Abiotic Methyl Bromide Formation from Vegetation, and Its Strong Dependence on Temperature

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• 作者：Asher Wishkerman ; Sarah Gebhardt ; Colin W. McRoberts ; John T. G. Hamilton ; Jonathan Williams ; Frank Keppler
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：September 15, 2008
• 年：2008
• 卷：42
• 期：18
• 页码：6837-6842
• 全文大小：157K
• 年卷期：v.42,no.18(September 15, 2008)
• ISSN：1520-5851

文摘

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 °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 °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.