School of Civil and Environmental Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0512, United States.
Environ Sci Technol. 2014 Nov 18;48(22):13350-7. doi: 10.1021/es503071m. Epub 2014 Nov 5.
Volatile chlorinated compounds are major pollutants in groundwater, and they pose a risk of vapor intrusion into buildings. Vapor intrusion can be prevented by natural attenuation in the vadose zone if biodegradation mechanisms can be established. In this study, we tested the hypothesis that bacteria can use cis-dichloroethene (cis-DCE) or vinyl chloride (VC) as an electron donor in the vadose zone. Anoxic water containing cis-DCE or VC was pumped continuously beneath laboratory columns that represented the vadose zone. Columns were inoculated with Polaromonas sp. strain JS666, which grows aerobically on cis-DCE, or with Mycobacterium sp. JS60 and Nocardiodes sp. JS614 that grow on VC. Complete biodegradation with fluxes of 84 ± 15 μmol of cis-DCE · m(-2) · hr(-1) and 218 ± 25 μmole VC·m(-2) · h(-1) within the 23 cm column indicated that microbial activities can prevent the migration of cis-DCE and VC vapors. Oxygen and volatile compound profiles along with enumeration of bacterial populations indicated that most of the biodegradation took place in the first 10 cm above the saturated zone within the capillary fringe. The results revealed that cis-DCE and VC can be biodegraded readily at the oxic/anoxic interfaces in the vadose zone if appropriate microbes are present.
挥发性氯化化合物是地下水的主要污染物，它们构成了蒸气侵入建筑物的风险。如果可以建立生物降解机制，那么在包气带中通过自然衰减就可以防止蒸气侵入。在这项研究中，我们检验了这样一个假设，即在包气带中，细菌可以将顺式-1,2-二氯乙烯（cis-DCE）或氯乙烯（VC）用作电子供体。含有 cis-DCE 或 VC 的缺氧水被连续泵入代表包气带的实验室柱中。用能够好氧降解 cis-DCE 的 Polaromonas sp. strain JS666 或能够降解 VC 的 Mycobacterium sp. JS60 和 Nocardiodes sp. JS614 对柱进行接种。在 23 厘米长的柱中，通量分别为 84 ± 15 μmol cis-DCE·m(-2)·hr(-1)和 218 ± 25 μmole VC·m(-2)·h(-1)，实现了完全生物降解，这表明微生物活性可以阻止 cis-DCE 和 VC 蒸气的迁移。氧气和挥发性化合物的分布以及细菌种群的计数表明，大部分生物降解发生在饱和带上方毛细带的前 10 厘米内。结果表明，如果存在适当的微生物，cis-DCE 和 VC 可以在包气带的好氧/缺氧界面上很容易地被生物降解。
