Processes governing the environmental fates of alachlor in soil and aqueous media: a critical review

Alachlor is a chloroacetanilide herbicide which is commonly used to control different broad leaf weeds and annual grasses at their pre-emergence stage from various agricultural crops including maize, sorghum and soybean. Owing to its intensive and repeated use in agricultural fields, this herbicide was detected beyond the permissible limits in different soil and water resources worldwide. Ecotoxicological data suggest for its harmful impacts on different biotic components of the environment including plants, animal and human beings. The present review article has been focused on an overview of the toxic effects of alachlor as well as different processes including sorption, transport, leaching and transformations governing its fates in the environment. A detailed review of the data indicated that alachlor has a relatively low sorption and persistence in the soil and aqueous media because it is easily degraded by different physicochemical processes as well as by different microbial strains existing in the soil. The degradation results into the formation of different types of metabolites following different metabolic pathways, which have also been presented in this review article. The distinctive role of different bacterial and fungal strains in the biotransformation of this herbicide in soil and aqueous media as well as the enzymes potentially involved in its biodegradation has also been highlighted herein.