Levels and distribution of pesticide residues in soil and sediments in Eastern Lake Tanganyika environs

Abstract

The aim of this study was to investigate the types, levels and distribution of pesticide residues in Eastern Lake Tanganyika basin in Tanzania. Water, soil and sediments samples were collected from various sites in Kigoma region. Analyses of cleaned sample extracts were performed using gas chromatographyelectron capture detection (GC-ECD) and gas chromatography-mass spectrometry (GC-MS). Six pesticide residues and metabolites were detected, namely, p,p'-DDT, o,p'-DDT, p,p'-DDE, p,p'-DDD, diazinon and chlorpyrifos. DDT, DDD and DDE were the predominantly detected compounds in all of the samples. Diazinon and chlorpyrifos were detected in soil samples only. The highest concentrations of total DDT in sediments and soil ranged from 10.02 to 116 μg/kg dry weight (dw) and 7.5 to 564.2 μg/kg dw, respectively. Chlorpyrifos and diazinon had concentrations up to 36 and 184 μg/kg dw, respectively. The concentrations of DDT residues were greater in soil samples than in sediments. The highest concentrations of DDT residues were detected in soil samples. The ratios of (p,p'-DDE + p,p'-DDD)/p,p'-DDT indicated recent inputs in most samples. The study reveals that there were recent uses of DDT, diazinon and chlorpyrifos in the region. Continued use of DDT indicates risks and may result into serious environmental problems. The area therefore needs serious environmental monitoring.

© 2017 International Formulae Group. All rights reserved.

Keywords: Pesticide, Lake, soil, sediments, Tanzania