Groundwater contamination, fate, and transport of fluoride and nitrate in Western Jilin, China: Implications for water quality and health risks

This study investigates groundwater quality in confined and unconfined Quaternary aquifers in Western Jilin, focusing on key parameters: fluoride and nitrate. Most physicochemical parameters adhered to established guidelines; however, fluoride in unconfined Quaternary aquifers increased from 1.50 mg/L in 2010 to 1.88 mg/L in 2020, while nitrate reached 12.96 mg/L and TDS ranged between 2150 and 2564 mg/L. Confined Quaternary aquifers generally met quality standards with lower pollutant levels. The primary groundwater types were identified as Ca 2+ + Mg 2+ − HCO₃ − + CO₃ 2− and Na + + K + − HCO₃ − + CO₃ 2− , indicating enhanced cation exchange processes. The temporal analysis showed an increase in unsuitable drinking water samples in confined aquifers from 2.70 % in 2000, 11.11 % in 2010 and 30.56 % in 2020, and in unconfined aquifers at 10.20 %, 12.73 %, and 10.42 % for 2000, 2010, and 2020, respectively. Groundwater pollution zones indicate an increase in contamination in confined aquifers and widespread fluoride contamination in unconfined aquifers. Health risks assessment revealed significant risks: fluoride posed high risks, and nitrate was moderate risk, particularly for infants, followed by children and adults. Hazard index trends indicated an increase in samples exceeding recommended limits for infants, rising in confined aquifers from 70.27 % in 2000 to 98.96 % in 2020, and in unconfined aquifers from 79.59 % to 98.96 % over the same period. This trend highlights higher contamination risks in unconfined aquifers. Similar findings were observed in spatial distribution analyses, which confirmed heightened aquifer vulnerability due to industrial activities and agricultural practices. The study emphasizes the need for targeted strategies to address fluoride and nitrate contamination in susceptible aquifer zones. • Fluoride (F − ) concentrations increased in Confined Quaternary Aquifer (CQA) and Unconfined Aquifer (UQA). • Nitrate (NO₃ − ) concentrations reached a maximum of 12.96 mg/L in UQA risk zones by 2020. • By 2020, 30.56 % of CQA and 10.42 % of UQA samples were unsuitable for drinking. • Groundwater pollution zones increased, while safe zones declined from 2000 to 2020. • Health risks ranked: infants > children > adults.