Aulenta Federico, Potalivo Monica, Majone Mauro, Papini Marco Petrangeli, Tandoi Valter
Department of Chemistry, University of Rome La Sapienza, P.le Aldo Moro 5, 00185, Rome, Italy.
Biodegradation. 2006 Jun;17(3):193-206. doi: 10.1007/s10532-005-4218-7.
This study investigated the biotransformation pathways of 1,1,2,2-tetrachloroethane (1,1,2,2-TeCA) in the presence of chloroethenes (i.e. tetrachloroethene, PCE; trichloroethene, TCE) in anaerobic microcosms constructed with subsurface soil and groundwater from a contaminated site. When amended with yeast extract, lactate, butyrate, or H2 and acetate, 1,1,2,2-TeCA was initially dechlorinated via both hydrogenolysis to 1,1,2-trichloroethane (1,1,2-TCA) (major pathway) and dichloroelimination to dichloroethenes (DCEs) (minor pathway), with both reactions occurring under sulfidogenic conditions. In the presence of only H2, the hydrogenolysis of 1,1,2,2-TeCA to 1,1,2-TCA apparently required the presence of acetate to occur. Once formed, 1,1,2-TCA was degraded predominantly via dichloroelimination to vinyl chloride (VC). Ultimately, chloroethanes were converted to chloroethenes (mainly VC and DCEs) which persisted in the microcosms for very long periods along with PCE and TCE originally present in the groundwater. Hydrogenolysis of chloroethenes occurred only after highly reducing methanogenic conditions were established. However, substantial conversion to ethene (ETH) was observed only in microcosms amended with yeast extract (200 mg/l), suggesting that groundwater lacked some nutritional factors which were likely provided to dechlorinating microorganisms by this complex organic substrate. Bioaugmentation with an H2-utilizing PCE-dechlorinating Dehalococcoides spp. -containing culture resulted in the conversion of 1,1,2,2-TeCA, PCE and TCE to ETH and VC. No chloroethanes accumulated during degradation suggesting that 1,1,2,2-TeCA was degraded through initial dichloroelimination into DCEs and then typical hydrogenolysis into ETH and VC.
本研究在取自某污染场地的地下土壤和地下水中构建厌氧微观生态系统，调查了在氯乙烯（即四氯乙烯，PCE；三氯乙烯，TCE）存在的情况下，1,1,2,2 - 四氯乙烷（1,1,2,2 - TeCA）的生物转化途径。当用酵母提取物、乳酸盐、丁酸盐或氢气和乙酸盐进行修正时，1,1,2,2 - TeCA最初通过氢解作用生成1,1,2 - 三氯乙烷（1,1,2 - TCA）（主要途径）和二氯消除反应生成二氯乙烯（DCEs）（次要途径）进行脱氯，这两种反应均在产硫化物条件下发生。仅在有氢气存在的情况下，1,1,2,2 - TeCA氢解生成1,1,2 - TCA显然需要乙酸盐的存在才能发生。一旦形成，1,1,2 - TCA主要通过二氯消除反应降解为氯乙烯（VC）。最终，氯乙烷转化为氯烯烃（主要是VC和DCEs），它们与地下水中原本存在的PCE和TCE一起在微观生态系统中长时间存在。氯烯烃的氢解仅在建立高度还原的产甲烷条件后才发生。然而，仅在用酵母提取物（200 mg/l）修正的微观生态系统中观察到大量转化为乙烯（ETH），这表明地下水中缺乏一些营养因子，而这种复杂的有机底物可能为脱氯微生物提供了这些营养因子。用含有利用氢气的PCE - 脱氯的脱卤球菌属（Dehalococcoides spp.）的培养物进行生物强化，导致1,1,2,2 - TeCA、PCE和TCE转化为ETH和VC。降解过程中没有氯乙烷积累，这表明1,1,2,2 - TeCA首先通过二氯消除反应降解为DCEs，然后通过典型的氢解反应降解为ETH和VC。
