Seasonal variations of polychlorinated biphenyls in surface soils and air-soil exchange in Bursa, Turkey

This study investigates the seasonality of polychlorinated biphenyl (PCB) levels in soils of Bursa city located in northwestern Turkey. Forty-three soil samples were collected each season during a 1-year period. Air and soil samples were collected concurrently 3 or 3 times in a month during a 1-year monitoring period from 2 of the 43 locations. The samples were analyzed for 83 PCB congeners. Flux levels, fugacity fraction (ff) levels, and net flux levels of PCB congeners were calculated for 2 specific regions. The influence of humic substance and total organic carbon content of soil on PCB levels was also examined. The mean concentrations of the total PCBs were 1275 ± 1120, 4075 ± 2740, 2185 ± 2010, and 1150 ± 1540 pg/g dry weight in spring, summer, autumn, and winter seasons, respectively. Four- and 5- CBs were the most abundant homologue groups in soils, and their contribution to the total was 55 %. PCB-74, followed by PCB-153, was the dominant congener. Air and soil PCB levels increased together with the soil temperature suggesting the influence of instantaneous air-soil exchange toward the equilibrium conditions. Flux and ff levels also showed a positive significant correlation with soil temperature. Flux levels were mostly positive for the 2 regions indicating volatilization from soil to air.