Groundwater nitrate contamination around a municipal landfill: hydrogeochemical insights, source identification, and health risk assessment.

Abstract

This study intended to investigate the hydrochemical characteristics and sources of nitrate (NO₃-N) in groundwater, and to evaluate the potential health risks in the vicinity of the Jiangcungou landfill in Northwest China. To fulfill these purposes, a total of 41 groundwater sourced primarily from the phreatic aquifer were collected and analyzed. The study found that NO₃-N concentrations in the area varied between 0.57 mg/L and 47.69 mg/L, with 26.67% of samples exceeded China's drinking water threshold (20 mg/L as N) and 31.7% surpassing the WHO guideline (11.3 mg/L as N). The background level of NO₃-N was estimated to be 1.11 mg/L through a probabilistic approach and was exceeded by 85.4% of the samples. Ionic ratios and land use analysis highlighted significant NO₃-N contributions from domestic sewage, industrial, and agricultural sources. These findings were reinforced by principal component analysis (PCA) and the absolute principal component score-multiple linear regression (APCS-MLR) model, which attributed 40.12% of NO₃-N to domestic sewage and wastewater and 7.78% to industrial and agricultural activities. Although Jiangcungou landfill is not the primary contributor, lingering leachate still affects groundwater quality, especially in nearby wells with high NO₃-N concentrations. Furthermore, health risk assessments indicated significant NO₃-N associated non-carcinogenic risks (HQ_oral > 1) for infants (63.4%), children (46.3%), females (41.5%), and males (34.1%). The Monte Carlo Simulation further supports these findings, highlighting elevated risks, especially for infants and children. This study provides important scientific support and guidance for implementing sustainable groundwater management practices and the protection of human health in affected areas.