科研之友
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摘要
Brominated organic halogens such as bromoform (CHBr3) and dibromomethane (CH2Br2) play important roles as carriers of bromine from the ocean to the atmosphere. The bromine carried by these brominated methanes is released into the atmosphere, where it catalyzes ozone depletion. Previously, however, no microbial organisms capable of CHBr3 decomposition have been found in marine environments. In this study, we investigated bacteria to assess their capacity to decompose CHBr3 in temperate oceans. Bacteria were incubated with (CHBr3)-C-13 at 25 degrees C and the concentrations of trace gases in the gas phase above the cultured samples were determined using dynamic headspace gas chromatography-mass spectrometry. Bacterial growth was monitored by measuring the optical density at 600 nm. (CHBr3)-C-13 was decomposed for several days by cultures of three different bacteria, Phaeobacter gallaeciensis, Roseobacter denitrifi cans, and Rhodobacter vinaykumarii, suggesting temperate marine bacteria can decompose CHBr3. The maximum (CHBr3)-C-13 decomposition rate was observed in the culture of P. gallaeciensis. The half-lives for (CHBr3)-C-13 decomposition by P. gallaeciensis, R. denitrificans, and R. vinaykumarii were 0.4 (03-0.5), 2.7 (2.5-2.9), and 2.0 (1.9-2.0) days, respectively. (CH2Br2)-C-13 and (13)CHgr(2)CI production were observed in the cultures, suggesting that 13CHBr3 was transformed into these compounds, and the production ratio of (CH2Br2)-C-13 was approximately 30% of the amount of (CHBr3)-C-13 spiked into the bacterial cultures. In contrast to CHBr3, CH2Br2 was not decomposed by the P. gallaeciensis, R. denitrifi cans, and R. vinaykumarii cultures. These results suggest that aquatic bacteria could act as a new sink for CHBr3 through decomposition in marine environments.
- 出版日期2015-11-20
