Abstract
Assessment of groundwater quality, contamination sources and geochemical processes in the coastal aquifer of Tugela Catchment, South Africa were carried out by the geochemical and statistical approach using major ion chemistry of 36 groundwater samples. Results suggest that the spatial distribution pattern of EC, TDS, Na, Mg, Cl and SO4 are homogenous and elevated concentrations are observed in the wells in the coastal region and few wells near the Tugela River. Wells located far from the coast are enriched by Ca, HCO3 and CO3. Durov diagrams, Gibbs plots, ionic ratios, chloro alkaline indices (CAI1 and CAI2) and correlation analysis imply that groundwater chemistry in the coastal aquifer of Tugela Catchment is regulated by the ion exchange, mineral dissolution, saline sources, and wastewater infiltration from domestic sewage; septic tank leakage and irrigation return flow. Principle component analysis also ensured the role of saline and anthropogenic sources and carbonates dissolution on water chemistry. Spatial distributions of factor score also justify the above predictions. Groundwater suitability assessment indicates that around 80% and 90% of wells exceeded the drinking water standards recommended by the WHO and South African drinking water standards (SAWQG), respectively. Based on SAR, RSC, PI, and MH classifications, most of the wells are suitable for irrigation in the study region. USSL classification suggests that groundwater is suitable for coarse-textured soils and salt-tolerant crops. The study recommends that a proper management plan is required to protect this coastal aquifer efficiently.
Highlights
Groundwater in the coastal aquifer is generally affected by the complex geochemical processes and multiple contamination sources [1,2,3]
The purpose of this study is to evaluate the groundwater chemistry and its associated geochemical processes and to evaluate the contamination sources in this coastal aquifer
PH, DO, oxidation-reduction potential (ORP), K and HCO3 is not correlating with other variables. These results suggest that water is strongly affected by the saline and surface contamination sources as well as mineral weathering
Summary
Groundwater in the coastal aquifer is generally affected by the complex geochemical processes and multiple contamination sources [1,2,3]. Increasing population rates, intense irrigation activities, drainage patterns for industries and domestic sewage systems in the urban coastal areas resulted in severe damages to the groundwater quality [4,5,6]. Geochemical processes in the aquifer are strongly related to geological formations, climatic conditions, groundwater flow, residence time, etc. In the arid and semi-arid climatic condition, evaporation, ion exchange reactions, oxidation-reduction processes, dissolution and precipitation of minerals takes place in the aquifer, which alters groundwater chemistry [9,10,11]. Surface contamination sources play a major role on water pollution due to shallow depth compared to natural processes. 2007, South African Water Quality Guidelines (SAWQG).
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