Polycyclic aromatic hydrocarbons and polychlorinated biphenyls in topsoils of Harbin, China

Levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in 17 topsoil samples collected in and around the city of Harbin, an industrial center in Northeast China for decades, are presented. Total concentrations (ng/g dry weight [dw]) ranged from 17 to 3,260 (mean: 508) for PAHs and 0.30 to 6.17 (mean: 1.63) for PCBs. As expected, large differences of the concentration levels of PAHs and PCBs in topsoil were found among the samples from urban, suburban, and background/rural sites. Total PCB and PAH concentrations were higher in industrialized areas than those at the other sites, with a ratio of up to one order of magnitude, possibly indicating the urban source of these chemicals. The PAH profiles were similar among samples, with high percentages of high molecular weight (HMW) PAHs and domination of four-ring PAHs. Compositions of PCB homologues showed that tri-CBs and tetra-CBs were abundant in all soil samples. There was also a higher abundance of low molecular weight (LMW) PCBs and lower abundance of HMW PCBs at background sites than other areas, indicating the urban fractionation phenomenon. Pyrogenic origins were the dominant PAH sources in surface soil at most urban sites, whereas petrogenic origins were the major PAH sources in surface soil at all the rural and background sites. The TEQ concentrations (pg/g dw) of all four dioxin-like PCBs (CBs 77, 81, 105, and 118) were 0.009 for humans and mammals, 0.005 for fish, and 1.42 for birds. Strong correlations were found between PAH and PCB concentrations and soil organic matter and, also, between PAH and PCB concentrations.