Deciphering Groundwater Hydrogeochemical Evolution and Anthropogenic Influences in Xingtai, North China: Insights From Multivariate Analysis, Nitrate Indicators, and Health Risk Assessment.

Understanding natural hydrogeochemical processes and anthropogenic disturbances is essential for sustainable groundwater management. This study investigated groundwater hydrogeochemical evolution in Xingtai, North China, using hydrochemical data from three campaigns (2016: n = 61; 2022: n = 89; 2024: n = 48) via integrated approaches including Piper and Gibbs diagrams, ion ratios, chloro-alkaline indices (CAI), principal component analysis (PCA), and nitrate-based health risk assessment. Groundwater was predominantly Ca-HCO3 type but shifted toward Ca-SO4, with Ca-HCO3 decreasing from 83.6% to 58.3% and Ca-SO4 increasing from 16.4% to 37.5%. Rock weathering dominated groundwater chemistry in every campaign, with essentially all samples plotting in the rock-weathering domain of the Gibbs diagram (100% of 2016 samples, 95.5% of 2022 samples, and 97.9% of 2024 samples). CAI analysis revealed a shift from dominantly direct ion exchange in 2016-2022 toward a more balanced regime with reverse ion exchange becoming more prominent in 2024. The proportion of samples with unacceptable non-carcinogenic risks (HQ ≥ 1) for children rose from none in 2022 to 2.1% in 2024, confined to persistent, co-located hot spots, underscoring the need for targeted nitrate management.