Investigation of selected organic compounds on water quality along the Olifants river catchment

Abstract

Water is a crucial natural resource, indispensable to food production, life, the environment, power generation, industry, sanitation and hygiene. The presence of Organochlorine Pesticides (OCPs) in the environment is not wanted due to their negative effects on human beings and animals. As a result, there is a need to continuously monitor their presence in the environment. In this study, surface water samples were collected once a month during the dry season and during wet season from the selected five points along the Olifants River and stored at a temperature of < 50C before analysis. The OCPs were extracted with dichloromethane (DCM) using the Liquid-Liquid Extraction (LLE) method. After undertaking the sample through the clean- up process, the crude extracts obtained were put into the column chromatography and eluted with hexane, about 1.5 μL of the purified extracts were analysed by the Gas Chromatographic- Mass Spectrophotometer (GC/MS). The percentage recoveries, varied from 32- 116 % for p, p’-DDT and 4,4'-DDD respectively in triply spiked water samples. The standard deviation for most of the compounds is less than±0.04, with the exclusion of Heptachlor (±0.14). The seasonal variability of OCPs in water samples along Olifants River results show that in dry season, the Olifants River is mostly polluted at the Oxford site with (BHC-beta, Aldrin, Heptachlor-epoxide, Endosulfan-alpha and Endrin), at the Ga- Selati site with (Heptachlor-epoxide and Endrin) and at the Wolvekrans site with (Endosulfan-alpha), with Aldrin up to 834.20 ng/ L indicating the highest hazard toward the aquatic environment while in summer the Olifants River is mostly polluted at the Ga- selati site with BHC-beta and at the Waterval site with (Heptachlor and BHC-gamma) with BHC- gamma up to 560 ng/ L indicating the highest hazard toward the aquatic environment. The levels reached from the Olifants River catchment were meaningfully above the drinking water quality guidelines for organic chemical recommended by WHO, 2006 i.e. (BHC-gamma,DDT-44, Aldrin, dieldrin and Endrin are (2.0,1.0,0.03,0.03 and 0.6) respectively for the protection of the domestic use, aquatic ecology and agricultural use (irrigation and livestock watering) for compounds with local guideline values; while, the international water quality guidelines to protect the aquatic ecosystems are 0.00083 ng/mℓ (4,4’DDD), 0.00059 ng/mL (4,4’DDE), (4,4’DDT), 0.00021 ng/mL (heptachlor), 0.0092 ng/mℓ (α-HCH), 0.0186 ng/mL (γ- HCH), and chronic values are 0.056 ng/mL (ENDO I and II) and 0.0023 ng/mL endrin) (USEPA, 2002). Levels detected were significantly higher than some research studies conducted up to now in South African aquatic environments. These results confirm the contamination of the Olifants River catchment by the OCPs.