Department of Chemistry, University of California-Irvine, Irvine, California 92697, USA.
Nature. 2012 Aug 23;488(7412):490-4. doi: 10.1038/nature11342.
After methane, ethane is the most abundant hydrocarbon in the remote atmosphere. It is a precursor to tropospheric ozone and it influences the atmosphere's oxidative capacity through its reaction with the hydroxyl radical, ethane's primary atmospheric sink. Here we present the longest continuous record of global atmospheric ethane levels. We show that global ethane emission rates decreased from 14.3 to 11.3 teragrams per year, or by 21 per cent, from 1984 to 2010. We attribute this to decreasing fugitive emissions from ethane's fossil fuel source--most probably decreased venting and flaring of natural gas in oil fields--rather than a decline in its other major sources, biofuel use and biomass burning. Ethane's major emission sources are shared with methane, and recent studies have disagreed on whether reduced fossil fuel or microbial emissions have caused methane's atmospheric growth rate to slow. Our findings suggest that reduced fugitive fossil fuel emissions account for at least 10-21 teragrams per year (30-70 per cent) of the decrease in methane's global emissions, significantly contributing to methane's slowing atmospheric growth rate since the mid-1980s.
在甲烷之后，乙烷是远程大气中最丰富的碳氢化合物。它是对流层臭氧的前体，通过与羟基自由基反应影响大气的氧化能力，这是乙烷的主要大气汇。在这里，我们呈现了全球大气乙烷水平的最长连续记录。我们表明，从 1984 年到 2010 年，全球乙烷排放量从 143 到 113 太克/年，即减少了 21%。我们将其归因于乙烷化石燃料源的逸散排放减少——最有可能是油田天然气的泄漏和燃烧减少——而不是其其他主要来源，生物燃料使用和生物质燃烧的减少。乙烷的主要排放源与甲烷相同，最近的研究对减少化石燃料或微生物排放导致甲烷大气增长率放缓的原因存在分歧。我们的研究结果表明，逸散的化石燃料排放量减少至少占甲烷全球排放量减少的 10-21 太克/年（30-70%），这显著导致了自 20 世纪 80 年代中期以来甲烷大气增长率的放缓。
