Abstract: Approximately 156 countries worldwide have detected sulfate concentrations exceeding permissible levels in groundwater.Sulfate contamination in groundwater poses a threat to human health and the balance of ecosystems.Conducting monitoring and source apportionment of sulfate in groundwater is crucial for the control of groundwater pollution sources.A study on the source apportionment of sulfate at groundwater environmental quality monitoring sites was conducted using a combination of methods including field investigations,borehole television detection,and hydrochemical and isotopic tracing.The results indicate that in the localized water environment of the target monitoring site,sulfate concentrations are relatively high during both dry and wet seasons,with Sr isotope ratios being relatively low and concentrated in the range of 0.711-0.712.The sulfate isotope composition is relatively enriched,with δ³⁴S-SO₄^2- distribution ratios exceeding 15‰ and δ¹⁸O-SO₄^2- distribution ratios exceeding 10‰.Multiple lines of evidence from hydrochemistry and isotopes suggest that the primary source of sulfate in the groundwater at the target groundwater monitoring well is the dissolution of evaporative rock salt,with a certain contribution from sulfide oxidation,which is consistent with the source classification results of material sources obtained from principal component analysis.This study provides methodological guidance for analyzing the causes of groundwater exceedances in small-scale areas around environmental quality monitoring wells and offers important scientific support for groundwater environmental management.