贵州普定灯盏河岩溶泉的硫同位素季节变化特征

通过对贵州普定后寨地下河补给区的灯盏河岩溶泉为期1年的泉水水文地球化学特征与水中SO2-4的硫同位素组成及季节性变化规律的分析,揭示灯盏河岩溶泉泉水中硫酸盐的来源及形成机理.结果表明:灯盏河岩溶泉的水化学类型主要为HCO-3·SO2-4 Ca2+型,具有很高的硫酸盐浓度,且变化幅度较大,SO2-4浓度为0.35~8.76mmol·L-1;灯盏河泉水SO2-4的硫同位素组成为(3.80~25.76)×10-3,反映泉水的硫同位素组成主要受土壤有机硫氧化和石膏岩层溶解的控制;泉水硫同位素组成季节性变化明显,表现为旱季大于雨季,且旱季变化平缓,主要受石膏溶解的控制,而雨季变化幅度较大,反映雨季地下水硫酸盐土壤有机硫源贡献的增加及其季节性差异.

Seasonal Variation of Sulfur Isotope in Dengzhanhe Karst Spring of Puding,Guizhou

The concentration of sulfate is high in Dengzhanhe karst spring located in the recharge area of Houzhai underground river of Puding,Guizhou.Hydrogeochemistry characteristics of the spring,sulfur isotopic composition of SO2-4 and their seasonal changes were analyzed during a hydrological year,and the source and formation mechanism of sulfate in the spring were revealed.The results showed that the hydrochemical type of Dengzhanhe karst spring was HCO-3·SO2-4-Ca2+,the concentration of sulfate was very high and the range of variation was significant,the concentration of SO2-4 was 0.35-8.76 mmol·L-1;the sulfur isotopic composition of SO2-4 in the spring was(3.80-25.76)×10-3,and indicated that the sulfur isotopic composition was mainly controlled by dissolution of gypsum and oxidation of organic sulfur in soil;seasonal variation of sulfur isotopic composition was remarkable,and indicated that sulfur isotopic composition in dry season was more than that in rainy season,and the change of composition in dry season was small and mainly controlled by the dissolution of gypsum,but the change in rainy season was large and reflected the increase of organic sulfur for underground sulfate soil and its seasonal difference.