The water quality evaluation of aquifer systems on human health

Abstract

The semi-arid zone of Killinochi area in Northern Sri Lanka, which was ravaged by civil war for last 25 Years, is again being revitalized by human settlement in last couple of years. Conversely, water scarcity driven by increasing demand, deteriorating water quality (report of kidney stone and fluorosis) and non-efficient management is the most pressing issue for sustainable water resource management in the area. This work focuses on factors affecting water quality with special emphasis on excess hardness, nitrate and fluoride pollution. Forty four ground water samples comprising both shallow and deep aquifers were collected and analysed for different hydrogeochemical parameters to characterize and classify water samples based on a multitude of ion plots and diagrams. Among anions, the average abundance trend found was in the order HCO3- > Cl- > SO42- > NO3- > F-. On the other hand, the dominant cation was Ca2+ followed by Na+, Mg2+ and K+. High value of EC at point scale suggests the combined effect of the high concentration of dissolved solids, local variation in soil type, multiple aquifer system, agricultural activities in the area and salt water intrusion because of proximity to coast and excess water extraction. A high amount of hardness is mainly due to presence of multivalent cations coming from carbonate weathering from the minerals dominated by dolomite, magnesite and calcite. Other possible reason is indiscriminate use of glyphosate, the most widely used herbicide with its unique metal chelating properties. Prolong consumption of this groundwater causing health diseases like kidney stone, which has affected more than 2000 peoples in last ten years. It is found that nitrate enrichment mainly occurs in areas occupied with intense fertilizer practice in agricultural fields. In addition to that non-proper drainage system might also responsible for relatively higher concentration of nitrate at point scale. Since the area is not dominated by industrialization, the possibility of anthropogenic input of fluoride is almost negligible, and hence the enrichment of fluoride in the groundwater is only possible due to rock-water interaction. The highly alkaline conditions of the aquifer system favor the fluorite dissolution. The positive values of calculated saturation index (SI) with respect to calcite, dolomite, and gypsum for majority of the water samples suggest their oversaturation, which mainly has geological origin derived from the abundant carbonate weathering in the plain area. Show more