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| - Influence of Temperature on thePlant/Air Partitioning of SemivolatileOrganic Compounds
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| - Dry gaseous deposition is the main pathway of many SOCsto vegetation. It can be understood as a partitioningprocess between the plant and the gas phase. In thispaper,the temperature dependence of the partitioning of polychlorinated biphenyls between air and ryegrass (Loliummultiflorum) was investigated in the laboratory using asolid-phase fugacity meter, and the results were incorporatedinto a mathematical model of plant uptake of SOCs.Themeasured plant/air partition coefficients wereexponentiallyproportional to the reciprocal temperature, in agreementwith theoretical expectations. The enthalpy of phasechange (plant/air) was linearly proportional to theenthalpyof vaporization of the subcooled liquid, but the agreementbetween the two parameters was poor, the enthalpy ofphase change (plant/air) being lower than the enthalpy ofvaporization for the lower chlorinated PCBs and muchhigher for the higher chlorinated PCBs. The modelsimulationsshowed that under environmental conditions the temperature dependence of the partitioning coefficient does notinfluence the plant concentrations of most SOCs. Theslow uptake/clearance kinetics prevent the plant/airsystemfrom reacting quickly to the new equilibrium stateresultingfrom the temperature-induced change in the partitioncoefficient. Only for more volatile compounds such astrichlorobiphenyls or phenanthrene can the plant/air concentration ratio be expected to react to changes in temperature.
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