Coastal Aquifer Contamination and Geochemical Processes Evaluation in Tugela Catchment, South Africa—Geochemical and Statistical Approaches

Abstract

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 SO 4 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, HCO 3 and CO 3 . 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.

Assessment of Groundwater Quality in the Talensi District, Northern Ghana

“…In natural water systems, bicarbonate is the dominant anion within pH ranges of 4.5-9 [57]; as such, the dominant anion in the groundwater system was bicarbonate, in the given pH ranges. Although other parameters such as Ca 2+ , Mg 2+ , Na + , CI − , SO 4 2− , NO 3 − , and PO 4 3− displayed high variations and deviation from the mean, the values fall within the WHO [59] permissible limits for domestic water use. Most of the parameters appear to be positively skewed and, thus, scaled towards the right tail, except for Mg 2+ , K + , and PO 4 3− which appear negatively skewed with outliers skewed to the right (Figure 7).…”

“…All the samples were clearly labelled and preserved in ice chests that had been conditioned to a temperature of about 4°C by ice until they were ready to be transported to the laboratory for analysis. Water samples were analysed for physicochemical parameters such as pH, electrical conductivity (EC), calcium (Ca 2 ⁺), magnesium (Mg 2 ⁺), sodium (Na⁺), potassium (K⁺), sulphate (SO 4 2− ), chloride (Cl⁻), bicarbonate (HCO 3 − ), nitrate (NO 3 − ), phosphate (PO 4 3− ), fluoride (F − ), salinity (SAL), and Total Dissolved Solids (TDSs) in the laboratories of the Chemistry Department of National Nuclear Research Institute (NNRI) of the Ghana Atomic Energy Commission (GAEC). Physical parameters such as pH, EC, TDS, and salinity were measured using HI 2550 pH/ORP & EC/TDS/NaCl Meter.…”

“…Atomic absorption spectroscopy (AAS) was used to determine the major cations and trace elements. Anions such as Cl − , SO 4 2− , NO 3 − , F − , and PO 4 3− were analysed using Dionex DX 120 ion chromatograph. e dataset was subjected to charge balance error (CBE) to test the accuracy of the analysis (equation (1)).…”

“…Parameters such as Pb, F-, NO 3 − , and pH which are believed to be of critical health importance and significant impactors of the quality of groundwater were assigned the maximum value of 5. TDS, TH, Ca 2+ , Mg 2+ , Na + , K + , CI − , SO 4 2− , PO 4 3− , and Fe were assigned values of 2 to 4 ( Table 1) depending on their perceived significance relative to groundwater potability and health implications. is method also involves the computation of relative weights (Wi) (equation (8)) and quality rating scale (qi) (equations (4)) and determination of the subindex (SI) (equation (5)) and water quality index (WQI) (equation (6)).…”

“…Several combinations of factors work together and/or in isolation to determine the quality of groundwater in space and time. erefore, groundwater is not always as safe as it is believed to be, since its quality can be influenced negatively by weathering of the rock matrix through which it travels [4][5][6]. e degree of rock weathering which influences groundwater quality is also dependent on factors such as the residence time, pH, and ambient temperatures [7].…”