Influence of hydrological and hydrogeochemical parameters on arsenic variation in shallow groundwater of southwestern Taiwan

► We evaluated the effects of hydrogeochemical variables on groundwater As of Taiwan. ► Dynamic factor analysis is adopted to obtain underlying trends of As variations. ► Surface water recharge is responsible for reduction condition and As mobility. ► Redox cycling of Fe and S controlled the As distribution in wet and dry seasons. ► Extensive pumping masked the influence of groundwater level on As variation.