Spatial variability in surface water quality of lakes and ex-mining ponds in Malacca, Malaysia: the geochemical influence

A surface water quality assessment was carried out to explore the spatial variations between lakes and ex-mining ponds in Malacca with the aid of chemometrics tools. The physio-chemical data included pH, dissolved oxygen, total dissolved solids, electrical conductivity, biological oxygen demand, and ammoniacal nitrogen, which were measured in situ. Meanwhile, the elemental concentrations were determined by inductively coupled plasma mass spectrometry. Hierarchical cluster analysis of the water quality dataset revealed a clustering pattern that was strongly associated with their underlying geochemical variations. A similar trend was also demonstrated in the principal component analysis which suggested that the variability in the water quality depended mainly on the nature of ponds/lakes, whereby the dominance of Ca, Mg, electrical conductivity, and total dissolved solid could plausibly be linked with the dissolution of rocks; and part of the variation was originated from their current uses. Based on the linear discriminant analysis model, the ex-mining ponds were characterized with As, Ca, Mg, and Mn concentrations whereas Na, Fe, pH, and ammoniacal nitrogen levels were associated with the lakes. Despite the inherent variability characteristics between both water sources, the corresponding metal index revealed no significant As a threat. But, in most cases, Fe exceeded the reference limit, which was attributed to its natural abundance. Therefore, these surface water sources could be considered as potential reservoirs for potable supply after conventional treatment.