Legacy Pesticides In An Urban Lifeline: Spatial Patterns, Statistics And Source Signatures Of Organochlorine Residues In The Hooghly River, India

Organochlorine pesticides (OCPs) are persistent organic pollutants that continue to pose long-term risks to aquatic ecosystems and human health due to their resistance to degradation and bioaccumulative nature. Despite regulatory restrictions in India, residues of these compounds are frequently detected in environmental matrices. The present study investigates the spatial distribution and statistical characteristics of four widely reported OCPs—DDT, HCH, Endosulfan, and Heptachlor— in surface water collected from six major ghats along the Hooghly River in Kolkata, India. Concentrations ranged from 0.99–2.19 ng L⁻¹ for DDT, 1.03–5.17 ng L⁻¹ for HCH, 0.06–0.23 ng L⁻¹ for Endosulfan, and 0.08–0.29 ng L⁻¹ for Heptachlor. HCH exhibited the highest mean concentration (3.57 ± 1.64 ng L⁻¹), while Endosulfan showed the lowest (0.16 ± 0.06 ng L⁻¹). Strong positive correlations (r > 0.93) among all pesticide pairs indicate common sources and similar environmental behavior. The spatial pattern revealed Babughat and Princep Ghat as contamination hotspots due to intense anthropogenic pressure. The persistence of these legacy pesticides highlights the need for continuous monitoring, source control, and improved regulatory enforcement in urban river systems.