Department of Civil and Environmental Engineering, 4105 Seamans Center, The University of Iowa, Iowa City, IA, 52242, USA.
Geosyntec Consultants, Inc, 10211 Wincopin Circle, 4th Floor, Columbia, MD, 21044, USA.
Environ Sci Pollut Res Int. 2022 Aug;29(37):56154-56167. doi: 10.1007/s11356-022-19755-1. Epub 2022 Mar 24.
Chlorinated ethene (CE) groundwater contamination is commonly treated through anaerobic biodegradation (i.e., reductive dechlorination) either as part of an engineered system or through natural attenuation. Aerobic biodegradation has also been recognized as a potentially significant pathway for the removal of the lower CEs cis-1,2-dichloroethene (cDCE) and vinyl chloride (VC). However, the role of aerobic biodegradation under low oxygen conditions typical of contaminated groundwater is unclear. Bacteria capable of aerobic VC biodegradation appear to be common in the environment, while aerobic biodegradation of cDCE is less common and little is known regarding the organisms responsible. In this study, we investigate the role of aerobic cDCE and VC biodegradation in a mixed contaminant plume (including CEs, BTEX, and ketones) at Naval Air Station North Island, Installation Restoration Site 9. Sediment and groundwater collected from the plume source area, mid-plume, and shoreline were used to prepare microcosms under fully aerobic (8 mg/L dissolved oxygen (DO)) and suboxic (< 1 mg/L DO) conditions. In the shoreline microcosms, VC and cDCE were rapidly degraded under suboxic conditions (100% and 77% removal in < 62 days). In the suboxic VC microcosms, biodegradation was associated with a > 5 order of magnitude increase in the abundance of functional gene etnE, part of the aerobic VC utilization pathway. VC and cDCE were degraded more slowly under fully aerobic conditions (74% and 30% removal) in 110 days. High-throughput 16S rRNA and etnE sequencing suggest the presence of novel VC- and cDCE-degrading bacteria. These results suggest that natural aerobic biodegradation of cDCE and VC is occurring at the site and provide new evidence that low (< 1 mg/L) DO levels play a significant role in natural attenuation of cDCE and VC.
氯代乙烯（CE）地下水污染通常通过厌氧生物降解（即还原脱氯）来处理，无论是作为工程系统的一部分还是通过自然衰减。有氧生物降解也被认为是去除较低的 CEs 顺式-1,2-二氯乙烷（cDCE）和氯乙烯（VC）的潜在重要途径。然而，在受污染地下水典型的低氧条件下，有氧生物降解的作用尚不清楚。能够进行有氧 VC 生物降解的细菌在环境中似乎很常见，而 cDCE 的有氧生物降解则不太常见，对于负责的生物也知之甚少。在这项研究中，我们调查了有氧 cDCE 和 VC 生物降解在海军航空站北岛混合污染物羽流（包括 CEs、BTEX 和酮类）中的作用，该站点是安装恢复站点 9。从羽流源区、羽流中部和海岸线采集的沉积物和地下水用于在完全有氧（8mg/L 溶解氧（DO））和亚缺氧（<1mg/L DO）条件下制备微宇宙。在海岸线微宇宙中，VC 和 cDCE 在亚缺氧条件下迅速降解（<62 天内去除率分别为 100%和 77%）。在亚缺氧 VC 微宇宙中，生物降解与有氧 VC 利用途径的一部分功能基因 etnE 的丰度增加了>5 个数量级有关。在 110 天内，在完全有氧条件下，VC 和 cDCE 的降解速度较慢（去除率分别为 74%和 30%）。高通量 16S rRNA 和 etnE 测序表明存在新型 VC 和 cDCE 降解细菌。这些结果表明，该地点正在发生自然有氧 cDCE 和 VC 的生物降解，并提供了新的证据，表明低（<1mg/L）DO 水平在 cDCE 和 VC 的自然衰减中起着重要作用。
