Extensive vadose zone metals and organic contamination remains at many former industrial and defense manufacturing sites, and effective remedial solutions are needed to slow or prevent its migration to groundwater. In this study, the application of gaseous substrates to stimulate microbial respiratory reduction of comingled radioisotopes and nitrate under unsaturated conditions was examined for possible application at the Hanford Site, a former nuclear production facility in southeastern WA, USA. First, screening studies were performed to qualitatively measure the sediment respiratory response to 14 gaseous or volatile organic substrates at two moisture contents, 4% and 8%. Volatile substrates produced the strongest respiratory response, among them were butyrate, pentane, butyl acetate. Ethane and butane were the most effective gaseous substrates but only at 8% water content. Hanford sediment from two waste sites with distinctive chemistries were wetted to 7% moisture content, packed into columns, and treated with ethane or butane. After 4 weeks, columns were then leached to quantify retardation in the mobility of aqueous contaminant concentrations compared to no gas control columns. Treatment with both gases resulted in >80% removal of Cr from the aqueous phase. However, NO3 concentration and a waste sites exposure history to NO3 had a major effect on U and Tc reduction. Incomplete nitrate reduction outcompeted U and Tc in waste site sediments having limited prior exposure to NO3. Conversely, waste site sediments co-contaminated with NO3 were able to achieve highly reduced conditions resulting in complete denitrification of NO3, and delayed leaching of U and Tc. This implied effective reduction of both contaminants to less mobile species. This study demonstrates that unsaturated vadose sediments at Hanford waste sites have the capacity for a sustained respiratory response to gaseous substrate injection, which could potentially be deployed as part of an overall strategy to reduce the flux of long-lived radionuclides to groundwater at Hanford and other legacy waste sites.

中文翻译：

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评估气态基质对不饱和地下沉积物中污染物混合物的微生物固定作用。

大量的渗流带金属和有机污染物仍留在许多以前的工业和国防制造场所，需要有效的补救措施来减缓或防止其迁移到地下水中。在这项研究中，研究了在不饱和条件下使用气态底物刺激微生物放射性混合的放射性同位素和硝酸盐的减少，以在汉福德工地（美国华盛顿州东南部的一家前核生产设施）中进行了可能的应用。首先，进行筛选研究以定性地测量在两种水分含量分别为4％和8％时，沉积物对14种气态或挥发性有机底物的呼吸反应。挥发性底物产生最强的呼吸反应，其中包括丁酸酯，戊烷，乙酸丁酯。乙烷和丁烷是最有效的气态底物，但含水量仅为8％。将来自两个具有独特化学性质的废料场的汉福德沉淀物润湿至7％的水分含量，装入柱中，并用乙烷或丁烷进行处理。4周后，与没有气体控制的色谱柱相比，对色谱柱进行浸提以量化水污染物浓度迁移率的延迟。用两种气体处理导致从水相中去除> 80％的Cr。但是，NO3浓度和废物场所接触NO3的历史对U和Tc的降低有重大影响。硝酸盐还原不完全超过了先前暴露于NO3有限的废物现场沉积物中的U和Tc。反过来，与NO3共同污染的废物现场沉积物能够实现高度还原的条件，从而使NO3完全脱氮，并延迟U和Tc的浸出。这意味着将两种污染物有效地减少为流动性较小的物质。这项研究表明，汉福德废料场的不饱和渗流沉积物具有对气态底物注入持续呼吸作用的能力，这有可能被部署为减少汉福德等地长期放射性核素流向地下水的总体策略的一部分。遗留垃圾场。