Assessing the Impact of Persistent Pesticide Pollution in an Agricultural Region in Lower Bengal Basin with a Newly Developed Indicator

Pesticides have made a stark difference in the agricultural sector by increasing food production globally but subsequently affected ecological and human health. Classifying the high pesticide polluted sites is essential in promoting the sustainable use of pesticides. Such identification is made by determining pesticide concentrations in the various environmental compartments. But the vulnerability of a site does not restrict to the pesticide concentration alone. A newly developed indicator called "Level of Concern" was assigned to a site by integrating five factors: the ecological and human health risks due to exposure to pesticide concentrations, freshwater availability, agricultural yield, and biodiversity richness. A case study was conducted to allocate "Level of Concern" to an agricultural region located in the Lower Ganges Basin in West Bengal, India. The concentrations of 20 prohibited and restricted organochlorine pesticides (OCPs) were investigated across pre-monsoon, monsoon, and post-monsoon seasons. No discernible spatial variation was seen in the OCPs concentrations in the study area. The mean concentrations of ΣOCPs in groundwater were 122.1 ng/L in pre-monsoon, 144.7 ng/L in monsoon, and 126.9 ng/L in post-monsoon. The concentrations in the surface water were 104 ng/L, 138 ng/L, and 147 ng/L, respectively, in the pre-monsoon, monsoon, and post-monsoon seasons. No significant seasonal difference was observed in the groundwater, but the concentrations of pesticides were significantly higher in monsoon, and post-monsoon surface water, which could be attributed to the timing of pesticide application and agricultural runoff. Fresh usage of lindane, endrin, aldrin, and heptachlor, were encountered, whereas the presence of DDT, endosulfan, and chlordane were mainly from historical use, causing high ecological and human health risks. The study area was suffering from a high risk of freshwater scarcity, while supporting high agricultural yield and bearing high biodiversity richness. Therefore, integrating all the high risks from all the parameters, our case study area was identified with the highest level of concern.