Miao Ziheng, Carreón-Diazconti Concepcion, Carroll Kenneth C, Brusseau Mark L
Department of Soil, Water and Environmental Science, University of Arizona, 429 Shantz Building #38, P.O. Box 210038, Tucson, AZ, USA; Department of Hydrology and Water Resources, University of Arizona, Harshbarger Building #11, Tucson, AZ, USA.
Engineering Institute, Autonomous University of Baja California, Mexicali, Baja California, Mexico.
J Contam Hydrol. 2014 Aug;164:240-50. doi: 10.1016/j.jconhyd.2014.06.010. Epub 2014 Jun 27.
The impact of electron-donor addition on sulfur dynamics for a groundwater system with low levels of metal contaminants was evaluated with a pilot-scale biostimulation test conducted at a former uranium mining site. Geochemical and stable-isotope data collected before, during, and after the test were analyzed to evaluate the sustainability of sulfate reducing conditions induced by the test, the fate of hydrogen sulfide, and the impact on aqueous geochemical conditions. The results of site characterization activities conducted prior to the test indicated the absence of measurable bacterial sulfate reduction. The injection of an electron donor (ethanol) induced bacterial sulfate reduction, as confirmed by an exponential decrease of sulfate concentration in concert with changes in oxidation-reduction potential, redox species, alkalinity, production of hydrogen sulfide, and fractionation of δ(34)S-sulfate. High, stoichiometrically-equivalent hydrogen sulfide concentrations were not observed until several months after the start of the test. It is hypothesized that hydrogen sulfide produced from sulfate reduction was initially sequestered in the form of iron sulfides until the exhaustion of readily reducible iron oxides within the sediment. The fractionation of δ(34)S for sulfate was atypical, wherein the enrichment declined in the latter half of the experiment. It was conjectured that mixing effects associated with the release of sulfate from sulfate minerals associated with the sediments, along with possible sulfide re-oxidation contributed to this behavior. The results of this study illustrate the biogeochemical complexity that is associated with in-situ biostimulation processes involving bacterial sulfate reduction.
通过在一个 former uranium mining site 进行的中试规模生物刺激试验，评估了电子供体添加对低金属污染物含量地下水系统中硫动力学的影响。对试验前、试验期间和试验后收集的地球化学和稳定同位素数据进行了分析，以评估试验诱导的硫酸盐还原条件的可持续性、硫化氢的归宿以及对水地球化学条件的影响。试验前进行的现场表征活动结果表明不存在可测量的细菌硫酸盐还原。电子供体（乙醇）的注入诱导了细菌硫酸盐还原，这通过硫酸盐浓度的指数下降与氧化还原电位、氧化还原物种、碱度、硫化氢产生以及 δ(34)S-硫酸盐分馏的变化相一致得到证实。直到试验开始几个月后才观察到高的、化学计量当量的硫化氢浓度。据推测，硫酸盐还原产生的硫化氢最初以硫化铁的形式被封存，直到沉积物中易还原的铁氧化物耗尽。硫酸盐的 δ(34)S 分馏是非典型的，其中在实验后半段富集程度下降。据推测，与沉积物相关的硫酸盐矿物中硫酸盐释放相关的混合效应以及可能的硫化物再氧化导致了这种行为。本研究结果说明了与涉及细菌硫酸盐还原的原位生物刺激过程相关的生物地球化学复杂性。
