| Abstract
| - A wetted wall column device was used to determine air−waterdistribution coefficients [Henry'slaw constants (HLCs)] for pesticides: chlorpyrifos, trifluralin,endosulfans I and II, methyl parathion,metolachlor, and 2,4-D. The measured HLCs were all significantlyhigher than values calculatedfrom published vapor pressure and solubilities except those fortechnical endosulfan and 2,4-D.With 2,4-D, however, the HLC was higher under acidic conditions.The effects of temperature andsalinity were investigated using chlorpyrifos, trifluralin, andendosulfan I. Simulated seawaterincreased the HLCs from 1.5 to 2.4 times, which suggests a salting outeffect. Natural water HLCvalues that were determined on Chesapeake Bay and Bering/Chukchi Seawater samples ofmicrolayer and subsurface water were all lower than predicted valueseven after correction fortemperature and salinity. Therefore, some as yet undefined factorsin the aqueous phase appearto be responsible for these lowered HLCs. There was generally alinear increase in the log HLCversus increase in temperature for all of the pesticides in bothdistilled water and salt water exceptfor trifluralin, which was curvilinear in simulatedseawater. Keywords: Henry's law constants; air−water partitioning; chlorpyrifos;trifluralin; endosulfan;methyl parathion; 2,4-D; metolachlor
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