years i n t e s t . 112 12. Analysis of ACA chemical retention. 116 13. Student t - t e s t between the mean current and previous (prior to i n s t a l l a t i o n ) t o t a l s . 122 14. Multiple regression analysis of the r a t i o of copper to arsenic for the retention i n the f i r s t a n a l y t i c a l zone. 125 ix Table Page 15. Identify and frequency of fungi is o l a t e d from 24 white spruce poles at Westham Island test f i e l d s i t e . 128 16. Fungi i d e n t i f i e d from basidiocarps on un-treated spruce control poles at Westham Island test s i t e (Cserjesi, 1984). 131 17. Relationship between i s o l a t i o n frequency and core p o s i t i o n for the genera of major fungi isolated from 24 white spruce poles. 132 18. Frequency of i s o l a t i o n of the major fungi i n the p i t h zone from both kerfed and non-kerfed poles. 136 19. Analysis of nitrogen percentage i n ACA-treated white spruce poles. 139 20. Analysis of variance of residual nitrogen i n the ACA-treated white spruce poles, using s p l i t - p l o t design. 140 21. Range tests for nitrogen i n four d i f f e r e n t zones. 140 22. Least squares regression analysis for the nitrogen content and chemical retention i n the f i r s t a n a l y t i c a l zone. 143 23. Moisture contents of the ACA-treated spruce test poles. 153 24. E l e c t r i c a l resistance reading (kP_) with the Shigometer i n ACA-treated spruce poles. 157 25. E l e c t r i c a l resistance readings of poles c l a s s i f i e d to i d e n t i f y those greatest de-f l e c t i o n readings ( i n d i c a t i v e of decay). 161 26. Examples of test measurements obtained from seven suspect spruce poles. 164 X LIST OF FIGURES Figure Page 1. Changes i n annual Canadian imports, exports, payments and receipts of u t i l i t y poles. 19 2. Battery-powered pulsed-current meter, Shigometer Model 7950, and twisted wire probe. 87 3. Cross-sectional view of the pole at the groundline showing the p o s i t i o n of three b i o l o g i c a l cores. 95 4a. Using flamed forceps, sampled core i s inserted i n a s t e r i l i z e d glass tube. 96 4b. Sample cores i n the s t e r i l i z e d glass tubes with cork caps at both ends. 96 5. Sampling of cores for the study of chemical d i s t r i b u t i o n and nitrogen content. 98 6. Storing a piece of the core for moisture measurement. 98 7. Sectioning procedures of a b i o l o g i c a l core, providing four zones for the i s o l a t i o n of fungi. 103 8. Two r e p l i c a t i o n s of two d i f f e r e n t types of media, representing each section of four selected zones. 105 9. Positioning about 3/4 of each piece above the medium surface. 105 10. Histogram of average ACA penetration. 113 11. Ratio of copper to arsenic versus t o t a l retention. 124 12. Mean residual nitrogen content versus zone. 142 Regression l i n e of nitrogen content over chemical retention i n the f i r s t a n a l y t i c a l zone. ACKNOWLEDGEMENTS I am deeply indebted to Dr. R.W. Kennedy, my graduate supervisor, for his valuable assistance i n suggesting the experimental subject and preparing the thesis, as well as for his conscientious and understanding guidance over the past three years at thi s University. I should l i k e to express p a r t i c u l a r gratitude to Drs. J.N.R. Ruddick and R..S. Smith for t h e i r professional assistance i n supervising the experimental phases and for t h e i r valuable advice, c r i t i c i s m and continuing encouragement. Also, I deeply appreciate the guidance of the remaining member of my committee, Dr. van der Kamp. Special thanks are due to Dr. E.C. S e t l i f f for his di r e c t i o n and assistance throughout bioassay work, Ms. J . E. Clark, Ms. W.C. Chung, Ms. J.K. Ingram and Mr. N.A. Ross for providing technical guidance and f a c i l i t i e s for the experimental works, and to Dr. A. Kozak and Mr. J. Emanuel for the s t a t i s t i c a l analysis. I should l i k e to extend my s p e c i a l thanks to Mr. B.E. Dawson-Andoh, my colleague, and Mr. A. Byrne for the benefit derived from many discussions with them at the time of writing t h i s t h e s i s . I would l i k e to express my sincere thanks to Drs. J.W. Wilson and R.M. Kellogg for t h e i r continuous encour-agement through my graduate study. F i n a n c i a l support from the Canadian E l e c t r i c a l Association i s very sincerely acknowledged. F i n a l l y , I am extremely g r a t e f u l to my wife, Sharon, for the excellent typing job and, above a l l , for her warm encouragement, support and endless patience, without which thi s study would not have been possible. 1.0 INTRODUCTION Wood u t i l i t y poles i n transmission and d i s t r i b u t i o n systems represent a large annual c a p i t a l investment. Canadian e l e c t r i c a l and telephone companies have a consid-erable f i n a n c i a l investment i n wooden poles i n service, amounting to an annual rate i n excess of $80 m i l l i o n (Ruddick, 1984b). Every year over $29 m i l l i o n i s invested in B r i t i s h Columbia alone through the i n s t a l l a t i o n of preservative treated wooden poles. Canada has an uneven d i s t r i b u t i o n of coniferous species capable of being used as pole material. In p a r t i c u l a r , the regions between the P a c i f i c Coast and the Rocky Mountains are endowed with several softwoods which produce trees of great q u a l i t y and height. At the same time the i n d u s t r i a l and population pressures on eastern and central Canadian forests have long ago removed almost a l l the best pole material (Sugden, 1979). T r a d i t i o n a l l y , Canada has been a net pole exporter due to i t s vast forest resource. The province of B.C. i s p a r t i c u l a r l y fortunate since i t contains commercial quanti-t i e s of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco), western red cedar (Thuja p l i c a t a Donn) and lodgepole pine (Pinus contorta Dougl.), for the supply of the u t i l i t y poles. 2 Since the early 1970's, however, there has been a number of comments concerning the shortage of these poles. At the 1974 meeting of the Western Forest Products Laboratory's (WFPL) Research Program Committee on Treated Wood Products, i t was revealed that Canada was importing a considerable number of u t i l i t y poles mainly from the U.S.A. and Finland (Dobie, 1976). As a consequence, a study was conducted to analyze the supply-demand s i t u a t i o n , and to i d e n t i f y and understand the various problems plaguing the industry. Possible ways of solving or eliminating some of the problems were suggested. The simple, short-term solution was to import poles from other countries, such as the U.S.A. However, i t became obvious that a more appropriate, long-term solution would be to u t i l i z e some of the other wood species, currently not used for poles i n Canada. Although western red cedar and lodgepole pine are the two wood species most widely used, the B.C. forests also contain large quantities of western hemlock (Tsuga hetero- phylla (Raf.) Sarg.), amabilis f i r (Abies amabilis (Doug.) Forbes) and white spruce (Picea glauca (Moench) Voss). In 1974, the WFPL proposed to the Research Program Committee on Wood Preservation a study to determine the strength and t r e a t a b i l i t y of three a l t e r n a t i v e pole species available i n B.C. Among these species, there was considerable interest 3 i n the p o t e n t i a l of spruce for s a t i s f y i n g some of the future demand. Spruce i s p a r t i c u l a r l y a t t r a c t i v e because i t i s available i n r e l a t i v e l y large quantities and the pole produced from t h i s species would meet the requirements of the pole classes i n greatest demand. In 1977, sixty-two white spruce pole sections were i n s t a l l e d at the WFPL's Westham Island test f i e l d s i t e near Vancouver. They had been commercially incised and pressure-impregnated with ammoniacal copper arsenate (ACA) or penta-chlorophenol (PCP) i n o i l . As a consequence of the treating conditions used for the poles, those treated with ACA were well penetrated but the preservative retentions were low, whereas the PCP-treated poles had poor penetration but a high chemical content i n the treated zone (Ruddick, 1978). This material therefore provides an unique opportunity to investigate the influence of the parameters of preservative penetration and retention on the long-term d u r a b i l i t y of spruce poles. This present study investigated only the ACA-treated poles. Since i t was intended that a number of the spruce pole sections would be i n s t a l l e d i n a graveyard test to evaluate t h e i r service l i f e , one additional factor, kerfing, was included i n the design of the o r i g i n a l study i n 1977. Twenty-two of the forty-one spruce poles to be l a t e r i n s t a l l e d at Westham Island test f i e l d s i t e were therefore f u l l -length kerfed 0.32 i n . (0.81 cm) i n width extending to the p i t h of poles, to minimize the formation of deep checks i n service and treated with ACA using the Lowry empty-cell process. I n s t a l l a t i o n of representative samples of a l l treatments in the graveyard test permitted monitoring of fungal colonization, decay, preservative leaching and check* ing c h a r a c t e r i s t i c s of the ACA-treated pole sections. Four main objectives have been i d e n t i f i e d for t h i s study: a) To determine the ACA preservative penetration and retention of the poles i n test and report on the preservative d i s t r i b u t i o n and possible leaching of ACA; b) To determine whether decay fungi have become es-tablished i n the treated and untreated wood; c) To confirm or deny previous observations of enhanced nitrogen levels in the untreated core of commodities treated with ACA preservative; d) To evaluate the usefulness of a Shigometer for the detection of decay i n poles, by comparing Shigometer data with the results obtained from fungal i s o l a t i o n studies. Such information i s required to e s t a b l i s h the v i a b i l i t y of ACA-treated spruce as pole material i n Canada. 1.1 CHEMICAL DISTRIBUTION STUDY Preservative systems must perform t h e i r functions throughout the service l i f e of the product under a v a r i e t y of exposure conditions. Thus, wooden poles must be preserv-ative-treated to protect both the above- and below-ground portions for several decades, i n a v a r i e t y of climates and s o i l s . Because of the r e l a t i v e l y high cost of organic solvents, much work has been directed to developing water-soluble rather than o i l - s o l u b l e formulations (e.g. PCP) for protection of poles. ACA i s one waterborne preservative that has become well established for treatment of poles during the past 2 0 years. This formulation contains, as active ingredients, equal amounts of copper and arsenic, expressed as CuO and A S 2 O 5 . In ACA, the ammonia i n the solvent reacts with the copper arsenate to form a soluble complex which, although stable i n ammonium hydroxide solution, r e a d i l y breaks down to form an insoluble copper arsenate when the solvent i s removed. Inorganic s a l t s of copper-arsenic-zinc dissolved in ammonium hydroxide have been formulated and tested i n wood for t o x i c i t y to fungi, water repellency (Rak, 1975), glowing combustion resistance, and leach resistance (Rak 6 and Clarice, 1974) . In recent studies (Krzyzewski, 1978a? Rak, 1977a; Ruddick, 1978) , the outstanding penetration of ammoniacal preservative solutions into spruce roundwood has been shown. The f i x a t i o n of ammoniacal copper compounds depends on the v o l a t i l i z a t i o n of ammonia and the i n s o l u b i l i z a t i o n of the preservative. Copper arsenate-treated wood has proven to be one of the most durable of the preservative treatments used today. It i s r e l a t i v e l y non-leachable and the preservative i s highly e f f e c t i v e . The objective of t h i s part of the study was to deter-mine the preservative penetration and retention of the poles i n test for several years and to compare these results with i n i t i a l values obtained i n 1977 p r i o r to graveyard i n s t a l l a -t i o n . 1.2 BIOLOGICAL STUDY The service l i f e of wood poles can be d r a s t i c a l l y reduced by decay, insect attack, and even automobile c o l l i s i o n s . The most serious of these i s undoubtedly decay. During recent pole shortages, several wood-treating companies examined the s u i t a b i l i t y of spruce as a pole material. In various experiments conducted on spruce, however, i t has been reported that p o t e n t i a l problems existed due to 7 excessive checking and d i f f i c u l t y i n obtaining an adequate treatment. It i s also known that spruce wood i s very low in natural decay resistance, and as such must be preservative-treated for applications involving ground contact. In u t i l i t y poles fungal attack i s favoured i n the surface layers just above and below the groundline, and also i n the core of these regions. Both of these locations are c r i t i c a l with respect to the serviceable l i f e of the pole, since i t s strength i s dependent on i t s c a n t i l e v e r beam configuration, where the maximum moment i s developed about the groundline. The i d e n t i t y and the e f f e c t s on microorganisms colonizing wood have been the subject of many major investigations. Information on the i d e n t i t i e s , frequencies, and the role of the major fungi associated with degradation i n u t i l i t y poles i s e s s e n t i a l for control programs. An understanding of the successional relationships among microorganisms i n the i n i -t i a t i o n and development of wood decay, and t h e i r e f f e c t s on preservative s t a b i l i t y and pole strength i s required to devise the best protection s t r a t e g i e s . This portion of the study was designed to obtain the id e n t i t y , frequency, and role of the major fungi involved i n degradation i n the ACA-treated white spruce poles a f t e r several years i n f i e l d t e s t i n g . 8 1.3 NITROGEN ENHANCEMENT STUDY Wood-degrading microorganisms have the same basic growth requirements as do the green plants. These include a source of food, an adequate supply of water, favourable temperature, oxygen, and a suitable pH. Optimal n u t r i t i o n a l needs of wood-damaging microorganisms vary, but a l l species obviously can e x i s t on what i s available in wood i t s e l f . Energy and most of the c e l l - b u i l d i n g materials for microorganisms are supplied mainly by the carbohydrate f r a c t i o n consisting of holocellulose, starches, and sugars, and for some organisms, by the l i g n i n f r a c t i o n . Nitrogen and minerals are available, though i n comparatively small amounts. A trace amount of thiamin, the vitamin B l of animal n u t r i t i o n , apparently i s needed by most decay fungi. Cellulose, hemicellulose and l i g n i n comprise more than 90 percent of the dry weight of most woods, so are s u f f i -c i e n t l y abundant to meet the requirements of microorganisms u t i l i z i n g them. However, nitrogen i s extremely sparse, being present i n amounts no greater than about 0.03 to 0.10 percent (Cowling, 1970). Nevertheless, these quantities are adequate for rapid decay of wood, in d i c a t i n g unique n i t r o g e n - u t i l i z i n g e f f i c i e n c y by the attacking fungi. I t has been suggested by Cowling that t h i s e f f i c i e n c y may derive i n part from an a b i l -i t y of the fungi to s o l u b i l i z e the nitrogen i n the protoplasm 9 of t h e i r older hyphae and transport i t to new zones of attack, where i t supplements the nitrogen e x i s t i n g i n the zones. Several researchers (Cowling, 1970; Cowling and M e r r i l l , 1965; Findlay, 1934; M e r r i l l and Cowling, 1965 and 1966) have shown that increasing the nitrogen content of wood frequently increases the rate of decay by wood-inhabiting fungi. Moder-ately greater rates of decay have been observed to be corre-lated with greater amounts of natural nitrogen, but there i s s t i l l c o n f l i c t i n g evidence as to whether decay can be increased appreciably by a r t i f i c i a l l y adding nitrogen to wood (Cowling, 1970). I t i s generally assumed that, during the f i x a t i o n of the ammonia-based wood preservative, such as ACA, the ammonia i s l o s t from the wood. However, i t has previously been reported by Ruddick (1979) that the treatment of wood with ammoniacal type preservatives results i n c e r t a i n enhancement of the nitrogen content i n the untreated core. Therefore, the question of whether the loss of ammonia from ACA-treated wood i s complete could well prove to be important, p a r t i c u -l a r l y i n spruce when inadequate treatment combined with the easy formation of deep checks i s encountered. Comparison of the ACA- and non-ACA-treated spruce woods would allow conclusions to be made on possible nitrogen enhancement. Thus the objective of th i s part of the study 10 was to measure the residual nitrogen l e v e l i n wood treated with ACA and to determine also to what extent, i f any, the nitrogen l e v e l i n wood was enhanced by the treatment. Any possible nitrogen enhancement was correlated with the presence of fungi inhabiting the wood. 1.4 SHIGOMETER STUDY Early recognition of an attack and the degree of any wood deterioration are important to the pole producers to minimize possible losses. Unfortunately, b i o l o g i c a l attack i s not r e a d i l y i d e n t i f i e d i n the i n i t i a l stages. S u p e r f i c i a l mycelium and fungal f r u i t bodies are only produced a f t e r fungi have become well established. Some of the key elements i n a long-term decay control program for u t i l i t i e s are proper pole s p e c i f i c a t i o n s , c a r e f u l pole s e l e c t i o n and handling, e f f e c t i v e preservative treatment, r e l i a b l e inspections, and pole maintenance programs involving a n c i l l a r y preservative treatment. However, the r e l i a b l e detection of early decay i n poles followed by e f f e c t i v e eco-nomical remedial treatment has been of p a r t i c u l a r importance. Existi n g methods for i n t e r n a l decay detection, such as boring, sounding, sonic detectors, and X-rays, are either i n s e n s i t i v e to i n c i p i e n t decay attack or unreliable. Recently, the Shigometer has been proposed for detection of decay i n 11 l i v i n g hardwood trees. The Shigometer i s a resistance meter, which measures changes i n the condition of the wood associated with changes i n e l e c t r i c a l resistance. A pulsed d i r e c t current, passing through wood i n progressive stages of decay, meets with decreasing resistance. Such changes caused by fungal attack are, for example, s p e c i f i c gravity, pH, moisture and the concentration of cations (Brudermann, 1977). Despite considerable research conducted on wood u t i l i t y poles, there i s no c l e a r i n d i c a t i o n of the value of the Shigometer i n detecting early decay i n poles under f i e l d conditions. The objective of th i s f i n a l segment of the study was to determine whether a Shigometer could be used for detec-t i o n of early decay i n poles having been i n f i e l d test for several years. Shigometer readings were, therefore, taken in wood adjacent to the locations sampled for the fungal studies, and the results interpreted i n terms of presence or absence of active decay fungi. 12 2.0 LITERATURE REVIEW 2.1 SUPPLY AND DEMAND FOR UTILITY POLES IN CANADA Since the building of the nation's railway and the i n -vention of the telegraph, wood u t i l i t y poles have been widely used i n Canada. With the growing population and industry, the demand for e l e c t r i f i c a t i o n spread through urban and r u r a l areas across the nation. During the period between the late 1950s and the early 1970s, there was a s i g n i f i c a n t increase i n the e l e c t r i c a l d i s t r i b u t i o n f a c i l i t i e s , p a r t i c u l a r l y i n the P r a i r i e provinces of Alberta, Saskatchewan and Manitoba. For example, actual purchases of these provinces increased approximately 15% a year from 1970 when 50,800 poles were procured to 1973 when 77,600 poles were obtained (Karaim, 1975). With r i s i n g disposable incomes and more automobiles purchased, there have been pressures to improve road trans-portation networks, often necessitating relocation of e x i s t -ing pole l i n e s . The requirement for pole replacement, at the rate of anywhere from 0.5 to 2.5% depending on the u t i l i t y reporting (Sugden, 1979), has also been an important factor a f f e c t i n g a constant demand for new poles. There have been some counteracting e f f e c t s on the demand for wooden poles due to aesthetic reason, development of new technology such as microwave systems i n telegraph pole l i n e , and encroachment into the market by concrete and s t e e l poles (Karaim, 1975; Sugden, 1979). Nevertheless, such types of natural, economic and environmental factors have maintained a steady pressure on the e l e c t r i c a l , telephone and telegraph u t i l i t y companies and, by extension, on the suppliers of wooden poles. Thus, natural wooden poles have been a unique product of Canada's forests, since they have been e f f e c t i v e l y used i n the form in which they grew. H i s t o r i c a l l y , the u t i l i t y pole industry i n Canada was established around western red cedar mainly due to i t s natural decay resistance, straightness, length and l i g h t weight, comparatively thin sapwood, s u i t a b i l i t y of climbing and f i n a l l y i t s abundance r e l a t i v e to demand. Even without treatment, an average western red cedar pole l i f e somewhat less than 20 years can be expected (USDA, 1974). Since the early 1970s, the requirements for u t i l i t y poles have been gradually increasing across Canada. However, because B.C. contains h a l f of the nation's t o t a l softwood growing stock (Table 1), and a l l i t s western red cedar, the province t r a d i t i o n a l l y has been a net pole exporter, as well as a steady supplier to the rest of the country. The trend i n u t i l i t y pole exports from B.C. for the period 1963 to 1978 i s shown i n Table 2. One s i g n i f i c a n t feature of the data i s that exports of poles from B.C. since TABLE 1. Forest resources comparison (B.C. Ministry of Forests, 1979). Softwood Hardwood Total Growing Growing Growing Forest Region Forest Land Stock Stock Stock (million ha.) (million m ) (mi l l i o n m ) (mi l l i o n m^ ) B r i t i s h Columbia(1) 52.1 7,871 211 8,082 Canada(2) 342.0 15,202 4,079 19,281 World(3) 2,795.0 107,000 180,000 287,000 O r i g i n a l sources: (1) B r i t i s h Columbia Ministry of Forests, Inventory S t a t i s t i c s , 1978 (2) Canadian Forestry Service, Canada's Forests, 1978 (3) FAQ, World Pulp and Paper Demand, Supply and Trade, 1977; Royal College of Forestry, Stockholm, Sweden, World Forest Resources, 1974 Note: The qu a l i t y of forest land and growing stock s t a t i s t i c s i s not uniform amongst regions of the world due to the use of d i f f e r e n t d e f i n i t i o n s and measurements standards. TABLE 2. Trend i n u t i l i t y pole exports from B.C. (Sugden, 1979). Total Quantity Exported (Lineal Feet) To other To To other Year Provinces U.S.A. Countries Total 1963 3,894,070 7,797,268 1,014,324 12,705,662 1964 2,909,059 6,566,569 677,201 10,172,829 1965 5,958,518 3,750,672 473,529 10,182,719 1966 3,358,961 8,026,637 1,005,065 12,390,663 1967 2,252,050 6,496,834 3,128,154 11,877,038 1968 1,271,184 5,917,141 4,281,641 11,469,966 1969 815,305 4,700,716 2,088,801, 7,604,822 1970 1,407,227 6,059,181 1,583,584 9,049,992 1971 2,073,375 3,699,385 271,502 6,044,262 1972 2,069,189 4,183,636 213,192 6,466,017 1973 2,693,753 2,205,397 638,317 5,537,467 1974 3,912,525 3,483,773 49,784 7,446,082 1975 2,027,878 1,574,975 522,624 4,125,477 1976 1,788,082 1,602,261 67,600 3,457,943 1977 1,018,076 2,352,849 80,225 3,451,150 1978 2,865,669 3,132,550 1,800 6,000,019 Or i g i n a l source: B.C. Min i s t r y of Forests, Annual Reports Note: 1. Due to the use of d i f f e r e n t measurement units, i . e . pieces and l i n e a l feet, and no categori-zation between poles and p i l e s i n some B.C. forest d i s t r i c t s , the above data u n t i l 1976 do not coincide with those available i n other l i t e r a t u r e sources such as B.C. Annual Reports and Dobie (1976). 2. Further data a f t e r 1978 are omitted because of t h e i r u n a v a i l a b i l i t y . 1971 were seldom more than h a l f of those from 1963 to 1968. But log production i n B.C. increased from 16.02 m i l l i o n cunits i n 1966 to 24.77 m i l l i o n i n 1973, and western red cedar output jumped from 2.09 to 3.10 m i l l i o n cunits (Dobie, 1976). Thus the probable s i t u a t i o n , as Dobie (1976) points out, was one of a diminishing portion of the harvest being u t i l i z e d as pole stock. At the same time, demand for B.C. poles from the rest of the country increased s u b s t a n t i a l l y since 1969, consequently putting pressure on the available supply. As indicated above, the u t i l i t y pole market which had been t r a d i t i o n a l l y stable changed markedly i n the early 1970s. As a r e s u l t , Canada became a net pole importer for the f i r s t time i n 1974. The trends i n t o t a l annual Canadian imports and exports of u t i l i t y poles for the period 1963 to 1983 are presented i n Table 3, and are shown graphically i n Figure 1. The most s t r i k i n g feature about the figure i s that considerable fluctuations i n pole imports were apparent, p a r t i c u l a r l y for several years since 1973. On the other hand, i t leaves no doubt that the trend i n exports has been s t e a d i l y downward. It i s c l e a r l y noted that there was a f a i r l y dramat-i c increase i n imports i n 1973, so that net pole imports were about 4.4 m i l l i o n l i n . f t . i n 1974. This had an adverse e f f e c t on the balance of payments for poles, which i n 1974 T A B L E 3 . T r e n d i n t o t a l a n n u a l C a n a d i a n i m p o r t s , e x p o r t s , p a y m e n t s a n d r e c e i p t s o f u t i l i t y p o l e s . E x p o r t s I m p o r t s Y e a r V a l u e T o t a l Q u a n t i t y ( T o U . S . A . ) V a l u e T o t a l Q u a n t i t y ( F r o m U . S . A . ) i n 1 0 0 0 o f $ i n L i n . F t . i n 1 0 0 0 o f $ i n L i n . F t . 1 9 6 3 5 , 3 7 7 8 , 1 2 6 , 3 2 7 ( 8 , 0 8 8 , 7 0 5 ) 1 9 6 4 4 , 8 6 6 6 , 9 3 5 , 3 1 8 ( 6 , 9 1 0 , 4 1 1 ) 4 5 9 1 , 1 7 6 , 1 8 0 ( 1 , 1 7 6 , 1 8 0 ) 1 9 6 5 5 , 0 2 5 6 , 7 3 3 , 7 6 4 ( 6 , 6 8 7 , 9 3 0 ) 1 , 3 9 8 2 , 1 2 9 , 1 1 1 [ 2 , 1 2 9 . 1 1 1 ) 1 9 6 6 5 , 5 3 8 6 , 8 9 5 , 3 0 9 ( 6 , 8 9 0 . 6 5 6 ) 1 , 6 1 6 3 , 0 4 9 , 9 3 2 [ 3 , 0 4 9 , 9 3 2 ) 1 9 6 7 5 , 3 2 4 6 , 0 9 2 , 9 4 3 ( 5 , 9 7 9 , 8 3 3 ) 7 9 1 1 , 3 8 8 , 6 8 3 [ 1 . 3 8 8 . 6 8 3 ) 1 9 6 8 6 , 4 3 5 7 , 5 2 0 , 4 4 9 ( 7 . 3 4 1 . 0 5 6 ) 5 0 4 4 9 2 , 4 6 5 [ 4 9 2 , 4 6 5 ) 1 9 6 9 6 , 2 8 1 5 , 8 9 7 , 5 0 1 ( 5 , 7 9 1 , 2 1 9 ) 3 9 9 3 5 4 , 7 7 8 [ 3 5 4 , 7 7 8 ) 1 9 7 0 6 , 3 8 4 6 , 3 5 7 , 9 9 4 ( 5 , 9 2 8 . 9 1 8 ) 9 3 2 6 6 4 , 8 4 6 [ 6 6 4 , 8 4 6 ) 1 9 7 1 5 , 7 0 7 5 , 6 3 2 , 9 8 0 ( 5 , 2 0 4 , 4 3 9 ) 8 1 1 6 2 0 , 9 9 4 ( 6 2 0 , 9 9 4 ) 1 9 7 2 6 , 0 4 0 5 , 2 1 7 , 0 1 6 ( 5 , 1 8 0 , 0 8 1 ) 9 0 0 1 , 0 0 7 , 1 8 7 ( 1 , 0 0 7 , 1 8 7 ) 1 9 7 3 5 , 8 9 2 4 , 8 8 6 , 5 5 4 [ 4 , 8 0 3 . 2 8 7 ) 3 , 6 2 9 3 , 8 7 4 , 7 1 6 ( 3 , 4 2 2 , 7 1 6 ) 1 9 7 4 7 . 2 3 0 5 , 1 0 2 , 7 3 2 ( 4 , 2 8 1 , 2 7 4 ) 1 2 , 1 0 5 9 , 4 7 5 , 2 6 9 ( 8 , 8 3 1 , 6 7 4 ) 1 9 7 5 7 , 6 4 4 4 , 2 6 9 , 4 3 5 ( 2 , 7 6 8 . 0 7 9 ) 1 1 , 9 8 0 7 , 8 1 8 , 4 3 7 ( 7 , 4 1 5 , 8 3 7 ) 1 9 7 6 9 , 2 6 2 5 , 2 2 3 , 4 5 0 ( 2 , 2 8 8 , 7 1 8 ) 4 , 0 3 0 2 , 0 2 9 , 8 8 0 ( 1 , 5 6 1 , 3 7 3 ) 1 9 7 7 6 , 8 5 9 3 , 5 6 4 . 0 4 2 ( 2 , 8 9 2 , 8 6 7 ) 3 , 0 3 1 1 , 5 0 5 , 5 3 6 ( 1 , 5 0 3 , 5 3 6 ) 1 9 7 8 7 , 6 1 8 3 , 3 1 1 , 4 5 2 ( 2 , 6 7 3 , 6 3 6 ) 8 , 0 7 6 4 , 4 7 8 , 6 5 9 ( 3 , 1 6 6 , 6 8 9 ) 1 9 7 9 7 , 8 0 2 2 , 8 1 3 . 