重庆芙蓉洞上覆基岩、土壤元素分布特征及其对洞穴滴水水化学影响

Geochemical characteristics of the overlying bedrock and soil,and its impact on hydro-chemistry of the drip waters in the Furong Cave,Chongqing

通过对重庆芙蓉洞上覆基岩和土壤中元素分布特征以及表层岩溶泉水、土壤渗透水和洞穴滴水水化学特征的系统监测,发现Ca2+、Mg2+、Sr2+和SO42-在表层岩溶系统的基岩、土壤、水(土壤渗透水和洞穴滴水)三大载体的运移过程中发生了明显分异。Ca2+、Mg2+和Sr2+在基岩中平均质量比分别为239 949ppm、129 607 ppm和123 ppm,在土壤中分别为37 458 ppm、28 360 ppm和49ppm,土壤渗透水中分别为25.55 mg/L、11.04 mg/L和0.026 mg/L,而在洞穴滴水中分别为64.37 mg/L、37.87 mg/L和0.044 mg/L。Ca、Mg和Sr在土壤剖面中表现出明显的淋溶和淀积作用,其元素含量高低直接影响土壤渗透水元素含量;基岩的元素含量主导了土壤各层位、土壤渗透水及滴水中元素含量。不同滴水点的水其运移的路径、时间和环境条件不同,因此在利用洞穴次生化学沉积物元素地球化学特征来反映洞外环境变化时,需综合考虑各元素在岩-土-水中的分布迁移特征及其与环境因素的相互关系。

Based on element analysis on the overlying bedrock and soil and system monitoring on cations concentration in spring water,soil infiltrating water and cave drip water in the Furong Cave,Chongqing,it is found that the concentration of Ca2＋,Mg2＋,Sr2＋ and SO42-have obvious differentiation during the processes of migration among bedrock,soil and water in epikarst zone.The average mass ratio of Ca2＋、Mg2＋ and Sr2＋ is 239 949 ppm,129 607 ppm and 123 ppm respectively in bedrocks;37 458 ppm,28 360 ppm and 49 ppm in soil;25.55 mg/L,11.04 mg/L and 0.026 mg/L in soil infiltrating water;64.37 mg/L,37.87 mg/L and 0.044 mg/L in cave drip water.Ca,Mg and Sr appear significant eluviation and illuviation on the soil profiles and their content directly control the concentration of corresponding element in soil infiltrating water.Additionally,as the mass source of soil,element composition in the bedrocks have considerable impact on the element content in soil and soil infiltrating water as well as cave drip water.Different cave drip waters have different transfer routes,transfer periods and environmental conditions.So,the migration process and distribution feature in bedrock-soil-water of each element and environment conditions should be considered in the reconstruction of environmental changes with the proxies of elements in speleothems.