Wishkerman Asher, Gebhardt Sarah, McRoberts Colin W, Hamilton John T G, Williams Jonathan, Keppler Frank
Max Planck Institute for Chemistry, J. J. Becherweg 27, 55128 Mainz, Germany.
Environ Sci Technol. 2008 Sep 15;42(18):6837-42. doi: 10.1021/es800411j.
Methyl bromide (CH3Br) is the most abundant brominated organic compound in the atmosphere. It is known to originate from natural and anthropogenic sources, although many uncertainties remain regarding strengths of both sources and sinks and the processes leading to its formation. In this study a potential new CH3Br source from vegetation has been examined, analogous to the recently discovered abiotic formation of methyl chloride from plant pectin. Several plant samples with known bromine content, including ash (Fraxinus excelsior), saltwort (Batis maritima), tomato reference material (NIST-1573a), hay reference material (IAEA V-10), and also bromine enriched pectin, were incubated in the temperature range of 25-50 degrees C and analyzed for CH3Br emission using gas chromatography/mass spectrometry. All plant samples inspected showed an exponential increase in CH3Br emission as a function of temperature increase, i.e., emissions were observed to approximately double with every 5 degrees C rise in temperature. Next to temperature, it was found that emissions of CH3Br were also dependent on the bromine content of the plants. The highest CH3Br release rates were found for the saltwort which contained the highest bromine concentration. Arrhenius plots confirmed that the observed emissions were from an abiotic origin. The contribution of abiotic CH3Br formation from vegetation to the global budget will vary geographically as a result of regional differences in both temperature and bromide content of terrestrial plants.
甲基溴（CH₃Br）是大气中含量最丰富的溴化有机化合物。虽然其源和汇的强度以及导致其形成的过程仍存在许多不确定性，但已知它来源于自然和人为来源。在本研究中，研究了一种来自植被的潜在新甲基溴源，类似于最近发现的由植物果胶非生物形成甲基氯的情况。将几种已知溴含量的植物样品，包括白蜡树（欧洲白蜡树）灰分、碱蓬（滨海碱蓬）、番茄标准物质（NIST - 1573a）、干草标准物质（IAEA V - 10）以及富含溴的果胶，在25 - 50摄氏度的温度范围内进行培养，并使用气相色谱/质谱法分析甲基溴的排放情况。所有检测的植物样品均显示，随着温度升高，甲基溴排放呈指数增加，即温度每升高5摄氏度，排放量大约翻倍。除了温度，还发现甲基溴的排放也取决于植物的溴含量。碱蓬的溴浓度最高，其甲基溴释放速率也最高。阿累尼乌斯曲线证实观察到的排放源自非生物过程。由于陆地植物温度和溴化物含量的区域差异，植被非生物形成甲基溴对全球收支的贡献将因地理位置而异。
