Spatio-temporal assessment of heavy metal contamination in groundwater along Madhuana drain, Faisalabad: source apportionment and health risk analysis.

Abstract

Trace metals are among the most critical pollutants in wastewater, contributing to severe groundwater contamination, particularly near wastewater canals. Study novelty is that seasonal variations of groundwater metals and their associated sources through the Positive Matrix Factorization Model, with health risks through skin exposure, have not been well understood in Faisalabad along wastewater drains. This study investigates groundwater quality in the Madhuana drain and its sub-drains (Satiana and Khanuana) by examining chemical parameters, water quality indices, and trace metal concentrations (Cd, Cr, Cu, Mn, Ni, Pb, and Zn) in samples collected during the summer (n = 21) and winter (n = 21) seasons of 2023-2024. The heavy metals primary sources were anthropogenic, such as industrial effluent discharge, household waste, and agricultural runoff. Based on seasonal results, physico-chemical, biological parameters and trace metals concentrations were higher in the winter than summer season, and these parameters exceeded permissible limits of national and international guidelines. Spatial contamination follows a pattern: Satiana drain (high contamination), Madhuana drain (medium contamination), and Khanuana drain (low contamination). Satiana, Madhuana, and Khanuana drains groundwater quality have been classified as "very poor", "poor", and "slightly poor", respectively, making the water unsuitable for human intake. Health risk analyses reveal low non-carcinogenic risks (HQ < 1) from ingesting and dermal exposure, with children at higher risk than adults. During both seasons, the carcinogenic risk for Cd, Cr, Ni, and Pb was under acceptable ranges (TCR < 1). The research is based on a one-year data set, which may not have captured long-term trends, and it is limited to heavy metal contamination, not including organic and microbial contaminants. Future studies with wider monitoring as well as detailed pollutant analysis will be required. For ensuring drinking water safety, regular monitoring and remedial measures must be adopted.