Analysis of polychlorinated biphenyls in concurrently sampled Chinese air and surface soil.

Polychlorinated biphenyl (PCB) concentrations were measured in a concurrent air and surface soil sampling program across China. Passive air samples were collected for approximately 3 months from mid-July to mid-October, 2005 using polyurethane foam (PUF) disk type samplers at 97 sites and surface soil samples were collected in a subset of 51 sites in the same year. As expected, the air concentrations (pg m(-3)) were highest at urban sites (mean of 350 +/- 218) followed by rural (230 +/- 180) and background sites (77 +/- 50). The PCB homologue composition was similar across China, with no distinction among site types, and reflected the profile of Chinese transformer oil with a greater proportion of lower molecular weight (LMW) congeners, particularly the tri-PCBs. This differs from the profile in Chinese soil that was shifted toward the higher molecular weight (HMW) congeners and likely attributed to numerous years of deposition and accumulation in this reservoir. The PCB profile in surface soil also reflects an "urban fractionation effect" with preferential deposition of HMW congeners near sources. The profile of PCBs in Chinese air was shown to be different than reported for Europe and for the Great Lakes Area (GLA) in North America. European and GLA air samples show a distinction between urban and rural/V background sites, with urban sites dominated by tetra- and penta-PCBs, whereas rural and background sites are shifted toward LMW congeners. European and GLA samples also exhibit much higher PCB concentrations at urban sites. This may be attributed to the use of PCBs in building materials in European and North American cities. In China, the difference between urban and rural/background sites is less pronounced. Strong soil-air correlations were found for the LMW PCBs at the background and rural sites, and for the HMW PCBs at the urban sites, a strong evidence of the urban fractionation effect. To our knowledge, this is the first national-scale study in China investigating PCBs in both air and surface soil samples.