Abstract

 The effects of aircraft deicing fluid on aquatic organisms have been previously evaluated using standardized laboratory tests. Few, if any, studies have demonstrated these effects in situ, where environmental conditions are more realistic. Lytle Creek has urban, agricultural, and industrial inputs. An airfreight company operates at the headwaters of Lytle Creek where aircraft deicing fluids leach into the stream. An integrated approach involving in situ and laboratory exposures, macroinvertebrate sampling, habitat evaluation and physiochemical sampling was used. To evaluate whether impairment exists and to distinguish between natural and anthropogenic stressors, assessments occurred during the winter and during the growing seasons. Testing consisted of in situ exposures of two surrogate species in the winter (Daphnia magna and Chironomus tentans) and three surrogate species during the growing season (D. magna, C. tentans, and Hyalella azteca). In situ stressor responses were determined from three key compartments (water column, sediment water interface, and surficial sediment) using caged exposures with survival endpoints. Low survival, £50% occurred in water column exposures during the winter, but not during the growing season. One in situ exposure (0% survival) correlated with high propylene glycol concentration (1000ppm). Habitat quality was excellent, but the macroinvertebrate community received a poor rating. Reproduction and feeding endpoints, as well as sediment toxicity tests were evaluated in the laboratory. Laboratory tests did not predict the toxicity seen in situ. Continual monitoring of upstream airport activities is essential in order to assess the short-term and long-term impact of aircraft deicing fluid.