A 24-year integrated assessment of fluoride in surface waters of Jinhua, China: spatiotemporal distribution, risk dynamics, and future projections

Fluoride contamination poses a significant global environmental and public health challenge. This study presents a comprehensive analysis of fluoride levels in the surface waters of Jinhua, China, utilizing a unique 24-year monitoring dataset (2001-2024) and a multi-faceted methodological framework. This framework integrated ecological and human health risk assessments with short-term forecasting via a hybrid ARIMA-Holt-Winters model. The multi-year mean fluoride concentration was 0.641 mg/L, 1.68-fold the regional background level but below the national drinking water standard (1.0 mg/L). Pronounced spatial and seasonal variations were observed, with downstream concentrations 137-320% higher than upstream, and dry-season levels elevated by 19.8-24.1%. Ecological risk was generally low (median risk quotient = 0.30). Health risk assessment identified children as the most vulnerable group; a pivotal shift in water source function in 2016 reduced their median hazard quotient(HQ) by approximately 97.0%. Forecasts for 2025-2029 indicate a marginal concentration increase, with risks remaining manageable. This study underscores the efficacy of source-water management and provides a transferable framework for proactive fluoride mitigation in industrial-urban regions.