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UBC Theses and Dissertations

An evaluation of the state of nitrate/nitrogen contamination of the Abbotsford-Sumas acquifer Ryan, Patrick J.


This thesis concerns groundwater quality with a detailed study of the Abbotsford-Sumas Aquifer and the high nitrate-nitrogen values that have been occurring for the past 20 or so years. Groundwater is becoming an increasingly scarce resource, both in terms of quantity and quality, worldwide. Aquifers are generally poorly understood, dynamic and are an integral part of the hydrological cycle. Aquifer contamination by land use activities threatens their utility as potable sources of water. The literature suggests that one useful measure of the effects of land use on water contamination is nitrate-nitrogen. This substance may be traced to such activities as agricultural practices and septic systems, two major concerns in the area above the Abbotsford-Sumas Aquifer in southwestern British Columbia. The Abbotsford-Sumas Aquifer was examined in detail with a review of the history, geology, hydrogeology, stakeholders, groundwater use and the current identified contamination. Based on the hydrogeology and land use of the aquifer, a representative study area was selected as a case study. With a focus on nitrate-nitrogen the principle objectives were: to determine land use effects on groundwater contamination, assess the contributions of various nitrogen sources and assess the overall impact of intensive land use on the groundwater contamination. This was investigated by a temporal land use evaluation, a nitrogen / nitrate balance and a review of water quality changes. The major land use change in the study area over the period 1969 to 1992 has been the increase in land used for raspberry production which now accounts for over half of the study area. The nitrogen balance revealed a large quantity of nitrogen unaccounted for which is potentially available for leaching. The predominate source of this excess nitrogen is attributed to the high levels of poultry manure fertilizer applied to the soils supporting raspberry crops. Calculations of the nitrogen sources suggest over 90 percent of the excess nitrogen comes from this source. This was well above the other nitrogen sources such as mineralisation, aerial deposition, septic systems, corn crops and pasture land. Although a minor overall nitrogen source, septic tanks appeared to have the potential for high local loadings of nitrate-nitrogen. The water quality data showed increases in nitrate-nitrogen concentrations in the groundwater over the last 40 years. Seventy percent of the water samples showed nitrate-nitrogen values above the Canadian Drinking Water Guideline maximum value allowed in drinking water. The data however displayed significant variability.

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