Herbicide residues in aquatic system: A review

Herbicides are usually applied in the early stages of the crop, at the time when the plant cover is little. Hence major portion of the chemical is liable to reach the soil and becomes a part of biological cycle in the environment. Concerns regarding the surface and ground water contamination due to the use of herbicides on crops and low land ecosystems lead to the necessity of a critical evaluation of the available residue data from India and elsewhere in the world. Longterm application of persistent chemicals is the determining factor for contamination of water bodies. The levels of herbicide residues in water depend on various factors like chemical nature and their behaviour in the environment, the agricultural practice, application rates, soil, geology and climatic characteristics. Persistence of phenoxy alkanoic acids and triazines are higher than the other groups of herbicides. This review discusses the persistence of major herbicides in various components of the aquatic system particularly in water, sediment and aquatic organisms and their possible threat to the environment.