Evaluation of background soil and air polychlorinated biphenyl (PCB) concentrations on a hill at the outskirts of a metropolitan city

- PCB TEQ concentrations were 0.17 pg m−3 in air and 21.92 pg g−1 dm in soil.
- Elevated dioxin-like congeners present due to medical waste incineration.
- Soil acted as a source for low molecular weight PCBs.

Air and soil sampling was conducted inside a forested area for 22 months. The sampling location is situated to the north of a metropolitan city. Average atmospheric gas and particle concentrations were found to be 180 and 28 pg m−3 respectively, while that of soil phase was detected to be 3.2 ng g−1 on dry matter, The congener pairs of PCB#4-10 had the highest contribution to each medium. TEQ concentration was 0.10 pg m−3, 0.07 pg m−3, 21.92 pg g−1, for gas, particle and soil phases, respectively. PCB#126 and PCB#169 contributed to over 99% of the entire TEQ concentrations for each medium. Local sources were investigated by conditional probability function (CPF) and soil/air fugacity. Landfilling area and medical waste incinerator, located to the 8 km northeast, contributed to ambient concentrations, especially in terms of dioxin-like congeners. The industrial settlement (called Dilovasi being to the east southeast of 60 km distant) contributed from southeast direction. Further sources were identified by potential source contribution function (PSCF). Sources at close proximity had high contribution. Air mass transportation from Aliaga industrial region (being to the southwest of 300 km distant) moderately contributed to ambient concentrations. Low molecular weight congeners were released from soil body. 5-CBs and 6-CBs were close to equilibrium state between soil/air interfaces. PCB#171 was close to equilibrium and PCB#180 was likely to evaporate from soil, which constitute 7-CBs. PCB#199, representing 8-CBs deposited to soil. 9-CB (PCB#207) was in equilibrium between soil and air phases.

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