Enantiomeric composition of Chiral pesticides in soil and air from the U.S. cornbelt region, /

Abstract

Past research has shown that selective enzymatic degradation of enantiomers by microorganisms does occur. This work was done to determine if enantiomeric ratios can be used to distinguish biotic from abiotic sources ofpesticide degradation. Concentrations and enantiomeric ratios were determined for several chiral organocWorine pesticides in soils and air from the combelt region. Concentrations were determined for eleven compounds (o,p'-DDT, p,p'-DDT, p,p'-DDD, p,p'-DDE, dieldrin, trans-cWordane, ciscWordane, trans-nonacWor, heptacWor, heptacWor epoxide, and ahexacWorocyclohexane) in 28 agricultural soils and one garden soil. The DDT compounds were found in the most samples and had the highest concentrations of all the compounds analyzed in the soil. Enantiomeric excesses were found for five compounds: o,p '-DDT, trans-cWordane, cis-cWordane, oxycWordane, and heptacWor epoxide, with the largest excesses for heptacWor epoxide. Six air samples were taken directly above agricultural soils, and enantiomeric patterns in air-above-soil samples mimicked the soils both in direction and relative magnitude of degradation. Seven ambient air samples were taken which showed the same general trends of enantiomeric degradation as soil and airabove- soil samples, although not as pronounced. Twenty-three indoor air samples were taken and concentrations determined for all eleven compounds as well as aldrin. Enantiomeric patterns were determined for three compounds, trans-cWordane, ciscWordane and a-hexacWorocyclohexane. Most ofthese values were racemic or very close to racemic. Enantiomeric analysis can be useful for distinguishing sources of pesticides to the atmosphere.