New evaluation scheme for two-dimensional isotope analysis to decipher biodegradation processes: application to groundwater contamination by MTBE.
New evaluation scheme for two-dimensional isotope analysis to decipher biodegradation processes: application to groundwater contamination by MTBE.
复制标题
DOI：
10.1021/es049650j
复制
发表时间：
2005-08
影响因子：
11.4
通讯作者：
L. Zwank;M. Berg;M. Elsner;T. Schmidt;R. Schwarzenbach;S. Haderlein
中科院分区：
文献类型：
--
作者：
L. Zwank;M. Berg;M. Elsner;T. Schmidt;R. Schwarzenbach;S. Haderlein
化合物的稳定碳和氢同位素的具体分析被用来评估汽油添加剂甲基叔丁基醚（MTBE）和其主要降解产物叔丁醇（TBA）在地下水羽流在工业处置场的命运。我们提出了一种新的方法来评估二维化合物特定的同位素数据的潜力，以确定反应机制，并量化在复杂的现场的生物降解的程度。由于污染物羽流分布广泛，多种MTBE来源，存在许多其他有机污染物，以及复杂的地球化学和水文状况，传统的质量平衡方法不适用。MTBE的同位素组成从污染源区域沿着主要污染物羽流稳定变化（-26.4%至+40.0%（碳）; -73.1%至+60.3%（氢）），表明存在大量生物降解。TBA的恒定碳同位素特征表明该站点没有TBA降解。已发表的MTBE在好氧和缺氧条件下生物降解的碳和氢同位素分馏数据分别进行了检查，并用于确定沿着羽流原位生物降解的性质和程度。二维化合物的具体同位素数据的耦合评价解释了碳和氢分馏数据在一个一致的方式，并表明沿沿着整个羽的MTBE厌氧生物降解。本文提出了一种新的方法，根据理论上的本征碳（12 k/13 k）和氢（1 k/2k）动力学同位素效应（KIE）重新计算经验同位素富集因子（EAF）。碳和氢的KIE值，计算不同的潜在反应机制，意味着厌氧生物降解的MTBE遵循SN 2型反应机制。此外，我们的数据表明，额外的去除过程（ES），如蒸发，有助于整体MTBE去除沿着羽流，这一现象可能是显着的，也为其他领域的网站在热带或亚热带气候与地下水温度升高（25摄氏度）。
Compound-specific analysis of stable carbon and hydrogen isotopes was used to assess the fate of the gasoline additive methyl tert-butyl ether (MTBE) and its major degradation product tert-butyl alcohol (TBA) in a groundwater plume at an industrial disposal site. We present a novel approach to evaluate two-dimensional compound-specific isotope data with the potential to identify reaction mechanisms and to quantify the extent of biodegradation at complex field sites. Due to the widespread contaminant plume, multiple MTBE sources, the presence of numerous other organic pollutants, and the complex biogeochemical and hydrological regime atthe site, a traditional mass balance approach was not applicable. The isotopic composition of MTBE steadily changed from the source regions along the major contaminant plume (-26.4% to +40.0% (carbon); -73.1% to +60.3% (hydrogen)) indicating substantial biodegradation. Constant carbon isotopic signatures of TBA suggest the absence of TBA degradation at the site. Published carbon and hydrogen isotope fractionation data for biodegradation of MTBE under oxic and anoxic conditions, respectively, were examined and used to determine both the nature and the extent of in-situ biodegradation along the plume(s). The coupled evaluation of two-dimensional compound-specific isotope data explained both carbon and hydrogen fractionation data in a consistent way and indicate anaerobic biodegradation of MTBE along the entire plume. A novel scheme to reevaluate empiric isotopic enrichment factors (epsilon) in terms of theoretically based intrinsic carbon (12k/13k) and hydrogen (1k/2k) kinetic isotope effects (KIE) is presented. Carbon and hydrogen KIE values, calculated for different potential reaction mechanisms, imply that anaerobic biodegradation of MTBE follows a SN2-type reaction mechanism. Furthermore, our data suggest that additional removal process(es) such as evaporation contributed to the overall MTBE removal along the plume, a phenomenon that might be significant also for other field sites at tropic or subtropic climates with elevated groundwater temperatures (25 degrees C).