No abstract

Nitrate is one of the most commonly detected contaminants found in aquatic systems with other pesticides such as atrazine. The current study examined potential combined effects of nitrate and atrazine on adults of the freshwater amphipod Hyalella azteca, using survival and precopulatory guarding behavior as toxic endpoints. Although significant differences in acute toxicity with nitrate alone and in binary combination with atrazine (200 µg/L) in water-only tests were not consistently observed for each time point, potential biologically relevant trends in the data were observed. Posttest growth and behavioral observations (10-day period) conducted after 96-hour exposure suggested that atrazine and nitrate at these concentrations did not result in delayed effects on H. azteca. However, when test conditions were modified from standard toxicity tests by feeding amphipods, nitrate was found to be more toxic, with a reduction in median lethal concentration (LC50) values of approximately 80%. We also demonstrated that nitrate exhibits a dose-response effect on precopulatory guarding behavior of H. azteca, suggesting that reproductive effects may occur at environmentally relevant concentrations.

Oil spills create unique challenges in regards to the assessment of potential exposures to response workers and members of the public, and in assessing the potential environmental impacts of the release. This presentation discusses the use of breathing zone air samples taken above or in the direct vicinity of freshly released product for the establishment of air (personal and ambient) monitoring strategies. Air samples collected directly in the vicinity of freshly released and weathered product can provide critical information regarding the potential for work-site and off-site community exposure monitoring. The relative levels in air of volatile organics emitted from fresh product can be used to focus analytical sampling efforts on those constituents with the greatest potential for exceeding occupational exposure levels and community exposure guidelines, and which have the potential for impacts on human health. Finally, analytical methods for evaluation of air samples should include reporting of tentatively identified compounds (TICs), as the primary constituents of crude oil are often not included as target analytes in commonly-employed analytical methods and will likely vary based on the type of crude oil released.