Characteristics of sulfur isotope in water bodies near the Zhaoyuan gold mine area and its indicative function of pollution sources

Stable isotopes have become an important technical method for analyzing pollution sources in mining areas due to their fingerprint effect. In the Zhaoyuan gold mine area, most of the studies were based on experiments or hydrochemical data combined with hydrogeological conditions. It is difficult to analyze the compositions of pollution sources. This paper is the first time to analyze the hydrochemical characteristics and pollution causes of the Zhaoyuan gold mine area by combining the ²H, ¹⁸O and ³⁴S isotopes of water bodies and hydrochemical methods. 32 samples were collected, including 16 groundwater samples, 10 surface water samples, 3 beneficiation wastewater samples, 2 tailing leachate samples and 1 pit water sample. Based on the analyses, the surface water and groundwater with close hydraulic connection in the mining area are mainly recharged by precipitation. The main hydrochemical components are from the oxidation of sulfide minerals, the dissolution of silicate minerals and the influence of human activities. The main hydrochemical types are of SO₄—Ca and SO₄—Na, the main anion is SO₄^2-, and the variation of NO₃^- and Cl^- in surface water and groundwater is large in space. The contents of sulfate in the surface water are generally high, and the sulfate pollution is serious. The high value areas appear near the Linglong gold mine, Jinchiling gold mine and Zhangxing Town, while the high value areas of groundwater appear near the Linglong gold mine, and the concentrations of SO₄^2- decreases gradually along the runoff direction. The value of δ³⁴S in the surface water ranges between 1.8‰ and 9.8‰, and that in groundwater, between 2.7‰ and 9.6‰. The groundwater and surface water are obviously affected by the Linglong granite, Jiaodong rock group and sulfide of Linglong gold deposit. In the process of groundwater runoff, there is the phenomenon of groundwater pollution caused by surface water infiltration. In addition, the discharge of industrial and domestic sewage is also the main reason for the increase of sulfate contents. Sulfur isotope can trace the source and characteristics of sulfate pollution in the gold mining area, and it is an effective tool for tracing and evaluating the groundwater pollution caused by mining activities.