Measurement & Flux Modeling of Lake Michigan's Polychlorinated Biphenyl (PCB) Content Near Chicago

Polychlorinated biphenyls (PCBs) exist in various matrices such as air, sediment, serum, soil, tissue, and water and pose a risk of toxic effects in humans and ecosystems; proclivity to bioaccumulate and biomagnify. In addition to being known carcinogens, PCBs also exhibit effects in the immune, reproductive, neurological, and endocrine systems. Dietary exposure and inhalation have been shown to be the primary pathways of human exposure. This study hypothesized that Chicago is an ongoing source of airborne PCBs to Lake Michigan. To address this, the overall strategy employed by this study was to simultaneously sample air and water to measure PCB concentrations and determine the fate of PCBs in southern Lake Michigan.

This study has successfully completed a detailed analysis of the quantity and transport of southern Lake Michiganâ??s PCB content; developing a detailed mathematical flux model in the process. The model predicts the air-water exchange though application of physical-chemical properties of each PCB congener, meteorological data, and environmental sampling. The air-water exchange was modeled, utilizing MATLAB^®R2015a, with combination of the following: Whitmanâ??s two-film resistance model, Deaconâ??s boundary model, three-phase partitioning model, and two parameter Weibull distribution.

Samples were collected, 20 in total, aboard the U.S. Environmental Protection Agencyâ??s R/V Lake Guardian, in September of 2010; 5 km off the coast of Chicago. The environmental samples were processed employing an Accelerated Solvent Extraction (ASE) System 300 and analyzed utilizing gas chromatography with tandem mass spectrometry.

Gaseous ΣPCB concentrations ranged from 0.19 to 1.1 ng m^-3 with an average of 0.75 ± 0.3 ng m^-3. Furthermore, dissolved ΣPCB concentrations ranged from 150 to 170 ng m^-3 with an average of 160 ± 13 ng m^-3. Based on the Aroclor history of the area, the air and water exhibited expected trends: combination of Aroclor 1242, 1248, and 1254. For the entire period of study, the congener specific net flux ranged from -27 to 18 ng m^-2 day^-1, PCB107+124 and PCB11, respectively; net ΣPCB fluxes were determined to range from -320 to 84 ng m^-2 day^-1 with an average of -160 ng m^-2 day^-1. Positive and negative fluxes indicate volatilization and absorption, respectively. Despite the limited study period, this study displays strong evidence that Chicago is a source of PCBs, primarily mid to higher chlorinated congeners, to Lake Michigan. Furthermore, Lake Michigan was found to be a volatilization source of a non-Aroclor congener, PCB11; average net flux of 14 ng m^-2 day^-1.