羟基氧化铁对太湖底泥中多氯联苯微生物厌氧脱氯的影响

多氯联苯（PCBs）的微生物厌氧脱氯过程与底泥的理化性质密切相关.三价铁是底泥中常见的竞争性电子受体，在太湖底泥微环境中添加羟基氧化铁（FeOOH），探究其对PCBs厌氧脱氯的影响.结果表明:①两种微环境（未添加FeOOH的对照组和添加了FeOOH的试验组）中的脱氯启动均存在滞后期，对照组的脱氯滞后期为21~42 d，而添加了40 mmol/kg（以泥浆计）FeOOH的试验组中，脱氯于42~63 d启动.脱氯启动后，对照组和FeOOH试验组的脱氯速率分别为0.035和0.014 mg/（kg·d）.第210天时，对照组内54.09%的PCBs母体被降解，而FeOOH试验组中仅去除了20.81%.因此，FeOOH对PCBs的还原脱氯具有显著的抑制作用，不仅延长了脱氯滞后期，还降低了脱氯程度和脱氯速率.②FeOOH显著抑制了间位（meta-）和对位（para-）氯的脱除（P < 0.05）.第210天时，对照组和FeOOH试验组中间位（meta-）氯原子的降解率分别为27.2%和8.9%，对位（para-）氯原子的降解率分别为17.9%和4.9%.但无论在三价铁〔Fe（Ⅲ）〕还原条件下还是无FeOOH添加的对照条件下，脱氯偏好均显示为间位（meta-）>对位（para-）>邻位（ortho-）.邻位脱氯路径仅存在于对照组中，说明FeOOH还原完全抑制了邻位脱氯进程.③脱氯过程中，对照组和FeOOH试验组的生物多样性（Shannon-Wiener指数和Simpson指数）从0天到210天逐渐降低，且Fe（Ⅲ）还原条件下的生物多样性低于对照组.随着脱氯反应的进行，厚壁菌门（Firmicutes）在两个体系中占比最高，而变形菌门（Proteobacteria）的优势地位下降，绿弯菌门（Chloroflexi）的占比有一定程度的提高.对照组和FeOOH试验组中脱氯菌Dehalococcoides均出现富集，Dehalococcoides可能对太湖底泥微环境中PCBs的厌氧脱氯具有重要作用.研究显示，FeOOH对太湖底泥中PCBs的厌氧脱氯具有抑制作用，并使微环境中的微生物群落发生了一定变化. 

Effects of Ferric Oxyhydroxide on Anaerobic Microbial Dechlorination of Polychlorinated Biphenyls in Taihu Lake Sediments

Anaerobic microbial dechlorination of polychlorinated biphenyls (PCBs) is greatly affected by sediment geochemical properties. Ferric iron is known as a common competitive electron accepter in sediments. In this study, ferric oxyhydroxide (FeOOH) was added to the Taihu Lake sediment microcosms to investigate its effects on anaerobic microbial dechlorination of PCBs. The results indicated that: (1) Dechlorination lag time existed in two microcosms (the control group without FeOOH and the experimental group with FeOOH). PCB dechlorination lag time of the control group without FeOOH addition was 21-42 days, while PCB dechlorination lag time was approximately 42-63 days in the experimental group with 40 mmol/kg FeOOH slurry. The dechlorination of the control group and FeOOH-group was 0.035 and 0.014 mg/(kg·d), respectively. On day 210, 54.09% of the spiked parent PCBs in the control group was dechlorinated, while only 20.81% in the FeOOH-group was removed. Therefore, FeOOH exhibited significant inhibitory effects on PCB dechlorination, which not only prolonged the dechlorination lag time, but also reduced the degree and rate of dechlorination. (2) FeOOH greatly inhibited the removal of meta- and para-chlorines (P < 0.05). On day 210, the removal of meta-chlorines in the control group and experimental group with FeOOH was 27.2% and 8.9%, respectively. Meanwhile, 17.9% and 4.9% para-chlorines were removed in the control group and experimental group with FeOOH, respectively. However, the dechlorination preference in the two groups was meta->para->ortho-. Ortho-dechlorination pathway was only observed in the control group, indicating that ortho-dechlorination process was completely inhibited by FeOOH reduction. (3) The biodiversity of both control group and the experimental group with FeOOH decreased gradually from day 0 to day 210, and the biodiversity under the Fe(Ⅲ) reduction condition was much lower than that of the control group. Along with PCB dechlorination, Firmicutes outcompeted Proteobacteria and became the most abundant phylum in the two groups. In addition, the relative abundance of Chloroflexi increased to a certain extent. Dehalococcoides, known as dechlorinators- greatly enriched over time in both control group and FeOOH experimental group and were very likely to play an important role in PCB dechlorination in Taihu Lake sediment microcosms. This study reveals that FeOOH can inhibit the anaerobic microbial dechlorination of PCBs in Taihu Lake sediment microcosms and change the sediment microbial community.