Spatio-temporal distribution of organochlorine pesticide residues in water and sediments of tropical reservoirs: a case study of Bui Reservoir, Ghana

Abstract

This study investigated the spatio-temporal distribution of organochlorine pesticides (OCPs) in water and sediments of the Bui Reservoir from June 2017 to May 2018, to provide baseline data for monitoring contamination in the Reservoir. Samples were collected during four seasons reflecting levels of rainfall and from five sites around the Reservoir. Water and sediment samples were subjected to liquid-liquid separation and ultrasonic extraction, respectively. GC-ECD was used to identify and quantify the pesticide residues. Eight OCPs each for water and sediment were detected and their concentrations in water and sediment range from 0.1–4.6 µg l⁻¹ and 1.38–104.86 ng g⁻¹ dry weight, respectively. α-Hexachlorocyclohexane and trans-chlordane dominated with mean concentrations of 3.2 ± 0.08 µg l⁻¹ and 70.91 ± 3.47 ng g⁻¹ dry weight in water and sediment, respectively. There were non-significant differences (p > 0.05) in the spatial distribution of OCPs in water and sediments, but significant differences (p < 0.001) in the temporal distribution of the contaminants in water and sediments, with the wet season samples accounting for the highest concentrations. This indicated that the distribution, behaviour and fate of OCPs the the reservoir have close links with meteorological properties beyond their chemical composition.