Assessing Groundwater Quality: Statistical and WQI Approaches on Nitrate Pollution in Hard Rock Aquifers of Bargarh Block in Western Odisha, India

ABSTRACT In the current investigation, geostatistical application and the Water Quality Index (WQI) method were employed to understand the geochemical characteristics, nitrate dynamics, and the susceptibility of different human groups to nitrate pollution in the hard rock aquifers of the Bargarh block in Western Odisha, India. Forty groundwater samples were collected and examined for various physicochemical properties. The ionic composition of the groundwater was found to follow the trend Ca 2 + > Na + > Mg 2 + > K + = SO 4 2 − > HCO 3 − > Cl − > NO 3 − > F − . Geochemical interpretations indicated that inverse ion exchange governs the groundwater chemistry in the region. Nitrate concentrations ranged from 1.1 to 280.03 mg/L, with 45% of the samples exceeded the WHO drinking water limit. The Nitrate Pollution Index ranged from clean to heavily polluted categories. A Human Health Risk Assessment highlighted that children and females are at a higher risk of experiencing adverse non‐cancerous health effects from nitrate exposure than males. The primary source of nitrate was widespread agricultural runoff caused by over‐application of fertilizers and pesticides, with domestic waste as a secondary contributor. Furthermore, about 38% of the groundwater samples were undrinkable, while the WQI rated more than 40% of the groundwater as poor to very poor quality. Despite this, groundwater was considered appropriate for irrigation based on Sodium Adsorption Ratio, Percent Sodium, Residual Sodium Carbonate, and Kelly Ratio. The findings call for targeted nitrate mitigation, including precision fertilizer use, improved wastewater handling, and long‐term monitoring to ensure safe groundwater use for future generations.