Temporal and spatial distribution and source identification of organic pollutants in Lake Calumet area.

摘要

Nine sediment core samples including five deep cores (42–51 cm) and four short cores (8–12 cm) were collected from the Lake Calumet area located about 15 miles southeast of downtown Chicago. Sampling locations include the main lake body, surrounding ponds and the Calumet River.; The deep cores were sectioned into ten to twelve segments and dated by Pb-210 radiological technique to construct the chronological profile for each core. Loss on ignition (LOI), water content, sediment density, and grain size were determined for physical characteristics of sediments.; The concentrations of seventeen polycyclic aromatic hydrocarbon (PAHs) and nineteen polychlorinated biphenyls (PCBs) in each sediment segment were measured. The samples were Soxhlet extracted, concentrated using a K-D evaporator, passed through a silica gel column, then analyzed by HP-5890 gas chromatograph (GC) with a DB-5 capillary column. A flame ionization detector (FID) was used for PAHs analysis. PCBs were detected by an electron capture detector (ECD). The identities of PAHs were confirmed by HP-6890/5973 GC/MS.; The concentration of PAHs was weakly correlated with LOI (r2 = 0.3648), while that of PCBs was not (r2 = 0.0568). PAHs and PCBs showed little correlation with grain size distribution. PAHs were weakly correlated with PCBs with r2 = 0.2580. The Pullman Creek running along the freeway I-90/94 was identified as the most significant source of PAHs to the lake.; The maximum fluxes of PAHs and PCBs occurred during the 1950s to 1980s. The effect of the PCBs ban during the 1970s was not conspicuous, while PAH fluxes to the lake area were reduced recently. Isomer ratios and molecular mass profiles of PAHs confirmed the combustion origin of the PAHs in the lake area. The petrogenic contribution of PAHs was not identified.; A chemical mass balance model (EPA-CMB8.2) was applied to apportion two important PAHs sources with seven high molecular weight PAHs being used as the fitting species. Traffic related sources were responsible for thirty-six percent of PAHs. Coal combustion related sources accounted for the remaining sixty-four percent. The results of PAHs source apportionment using EPA-CMB8.2 were confirmed by another CMB model developed at the University of Wisconsin-Milwaukee, factor analyses, and model predictability to nonfitting PAH species.