Appraising factors governing sorption and dissipation of the monoterpene carvone in agricultural soils

Abstract

he use of monoterpenes as agrochemicals has been proposed, but the behavior of this family of compounds once they reach the soil environment has not been completely examined. In this work, we investigated the sorption of the two optical isomers of the monoterpene carvone, R-carvone and S-carvone, on different soils and model sorbents, as well as their dissipation in selected soils. Sorption was a non-enantioselective process; from racemic initial solutions, R-carvone was sorbed to the same extent as S-carvone. Correlations with soil properties indicated that organic matter was the most important component determining the sorption of carvone on the soils. Accordingly, higher sorption of carvone enantiomers was measured on organic model sorbent (humic acid, Kd = 28 L kg−1) compared to mineral model sorbents (kaolinite, illite, montmorillonite, ferrihydrite, Kd < 6.3 L kg−1). Desorption from the soils was hysteretic, most likely because of the rapid degradation of the enantiomers in the soils. Dissipation of carvone in soils was microbial mediated and enantioselective, with S-carvone being degraded faster than R-carvone. The individual enantiomer dissipation rates and enantioselectivity depended on soil characteristics, such as pH. The findings of this study constitute a base for the understanding of the fate of monoterpenes in soils and for further investigations on their applicability as environmentally friendly agrochemicals