1 7 3 ( 2 , 5 7 0 , 8 4 0 ) 1 0 , 4 5 9 3 , 5 9 3 , 1 1 9 ( 3 , 2 0 5 , 0 5 9 ) 1 9 8 0 8 , 5 8 7 2 , 8 6 3 , 5 1 0 ( 2 , 7 6 9 . 4 1 4 ) 1 0 , 5 3 0 3 , 6 1 4 , 1 2 4 ( 3 , 1 1 0 , 2 7 7 ) T A B L E 3 . ( c o n t . ) E x p o r t s I m p o r t s Y e a r V a l u e T o t a l Q u a n t i t y ( T o U . S . A . ) i n 1 0 0 0 o f $ i n L i n . F t . V a l u e i n 1 0 0 0 o f $ T o t a l Q u a n t i t y ( F r o m U . S . A . ) i n L i n . F t . 1 9 8 1 1 9 8 2 1 9 8 3 8 , 9 9 0 1 0 , 8 5 3 1 3 , 8 7 6 3 , 1 3 5 , 8 8 0 ( 2 , 7 1 9 , 1 3 7 ) 2 , 6 3 2 , 9 5 0 ( 1 , 7 0 1 , 7 6 2 ) 3 , 1 2 2 . 0 4 7 ( 2 , 6 3 4 , 0 6 5 ) 6 , 6 6 8 7 , 0 3 2 2 , 6 2 9 2 , 1 9 2 , 3 8 3 ( 1 , 8 3 9 , 4 7 1 ) 2 , 1 0 2 , 4 1 0 ( 1 . 7 2 9 , 6 4 6 ) 8 2 5 , 0 8 5 ( 8 2 5 , 0 8 5 ) S o u r c e s S t a t i s t i c s C a n a d a C a t a l o g u e s 6 5 - 2 0 2 , 6 5 - 2 0 3 -10-H r-8-LU LU LU < LU L-6-U. O 0) z o -4--2-A • IMPORTS EXPORTS — \ -15-(0 oc < o M 0 1 z h5-• PAYMENTS RECEIPTS / ^ > ' \ -o- — i ' " " i 1963 '64 -1— '66 _ 1 _ I '69 _L_ -1 1 '72 '73 _ l L_ ~i r~ '74 '76 r -'76 — T — '77 —r— '81 _ l _ '66 I '67 _ L _ '68 _L_ '70 '71 '78 _ L _ i '79 _L_ '80 _ L _ '82 '83 Figure 1. Changes in annual Canadian imports, exports, payments and receipts of utility poles. 20 was a d e f i c i t of $4.9 m i l l i o n compared with a surplus of $2.3 m i l l i o n i n the p r i o r year. The p r i n c i p a l reason that Canada became a net importer of poles during the years 1974 and 1975 and again i n 1978 -1980 i s that, as noted previously, very high lumber prices resulted i n the diversion of some pole stock to sawmills, thus creating a reduction i n pole inventories. Another reason was the sudden increase i n demand i n conjunction with an extremely low supply s i t u a t i o n . I t should also be noted that t h i s change was a res u l t of heavy forward buying i n 1973 for the following years. Further detailed discussion and analysis are available elsewhere (Dobie, 1976; Karaim, 1975; Sugden, 1979). As most pole suppliers anticipated, Canada returned shortly to i t s former p o s i t i o n as a net pole exporter. Due to a dramatic increase in pole imports from the U.S.A. (Table 3), however, this p o s i t i o n was reversed again for the short period between 1978 and 1980. The large proportion of imports was southern yellow pine from southern U.S. destined for c e n t r a l and eastern Canada. As Dobie (1976) indicated, t h i s trend appeared to be mainly because of price advantage and equivalent freight costs for poles from Alabama to southern Ontario compared with those from B.C. In s p i t e of the major fl u c t u a t i o n that occurred from the early 1970s u n t i l 1980, 21 i t i s c l e a r l y shown that the trade trend for poles i n recent years has been f a i r l y stable, with the increased surplus of receipts commencing i n 1981 and p e r s i s t i n g to the present. In a recent study conducted by Sugden (1979), the future demand and supply of wooden u t i l i t y poles i n Canada has been extensively analysed on the basis of calculated pole usage rates and estimated p r o v i n c i a l populations. Without consid-ering the eventuality of imports of poles from foreign coun-t r i e s , what his analyses have shown i s that projected demands for wooden u t i l i t y poles to the year 2000 i s s u f f i c i e n t to be met by projected domestic supplies. Since the early 1970s, as noted, there has been the danger that southern yellow pine suppliers could maintain or enlarge t h e i r proportion of the pole market. Regardless of the Canadian supply s i t u a t i o n , there w i l l always be a l i k e l i h o o d of poles being imported. Therefore, Canada should compete successfully i n p r i c e to continue to be a net pole exporter, as well as to s a t i s f y i t s domestic demands. But i n order to avoid the necessity of having to import to ac-commodate increased pole requirements, as Dobie (1976) points out, an obvious need exists for closer l i a i s o n between buyer and s e l l e r regarding future supply. There are also needs for a greater lead-time allowance on the part of pole buyers, and for manufacturers to check comparative pole and lumber 22 values c a r e f u l l y before consigning pole stock to a sawmill. In agreement with the l i t e r a t u r e (Dobie, 1976; Karaim, 1975; Ruddick, 1978; Sugden, 1979), i t i s believed that a more appropriate, long-term sol u t i o n would be to u t i l i z e some of the l i t t l e - u s e d pole species available i n Canada. Therefore, an urgent need exists for research data on the s a t i s f a c t o r y treatment of non-traditional species such as white spruce for use as u t i l i t y poles, with the objective of making pole supply more e l a s t i c . 2.2 WHITE SPRUCE AS POTENTIAL POLE SPECIES White spruce, a c h a r a c t e r i s t i c tree of the boreal forest region, can be found almost everywhere i n Canada, making up approximately 40% of the coniferous volume and one-third of the t o t a l volume of a l l species grown i n t h i s country (Sudgen, 1979). Even i n B.C. where the number of conifers are found, a number of species of spruce again predominates, consisting of 25% of the mature volume i n the province. This species i s widely used for reforestation and planting, and i t s pole-sized timber i s abundant i n large q u a n t i t i e s . On the average (Hosie, 1975; Isenberg, 1980), white spruce i s 80 f t . (24 m) t a l l and 24 i n . (61 cm) i n diameter, but some trees a t t a i n heights of 120 f t . (36 m) with a diameter of up to 48 i n . (122 cm). 23 The wood i s lustrous, nearly white to pale brown coloured with an i n d i s t i n c t heartwood, i s usually s t r a i g h t grained, l i g h t to moderately l i g h t (e.g. a l i t t l e denser than western red cedar), and very uniform i n appearance. 2.2.1 CHEMICAL, PHYSICAL AND MECHANICAL PROPERTIES OF WHITE SPRUCE The chemical properties of coniferous woods are s u r p r i s -ingly s i m i l a r with only minor variations occurring among species. Wood of a l l species i s chemically composed of holo-c e l l u l o s e (alpha c e l l u l o s e and hemicellulose), l i g n i n , ash and extractives. The proximate values for the chemical com-posi t i o n of white spruce wood are shown i n Table 4. For sake of comparison, the table also includes several coniferous woods which are e i t h e r dominant or p o t e n t i a l species f o r pole production i n Canada. Of the chemical properties of c o n i f -erous woods, extractive content i s probably the only variable of consequence, and as Panshin and De Zeeuw (1970) point out, the extractives generally constitute a few percent of the oven-dry weight of wood. The heartwood of white spruce contains acetone- and petroleum ether-soluble extractives (Rogers et a l . , 1969), and Swan (1973) reported information on f a t t y acids and r e s i n acids. For the percent composition of heartwood extractives are available elsewhere (Drew and Pylant, 1966). However, the extractives, such as t h u j a p l i c i n s T A B L E 4 . C h e m i c a l c o m p o s i t i o n o f s i x c o m m o n c o n i f e r o u s w o o d s ( I s e n b e r g , 1 9 8 0 ) S o l u b i l i t y i n A l p h a - H e m i - T o t a l A l c o h o l H o t S p e c i e s c e l l u l o s e c e l l u l o s e L i g n i n p e n t o s a n A s h b e n z e n e w a t e r (%) (%) (%) (%) (%) i%) (%) W h i t e s p r u c e ( P i c e a q l a u c a ) 4 2 . 6 1 6 . 4 2 9 . 4 1 1 . 8 0 . 3 2 . 0 2 . 6 A m a b i l i s f i r ( A b i e s a m a b i l i s ) 4 3 . 8 - 2 8 . 2 9 . 8 0 . 5 2 . 6 3 . 2 D o u a l a s - f i r ( P s e u d o t s u q a m e n z i e s i i ) 4 9 . 6 1 4 . 1 2 7 . 7 7 . 9 0 . 2 4 ; i 5 . 0 L o d q e p o l e p i n e ( P i n u s c o n t o r t a ) 4 5 . 7 - 2 7 . 2 1 2 . 4 0 . 2 3 . 5 2 . 7 W e s t e r n h e m l o c k ( T s u g a h e t e r o p h y l l a ) 4 9 . 2 1 5 . 5 2 9 . 4 9 . 2 0 . 3 2 . 6 2 . 0 W e s t e r n r e d c e d a r ( T h u i a p l i c a t a ) 4 4 . 0 1 4 . 6 3 0 . 9 9 . 0 0 . 3 1 4 . 1 1 1 . 0 N o t e : A l l p e r c e n t a g e s b a s e d o n m o i s t u r e - f r e e w o o d . to 4* 25 responsible for the natural decays resistance of western red cedar (Kurth, 1950; Rennerfelt, 1948), are not present i n spruce wood. The physical properties of wood normally include spe-c i f i c gravity, shrinkage, anatomy. These properties c l o s e l y r e l a t e to the mechanical strength properties of the wood and to i t s a b i l i t y to be impregnated by preservative solutions. To i l l u s t r a t e the physical properties of white spruce, Table 5 has been prepared to include white spruce and the f i v e other species l i s t e d i n Table 4. Of these species presented, there i s a l i t t l e difference i n most of the physical proper-t i e s examined, though Douglas-fir has a s i g n i f i c a n t l y higher s p e c i f i c gravity value. It could be argued that the presence of r e s i n canals i s b e n e f i c i a l for the d i s t r i b u t i o n of preserv-ative solutions both i n the transverse and r a d i a l d i r e c t i o n s . Attributes such as tracheid diameter and ray volume would influence the ease of penetration both i n v e r t i c a l and l a t e r a l d i r e c t i o n s . Thus the small average tracheid diameter with the presence of blocked bordered p i t s of white spruce may account for some of the d i f f i c u l t i e s i n preservative t r e a t -ment reported for t h i s species. The process of heartwood formation or drying causes the p i t membrane to s h i f t thereby blocking the p i t aperture by the torus (Stamm, 1970). This s i t u a t i o n , which i s well known i n the i n t e r i o r v a r i e t y of T A B L E 5 . P h y s i c a l p r o p e r t i e s o f s i x c o m m o n c o n i f e r o u s w o o d s . S p e c i f i c G r a v i t y T r a c h e i d D i m e n s i o n s S h r i n k a g e A v e . R a y R e s i n R i n g L a t e -S p e c i e s G r e e n O v e n - d r y V o l u m e ^ L e n g t h D i a m e t e r C a n a l s 2 G r e e n t o O v e n - d r y ( % ) W i d t h w o o d V o l u m e V o l u m e ( * ) (mm) O n ) ( n o r m a l ) (mm) (%) T a n g e n - V o l u -R a d i a l t i a l m e t r i c W h i t e 0 . 3 7 0 . 4 2 7 . 0 3 . 3 3 5 p r e s e n t 4 . 7 8 . 2 1 3 . 7 1 . 7 2 1 s p r u c e A m a b i l i s 6 . 3 5 6 . 4 2 7 . 0 3 . 3 6 0 a b s e n t 4 . 6 9 . 8 1 3 . 8 1 . 7 2 2 f i r D o u g l a s - 0 . 4 5 0 . 5 1 7 . 3 3 . 4 5 5 p r e s e n t 5 . 0 7 . 8 1 1 . 8 1 . 7 3 5 f i r L o d g e p o l e 0 . 3 8 0 . 4 3 5 . 7 3 . 2 5 5 p r e s e n t 4 . 5 6 . 7 1 1 . 5 1 . 0 2 3 p i n e W e s t e r n 0 . 3 8 0 . 4 4 8 . 0 3 . 0 5 0 a b s e n t 4 . 3 7 . 9 1 1 . 9 1 . 3 3 1 h e m l o c k W e s t e r n 0 . 3 1 0 . 3 4 6 . 9 3 . 1 4 5 a b s e n t 2 . 4 5 . 0 6 . 8 1 . 7 2 7 r e d c e d a r S o u r c e s t 1 . I s e n b e r g ( 1 9 8 0 ) 2 . P a n s h i n a n d D e Z e e u w ( 1 9 7 0 ) 3 . J e s s o m e ( 1 9 7 7 ) Douglas-fir, also occurs i n white spruce (Sebastian et a l . , 1965). The mechanical properties of wood obtained from small c l e a r specimens are extremely useful i n determining the r e l a t i v e strength between species. These properties are dependent on a number of factors* such as the moisture con-tent and physical properties of the wood, which may vary among species and even within the same species. Table 6 summarizes the mechanical properties of the s i x species i n both green and ai r - d r y conditions. On the basis of the green data given i n the table, these species could be ranked i n order of increasing f i b r e stress at proportional l i m i t i n s t a t i c bending as follows: white spruce, lodgepole pine, amabilis f i r , western red cedar, western hemlock and Douglas-f i r . Although the results of mechanical tests made on small c l e a r specimens can be used to select wood species for a given end-use, i t should be noted that i n very few cases i s the end-use s a t i s f i e d exactly by such specimens. Wooden u t i l i t y poles are normally tested for several purposes, i n accordance with established test procedures such as those published by the American Society for Testing and Materials (ASTM) i n t h e i r standard: ASTM D 1036-83 Standard Methods of S t a t i c Tests of Wood Poles (ASTM, 1984). The strength T A B L E 6 . M e c h a n i c a l p r o p e r t i e s o f s i x c o m m o n c o n i f e r s ( J e s s o m e , 1 9 7 7 ) . S p e c i e s A t t r i b u t e T e s t W h i t e A m a b i l i s D o u g l a s - L o d g e p o l e W e s t e r n W e s t e r n s p r u c e f i r f i r p i n e h e m l o c k r e d c e d a r S t a t i c B e n d i n g S t r e s s a t P r o p o r t i o n a l 2 . 7 8 0 2 , 9 9 0 4 , 3 2 0 2 , 9 7 0 4 , 1 1 0 3 . 1 0 0 L i m i t ( p s i ) 5 . 3 2 0 5 , 8 1 0 7 , 7 4 0 7 , 0 5 0 7 , 8 0 0 4 . 9 9 0 M o d u l u s o f R u p t u r e 5 . 1 0 0 5 , 4 8 0 7 , 5 0 0 5 , 6 5 0 6 , 9 6 0 5 , 3 0 0 ( p s i ) 9 , 0 9 0 9 , 9 9 0 1 2 , 8 5 0 1 1 , 0 2 0 1 1 , 7 6 0 7 . 8 0 0 M o d u l u s o f E l a s t i c i t y 1 , 1 5 0 1 , 3 5 0 1 , 6 1 0 1 , 2 7 0 1 , 4 8 0 1 , 0 5 0 ( 1 0 0 0 p s i ) 1 , 4 4 0 1 , 6 5 0 1 , 9 6 0 1 , 5 8 0 1 , 7 9 0 1 . 2 0 0 I m p a c t B e n d i n g S t r e s s a t P r o p o r t i o n a l 8 , 3 5 0 8 , 6 8 0 1 0 , 3 6 0 7 , 7 6 0 9 , 0 0 0 7 . 5 8 0 L i m i t ( p s i ) 1 0 , 9 2 0 1 2 , 0 0 0 1 4 , 3 4 0 1 0 , 7 8 0 1 1 , 2 0 0 9 , 7 0 0 M o d u l u s o f E l a s t i c i t y 1 , 3 7 0 1 . 6 1 0 2 , 0 0 0 1 , 3 7 0 1 , 9 7 0 1 , 3 8 0 ( 1 0 0 0 p s i ) 2 , 0 0 0 2 , 2 6 0 2 , 8 1 0 1 , 8 3 0 2 , 3 1 0 1 , 4 9 0 C o m p r e s s i o n C r u s h i n g S t r e s s a t P r o - 1 , 8 2 0 2 , 1 4 0 2 . 8 1 0 2 , 2 2 0 2 , 9 8 0 2 . 3 1 0 P a r a l l e l t o p o r t i o n a l L i m i t ( p s i ) 3 . 7 1 0 4 , 1 5 0 4 , 9 5 0 4 , 4 5 0 5 , 2 9 0 3 , 9 7 0 6 r a i n M a x i m u m C r u s h i n g S t r e s s 2 , 4 7 0 2 , 7 7 0 3 . 6 1 0 2 , 8 6 0 3 , 5 8 0 2 . 7 8 0 ( p s i ) 5 , 3 5 0 5 , 9 2 0 7 , 2 7 0 6 , 2 7 0 6 , 7 8 0 4 , 9 2 0 M o d u l u s o f E l a s t i c i t y 1 , 3 1 0 1 , 4 6 0 1 , 6 7 0 1 , 4 2 0 1 , 6 2 0 1 . 1 7 0 ( 1 0 0 0 p s i ) 1 , 6 5 0 1 , 7 5 0 1 , 9 7 0 1 , 6 6 0 1 , 7 5 0 1 . 3 2 0 C o m p r e s s i o n S t r e s s a t P r o p o r t i o n a l 2 4 5 2 3 4 4 6 0 2 7 6 3 7 3 2 7 8 P e r p e n d i c u l a r L i m i t ( p s i ) 5 0 0 5 2 3 8 7 1 5 2 9 6 5 7 4 9 7 t o G r a i n T A B L E 6 . ( c o n t . ) S p e c i e s A t t r i b u t e T e s t W h i t e A m a b i l i s D o u g l a s - L o d g e p o l e W e s t e r n W e s t e r n s p r u c e f i r f i r p i n e h e m l o c k r e d c e d a r H a r d n e s s L o a d R e q u i r e d t o S i d e 2 7 9 3 2 2 4 8 1 3 6 2 4 6 8 2 6 5 I m b e d 0.444 i n . 4 2 3 4 4 2 6 7 2 49a 6 1 7 3 3 0 S p h e r e t o H a l f E n d 3 2 0 4 0 6 5 8 9 3 3 9 5 6 1 4 3 1 D i a m e t e r ( l b ) 5 5 5 8 3 5 9 0 3 6 7 3 9 9 2 6 7 4 S h e a r P a r a l l e l M a x i m u m S t r e s s ( p s i ) 6 7 0 7 1 4 9 2 2 7 2 4 7 5 2 6 9 6 t o G r a i n 9 8 5 1 , 0 9 3 1 , 3 8 2 1 , 2 3 8 9 4 0 8 0 9 C l e a v a g e S p l i t t i n g S t r e n g t h ( l b . / 1 5 6 1 6 8 2 1 6 1 8 6 2 0 2 1 3 6 i n . w i d t h , 3 i n . l o n g ) 2 2 1 2 1 0 2 2 2 2 9 7 2 1 4 1 4 5 T e s i o n P e r p e n - M a x i m u m S t r e s s ( p s i ) 3 0 7 2 7 4 4 0 7 3 3 2 3 9 0 2 3 8 d i c u l a r t o 4 7 5 4 4 4 4 4 4 5 4 8 4 2 5 3 5 7 G r a i n N o t e : V a l u e s i n t h e f i r s t l i n e f o r e a c h p r o p e r t y a r e t h e s p e c i e s m e a n s i n t h e u n s e a s o n e d c o n d i t i o n ; t h o s e i n t h e s e c o n d l i n e a r e a d j u s t e d t o 1 2 p e r c e n t m o i s t u r e c o n d i t i o n . 30 properties of whole pole from white spruce have been obtained from ava i l a b l e l i t e r a t u r e sources (Eggleston, 1952; Sugden, 1979), and are presented i n Table 7. For sake of comparison, data from western red cedar, lodgepole pine, amabilis f i r and western hemlock poles are also included. On the basis of the data given i n the table, i t i s evident that both amabilis f i r and western hemlock are p o t e n t i a l candidates as substitutes for western red cedar and lodgepole pine poles, at least i n terms of mechanical strength properties. On the other hand, white spruce appears to have lower strength properties than any of the species l i s t e d . This might be a cause for concern, p a r t i c u l a r l y when considering t h i s species as a source of longer poles. 2.2.2 PROBLEMS ASSOCIATED WITH WHITE SPRUCE During the past decade, the Eastern Forest Products Laboratory (EFPL) conducted numerous studies on the t r e a t -ment of white spruce with waterborne preservatives (Krzyzew-s k i , 1978; Rak, 1977a,b and c; Rak and Clarke, 1975a; Ralph and Shields, 1984a and b). However, because of the d i f f i -c u l t y i n penetrating t h i s species with preservatives, limited use has been made of i t for the production of preserved wood products. Due to the pole shortage i n the early 1970s, several T A B L E 7 . S u m m a r y o f p o l e s t r e n g t h t e s t s . T r e a t m e n t M o d u l u s o f R u p t u r e 3 P o l e M o . C o e f f . S p e c i e s O r i g i n D r y i n g P r e s e r v a t i o n L e n g t h o f A v e r a g e S t d . o f V a r . 5% S o u r c e 0 ( f t . ) P o l e s ( p s i ) D e v . {%) F r a c t i l e W h i t e B . C . A i r B e t h e l - P C P 3 5 5 3 4 9 6 1 9 5 1 1 9 . 2 3 5 6 2 1 s p r u c e B . C . A i r B e t h e l - A C A 3 5 5 3 4 9 1 1 6 8 4 1 3 . 9 3 8 7 2 1 A m a b i l i s B . C . K i l n B e t h e l - P C P 3 5 5 2 5 6 4 2 1 0 3 2 1 8 . 3 4 1 1 8 1 f i r B . C . K i l n B e t h e l - A C A 3 5 5 1 5 1 9 4 7 8 1 1 5 . 0 4 0 1 6 1 W e s t e r n B . C . N o n e N o n e 2 5 5 2 6 1 3 5 7 3 9 1 2 . 0 4 9 9 9 1 h e m l o c k B . C . A i r C r e o s o t e 2 5 5 0 6 4 3 2 9 7 5 1 5 . 2 4 9 6 3 1 B . C . K i l n B e t h e l - P C P 3 5 5 2 7 4 8 3 1 0 2 6 1 3 . 7 5 9 2 2 1 B . C . K i l n B e t h e l - A C A 3 5 5 0 6 9 6 7 1 0 3 4 1 4 . 8 5 4 0 7 1 L o d g e p o l e U . S . A . - C C A - 9 5 8 3 6 - - - 2 p i n e B . C . N o n e N o n e 2 5 2 3 5 8 0 9 6 2 7 1 0 . 8 4 8 3 9 1 B . C . A i r R u e p i n g - C r e o s o t e 2 5 2 4 6 6 7 1 8 6 2 1 2 . 9 5 3 5 3 1 A l t a . N o n e N o n e 2 5 2 3 6 6 0 4 6 6 7 1 0 . 1 5 5 6 7 1 A l t a . N o n e N o n e 2 5 2 5 6 5 8 1 5 2 7 8 . 0 5 7 5 2 1 U . S . A . N o n e N o n e 2 5 6 4 9 5 5 5 4 2 1 0 . 9 4 1 1 6 1 U . S . A . A i r R u e p i n g - C r e o s o t e 2 5 6 5 1 7 4 4 9 2 9 . 5 4 4 0 6 1 U . S . A . A i r R u e p i n g - C r e o s o t e 3 0 2 1 5 1 5 0 6 8 4 1 3 . 3 4 1 0 6 1 U . S . A . N o n e N o n e 4 5 5 4 2 2 0 6 4 8 1 5 . 3 3 2 4 5 1 T A B L E 7 . ( c o n t . ) T r e a t m e n t M o d u l u s o f R u p t u r e 9 P o l e N o . C o e f f . S p e c i e s O r i g i n D r y i n g P r e s e r v a t i o n L e n g t h o f A v e r a g e S t d . o f V a r . 5% S o u r c e * 3 ( f t . ) P o l e s ( p s i ) D e v . (%) F r a c t i l e W e s t e r n U . S . A . - C C A r e d c e d a r U . S . A . - C C A U . S . A . - C C A B . C . N o n e N o n e 3 0 B . C . - B u t t T r e a t e d 3 0 B . C . N o n e N o n e 3 0 B . C . N o n e N o n e 3 0 B . C . N o n e N o n e 3 0 U . S . A . N o n e N o n e 3 0 U . S . A . N o n e N o n e 3 0 2 4 3 9 5 - - - 2 3 5 2 0 7 - - - 2 5 4 8 8 2 - - - 2 5 1 5 2 2 9 7 6 3 1 4 . 6 4 0 7 5 2 5 4 6 9 4 8 8 5 1 8 . 9 3 3 9 1 5 1 4 5 8 7 5 9 9 1 3 . 1 3 6 7 2 4 0 5 7 8 7 8 7 7 1 5 . 2 4 4 6 6 4 0 5 6 2 0 8 2 7 1 4 . 7 4 3 7 0 2 6 5 5 5 0 5 1 4 9 . 3 4 7 4 6 2 5 5 3 2 5 5 0 5 9 . 5 4 5 3 6 T h e g r o u n d l i n e M O R v a l u e s w e r e d e t e r m i n e d a p p r o x i m a t e l y a t 6 f e e t a b o v e t h e b u t t . 1) S u g d e n ( 1 9 7 9 ) 2 ) E g g l e s t o n ( 1 9 5 2 ) wood-treating companies examined the s u i t a b i l i t y of spruce as pole material. It has been reported by Rutherford (1977) of Domtar that, i n experiments conducted on spruce, p o t e n t i a l problems existed due to excessive checking formation and d i f -f i c u l t y i n obtaining an adequate treatment. This i s consist-ent with the world l i t e r a t u r e i n which the refractory behav-iour of several species of spruce i s described (Banks, 1973? Dunleavy et a l . , 1973a and b? Hauffe, 1970? Hackbarth, 1975? Liese and Bauch, 1967; Rak, 1977a? Rak and Clarke, 1975a? Siau and Shaw, 1971? U n l i g i l , 1971). It i s generally known that spruce wood i s very low i n natural decay resistance (MacLean, 1935? Nicholas and Siau, 1973? Panshin and De Zeeuw, 1970? USDA, 1974). For example, untreated fence posts of white spruce have an average service l i f e of only 3.2 years i n eastern Canada (Krzyzewski and Sedziak, 1974). Thus any damage by checking a f t e r shallow treatment could expose spruce wood with low natural d u r a b i l i t y to high decay hazard. Despite extensive studies (Hackbarth, 1975? Hackbarth and Liese, 1975? Liese and Bauch, 1967? Rak, 1977a? Siau, 1970), the reasons for the refractory nature of spruce are not f u l l y understood. Liese and Bauch (1967) have proposed that the low permeability of the ray c e l l s i s due to the r e l a t i v e l y small proportion of ray tracheids. However, i n a more recent study conducted by Hackbarth and Liese (1975) on spruce treated with two waterborne preservatives, copper chrome f l u o r i d e and copper chrome borate, they concluded that neither the number nor the area of ray c e l l s influenced the preservative penetration, and rather increasing density and the proportion of latewood both reduced the preservative absorption. Sapwood was found to be more permeable than heartwood and a x i a l penetration i n sapwood was t h i r t y - f o u r times greater than that i n either the r a d i a l or tangential d i r e c t i o n s . The only chemical factor for which a p o s i t i v e influence was detected was the solution concentration, sug-gesting that increasing the solution strength caused a re-duction i n the amount of so l u t i o n absorbed (Harkbarth and Liese, 1975). Recently Rak (1977a) has also suggested that s t r u c t u r a l reasons for the low permeability of spruce are fewer bordered p i t s with smaller margo pores, and less e f f i -cient c a p i l l a r y connections between ray parenchyma on cross-f i e l d s than i n permeable species such as pines. White spruce heartwood i s undoubtedly one of the most d i f f i c u l t woods to t r e a t . Although the range of permeability i s thought to be r e l a t i v e l y narrow i n spruce, exceptions to t h i s may occur depending on the species of spruce, t h e i r geographic location and rate of growth (Ralph and Shields, 1984b). In addition permeability may be affected by such factors as the method of log storage, time of year the material i s cut, as well as several other v a r i a b l e s . Per-meability also d i f f e r s within a single annual ring with earlywood bands often being more permeable than latewood. This phenomenon i s frequently observed as a banding e f f e c t i n some pressure-treated spruce (Ralph and Shields, 1984b). 2.3 FACTORS AFFECTING THE TREATABILITY OF SPRUCE ROUNDWOOD The Canadian wood preservation industry has r e l i e d heavily on s p e c i f i c wood species for pressure treatment. Consequently, more permeable wood species for use i n pre-servative-treated commodities have become depleted i n Canada. Thus spruce can be a convenient replacement for them from abundant l o c a l resources provided that i t can be treated to levels adequate to protect commodities i n ground contact. In general, the problem of treating d i f f i c u l t l y pene-trable species such as spruce has been attacked by three basic methods. These are: (1) the use of enzymes, molds, or bacteria (microbiological); (2) i n c i s i n g and v a r i a t i o n of the treating conditions (physical); and (3) preservative type and formulation (chemical). 2.3.1 MICROBIOLOGICAL STUDIES A number of researchers have shown that microorganisms and enzymes ean increase the permeability of wood. Work i n 36 t h i s area was i n i t i a t e d by Lindgren and Harvey (1952) when they found that Trichoderma mold improved the permeability of southern pine sapwood sprayed with f l u o r i d e solutions. Several subsequent studies (Dunleavy et a l . , 1973a and b; Ellwood and Ecklund, 1959; Greaves and Barnacle, 1970; Knuth and McCoy, 1962; Schulz, 1968; U n l i g i l , 1971 and 1972a) have reported that bacteria and other fungi also e f f e c t i v e l y i n -crease the permeability of wood, indicating that the increased permeability i s p r i n c i p a l l y due to degradation of the ray c e l l s and p i t membranes. For example, steeping spruce poles for two months i n stagnant water caused a breakdown of the p i t membranes, r e s u l t i n g i n an improved permeability of the ray c e l l s (Dunleavy et a l . , 1973b). The degree of improve-ment depends upon both the time of year and the duration of ponding, r e f l e c t i n g the e f f e c t of water temperature on bac-t e r i a l a c t i v i t y . Schulz (1968) also observed that penetra-t i o n of fluor-chrome arsenic phenol (FCAP) preservative increased up to 67% i n the sapwood region of ponded spruce poles. S i m i l a r l y , when treating ponded white spruce pole sections with CCA preservative, U n l i g i l (1971) reported a 50% greater s o l u t i o n absorption. For creosote treatment, the improvement i n permeability was even more marked, with increased retentions up to 179% ( U n l i g i l , 1971 and 1972a). According to U n l i g i l , the e f f e c t s of ponding are limited to the sapwood zone. Although bacteria were detected throughout the sapwood, only the r e s i n canals, e p i t h e l i a l c e l l s and ray parenchyma were p a r t i c u l a r l y affected i n the inner region. He also suggested that attack of the surface of the pole section by soft rot fungi may have contributed to the improved permeability. Since i t i s known that microorganisms degrade wood by enzymatic action, i t i s l o g i c a l to assume that permeability could be increased by treatment with enzymes. This'assump-tio n was v e r i f i e d i n a study by Nicholas and Thomas (1968) which showed that several enzymes attack the p i t membranes in l o b l o l l y pine sapwood, re s u l t i n g i n a s i g n i f i c a n t increase i n permeability. U n l i g i l and Krzyzewski (1972) attempted to improve the permeability of spruce by enzymatic decomposition of the p e c t i c substances i n the liquid-f&ow-controlling t o r i . Dunleavy and his co-workers (1973b) have also conducted a s i m i l a r study on water-stored spruce logs to examined water-stored spruce logs for enzymatic a c t i v i t y , p a r t i c u l a r l y that involving pectate lyase, since degradation products from p e c t i c substances ( i . e . p i t membranes) would enhance further lyase a c t i v i t y . While the enzymatic pretreatment of pole material may improve the o v e r a l l permeability, i t remains unclear whether any s i g n i f i c a n t improvement i n penetration i n the r a d i a l d i r e c t i o n i s obtained. Indeed Adolph (1976) h a s s u g g e s t e d t h a t i m p r e g n a t i o n r a d i a l l y i s much more d i f f i -c u l t t h a n i n e i t h e r t h e t a n g e n t i a l o r a x i a l d i r e c t i o n . A s s u m i n g t h a t b o r d e r e d p i t membranes and t o r i a r e p a r t i a l l y d e s t r o y e d , t h i s w o u l d l e a d t o i m p r o v e d t a n g e n t i a l movement b e c a u s e o f b o r d e r e d p i t s b e i n g o n t h e r a d i a l f a c e s . The u s e o f m i c r o o r g a n i s m s and enzymes t o i m p r o v e t h e p e r m e a b i l i t y o f wood i s a d v a n t a g e o u s b e c a u s e t h e y a r e s e l e c -t i v e i n t h e i r a t t a c k , t h u s m i n i m i z i n g s t r e n g t h l o s s . A c c o r d -i n g t o U n l i g i l ( 1 9 7 2 a ) , s t a t i c b e n d i n g t e s t s o n a i r - d r i e d s m a l l , c l e a r s p e c i m e n s o f w h i t e s p r u c e i n d i c a t e d a s l i g h t l o s s i n s t r e n g t h . However, D u n l e a v y and h i s c o - w o r k e r s (1973b) h a v e r e p o r t e d t h a t s t r e n g t h t e s t s on f u l l - s i z e d S i t k a s p r u c e ( P i c e a s i t c h e n s i s (Bong.) C a r r ) p o l e s i n d i c a t e d t h a t a n y r e d u c t i o n r e s u l t i n g f r o m p o n d i n g was n e g l i g i b l e . They f o u n d t h a t an a d d e d b e n e f i t o f p o n d i n g o f p o l e s was t h e c l e a n s u r f a c e a p p e a r a n c e a f t e r t r e a t m e n t w i t h o i l - b o r n e p r e s e r v a -t i v e s . C o n c e r n i n g r oundwoods s u c h as u t i l i t y p o l e s , However, t h e r e a r e c e r t a i n p r o b l e m s . W a t e r s t o r a g e o f p o l e s l e a d s t o e x t r a h a n d l i n g s i n c e t h e y must b e p l a c e d i n w a t e r and l a t e r b e s t a c k e d f o r d r y i n g . F u r t h e r m o r e t h e p o l e s a r e d i f f i c u l t t o d r y and t h e r i s k o f d e c a y d u r i n g t h e d r y i n g p r o c e s s i n -c r e a s e s . E x p e r i m e n t s w i t h enzyme t r e a t m e n t s h a v e s o f a r b e e n c a r r i e d o u t m o s t l y o n s m a l l wood s p e c i m e n s . T h e r e f o r e , 39 studies on the a p p l i c a b i l i t y of enzyme treatments to round-woods are required. At present, the enzyme preparations are s t i l l too expensive to have a p r a c t i c a l use. Although use of the mould fungus Trichoderma i s a simple method to improve permeability of softwood (Bergman, 1984), i t i s not used i n p r a c t i c e . Presumably t h i s i s because a mould attack i s s t i l l regarded as a gateway to wood decay. 