Water Quality Assessment of the Southwestern and Coastal River Systems of Ghana

Investigation into physico-chemical water quality and dissolved heavy metal contents of major rivers from the Southwestern and Coastal River Systems of Ghana from 19 stations was undertaken from 2007 to 2010. The waters are used in their raw states for domestic purposes including drinking in most communities in the study area. The concentrations of the various parameters were assessed in relation to the Ghana Raw Water Quality Criteria and Guidelines for raw water, and in few instances, are compared with the WHO guidelines where the waters are known to be sources of drinking water. Turbidity, Total Suspended Solids (TSS) and Total Hardness were the physical parameters selected for the quality assessment of the waters in relation to domestic use. An Adapted Water Quality Index (WQI) was used to characterize the overall water quality status of the waters.  Turbidity and TSS were found to be above their respective Target Water Quality Range (TWQR) values for raw water, while Total Hardness concentration were within guideline values. The levels of the trace metals investigated in the waters, Fe, Mn, Zn, Pb, Cr, Ni, Cu, As, Cd, and Hg, were found to be  generally low, and do not yet pose health risks in the dissolved form. However, Fe and Mn levels were moderately high, exceeding their respective TWQR values stipulated for Ghanaian freshwaters.  An assessment of non-cancerous health risk from exposure to Fe, Mn, and Zn was performed with the Risk Integrated Software for cleanup (RISC 4.02) developed by the USEPA. Results of the risk assessment, however, revealed a hazard quotient greater than 1 in some locations, indicating that the risk of adverse health effects associated with exposure to zinc, manganese and iron is high in those locations. Efforts should therefore be made to prevent metal pollutants, mainly from mining activities, from entering our water bodies to keep them suitable for their intended uses. Keywords: Risk assessment, Southwestern Rivers Systems, Coastal Rivers Systems, Water Quality, Water Quality Index

Multivariate and spatial assessment of water quality of the Lower Pra basin, Ghana

In this paper, multivariate statistical approaches based on principal component analysis (PCA) coupled with spatial assessment were employed to assess physicochemical parameters (turbidity, pH, electrical conductivity, total dissolved solids, total suspended solids, nitrates, nitrite, phosphate, ammonium, total hardness, total alkalinity, dissolved oxygen, BOD, Na, Cl, Ca, HCO3, SO4 and F) and heavy metals (Cu, Cd, Fe, Mn, Pb, Hg and Zn) of more than fifty five (55) water samples from 20 mining and non-communities within the lower Pra basin. The correlation matrix, however, shows significant inter-metal relationships (p<0.05 and p<0.01). The Fe–Mn correlation is recognized as the weakest with a correlation coefficient r=0.422. Also, significant strong correlations (r>0.5) were found between Zn – Cd, Pb–Zn, Pb – Cd, Pb – Cu, Cu – Zn, Cu – Cd, Hg – Zn, Hg – Cd, Hg - Cu and two more toxic metals, Hg and Pb. From the results of the principal component analysis on surface water in the study, component model 1 is interpreted to be contaminated water with mercury. This is because Hg has the highest correlation value (0.985). Within the study area, illegal artisanal small scale miners (popularly referred to as galamsey) use mercury extensively in their activities. The mercury is a steady source of contamination of the surface water in the Lower Pra Basin area. The use of mercury in gold mining by the Artisanal Small Scale Miners constitutes a point source of contamination. Keywords: Multivariate statistical techniques, Principal component analysis, Lower Pra Basin, Heavy Metal