FURTHER-STUDIES OF THE AIR-PASTURE TRANSFER OF POLYCHLORINATED-BIPHENYLS

Field survey and field experimental data are presented and interpreted in the context of the factors controlling the supply of polychlorinat ed biphenyls (PCBs) to the pasture sward. The field experimental data show that an air (gas phase)-pasture equilibrium was approached rapidl y, within a few days, with a similar equilibrium attained between diff erent grass species studied (Lolium perenne, Holcus lanatus, Festuca o vina). A mass balance model for a typical UK air-pasture-soil system i s presented and used to estimate the distribution and rates of air-sur face exchange and sequestration of PCBs into freshly growing plant bio mass. A soil-air-vegetation model developed by Trapp and Matthies (199 7, Environmental Science and Technology 31, 71-74) and other informati on is used to consider the possible influence of soil outgassing and s equestration versus the supply of PCBs from the bulk air to the pastur e. It is hypothesised that a rapid approach to air-pasture equilibrium conditions could occur because PCBs are supplied from both the bulk a ir and by volatilisation from the underlying pastureland soil. (C) 199 8 Elsevier Science Ltd. All rights reserved.