2.3.2 PHYSICAL STUDIES 2.3.2.1 INCISING While natural seasoning or a r t i f i c i a l preconditioning normally improve results of treatment, some refractory species require additional preparation i n order to obtain s a t i s f a c t o r y treating r e s u l t s . At present, the most commonly imployed method of preparing these species i s i n c i s i n g , which i s per-formed on both sawn and round material. Incising has been one of the most e f f e c t i v e and least c o s t l y methods of iroprove-ing the t r e a t a b i l i t y of wood (Nicholas and Siau, 1973). By mechanically rupturing the wood c e l l s at periodic i n t e r v a l s along and across the piece, the structure i s rendered s u f f i -c i e n t l y porous to permit the flow of preservative solutions into the incised zone. A number of reports indicate that the permeability of spruce to preservatives can be improved by i n c i s i n g (Banks, 1973; Horn et a l . , 1977; Krzyzewski and Shields, 1977; Mohler, 1969; Ralph and Shields, 1984a). Banks (1973) has reported the development of a close-spaced i n c i s i n g pattern for use on spruce lumber, and i n a very recent study (Ralph and Shields, 1984a) i n c i s i n g of spruce lumber proved bene-f i c i a l by increasing preservative penetration i n the heart-wood areas of boards, even when treated by the thermal d i f -fusion process. Horn and his co-workers (1977) have shown that i n c i s i n g spruce poles c l e a r l y enhances both the pene-t r a t i o n and retention of waterborne preservatives applied by pressure impregnation. They also noted that an addition-a l benefit r e s u l t i n g from i n c i s i n g was the dramatic lowering of the concentration gradient over the outer 1.2 i n . (3 cm) a n a l y t i c a l zone, with the pattern of 1.2 i n . (3 cm) deep in c i s i o n s staggered 0.4 i n . (1 cm) and l a t e r a l l y 1.2 i n . (3 cm). Thus by choosing a suitable spacing and depth of i n c i s i o n s , i t i s possible to provide poles with a more uniform preservative treatment. In addition to improving treatment res u l t s , a secondary benefit provided by i n c i s i n g i s the reduction of deep checks (Krzyzewski and Shields, 1977) The main disadvantages of i n c i s i n g are that i t produces a rough surface and results i n some strength loss (Mohler, 1969) Nicholas and Siau, 1973). However, for most products such as pole and timber, these disadvantages are not too 41 serious and i n c i s i n g undoubtedly w i l l continue to be the p r i n c i p a l method of improving t r e a t a b i l i t y . 2.3.2.2 VARIATION OF THE TREATING CONDITIONS To a c e r t a i n extent, the treatment results can be altered by using d i f f e r e n t treating cycles. For example, i t i s gen-e r a l l y known that the f u l l - c e l l process can be used to maxi-mize retention. Furthermore, the Lowry and Rueping processes can be used to reduce retention while obtaining better pene-t r a t i o n compared with the f u l l - c e l l process (Canadian I n s t i -tute of Timber Construction, 1971). Pressure processes used with oilborne solutions may be either f u l l - c e l l or empty-c e l l , while the f u l l - c e l l process i s almost always used with the waterborne solutions (Kennedy, 1981). Although these pressure-treating processes have proven to be e f f e c t i v e means of impregnating wood with preservative solutions i n most cases, they do not provide adequate treatment of refractory wood. This i s mainly the result of i n s u f f i c i e n t pressure to overcome the a i r - l i q u i d interfaces i n the extremely small pores of this type of wood (Nicholas and Siau, 1973). Thus i t i s anticipated that s i g n i f i c a n t l y better results could be obtained by a l t e r i n g the treating schedule (e.g. pressure and temperature). The work by MacLean (1935) c l e a r l y showed that increasing the pressure from 100 to 250 p s i (689 to 1723 kPa) improved the treatment of refractory wood. However, the research by Siau (1970) and Walters and Whittington (1970) has indicated that considerably higher pressures are required to obtain complete impregnation of this type of wood. Although an increase i n pressure appears to be a means of achieving better treatment of refractory wood, increasing the duration of applied pressure rather than i t s magnitude was found to be more b e n e f i c i a l to improving penetration (Hackbarth, 1975). These results are i n agreement with those of an e a r l i e r study by Hauffe (1970), who also noted the b e n e f i c i a l e f f e c t of increasing the temperature of creosote solution when treating black spruce (Picea mariana (Mill.) B.S.P.). Both Hauffe and Bosshard (1968), who investigated the use of high pressures and temperatures on the impregna-tion of Norway spruce (Picea abies (L.) Karst.) with c o a l -tar o i l , concluded that pressures greater than 150 p s i (1032 kPa) and temperatures in excess of 100°C caused damage to the wood structure. It was also observed during treatment of squared timbers of white spruce that collapse occurred at about 65°C i n some timbers, mostly on heartwood faces (Krzyzewski, 1978). This e f f e c t has not been observed in the treatment of roundwood, but u n t i l such time as the i n -fluence of temperature i s determined, Krzyzewski has recom-mended that the temperature should not be higher than that indicated. A number of p i l o t plant studies (Krzyzewski, 1978; Rak, 1975 and 1977c) have been conducted on white spruce lumber and roundwood to determine optimum treating conditions. Using a modified treating schedule, i . e . flow i n preserva-t i v e at 57°C with pressures up to 150 p s i (1032 kPa), Krzyzewski (1978) obtained good penetrations and retentions in a large number of spruce roundwood treated with ammoniacal s a l t preservatives. This observation i s in agreement with that reported by Rak (1975>. The treating schedule plays an important role in achiev-ing a s a t i s f a c t o r y preservative treatment. However, i t should be noted that c e r t a i n factors place r e s t r i c t i o n s on the pres-sure and temperature used. As Nicholas and Siau (1973) point out, s u s c e p t i b i l i t y of wood to collapse varies with the pres-sure, permeability, wood species, si z e of the specimen, type of preservative, rate of pressure increase, and preservative temperature. Consequently, a l l these factors must be con-sidered when the use of higher pressure i s contemplated. 2.3.3 CHEMICAL STUDIES The t h i r d area of research a c t i v i t y to increase the p e n e t r a b i l i t y of spruce i s the proper s e l e c t i o n of chemicals and additives for formulations. Since the c h a r a c t e r i s t i c s of the treating s o l u t i o n have an e f f e c t on the treatment of wood, the problem of treating d i f f i c u l t l y penetrable species such as spruce has been attacked by using more penetrative preservatives (e.g. ACA) and t h e i r modifications. Long experience with aqueous ammonia as a solvent for inorganic preservative s a l t s as o r i g i n a l l y used i n the U.S.A. ( F r i t z , 1947? Gordon, 1947) for the treatment of a d i f f i c u l t - t o -treat white f i r (Abies concolor (Gord. & Glend.) Lindl.) prompted t r i a l s of t h i s solvent for the treatment of Cana-dian spruce (Rak, 1977a). Since then, ammonia has been used in preservative formulation studies and in the development of a copper-zinc-arsenic (CZA) preservative system for t r e a t -ment of spruce (Clarke and Rak, 1974; Rak, 1976; Rak and Clarke, 1975a). Rak (1977a) reported that the permeability of spruce roundwood in the r a d i a l d i r e c t i o n was improved using an aqueous ammoniacal solution of inorganic s a l t s , compared with ordinary aqueous solutions. On the basis of this obser-vation, experimental ammoniacal preservatives, copper-arsenic additive (CAA) and copper-zinc-arsenic-additive (CZAA), devel oped by Rak (1976 and 1977c) and Rak and U n l i g i l (1977), have provided high chemical retentions and excellent sapwood pene-t r a t i o n i n white spruce. These preservatives have improved f i x a t i o n properties i n the wood compared to conventional ACA, are toxic to a wide range of fungi, and at the same time reduce the amount of arsenic necessary for t h e i r formulation. CAA i s now included i n the Canadian Standards Association preservation standard CS'A 080 as a modification of ACA, while CZAA has been accepted p r o v i s i o n a l l y as ammoniacal copper zinc arsenate (ACZA). A commercial schedule for treatment of spruce with the new preservative, copper-ammonia-additive, was prepared by Krzyzewski and Rak (1973) i n which a pressure of 150 p s i (1032 kPa) and temperatures ranging from 52°C to 75°C were employed. Encouraging results with this treating schedule were reported by Rak (1977c), Ralph and Shields (1984a) and U n l i g i l and Krzyzewski (1978) with both pressure treatments and d i f f u s i o n treatments of the groundline bandage-type on spruce having moisture contents above the f i b e r saturation point. P o s i t i v e economic benefits of ACA or ACZA systems include a wider yet less expensive range of woods (e.g. Picea and Populus species) that can be treated (Ralph and Shields, 1984a). 2.4 PROTECTION OF POLES WITH WATERBORNE CHEMICALS With increasing importance of communications and power supply i n everyday l i f e , experience has led u t i l i t y companies to specify preservative treatment to ensure continued strength and eliminate the high cost of replacement. For these reasons, preservative treatment of most species of poles has been em-ployed by means of pressure impregnation for many years. Although creosote was the f i r s t preservative to become established i n Canada, a number of other preservatives have since followed and the wood-preserving industry has s e t t l e d on a few basic materials and formulations which have stood the test of time. Wood preservatives can be arranged into two broad categories: organie-solvent substances (oilborne) and water-soluble inorganic s a l t s (waterborne). Five o i l -borne preservatives are described i n the Canadian Standard for wood preservation using pressure processes (CSA-080 Wood Preservation, 1983a). They are creosote, pentachlorophenol, bis ( t r i b u t y l t i n ) oxide, copper-8-quinolinolate and copper naphthenate. On the other hand, of the common waterborne preservatives, two systems such as CCA and ACA are most widely used i n Canada (Smith, 1977) and provide excellent and long-l a s t i n g protection of treated wood against biodegradation (Gjovik and Davidson, 1972). Three preservatives have been in common use for u t i l i t y poles pressure-treated i n accordance with the CSA 080.4 spec-i f i c a t i o n s , namely creosote, PCP and CCA. Although PCP i s s t i l l the main preservative employed for u t i l i t y poles, the 47 waterborne preservatives are gaining more acceptance by some u t i l i t y companies. Since the early 1970s, considerable e f f o r t has been devoted towards the development of new wood preservatives (Butcher et a l . , 1977? Clarke and Rak, 1974? Johnson and Gutzmer, 1978? Rak and Clarke, 1975a? Sparks, 1978) and, because of the r e l a t i v e l y high cost of organic solvents, much of t h i s a c t i v i t y has been directed to developing water-soluble rather than o i l - s o l u b l e formulations. These waterborne pre-servatives involve chemicals which are toxic to fungi, and preferably show some a b i l i t y for f i x a t i o n i n the wood, thereby preventing t h e i r subsequent leaching from wood when in contact with water. Approved formulations of preservatives used in Canada are covered by Standard CSA-080 Wood Preservation. Good examples of such formulations are CCA, ACA and CAA, the f i r s t two of which form the bulk of waterborne preservatives currently used i n Canada. ACA i s p a r t i c u l a r l y a t t r a c t i v e since the penetration of ammonia into a l l components of wood substance, and i t s action on the structure of wood are iden-t i f i e d as factors a f f e c t i n g the t r e a t a b i l i t y of spruce. 2.4.1 CHROMATED COPPER ARSENATE (CCA) The chromated copper arsenates are known i n the American Wood-Preservers' Association (AWPA, 1984) and CSA (1983b) as Type A, B, and C, l i s t e d i n t h e i r order of acceptance as AWPA standards. These formulations d i f f e r p r i n c i p a l l y i n the proportions of arsenic and chromium present i n each fo r -mulations d i f f e r p r i n c i p a l l y i n the proportions of arsenic and chromium present i n each formulation. A l l three, on the oxide basis, contain about 19% CuO. Type A i s high i n chromium, Type B high i n arsenic, while Type C i s intermedi-ate. Type C i s close in composition to the numerical averag of Types A and B, and also close to the two widely used B r i t i s h formulations, Tanalith C and Celcure A. The compo-s i t i o n of each type of CCA preservatives i s shown i n Table 8 CCA preservatives have been used widely for many years throughout the world for treating permeable species. A l -though a l l three types of CCA could be used, only Types B and C have found extensive use since the introduction of CCA preservatives into the Canadian standards. However, the s i t u a t i o n has changed such that Type C formulation i s now favoured by CCA treaters, mainly due to i t s adoption by a major chain of Type B users and due i n part to a desire by treaters to use a preservative with a lower arsenic content (Ruddick, 1982). Research i n various countries has looked into many aspects of CCA preservative system for treating wood, thus enabling properties such as f i x a t i o n of toxic chemicals, TABLE 8. Composition of the CCA preservatives. AWPA standards^ Type A Type B Type C CSA 2 Standards Cr0 3(%) 59.4(65.5)69.3 33.0(35.3)38.0 44.5(47.5)50.5 3 6 - 6 5 CuO(%) 16.0(18.1) 20.9 18.0(19.6)22.0 17.0(18.5) 21.0 19 As 20 5(%) 14.7(16.4)19.7 42.0(45.1)48.0 30.0(34.0)38.0 1 6 - 4 5 Sources: 1. American Wood-Preservers' Association (1984). 2. Canadian Standards Association 080, Wood Preservation (1983b). Note: Figures in parentheses represent nominal composition on the oxide basis others represent range. t h e i r resistance to leaching, water repellency, e l e c t r i c a l r e s i s t i v i t y , p a i n t a b i l i t y , and cost to be controlled (Rak and Clarke, 1975a). This has been possible by varying the nature and the r a t i o of the copper, chromium and arsenic components. In CCA solution, these three components are a l l water-soluble. When the solution i s impregnated into wood, f i x a t i o n depends on an oxidation-reduction reaction between chromium components i n the preservative and reducing groups in the wood substance, thereby preventing t h e i r subsequent leaching from wood (Rak and Clarke, 1975b). Since the rate of the reduction-oxidation reactions i s a function of the concentration of the reducing compound and temperature, the s t a b i l i t y of the preservative system i s limited during both treatments and storage. For this reason, maximum tre a t i n g temperatures of only 49°C are allowed by the AWPA and CSA standards. A protracted schedule necessary for treating d i f f i c u l t - t o - t r e a t species leads to problems with early pre-c i p i t a t i o n of toxic chemicals (Rak and Clarke, 1975a). It has been also reported by Rak and Clarke (1975b) that v a r i a -tion of the chemical components i n the preservative solution did not provide s u f f i c i e n t control over the rates of the oxidation-reduction reactions to enable adequate penetration to be achieved. 51 2.4.2 AMMONIACAL COPPER ARSENATE (ACA) Information in support of ACA, under the trade name "Chemonite", was submitted to the AWPA Preservatives Committee in 1949 (Baechler, 1949), following the papers presented to the Association i n 1947 ( F r i t z , 1947? Gordon, 1947? Ott, 1947). The o r i g i n a l patent was issued to Gordon i n 1939. ACA was o r i g i n a l l y prepared at the treating plant by mixing a copper chemical with arsenic t r i o x i d e in ammonium hydroxide. Because of the components used, the preservative was i n c o r r e c t l y c a l l e d ammoniacal copper arsenite. However, in the mid-1970s, i t was r e a l i z e d that t h i s was erroneous, since during the mixing process, the a i r oxidized the arsenic to the pentavalent form (Ruddick, 1982). Thus the name was changed to ammoniacal copper arsenate. ACA has been used for many years on the west coast of the United States and i s now widely used in Canada. 2.4.2.1 CHEMICAL COMPOSITION AND FORMULATION The h i s t o r i c a l development of the s p e c i f i c a t i o n s for ACA composition i s shown i n Table 9. According to the o r i g -i n a l standards (Beachler, 1949? Gordon, 1947), ACA was fo r -mulated from copper hydroxide, arsenic t r i o x i d e , acetic acid, and ammonia. Although no d e f i n i t e information i s available, i t i s u n l i k e l y that copper hydroxide i s used i n the formulation T A B L E 9 . H i s t o r i c a l d e v e l o p m e n t o f A C A c o m p o s i t i o n . A W P A S t a n d a r d s 1 9 4 9 l P r o p o s a l 1 9 5 3 A c c e p t a n c e 1 9 6 9 O x i d e B a s i s 1 9 8 4 4 O x i d e B a s i s C S A S t a n d a r d s C u a s C u ( O H ) 2 ( % ) 6 0 + 5 5 5 . 7 ( 5 7 . 7 ) 5 9 . 7 - - -A s a s A s 2 O 3 O 6 ) 4 0 + 5 3 8 . 7 ( 4 0 . 7 ) 4 2 . 7 - - -C u a s C u O ( % ) - - ( 4 9 . 8 ) 4 7 . 7 m i n . ( 4 9 . 8 ) 4 7 . 7 m i n . 4 9 . 8 - 6 3 . 0 A s a s A & 2 0 5 ( % ) - - ( 5 0 . 2 ) 4 7 . 6 m i n . ( 5 0 . 2 ) 4 7 . 6 m i n . 3 7 . 0 - 5 0 . 2 N H 3 2 . 0 - 3 . 0 % i n s o l n . 1 . 5 - 2 . 0 x C u ( O H ) 2 1 . 5 - 2 . 0 x C u O 1 . 5 m i n . x C u O 1 . 5 - 3 . 5 x C u 0 A c e t i c a c i d ( * ) 0 . 0 5 i n s o l n . 1 1 6 1 . 7 m a x . 1 . 7 m a x . -C a r b o n a t e a s CO 2 - - - - 0 . 0 - 0 . 8 x C u O S o u r c e s t 1 . B a e c h l e r ( 1 9 4 9 ) 2 . ( 1 9 5 3 ) 3 . A m e r i c a n W o o d - P r e s e r v e r s ' A s s o c i a t i o n ( 1 9 7 1 ) 4 . ( 1 9 8 4 ) 5 . C a n a d i a n S t a n d a r d s A s s o c i a t i o n 0 8 0 , W o o d P r e s e r v a t i o n ( 1 9 8 3 b ) N o t e : F i g u r e s i n p a r e n t h e s e s r e p r e s e n t n o m i n a l c o m p o s i t i o n ; o t h e r f i g u r e s r e p r e s e n t r a n g e . of ACA, because of i t s higher cost i n the preparation rather than the su l f a t e or basic carbonate (Winter et a l . , 1965). However, the d i r e c t use of copper su l f a t e may be somewhat undesirable i f the re s u l t i n g ACA solution i s to be used i n the treatment of u t i l i t y poles, where residual conductivity i s unwanted (Hartford 1973). Over the past 30 years, the ACA preservative system has become well established, and i t s formulation presently con-tains equal weights of cupric and arsenic oxides, plus op-t i o n a l small amounts of ammonium acetate or bicarbonate, a l l dissolved i n 4-6% of aqueous ammonia. Acetate ions enhance copper s o l u b i l i t y , and carbonate ions render the surface of the treated wood more water repellent (Kennedy, 1981). Un-l i k e CCA, the ammoniacal preservative i s not marketed as a prepared formulation. With the oxidation of AS2O3 to AS2O5, the ammonia i n the solvent reacts with the copper arsenate to form a soluble complex: 3CuO + A s 2 0 3 + I 2 N H 3 + 4H 20 » 3Cu(NH 3) 4 2 + + 2H 2 As04 _ + 40H~ (1) This soluble complex is stable in ammonium hydroxide solution. 2.4.2.2 MECHANISM OF FIXATION The f i x a t i o n of ammoniacal copper systems i n wood has been reported by Eadie and Wallace (1962), Rak and Clarke (1974) and Sundman (1984). While the CCA preservative depends on a reaction between the preservative components and the wood, the f i x a t i o n of ammoniacal copper compounds depends on the v o l a t i l i z a t i o n of ammonia and the i n s o l u b i l i z a t i o n of the preservative. Following impregnation of the ACA into the wood, the ammonia i n the solvent evaporates. Although the soluble com-plex in ammonium hydroxide solution i s stable as shown i n reaction (1), i t readi l y breaks down to form insoluble copper arsenate when the solvent i s removed: o+ _ » 1 2 N H 3 3Cu(NH 3) 4 z + 2H 2As0 4 + 40H~ ^ > C u 3 ( A s 0 4 ) 2 • 4H20 (2) For t h i s reason, the ACA system i s r e l a t i v e l y r e s i s t a n t to leaching when the treated wood i s placed i n service and the formulation enables time and temperature to be varied with-out danger of premature p r e c i p i t a t i o n of toxic chemicals, provided that loss of ammonia from the treating solution i s prevented (Rak and Clarke, 1974). However, Wilson and his co-workers (1955) reported that the ACA-treated wood has lower arsenic f i x a t i o n . Copper arsenate-treated wood has proven to be one of the most durable of the preservative treatments used today. A l -though i t i s r e l a t i v e l y non-leachable and the ACA preservative i s highly e f f e c t i v e , considerable e f f o r t has been devoted towards the development of several ammonia-based preserva-tives that make use of the method of f i x a t i o n applied in ACA (Butcher et a l . , 1977; Clarke and Rak, 1974; Rak and Clarke, 1975a). In accelerated laboratory and f i e l d tests, i t has been shown that these modified preservatives are more r e s i s t -ant to leaching compared with ACA. Ammoniacal copper borate (ACB) i s another s i m i l a r l y p r e c i p i t a t e d preservative (Johnson and Gutzmer, 1978; Vinden and McQuire, 1984). 2.5 FACTORS INFLUENCING THE EFFECTIVENESS OF PRESERVATIVE SYSTEMS Preservative systems must perform t h e i r function through-out the service l i f e of the product under a variety of expo-sure conditions. Thus, u t i l i t y poles must be treated with systems that protect both the a e r i a l and below-ground portions for several decades i n a v a r i e t y of climates, s o i l s and leach-ing conditions. In general, the effectiveness of a wood-preservative treatment i n preventing deterioration i s dependent on the treatment r e s u l t s , as well as the preservative system. The two main c r i t e r i a used to e s t a b l i s h the effectiveness of a preservative treatment are depth of penetration and l e v e l of chemical retention. Almost a l l wood products purchased today are inspected for conformance with a results-type s p e c i f i c a -t i o n , because an accurate measure of both penetration and retention would indicate whether the wood was properly treated. 2.5.1 PENETRATION It has been recognized that there are a number of factors a f f e c t i n g penetration other than treating techniques. These are species, p i t aspiration, sapwood depth, sap stain, i n c i s -ing technique, dryness, and season of the year. Regardless of what causes lack of penetration, i t affects service l i f e . For example, poles which do not receive adequate penetration are subject to decay i n the untreated sapwood and low-reten-ti o n zones near the point of termination of seasoning checks. These checks normally close at or near the groundline, and rain water running down the inside of checks accumulates dust, spores and moisture. Therefore, the wood should be adequately treated well beyond the point of penetration of these checks to prevent i t from decay hazard. While i t i s often observed that the depth of penetra-tion i s approximately uniform on a l l sides of the material, not infrequently the penetration i s much deeper at some points than others, showing an untreated core of wood of ir r e g u l a r or star-shaped cross section (Best, 1974; Bramhall, 1966). The causes of thi s naturally vary, but are known to include factors such as off-center p i t h , thickness of the growth 57 rings, density, sap s t a i n , moisture content differences, and checking pattern (Arsenault, 1973). Since sapwood i s perishable, i t i s important that i t should be thoroughly treated to prevent early f a i l u r e s . In general, the depth of sapwood controls the depth of penetra-tion (Arsenault, 1966; Hearn, 1951). In species where the sapwood i s thin, as well as in large poles and timbers, i n -c i s i n g procedures have been practised for more thorough penetration (Banks, 1973; Best and Martin, 1969; Graham and Estep, 1966; Ruddick, 1978). Although i n c i s i n g may encourage formation of several shallow checks rather than one major check, i t i s i n s u f f i c i e n t in preventing formation of checks that extend beyond the zone of treated wood. This i s p a r t i c -u l a r l y true when the depth of penetration i s shallow, as in d i f f i c u l t - t o - t r e a t species having a narrow sapwood (Graham and Estep, 1966). Thus the use of saw kerfs has been employed to reduce deep checking through the thin sapwood (Graham, 1973; Graham and Estep, 1966; Helsing and Graham, 1976; Ruddick, 1981; Ruddick and Ross, 1979). It has been concluded that ke r f i n g i s much more e f f e c t i v e than i n c i s i n g i n c o n t r o l l i n g checking i n roundwood, p a r t i c u l a r l y when treated with water-borne preservatives. Some aspects of v a r i a b i l i t y i n penetration are described above, namely, species, off-center p i t h , and sapwood depth. Other factors a f f e c t i n g penetration, e s p e c i a l l y lack of pene-t r a t i o n i n the inner sapwood, may include water pockets or areas of saturation due to the presence of mold fungi or bacteria, or i n c i p i e n t decay (Arsenault, 1973). However, more importantly, causes of v a r i a b i l i t y related to treatment practices include treating poles and lumber of widely d i f f e r -ent moisture contents, following various periods and methods of a i r drying. Several researchers (Coetzee and Laar, 1976; Krzyzewski, 1978; Rak, 1977a; Ruddick, 1978) have shown that when material i s impregnated with a waterborne preservative, increasing the moisture expedites the spread of preservative and results in deeper preservative penetration. According to Krzyzewski (1978), the optimum p r a c t i c a l condition i s the medium range of 28 to 35% moisture content. However, since the worst checks i n a pole frequently extend more than two inches into the pole, Ruddick (1978) recommended to conduct the treatment of roundwood at moisture contents not exceeding 25%. Indeed, there i s even concern that the current commer-c i a l practice of drying the material to just less than 25% moisture content does not e s t a b l i s h adequate checking patterns p r i o r to treatment. To a cert a i n extent, t h i s may be a l l e v i -ated by pretreatments such as i n c i s i n g and/or k e r f i n g . Complete penetration of the sapwood should be the ideal in a l l pressure treatments. Although long experience has 59 shown that even s l i g h t penetrations have some value, deeper penetrations are highly desirable to avoid exposing untreated wood when checks occurs i n service, p a r t i c u l a r l y for important members of high replacement cost. Whatever the cause, i f wood i s not adequately penetrated, early f a i l u r e s would r e s u l t . 