soil-air partitioning of polychlorinated biphenyls and total dichloro-diphenyl-trichloroethanes

Soil-air partitioning is an important diffusive process that affects the environmental fate of organic compounds and human health. In this review, factors affecting the soil-air partitioning of polychlorinated biphenyls (PCBs) and total dichloro-diphenyl-trichloroethanes (p,p′- and o,p′- isomers of DDT, DDD, and DDE) are discussed. Hydrophobicity is an important factor that influences soil-air partition coefficients (K SA), and its effect can be explained through enthalpy of phase change for soil-air partitioning transfer (ΔH SA). For more hydrophobic compounds, a sharp increase in the K SA of PCBs and organochlorines can be seen in the early aging period. During the aging period, the temperature has a significant effect on the more hydrophobic organic compounds. The content and properties of soil organic matter influence the K SA of the target compounds. Generally, K SA decreases with increasing relative humidity in soils. The linear trend between K SA and temperature (T) changes at 0 °C. Freezing the air or soil in experiments would change the research results. On the basis of factors influencing soil-air partitioning, a multipleparameter (T, organic carbon fraction (f OC), and octanol-air partition coefficient (K OA)) model is put forward to predict the K SA values for PCBs and total DDTs.