Spatiotemporal Distribution, Risk, and Source Identification of Organochlorine Pesticides in the Surface Water of Shitalakshya River, Bangladesh.
Islam Md Mazharul MM, Shoeb Mohammad M, Mamun Md Iqbal Rouf MIR
This study investigates the spatiotemporal distribution of organochlorine pesticides (OCPs) in the surface water (n = 60) of Shitalakshya River, Bangladesh, by an optimized and validated LLE-GC-ECD method by calibration (0.10-5.00 µgL-1), linearity (R 2 = 0.995-0.999), recovery (80.11%-117.10%), precision, specificity, selectivity, LODs (0.0009-0.0026 µgL-1), and LOQs (0.0027-0.0079 µgL-1). Among the targeted OCPs, α-BHC (0.01-0.19 µgL-1), δ-BHC (0.01-0.27 µgL-1), chlordane (0.01-0.23 µgL-1), endosulfan (0.01 and 1.56 µgL-1), 4,4'-DDE (0.01-2.14 µgL-1), dieldrin (0.03-0.58 µgL-1), endrin (0.01-2.96 µgL-1), 4,4'-DDD (0.01-4.07 µgL-1), endrin aldehyde (0.01-3.72 µgL-1), 4,4'-DDT (0.01-0.02 µgL-1), and endosulfan sulfate (0.03-2.05 µgL-1) were detected with varying frequencies. These levels were below the international guideline values, except 4,4'-DDE in Kanchon (2.14 μgL-1), dieldrin in Kanchpur (0.10 μgL-1), Atlapur (0.12 μgL-1), Ghorashal (0.45 μgL-1), Charshindur (0.58 μgL-1) and Kapasia (0.03 μgL-1), endrin in Kapasia (2.96 μgL-1), 4,4'-DDD in Kalagachhia (1.63 μgL-1), Narayanganj (0.69 μgL-1), Nabiganj (1.95 μgL-1), Ichakhali (1.05 μgL-1), Kanchon (0.57 μgL-1), Atlapur (1.02 μgL-1), Ghorashal (2.51 μgL-1), and Charshindur (4.07 μgL-1). The occurrence of OCPs exhibited pronounced spatiotemporal variation, with the highest concentrations and detection frequencies observed during the dry seasons (L. autumn, autumn, winter, and spring), indicating reduced dilution and possible remobilization from contaminated sediments. Multivariate statistical analysis revealed distinct sources, with endosulfans and BHCs dominating at Kanchon, whereas dieldrin, endrin, and chlordane were more strongly associated with Ghorashal and nearby locations, suggesting localized anthropogenic inputs and legacy pollution sources. While risk is generally low, specific exceedances (H q > 1) were observed in L. Autumn 2022 for 4,4'-DDD, indicating a localized noncarcinogenic hazard. While the immediate screening-level risks are low across most seasons, the high chemical persistence and bioaccumulation over time warrant continued monitoring and proactive water management.