Geogenic and anthropogenic contamination of toxic elements and nitrate content in the soil groundwater system in central part of south west Punjab India

Abstract

This study investigates trace element contamination in the soil-groundwater system of southwest Punjab, focusing on both shallow and deeper aquifers using integrated and multivariate approaches. Field activities involved collecting groundwater, soil surface samples (lt 1 foot), Subsurface (lt 30 feet) deep drill samples (up to 180 feet) and food samples, followed by laboratory analysis of elemental content and soil texture. Groundwater samples showed that elements like As, B, Cd, Li, Mn, Pb, Sr, and Se exceed permissible limits, with 68% and 13% of samples surpassing the NO3- limit in shallow and deep aquifers, respectively. Sodium Adsorption Ratio (SAR) and Kelly index reveal that many samples are inappropriate for agricultural use, with 55% of shallow and 58% of deep samples deemed unsuitable. WQI varies from 11.8 to 315.3 in the shallow aquifer, and 12.1 to 242.3 indicates that groundwater is largely unfit for drinking, and health risk assessments show that children are at higher non-carcinogenic risk from nitrate. At the same time, all age groups face As, Cr, and Cd carcinogenic risks. Multivariate analysis suggests that anthropogenic activities influence NO3-, Mn, Ni, and Zn levels, while geogenic factors control As and Mo concentrations. Agricultural samples showed double the trace element levels compared to barren samples, indicating a significant anthropogenic impact. Pollution levels classify the region as moderately contaminated, with lower trace element concentrations found in kitchen garden samples than agricultural areas. Aquifer characteristics varied, with some areas showing a higher concentration of silt and clay, correlating with elevated trace element levels. newline