Carbon and hydrogen stable isotopic ratios of methane emitted from wetlands and wildfires in Alaska: aircraft observations and bonfire experiments
Carbon and hydrogen stable isotopic ratios of methane emitted from wetlands and wildfires in Alaska: aircraft observations and bonfire experiments
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阿拉斯加湿地和野火排放的甲烷的碳和氢稳定同位素比率：飞机观测和篝火实验
DOI：
10.1029/2010jd015545
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发表时间：
2011
期刊：
影响因子：
--
通讯作者：
and T. Nakazawa
中科院分区：
文献类型：
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作者：
T. Umezawa;S. Aoki;Y. Kim;S. Morimoto;and T. Nakazawa
为了研究阿拉斯加上空CH4、δ13CH4和δD-CH4浓度的空间变化，在2006年夏季进行了飞机观测。在有湿地和野火的地区观察到甲烷浓度高于本底水平，而湿地和野火是甲烷的重要来源。有几个航班的CH4值升高，相应的δ13CH4和δD-CH4特征分别为−63.4‰±3.0‰和−424‰±79‰，这是基于δ13CH4(或δD-CH4)与CH4浓度的关系(单一混合关系)，这是湿地来源的指示。还指出，湿地和野火都影响了在野火地区观测到的甲烷浓度。假设野火的CH4与CO的排放比(ERCH4/CO)和湿地CH4的δ13CH4和δD-CH4有一定的值，我们得到野火排放的CH4的δ13CH4和δD-CH4分别为−27.5‰±2.0‰和−285‰±111‰，这与以前在低纬度地区的研究结果比较吻合，但略有下降。为了验证这些估计，在阿拉斯加内陆地区进行了篝火实验，使用与飞机观察到的野火中燃烧的生物质相同的材料。结果表明，以前报道的ERCH_4/CO值是可信的，篝火实验得到的δ_(13)CH_4和δ_D-CH_4与飞机观测的估计值是一致的。δ~(13)CH_4和δ_D-CH_4值随燃烧效率的提高而变富。利用生物质燃烧的δD-CH4与降水的δD之间的关系，估算出全球生物质燃烧排放的δD-CH4平均值为−204‰±11‰。
To investigate spatial variations of CH4concentration,δ13CH4, andδD‐CH4over Alaska, aircraft observations were conducted during the summer of 2006. CH4concentrations elevated above the background level were observed over areas with wetlands and wildfires, important sources of CH4. Several flights showed elevated CH4values, with correspondingδ13CH4andδD‐CH4signatures of −63.4‰ ± 3.0‰ and −424‰ ± 79‰, respectively, which are based on the relationship betweenδ13CH4(orδD‐CH4) and CH4concentration (single mixing relation), an indication of wetland source. It was also noted that both wetlands and wildfires influenced the CH4concentrations observed over the wildfire area. Assuming certain emission ratios of CH4to CO (ERCH4/CO) for the wildfire and certain values ofδ13CH4andδD‐CH4for wetland CH4, we derivedδ13CH4andδD‐CH4of CH4emitted from the wildfire to be −27.5‰ ± 2.0‰ and −285‰ ± 111‰, respectively, which agreed relatively well with, but was slightly lower than, those obtained by previous studies at lower latitudes. To verify these estimates, bonfire experiments were conducted in the interior of Alaska using the same biomass material burned in the wildfire observed by the aircraft. The result showed that the previously reported ERCH4/COvalue was plausible and thatδ13CH4andδD‐CH4obtained by the bonfire experiments agreed with the estimates by the aircraft observations. We also found thatδ13CH4andδD‐CH4values became enriched with increasing combustion efficiency. By using the relationship betweenδD‐CH4for biomass burning andδD of precipitation, global average ofδD‐CH4emitted from biomass burning was estimated to be −204‰ ± 11‰.