Measurement & Flux Modeling of Lake Michigan's Polychlorinated Biphenyl (PCB) Content Near Chicago
AIChE Annual Meeting
Monday, November 14, 2016 - 10:00am to 12:30pm
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 MATLABÂ®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 Î£PCB concentrations ranged from 0.19 to 1.1 ng m-3 with an average of 0.75 Â± 0.3 ng m-3. Furthermore, dissolved Î£PCB concentrations ranged from 150 to 170 ng m-3 with an average of 160 Â± 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 Î£PCB 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.