MA1 Large-Scale Investigations of Contaminated Sediments
256 Portland Ballroom
8:00 AM - 12:00 PM, Monday
() National-Scale Trends in Hydrophobic Organic Contaminants in Urban and Reference Lake Sediments, 1970 to 2001.
Van Metre, P1, Mahler, B1, 1 U.S. Geological Survey, Austin, Texas, USA
ABSTRACT- Major shifts in environmental policy, urban land use, population distribution, and vehicle use have occurred in the United States over the past three decades. To assess the effects of these environmental changes on the water quality of streams and lakes, the U.S. Geological Survey collected and analyzed sediment cores for historical trends in pollutants from 41 lakes and reservoirs across the United States. Watershed land use for the sampled lakes ranged from undeveloped forest or grassland (nine sites) to light urban (17 sites) to dense urban (15 sites). Core samples were analyzed for polycyclic aromatic hydrocarbons (PAHs) and chlorinated hydrocarbons (organochlorine pesticides and polychlorinated biphenyls), and contaminant trends from the core profiles were tested for statistical significance from 1970 to the tops of the cores (1996 to 2001). Statistically-significant trends were mostly downward (decreasing concentrations over time) for the chlorinated hydrocarbons and mostly upward for the PAHs. One-half of the lakes, for example, had downward trends in DDE and no lake had an upward trend, whereas one-half of the lakes had upward trends in benzo(a)pyrene and only three had downward trends. Contaminant concentrations were much higher in lakes in dense urban watersheds than in reference lakes and frequently exceeded probable effect concentrations (PEC) from consensus-based sediment quality guidelines. PAHs were twice as likely to exceed the PEC in sediments deposited in the 1990s as they were in sediments deposited from 1965 to 1975, whereas DDT and PCBs were half as likely. The combination of upward trends in PAH concentrations, the strong association of PAHs with urban settings, and the rapid urbanization occurring in the United States suggests that PAHs eventually could surpass chlorinated hydrocarbons in potential toxicity to aquatic biota in urban streams and lakes.
Key words: contaminants, trends, sediment, national