Transverse hydrodynamic dispersion effects on isotope signals in groundwater chlorinated solvents' plumes.
Transverse hydrodynamic dispersion effects on isotope signals in groundwater chlorinated solvents' plumes.
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DOI：
10.1021/es301058z
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发表时间：
2012-06
影响因子：
11.4
通讯作者：
B. V. van Breukelen;M. Rolle
中科院分区：
文献类型：
--
作者：
B. V. van Breukelen;M. Rolle
横向水动力弥散对地下水污染羽状流中变换诱导的化合物特定同位素分析（CSIA）信号的影响进行了评估，反应输运模型适应扩散诱导的同位素分馏（DIF）和实施不同的参数化的局部横向弥散。该模型再现了先前发表的现场数据，显示出在非降解PCE羽流的边缘处的负碳同位素模式（-2 ‰）。我们的研究扩展到反应性运输的情况下，考虑氯乙烯作为模型化合物和评估，通过详细的敏感性分析，耦合效应的横向水动力分散（有和没有DIF）和有氧边缘降解的碳和氯同位素比值的演变。转化诱导的正同位素信号随着离源的距离和更高的降解速率而逐渐衰减。DIF对总体同位素信号衰减的影响在源附近最大，并且对于地下水流速、横向分散系数、分子量、速率常数和降解反应的同位素分馏因子α的低值最大。忽略DIF的模型低估了实际α。氯的DIF效应大约是碳的两倍，加上氧化的α较低，导致烟羽边缘的VC强烈的氯CSIA消耗。
The effects of transverse hydrodynamic dispersion on altering transformation-induced compound-specific isotope analysis (CSIA) signals within groundwater pollution plumes have been assessed with reactive transport modeling accommodating diffusion-induced isotope fractionation (DIF) and implementing different parameterizations of local transverse dispersion. The model reproduced previously published field data showing a negative carbon isotope pattern (-2 ‰) at the fringes of a nondegrading PCE plume. We extended the study to reactive transport scenarios considering vinyl chloride as a model compound and assessing, through a detailed sensitivity analysis, the coupled effects of transverse hydrodynamic dispersion (with and without DIF) and aerobic fringe degradation on the evolution of carbon and chloride isotope ratios. Transformation-induced positive isotope signals were increasingly attenuated with distance from the source and higher degradation rate. The effect of DIF on the overall isotope signal attenuation was greatest near the source and for low values of groundwater flow velocity, transverse dispersion coefficient, molecular weight, rate constant, and isotope fractionation factor, α, of the degradation reaction. Models disregarding DIF underestimate the actual α. The approximately twice larger DIF effect for chlorine than for carbon together with the low α for oxidation resulted in strong chlorine CSIA depletions for VC at the plume fringe.