Assessment of minor ions and trace element chemistry in groundwater in Luvuvhu catchment, Limpopo province, South Africa.
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Date
2022
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Publisher
Univeristy of Zululand
Abstract
Agricultural activities are often associated with contamination of water, which
resulted in high concentration of nutrients and trace metals in the shallow aquifer.
Occurrence and distribution of nutrients and trace metals in the groundwater of
intensively irrigated region of Luvuvhu catchment was carried out to determine the
status of groundwater quality and its suitability for drinking. Groundwater samples
were collected and analysed for physiochemical parameters. The results suggest that
the concentration of nutrients and trace metals in the groundwater are below the
permissible limit of drinking water standards recommended by the World Health
Organization and South African standards except pH, K and Pb. Low pH (51%),
potassium (31%) and lead (100%) restrict the groundwater usage for drinking. Relation
between groundwater flow direction and EC, sulphate, nitrate, and ammonium
contents indicate that it is mostly constant towards the centre of the study area, but
sudden enrichment is noticed in the downstream. Silica and fluoride has increased
along with the direction of groundwater flow. Trace metals (B, Pb and Zn) show
decreasing trend in the flow direction. However, pH, K, Li, Cr, and phosphate
concentrations do not show significant variation along the flow direction. Positive
relation between nitrate, EC, sulphate, and ammonium implies that groundwater
quality is affected by the surface contamination sources, and mostly from irrigation
return flow, through the application of fertilizers and organic manures. However,
groundwater with high silica and fluoride also has high nitrate, which justifies that
wastewater infiltration from the surface has triggered the mineral dissolution in the
vadose. Trace metals does not correlate with nitrate. High concentrations of trace
metals are recorded with low nitrate, which implies that metals are derived from
mineral weathering. However, boron concentrations in a few wells show positive
relation with nitrate, which justified the impact of natural sources and irrigational
activities.
Description
A thesis submitted to the Faculty of Science, Agriculture and Engineering in fulfilment of the requirements for the Master of Science in the Department of Hydrology at the University of Zululand, South Africa, 2022.
Keywords
Luvuvhu catchment, Groundwater, Limpopo PRovince