2.5.2 RETENTION The second c r i t e r i o n used in establishing the e f f i c a c y of preservative treatment i s the amount of chemical retained in wood. The retention of preservative i s an equally impor-tant factor influencing the effectiveness of preservative systems in extending the service l i f e of treated wood pro-ducts. However, i t should be noted that net retention of preservative by the treated wood alone i s not an adequate index of the e f f i c i e n c y of treatment. As mentioned previously, t h i s i s because the preservative can be concentrated i n c e r t a i n areas of the wood, leaving wide variations in depth of pene-t r a t i o n . In general, the frequency d i s t r i b u t i o n of retention in a group of treated poles shows a normal d i s t r i b u t i o n . Thus i t i s obvious that many of the treated poles w i l l have below-average retentions. Also, i t i s obvious that some of them w i l l be i n the r i s k retention l e v e l category sp e c i f i e d i n the appropriate standards. These low-retention poles are candidates for early f a i l u r e . Not only are poles d i f f e r e n t from each other, but retentions within a pole are as variable as those among poles. M i l l s and his co-workers (1965) have suggested that while 30 to 40% of the v a r i a t i o n i n retention can be explained by measured physical c h a r a c t e r i s t i c s , 60 to 70% of pole-to-pole v a r i a t i o n i s normal due to other factors. A study con-ducted by Arsenault (1966) on the penta retention v a r i a t i o n in standard pole species reported that percentage v a r i a t i o n i s less near the surface of the wood than at greater depths, where permeability differences add to the v a r i a t i o n . The more refractory species such as Douglas-fir and lodgepole pine have greater v a r i a t i o n between poles compared with red and southern pines. As described e a r l i e r , the retention of preservative i n wood i s influenced by several factors, including permeability and surface-to-volume r a t i o . These two factors account for the large differences i n absorption between small-diameter and large-diameter poles (Arsenault, 1973). Varying surface-to-volume r a t i o s explain the fact that the top of poles receive considerably more treatment than the butts, and small-diameter poles in a cylinder charge tend to be overtreated when the large poles are adequately treated. In a study of the causes of v a r i a t i o n i n retentions, M i l l s e_t a l . (1965) found that the retentions on a weight per cubic foot basis were not s i g n i f i c a n t l y affected by eithe r density or ring count. Also, i t has been reported by Cse r j e s i et al.(1967) that there is apparently no c o r r e l a t i o n between s p e c i f i c gravity and absorption of preservative on a weight per surface area basis from waterborne solutions of a n t i s t a i n chemicals (e.g. copper s u l f a t e or sodium pentachlorophenate) applied to western hemlock and Douglas-fir lumber. Therefore, as a p r a c t i c a l matter, a uniform method of assigning weight per unit volume retentions to species and products should be used (Arsenault, 1966), avoiding any consideration of density differences between species. 2.5.3 TREATMENT RESULTS OF SPRUCE WITH AMMONIACAL WOOD PRESERVATIVES Extensive experimentation and i n d u s t r i a l t r i a l s with ammoniacal preservative solutions have yielded favourable results i ndicating that spruce roundwood, lumber and plywood can be treated successfully by pressure process (Krzyzewski, 1978; Krzyzewski and Rak, 1973; Krzyzewski et a l . , 1978; Krzyzewski and Shields, 1977; Rak, 1977a, b, and c; Rak and Clarke, 1975a). Encouraging results were also reported by Ralph and Shields (1984a and b) with non-pressure treatments (e.g. thermal d i f f u s i o n process) of spruce with moisture contents above the f i b e r saturation point. C s e r j e s i (1984) has reported improvements in pole resistance to c e r t a i n types of decay organisms when treated with ammoniacal wood preserv-a t i v e s . The CSA (1983c) presently allows for the use of spruce poles treated with ACA at 0.6 l b . / f t . 3 (9.6 kg/m3) oxide retention with a minimum penetration of 0.5 in.(13 mm) and 100% sapwood up to a depth of 0.75 in.(19 mm). However, even these minimum requirements, p a r t i c u l a r l y for retention, are often not achieved with spruce roundwood, i n spite of pretreatments to improve preservative uptake. In a study of preservative treatment of white spruce poles with ACA, Ruddick (1978) found that they showed excellent penetration of preserv ative, but the chemicals retained were not s u f f i c i e n t to s a t i s f y the l e v e l established by the CSA standard. These observations correlate c l o s e l y with those reported by several investigators (Coetzee and Laar, 1976; Gohre, 1958; Krzyzewski 1978; Rak, 1977a), i n that excellent preservative-penetration values were obtained, while the chemical retentions were much lower than anticipated. As mentioned previously, the problem of treating d i f f i -c u l t l y penetrable species such as spruce has been solved i n two ways: by increasing the permeability of the wood, and by using more penetrable preservatives. Several researchers (Banks, 1973; Horn e_t a l . , 1977) 63 have shown that i n c i s i n g spruce wood c l e a r l y enhances the permeability of waterborne preservatives applied by pressure impregnation, thus improving the penetration of preservatives. It has also been reported by numerous investigators (Dunleavy et a l . . 1973a and b; Krzyzewski, 1973; Schulz, 1968; U n l i g i l , 1971 and 1972a) that the improvement i n the permeability was s i g n i f i c a n t l y marked when treating ponded spruce material with preservatives. Considerable e f f o r t has also been made to study the eff e c t of ammonia on various components of the wood substance and some physico-chemical properties of ammonia-treated wood (Bariska and Popper, 1971 and 1975; Bariska et_ a l . , 1969; Davidson and Baumgardt, 1970; Rak, 1977a). These studies can be summarized by saying that penetration of ammonia into a l l components of wood substance, and i t s action on the substance of wood are i d e n t i f i e d as factors a f f e c t i n g the t r e a t a b i l i t y . Indeed Rak (1977a) has indicated, i n his permeability studies of spruce using a method previously developed (Rak, 1964), that an ammo-ni a c a l s o l u t i o n of copper arsenate i s an excellent candidate for the treatment of spruce. Studies of the permeability of spruce sapwood microsections to ACA and CCA preservatives proved that the ammoniacal system penetrates 1.7 to 1.8 times faster i n the r a d i a l d i r e c t i o n than the CCA system. The per-meability i n the tangential d i r e c t i o n was 3.8 times better on the average (Rak and Clarke, 1975a). These results were con-firmed by pressure treatments of spruce lumber (Rak, 1975) and spruce roundwood (Rak, 1977c) with both preservatives. Sup-porting evidence for these observations i s also provided by the fact described by Rak (1977a) that the permeability of spruce sapwood to an aqueous ammoniacal solution of inorganic s a l t s was found to be better than a p l a i n water s o l u t i o n . He also found that t h i s improved rate of penetration was inde-pendent of the nature of the s a l t s i n ammoniacal s o l u t i o n . The e f f e c t of ammonia on various components of the wood substance has been investigated on model systems with anhy-drous l i q u i d ammonia by many researchers (Bariska and Popper, 1975; Bariska et a l . , 1969; Fukada, 1968; Marrinan and Mann, 1956; Rak, 1964; Schuerch, 1964; Wellard, 1954). It was often compared with the in t e r a c t i o n of water with wood sub-stance. Marrinan and Mann (1956) suggested that anhydrous l i q u i d ammonia converts c e l l u l o s e I (native cellulose) at about 55°C into c e l l u l o s e HI (ammonium cellulose) which may be reverted back to c e l l u l o s e I by water at room temperature. It i s generally known that the crystallographic unit of c e l l u l o s e HE i s geometrically d i f f e r e n t from that of c e l l u l o s e I. Of the reported e f f e c t s of ammonia on wood, Rak (1977a) concluded that only two appeared to be c l o s e l y related to spruce t r e a t a b i l i t y . F i r s t , anhydrous l i q u i d ammonia can 65 penetrate a l l components of the wood substance including c r y s t a l l i n e c e l l u l o s e , i n the better and faster absorption of aqueous ammonia than of water by spruce sapwood. Secondly, ammonia changes the microstructure, reducing the c e l l wall dimensions and forming a new system of c a p i l l a r i e s made up of intertracheal separations i n the compound middle lamella of c e l l walls and also separations between ray c e l l s and longitudinal tracheids. The other properties of ammonia and i t s e f f e c t s on wood, such as i t s p l a s t i c i z i n g e f f e c t , chemical changes i n hemicelluloses a f f e c t i n g the f i b e r saturation point, sorption and equilibrium moisture content, and d e n s i f i c a t i o n of wood, are rather related to the properties of treated wood i t s e l f (Rak, 1977a). However, i t i s believed that they i l l u -s t r ate the nature of the treatment with ammoniacal solutions. Since the structure of wood i s obviously a very impor-tant factor i n i t s impregnation with preservative, i t would seem that i t s r e l a t i o n s h i p to wood preservation would have < been investigated very intensively. However, thi s i s not the case. The l i t e r a t u r e contains many more references to s p e c i f i c a t i o n s , p ractice and technique than to the c r i t i c a l factor of wood anatomy. In the reports on the e f f e c t of wood structure, more deal with the bordered p i t pairs, since these p i t s are the most c r i t i c a l , s ingle feature influencing l i q u i d movement i n the r e l a t i v e l y simple organization of tissues in coniferous woods. Spruce i s p a r t i c u l a r l y d i f f i -c u l t to treat with waterborne preservatives i f the moisture content i n the wood i s allowed to f a l l below the f i b e r satu-ration point. Under these conditions, i t i s generally known that continuity of the c a p i l l a r y system i s impaired by a s p i -rated t o r i i n bordered p i t s , and the secondary wall of t r a -cheids has rather higher a f f i n i t y to hydrophobic l i q u i d s than to the water (Rak and Clarke, 1975). Thus i t i s possible that the anatomical features of spruce, forming the pathways by which a chemical penetrates r a d i a l l y in the sapwood, con-ta i n c o n s t r i c t i o n s which cause premature p r e c i p i t a t i o n of the preservative, r e s u l t i n g i n an enhanced chemical retention and less chemical penetration. Using a scanning electron microscope coupled to an X-ray energy analyzer, however, Ruddick (1978) f a i l e d to locate any consistent high concen-trations of copper arsenate i n a regular pattern which would have confirmed t h i s hypothesis. Gross c e l l u l a r inclusions, in the form of c r y s t a l l i n e deposits of copper arsenate , were located i n several v e r t i c a l e p i t h e l i a l c e l l s of samples of the ACA-treated spruce, although the adjoining longitudinal resin canals were devoid of copper arsenate. However, the neighboring horizontal resin canals and associated e p i t h e l i a l c e l l s contained no large deposits. Thus he concluded that i t i s not possible to interpret the poor retention as being 67 mainly due to a blockage of the pathways by which the preserv-ative permeates the wood. As mentioned e a r l i e r , the empty-cell process i s known to produce an enhanced chemical penetration and less retention. While there may be other possible interpretations, at the present time high moisture content appears to be the most plausible explanation for the observations of ACA-treated spruce material with s a t i s f a c t o r y penetrations but low reten-tions . Rak (1977a) has suggested that the i n i t i a l moisture content of spruce roundwood affects the gross absorptions and depth of penetration of ammoniacal solutions, i n that increasing the moisture expedites the spread of preservative and results in deeper ^chemical penetration while decreasing the chemical retention. Indeed Krzyzewski (1978) reported that in his study of the treatment of white spruce poles with ammoniacal s a l t preservative, high retentions were obtained at low moisture content (20 to 30%) while deep penetrations were secured at high moisture content (above 75%) . These general observations correlate c l o s e l y with those reported by other investigators (Coetzee and Laar, 1976; Gohre, 1958; Ruddick, 1978), in that an increase in moisture content causes a reduction in chemical retention. This may e a s i l y be accounted for by the d i l u t i n g influence of the water 68 already present in the wood. On the other hand, the chemical would be able to di f f u s e r e a d i l y from the preservative solu-tion to the water present i n the c e l l lumens, resu l t i n g in better penetration at high moisture content. Indeed Ruddick (1978) has used moisture v a r i a t i o n present inside the poles to explain the results from his spruce pole study. The short air- d r y i n g period of about f i v e months, while allowing the outer sapwood to dry to less than 25% moisture content, would have a smaller e f f e c t on the moisture l e v e l of both the tran-s i t i o n zone and the heartwood, which were indeed i n excess of 30% moisture content for 86% of a l l pole tests. The effectiveness of a wood-preservative treatment may also depend on the uniform d i s t r i b u t i o n of a l l chemical components, p a r t i c u l a r l y in waterborne preservative systems. Good performance of the s a l t treatments i s p a r t i a l l y a t t r i b -uted to the fact that they are absorbed into the c e l l wall and uniformly di s t r i b u t e d in the wood. Very recently, however, Ruddick and his co-workers (1981, 1984a) have reported a d i s -proportionate uptake of chemical components, such as copper and arsenic, in ACA-treated woods. This can be explained as being due to the adaptability of these components to the f i x a t i o n process. The importance of these observations l i e s i n the fact that the arsenic content i n the wood should not be allowed to f a l l to unacceptably low levels (Ruddick, 1984a) which might permit decay by any copper-tolerant fungi such as Phialophora spp. Although spruce can be treated with preservative to sa t i s f a c t o r y l e v e l s by using aqueous ammonia solutions, studies of pressure treatments of spruce roundwood have showed an influence of i n i t i a l moisture content on preservative pene-t r a t i o n and retention. With the observations of excellent penetrations but low retentions, this i s a fundamental, f i r s t -order problem to overcome. I t should be also noted that beyond the question of t r e a t a b i l i t y to conventional levels of penetration and retention i s the question of service l i f e , since the p r i n c i p a l factor involved i n deciding the longevity of service l i f e of a pole i s the degree and severity of check-ing in service. 2.6 BIODETERIORATION OF CHEMICALLY TREATED WOOD Various species of wood have c e r t a i n unique characteris-t i c s that allow one species to be dif f e r e n c i a t e d from another, and the same i s true of an abundance of microorganisms which inhabit and degrade both untreated and preservative-treated wood. Microscopical patterns of such degradation are a re-sultant of the combination of these two p a r t i c i p a t i n g com-ponents, as well as the effectiveness of preservative systems in the treated wood products. Differences in decay s u s c e p t i b i l i t y between untreated and chemically treated wood have long been studied. In addition to substandard treatment of wood, however, i t has been recognized that there are the two other basic reasons for the premature f a i l u r e of chemically treated wood, namely d e t o x i f i c a t i o n or removal of preservative chemicals by wood-inhabiting and wood-destroying microorganisms, and preserva-t i v e tolerance by ce r t a i n fungi. 2.6.1 DETOXIFICATION OR REMOVAL OF PRESERVATIVE CHEMICALS BY MICROORGANISMS Laboratory tests have shown that Fusarium sp. i s able to break down the dinitrophenol component of FCAP preserva-t i v e , allowing treated wood to be attacked by non-tolerant fungi such as Coprinus sp. (Madhosingh, 1961a and b). Drisko and O ' N i e l l (1966) reported that some microorganisms found on creosoted p i l e s metabolized naphthalene, phenanthrene and neutral fractions of creosote. Losses of arsenic from FCAP-treated wood and of PCP have been noted when the treated wood was exposed to non-wood-destroying fungi (Duncan and Deverall, 1964). Similar r e s u l t s have been obtained on exposure of PCP-treated wood to Trichoderma v i r i d e ( U n l i g i l , 1972b). Numerous laboratory tests have also shown the ef f e c t s of wood-destroying fungi on preservatives. DaCosta and Osborne (1968) reported that Lenzites sp. affected the water s o l u b i l i t y and/or t o x i c i t y of CCA preservative i n treated wood without causing any decay. Coniophora sp. caused con-siderable loss of PCP from pine blocks treated with subtoxic amounts of the preservative ( U n l i g i l , 1968). It has been reported by Levi (1976) that several wood-decaying fungi such as Poria spp. s o l u b i l i z e d and absorbed copper, chromium and arsenic components from the wood treated with CCA preserva-t i v e , suggesting that the presence of even small amounts of mycelium i n wood may r e s u l t i n the s o l u b i l i z a t i o n of CCA components. Bacteria have long been known to be associated with wood i n service (Levy, 1975; Smith, 1975). In recent years several researchers (Drysdale and Hedley, 1984; Leightley, 1982; Nilsson, 1982) have intensively studied the e f f e c t of bacteria on treated wood products such as posts and poles, and as the t h i r d major type of decay, b a c t e r i a l degrade has been frequently observed in such products. It i s believed that the colonization by bacteria i n association with fungi i s the i n i t i a l part of the process of decay, and t h i s i n i t i a l c o l o nization of wood by bacteria i s established p a r t l y by random action on the surface zones of the samples, but mostly by invasion through the ray parenchyma c e l l s (Liese and Greaves, 1975). Detailed discussions on b a c t e r i a l degrade have been offered i n several works (Drysdale and Hedley, 1984; Leightley, 1982; Nilsson and Holt, 1983; Schmidt and Liese, 1982) . In the absence of good preservation practice, there can be l i t t l e doubt that the major cause of wood degradation i n service i s due to organisms. Even where biodegradation i s adequately controlled by the c a r e f u l application of known wood preservation technology, i t i s now recognized that other forms of degradation may play a s i g n i f i c a n t r o l e i n damaging wood i n service. In very recent studies (Banks and Evans, 1984; Carey, 1982; Voulgaridis and Banks, 1981), i t has been observed that surface layers of wood were degraded by the action of water. As Carey (1982) points out, the increased moisture contents may play another role i n encouraging sub-sequent colonization by wood destroying organisms. Despite these numerous studies, very limited data i s available on the p r a c t i c a l s i g n i f i c a n c e of such observations. In fact, the relevance of some of the laboratory results to the f i e l d s i t u a t i o n has been questioned (Le u t r i t z , 1965). F i e l d evaluations of preservative performance, p a r t i c u l a r l y i n u t i l i t y poles, have been concerned s o l e l y with the length of time the treated material remains serviceable. A number of studies (Duncan and Lombard, 1965; Eslyn, 1970; Zabel et  a l . , 1980 and 1982) have simply examined the fungi associated with decay i n such treated poles. It i s now recognized that 73 f i e l d tests of wood preservatives should determine not only the performance l i f e of treated wood products but also the fate of the preservative i n the wood. The i d e n t i t y and the effe c t s of organisms colonizing wood, both untreated and treated, have also been the v i t a l subject of many i n v e s t i -gations (Clubbe and Levy, 1982). E f f e c t i v e studies of f i e l d performance should incorporate a l l the elements, i . e . service l i f e , attacking organisms and biodegradation of preservatives, In t h i s way, i t would be possible to determine the importance of d e t o x i f i c a t i o n or removal of preservative and thus predict more accurately the performance of the preservative system. 2.6.2 PRESERVATIVE TOLERANCE BY WOOD_DECAYING FUNGI In the same manner as fungi exert s e l e c t i v e influences on various types of media, i . e . a c i d i f i e d , benomyl and/or te t r a c y c l i n e , or phenol-added malt agar, due to t h e i r t o l e -rance to such substances (Clubbe and Levy, 1977; Hale and Savory, 1976; Hunt and Cobb, 1971; Smith, 1983), service experience and laboratory tests have shown that preservative tolerance varies with fungal species and s t r a i n . It has also been found that within-species differences are often greater than between-species differences (Levi, 1973). The frequency with which tolerant fungi occur i n the f i e l d , and the economic f e a s i b i l i t y of impregnating s u f f i c i e n t preserv-74 ative into wood to protect against tolerant fungi may deter-mine the l i k e l i h o o d of fungal decay of chemically treated wood. It has been thought that s o f t rot fungi may be the ultimate cause of f a i l u r e of preservative-treated softwoods (Hulme and Butcher, 1977a and b; Smith, 1977). Certainly many species have the a b i l i t y to tolerate quite high l e v e l s of commonly used wood preservatives, which results in pre-mature f a i l u r e of treated wood products i n service (Dale, 1976). The dominant sof t rot fungi belong to the genus Phialophora. Members of this genus have shown very active soft rot a b i l i t y (Nilsson, 1973) and prominent tolerances to copper (Leightley, 1979 and 1980; Nilsson and Henningsson, 1978). Very recently, Leightley and his co-workers (Francis and Leightley, 1983; Leightley and Armstrong, 1980) reported that transmission electron microscopy of the copper-tolerant Phialophora species revealed a d i s t i n c t i v e e x t r a c e l l u l a r layer around hyphae. The presence of e x t r a c e l l u l a r polysac-charides on the hyphae of wood decay fungi suggests some phy s i o l o g i c a l r o l e . As Green (1980) suggested, i t i s believed that these layers act as matrices for hyphal substrate contact and subsequent enzymic a c t i v i t y . Some of the Basidiomycetes, true wood-destroying fungi, have also shown high tolerance to c e r t a i n preservatives. For example, Lentinus lepideus i s known to be tolerant to creosote and the fungus i s widespread i n nature. Thus i t i s necessary to treat wood products, such as r a i l r o a d t i e s and u t i l i t y poles, treated with s u f f i c i e n t creosote to control t h i s fungal species, even though considerably smaller quantities would control other wood-destroying fungi. Duncan and Lombard (1965) reported that f a i l u r e to do th i s had led to premature f a i l u r e to many creosote-treated t i e s and poles. It has also been known that some Poria spp. are highly tolerant to CCA preserv-ative (DaCosta and Kerruish, 1964; Levi, 1975). Using elec-tron microscopy, Levi (1975) found that copper, chromium and arsenic i n CCA-treated pine wood were absorbed from the S2 layers of tracheids i n and/or onto the hyphae of P_. monticola, but the concentration of these three components varied greatly from hypha to hypha. He explained that t h i s v a r i -ation may have been due to differences i n the binding capac-i t i e s of the various c e l l s i t e s for copper, chromium and arsenic. It i s generally known that laboratory tests are e s s e n t i a l to avoid the problem of decay s u s c e p t i b i l i t y of chemically treated wood i n service by tolerant fungi ( U n l i g i l , 1972b). Laboratory tolerance tests are not always f e a s i b l e . There-fore, f i e l d tests on preservatives should i d e n t i f y tolerant decay fungi so that laboratory test data can be related to 76 service experience. 