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.