Abstract
Present Lake Environment of Hartbeespoort Dam was evaluated from Geochemistry of bottom Sediment. Ten (10) bottom sediment samples were collected across the entire Lake. The geochemical composition of the sediment samples was determined using X-ray fluorescence (XRF); trace and major elements determined includes As, Pb, Zn, Cu, Ni, Cr, Fe 2 O 3 , TiO 2 , MnO, CaO and P 2 O 5 . The trace elements concentrations of the sediment were grouped into three zones base on their spatial distribution. The Western zone of the lake shows a remarkable enrichment in Nickel (Ni) and Chromium (Cr) and could be associated with geogenic source. However high enrichment of phosphate (P 2 O 5 ) observed in the same zone could be attributed to anthropogenic source, due to agricultural activities on the catchment of Magalies River. Moderate enrichment of As, Zn, Cu, Cr and Pb was recorded in the central zone and could be ascribed to entrapment by fine-grained organic and Fe-rich clay deposit in the central part of the lake; this was showcased by the strong positive correlation between the trace elements and Fe 2 O 3 . As, Zn, Pb and Cu were highly enriched in the South – Eastern zone and anthropogenic source could be responsible for the enrichment due to the influence of the Crocodile River. The average concentration of As, Pb, Zn, Cu, Ni and Cr in the sediment were evaluated by comparison with the upper continental crust (UCC), Shale standard (Turekian and Wedepohl, 1961) and Sediment quality guidelines (SQG); the result indicates that As, Pb, Zn, Cu and Cr in the study area were above the lowest effect level (LEL) but below the severe affect level (SEL) which shows that the impact on biota is moderate. However, Nickel (Ni) was above the severe effect level and could therefore have severe effect on the aquatic environment. Keywords: aquatic environment, Bottom Sediment, Heavy Metals, Hartbeespoort Dam, X-ray fluorescence DOI : 10.7176/JEES/9-11-10 Publication date: November 30 th 2019
Highlights
Since ancient civilization Freshwater lakes are acknowledged as centres for cultural development and urbanization, these fresh water bodies are increasingly faced with threat of pollution from agricultural activities, industrialization, waste generation and other related activities as a result of population density (Forstner & Wittmann, 1979)
The Heavy metal concentration in Hartbeespoort dam was determined through bottom sediment sample analysis
The trace elements concentrations of the sediment were grouped into three zones base on their spatial distribution
Summary
Since ancient civilization Freshwater lakes are acknowledged as centres for cultural development and urbanization, these fresh water bodies are increasingly faced with threat of pollution from agricultural activities, industrialization, waste generation and other related activities as a result of population density (Forstner & Wittmann, 1979). The sampling stations were located strategically on western, central and south-eastern part of the lake to target sediments from the two major inflows into the dam, which are the Crocodile and the Magalies River. 5.2 Spatial distribution of elements Concentration across the study area The concentration of metals in the bottom sediment of Hartbeespoort Dam, represented graphically to show the spatial distribution of the enrichment in the study area indicates that the heavy metal enrichment can be divided into three zones; (i) The western zone (ii) The Central zone (iii) The south-eastern zone This is based on the sampling pattern of this study. Phosphate (P2O5) was enriched in the western zone, this can be attributed to Anthropogenic source because the Magalies River and its tributaries drains mostly pastoral area used for grazing, agriculture and nature reserves (NIWR, 1985)
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