Comprehensive assessment on groundwater quality, pollution characteristics, and ecological health risks under seasonal thaws: Spatial insights with Monte Carlo simulations

Groundwater pollution is a major environmental concern and may persist under diverse ecological conditions. This study describes the seasonal impacts on pollution characteristics coupled with the degree of human health risks in groundwater. For this purpose, a highly populated city of Pakistan, Lahore was planned and about 50 groundwater samples were collected during the summer and winter seasons in 2021 and 2022. Various physiochemical parameters (pH, EC, TDS, and hardness), cations, anions, and toxic metals (As, Cd, Co, Cr, Mn, Ni, and Pb) were analyzed to evaluate the seasonal impacts on the groundwater quality. Besides, a Monte Carlo simulation model and sensitivity analysis were performed to obtain a high-level accuracy in cancer risk estimation. Results revealed that physiochemical parameters, cations, and anions in most of the samples were within the WHO limit. However, the heavy metals concentration was higher in winter than in summer season. Most metals showed a significant spatial variability were found in older settlements and densely populated areas of the city for both seasons. Factor analysis (FA) and cluster analysis (CA) revealed a significant anthropogenic contribution to Ni, Co, Cd, Cu, Cr, and Pb contaminations in groundwater. Drinking water quality indices (DWQI) and heavy metal pollution indices (HMEI) points in both seasons revealed a poor to moderated pollution pattern. Pollution load index (PLI) and potential ecological risk index (PERI) indicated the medium pollution with low risks. Through Monte Carlo simulation at 95% confidence level revealed that carcinogenic risks associated with As, Cr, Cd, and Ni has exceeded from safer limits. Consequently, winter season was perceived more sensitive owing to the substantial increase of pollutants proclamation in groundwater and posturing a serious threat to humans. Hence, instant remedial actions are suggested to ensure safe drinking water.