Unified model for groundwater quality assessment using multivariate statistical techniques and geospatial approaches in northern Tiruvallur, Tamil Nadu, India

Abstract

This study presents an integrated hydrochemical assessment of groundwater in the northern Tiruvallur District, Tamil Nadu, and India, aimed at evaluating its suitability for drinking, irrigation, and industrial use. A total of 50 groundwater samples, collected in 2023, were analyzed for key physicochemical parameters. Results reveal that the majority of samples exhibit slightly alkaline pH and elevated hardness, with critical parameters electrical conductivity (1354 μS/cm), total dissolved solids (1104 mg/L), total hardness (449 mg/L), sodium (236.7 mg/L), calcium (88.8 mg/L), chloride (411 mg/L), magnesium (52.9 mg/L), bicarbonate (269 mg/L), nitrate (13.90 mg/L), and fluoride (0.39 mg/L) exceeding World Health Organization (WHO) permissible limits for potable water. Multivariate statistical techniques, including Pearson correlation and R-mode factor analysis, identified TDS, EC, TH, Na⁺, and Cl⁻ as the dominant controlling variables. Ionic distribution followed the order Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ and Cl⁻ > HCO₃⁻ > SO₄²⁻, indicating both marine intrusion and geogenic processes. Geospatial mapping delineated zones of salinity, alkalinity, and anthropogenic influence, while the Piper diagram classified the majority of samples as Na–Cl water type especially prominent in coastal locations suggesting seawater intrusion. The Water Quality Index (WQI) ranged from 37.9 to 299, with 62.5 % of samples falling within excellent to acceptable categories for drinking purposes. Additionally, 36 sites were deemed suitable for agricultural irrigation. The findings underscore the interplay of natural and anthropogenic drivers on groundwater quality and emphasize the need for robust, location-specific groundwater management strategies to safeguard this vulnerable coastal aquifer system.