Diurnal Variations of Air-Soil Exchange of Semivolatile Organic Compounds (PAHs, PCBs, OCPs, and PBDEs) in a Central European Receptor Area

Concentrations of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs), and polybrominated diphenyl ethers (PBDEs) in air and soil, their fugacities, and the experimental soil-air partitioning coefficient (KSA) were determined at two background sites in the Gt. Hungarian Plain in August 2013. The concentrations of the semivolatile organic compounds (SOCs) in the soil were not correlated with the organic carbon content but with two indirect parameters of mineralization and aromaticity, suggesting that soil organic matter quality is an important parameter affecting the sorption of SOCs onto soils. Predictions based on the assumption that absorption is the dominant process were in good agreement with the measurements for PAHs, OCPs, and the low chlorinated PCBs. In general, soils were found to be a source of PAHs, high chlorinated PCBs, the majority of OCPs and PBDEs, and a sink for the low chlorinated PCBs and γ-hexachlorocyclohexane. Diurnal variations in the direction of the soil-air exchange were found for two compounds (i.e., pentachlorobenzene and p,p'-dichlorodiphenyldichloroethane), with volatilization during the day and deposition in the night. The concentrations of most SOCs in the near-ground atmosphere were dominated by revolatilization from the soil.