The toxicity of softwood leachate in aquatic and terrestrial environments

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Farmer, Kristina L. A.
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Concerns over the potential toxicity of leachate derived from softwood logs in remote storage areas lead Manitoba's Clean Environment Commission to request an investigation into the toxicity of softwood leachate in aquatic and terrestrial environments. This study had two main objectives: (1) To determine if leachates derived from the softwood species Jack Pine (Pinus banksiana) and Black Spruce (Picea mariana) are toxic to aquatic organisms; and (2) To determine the impact of softwood leachate on carbon and nitrogen mineralization and microbial functional diversity in an Eluviated Dystric Brunisol (Ahe horizon) and an Orthic Gray Luvisol (Ae horizon and LFH layer). Softwood leachate was generated by soaking Jack Pine and Black Spruce logs in dechlorinated tap water for up to 60 days. Aquatic toxicity was assessed with rainbow trout (Onchorhynchus mykiss), Daphnia magna, and Microtox (Photobacterium phosphoreum) toxicity tests. Leachate generated by soaking logs for 30 days was used to evaluate the effects on soil microbial processes. Soil functional diversity was assessed via examination of the rate and pattern of substrate usage on Biolog$\sp{\rm TM}$ microtitre plates inoculated with extracts of leachate amended soils. (Abstract shortened by UMI.)