Enantiomeric ratios as tracers of soil-air exchange for organochlorine pesticides, /

Abstract

Past research has shown that selective degradation of enantiomers by microorganisms does occur. This work was done to determine concentrations and enantiomeric ratios of several chiral pesticides above an agricultural soil to determine if volatilization from the soil to the overlying air occurs. Quantitative analysis was done using gas chromatography with electron capture detection on a DB-5 capillary column. Concentrations were determined for five compounds (trans-Chlordane, cis-Chlordane, trans-Nonachlor, a-hexachlorocyclohexane, and y-hexachlorocyclohexane) at varying heights above an agricultural soil for the week of June 21-26, 1998. Trans-Nonachlor was found to be the highest in concentration for the five pesticides while ahexachlorocyclohexane was the lowest. Concentration gradients were determined for all five compounds. Enantiomeric analysis was done for trans-Chlordane, cis-Chlordane, and MC-5 (another chlordane component) using gas chromatography-mass spectrometry on a chiral phase capillary column. Enantiomeric excesses were found for all three pesticides. The enantiomeric ratios of the pesticides in overlying air were constant at all four heights above the soil and agreed well with the soil ERs determined previously. This suggests the soil as the primary source of these pesticides to the overlying air.