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Toxicity testing of organic chemicals in groundwater polluted with landfill leachate

A method for assessment of toxicity of nonvolatile organic chemicals contaminants in groundwater polluted with landfill leachate has been evaluated. The biotests utilized were comprosed of an algal growth inhibition test (Selenastrum capricornutum), a daphnia immobilization test (Daphnia magna), and a bacterial genotoxicity test (umuC, Salmonella typhimurium). The feasibility of the selected biotests was investigated for a series of groundwater samples collected along pollution gradients downstreams of two landfills in Jutland, Denmark. Two different approaches were used, direct toxicity testing of whole groundwater samples, and toxicity testing of concentrates obtained by solid‐phase extraction. Direct testing of whole groundwater samples produced toxic responses, but the complex sample matrix masked the toxicity of the organic chemical contaminants of interest. Solid‐phase extraction was used successfully as an on‐site method that eliminated ion toxicity and produced biotest responses that reflected the toxicity of the nonvolatile organic chemical contaminants in the groundwater.