2.7 NITROGEN ENHANCEMENT DUE TO ACA TREATMENT Nitrogen i s present i n wood i n r e l a t i v e l y small amounts, comprising more than about 0.03% but usually less than 0.1% of the dry weight of wood ( A l l i s o n et a l . , 1963; Cowling, 1970; Heck, 1929; M e r r i l l and Cowling, 1966; Rennie, 1965; Young and Guinn, 1966). L i t t l e i s known concerning the n i -trogenous materials i n wood, largely because the small amounts present are commercially unimportant. But to wood-inhabiting microorganisms and insects that derive t h e i r nourishment p r i -marily from the wood i t s e l f , these small amounts of nitrogen are of paramount importance. Numerous researchers (Cowling, 1970; Cowling and M e r r i l l , 1966; Findlay, 1934; Henningsson, 1976; King et a l . , 1980; M e r r i l l and Cowling, 1965 and 1966) have shown that the rate of decay of wood by fungi i s related d i r e c t l y to i t s nitrogen content. As mentioned previously, i t i s generally assumed that, during the f i x a t i o n of the ammonia-based wood preservative, the ammonia i s lo s t from the wood. However, t h i s has not been v e r i f i e d yet. Therefore, the question of whether loss of ammonia from the ACA-treated wood i s complete or not, could well prove important, p a r t i c u l a r l y when inadequate treatment of d i f f i c u l t - t o - t r e a t and non-durable woods, such as spruce, i s encountered. Very l i t t l e work has been conducted on the nitrogen enhancement of ACA-treated wood. Based on the method devel-oped by Rennie (1955), Ruddick (1979) determined the nitrogen, content of wood with ACA treatment, using an Orion Micropro-cessor ionalyser, as described i n the Orion operating manuals (1977 and 1978). In his study of the nitrogen content of ACA-treated wood, the enhancement of nitrogen was e a s i l y detectable a f t e r nine months of storage of treated ponderosa pine (Pinus ponderosa Laws.) sapwood stakes indoors, and a f t e r two years of storage outdoors of discs cut from treated spruce pole material. However, the nitrogen content of the spruce samples was much less (< 50%) than that of the pine stakes, possibly indicating loss of chemical due to leaching. From the spruce samples, he concluded that the ammonia pene-t r a t i o n was s i g n i f i c a n t l y greater than that of the preserva-t i v e solution i n some of the wood where no copper or arsenic could be detected. There are also indications from the ACA pressure t r e a t -ment of c e r t a i n wood species, which darken i n colour during treatment, that the ammonia may penetrate farther into the wood than the preservative. For example, when Douglas-fir wood i s pressure-treated with ACA, i t darkens i n colour. The cause of t h i s darkening i s presumably related to the 78 use of ammonium hydroxide i n the preservative, since the treatment with other waterborne preservatives (e.g. CCA) which also contain copper and arsenic does not give t h i s reaction. Because ammonia i s readi l y liberated from ammonium hy-droxide. Ruddick (1979) has suggested that, during the pres-sure treatment of wood with ACA, the ammonia penetrates the wood c e l l s p r i o r to the preservative solution. Indeed Rak (1977a) has used th i s fact to explain the improved permea-b i l i t y of spruce to ACA compared with CCA. It has been also suggested by Ruddick (1979) that, during the f i x a t i o n process, some of the ammonia diffuses further into the wood. Based on these two suggestions, which have not been v e r i f i e d , he has concluded that an enhancement of the nitrogen l e v e l could r e s u l t i n non-preservative-treated wood. 2.8 FUNGAL METABOLISM OF NITROGEN Although the previous study (Ruddick, 1979) has proven that the wood treated with ACA preservative i s enhanced in i t s nitrogen l e v e l , i t i s s t i l l questionable in which chemi-c a l form t h i s enhanced nitrogen i s present i n the wood, and also whether fungi are capable of metabolizing t h i s source of nitrogen to promote t h e i r growth. Increasing the nitrogen content of wood frequently increases the rate of decay by wood-destroying fungi. However, there i s c o n f l i c t i n g evidence 79 as to whether decay can be increased appriciably by a r t i f i -c i a l l y adding nitrogen to wood. To date, l i t t l e or no work has been performed on these questions. Nevertheless, answers may be inferred p a r t l y on the basis of more recent knowledge of fungal metabolism of nitrogen, derived from combined b i o -chemical and genetical studies. Fungal nitrogen sources are quite varied and may be organic or inorganic i n nature. In the same manner as the degree of s p e c i a l i z a t i o n depends p a r t l y on whether the fungus possesses enzymes to degrade insoluble carbon sources (e.g. starch, c e l l u l o s e , l i g n i n ) , or whether i t can u t i l i z e only soluble carbon compounds, the nitrogen can exert a s e l e c t i v e influence. For example, the a b i l i t y to assimilate n i t r a t e confers a higher degree of n u t r i t i o n a l independence (autotropy) than does the need for ammonia or ammonia-compounds, and an even stronger dependence (heterotropy) exists when s p e c i f i c nitrogen compounds, i . e . a p a r t i c u l a r amino acid, are required (Muller and L o e f f l e r , 1976). In general, not a l l fungi use nitrogen sources with equal f a c i l i t y , and a fungus may have a requirement for nitrogen in a s p e c i f i c form. Fungi may u t i l i z e inorganic nitrogen i n the form of n i t r a t e s , n i t r i t e s or ammonia, or organic nitrogen in the form of amino acids. A few fungi may be able to obtain nitrogen v i a the d i r e c t u t i l i z a t i o n of molecular nitrogen (Smith, 1970). However, 80 It i s questionable whether the f i x a t i o n of atmospheric nitrogen, which i s so well-known among bacteria (Seidler et a l . , 1972), occurs with fungi. Interestingly, Henningson and Nilsson (1976) reported that nitrogen compounds had mi« grated to treated transmission poles from surrounding s o i l . Having shown that during drying of wood, soluble nitrogenous and carbohydrate materials accumulate at evaporative faces of wood. King and his co-workers (1974, 1976, 1979 and 1980) also showed that such soluble materials not only enhanced decay rate of wood in s o i l by soft rot, but stimulated con-siderable movement of nitrogen to wood which was attributed to microbial biomass. Most fungi can use ni t r a t e s as a sole or s i g n i f i c a n t source of nitrogen, but as Moore-Landecker (1972) points out, i n a b i l i t i e s to u t i l i z e n i t r a t e s are common among the higher Basidiomycetes to which most wood-decaying fungi belong. As presented in Table 10, i t has been postulated by several researchers (Nason, 1962; Nason and Takahashi, 1958; Nicholas, 1963) that n i t r a t e i s reduced via n i t r i t e and hydroxylamine to ammonia in a series of steps which are e s s e n t i a l l y electron transfer reactions. The enzymes involved contain a number of cofactors and metals, and u t i l i z e NADH or NADPH (see Table 10) as a hydrogen donor. There i s s t i l l some doubt about the possible existence of an organic reductive route from TABLE 10. Summary of Ni t r a t e Reduction (Nason, 1962; Nason and Takahashi, 1958; Nicholas, 1963). Possible pathway Oxidation/ reduction state of N Hydrogen donor Co-factors Enzyme NOr +2e NO 2 +2e (HNO) n i t r o x y l group or (N20) nitrous oxide group or N0 2 N H 2 nitramide or H 2 N 2 0 2 hyponitrous acid + 2e N H 2 O H hydroxylamine N H . +5 + 3 + 1 -1 NADH or NADPH2 NADH or NADPH NADH or NADPH FAD" Fe M O FAD Cu Fe FAD Mg Mn Nitr a t e reductase N i t r i t e reductase Hypo-n i t r i t e reductase Hydroxyl-amine reductase Reduced nicotinamide adenine dinucleotide 2 Reduced nicotinamide adenine dinucleotide phosphate F l a v i n adenine dinucleotide n i t r i t e t o ammonia, b u t i t i s g e n e r a l l y a c c e p t e d t h a t t h e i n o r g a n i c r e d u c t i v e p a t h w a y i s t h e i m p o r t a n t one i n f u n g i ( P a t e m a n a n d K i n g h o r n , 1 9 7 6 ) . From t h e e q u a t i o n shown i n T a b l e 10, i t i s p r o b a b l e t h a t one o r more i n t e r m e d i a t e compounds a r e f o r m e d b e t w e e n n i t r i t e and h y d r o x y l a m i n e a t t h e +1 o x i d a t i o n s t a t e f o r t h e n i t r o g e n atom. The n a t u r e o f t h e p o s t u l a t e d i n t e r m e d i a t e s i s u n c e r t a i n ; n i t r o x y l , h y p o n i t r i t e (N2O2), n i t r o g e n d i o x i d e (NC^) and n i t r o u s o x i d e h a v e a l l b e e n c o n s i d e r e d as p o s s i b i l i t i e s ( N a s o n , 1962; N i c h o l a s , 1963; P a t e m a n and K i n g h o r n , 1 9 7 6 ) . The n i t r a t e i o n may b e i n c o r p o r a t e d i n t o t h e wood c e l l s as ammonium, p o t a s s i u m , o r c a l c i u m n i t r a t e ( C o c h r a n e , 1 9 5 8 ) , and t h e n m ust be r e d u c e d t o t h e o x i d a t i o n l e v e l o f ammonia b e f o r e t h e n i t r o g e n c a n b e a s s i m i l a t e d i n t o o r g a n i c compounds. N i t r i t e i s f o r m e d f r o m n i t r a t e , and t h u s i n one s e n s e i s u t i l i z e d b y a l l f u n g i w h i c h c a n u s e n i t r a t e . A l t h o u g h n i t r i t e i s known t o be t o x i c t o many f u n g i and b a c t e r i a , i t c a n b e u s e d as a n i t r o g e n s o u r c e b y some f u n g i , i . e . A s p e r - g i l l u s s p p . , F u s a r i u m s p . N e u r o s p o r a s p p . P e n i c i l l i u m s p p . and U s t i l a g o s p . ( P a t e m a n and K i n g h o r n , 1 9 7 6 ) . On t h e o t h e r h a n d , a s w i t h n i t r a t e , i t i s l i k e l y t h a t t h e g r e a t m a j o r i t y o f f u n g i c a n u s e ammonia as a s o l e n i t r o g e n s o u r c e . T h i s h a s b e e n o b s e r v e d i n numerous f u n g i , s u c h a s A l t e r n a r i a s p . , A s p e r g i l l u s s p p . , B o t r y t i s s p . , C l a d o s p o r i u m s p . , 83 Coprinus s p i , Dip loci ia sp. , Mucor sp., Neurospora spp., PeniciIlium spp. and Ustilago sp. (Lewis and Fincham, 1970; Morton and Macmillan, 1954; Pateman et a l . , 1967). It i s generally recognized that the form i n which the ammonia i s supplied i s important. The fungi may use nitrogen i n the form of ammonium ion (NH^ "1") which can be supplied as ammonium hydroxide or ammonium s a l t s . Although the fungi are capable of metabolizing both n i t r a t e or n i t r i t e and ammonium ion, ammonium ion i s known to be preferred because i t requires less energy expenditure by the fungus to use thi s reduced form of nitrogen. It i s interesting to note that some nitrogen sources function as a toxic substance in the form of ammonium hy-droxide sol u t i o n . Because treating wood with a l k a l i (e.g. NaOH and N H 4 O H ) increases decay resistance i n both the laboratory and the f i e l d (Amburgey and Johnson, 1978; Baechler, 1959; Highley, 1970 and 1973), a l k a l i treatments have been proposed as an alt e r n a t i v e method of wood protec-t i o n . I t has been assumed that the a l k a l i treatment may destroy thiamine (Dwivedi and Arnold, 1973), which i s essen-t i a l for treatment may also increase decay resistance i n wood by reducing the a v a i l a b i l i t y of other micronutrients e s s e n t i a l for fungal growth (Baechler, 1959), or by increasing the pH or ammoniacal nitrogen content (Highley, 1973). I f ammonium s a l t s , i . e . ammonium n i t r a t e , are favoured over ammonium hydroxide, as Moore-Landecker (1972) points out, these s a l t s are u t i l i z e d poorly or possibly not at a l l by some fungi (e.g. the Blas t o c l a d i a l e s , Saprolegniaceae, yeasts, and the higher Basidiomycetes). It was shown by Morton and MacMillan (1954) that this i n a b i l i t y i s due to the pH e f f e c t i n the medium. When these s a l t s were used, they found that the pH of the medium rapidly dropped due to the p r e f e r e n t i a l use of ammonium ion which occurs i n many fungi, and consequently fungal growth was retarded. Although much i s known about the physiology of wood-inhabiting microorganisms, many areas in the fundamentals of th e i r nitrogen metabolism remain to be questionable. The previous study (Ruddick, 1979) has proven that the treatment of wood with ACA increases i t s nitrogen content. However, comparatively l i t t l e i s known about the e f f e c t of treatment with ammoniacal wood preservatives on the c a p a b i l i t y of metabolizing enhanced nitrogenous materials to promote fungal growth. Therefore, more extensive and precise information i s needed about the nature of fungal nitrogen metabolism i n the wood treated with ammoniacal preservatives, under various laboratory and f i e l d t e s ts. 2.9 FUNCTION OF THE SHIGOMETER IN RELATION TO ELECTRICAL PROPERTIES OF INFECTED WOOD The e l e c t r i c a l properties of wood are measured by i t s r e s i s t i v i t y or s p e c i f i c resistance or by i t s r e c i p r o c a l conductivity. The conductivity of a material determines the current that w i l l flow when the material i s placed under a given voltage gradient. Very dry wood i s an excellent elec-t r i c a l insulator, with direct-current r e s i s t i v i t y i n the 17 1 fl order of 3 x 101-' to 3 x 10 ohm-centimeters at room tem-perature (Bannan, 1967). It i s generally known that the e l e c t r i c a l resistance of wood i s lowered by increasing mois-ture content. Es p e c i a l l y below the f i b e r saturation point, the direct-current e l e c t r i c a l resistance of wood decrease rapidly as the moisture content increases. Even traces of water increase the conductivity considerably. The mechanism of e l e c t r i c a l conduction depends on the presence of ions i n the wood. A model for i o n i c conduction was proposed by Lin (1965) to explain the e l e c t r i c a l conduction through the c e l l wall of wood. He pointed out that the number of charges-c a r r i e r s i n wood i s the major factor a f f e c t i n g the conduction mechanism over the moisture content range from 0 to 20%. At higher moisture contents, the degree of d i s s o c i a t i o n of absorbed ions i s s u f f i c i e n t l y high so that the mobility of ions may become the major factor i n determining the e l e c t r i c a l 86 conductivity. Therefore, any change i n ion concentration, d i s t r i b u t i o n , or both, w i l l also change the e l e c t r i c a l conductivity of the wood. Research on the e l e c t r i c a l properties of wood (Brown et a l . , 1963; Lin, 1965 and 1967; Skaar, 1964), and of trees (Fensom, 1959, 1960 and 1963; Levengood, 1970) provided the basic information for the development of a number of r e l a t i v e -l y new techniques to detect the inte r n a l condition, i . e . heartrot, of l i v i n g trees (McGinnes and Shigo, 1975; Shigo and Berry, 1975; Tattar, 1974; Tattar et a l . , 1972 and 1974; Tattar and Saufley, 1973). One such technique involves the measurement of the e l e c t r i c a l resistance of wood to a pulsed current. The o r i g i n a l equipment described by Skutt et: a l . (1972) has been refined s u b s t a n t i a l l y . A f t e r further devel-opment of the meter and the electrodes, the Shigometer (registered trade mark Northeast Electronics Corporation) Model 7950 (Fig.2), described by Shigo and Shigo (1974) and Shigo et a l . (1977), has been widely investigated for use i n u t i l i t y poles (Brudermann, 1977; Inwards and Graham, 1980; Morris et a l . , 1984; Perrin, 1978 and 1979; Shortle et a l . , 1978). The Shigometer i s a meter which measures changes i n the condition of the wood, associated with a change i n e l e c t r i c a l resistance. The method involves the in s e r t i o n of a twisted Figure 2. Battery-powered pulsed-current meter, Shigometer Model 7950, and t w i s t e d w i r e probe. 88 wire probe with bared kinks at the t i p s into a radially-d r i l l e d hole. The degree of resistance to a pulsed e l e c t r i c current i s c l o s e l y governed by the concentration of cations, p a r t i c u l a r l y i n many deciduous woods (Safford et. a l . , 1974; Shigo and Sharon, 1970; Shigo and Shigo, 1974; Shortle and Shigo, 1973; Tattar ejt a l . , 1972) . As wood discolors and decays, the cations (primarily potassium, calcium, manganese, and magnesium) increase and resistance decreases. McGinnes and Shigo (1975) stated more s p e c i f i c a l l y that the Shigometer measures mobile ion concentration within the tree. Tattar and his co-workers (1972 and 1974) have recognized that i n t e r -pretation of Shigometer resistance involves many other factors such as concentration of hydrogen ions (pH), moisture content, s p e c i f i c gravity, and wood structure. In agreement with t h e i r studies, Wilkes and Heather (1982a) found that there was a r e l a t i v e l y weak c o r r e l a t i o n of pulse resistance with pH and with moisture content above the f i b e r saturation point for several hardwood species. However, i t has been reported that the weak p o s i t i v e c o r r e l a t i o n with moisture content i s apparently not consistent among species, since a negative c o r r e l a t i o n was observed for Abies and Sequoia ( P i i r t o and Wilcox, 1978) and for Pinus and Dyera spp. (Thornton, 1979a and b). The e f f e c t s of density and wood structure on pulse resistance have been discussed elsewhere (Skutt e_t a l . , 1972; Wilkes and Heather, 1982a and b), suggesting that above the f i b e r saturation point, an increase i n density could be expected to res u l t i n a decrease i n conductivity. Shigometer resistance may also vary with c e l l wall r e s i s t i v i t y , d r i l l hole c h a r a c t e r i s t i c s , probe geometry, and some aspects of measurement procedure such as the pressure, surface area, and q u a l i t y of electrode contact (Wilson e_t a l . , 1982) . Shigo and his co-workers (McGinnes and Shigo, 1975; Shigo and Berry, 1975; Shigo and Shigo, 1974) have stressed the importance of patterns of resistance rather than absolute values for pr e d i c t i v e purposes. It has been emphasized by Shortle et al.(1978) that the pattern of readings at i n t e r -vals along one hole and not i n d i v i d u a l readings should be taken to indicate the condition of the wood, with a drop of 75% i n the reading in d i c a t i n g decay. Readings of over 500 Ksi were taken as 500 Ka because the o r i g i n a l analogue displays were pegged at 500 Ksa. They also stated that where the high-est reading was over 500 Ysi, a reading of less than 250 Ksz would indicate decay. However, the Shigometer manual (Osmose Wood Preserving Co., 1980) only states the f i r s t (75% drop) of these two c r i t e r i a for predicting decay. Since the introduction of the Shigometer, a number of investigators (Brudermann, 1977; Inwards and Graham, 1980; McGinnes and Shigo, 1975; Morris et a l . , 1984; Perrin, 1978 and 1979; P i i r t o and Wilcox, 1978; Shigo and Berry, 1975; Shortle, 1982; Shortle et a l . , 1978; Thornton, 1979a and b; Thornton et a l . , 1981; Wilkes and Heather, 1982a and b; Wilson et a l . , 1982; Zabel et a l . , 1982) have c r i t i c a l l y examined t h i s instrument as a decay-detecting devise. Not a l l of them adhered to the p r i n c i p l e s of two c r i t e r i a given above, for predicting decay. The l i t e r a t u r e contains con-f l i c t i n g views as to the effectiveness of the Shigometer for detecting d i s c o l o r a t i o n and decay in both standing trees and converted timber. McGinnes and Shigo (1975) claimed that the technique i s capable of detecting ring shake and discoloured heartwood i n black walnut (Juglans nigra L.). Shigo and Berry (1975) con-cluded that the Shigometer detects decay i n Pinus resinosa A i t . Shortle e_t a l . (1978) reportedly worked out p r e d i c t i v e c r i t e r i a which indicated in t e r n a l i n telegraph poles with 93% accuracy. In agreement with t h e i r study, i t has been shown by Inwards and Graham (1980) that the Shigometer could detect the condition of pole i n t e r i o r s at a r e l i a b i l i t y of 76% compared to increment borings. Recently Thornton et a l . (1981) and Zabel et: a l . (1982) also placed a c e r t a i n amount of confidence i n Shigometer methods for detection of i n t e r n a l decay i n poles, but not for soft rot. Despite these p o s i t i v e responses, further assessments of the Shigometer i n both 91 l i v i n g trees ( P i i r t o and Wilcox, 1978; Thornton, 1979a and b; Wilkes and Heather, 1982; Wilson e_t a l . , 1982) and converted timber (Brudermann, 1977; Morris e_t a l . , 1984; Perrin, 1978 and 1979) have a l l been c r i t i c a l . P i i r t o and Wilcox (1978) reported low readings i n both sound and decayed heartwood of Sequoia gigantea L i n d l . with great v a r i a b i l i t y , e s p e c i a l l y in sound wood. From s o i l - b l o c k tests with white- and brown-rot fungi on hardwoods and softwoods, Thornton (1979a and b) concluded that the Shigometer detected the presence but not the severity of decay. As a t o o l for i d e n t i f y i n g s t a i n and early decay in u t i l i t y poles, i t has been reported by Bruder-mann (1977) and Perrin (1978 and 1979) that the re s u l t s of Shigometer measurements are not consistent enough to judge conclusively the effectiveness of t h i s instrument. More recently several researchers (Morris e_t a l . , 1984; Shortle, 1982; Wilkes and Heather, 1982a; Wilson et a l . , 1982) have also demonstrated no p r e d i c t i v e a b i l i t y for patterns of resistance, and suggested that the previously published e v i -dence should be regarded as inconclusive. They a l l found great natural v a r i a t i o n i n e l e c t r i c a l resistance without decay, thus suggesting that the method i s unreliable. In a very recent study of the e f f e c t of moisture content on e l e c t r i c a l resistance, Morris and his co-workers (1984) have concluded that there i s a large difference between the reading of timbers below 38% and above 45% moisture content. These observations correlate c l o s e l y with those reported by P i i r t o and Wilcox (1978), and Thornton (1979a and b), i n that moisture content alone could r e s u l t i n a marked lowering of resistance. However, some groups of investigators (Inwards and Graham, 1980? Shortle, 1982) have repeatedly asserted that variations i n moisture content above the f i b e r satura-tion point do not a f f e c t the e l e c t r i c a l resistance. Another inter e s t i n g area of concern with regard to the effectiveness of the meter for wood in service i s the possible e f f e c t of the presence of ionized material i n the wood on v a r i a b i l i t y i n meter readings. Although the Shigometer has been shown to be e f f e c t i v e in detecting decay in creosote-treated u t i l i t y poles (Shigo and Shigo, 1974), i t i s expected that inorganic materials present i n wood treated with f i r e retardants or waterborne preservative s a l t s could substan-t i a l l y a f f e c t resistance readings in the same manner as the increasing ash content of decaying wood appears to a f f e c t the readings. In this regard, where very l i t t l e work has been done, James (1965) reported that water-soluble, s a l t -type wood preservatives had a substantial e f f e c t on the accuracy of e l e c t r i c moisture meters. 3.0 MATERIALS AND METHODS 3.1 MATERIALS Twelve kerfed and twelve unkerfed ACA-treated poles were selected from those i n s t a l l e d at Westham Island f i e l d test s i t e i n 1977. Based on retention data obtained on each pole p r i o r to i n s t a l l a t i o n , these kerfed and unkerfed poles were categorized into four equal groups: retention greater 3 3 than or equal to 0.60 l b / f t (9.6 kg/m ); greater than or equal to 0.45 (7.2) and less than 0.60 (9.6); greater than or equal to 0.30 (4.8) and less than 0.45 (7.2); and reten-tion less than 0.30 (4.8). In the se l e c t i o n of each pole, r e l a t i v e l y uniform penetration was considered based upon the data a v a i l a b l e . 3.2 METHODS 3.2.1 SAMPLING METHODS 3.2.1.1 BIOASSAY The s o i l around the pole was excavated to f a c i l i t a t e groundline inspection and core sampling. The pole surfaces were examined and probed around the groundline zone. Obser-vations were recorded on the external wood condition, such as major checks, t h e i r width and depth, any detectable decay pockets,etc. 94 Three increment cores, approximately 5 mm i n diameter, were removed from the pole i n the region of the groundline for b i o l o g i c a l investigation. The f i r s t cores were sampled at about 3.0 cm away from the largest major check developed i n non-kerfed poles, or from the kerf of kerfed poles. The second and t h i r d cores were taken at positions of 120° and 240° clockwise apart from the f i r s t , respectively (Figure 3). The cores extended from the surface of the pole to the p i t h . The core borer and extractor were dipped i n 70% alcohol, flamed and allowed to cool down. Using flamed forceps, each sampled core was immediately put into a s t e r l i z e d glass tube with cork caps at both ends (Figures 4a and b). The tube was then wrapped t i g h t l y in a p l a s t i c bag and kept out of di r e c t sunlight. When sampling was completed, the d r i l l e d holes were f i l l e d with copper naphthenate preservative, and then sealed with treated plugs to prevent subsequent i n f e c t i o n . A f t e r returning to the laboratory, the cores were stored i n a cool chamber. Isolations were made within 24 hours of sampling. The d e t a i l s of subdivision for i s o l a t i o n are given i n Section 3,2.3.1. Sampling and examination of removed cores for fungal attack were carried out i n p a r a l l e l i n order to prevent contamination of the cores. Figure 3 . Cross-sectional view of the pole at the groundline, showing the position of three biological cores. 96 F i g u r e 4b. Sample c o r e s i n t h e s t e r i l i z e d g l a s s t u b e s w i t h c o r k c a p s a t b o t h e n d s . 97 3.2.1.2 CHEMICAL ASSAY AND NITROGEN Following the removal of cores for the b i o l o g i c a l investigation, a second set of cores, each approximately 1.3 cm i n diameter was removed adjacent to the s i t e of the second b i o l o g i c a l core from each of the selected poles (Figure 5), for determination of the ACA preservative reten-t i o n and penetration, and also for measurement of the n i t r o -gen content. The core extended from the surface of the pole to the p i t h . The sampled core was cut into four equal pieces for determination of the moisture content of the pole, and each piece was stored i n a glass tube with rubber cap (Figure 6) and returned to the laboratory where i t was weighed and oven-dried at 103 ± 2° for 24 hours. Afte r weighing the oven-dried sample, each piece was sealed within a p l a s t i c bag and stored under r e f r i g e r a t i o n for l a t e r determination of the retention and penetration, and for measurement of the nitrogen content. Upon completion of the core sampling, a l l holes were injected with copper naphthenate, and c a r e f u l l y sealed with a treated plug to prevent subsequent i n f e c t i o n of the pole. 3.2.1.3 SHIGOMETER The experimental work for the evaluation of the Shigo-F i g u r e 5 . S a m p l i n g o f c o r e s f o r t h e s t u d y o f c h e m i c a l d i s t r i b u t i o n and n i t r o g e n c o n t e n t . F i g u r e 6 . S t o r i n g a p i e c e o f t h e c o r e f o r m o i s t u r e measurement. meter was conducted using the same poles as those studied during the fungal i s o l a t i o n and chemical assay. A f t e r the i n i t i a l fungal i s o l a t i o n had been completed, each of the poles was examined using the Shigometer. Based on the information obtained from preliminary i s o l a t i o n of fungi, i . e . the number of fungi present, the Shigometer readings were made near the s i t e of one of the three cores sampled for b i o l o g i c a l assay. 3.2.2 ANALYSIS OF CHEMICAL PENETRATION AND RETENTION To determine preservative penetration, the twenty-four cores co l l e c t e d from the poles were stained with a 0.5% solution (weight/volume) of chrome azurol S prepared accord ing to the AWPA Standard A3-77 (AWPA, 1977), by applying a few narrow streaks along the length of each core. The ACA-treated wood stained blue due to a reaction with the copper and the r a d i a l depth of treatment i n each core was measured Af t e r the measurement of preservative penetration, the stained portion was removed with a sharp knife, thereby eliminating any influence from the chrome azurol S. The remainder of each core was then trimmed to length (the wood between 2 mm and 16 mm from the surface of the pole) as s p e c i f i e d i n the CSA Standard 080.4-M (CSA, 1983c) for the measurement of chemical retention. In addition, two addi-100 t i o n a l portions of each core, adjacent to the f i r s t sampled and immediately beyond the treated zone, were cut to a length i d e n t i c a l to the CSA standard. They were then ground to 20 mesh sawdust. Three-tenths gram of the ground sawdust was thoroughly mixed with 0.2 g of c e l l u l o s e powder which acted as a binding agent and the mixture c a r e f u l l y placed i n a die. The sawdust i n the die was then compressed for 3 minutes at 300 MPa, to produce a p e l l e t 19 mm i n diameter and approxi-mately 1.5 mm thick. The p e l l e t s were analysed using a Tracor Northern energy-dispersive X-ray spectrometer with an americium-241 source, a molybdenum target and a l i t h i u m - d r i f t e d germanium detector. Each p e l l e t was analysed on both sides to check that they were si m i l a r , as i t had been observed that the c e l l u l o s e powder tended to s e t t l e out i n preparing the p e l l e t . The X-ray spectrometer was controlled by an Apple IU microcomputer. A computerized standard c a l i b r a t i o n graph had previously been prepared for various combinations of chromium, copper and arsenic, and included corrections due to inter-element i n t e r -ferences and matrix e f f e c t s . The results were converted from a weight/weight basis to weight/volume basis by multiplying by a conversion factor that includes the sample s p e c i f i c g r a vity. The s p e c i f i c gravity determined for each pole p r i o r to i n s t a l l a t i o n was taken approximately 1 m below the present 101 sampling s i t e . This was deemed more accurate than using a mean species s p e c i f i c gravity. The preservative retentions were expressed on an oxide basis, i . e . CuO and AS2O5, from X-ray spectrometer output. Since 0.3 g of sawdust was used to make a p e l l e t instead of the usual 0.4 g, the r e s u l t was mu l t i p l i e d by 4/3 to obtain the actual retention. 