Hydro geochemical Dynamics, Trace Metal Distribution and Depth-Dependent Vulnerability of Alluvial Aquifers in Sakrand City, Pakistan

Abstract

Sub-ground water in semi-arid developing regions is still susceptible to degradation, despite being a vital part of human well-being and environmental stability, because of the lack of municipal treatment facilities. A detailed spatial hydro-chemical and toxicological evaluation of the groundwater quality of 30 residential, commercial and agricultural sampling sites (N = 30) of Sakrand City in Sindh, Pakistan is presented. Ten elemental and physicochemical parameters were measured using ICP-OES along with conventional methods, and compared with the World Health Organization (WHO) standards. Groundwater in the region is neutral to weakly alkaline (pH 7.40–8.30), with cationic dominance following the order Na+ (47.8%) > Mg2+ (24.3%) > Ca2+ (18.3%) > K+ (9.6%). Results show that water safety is mainly limited by salinity and halide buildup from the water sources and not by the presence of toxic heavy metals which are generally 1 to 3 orders of magnitude lower than the maximum WHO limits. Electrical Conductivity (33% expedience rate), Chloride (30%) and Magnesium (30%) and Total Dissolved Solids (17%) were among the parameters that exceeded WHO guidelines. When the water was compared with depth, shallow hand pumps had significantly higher ionic loads (TDS = 814 mg/L) when compared to deeper bore wells (TDS = 736 mg/L) owing to the vulnerability of the upper aquifer to domestic waste water, agricultural run-off and high evapotranspiration. Single factor analysis of variance (ANOVA) showed that there was significant spatial variation among all the parameter groups (F = 330.68, p = 0.001). The result highlights the critical need for treatment strategies that focus on depth to extract salt (depth targeted extraction), on-site point-of-use filters, and site-specific groundwater management protocols to address the salinity risk in Sakrand City.