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UBC Theses and Dissertations

A heuristic system for environmental risk assessment of mercury from gold mining operations Veiga, Marcello M.


Mercury pollution in the Amazon region represents today one of the most serious environmental issues faced by mankind. Quantities from 70 to 170 tonnes of mercury are discharged into the Amazonian environment annually from gold mining operations conducted by so-called “garjmpeiros” or informal miners. The transformations of mercury in the environment are not well understood by non-technical people and neither are methods to alleviate dangerous situations. As the issue is fraught with complex and vague concepts, Expert Systems can play an important role in transferring heuristic knowledge to non-technical people interacting directly with miners. A synergy is obtained if these people are also made aware of the toxic effects of mercury, methods to minimize emissions and of methods to diagnose critical situations. This work shows how an Expert System, HgEx, was developed to assist non-expert people to obtain a preliminary Hg bioaccumulation risk assessment without conducting a complex monitoring program. Fuzzy Logic techniques and a new weighted inference method allow program users to input imprecise field observations and still obtain conclusions about pollution extent and bioaccumulation possibilities. Because of its simplicity and ability to combine complex technical issues together with heuristic operational observations, the technology of an Expert System can play an important role in providing a rapid risk assessment for non-technical people. An initial picture of the contamination potential of a region or mining site together with measures to minimize mercury emissions and remedy critical situations are the main results presented to users who might include health workers, environmental and mining inspectors, engineers, biologists, etc. This work also stresses the importance of organic-rich environments in Hg-complex formation and points out the importance of vegetation fires as an additional source of Hg not previously considered in the Amazon. The tutorial part of the system can give guidelines for mercury-monitoring field work as well as an overview on the mercury biogeochemical cycle.

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