3.2.3 MICROBIOLOGICAL STUDIES 3.2.3.1 ISOLATION PROCEDURES The fungi responsible for decay and staining i n ACA-treated western white spruce have not been previously studied. In general, i t i s known that fast-growing microfungi or bac-t e r i a often overgrow and obscure the decay and staining fungi. Thms a preliminary review of the l i t e r a t u r e (Clubbe and Levy, 1977; Hale and Savory, 1976; Hunt and Cobb, 1971; Smith, 1983) was done to select media favourable towards the growth and i s o l a t i o n of decay fungi. The two s e l e c t i v e media chosen were; 1) malt agar a c i d i f i e d by the addition of 0.5% malic acid (mainly for i n h i b i t i n g b a c t e r i a l growth); 2) benomyl/tetracycline malt agar (for suppressing most microfungi such as Trichoderma and P e n i c i l l i u m spp.). Media formulation and preparations are presented i n Appendix A. 102 Each core provided four zones for the i s o l a t i o n of fungi. The zones selected for investigation were: i) the outer zone of the treated wood (defined as the wood between 2 mm and 7 mm from the surface of the pole); i i ) the un-treated wood immediately adjacent to the outer treated s h e l l ; i i i ) the heartwood region; iv) the p i t h . From each of these selected regions, a 5 mm-long section was taken for culturing and i d e n t i f i c a t i o n of the fungi. Before sectioning for i s o l a t i o n , a whole core was b r i e f l y surface-flamed, and before every cut a kni f e and forceps were dipped i n alcohol, flamed and allowed to cool down. A l l materials needed to make sections, i . e . , glass p e t r i dishes, f i l t e r papers and wood cutting boards, were s t e r i l i z e d . A f t e r a 5 mm-long section of the treated wood was cut and placed on s t e r i l i z e d f i l t e r paper i n a s t e r i l e glass p e t r i dish, a small cutting from the remainder of the treated zone was made and dipped i n a 0.5% solution of chrome azurol S. The penetration of the copper component of the ACA was defined by the dark blue color produced. This procedure was used to determine the l i m i t of the ACA penetration. A f t e r the second 5 mm section was cut, the t h i r d was removed from the heartwood at the mid-point between the second and the pi t h , and the l a s t section was made as near as possible to the p i t h . The core was cut up as shown i n Figure 7. F i g u r e 7. S e c t i o n i n g p r o c e d u r e s o f a b i o l o g i c a l c o r e , p r o v i d i n g f o u r z o n e s f o r t h e i s o l a t i o n o f f u n g i . 104 Each 5 nun section prepared for fungal i s o l a t i o n was then cut into four quarters. Two r e p l i c a t i o n s of two d i f f e r -ent media were prepared for the culturing of fungi (Figure 8). Each quarter was positioned i n the medium so about 3/4 the piece was above the surface (Figure 9). A coding system was developed to re l a t e a l l i s o l a t e s obtained to a pole type (kerfed or non-kerfed), pole number, core location, r a d i a l p o s i t i o n i n a core, and i s o l a t e number of media. The plates were incubated at about 22°C and monitored for several weeks. When fungal growth appeared from the wood samples, they were examined daily, both macroscopically and microscopically. Frequent subculturing onto pure malt agar plates was necessary for the i s o l a t i o n of a single fungus from the frequently occuring b a c t e r i a l contamination or from other fungi. In some cases, as many as f i v e fungi were obtained from the same core p o s i t i o n . Cores from which no fungi could be isol a t e d i n i t i a l l y , were sometimes re-iso l a t e d to confirm absence of fungal i n f e c t i o n . The average observation period for a plate was about eight weeks. The numbers and kinds of colonies were recorded on core data sheets. Isolations of selected fungi were f i r s t made onto pure malt agar plates, and subcultured r e p e t i t i v e l y , as necessary from mycelial margins or streaking to e s t a b l i s h pure cultures. Pure i s o l a t i o n s of selected fungi were then F i g u r e 8. Two r e p l i c a t i o n s o f two d i f f e r e n t t y p e s o f media, r e p r e s e n t i n g e a c h s e c t i o n o f f o u r s e l e c t e d z o n e s . F i g u r e 9. P o s i t i o n i n g a b o u t 3/4 o f e a c h p i e c e above t h e medium s u r f a c e . 106 made into malt agar test tubes and maintained i n a culture bank for l a t e r identification,and study. Approximately one thousand fungi were isolated from the twenty-four poles. When the same fungus appeared i n a core p o s i t i o n on the two s e l e c t i v e media or r e p l i c a t e plates, i t was recorded alphabetically as one i s o l a t e (e.g. Fungus A, B, e t c . ) . Because there was sometimes v a r i a t i o n i n the growth pattern observed on the media (e.g. Phoma sp.), the tentative name of the fungus was modified by a series of numbers (e.g. Fungus A l , A2, e t c . ) . Fungi r e a d i l y i n d e n t i f i a b l e from c u l -t u r a l and microscopic c h a r a c t e r i s t i c s , were recorded only a f t e r several i s o l a t e s had been studied and included i n the culture c o l l e c t i o n . By t h i s method approximately ninety i s o l a t e s were selected f or further study as being representative of the p r i n c i p a l fungal population inhabiting the twenty-four ACA-treated white spruce poles. 3.2.3.2 IDENTIFICATION AND GROUPING OF THE ISOLATES Pure i s o l a t i o n of selected fungi were stored i n a culture bank for subsequent i d e n t i f i c a t i o n and study. A f t e r several months, malt agar plates were prepared to transfer those fungi maintained i n test tubes. Because of t h e i r a b i l -i t y to exhibit d i f f e r e n t forms on d i f f e r e n t media, a l l fungi 107 were sub-cultured onto uniform medium of 1.5% malt extract, 2% agar and d i s t i l l e d water. Sub-cultured p e t r i dishes were put i n p l a s t i c bags and kept at a temperature of 22°C i n a dark growth chamber for approximately two weeks depending on t h e i r growth rates. Heavily sporulating cultures were kept separately to avoid cross-contamination. Macroscopic c u l t u r a l and microscopic c h a r a c t e r i s t i c s were determined for each i s o l a t e . Using dichotomous keys, some of the fungi were i d e n t i f i e d r e a d i l y and the others sorted into taxa of s i m i l a r unknowns. For those unknown fungi, semi-permanent microscope s l i d e s were prepared for each i s o l a t e , using lactophenol as the mounting medium. Some is o l a t e s of the known and unknown fungi were sent to Biosystematics Research I n s t i t u t e of Agriculture Canada (Ottawa), Centraalbureau Voor Schimmelcultures (Baarn, Netherlands), or Commonwealth Mycological I n s t i t u t e (Kew, England), for confirmation or i d e n t i f i c a t i o n . The i d e n t i t i e s of the named fungi were also confirmed by Dr. E.C. S e t l i f f of the Western Laboratory of Forintek Canada Corp. A l l i s o l a t e s were then categorized into three major groups of pole-inhabiting fungi as follows: Basidiomycetes; s o f t - r o t fungi; and microfungi. 108 3.2.4 DETERMINATION OF NITROGEN Following analysis of a portion of the wood sawdust for chemical retention, the remainder of the treated zone near the pole surface and the untreated zone immediately adjacent to the treated s h e l l were analyzed for t h e i r nitrogen con-tents. In addition, two other 1 cm portions from the heart-wood and pi t h of each core were cut and ground to 20 mesh sawdust. The method used was based on that described by Rennie" (1965) for the determination of nitrogen i n woody tis s u e . Approximately 300 mg of oven-dried wood, depending on the a v a i l a b i l i t y of sawdust sample, was weighed into a 100 ml Kjeldahl flask, followed by 40 mg of mercuric oxide and 4 g of potassium sulphate. Five ml of analytical-grade concen-trated sulphuric acid was added and the mixture gently swirled. It was then l e f t to stand for 10 minutes p r i o r to heating to b o i l i n g . The heating schedule depended upon the sample, but i n general heating on an e l e c t r i c rack was maintained for a h a l f hour a f t e r the solution was c l e a r . Care was taken to minimize foaming during the i n i t i a l heating. During heat-ing, the flask was rotated several times to speed c l e a r i n g and to wash down any p a r t i c l e s spattered onto the side of the fl a s k . When the heating was completed, the solut i o n was allowed to cool s l i g h t l y before transferring to a 100 ml 109 volumetric f l a s k . This transfer took place while the solution was s t i l l warm, because otherwise i t could s o l i d i f y r e a d i l y . 5 ml of 2M sodium iodide solution was then added to the d i -gestate which was f i n a l l y d i l u t e d with d i s t i l l e d water up to 100 ml of dil u t e d s o l u t i o n . The diluted solution i n a volumetric flask was placed in cool area overnight a f t e r which the nitrogen content was measured using an Orion ammonia-specific electrode (Orion 95-10) coupled to an Orion Microprocessor ionalyser 901. This instrument was operated i n the analate-addition mode, as described in the Orion operating manuals (1977 and 1978) and the nitrogen concentration i n percentage was read d i r e c t l y from the analyzer display. In summary, the method involved pip e t t i n g 1 ml of the ammonia standard into a 0.4M sodium hydroxide solution and a f t e r allowing the reading to s t a b i -l i z e , adding 10 ml of the diluted digestate to the solution and recording the r e s u l t s . Two replicated readings on each solution were made to provide an average nitrogen content. 3.2.5 SHIGOMETER MEASUREMENTS Measurements for int e r n a l decay were made with a sp e c i a l twisted-wire probe; an abrupt drop i n e l e c t r i c a l resistance supposedly indicates decay. Resistance measurements with the Shigometer on each pole involved d r i l l i n g , from surface to p i t h , a r a d i a l l y oriented hole, 3/32 i n . (2.4 mm) i n diameter, at groundline. The hole was made with 8 i n . (20.3 cm) long d r i l l b i t mounted i n a lightweight battery powered d r i l l . The time taken to d r i l l the hole was usually 40 to 60 seconds with frequent removal of the b i t from the hole to eliminate sawdust. The measurement of resistance was begun a couple of minutes a f t e r d r i l l i n g had been completed. Meter readings were made at 1 cm int e r v a l s , as indicated by painted marks on the probe, to progressively deeper p o s i -tions inside the pole. These measurements established the int e r n a l p r o f i l e of the e l e c t r i c a l resistance. When i n s e r t -ing the twisted-wired probe into a hole, i t was kept horizon-t a l . The procedure followed was based on that described i n the Shigometer method manual. The e l e c t r i c a l resistance readings i n k i l o ohms (kS2) were plotted on scaled sketches of the cores. Deflection percentages were calculated for the lowest each reading from the highest value for a core. The core positions where a de f l e c t i o n percentage was 75 or greater"were recorded being possibly decayed. When the inspection was completed, a l l d r i l l e d holes were f i l l e d with copper naphthenate preservative from a p l a s t i c squeeze b o t t l e , and then c a r e f u l l y sealed with a treated plug to prevent subsequent i n f e c t i o n of the pole. I l l 4.0 RESULTS AND DISCUSSION 4.1 CHEMICAL DISTRIBUTION STUDY The effectiveness of a wood-preservative treatment i n preventing deterioration i s dependent on the degree of tr e a t -ment, as well as the effectiveness of the preservative system i t s e l f . Treatment variables include depth of penetration, l e v e l of chemical retention, and preservative d i s t r i b u t i o n . 4.1.1 PENETRATION Table 11 represents the results of preservative pene-t r a t i o n determined for the ACA-treated spruce poles a f t e r seven years in te s t . The histogram of the average penetra-t i o n values (Figure 10) depicts a s l i g h t right-skewed d i s -t r i b u t i o n with the 50 percent of the observed penetrations f a l l i n g within the range of 1.0 (2.5) to 1.2 i n . (3.0 cm). The s i g n i f i c a n c e of th i s large penetration i s evident when comparing the data obtained in this study with the current ACA-penetration requirements for spruce poles described i n the CSA 080 Wood Preservation Standard, section 080.4. The current standard requires a minimum preservative penetration of 0.50 i n . (13 mm) and 100% sapwood up to a depth of 0.75 i n . (19 mm). Results from this study c l e a r l y indicate that a l l the test poles achieved the CSA-required penetration. These observations correlate c l o s e l y with those reported by Ruddick 112 TABLE 11. Preservative penetration values determined for the ACA-treated spruce poles a f t e r seven years in t e s t . Penetration (in.) Pole Number Min. Max. Ave. K-3-24 1.14 1.17 1.16 K-3-25 1.26 1.39 1.33 K-3-29 1.02 1.20 1.11 N-3-49 0.79 1.03 0.91 K-4- 1 1.33 1.42 1.38 N-4- 2 0.96 1.09 1.03 K-4- 5 1.06 1.12 1.09 K-4- 8 1.27 1.34 1.31 N-4-10 1.45 1.54 1.50 K-4-20 1.14 1.19 1.17 N-4-23 0.91 0.98 0.95 K-4-25 1.04 1.07 1.06 N-4-29 1.17 1.33 1.25 N-4-41 1.05 1.15 1.10 N-5-11 0.97 1.56 1.27 N-5-16 0.88 0.92 0.90 K-5-21 0.93 0.99 0.96 N-5-23 1.08 1.12 1.10 K-5-26 1.01 1.03 1.02 N-5-29 1.34 1.51 1.43 K-5-31 1.04 1.08 1.06 K-5-39 0.99 1.14 1.07 N-5-50 1.04 1.15 1.10 N-5-51 1.06 1.10 1.08 Mean Std. Dev. 1.14 0.19 113 CO LU _ l o OL U . O cr HI C Q 10 8 • • • • • • • • x'X'X'x* %*X*X'X w;Xx";*x*; • • j ^ M E A N (1.14" i i • ) urn i i i i • •ixVx-x-. • V . W . V i tf-XyXv .ix-x-x»;« ;*x*x*x*! IIP *x*x-x* ?**x*:"x*S ••I-X-X-X *-X'X;X; *;*X"X"X' «»x"x"x"5 x^Sx^ 1 — 5$x*:$ ».**x«x*> JL'X'X'X* JSvxS: X x ^ ^ : 1$$$ 0.8 1.0 1.2 1.4 AVERAGE PENETRATION (in.) 1.6 Figure 10. Histogram of average ACA penetration. (1978) , i n t h a t e x c e l l e n t p e n e t r a t i o n w e r e o b t a i n e d i n a l a r g e number o f t r e a t m e n t s o f s p r u c e r o u n d w o o d . R u d d i c k a t t r i b u t e d t h e s a t i s f a c t o r y p e n e t r a t i o n v a l u e s t o t h e c o m b i n a t i o n o f i n c i s i n g a n d ACA t r e a t m e n t . I n d e e d , H o r n and h i s c o - w o r k e r s (1977) h a v e shown t h a t i n c i s i n g s p r u c e p o l e s c l e a r l y e n h a n c e s t h e p e n e t r a t i o n o f w a t e r b o r n e p r e s e r v a t i v e s a p p l i e d b y p r e s s u r e i m p r e g n a t i o n . B a n k s (1973) h a s a l s o r e p o r t e d t h e d e v e l o p m e n t o f a c l o s e -s p a c e d i n c i s i n g p a t t e r n f o r u s e o n s p r u c e l u m b e r t o i m p r o v e t h e p e n e t r a t i o n o f p r e s e r v a t i v e s . C o n s i d e r a b l e e f f o r t h a s b e e n made t o s t u d y t h e e f f e c t o f ammonia o n v a r i o u s c o m p o n e n t s o f t h e wood s u b s t a n c e and some p h y s i c o - c h e m i c a l p r o p e r t i e s o f a m m o n i a - t r e a t e d wood ( B a r i s k a and P o p p e r , 1971 and 1975; B a r i s k a et. a l . , 1 9 69; D a v i d s o n and B a n g a r d t , 1970; Rak, 1 9 7 7 a ) . From t h e s e s t u d i e s , i t c a n be c o n c l u d e d t h a t p e n e t r a t i o n o f ammonia i n t o a l l c o m p o n e n t s o f wood s u b s t a n c e , and i t s a c t i o n o n t h e s t r u c t u r e o f wood a r e i d e n t i f i e d a s f a c t o r s a f f e c t i n g t h e t r e a t a b i l i t y . T h u s , t r e a t m e n t s o f s p r u c e p o l e s w i t h Cu-As p r e s e r v a t i v e s d i s s o l v e d i n a q u e o u s ammonia p r o v i d e d e x c e l l e n t sapwood p e n e t r a t i o n . S u p p o r t i n g e v i d e n c e f o r t h e s e o b s e r v a t i o n s i s p r o v i d e d b y a c o m p a r i s o n o f t h e r e s u l t s o f t h e A C A - t r e a t e d p o l e s w i t h t h o s e r e c o r d e d f o r a s i m i l a r g r o u p o f t h e P C P - t r e a t e d p o l e s ( R u d d i c k , 1 9 7 8 ) . The i n f e r i o r penetration of the l a t t e r was obvious. Rak (1977a) has also shown that the permeability of spruce sapwood i n the r a d i a l d i r e c t i o n to an aqueous ammoniacal solution of inorganic s a l t s was found to be better than that of water. Thus, i t may be concluded from these obser-vations that the use of ACA solutions with the application of i n c i s i n g have both contributed towards the excellent penetrations observed for the ACA-treated spruce poles. 4.1.2 RETENTION The retention of preservative i s one of the most impor-tant factors influencing the extension of the service l i f e of preservative-treated poles. Thus, i n t h i s study, the chemical retention was determined i n three d i f f e r e n t assay zones for each pole, by analyzing the boring that had been used to assess the penetration. The a n a l y t i c a l results are presented i n Table 12. This table also shows the t o t a l chemical content and the r e l a t i v e percentage of the two com-ponents, Cu and As, i n the three a n a l y t i c a l zones, and for comparison the retention values measured p r i o r to i n s t a l l a -t i o n for the f i r s t zone only. The present values determined for zone 1 according to the CSA standard method may be com-pared with those described i n the CSA 080.4 standard of 3 3 0.6 l b . / f t . (9.6 kg/m ) for ACA, on an element oxide basis. TABLE 12. A n a l y s i s o f ACA c h e m i c a l r e t e n t i o n . R e t e n t i o n R e l a t i v e Zone p e r c e n t a g e R e t e n t i o n p r i o r P o l e o f Cu As T o t a l T o t a l t o i n s t a l l a t i o n 1 5 number a n a l y s i s 3 (kg/m 3) (kg/m 3) (kg/m 3) ( l b . / f t . ) Cu As ( l b . / f t . 3 ) K-3-24 1 2 3 5.00 0.80 0.27 3.67 0.27 0.13 8.67 1.07 0.40 0.53 0.07 0.03 58 75 67 42 25 33 0.27 K-3-25 1 2 3 6.27 1.60 0.40 6.00 1.33 0.27 12.27 2.93 0.67 0.77 0.18 0.04 51 55 49 45 60 40 0.62 K-3-29 1 2 3 3.47 0.80 0.13 2.13 0.27 0.13 5.60 1.07 0.26 0.35 0.07 0.01 62 75 50 38 25 50 0.39 N-3-49 1 2 3 4.13 0.80 0.27 2.67 0.40 0.13 6.80 1.20 0.40 0.43 0.08 0.03 61 67 67 39 33 33 0.28 K-4- 1 1 2 3 5.87 2.13 0.27 4.93 1.87 0.40 10.80 4.00 0.67 0.68 0.25 0.04 54 53 40 46 47 60 G.67 K-4- 2 1 2 3 2.40 0.53 0.13 1.60 0.27 0.13 4.00 0.80 0.26 0.25 0.05 0.01 60 67 50 40 33 50 0.39 TABLE 12. (cont.) Retention Relative percentage Retention p r i o r Pole of Cu As Total T o t a l . ^  ,„ o 4. = n I«-,-,^ b a / 3» , , , . 3. . 3, to i n s t a l l a t i o n number a n a l y s i s 0 (kg/mJ) (kg/mJ) (kg/m ) ( l b . / f t . J ) C u A s ( l b . / f t . 3 ) K-4- 5 1 2 3 4.67 1.73 0.27 3.33 1.07 0.27 8.00 2.80 0.54 0.49 0.17 0.03 58 62 50 42 38 50 0.26 K-4- 8 1 2 3 2.40 1.13 0.27 1.73 0.87 0.27 4.13 2.00 0.54 0.25 0.12 0.03 58 57 50 42 43 50 0.54 K-4-10 1 2 3 5.33 1.73 0.40 4.40 1.07 0.13 9.73 2.80 0.53 0.61 0.17 0.03 55 62 75 45 38 25 0.62 K-4-20 1 2 3 4.67 1.60 0.27 2.40 1.20 0.27 6.93 2.80 0.54 0.43 0.17 0.03 65 57 50 35 43 50 0.55 N-4-23 1 2 3 4.53 0.67 0.27 2.40 0.27 0.13 6.93 0.94 0.40 0.43 0.05 0.03 65 71 67 35 29 33 0.35 K-4-25 1 2 3 5.73 0.67 0. 13 4.00 0.40 0.13 9.73 1.07 0.26 0.61 0.07 0.01 59 63 50 41 37 50 0.32 TABLE 12. (cont.) Retention Relative Zone percentage Retention p r i o r Pole of Cu As Total Total to i n s t a l l a t i o n 1 3 number a n a l y s i s 3 (kg/m3) (kg/m3) (kg/m3) ( l b . / f t . 3 ) Cu As ( l b . / f t . 3 ) N-4-29 1 2 3 4.13 0.67 0.27 3.33 0.53 0.27 7.46 1.20 0.54 0.47 0.08 0.03 55 56 50 45 44 50 0.60 N-4-41 1 2 3 6.80 1.33 0.40 6.40 1.07 0.27 13.20 2.40 0.67 0.82 0.15 0.04 52 56 48 44 60 40 0.74 N-5-11 1 2 3 1.87 1.07 0.27 0.67 0.40 0.13 2.54 1.47 0.40 0.16 0.09 0.03 74 73 67 26 27 33 0.33 N-5-16 1 2 3 4.07 0.83 0.27 2.60 0.41 0.13 6.67 1.24 0.40 0.41 0.08 0.03 61 67 67 39 33 33 0.21 K-5-21 1 2 3 5.67 0.53 0.13 3.53 0.27 0.13 9.20 0.80 0.26 0.57 0.05 0.01 62 67 50 38 33 50 0.22 N-5-23 1 2 3 5.67 1.33 0.13 3.80 0.67 0.13 9.47 2.00 0.26 0.59 0.12 0.01 60 67 50 40 33 50 0.46 TABLE 12. (cont.) Zone of Retention Relative Pole Cu As Total Total percentage Retention p r i o r to i n s t a l l a t i o n 1 3 ( l b . / f t . 3 ) number a n a l y s i s 3 (kg/m3) (kg/m3) (kg/m3) ( l b . / f t . 3 ) Cu As K-5-26 1 4.40 3.47 7.87 0.49 56 44 0.33 2 0.67 0.40 1.07 0.07 63 37 3 0.13 0.13 0.26 0.01 50 50 N-5-29 1 4.53 2.80 7.33 0.45 62 38 0.29 2 1.73 0.93 2.67 0.16 65 35 3 0.13 0.27 0.40 0.03 33 67 K-5-31 1 4.27 3.60 7.87 0.49 54 46 0.45 2 2.27 2.13 4.40 0.28 52 48 3 0.40 0.53 0.93 0.05 43 57 K-5-39 1 6.00 5.33 11.33 0.71 53 47 0.70 2 0.80 0.53 1.33 0.08 60 40 3 0.27 0.13 0.40 0.03 67 33 N-5-50 1 3.07 2.13 5.20 0.33 59 41 0.48 2 1.07 0.80 1.87 0.12 57 43 3 0.13 0.27 0.40 0.03 33 67 N-5-51 1 6.13 4.13 10.26 0.64 60 40 0.56 2 1.47 0.93 2.40 0.15 61 39 3 0.40 0.27 0.67 0.04 60 40 TABLE 12. (cont.) Retention Relative Zone percentage Retention p r i o r Pole of Cu As Total Total to installation^* number A n a l y s i s 9 (kg/m3)f (kg/m3) (kg/m3) ( l b . / f t . 3 ) Cu As ( l b . / f t . 3 ) Mean 1 8.06 0.50 0.44 2 1.93 0.12 Std. Dev. 1 2.63 0.16 6 0.16 2 1.01 0.06 a 1: core section from the surface of pole, cut to the length s p e c i f i e d i n CSA standard for the measurement of chemical retention. 2: zone next to the f i r s t section. 3: approximately 1 cm-long section immediately beyond the treated zone. The previous retentions were determined by Ruddick (1978). 3 3 Note: To convert l b . / f t . to kg/m , multiply by 16. 121 As reported by Ruddick (1978), the majority of i n i t i a l retentions i n t h i s white spruce pole study f a i l e d to achieve the l e v e l established by the CSA standard. When the results from t h i s study are compared with those reported by Ruddick, there i s no s i g n i f i c a n t difference at the 90% l e v e l i n the mean retention for the two measurements (Table 13). The mean retention of 0.50 l b . / f t . 3 ( 8 . 0 kg/m3) observed for zone 1 a f t e r several years of testing, i s s l i g h t -3 3 ly greater than the o r i g i n a l value of 0.44 l b . / f t . (7.0 kg/m ). This i s associated with the fact that the samples were removed from the poles at d i f f e r e n t locations ( i . e . for the present study, approximately 3 f t . (0.9 m) above the o r i g i n a l zone, which was 10 f t . (3.0 m) from the butt of the poles. However, i t should be noted that an assay based on a single boring of a pole can furnish only an estimate of chemical retention in the zone and at the point sampled. As shown i n Table 12, i t i s c l e a r that there i s an abrupt gradient i n retention between the f i r s t and second zones. The results indicate that h a l f of the test poles 3 3 have retained less than 0.10 l b . / f t . (1.6 kg/m ) of Cu and As i n the second assay zone. However, i t i s not possible to interpret t h i s poor retention i n white spruce as being s o l e l y due to a blockage of the pathways by which the chemical permeates the sapwood. Rather, low chemical retentions i n TABLE 13. Student t - test between the mean current and previous (prior to i n s t a l l a t i o n ) t o t a l s . Test Present Previous s t a t i s t i c DF Significance Mean 0.50 0.44 t = 1.2559 46 0.2155 Variance 0.027 0.026 F = 1.0361 23,23 0.4665 No. of poles 24 24 Probability ( 1 s t mean) 2 n d) = 0.8872 123 the ACA-treated spruce poles with excellent penetrations can be explained most p l a u s i b l y i n two ways, such as the treating process and the high i n i t i a l moisture content of wood, thus d i l u t i n g the ACA. 4.1.3 DISTRIBUTION OF CHEMICAL COMPONENTS The effectiveness of a preservative treatment may also depend on the d i s t r i b u t i o n of chemical components, p a r t i c u l a r l y i n the waterborne preservative system. The good performance of the s a l t treatments i s p a r t i a l l y attributed to the fact that they are able to penetrate e a s i l y into the c e l l wall of softwoods and are uniformly di s t r i b u t e d i n the wood. From the results shown i n Table 12, an int e r e s t i n g ob-servation has been found i n the r a t i o of copper to arsenic for the retentions i n the f i r s t a n a l y t i c a l zone. When t h i s r a t i o i s plotted against the t o t a l retention (Figure 11), i t is c l e a r l y seen that the r a t i o of copper to arsenic i s near unity at very high t o t a l retention, but increases i n the form of a hyperbolic equation (y = b Q + b^x"*-) as t o t a l retention decreases. From the multiple regression analysis shown i n Table 14, hyperbolic model f i t s the data well at the 99.9% l e v e l , judging by the value of the multiple c o e f f i c i e n t of determination (R 2). The estimates of the model parameters (b Q and b.) are also presented i n the same table, showing Figure 11. Ratio of copper to arsenic versus total retention. TABLE 14. Multiple regression analysis of the r a t i o of copper to arsenic for the retentions in the f i r s t a n a l y t i c a l zone. Source DF SS MS F S i g n i f . Regression 1 1.7406 1.7406 35.135* 0.0000 Error 22 1.0899 0.0495 Total 23 2.8305 Multiple R = 0.78418 R 2 = 0.61495 SE = 0.22258 Variable P a r t i a l C o e f f i c i e n t Std. error t S i g n i f . Constant 0.8835 0.10565 8.3624* 0.0000 1/ t o t a l 0.78418 3.9453 0.66561 5.9275* 0.0000 1c Note: s i g n i f i c a n t at 0.1% l e v e l . 126 the p r e d i c t i o n equation of y = 0.8835 + 3.9453x"x for the t o t a l retention. Recently Ruddick e_t a l . (1981) and Ruddick (1984) have reported the r a t i o of copper and arsenic i n ACA-treated hard-woods grown i n Southeast A s i a . In both studies, the dispro-portionate uptake of these chemical components has been c l e a r l y noted. According to Ruddick (1984), a dispropor-tionate uptake previously observed i n those ACA-treated hard-woods can be explained as being due mainly to the a d a p t a b i l i t y of copper and arsenic to the f i x a t i o n process, suggesting that during treatment of ACA solutions greater amount of copper would be absorbed than arsenic. As a r e s u l t , this would tend to increase the r a t i o of copper to arsenic compared with that present i n the treating s o l u t i o n . However, since the results of t h i s disproportionate uptake were obtained from weathered spruce poles i n exposure tests for several years, low arsenic d i s t r i b u t i o n s where low retentions were observed would also suggest that the arsenic component has been gradually leached out. Where disproportional uptake occurs during the treating process, as reported i n freshly treated hardwoods by Ruddick and his co-workers (1981 and 1984), i t i s necessary to moni-tor the treating solution compositions, and add additional arsenic as required. 127 The importance of these observations l i e s i n the fact that the arsenic content i n the wood should not be allowed to f a l l below a s p e c i f i c l e v e l , because arsenic i s needed to prevent decay by copper-tolerant fungi such as Phialophora spp. Indeed the microbiological investigations to follow indicate that numerous species of the genus Phialophora have been frequently i s o l a t e d near the treated surface of poles. 4.2 BIOLOGICAL STUDY Wood-inhabiting fungi were is o l a t e d from the 24 ACA-treated white spruce poles sampled. As described previously, these fungi were isol a t e d from the four d i f f e r e n t zones of each core. A t o t a l of 71 fungal i s o l a t e s belonging to 17 genera and 4 taxa were i d e n t i f i e d to genus, with 15 of these being i d e n t i f i e d as to species (Table 15). The most f r e -quently i s o l a t e d fungi were Phoma herbarum (24/24, obtained from 24 poles out of 24 sampled), Exophiala jeanselmei (19/24), Oidiodendron spp. (16/24), Acremonium and P e n i c i l l i u m spp. (14/24), Phialophora spp. (13/24), Sclerophoma pythiophila (6/24), and V e r t i c i l l i u m spp. (4/24). Bacteria were also commonly associated with these microfungi i s o l a t e d . However, no Basidiomycetes, regarded as being true decay fungi on the basis of clamp connections, were i s o l a t e d from any ACA-treated 128 TABLE 15. Identity and frequency of fungi isolated from 24 white spruce poles at Westham Island test f i e l d s i t e . I s o lation frequency 1 3 Fungus 9 ! Poles(24) Cores(72) Acremonium spp. 14 20 A_. bu t y r i (Van Bevma) W. Gams 1 1 A. fusidioides (Nicot) W. Gams 1 1 A. k i l i e n s e Grutz 8 11 A. strictum W. Gams 1 2 other species 5 6 Alt e r n a r i a tenuissima (Kunze ex Pers.) Wilts .