龙子祠泉域岩溶地下水水化学特征及成因

龙子祠岩溶水是临汾市工农业生产和城市水源地.查明污染特征及成因,对合理开发利用岩溶地下水资源与泉域生态保护具有重要的意义.本研究以龙子祠泉域岩溶地下水系统为研究对象,通过样品采集与同位素分析,综合运用水化学(Durov图、离子比例、Gibbs图、硫同位素和氢氧同位素)方法分析地下水水化学特征.揭示了龙子祠泉水的水文地球化学特征和环境同位素特征.龙子祠泉域岩溶地下水水化学场从深埋滞留区到补给区到径流、排泄区具有明显的分带性.龙子祠岩溶地下水主要为SO_4·HCO_3-Ca和SO_4·HCO_3-Ca·Mg型水,SO_4~(2-)值为61.6～1 503 mg·L~(-1),均值为481.4 mg·L~(-1),SO_4~(2-)超标比例为70.3%.其SO_4~(2-)主要来源于石膏的溶解和煤系地层FeS_2氧化,其中龙子祠泉水中SO_4~(2-)源于FeS_2氧化的比例为20.2%.依据氢氧、硫同位素得出70%的岩溶地下水不同程度的受到煤矿酸性水的污染.利用Phreeqc软件模拟得出:研究区水化学特征主要受白云石、岩盐和石膏的溶解作用与去白云石化作用.

Hydrochemical Characteristics and Formation Causes of Ground Karst Water Systems in the Longzici Spring Catchment

The water of the Longzici Spring catchment is the source of industrial, agricultural, and urban domestic water in Linfen City, Shanxi Province. It is of great significance to identify the sources and influencing factors of karst water resources for their development and utilization, and the protection of the ecological environment. Taking the karst groundwater in the Longzici Spring Area as the research object, systematic sample collection and isotope analysis were carried out. Hydrochemistry methods (Durov diagram, ion ratio system, Gibbs diagram, hydrogen and oxygen isotopes, and sulfur isotopes) were used to analyze the hydrochemical characteristics of groundwater. The hydrogeochemical and environmental isotopic characteristics of Longzici Spring water are revealed. The hydrochemical field of karst groundwater in the Longzici Spring domain has obvious zonation, from the deep buried detention area to the supply area to the runoff and discharge area. The hydrochemical types of karst groundwater detention area are SO₄-Ca and SO₄-Ca·Mg, with total dissolved solids (TDS) of 960.5-2340 mg·L^-1; the supply area is HCO₃-Ca·Mg and HCO₃·SO₄-Ca·Mg, with TDS of 340.5-562 mg·L^-1; and the runoff and discharge areas are SO₄·HCO₃-Ca·Mg·Na, SO₄·HCO₃-Ca, and SO₄·HCO₃-Ca·Mg, with TDS of 494.0-1168.5 mg·L^-1. The karst groundwater is mainly SO₄·HCO₃-Ca and SO₄·HCO₃-Ca·Mg type water. The content range of sulfate ions is 61.6-1503 mg·L^-1, with an average of 481.4 mg·L^-1. A total of 70.3% of the karst groundwater SO₄^2- samples exceed the standard. The sulfate ions in karst groundwater mainly come from the dissolution of gypsum in the Ordovician aquifer and the oxidation of pyrite in a coal aquifer. The ratio of sulfate ions in the Longzici Spring catchment that come from pyrite oxidation in water is 20.2%. According to the analysis of hydrogen, oxygen and sulfur isotopes, 70% of karst groundwater is polluted by the acid water of coal mines to different degrees. Using the software PHREEQC, it is concluded that the hydrochemical characteristics of the study area are mainly affected by dissolution and dedolomitization, rock salt, and gypsum.