Emissions of polychlorinated biphenyls (PCBs) from sludge drying beds to the atmosphere in Chicago

Ambient air PCB concentrations in the Lake Calumet region in Southeast Chicago have been found to be significantly higher than in nearby non-urban areas. This area is highly industrialized and also contains municipal sludge drying facilities and landfills. In an effort to quantify the importance of the sludge drying facilities to the elevated concentrations, upwind/downwind air samples from the Calumet East sludge drying bed were obtained between April and October 2002. For these samples, the downwind minus upwind (downwind–upwind) concentration varied from 0.33 to 1.27 ng m−3 for non-northeast (NE) direction winds suggesting sludge drying is a source of PCBs to the atmosphere. However, the upwind concentrations were higher than the downwind for winds from the NE of the sampling site suggesting more significant source(s), possibly Lake Calumet or the so called “Cluster site” NE of the sludge drying beds. Flux chamber experiments carried out during the sampling period measured average PCB fluxes of 210 ng m−2 h−1 (range 43–910 ng m−2 h−1) which resulted in an overall flux of 0.005 kg day (d)−1 (∼2 kg yr−1). A developed regression equation between moisture content and sludge concentration estimated higher PCB losses of 0.26 kg d−1 (∼95 kg yr−1). Although these two approaches yielded different values, they both indicate that the emission from the Calumet East sludge drying beds were of minimal importance when compared to the total estimated amount of 2–70 kg d−1 (700–2100 kg yr−1) of PCBs entering the Chicago atmosphere.