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(052) The rapid equilibration of pasture with atmospheric semi-volatile organic chemicals: implications for foodchain transfer. Smith, Kilian1, Thomas, Gareth1, Jones, Kevin1, 1 ABSTRACT- Atmospheric inputs are considered to dominate the supply of semi-volatile organic chemicals (SOCs) to vegetation such as pasture. The kinetics of equilibration of pasture with atmospheric gas and particle phase SOCs were investigated in a field situation over the growing season. For both the gas and particle phases, uptake by the vegetation was very rapid, with equilibrium concentrations being reached between the pasture and the overlying atmosphere within 3 days. The majority of the compounds displayed a marked seasonality over the growing season, with winter concentrations being higher than summer ones. Changes in the air concentrations in combination with the temperature dependence of the gas - plant partitioning process drove the observed seasonality. For some compounds soil volatilisation was also important in contaminating the pasture. Different plant and sward characteristics did not have an influence on the interception and retention of either the gas or the particle phase SOCs. The implications of these findings for the transfer of these chemicals into the agricultural foodchain are discussed. Key words: SOCs, pasture, equilibration , foodchain |
