Polychlorinated Biphenyls In Chinese Air And Surface Soil: Spatial Distribution Characteristics And Thrie Inherent Causes

Polychlorinated biphenyls (PCBs) are a group of persistent organic pollutants (POPs) which can impose a threat to human health and the environment. In this study, congener and homologue profiles of Chinese PCBs production were studied, based on which fingerprint characteristics of Chinese PCBs production were identified; 97 air samples were collected by using passive air samplers and 184 surface soil samples were also concurrently collected; PCBs concentration of the air and soil samples were measured; the spatial distribution of PCB in Chinese air and soil was analyzed; the air-soil exchange of PCBs between Chinese air and soil was investigated; grided Chinese PCBs usage inventories were established; grided Chinese surface soil PCBs residue inventories were established by taking advantage of a significant correlation between PCBs usage and concentration of PCBs in Chinese surface soil.A total of 73 PCBs congeners were detected in Chinese surface soil. Mean concentration ofΣPCBs was 1799 pg/g dw (dry weight), 3352 pg/g dw in urban sites, 1354 pg/g dw in rural sites, and 1345 pg/g dw in background sites. The mainly homologues were lower molecular weight (LMW) PCBs, and 4Cl-PCBs have the highest concentration in soil sample. The higher molecular weight (HMW) PCBs were more enriched in urban soil. 60 PCBs congeners were detected in Chinese air samples. Mean concentration ofΣPCBs was 50 pg/m3 (urban: 350 pg/m3, rural: 230 pg/m3, and background: 77 pg/m3). The mainly homologue is LMW PCBs, and 3Cl-PCBs have the highest concentration in air sample. A highly significant correlation (R = 0.315, P < 0.001) was found inΣPCBs concentration between Chinese air and surface soil samples. The PCBs concentrations in both air and soil at urban sites were higher than those at rural and background sites. It was found that the PCB concentrations in Chinese air and surface soil were in general lower than those in Europe and North America, and there were more HMW PCBs in the air and soil in Europe and North America than those in China.The PCB homologue composition in Chinese air and surface soil was similar to that of the PCBs produced and used in China,which indicates that the PCBs produced and used in China were the major sources of PCBs in Chinese air and surface soil. A further study by using Principal Component Analysis (PCA) was carried out to identify the sources of PABs found in Chinese air and soil. Some sources other than China-produced PCBs were also identified. For example, the sources of PCBs in soil samples in shanghai, chongqing, and kunming and in Southern China air were probably came from imported PCBs products.The fractionation effect was investigated in China, and the phenomenon of the"longitude fractionation effect"was found for the first time in the world POP's research, showing the decrease of total PCB concentrations and the proportion of MMW PCBs and increase of LMW PCBs from east to west in both Chinese rural/background air and soil. A significant correlation between concentrations of PCB congeners/homologues in Chinese surface soil with longitude in 80°-122°E was found, The"urban fractionation effect"was also confirmed in the soil samples around shanghai and in whole China, characterized by high portions of HMW PCBs in urban area and high portions of LMW PCBs in rural and background area., and a strong soil-air correlation for LMW PCBs in the background and rural sites, whereas a strong soil-air correlation for HMW PCBs in the urban sites.Gridded China PCB usage with a 1/6o latitude by 1/4o longitude resolution was established. The dense usage of Chinese PCBs focused on the eastern part of the country with highly developed industry and large population, and was in the region between 96-130°E longitude and 20-50°N latitude.Based on the gridded Chinese usage inventories and a significant correlation between PCBs usage and concentration of PCBs in Chinese surface soil, grided PCBs residue inventories in Chinese surface soil were established, which paved a way for further PCB studies in China.