Methane Isotope Instrument Validation and Source Identification at Four Corners, New Mexico, United States

详细信息    查看全文

• 作者：Caleb Arata ; Thom Rahn ; Manvendra K. Dubey
• 刊名：Journal of Physical Chemistry A
• 出版年：2016
• 出版时间：March 10, 2016
• 年：2016
• 卷：120
• 期：9
• 页码：1488-1494
• 全文大小：515K
• ISSN：1520-5215

文摘

Measurements of δ¹³CH₄ and CH₄ concentration were made at a field site in Four Corners, New Mexico (FC), where we observed large sustained CH₄ enhancements (2–8 ppm peaks for hours) during nocturnal inversions. Potential sources of this large CH₄ signal at FC include (1) fugitive emissions from coal mining and gas processing that are thermogenic and isotopically ¹³C enriched relative to background atmosphere and (2) emissions from agriculture, ruminants, landfills, and coalbed biogenic methane that are¹³C depleted relative to background atmosphere. We analyze our measurements of methane concentration and δ¹³C during spring and summer of 2012 to identify fugitive methane sources. We find CH₄ plumes that are both enriched and depleted in ¹³C relative to CH₄ in background air. Keeling plots show a continuum of δ¹³C source compositions between −40‰ and −60‰ that are consistent with thermogenic and biogenic sources. The Picarro Mobile Methane Investigator (PMMI), a mobile δ¹³CH₄ instrument platform, was deployed in the spring of 2013 and used to verify the isotopic enrichment of coal bed methane in the region. We combine our results with meteorological data to spatially separate these sources in the Four Corners regions. Using CO and CO₂ data, along with meteorological data, we propose that the high methane concentration events ([CH₄] > 3.5 ppm) are from both thermogenic and biogenic methane released from coal beds.