USGS Grant Number: G11AP20211
Year Established: 2011 Start Date: 2011-08-01 End Date: 2014-07-31
Total Federal Funds: $249,949 Total Non-Federal Funds: $298,300
Principal Investigators: Charles Werth, Michael Plewa
Abstract: Particle associated contaminants (PACs) were responsible for fish-consumption advisories for 39 percent of total river mileage and 43 percent of total lake acreage in the United States in 2008 (USEPA, 2009). Results from recent water quality surveys indicate that metal, polychlorinated biphenyl, and DDT concentrations in freshwater sediments have generally decreased since their peak in the mid 1970’s, consistent with their use and regulatory histories. However, total concentrations of polycyclic aromatic hydrocarbons (PAHs) have increased, and generally with increasing urbanization. Results from a number of our recent studies indicate that coal-tar pavement sealcoat is a dominant source of PAHs in urban lakes. Coal-tar sealcoat contains 5% PAHs by weight and is widely used in the United States; e.g., 18 million L is applied annually in Texas alone corresponding to about 30% of all parking lots. The overall goal of this study is to determine the fate and toxicity of PAHs associated with coal tar particles in urban lake sediments. We hypothesize that lower molecular weight PAHs are released from coal-tar particles soon after deposition as lake sediments (weeks to months), and taken up by more strongly sorbing black carbon, and that higher molecular weight PAHs are only lost to black carbon over much longer time scales (i.e. years) as phenolic and heterocyclic compounds that comprise coal tar degrade. As a result, we also hypothesize that PAHs are preserved in lake sediments, but that they become more tightly bound and less toxic over time. We propose to use the Lake in the Hills watershed (in the Chicago suburbs) as an urban “laboratory” to test our hypotheses. Land use in this watershed has transformed from predominantly agriculture to greater than 90% urban over the last 20 years, and this has corresponded to a 10-fold increase in lake sediment PAH concentrations. Sealcoated pavement in the watershed constitutes 4% of the total area, 42% of the parking lot area, and 89% of the driveway area. We propose to take lake sediment cores from Lake in the Hills. Two cores will be sectioned and used to determine PAH and coal tar particle mass loadings with depth. Material from these cores will also be used to determine the equilibrium distribution and exchange rate of PAHs among different carbonaceous materials including coal tar. Six cores will be spiked with four different carbonaceous material particle types loaded with deuterated PAHs. The carbonaceous materials will be asphalt, coal tar, char, and soot; these were found to control PAH loadings in an urban lake in Fort Worth, Texas. After spiking, the cores will be placed back in the lake sediments and allowed to age for 6 months, 1 year, and 2 years. After each of these time periods, two cores will be taken and used to determine PAH and carbonaceous material mass loadings with depth, and the concentration of PAHs on specific types of carbonaceous materials. Because structurally similar but different PAHs will initially be loaded into each of the spiked carbonaceous materials, these measurements will show to what extent each type of carbonaceous material lost PAHs, and to what extent PAHs redistributed among the different carbonaceous material types. PAHs that desorb into pore water and total extract PAHs will be subject to geno- and cyto-toxicity tests. Toxicity results will be compared to chemical results to determine if total PAH losses or PAH redistribution among carbonaceous material particles affects toxicity as hypothesized.