Analysis of organochlorine pesticides in water, sediment and fish of gilgel gibe (i) hydroelectric dam, oromia, Ethiopia

Abstract

In this study, analysis of organochlorine pesticides (OCPs) has been carried out in water, sediment and fish samples collected from Gilgle Gibe (I) hydroelectric dam of Ethiopia, using gas chromatography with electron capture detector (GC-ECD). Low density based dispersive liquid-liquid microextraction (LDDLLME) using toluene (as extractant) and acetone (disperser) was used for extraction OCPs from water samples and soxhlet extraction, using 150 mL acetone: n-hexane (20:80 v/v) was used for extraction of sediment and fish samples. After soxhlet procedure, sediment and fish extracts were cleaned with Florisil solid phase extraction (SPE). External calibration curves constructed at five concentration points were exhibited wide linear ranges, i.e., 0.2 – 100 μg/L, with excellent coefficient of determination, r2, ranging 0.999 -1.00. The limits of detection and quantification (LOD & LOQ) of the utilized method which were determined as 3 and 10 times the signal-to-noise ratio were ranging 0.06–0.72 μg/L and 0.30–2.40 μg/L, respectively. The efficiency of the methods was also evaluated by spiking the samples with known concentration of the target analytes and the obtained recoveries were ranging from 67 - 118%. Except gamma-chlordane, which was not detected in fish samples, all the studied samples, i.e., water, sediment and fish samples contain all target OCPs in the increasing order of their concentrations water < fish < sediment samples. Among the studied OCPs, DDE, endrin and dibuthyl chlorendate were observed at smallest concentration levels, in water, sediment and fish sample respectively and heptachlor epoxide was observed at highest concentration level in all sample type. The bioconcentration studies also demonstrated that the analytes are more concentrated in sediment than in fish samples. In general, the finding demonstrated that Gilgel Gibe I hydroelectric dam water and sediment as well as fishes grown in the dam water contain the studied pesticides residues by far above the WHO permissible limits. Thus, apart from hydroelectric power generation, use the dam water for agricultural purpose such as irrigation and/or fish production as well as recreation has health risk to the consumers.