The determination of organochlorinated pesticides and polychlorinated biphenyls in sediment, soil and water of the Msunduzi River, KwaZulu-Natal, South Africa.
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Date
2014
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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.
Description
M. Sc. University of KwaZulu-Natal, Durban 2014.
Keywords
Pesticides--KwaZulu-Natal., Water--Pollution--KwaZulu-Natal., Soils--Pesticide content--KwaZulu-Natal., Water--Pesticide content--KwaZulu-Natal., Polychlorinated biphenyls., Organochlorine compounds., Theses--Chemistry.