The determination of organochlorinated pesticides and polychlorinated biphenyls in sediment, soil and water of the Msunduzi River, KwaZulu-Natal, South Africa.

Abstract

Persistent organic pollutants (POPs) are a major class of organic contaminants of serious global concern due to their persistence in the environment because of their stability to photolytic, chemical and biological degradation. POPs are mostly semi volatile organic compounds (SVOCs) and include polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), which are toxic and capable of causing serious health disorders, such as, developmental and cancer related problems in animals and humans. Organic pollutants, such as, organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) are as well toxic as inorganic pollutants. There is limited information available on the concentration level and distribution pattern of organic pollutants within the KwaZulu-Natal Rivers as well as many studies done within this area have also only focused on inorganic pollutants. The lack of information and the need for knowledge on the organic pollutants in these rivers together with global concern for quality water has therefore prompted an investigation of the organic pollutants in the selected river. Therefore, the results and outcomes of this study could serve as a baseline assessment for various levels of government and scientific communities for future planning on the state of this river. The concentration patterns of selected priority pollutants (dirty dozen) made up of eight polychlorinated biphenyl (PCB) congeners and seven organochlorine pesticides (OCPs) together with six DDT metabolites were evaluated in sediment, soil and surface water during autumn, winter, spring and summer seasons from the Msunduzi River of KwaZulu-Natal, South Africa. Sediment, soil and water samples were collected at ten sites along the river in April 2013, July 2013, September 2013 and February 2014 that represented autumn, winter, spring and summer sampling seasons. Soil and sediment samples were dried and sieved while water samples were kept at 4 °C prior to the extraction. Soil and sediment samples were extracted by ultrasonication with dichloromethane (DCM) and water samples were subjected to liquid-liquid extraction using DCM. All sample extracts were cleaned up using multi-layered acidic/basic silica gel and all quality assurance steps were carefully observed. Both PCB congeners and OCPs were analysed and quantified in the sample extracts using gas chromatography–mass spectrometry (GC-MS). All the PCB congeners and OCPs analysed were detected in sediment, soil and water samples during all seasons. The results showed that sediment and soil samples contained the highest concentrations of both PCBs and OCPs with water samples having the lowest concentrations of all the analytes throughout the seasons. Concentrations of PCB congeners detected in the environment were found to be dependent on the number of chlorine atoms on the phenyl ring of PCB congeners, were PCB 180 exhibited the highest concentration and PCB 138 was found to be present in the lowest concentration. Total DDTs and endrin were the most predominant OCPs. The result of indicative indices suggested that the presence of DDTs could be attributed to the aged long degradation of DDT to its metabolites. The concentration patterns of the pollutants during the seasons were found to be in decreasing order of winter, spring, autumn and summer seasons. The concentrations detected in water samples during the seasons were also found to exceed the United State Environmental Protection Agency (USEPA) of 0.014 ng/mL and European Union (EU) 0.01 ng/mL recommended tolerable levels in surface and underground water respectively.