Spatial characteristics and driving factors of groundwater hydrochemistry and heavy metals in peri-urban agricultural areas of in Southwest China

The hydrogeochemical evolution of groundwater in peri-urban agricultural areas is influenced by the convergence of natural processes, agricultural practices, and industrial activities. Understanding the combination of these influences is essential for assessing groundwater quality and human health risks. The study, taking the peri-urban agricultural areas in Guixi, China as a case, investigated the major components and heavy metals in groundwater and analyzed their spatial distribution patterns, sources, controlling factors, and human health risks. HCO3- and Ca2+ are the most prevalent anions and cations in groundwater, with average concentrations of 136.74 and 34.07 mg/L, respectively. Heavy metal concentrations follow the sequence: Fe > Ba > Mn > Al > As > Pb. Groundwater compositions exhibit moderate to strong spatial variability, and most of the groundwater in the area presents moderate to significant health risks, with Cl-, As, Al, and Mn being the primary risk factors. Rock weathering by carbonic acid and industrial waste gypsum dissolution emerge as primary factors driving groundwater hydrogeochemical evolution. Fe and Mn correlate with SO42-, sourced from industrial waste gypsum, while As and Al correlate with HCO3-, indicating a geological origin. Pb originates from transportation inputs, and Ba exhibits contrasting correlations with NO3- and SO42-, reflecting the dual influence of agricultural and industrial activities. These findings highlight groundwater hydrogeochemistry evolutions in peri-urban agricultural areas are intricately influenced by the combination of natural processes and a variety of human activities, rather than just the additive effect of these factors.