* 1 1 Aphanocladium album (Preuss) W. Gams 2 3 Asperqillus sp. 1 2 Exophiala ieanselmei (Lanqeron) McGinnis & 19 37 Padhye # Fusidtum sp.' 1 1 Geomyces pannorum (Link) S i q l e r & Carmichael 1 1 Gilmaniella sp. 1 2 Gliocladium sp. 1 1 Oidiodendron spp. 16 28 0. qriseum Robak 10 15 c f . 0 . rhodoqenum Robak 2 2 c f . 0 . tenuissima (Peck) Huqhes 2 2 Cf. 0 . truncatum Barron 1 1 other species 8 13 Pe n i c i l l i u m spp. 14 24 P. canescens Sopp 1 1 unide n t i f i e d species 14 24 TABLE 15. (cont.) Iso l a t i o n frequency Fungus 3 ~ Poles(24) Cores(72) Phialophora spp.* 13 28 P_. americana 3 5 c f . P. f a s t i g i a t a 6 12 cf . P. molorum 2 2 other species 7 15 Phoma herbarum Westend. 24 72 Sclerophoma pythiophila (Corda) Hohnel. 6 11 Scytalidium sp. 1 1 Stemphylium botryosum Wallr. 1 1 V e r t i c i I l i u m spp. 4 6 V. nigrescens Pethybr. 2 2 other species 3 4 unidentified imperfects Taxon 1 1 1 Taxon 2 1 1 Taxon 3 1 1 Taxon 4 1 1 a The species marked with * are pot e n t i a l soft rot fungi on the basis of l i t e r a t u r e (Cserjesi, 1984; Leightley, 1980 and 1981; Nilsson, 1973; Zabel et a l . , 1982). k The t o t a l numbers of poles and cores from which fungi were isolated are placed in parenthesis. 130 spruce poles. An important consideration i n wood protection i s to determine whether or not c e r t a i n fungi are being controlled by a preservative treatment. Such knowledge i s e s s e n t i a l for the s e l e c t i o n of fungi to be used i n future experimental testing and also for the evaluation of a preservative t r e a t -ments. For these reasons, untreated spruce poles i n s t a l l e d at Westham Island were examined for the presence of basidio-carps f r u i t i n g on t h e i r surfaces. Several wood-destroying fungi which have been attacking spruce control poles are l i s t e d i n Table 16. Both white- and brown-rot fungi were observed, but Gloeophyllum saepiarium which causes a brown rot was the most common among the Baasidiomycetes. It i s generally known that G. saepiarium i s a very destructive and resistant ( i . e . to drying and high temperatures) brown-rot fungus, which primarily attacks sapwood but may l a t e r degrade heartwood. As shown i n Table 15, none of the true wood-destroying fungi i d e n t i f i e d from the spruce control poles (see Table 16) have been isolated from the ACA-treated poles. The eight major genera of microfungi were grouped by t h e i r p o s i t i o n i n the cores as to the location and possible time of o r i g i n of fungal inhabitation i n the poles. The data are summarized for the ACA-treated poles i n Table 17. i TABLE 16. Fungi i d e n t i f i e d from basidiocarps on untreated spruce control poles at Westham Island test s i t e (Cserjesi, 1984). 131 Pole number Fungus 1980 SP 8 Poria sp. Stereum sanquinolentum (Alb. & Schw:Fr.) Pouz, Dacryroyces s t i l l a t u s nees:Fr. 1980 15 Gloeophyllum saepiarium (Wolf.:Fr.) Karst. 1980 26 Leucoqyrophana molluscus (Fr.) Pouzar 1980 28 Gloeophyllum saepiarium 1980 31 Crustoderma dryinum (Berk. & Curt.) Parm. 1980 32 Gloeophyllum saepiarium  Crustoderma dryinum Phlebia s u b s e r i a l i s (Bourd. & Galz.) Donk 1980 33 Gloeophyllum saepiarium TABLE 17. Relationship between i s o l a t i o n frequency and core p o s i t i o n for the genera of major fungi isolated from 24 white spruce poles. Frequency of isolations from a core position Core p o s i t i o n 3 Acre-monium Exo-phiala Oidio-dendron Feni-c i l l i u m Phia-lophora Phoma Sclero-phoma V e r t i -c i l lium Total 1 8 35 25 16 13 68 5 4 174 2 3 1 0 3 6 61 2 0 76 3 3 0 1 1 6 57 2 0 70 4 10 2 9 9 11 37 4 2 84 The core position are: 1. the outer zone of the treated wood; 2. the untreated wood immediately adjacent to the outer treated s h e l l ; 3. the heartwood region (outer heartwood); 4. the inner heartwood including p i t h . 133 These data c l e a r l y suggest that most fungi were present i n the outer portion of poles. Since t h i s was treated wood, the presence of these fungi could be attributed to a high tolerance to one or a l l of the chemical components i n the ACA preservative. I f the tolerant fungi were able to attack c e l l u l o s e or l i g n i n , then some decay of the wood could occur. In p a r t i c u l a r , members of the genus Phialophora are known to be copper-tolerant (Francis and Leightley, 1983; Leightley, 1979; Leightley and Armstrong, 1980; Nilsson and Henningssqn, 1978). The presence of fungi i n the treated wood may also have been attributed to lower chemical retention than that s p e c i f i e d i n the CSA standard, possibly with poor preserva-t i v e macro-distribution between wood elements and micro-d i s t r i b u t i o n within c e l l walls. Following colonization by cer t a i n microfungi frequently isolated from the treated wood, a subsequent stage might then be succession by true wood-destroying fungi such as those isolated from tha untreated control poles. Fungi occurred less frequently i n the zone beyond the treated wood to the p i t h . Since t h i s was untreated wood, the presence of fungi might be explained e i t h e r by entry through deep checks penetration the outer treated s h e l l , or by pretreatment invasions that survived the preservative treatment cycle. Although i t i s known that the increased 134 decay incidence i s generally associated with check depth i n service, the time of fungal inception i n most poles i s unclear. As shown i n Table 17, the numerical d i s t r i b u t i o n of c e r t a i n fungi i n the poles would suggest attack from the outside inwards. This could have occurred i n the graveyard test a f t e r i n s t a l l a t i o n . However, i t can also be speculated that these ACA-treated spruce pole invasions by those fungi may have occurred i n the trees, as well as i n the poles p r i o r to treatment, or shortly a f t e r treatment and during storage. Wood-inhabiting fungi may be present i n standing trees and though some e f f o r t s are made to disallow t h e i r presence i n u t i l i t y poles, they can p o t e n t i a l l y be included i n such a product. Since the ACA treatment of the spruce poles, using the Lowry empty-cell process ( i . e . 29 to 51°C), did not i n -volve high temperatures, the presence of a c e r t a i n fungi such as Phoma sp. can be traced to the use of treatment cycles with moderate temperature regimes. This species could remain a l i v e but dormant through a treatment process, yet when the wood met favourable conditions ( i . e . re-wetted), dormancy could be broken and growth r e - i n i t i a t e d . Thus i t can be suggested that i n f e c t i o n with Phoma sp. which show a constant presence i n almost every p o s i t i o n of the core had occurred i n the l i v i n g trees. It i s of i n t e r e s t to note that Exophiala sp., Oidioderadron spp. and P e n i c i l l i u m spp. were associated most frequently with the treated zone (Table 17). Supporting evidence for t h i s association with treated wood i s also provided from fungal i n f e c t i o n i n the p i t h zone of kerfed poles. From the data shown i n Table 18, the presence of these three species was almost exclusively i n the treated p i t h area which received a c e r t a i n chemical retention due to k e r f i n g . This observation can be ascribed p a r t l y to the fact that i n every instance (except Phoma), the p i t h p o s i t i o n through kerf i n g had the maximum number of i s o l a t e s among the three i n t e r n a l , untreated p o s i t i o n s . Very recently several researchers (Drysdale and Hedley, 1984; Holt, 1983; Nilsson, 1982; Nilsson and Daniel, 1983; Nilsson and Holt, 1984) have suggested that b a c t e r i a l degrade i s one of the major types of decay observed i n untreated and preservative-treated wood. They have observed that b a c t e r i a l degrade was usually r e s t r i c t e d to the surface zones of wood products (e.g. p i l e s and posts) and often associated with severe soft rot. The v a r i a b i l i t y i n type and severity of attack has been studied by Nilsson (1984). Based on his observations, i t can be suggested that i n i t i a l b a c t e r i a l attack at the surface zones of poles may have contributed to subsequent colonization by c e r t a i n microfungi. Although b a c t e r i a l degrade has been confirmed i n some wood products, TABLE 18. Frequency of i s o l a t i o n of the major fungi i n the pith zone from both kerfed and non-kerfed poles. Frequency of isolations in the p i t h zone from a pole Pole condition Acre- Exo- Oidio- Peni- Phia- Sclero- V e r t i -monium phiala dendron c i l l i u m lophora Phoma phoma c i l l i u m Kerfed 4 2 5 5 1 9 3 1 Non-kerfed 3 0 1 1 5 8 1 0 Total 7 2 6 6 6 17 4 1 whether or not i t occurs i n ACA-treated poles i s uncertain. This would be an intere s t i n g area for further study, p a r t i c -u l a r l y when inadequate treatment of d i f f i c u l t - t o - t r e a t , non-durable woods, such as spruce, i s encountered. Although no Basidiomycetes were obtained from any ACA-treated spruce poles, i t should be noted that c u l t u r a l detection as conducted i n t h i s study i s a conservative es-timator of decay due to the limited point sampling inherent i n the increment boring procedure. Also because some decay fungi could be rapidl y overrun by bacteria or microfungi even with a s e l e c t i v e culture medium, they may have f a i l e d to be recognized i n the i n i t i a l phases of i s o l a t i o n from cores. However, the associated condition of spruce pole material with numerous microfungi and some s o f t - r o t fungi (e.g. Phialophora spp., A l t e r n a r i a sp., Fusidium sp., and Oidiodendron sp.; see Table 15) could be judged generally to be i n an early stage of development i n a l l of the test poles, based on the frequency of i s o l a t i o n of non-Basidio-myceteous fungi obtained from the cores of each pole com-pared with those decay fungi is o l a t e d from the control poles. This judgement was also based on the sound v i s u a l appearance of most cores sampled and the res u l t s obtained from the Shigometer measurements (see Section 4.4). From the r e s u l t s , i t can also be suggested that the 138 soft rot and microfungi iso l a t e d are more tolerant to ACA preservative than the wood-destroying Basidiomycetes. Some Phialophora species are known to be most tolerant to preserv-at i v e s . It i s recommended that further studies should be conducted to determine the soft rot c a p a b i l i t y of the major fungi isolated from the ACA-treated spruce pole materials. 4.3 NITROGEN ANALYSIS The nitrogen analysis for the ACA-treated white spruce poles a f t e r several years of exposure i n the graveyard test i s presented i n Table 19. Tables 20 and 21 are summaries of the analysis of variance for a s p l i t - p l o t design and Duncan's multiple range test, respectively. The following three observations are v a l i d : 1. There i s no s i g n i f i c a n t difference between the mean residual nitrogen levels due to treatment ( i . e . kerfed vs. non-kerfed) f o r the f i r s t three zones. 2. There i s a s i g n i f i c a n t difference between the mean residual nitrogen levels i n the kerfed vs. non-kerfed poles when the l a s t zone i s included ( s i g -n i f i c a n t at the 99.5% l e v e l ) . There i s also a s i g n i f i c a n t i n t e r a c t i o n between treatments and zones ( s i g n i f i c a n t at the 97.5% l e v e l ) . That i s , the mean nitrogen l e v e l for the kerfed poles i s TABLE 19. Analysis of nitrogen percentage i n ACA-treated white spruce poles. Non-kerfed Kerfed Zone 3 zone a Pole number 1 2 3 4 Pole number N-3-49 0. 163 0.061 0.044 0. 032 K-3-24 0. 210 0.097 0.050 0. 093 N-4- 2 0. 158 0.073 0.052 0. 094 K-3-25 0. 304 0.147 0.092 0. 111 N-4-10 0. 185 0.098 0.089 0. 067 K-3-29 0. 193 0.079 0.061 0. 078 N-4-23 0. 232 0.102 0.099 0. 104 K-4- 1 0. 277 0.121 0.078 0. 141 N-4-29 0. 197 0.095 0.060 0. 107 K-4- 5 0. 213 0.094 0.077 0. 061 N-4-41 0. 275 0.129 0.070 0. 097 K-4- 8 0. 180 0.102 0.058 0. 159* N-5-11 0. 137 0.088 0.046 0. 063 K-4-20 0. 205 0.110 0.061 0. 178* N-5-16 0. 248 0.089 0.046 0. 079 K-4-25 0. 246 0.139 0.080 0. 215* N-5-23 0. 224 0.086 0.054 0. 068 K-5-21 0. 199 0.087 0.072 0. 171* N-5-29 0. 268 0.131 0.103 0. 100 K-5-26 0. 191 0.081 0.059 0. 136* N-5-50 0. 145 0.081 0.060 0. 109 K-5-31 0. 250 0.181 0.102 0. 149 N-5-51 0. 272 0.161 0.119 0. 125 K-5-39 0. 232 0.105 0.060 0. 123 Mean 0.209 0.100 0.070 0.087 Mean 0.225 0.112 0.071 0.135 Std. Dev. 0.051 0.028 0.026 0.026 Std. Dev. 0.038 0.030 0.016 0.044 a 1) treated zone 2) untreated wood immediately adjacent to the outer treated s h e l l 3) heartwood 4) pi t h Note: The values in the pith zone of kerfed poles, marked with *, were measured from sawdust which showed a brown colour. 140 TABLE 20. Analysis of variance of residual nitrogen in the ACA-treated white spruce poles, using s p l i t - p l o t design. Source DF SS MS Tested against 1. Treatment(T) 1 8. 87x 10~ 3 8. 87x 10 2. Pole 22 5. 98 x I O - 2 2. 72x 10 3. Zone(Z) 3 2. 87 x 10' 1 9. 58x 10 4. T x Z 3 7. 19x 10" 3 2. 40 x 10 5. Error 66 4. 24x 10" 2 6. 42x 10 Total 95 4. 06x 10" 1 -3 -3 -2 -3 -4 3.27 4.23 149.10 3.73 *** *** ** 2 5 5 5 Notes: * ** *** Not s i g n i f i c a n t at 5% l e v e l , but at 10% l e v e l S i g n i f i c a n t at 2.5% l e v e l S i g n i f i c a n t at 0.1% l e v e l TABLE 21. Range tests for nitrogen in four d i f f e r e n t zones. Zone Frequency Nitrogen mean Standard Deviation 1 2 3 4 24 24 24 24 0.217 0.106 0.070 0.111 0.045 0.029 0.021 0.043 Duncan's multiple range test, ranges for ©t = 0.05 2.8259 2.9714 3.0668 There are 3 homogeneous subsets (subsets of elements, no pair of which d i f f e r by more than the shortest s i g n i f i c a n t range for a subset of that size) which are l i s t e d as follows: 1 4 2 3 141 s i g n i f i c a n t l y higher than that for the non-kerfed poles i n the p i t h (zone 4) and the r e l a t i o n s h i p between treatments and zones i s d i f f e r e n t f o r the l a s t zone. This i s apparent from Figure 12. 3. There i s a s i g n i f i c a n t difference between the mean nitrogen levels across the zones ( s i g n i f i c a n t at the 99.9% l e v e l ) . The difference i s mostly explained by the difference between the f i r s t zone and the other three zones. In addition to these observations, the nitrogen content just beyond the outer treated s h e l l (zone 2) i s s i g n i f i c a n t l y higher at the 95% l e v e l than either that i n the untreated heartwood, or the background nitrogen l e v e l (0.056%; Ruddick, 1979) established from the analysis of the untreated sapwood borings removed p r i o r to treatment. For the heartwood (zone 3), the nitrogen l e v e l i s comparable with the background nitrogen l e v e l of 0.056%, and also with the percentage n i t r o -gen reported by Young and Guinn (1966) for several coniferous woods, ranging from 0.059% to 0.078%. There are two general trends noted when comparing the nitrogen contents (Table 19) with the chemical retentions (Table 12) i n the same zone of analysis from the same test samples. F i r s t , least squares regression analysis (Table 22) indicates that the amount of nitrogen i s d i r e c t l y proportional 142 HI i -z o o z 111 CD O rr < 0.240 0.220 0.200 0.180 0.160 0.140 0.120 0.100 0.080 0.060 0.040 0.000 < > \ \ \ » \ \\ \ \ w • •• N • - - • K O N - K E R F E D E R F E D w w w \\ : \ • \ \\ t % V 1 1 1 • • • • • • g \ \ \ . \ t 1 1 1 1 i V \ \ \ \ w 1 1 2 Z O N E Figure 12. Mean residual nitrogen content versus zone. v TABLE 22. Least squares regression analysis for the nitrogen content and chemical retention in the f i r s t a n a l y t i c a l zone. Source DF SS MS F S i g n i f . Regression 1 2.6443"2 2.6443~2 29.584* 0.0000 Error 22 1.9665 - 2 8.9385~4 Total 23 4.6107"2 Multiple R = 0.75730 R 2 = 0.57350 SE = 0.02990 Variable P a r t i a l C o e f f i c i e n t Std. error t S i g n i f . Constant 0.11291 0.20059 - 1 5.6287* 0.0000 Retention 0.75730 0.12902"1 0.23720"2 5.4390* 0.0000 Note: s i g n i f i c a n t at 0.1% l e v e l . to that of the copper and arsenic contained i n the wood. This trend c l e a r l y shows that the more chemical retention, the higher the nitrogen percentage (Fig. 13). Second, as described by Ruddick (1979), i t i s generally noted that when in d i v i d u a l cores are examined, both the nitrogen percentage and the copper and arsenic contents decrease as the analyt-i c a l zone moves from the surface to the heartwood where the chemical retention i s assumed to be zero. The trend i s shown by the a n a l y t i c a l results for a l l cores (Table 19), and i s i l l u s t r a t e d g r a p hically for the kerfed and non-kerfed poles using t h e i r mean values of the nitrogen percentage (see F i g . 12) . It had been generally assumed that, as mentioned p r e v i -ously, the ammonia i s l o s t from the wood during the f i x a t i o n of ammonia-based wood preservatives, and exposure of the ACA-treated wood to the action of rainwater markedly reduces the nitrogen enhancement caused by treatment with the ammonia soluti o n . The results from t h i s study.confirm those of Ruddick (1979), namely, that a l l the ammonia present i n ACA preservative has not been lo s t from the wood during the f i x a t i o n process. Some may have reacted with the wood to increase i t s nitrogen content i n both the treated zone and those zones beyond the l i m i t of penetration. Compared with the results obtained by Ruddick (1979), i t can be also 145 0.300T 1 1 1 1 1 r — 0.100 ° 2.0 4.0 6.0 8.0 10.0 12.0 14.0 CHEMICAL RETENTION (kg/m3) Figure 13. Regression line of nitrogen content over chemical retention in the first analytical zone. 146 concluded from the present study that the enhanced nitrogen l e v e l has not been reduced during exposure over prolonged period of several years i n t e s t . Recently, King and his co-workers (1980) have reported that nitrogen compounds migrate to wood from surrounding s o i l , thus increasing i t s t o t a l nitrogen content during s o i l b u r i a l . I f nitrogen transfer i s a function of microbial translocation as postulated by these authors, then the con-siderable nitrogen increases observed i n the treated wood would have been attributed, to a c e r t a i n extent, to microbial biomass which suggests a s i g n i f i c a n t involvement of s a c r i f i -c i a l c olonization by microorganisms. However, i t i s believed that the nitrogen enhancement i n the treated zone has resulted mainly from the ACA treatment alone. There i s no question about the highly increased amount of nitrogen observed i n the treated zone. On the other hand, two possible suggestions could be made i n order to explain s i g n i f i c a n t l y high nitrogen percentage found i n the wood immeidately adjacent to the outer treated s h e l l compared to that i n the heartwood. One i s due to abnormal background leve l s of nitrogen and the other i s through nitrogen f i x a t i o n by fungi and b a c t e r i a . The p o s s i b i l i t y of these observations r e s u l t i n g from abnormal background nitrogen levels can be eliminated on the basis of the nitrogen l e v e l (0.056%) found for the untreated sapwood borings and the range, from 0.059% to 0.078%, of n i -trogen percentage reported by Young and Guinn (1966) for several coniferous trunk woods. It could be summarized that the nitrogen levels adjacent to the treated s h e l l have been enhanced through nitrogen f i x a t i o n by wood-inhabiting bacteria. This might be a rea-sonable suggestion since the results obtained from the micro-b i o l o g i c a l assay show a c e r t a i n evidence of fungal and b a c t e r i a l attack i n the same a n a l y t i c a l zone. However, although the nitrogen enhancement could be p a r t l y attributed to the presence of microorganisms inhabiting the wood, i t could be expected to have only a very small e f f e c t . In a survey of c u l t i v a t e d fungi (Heck, 1929), the percentage of t h e i r dry weight a t t r i b u t a b l e to nitrogen was found to vary between 2.27% i n Coprinus radicans to about 5.13% i n Tricho- derma liqnorum. Thus i t i s concluded that the nitrogen enhancement results mainly from the ACA treatment alone. Supporting evidence for t h i s conclusion i s also provided by the a n a l y t i c a l results obtained i n the p i t h zone, wherein the nitrogen l e v e l for the kerfed i s s i g n i f i c a n t l y higher than that for the non-kerfed. Assuming that an average value of penetration, 1.14 i n . (2.90 cm; Table 11), was obtained through kerfing i n the p i t h zone, i t would then be 148 obvious that a higher nitrogen content, s i m i l a r to that found i n the treated zone, might r e s u l t . This i s confirmed by the l i n e a r r elationship between nitrogen content and chemical retention i n the f i r s t a n a l y t i c a l zone (see F i g . 13). The following two scenarios have been postulated by Ruddick (1979) i n order to explain how and when the enhance-ment of nitrogen l e v e l occurs beyond the treated zone: 1. During the pressure treatment of wood with ACA. 2. During the f i x a t i o n process. When ce r t a i n wood species such as white spruce and Douglas-f i r are pressure-treated with ACA, they darken i n colour during treatment. The cause of t h i s darkening has not been v e r i f i e d yet, but i s presumably due to the use of ammonium hydroxide i n the ACA preservative, since treatment with other waterborne preservatives (e.g. CCA) which also contain copper and arsenic does not give t h i s color reaction. In ACA, as described e a r l i e r , the ammonia i n the solvent reacts with copper arsenate to form a soluble complex. Although t h i s ammonia i s stable i n ammonium hydroxide solution, i t i s r e a d i l y liberated from ammonium hydroxide when the solvent i s removed. Thus, i t i s possible that the ammonia penetrates the wood c e l l s p r i o r to the preservative solution during the pressure treatment of wood with ACA. Based on this fact, Rak (1977) indeed explained the enhanced permeability of 149 spruce wood to ACA compared with CCA. It i s also reasonable to suggest that, during the f i x a t i o n process, some of the ammonia diffuses further into the wood c e l l s . Since a l l the test poles have been at the Westham Island test f i e l d s i t e for several years, i t i s possible that the leaching action of rainwater may have reduced the nitrogen l e v e l . From the results shown i n Table 12, however, thi s i s not so. Supporting evidence i s also provided by the a n a l y t i c a l results reported by Ruddick (1979) for ACA-treated spruce pole sections, showing that the nitrogen l e v e l remained enhanced a f t e r two years of exposure outdoors. Based on these observations, therefore, i t i s also possible to suggest that some of the ammonia has moved further into wood with moisture content above the f i b e r saturation point, down a concentration gradient of ammonia i n the form of ammonium hydroxide or other ammonium solutions. In summary, although the exact cause of this nitrogen enhancement has not been v e r i f i e d yet, the two scenarios seem to best describe the circumstances permitting enhance-ment of nitrogen observed i n the ACA-treated wood. It i s generally known that increasing the nitrogen content of wood frequently increases the rate of decay by wood-destroying fungi. Therefore, the importance of these observations from t h i s study l i e s i n the fact that the addition of nitrogeneous materials to wood may increase i t s s u s c e p t i b i l i t y to decay. The high nitrogen levels at the surface of the poles are u n l i k e l y to be important, since the preservative retentions are also high and would deter fungal attack. However, at other locations farther from the surface where higher nitrogen levels have been observed, the preservative retention i s very much lower than that required to prevent decay. Thus any damage extending to t h i s zone, either by deep checking during subsequent weather-ing or by mechanical damage, could expose wood with a high nitrogen content and low or very l i t t l e preservative retention Although there i s c o n f l i c t i n g evidence as to whether decay can be increased appreciably by a r t i f i c i a l l y adding nitrogen to wood, such situations could lead to decay of the exposed wood, p a r t i c u l a r l y when non-durable spruce wood i s encountered The results from t h i s study show that the wood treated with ACA has been enhanced i n i t s nitrogen l e v e l . However, i t i s s t i l l questionable i n which chemical form th i s enhanced nitrogen i s present i n the wood, and also whether fungi are capable of metabolizing t h i s source of nitrogen to promote t h e i r growth. To date, l i t t l e or no work has been performed concerning these questions. Based on the metabolism of nitrogen described previously, i t may be suggested that t h i s nitrogen i s available i n at least one of three possible forms, 151 i . e . n i t r a t e , n i t r i t e or ammonium ion. As discussed e a r l i e r , some of the ammonia which has not been lo s t from the wood either during the f i x a t i o n process or a f t e r several years of exposure s t i l l remains i n the form of ammonium hydroxide. The n i t r a t e ion (NC>3~) may also have been incorporated into the wood c e l l s as ammonium n i t r a t e , potassium n i t r a t e or calcium n i t r a t e (Cochrane, 1958); i f so, i t then must be reduced to the oxidation l e v e l of ammonia before the nitrogen can be assimilated into organic compounds. I f eithe r of these suggestions are correct, the enrichment of the nitrogen l e v e l i s l i k e l y to promote the growth of some wood-inhabiting microorganisms. Even with frequent i s o l a t i o n s of bacteria and microfungi i n the treated zone, on the other hand, the a l k a l i e f f e c t due to ammonium hydroxide i n association with the high chemical retentions would almost c e r t a i n l y exclude wood-decaying fungi in t h i s zone. It has been assumed that the a l k a l i treatment may destroy thiamine (Dwivedi and Arnold, 1973), which i s e s s e n t i a l for the growth of many wood-decaying fungi, and that the treatment may also increase decay r e s i s t -ance i n wood by reducing the a v a i l a b i l i t y of other micro-nutrients e s s e n t i a l for fungal growth (Baechler, 1959), or by increasing the pH or ammoniacal nitrogen content (Highley, 1973) . Further research i s necessary to show whether the enrichment of the nitrogen l e v e l i n the ACA-treated spruce wood i s favoured p o s i t i v e l y or negatively by numerous fungi inhabiting the wood. If found to be po s i t i v e , further work i s also necessary to confirm that t h i s observation i s i n d i -cative fo ACA-treated wood i n general, and to determine i n which chemical form fungi are capable of metabolizing nitrogen to promote t h e i r growth. 