Einsiedl Florian, Mayer Bernhard
Institute of Groundwater Ecology, GSF-National Research Center for Environment and Health, Ingolstädter Landstrasse 1, D-85764 Neuherberg, Germany.
Environ Sci Technol. 2005 Sep 15;39(18):7118-25. doi: 10.1021/es050426j.
Chemical and isotope analyses on groundwater sulfate and 3H measurements on groundwaterwere used to determine the sulfate sources and sulfur transformation processes in a heterogeneous karst aquifer of the Franconian Alb, southern Germany. Sulfate was found to be derived from atmospheric deposition. Young groundwater was characterized by high sulfate concentrations and delta34S values similar to those of recent atmospheric sulfate deposition. However, the delta18O values of groundwater SO4(2-) were depleted by several per mil with respect to those of atmospheric deposition. This isotopic shift is indicative of mineralization of carbon-bonded S in the vadose zone of the karst system. In groundwater with mean residence times of more than 60 years, a trend of increasing delta34S values and delta18O values with decreasing sulfate concentrations was observed. This trend could not be solely explained by preindustrial atmospheric sulfate deposition with higher delta34S values, and hence, we conclude that bacterial (dissimilatory) sulfate reduction in the porous matrix of the karst aquifer must have occurred. This process has the potential to contribute to long-term biodegradation of contaminants in the porous rock matrix representing the dominantwater reservoir of the fissured porous karst aquifer.
通过对地下水硫酸盐进行化学和同位素分析以及对地下水进行³H测量，来确定德国南部弗兰肯阿尔卑斯山非均质岩溶含水层中的硫酸盐来源和硫转化过程。研究发现，硫酸盐来源于大气沉降。年轻地下水的特征是硫酸盐浓度高，且δ³⁴S值与近期大气硫酸盐沉降的δ³⁴S值相似。然而，地下水中SO₄²⁻的δ¹⁸O值相对于大气沉降的δ¹⁸O值贫化了几个千分点。这种同位素偏移表明岩溶系统包气带中碳键结合的硫发生了矿化作用。在平均停留时间超过60年的地下水中，观察到随着硫酸盐浓度降低，δ³⁴S值和δ¹⁸O值呈增加趋势。这种趋势不能仅用具有较高δ³⁴S值的工业化前大气硫酸盐沉降来解释，因此，我们得出结论，岩溶含水层多孔基质中一定发生了细菌（异化）硫酸盐还原作用。这一过程有可能促进多孔岩石基质中污染物的长期生物降解，而多孔岩石基质是裂隙多孔岩溶含水层的主要水源。
