Carbon and hydrogen stable isotopic ratios of methane emitted from wetlands and wildfires in Alaska: Aircraft observations and bonfire experiments

Taku Umezawa, Shuji Aoki, Yongwon Kim, Shinji Morimoto, Takakiyo Nakazawa

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

To investigate spatial variations of CH4 concentration, δ13CH4, and δD-CH4 over Alaska, aircraft observations were conducted during the summer of 2006. CH4 concentrations elevated above the background level were observed over areas with wetlands and wildfires, important sources of CH4. Several flights showed elevated CH4 values, with corresponding δ 13CH4 and δD-CH4 signatures of -63.4‰ ± 3.0‰ and -424‰ ± 79‰, respectively, which are based on the relationship between δ 13CH4 (or δD-CH4) and CH4 concentration (single mixing relation), an indication of wetland source. It was also noted that both wetlands and wildfires influenced the CH4 concentrations observed over the wildfire area. Assuming certain emission ratios of CH4 to CO (ERCH4/CO) for the wildfire and certain values of δ13CH4 and δD-CH4 for wetland CH4, we derived δ13CH4 and δD-CH4 of CH4 emitted 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/CO value was plausible and that δ13CH4 and δD-CH 4 obtained by the bonfire experiments agreed with the estimates by the aircraft observations. We also found that δ13CH4 and δD-CH4 values became enriched with increasing combustion efficiency. By using the relationship between δD-CH4 for biomass burning and δD of precipitation, global average of δD-CH4 emitted from biomass burning was estimated to be -204‰ ± 11‰.

Original languageEnglish
Article numberD15305
JournalJournal of Geophysical Research Atmospheres
Volume116
Issue number15
DOIs
Publication statusPublished - 2011

ASJC Scopus subject areas

  • Geophysics
  • Forestry
  • Oceanography
  • Aquatic Science
  • Ecology
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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