4.4 EVALUATION OF THE SHIGOMETER 4.4.1 MOISTURE MEASUREMENTS As previously described, moisture measurements were taken i n each of the t o t a l 24 spruce poles selected, using the cores sampled for the chemical analysis. These measure-ments served to determine i f additional moisture was required p r i o r to Shigometer measurements and to indicate the extent to which the Shigometer i s responding to moisture rather than to decay (Perrin, 1978). Moisture measurements determined for a l l test poles are shown i n Table 23. The moisture contents of in d i v i d u a l core sections removed from the poles ranged from 24.5% to 61.54%, with an o v e r a l l average of 31,12%. However, moisture levels i n each pole were not normally s u b s t a n t i a l l y d i f f e r e n t between the outer treated surface and p i t h zone, with some exceptions found i n the two kerfed poles (K-4-5 and K-5-26) . TABLE 23. Moisture contents of the ACA-treated spruce test poles. Moisture content 3 Weather Pole condition number 1 2 3 4 Average when sampled K-3-24 28.48 30.74 32.61 31.21 30.81 A K-3-25 29.79 30.28 28.15 30.33 29.64 B K-3-29 28.28 30.94 32.00 33.83 31.26 A N-3-49 33.13 29.71 32.41 28.83 31.02 B K-4- 1 32.14 33.68 32.38 33.65 32.96 A K-4- 2 33.33 30.37 30.91 29.25 30.97 A K-4- 5 30.65 44.54 61.54 58.54 48.82 A K-4- 8 31.65 26.72 28 57 28.83 28.94 B N-4-10 31.78 34.31 30.77 30.16 31.81 B K-4-20 25.60 28.97 28.46 31.71 28.69 B N-4-23 33.65 27.03 27.93 27.96 29.64 C K-4-25 25.93 29.15 25.10 28.07 27.06 A N-4-29 25.40 27.59 30.39 32.14 28.88 A N-4-41 29.41 31.68 28.79 29.30 29.80 B N-5-11 35.65 30.51 29.25 29.63 31.26 B N-5-16 30.77 30.11 27.18 28.83 29.22 A K-5-21 28.49 25.27 32.71 29.00 28.87 A N-5-23 33.87 31.25 30.84 29.41 31.34 E K-5-26 34.15 30.10 32.65 51.58 37.12 D N-5-29 32.20 29.41 30.15 29.70 30.37 E K-5-31 26.95 28.23 27.66 29.31 28.04 A K-5-39 24.59 29.00 30.11 31.78 28.87 E N-5-50 33.90 33.33 31.25 28.36 31.71 A N-5-51 25.71 29.90 31.63 31.40 29.66 A Mean 30.31 30.54 31.40 32.20 31.12 Std.Dew 3.41 3.66 6.73 7.30 4.26 a Each sampled core was cut into four equal sections and numbered from the surface to the p i t h . k A) sunny B) rained the day before C) rained t i l l the morning D) "C" and again during sampling E) cloudy 154 The Shigometer functions only above the f i b e r saturation point of wood tissue, which averages about 27% moisture con-tent (Shigo et_ a l . , 1977) . It has usually been found that, at groundline, the moisture content of poles i n the ground i s above the f i b e r saturation point, and that when micro-organisms are active i n wood, the moisture content i s above the f i b e r saturation point with a few rare exceptions. A l -though there i s some opinion that moisture contents between 25% and 35% are below the c r i t i c a l l i m i t for the Shigometer (Brudermann, 1977), based on instrument s p e c i f i c a t i o n s (Osmose Wood Preserving Co., 1980) and the res u l t s from the measurements of moisture content (see Table 23), the holes d r i l l e d f or the Shigometer measurements were not a d d i t i o n a l l y saturated with deionized water. Support for t h i s decision was also gained from the observation that an abrupt drop i n e l e c t r i c a l resistance readings may be simply due to high moisture content above f i b e r saturation. Very recently, Morris and his co-workers (1984) have reported that there i s a large difference between readings of wood below 38% and above 45% moisture content, suggesting that moisture content alone could res u l t i n a marked lowering of resistance. As shown i n Table 23, i t i s intere s t i n g to note that for poles K-4-5 and K-5-26, r e l a t i v e l y high moisture contents were observed p a r t i c u l a r l y i n the inner zones. Since both poles were kerfed, abnormally high moisture content could be due to the e f f e c t of the kerf through which ground water could move into the inner parts of the poles. As mentioned already, moisture content would be well above the f i b e r saturation point i f microorganisms were active i n wood. Thus, these high moisture contents may mean that there has been extensive decay or degradation by other non-decay microorganisms inside the poles. However, i t should be noted that moisture detection alone would not normally serve to detect decay i n a f i e l d s i t u a t i o n where d i f f e r e n t parts of a pole would be subject to d i f f e r e n t environmental con-d i t i o n s . Therefore, a high degree of s i g n i f i c a n c e cannot be attached to these measurements at t h i s time, as far as decay by active microorganisms i s concerned. For the purposes of t h i s study, knowledge of the absolute wood moisture content i s not e s s e n t i a l . In order to take measurements with the Shigometer, i t i s important to know that the wood moisture content i s above f i b e r sat-uration so that the Shigometer can successfully function. Thus moisture measurements were not taken i n the same hole as Shigometer measurements. On the other hand, at the higher moisture contents observed, i t would be desirable to see whether the moisture content causes the Shigometer to respond to moisture rather than to decay. In t h i s way, r e l a t i v e changes i n Shigometer readings would be compared with some v a l i d i t y to r e l a t i v e changes i n moisture. The e f f e c t of moisture content on e l e c t r i c a l resistance w i l l be discussed i n d e t a i l i n Section 4.4.3. 4.4.2 SHIGOMETER MEASUREMENTS Although the l i t e r a t u r e contains c o n f l i c t i n g views as to the effectiveness of the Shigometer for detecting i n t e r n a l wood condition, t h i s instrument has been used, to a c e r t a i n extent, to detect discoloured and decayed wood i n u t i l i t y poles. Decayed wood i s detected not on the basis of absolute resistance measurements, but on the change of the resistance measurements between sound and decayed zones. Shigometer readings are presented i n Table 24, with d e f l e c t i o n percentage calculated as the difference between the lowest and the highest value f o r a core. Shigo and his co-workers (1977 and 1978) have emphasized that the pattern of readings at inte r v a l s along one hole and not i n d i v i d u a l readings, should be taken to indicate the wood condition. Decay i s indicated with a d e f l e c t i o n of 75% or more i n the readings. The Shigometer manual (Osmose Wood Preserving Co., 1980) also states t h i s c r i t e r i o n for predicting decay. Thus the core positions where the d e f l e c t i o n percentage was 75% or greater were i n i t i a l l y regarded to s u f f e r from decay. T A B L E 2 4 . E l e c t r i c a l r e s i s t a n c e r e a d i n g s ( k a ) w i t h t h e S h i g o m e t e r i n A C A - t r e a t e d s p r u c e p o l e s . D e p t h i n p o l e ( c m ) S e q u e n -P o l e P o l e t i a l D e f l e c -n u m b e r 1 * r a d i u s n u m b e r t i o n c ( % ) 0 . 3 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 K - 3 - 2 4 ( l ) 1 1 . 9 A 4 5 2 7 5 3 6 0 4 6 5 + + + + + + + + 4 6 0 3 9 5 K - 3 - 2 5 ( l ) 1 2 . 4 B 2 8 3 6 0 + + + + + + + + + + + + K - 3 - 2 9 ( 3 ) 1 2 . 8 c 5 0 1 6 0 2 2 0 1 9 5 2 2 0 3 2 0 3 2 0 3 0 0 3 1 0 3 1 0 2 7 5 2 5 0 2 6 0 2 5 0 N - 3 - 4 9 ( l ) 1 3 . 2 D 5 9 2 1 5 2 0 5 2 6 0 3 8 5 + + + + + + + + + K - 4 - 1 ( 1 ) 1 1 . 9 E 1 2 + + + + + + + + + + + 4 5 5 4 4 0 N - 4 - 2 ( 1 ) 1 2 . 1 F 0 + + + + + + + + + + + + + K - 4 - 5 ( 1 ) 1 1 . 5 G 7 8 4 3 0 4 6 0 + + + + + + 1 2 0 1 1 0 1 2 0 1 0 0 K - 4 - 8 ( 3 ) 1 2 . 0 H 3 1 3 4 5 4 4 0 4 6 0 + + + + + + + + + 4 4 0 1 9 - 4 - 1 0 ( 1 ) 1 2 . 4 I 4 6 4 0 5 + + + + + + + + + + 3 3 0 2 7 0 K - 4 - 2 0 ( 3 ) 1 1 . 9 J 3 6 3 2 0 3 6 5 + + + + + + + - + + + 3 7 0 N - 4 - 2 3 ( 2 ) 1 1 . 6 K 3 6 3 2 0 3 7 0 + + + + + + + + + + K - 4 - 2 5 ( 2 ) 1 1 . 8 L 2 8 3 6 0 4 9 0 + • + + + + + + + 4 8 0 4 6 0 N - 4 - 2 9 ( 3 ) 1 2 . 2 M 2 5 3 7 5 4 4 0 + + + + + + + + + + 4 2 0 N - 4 - 4 1 ( 3 ) 1 1 . 9 N 6 4 + + 2 1 0 1 8 0 1 8 0 1 8 5 2 0 0 1 9 0 1 9 5 2 0 0 1 8 5 1 8 0 N - 5 - l l ( l ) 1 0 . 7 0 6 4 2 1 0 2 0 0 2 8 5 + + + + + 1 8 0 2 0 5 4 2 0 3 7 5 N - 5 - 1 6 ( 3 ) 1 0 . 2 P 3 6 3 2 0 4 4 0 + + + + + + + + + K - 5 - 2 l ( 2 ) 1 1 . 6 Q 3 6 3 2 0 + + + + + + + + + + + N - 5 - 2 3 ( 2 ) 1 0 . 9 R 6 4 1 8 0 2 2 0 3 2 0 3 4 0 3 5 0 5 0 0 4 6 0 5 0 0 4 7 0 + K - 5 - 2 6 ( l ) 1 1 . 4 S 7 9 1 0 0 1 5 0 2 0 0 2 2 0 4 0 0 4 4 0 4 8 0 4 3 0 4 6 0 1 8 0 1 0 0 ( r i g h t T 8 8 1 8 0 2 4 0 3 4 0 + 5 0 0 + + + 4 4 0 6 0 2 6 0 ( l e f t ) TABLE 24. (cont.) Depth in pole (cm) Sequen-Pole number** Pole radius t i a l number Deflec-t i o n 0 (%) 0.3 1 2 3 4 5 6 7 8 9 10 11 12 N-5-29(1) 10.9 U 27 365 + + + + + + + + + + + K-5-31(2) 11.4 V 0 + + + + + + + + + + + + K-5-39(l) 11.4 W 62 + 430 480 + + + 425 205 190 190 200 230 (right) X 60 200 350 400 + + + + 330 220 250 350 360 (below) N-5-50(3) 11.1 Y 34 330 400 + + + + + + + + 480 N-5-51(3) 10.7 Z 36 320 + + + + + + + + + 475 a "+" sign indicates resistance reading over 500 ksj. b Numbers in parentheses represent the positions where Shigometer measurements were made. (1) : right of the f i r s t core position made for biological investigation; (2) and (3)t right of the second and third cores, respectively. c Maximum el e c t r i c a l resistance - minimum e l e c t r i c a l resistance x 100: Maximum e l e c t r i c a l resistance To calculate deflection percentage, readings over 500 ka were taken as 500 ka. Note: For two poles (K-5-26 and K-5-39), readings were taken at two different positions. P r i o r to further analysis, the following three basic patterns of e l e c t r i c a l resistance were observed i n the t o t a l of 24 poles where no voids were detected by physical d r i l l -ing and probing: 1. A l l readings < 500 ksi 2. A l l readings > 500 ka 3. Mixed readings In two poles (N-4-2 and K-5-31), a l l resistance readings were above 500 ka the en t i r e length of the hole and there-fore beyond the scale of the meter. In two poles (K-3-29 and K-5-26) , a l l readings were below 500 ks. i n the other twenty poles, some readings were below 500 ka and some above 500 ksa. In numerous studies of a pulsed e l e c t r i c a l current to detect i n t e r n a l decay i n u t i l i t y poles (Brudermann, 1977; Shigo ejt a l . , 1977; Shortle et a l . , 1978; Wilkes and Heather, 1982; Wilson e_t a l . , 1982) , a v i s u a l assessment of the state of decay was also made on the pole cross section at the same locations where Shigometer readings had been taken. Thus the Shigometer readings were subsequently related to the r e s u l t s of the corresponding v i s u a l assessments i n order to be able to evaluate the accuracy and s u i t a b i l i t y of the instrument f o r detection of decay and s t a i n . In t h i s study, however, such v i s u a l assessments could not be made since the 160 poles must remain i n test for further studies. Consequently, the Shigometer readings were compared instead to the results obtained from fungal i s o l a t i o n studies. From the res u l t s of the microbiological study and also observations during d r i l l i n g , i . e . the d i f f i c u l t y of pene-t r a t i o n of the d r i l l , none of the 24 spruce poles seemed to have decay. However, based on the Shigometer readings alone, symptoms of decay were predicted i n a few poles having the following readings of e l e c t r i c a l resistance (Table 25): 1. Some > 500 ka, some < 125 ka (G and T i n Table 24); 2. A l l < 500 ka, lowest less than 75% of highest (S). According to the Shigometer manual, no symptoms of decay are indicated i n wood of most poles having the following readings of resistance (Table 25): 1. A l l > 500 k a (F and V i n Table 24) ; 2. Some > 500 ka, none 250 ka. (A,B, E,H-M, P,Q,U, Y,Z) ; 3. A l l < 500 ka, but lowest not less than 75% of highest (C); 4. Some > 500 ka, some < 250 ka, but none < 125 (D, N,0,R,W,X). Various r e s u l t s from other studies of a pulsed e l e c t r i c current to detect i n t e r n a l decay i n wood generally have i n d i -cated that the patterns of readings which show abrupt de-creases represent decay. The question i s , however, how much TABLE 25. E l e c t r i c a l resistance readings of poles c l a s s i f i e d to indentify those greatest d e f l e c t i o n readings (in d i c a t i v e of deca E l e c t r i c a l resistance readings (kft) No. of poles Low or de f l e c t i o n High moderate d e f l e c t i o n A l l > 500 Some>500, none > 250 14 A l l > 500, but lowest not less than 75% of highest Some > 500, some > 250, but none > 125 Some > 500, some > 125 5(1) K D A l l >500, lowest less than 75% of highest Total 22(1) 2(1) This c l a s s i f i c a t i o n was made on the basis of that of Shortle et a l . (1978). Number i n brackets indicates those poles (K-5-26 and (K-5-39) where two d r i l l holes were measured. 162 of a drop i n the reading i s necessary to indicate decay i n poles that are made from a va r i e t y of tree species and pre-served with a va r i e t y of preservatives. Data from numerous studies give some answers but d e f i n i t e l y not a l l . The Shigometer manual, as mentioned previously, only states that a decrease of 75% or more indicates decay. In addition to thi s c r i t e r i o n , Shortle et a l . ( 1 9 7 8 ) also stated that where the highest reading was over 500 k a , a reading of less than 250 k a would indicate the condition of i n t e r n a l decay. It has been shown i n t h e i r study that wood i n poles having some readings above ' 500 , some below 2 5 0 , and none less than 125 k a was sometimes decayed. Although some of the suspect poles did not appear to have decay, they decided that i f errors were to be made i n using these c r i t e r i a , such errors should be made i n favor of c a l l i n g a sound pole decayed rather than a decayed pole sound. For thi s reason, they have claimed that a l l such poles must be considered decay candi-dates. In t h i s present study, however, those spruce poles (having some readings > 5 0 0 , some < 2 5 0 , but none < 125 k a ) did not appear to have decay. This was based on the information from cultures obtained from borings taken adjacent to the Shigometer measurements, and the lack of ease of penetration of the d r i l l . Thus those f i v e suspect poles are categorized into the group without Shigometer symptoms of wood decay 163 (Table 25). Prom Table 26, which shows three test measure-ments obtained from suspect spruce poles, a close examination of the zones with low resistance reveals that r e l a t i v e l y more fungi were is o l a t e d from approximately matched zones, but none were Basidiomycetes. Therefore, while those sus-pect poles are not decayed (or very l i t t l e decayed due to the presence of soft rotters such as Phialophora spp.), they might have been altered or degraded by the presence of other types of microorganisms (e.g. bacteria and microfungi), re s u l t i n g i n r e l a t i v e l y low readings of e l e c t r i c a l resistance. In a very recent study of the e f f e c t of moisture content on the e l e c t r i c a l resistance of timber, Morris et al.(1984) concluded that the abrupt drop i n Shigometer readings between 38% and 45% moisture content may be due to the formation of a continuous water f i l m between the two electrodes permitting easier ion movement. Thus low resistance readings i n the suspect poles (Table 26) may be attributed just as l i k e l y to v a r i a t i o n i n moisture content rather than decay. The e f f e c t ' of moisture content on e l e c t r i c a l resistance w i l l be further discussed i n the following section. From the results shown i n Table 24, r e l a t i v e l y low readings of e l e c t r i c a l resistance at the surfaces of most poles were observed. Since these surface zones have high preservative retentions with s i g n i f i c a n t l y large amounts of T A B L E 2 6 . E x a m p l e s o f t e s t m e a s u r e m e n t s o b t a i n e d f r o m s e v e n s u s p e c t s p r u c e p o l e s . C a t e g o r y P o l e n u m b e r D e p t h i n p o l e ( c m ) T e s t 0 . 3 1 0 1 1 1 2 M o i s t u r e 1 (%) 3 3 . 1 3 2 9 . 7 1 3 2 . ' 4 1 2 8 . 8 3 N - 3 - 4 9 S h i g o m e t e r ( k ) 2 1 5 2 0 5 2 6 0 3 8 5 + + + + + + + + + N o . o f f u n g i 2 ( 1 ) 2 ( 1 ) 1 1 i s o l a t e d 2 M o i s t u r e 2 9 . 4 1 3 1 . 6 8 2 8 . 7 9 2 9 . 3 0 N - 4 - 4 1 S h i g o m e t e r + + 2 1 0 1 8 0 1 8 0 1 8 5 2 0 0 1 9 0 1 9 5 2 0 0 1 8 5 1 8 0 N o . o f f u n g i 4 ( 1 ) 1 -M o i s t u r e 3 5 . 6 5 3 0 . 5 1 2 9 . 2 5 2 9 . 6 3 S o m e 5 0 0 , N - 5 - 1 1 S h i g o m e t e r 2 1 0 2 0 0 2 8 5 + + + + + 1 8 0 2 0 5 4 2 0 3 7 5 s o m e 2 5 0 , N o . o f f u n g i 4 2 3 2 b u t n o n e 1 2 5 k M o i s t u r e 3 3 . 8 7 3 1 . 2 5 3 0 . 8 4 2 7 . 4 1 N - 5 - 2 3 S h i g o m e t e r 1 8 0 2 2 0 3 2 0 3 4 0 3 5 0 5 0 0 4 6 0 5 0 0 4 7 0 + N o . o f f u n g i 2 1 2 ( 1 ) 2 ( 1 ) M o i s t u r e 2 4 . 5 9 2 9 . 0 0 3 0 . 1 1 3 1 . 7 8 K - 5 - 3 9 S h i g o m e t e r ^ + 4 3 0 4 8 0 + + + 4 2 5 2 0 5 1 7 0 1 9 0 2 0 0 2 3 0 2 0 0 3 5 0 4 0 0 + + + + 3 3 0 2 2 0 2 5 0 3 5 0 3 6 0 N o . o f f u n g i 2 ( 1 ) 1 3 1 T A B L E 2 6 . ( c o n t . ) C a t e g o r y P o l e n u m b e r T e s t 0 . 3 D e p t h i n p o l e ( c m ) 1 0 1 1 1 2 L o w e s t l e s s t h a n 7 5 % o f h i g h e s t , i . e . p o l e s i n i t i a l l y r e g a r d e d a s d e c a y . M o i s t u r e K - 4 - 5 S h i g o m e t e r N o . o f f u n g i M o i s t u r e K - 5 - 2 6 S h i g o m e t e r N o . o f f u n g i 3 0 . 6 5 4 3 0 4 6 0 4 3 4 . 1 5 1 0 0 1 5 0 1 8 0 2 4 0 3 4 4 . 5 4 + + 2(1) 3 0 . 1 0 2 0 0 2 2 0 3 4 0 + 2 4 0 0 • + 6 1 . 5 4 + + 3 2 . 6 5 4 4 0 4 8 0 4 3 0 + + + 1 5 8 . 3 4 1 2 0 1 1 0 5 1 . 6 8 4 6 0 1 8 0 4 4 0 6 0 1 2 0 1 0 0 2 6 0 3 1 0 0 6 ( 1 ) M o i s t u r e c o n t e n t s d e t e r m i n e d i n t h e z o n e s p r o d u c e d b y c u t t i n g c o r e e q u a l l y i n t o f o u r p i e c e s . N u m b e r i n b r a c k e t i n d i c a t e s t h a t a t l e a s t o n e s o f t r o t t i n g f u n g u s w a s i s o l a t e d i n f o u r d i f f e r e n t z o n e s f o r m i c r o b i o l o g i c a l a s s a y w o r k . T h e S h i g o m e t e r m e a s u r e m e n t s o b t a i n e d a t t w o d i f f e r e n t s i t e s . 166 nitrogen,,it i s expected that the presence of ACA preserva-t i v e s a l t s and/or other ionized materials (e.g. NH.4+) could s u b s t a n t i a l l y a f f e c t resistance readings i n the same manner as increasing ash content of decaying wood appears to a f f e c t the readings. Although very l i t t l e work has been done i n this regard, i t i s believed that the effectiveness of the Shigometer for treated wood i n service i s compromised by the possible e f f e c t of ionized materials i n the wood. This i s supported from the observation by James (1965) that water-soluble, salt-type wood preservatives had a substantial e f f e c t on the accuracyyof e l e c t r i c moisture meters. Indeed, Shigo and Shigo (19 74) have reported that the Shigometer seems to be more e f f e c t i v e i n detecting decay i n creosote-treated poles than i n wood treated with f i r e retardants or water-borne preservative s a l t s . The microbiological study showed that a r e l a t i v e l y large number of isola t e s of fungi were present i n the ACA-treated zone to depths of several millimeters r a d i a l l y from the surface of poles. According to Banks and Evans (1984), the degradation of wood surfaces i s due p a r t l y to water-created physico-chemical processes. Coupled with the assumption described by Carey (1982), that increased mois-ture contents also encourage colonization by microorganisms, i t can be suggested that b i o l o g i c a l and physical degradation also contribute to r e l a t i v e l y low readings of e l e c t r i c a l resistance, p a r t i c u l a r l y near the surfaces of most poles. The Shigometer was o r i g i n a l l y designed f o r decay detec-t i o n i n l i v i n g trees, where the wood moisture i s well above the f i b e r saturation point and where there i s most l i k e l y always some sound sapwood present. Since the meter readings are a l l r e l a t i v e values, they have to be related to wood of the same sample that i s s u b s t a n t i a l l y devoid of fungal deter i o r a t i o n and that can be therefore be taken as a reference. This would be possible i n a l i v i n g tree but i n timber i n service, i t i s not possible to d i f f e r e n t i a t e c l e a r l y between apparently sound wood and wood containing s t a i n or any in c i p ient decay. In t h i s study, two factors have been i d e n t i f i e d which made evaluation of the effectiveness of the Shigometer more d i f f i c u l t . F i r s t , since there was no v i s u a l assessment neither any possible decay nor other i n t e r n a l conditions (e.g. voids) could be detected. The results of fungal i s o -lations provided only limited information on i n t e r n a l wood conditions. Second, as described i n the study reported by Shortle est a l . (1978) , the meter measures resistance only to 500 kft, yet many readings exceed t h i s value. Because the true resistance corresponding to readings beyond 500 kn. was not known, the percentage d e f l e c t i o n owing to the lower readings could not be accurately calculated. Thus, i f poles 168 with these c h a r a c t e r i s t i c s make up a large percentage of poles to be inspected, further refinements o f the method or the meter need to be developed. 4 .4 .3 EFFECT OF MOISTURE CONTENT ON THE SHIGOMETER MEASUREMENTS The quest ion of whether such reductions i n e l e c t r i c a l res i s tance as measured i n the suspect spruce poles were due to the presence of decay or simply the v a r i a t i o n i n moisture content can be addressed to the two kerfed poles (K-4-5 and K-5-26) which showed the greatest d e f l e c t i o n i n res is tance readings (Table 24). It i s genera l ly known that changes i n moisture content are gradual i n the v e r t i c a l d i r e c t i o n , but abrupt changes do occur i n poles p a r t i c u l a r l y i n r e l a t i o n to the presence of checks. In kerfed poles , the ker f to the p i t h of a pole normally functions as a major check below groundl ine, permitt ing l o c a l i z e d upward movement of moisture along a continuous c a p i l l a r y above the ground. I f the Shigo-meter probe encounters such a column of wetter wood, the i n t e r p r e t a t i o n of the Shigometer readings could be p a r t i c u -l a r l y ambiguous. Moving the Shigometer probe from wood near the f i b e r sa turat ion point to wood at s i g n i f i c a n t l y higher moisture contents would have caused a drop i n r e s i s t -ance reading. For example. Table 26 shows that as the probe passed through moisture gradients , the Shigometer readings ranged from above 500 to 120 kft for the pole K-4-5, and from 440 to 60 kfl. (or 460 to 100 k«) f o r the pole K-5-26. This i s more than a 75% drop even when taking the maximum as 500 ksi as recommended by Shigo et a l . (1977) . With the previously observed moisture content d i s t r i b u t i o n s i n spruce poles, i t i s concluded that the abrupt drops i n Shigometer readings i n the suspect poles are due to the e f f e c t of va r i a t i o n i n moisture content above the f i b e r saturation point. 170 5.0 CONCLUSIONS 5.1 CHEMICAL STUDY For the ACA-treated spruce poles a f t e r seven years i n test, the penetration conformed to, but the retention was i n s u f f i c i e n t to conform to, the level s established by the CSA standard. Sat i s f a c t o r y penetration values i n refractory spruce wood are attributed to the combination of i n c i s i n g and ACA treatment, while low chemical retentions i n the ACA-treated spruce poles can be ascribed most p l a u s i b l y to the use of an empty-cell process and the impregnation of poles which had been i n s u f f i c i e n t l y dried. The disproportionate uptake of the active ACA chemical components at low retentions, previously described by other researchers, has been confirmed. Since the o r i g i n a l formu-l a t i o n of ACA contained equal amounts of cupric and arsenic oxides, the disproportionate retention of copper to arsenic can be explained as being due mainly to the d i f f e r i n g adapt-a b i l i t y of those components to the f i x a t i o n process, and p a r t l y to possible leaching of arsenic during service. 5.2 BIOLOGICAL STUDY Mic r o b i o l o g i c a l investigations indicated that numerous microfungi were commonly associated with the 24 ACA-treated spruce poles used i n thi s study. The most frequently isolated 171 microfungi were: Phoma herbarum (24 i s o l a t e s obtained from 24 poles sampled), Exophiala jeanselmei (19/24), Oidiodendron spp. (16/24), Acremonium and P e n i c i l l i u m spp. (14/24), Phialo- phora spp. (13/24), Sclerophoma pythiophila (6/24), and V e r t i c i l l i u m spp. (4/24). Bacteria were also commonly found associated with these microfungi. However, i n contrast to the untreated spruce control poles, no true wood-decaying fungi, Basidiomycetes, were isolated from the ACA-treated poles. It can be concluded that the microfungi isolated are more tolerant to ACA pre-servatives than are the wood-destroying Basidiomycetes. 5.3 NITROGEN STUDY The re s u l t s from the nitrogen analysis evidently prove that the treatment of spruce wood with ACA s i g n i f i c a n t l y increases the nitrogen content i n the treated zone and also provides a s i g n i f i c a n t enhancement of nitrogen l e v e l beyond the penetration l i m i t . A l i n e a r r e l a t i o n s h i p exists between nitrogen content and chemical retention i n the f i r s t analyt-i c a l zone. I t i s not c l e a r l y understood whether the enrichment of nitrogen l e v e l due to ACA treatment i n spruce wood i s corre-lated with i t s s u s c e p t i b i l i t y to fungal and b a c t e r i a l colo-n i z a t i o n . 172 5.4 SHIGOMETER STUDY Previously reported e f f e c t s of moisture content v a r i a t i o n within the range 38 to 45% on the Shigometer readings have been confirmed. Since no evidence of decayed wood was found, i t i s not possible to assess the accuracy of the Shigometer for detection of i n t e r n a l decay. However, resistance values observed for two of the poles show changes due to moisture content f l u c t u a t i o n which are s i m i l a r to those reported by previous workers. Hence the p r a c t i c a l a p p l i c a t i on of the Shigometer for detection of i n t e r n a l decay may be limited due to the known v a r i a t i o n i n moisture content of the ground-l i n e region of poles. 5.5 GENERAL Untreated spruce control poles i n the graveyard test had already decayed severely at groundline contact a f t e r seven years of service simulation. Although the ACA-treated spruce poles were infected moderately with numerous micro-fungi and some s o f t - r o t fungi, the complete absence of Basi-diomycetes and the good physical condition of the treated poles i s encouraging enough to warrant promise as an a l t e r -native for t r a d i t i o n a l pole species. With the a v a i l a b i l i t y of white spruce i n large quantities, there should be consid-erable interest i n the p o t e n t i a l of t h i s species for s a t i s -fying some of the future demand i n Canada and making pole supply more f l e x i b l e . I t i s , however, recommended that periodic investigation i n f i e l d test be performed to v e r i f y the u t i l i t y of ACA-treated spruce as pole material. Since the poor retention i n spruce i s a fundamental, f i r s t order problem to overcome, the greatest step to be taken i n preservative treatment i s to improve the t r e a t a b i l i t y of refractory spruce wood, by c a r e f u l drying, improved i n c i s i n g and optimal pressure pro-cesses. From the results to date, i t might be speculated that the CSA s p e c i f i c a t i o n s are too conservative i n that they c a l l for a more retention than actual f i e l d require-ments. However, further work would be required to prove or disprove t h i s . Further studies are also required to provide an i n d i c a t i o n of the extent of checking i n treated poles, and the a b i l i t y of kerfing to prevent the formation of deep checks i n ACA-treated spruce poles. REFERENCES Adolph, F.P. 1976. 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Syracuse, New York. 80 p. APPENDIX A MEDIA FORMULATIONS AND PREPARATIONS 1. A c i d i f i e d Malt Agar (AMA) Malt extract 20 g (2%) Agar 20 g (2%) Malic acid* 5 g (0.5%) D i s t i l l e d water 1000 ml * Acid solution was autoclaved separately and added to 1 l i t r e of the s t e r i l e media a f t e r autoclaving. 2. Benomyl Tetracycline Malt Agar (BTMA) Malt extract 20 g (2%) Agar 20 g (2%) Benomyl 15 ml (7.5 ppm) Tetracycline 10 ml (100 ppm) D i s t i l l e d water 1000 ml * 0.1 g of 50% active ingredient powder i n 100 ml d i s t i l l e d H 2 O was used to y i e l d 0.5/103 for 7.5 ppm. 0.5 g powder to 50 ml d i s t i l l e d H 2 O yielded 10 mg/ml; 10 ml of 10 mg/10 ml t e t r a c y c l i n e stock solution kept i n a r e f r i g e r a t o r were added separately to 1 l i t r e of the s t e r i l e media to y i e l d 100 ppm. Note: A l l these media were autoclaved for 20 minutes at the temperature of 121°C with the pressure of 100 kPa. 

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