Microbial Response Following a Carboxymethyl Cellulose-Stabilized Sulfidated Nano Zero-Valent Iron Injection: A Long-Term Field Study

Sulfidated nano zero-valent iron (S-nZVI), recognized
for its high
remediation efficiency, was evaluated in a field trial to assess its
impact on microbial communities in subsurface environments contaminated
with chlorinated volatile organic compounds (cVOCs). Over a 1.5 year
monitoring period, groundwater samples were collected to track microbial
responses following the injection of carboxymethyl cellulose (CMC)-stabilized
and dithionite-sulfidated nZVI (CMC-S-nZVI). The study observed pronounced
and prolonged biostimulatory effects at locations receiving notable
amounts of CMC-S-nZVI, as evidenced by increased DNA and bacterial
concentrations. 16S rRNA gene sequencing revealed the selective enrichment
of organohalide-respiring bacteria (OHRB), including Dehalococcoidaceae,
which played a crucial role in cVOCs biotic dechlorination. Numerical
ecological analyses indicated a sustained shift in microbial community
structures post injection. Additionally, Fe3+/sulfur-reducing
OHRB, including some strains of Geobacter, Sulfurospirillum, and Desulfitobacterium, emerged as major components of
the total bacterial population. These microorganisms likely utilized
both injected and native sulfur and iron species to form iron sulfides,
potentially contributing to abiotic dechlorination. This microbially
mediated process may explain the complete dechlorination of cVOCs
with minimal vinyl chloride accumulation. This study demonstrates
the long-term adaptation of microorganisms to the injected CMC-S-nZVI
and its effectiveness in removing cVOCs through a combination of abiotic
and biotic processes.

硫化纳米零价铁（Sulfidated nano zero-valent iron, S-nZVI）凭借极高的修复效能，本研究通过野外试验评估其对氯化挥发性有机化合物（chlorinated volatile organic compounds, cVOCs）污染地下环境中微生物群落的影响。在为期1.5年的监测周期内，研究人员采集地下水样本，以追踪羧甲基纤维素（carboxymethyl cellulose, CMC）稳定化连二亚硫酸盐硫化纳米零价铁（CMC-S-nZVI）注入后微生物群落的响应变化。研究发现，在接收大量CMC-S-nZVI的区域，出现了显著且持久的生物刺激效应，具体表现为DNA总量与细菌浓度均显著提升。16S rRNA基因测序结果显示，有机卤呼吸细菌（organohalide-respiring bacteria, OHRB）得到了选择性富集，其中脱卤球菌科（Dehalococcoidaceae）在氯化挥发性有机化合物的生物脱氯过程中发挥了关键作用。数值生态学分析表明，注入CMC-S-nZVI后，微生物群落结构发生了持续性改变。此外，三价铁/硫酸盐还原型有机卤呼吸细菌（包含部分地杆菌属、硫螺旋菌属与脱卤杆菌属菌株）成为总细菌群落的主要组成部分。这类微生物可能同时利用注入的与原位存在的硫、铁元素生成硫化铁，进而可能参与非生物脱氯过程。这种微生物介导的过程可解释氯化挥发性有机化合物被完全脱氯且氯乙烯副产物积累量极低的现象。本研究证实，微生物可长期适应注入的CMC-S-nZVI，且该材料可通过非生物与生物协同过程高效去除氯化挥发性有机化合物。