The Global Cycles of the Naturally-Occurring Monohalomethanes
The Global Cycles of the Naturally-Occurring Monohalomethanes
复制标题
天然存在的一卤甲烷的全球循环
DOI：
10.1007/b10456
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发表时间：
2003
影响因子：
5
通讯作者：
J. Hamilton
中科院分区：
文献类型：
--
作者：
D. B. Harper;J. Hamilton
就大气丰度和环境意义而言，自然界中形成的最重要的卤代化合物无疑是气态的一卤代甲烷氯甲烷（CH3Cl）、溴甲烷（CH3Br）和碘甲烷（CH3I）。尽管在过去的35年里，大量的人造氯氟烃进入大气，但大气中浓度为600 pptv、大气总负荷为5 Tg（500万吨）的CH3Cl仍然是大气中最丰富的卤代烃。它与CH3Br一起造成了平流层中约27%的卤素催化臭氧破坏。直到七、八年前，人们还普遍认为大气中大量的CH3Cl和CH3Br的来源是海洋，而这些化合物的汇绝大多数是非生物的。然而，最近，它已变得明显，大多数大气中的CH3Cl和CH3Br有陆地而不是海洋的起源。此外，生物来源，以前被认为是边缘意义，已承担越来越重要的大气收支。认为非生物反应是大气中CH3Cl和CH3Br的唯一汇的看法已被土壤中的微生物降解可能占大气负担的很大比例的认识所取代。在这一章中，我们审查目前的知识，全球循环和大气预算的CH3Cl，CH3Br和CH3I，特别强调生物源和汇。
In terms of atmospheric abundance and environmental significance the most important halogenated compounds formed in nature are undoubtedly the gaseous monohalomethanes chloromethane (CH3Cl), bromomethane (CH3Br) and iodomethane (CH3I). Despite the vast inputs of man-made chlorofluorocarbons into the atmosphere over the last 35 years, CH3Cl, present at an atmospheric concentration of 600 pptv with a total atmospheric burden of 5 Tg (5 million tonnes), is still the most abundant halocarbon in the atmosphere. Together with CH3Br it is responsible for around 27% of halogen-catalysed ozone destruction in the stratosphere. Until seven or eight years ago it was generally accepted that the source of the vast bulk of atmospheric CH3Cl and CH3Br was the oceans and that the sinks for these compounds were overwhelmingly abiotic. Recently, however, it has become apparent that most atmospheric CH3Cl and CH3Br has a terrestrial rather than a marine origin. Moreover, biological sources, formerly regarded as of peripheral significance, have assumed increasing importance in the atmospheric budgets. The belief that abiotic reactions are the only sinks for atmospheric CH3Cl and CH3Br has been displaced by a recognition that microbial degradation in soil may account for a large proportion of the atmospheric burden. In this chapter we review current knowledge concerning the global cycling and atmospheric budgets of CH3Cl, CH3Br and CH3I with particular emphasis on the biological sources and sinks.