Sources and evolution of sulfate in groundwater systems of northern Kuwait

Higher sulfate concentration in Kuwait's irrigation water poses serious risks to plant health, as many crops have limited tolerance for such high levels. The study is the first attempt in Kuwait to address the elevated sulfate concentrations in the clastic aquifer of northern Kuwait through numerical modeling and geochemical techniques. The geochemical analytical results reveal that groundwater in northern Kuwait is alkaline, with ion abundances in the order of Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl^-  > SO₄^2-  > NO₃^-  > HCO₃^-. Sulfate concentrations range from 1200 to 3865 mg/L, with the highest levels found in areas near agricultural zones, raising concerns about the viability of this groundwater for consumption and irrigation without treatment. A likely impact of anthropogenic influence due to the application of fertilizers is observed due to the good correlation between NO₃^- and SO₄^2-. Sulfide oxidation and sulfate mineral weathering also increase the concentration of SO₄^2- ions in groundwater. Apart from oxidation, the inferences from geochmical modeling indicate dissolution as due to the undersaturation states of major sulfate minerals (gypsum/anhydrite). Numerical simulations further confirmed that the groundwater chemistry is driven by mineral dissolution, ion exchange, and anthropogenic influences, with key calibrated parameters including a longitudinal dispersivity of 10 m, an adsorption coefficient of 1 × 10^-⁶ [1/(mg/L)], and a chemical reaction rate of 5 × 10^-5 [1/day]. These findings underscore the critical need to manage sulfate levels in the aquifer to prevent adverse effects on water quality and usability, offering essential guidance for developing sustainable water management practices in northern Kuwait.