Sediment Gas Ebullition and Flux Studies in Bubbly Creek, South Fork South Branch, Chicago River

摘要

Our study aims to quantify metal contaminant and polycyclic aromatichydrocarbon (PAH) transport from sediments to the water column by advection/diffusionand due to gas ebullition in a highly contaminated urban waterway, Bubbly Creek,Chicago River, Illinois. Nine sites were characterized and benthic flux and gas ebullitionstudies were performed at all sites spanning a wide range of sediment conditions. Principalcomponent and multivariate analysis demonstrates that the mechanisms governingflux of metal contaminants due to gas ebullition may be different from those governingPAH flux. Although both pollutant groups are released to the water column by gas ebullition,ebullition-facilitated heavy metal fluxes correlated with field gas flux and temperature,while PAH transport did not. Ebullition-facilitated organic contaminant transport isthought to occur via organic contaminant partitioning into/onto the gas bubbles fromsediment pore water. However, sediment organic carbon resuspended by gas ebullitionmay also play a more significant role on ebullition-facilitated PAH flux. This is supportedby our finding a lack of strong trends between ebullition-facilitated PAH flux and eitherfield gas flux or temperature and PAH. Ebullition-facilitated metal fluxes were surprisinglylarge compared to advection/diffusion; 18, 2, 5, 20, and 450 mg m~(-2) d~(-1) for Pb, Cr,Ba, Zn, and Fe, respectively. Ebullition-facilitated PAH fluxes were up to 0.3, 7.3, 0.4,0.9, and 5.7 mg m~(-2) d~(-1) for anthracene, fluoranthene, naphthalene, phenanthrene, andpyrene. In contrast, advection/diffusion benthic fluxes were only 1.9, 0.43, 0.62, and 2.2mg m~(-2) d~(-1) for Pb, Ba, Zn, and Fe, respectively. Although T-PAH flux was up to 0.07 mgm~(-2) d~(-1), sediment-to-water fluxes of PAHs at many sites were non-detectable over thebenthic chamber study time period.