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Occurrence of Unapproved Pesticides and their Ecotoxicological Significance for an Agriculturally Influenced Reservoir and its Tributaries in Nepal

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posted on 2024-02-08, 02:59 authored by Suman AcharyaSuman Acharya, HR Upadhayay, M Houbraken, RM Bajracharya, P Spanoghe

Many catchments in Nepal are affected by intensive agricultural activities, leading to extensive pesticide usages. This study aimed to assess pesticide abundance in concurrently collected water, sediment and fish samples for the first time in intensively cultivated catchment (Indra Sarowar) located in the mid-hill region of Nepal during the rice and vegetables growing season. A total of 75 pesticides were analysed, of which 4 pesticides (alachlor, diuron, metalaxyl and pyrimethanil) were present in water with detection frequency (DF) > 40%, with alachlor (0.62 – 2.68 µg L−1) being ubiquitous. In the sediment of tributaries, the pesticides p,p′-DDT, β-HCH, alachlor and diuron were detected with DF exceeding 40%, where β-HCH was commonly observed (DF = 92%) with concentration ranging from 6.29 – 99.22 µg kg−1. The ecotoxicological risk indicated that herbicides (alachlor and diuron) posed a high risk to aquatic organisms in both tributaries and reservoir water. Such risk in sediment was even more pronounced, with alachlor and diuron showing up to 2.3 and 53.7 times higher risk respectively compared to water samples. However, none of these herbicides were detected in fish muscles. Among the fish species studied, pyrimethanil was the only quantified pesticide in edible tissue of both cage cultured (0.35 – 1.80 µg g−1 ww) and open stock fishes (0.06 – 1.12 µg g−1 ww). The consumer risk assessment showed very low human health risk associated with fish consumption (HQ < 0.2). Nonetheless, long-term consumption of contaminated fish may pose some risk that cannot be ignored. Overall, this study generated the benchmark data highlighting pervasive presence of banned (DDT, endosulfan, HCH) and unapproved (alachlor, diuron, pyrimethanil) pesticides in the environmental compartments in the mid-hill’s streams of Nepal. 


This research was financially supported by Vlaamse Inter-universitaire Raad (VLIR) Belgium as a part of an ICP-Master grant (Master of Environmental Sanitation) for S. Acharya. She is also supported by La Trobe University Postgraduate Research Scholarship (LTUPRS), La Trobe University Full Fee Research Scholarship (LTUFFRS) and PhD Top-Up Scholarship supported by the Murray-Darling Basin Joint Government in association with the Centre for Freshwater Ecosystems (CFE). Rothamsted Research receives strategic funding from the UK Biotechnology and Biological Sciences Research Council (BBSRC) and contributions to this manuscript by H.R. Upadhayay was supported by the institute strategic programme Soil to Nutrition funded by grant award BBS/E/C/000I0330.


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Water, Air, and Soil Pollution



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Springer Nature



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