Groundwater Hydrogeochemistry, Regional Vulnerability and Trace Metal Enrichments Around Indus Basin Agricultural Fields of SE Punjab, India

Abstract

Aquifer-groundwater interaction plays an important role in controlling subsurface hydrogeochemistry along semi-arid regions because of limited rainfall and overexploitation of groundwater for domestic and irrigation use. Geochemical processes, nature of aquifer mineralogy, irrigation and domestic usability of groundwater, and pollution vulnerability along Indo-Gangetic Quaternary alluvial plain of Fatehgarh Sahib, SE Punjab, India was studied. The groundwater is slightly alkaline (pH 7.4–8.3) with total dissolved solids of 520–1060 mg L⁻¹, hardness of 164–314 mg L⁻¹ CaCO₃ and salinity of 400–800 mg L⁻¹ where the central region contains little greater contents. Groundwater is of NaHCO₃ and CaHCO₃ water type and Na⁺ and HCO₃⁻ constitute the abundant cations and anions, respectively. Silicate rock weathering and evaporation processes have majorly controlled the regional hydrogeochemistry, while cation exchange has dominated the ion exchange process. Other than water hardness (> 160 mg L⁻¹ CaCO₃), K⁺ (> 5.8 mg L⁻¹) and HCO₃⁻ (> 360 mg L⁻¹), no threats for drinking purpose is found from physical properties and chemical composition of groundwater. However, combined parameter weighted arithmetic water quality indices (WQI) suggest poor to very poor quality for drinking use (WQI- 133–325). A mixed irrigation suitability is inferred from agricultural indices where residual sodium carbonate (RSC- 0.9–5.2) and Kelley’s ratio (KR- 0.5–1.4) suggests > 50% of the studied groundwater is unsuitable for irrigation use, while percent sodium (Na%- 31–57) and sodium absorption ratio (SAR- 2.0–3.8) suggests their permissible limits with no sodium hazard concerns. Upto 2.0 mg L⁻¹ F⁻ was measured where > 40% samples exceeds the desirable limit (1.0 mg L⁻¹) and SW region groundwater is relatively enriched in F⁻ irrespective of their depth. Both geogenic and fertilizer origin of F⁻ is proposed with no sharp distinction of predominance of any. Uranium and As contents exceed the permissible limit in 43% (> 30 µg L⁻¹) and 21% (> 10 µg L⁻¹) of the studied groundwater, while Se, Cu, Cr, Co, Mo, Ni, Zn, Th are within their permissible limits with heavy metal pollution indices of 16–167. The central and SW region groundwater which is the regional groundwater flow direction is more deteriorated in terms of drinking and irrigation use and trace metal and F⁻ enrichment compared to eastern and NE region.