Passive air sampling for polychlorinated biphenyls in the Philadelphia metropolitan area.

Passive air samplers were deployed at 32 sites across the Philadelphia metropolitan area to investigate the types and locations of atmospheric polychlorinated biphenyl (PCB) sources in a typical U.S. city. PCB levels varied over a factor of approximately 30 and displayed strong spatial gradients. Two regions of high PCB levels were observed, one in the center of Philadelphia and another on the city's south side. These two maxima are thought to represent urban vs. industrial sources. A Gaussian diffusion model was found to adequately describe the spatial gradients for the primary (center city) concentration maximum. Higher molecular weight PCBs were more prevalent at the more urban locations, in agreement with other urban gradient studies and suggesting that re-emission (i.e., secondary sources) of PCBs are important Positive matrix factorization analysis resolved two factors that are interpreted to represent light Aroclors and a heavier industrial source concentrated atthe secondary maximum on the city's south side. The results generally corroborate an earlier study in which data from the New Jersey Atmospheric Deposition Network site in Camden, NJ, was used to investigate source types and locations. Additionally, the non-Aroclor congener PCB 11 (3,3'-dichlorobiphenyl) was detected in all samples.