Toxicity of organic chemical pollution in groundwater downgradient of a landfill (Grindsted, Denmark)

The aim of the present study was to describe the occurrence and distributio n of toxicity related to organic chemical contaminants in the leachate plum e downgradient of the Grindsted Landfill (Denmark). A total of 27 groundwat er samples were preconcentrated by solid-phase extraction (SPE) using XAD-2 as the resin material. This treatment effectively eliminated sample matrix toxicity caused by inorganic salts and natural organic compounds and produ ced an aqueous concentrate of the nonvolatile chemical contaminants. The SP E extracts were tested in a battery of standardized short-term aquatic toxi city tests with luminescent bacteria (Vibrio fischeri), algae (Selenastrum capricornutum), and crustaceans (Daphnia magna). Additional genotoxicity te sts were made using the umuC test (Salmonella typhimurium). Biotests with a lgae and luminescent bacteria were the most sensitive tests. On the basis o f results with these two bioassays, it was concluded that SPE extracts of g roundwater collected close to the landfill were toxic. The toxicity decreas ed with the distance from the landfill. At distances greater than 80 m from the border of the landfill, the groundwater toxicity was not significantly different from the background toxicity. SPE extracts were not toxic to Dap hnia (preconcentration factor 10), and no genotoxicity was observed in the umuC test (preconcentration factor up to 120). The overall findings indicat e that a battery of biotests applied on preconcentrated groundwater samples can be a useful tool for toxicity characterization and hazard ranking of g roundwater polluted with complex chemical mixtures, such as landfill leacha tes.