Isotopic Analysis of Tropospheric Carbon Monoxide

对流层一氧化碳的同位素分析

• 批准号: 9417525
• 负责人: John Mak
• 金额: $ 22.52万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-01 至 1998-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9417525&HistoricalAwards=false
• 关键词: Isotopic; Analysis; Tropospheric; Carbon; Monoxide

9417525 Mak Hydroxyl radial (OH) is the primary oxidant of the earth's atmosphere and so its concentration determines, to a large degree, the lifetimes of a host of trace gases. Carbon monoxide (CO) is a reactive species which controls the OH concentration in many parts of the remote atmosphere. The isotopes of atmospheric carbon monoxide can be used to constrain both the OH concentration as well as the relative source strengths of CO. In the first case, 14CO is measured to constrain OH concentrations. Since the 14CO cosmogenic production rate is known, its loss rate, and therefore the average OH concentration, can be deduced if the atmospheric inventory is determined. In the second case, the stable isotopes (13CO and C18O) are measured to help assess the relative source strengths, since certain sources of CO have characteristic isotopic signatures. The main sources of CO are methane oxidation by OH, non- methane hydrocarbon oxidation by OH, biomass burning, and fossil fuel combustion. However, the relative importance of these sources is poorly known. Determining the atmospheric abundance and seasonality of the isotopes of CO will provide important information concerning the relative magnitude of those sources. During the 1970's and 1980's CO has been increasing at a rate of about 1% per year, but for the last three to five years, this trend has reversed direction, and CO has been decreasing globally at a rate of 6-7% per year. The causes of these interannual variations are not known. Analysis of the isotopic composition of CO can help constrain the relative source rates. The PI proposes to build a clean air sampling system and cryogenic vacuum extraction line which will allow for the collection, separation, and analysis of air samples for the isotopes of carbon monoxide (14CO, 13CO, and C18O), and to then begin measurement of these isotopes from air samples collected at the Mauna Loa Observatory (in collaboration with the NOAA CMDL facility) and from samples collected in-flight between California and New Zealand.

9417525麦羟基(OH)是地球大气的主要氧化剂，因此其浓度在很大程度上决定了大量痕量气体的寿命。一氧化碳(CO)是一种活性物种，它控制着遥远大气中许多地方的OH浓度。大气中一氧化碳的同位素既可以用来限制氢氧化物的浓度，也可以用来限制一氧化碳的相对来源强度。在第一种情况下，测量~(14)CO以限制OH浓度。由于已知~(14)CO宇宙产生率，因此，如果确定大气库存，就可以推算出它的损失率，从而推算出平均氢氧浓度。在第二种情况下，测量稳定同位素(13CO和C18O)以帮助评估相对来源强度，因为某些来源的CO具有特征的同位素特征。CO的主要来源是甲烷的OH氧化、非甲烷烃的OH氧化、生物质燃烧和化石燃料燃烧。然而，这些来源的相对重要性却鲜为人知。确定大气中CO同位素的丰度和季节性将提供有关这些来源的相对大小的重要信息。在20世纪70年代的S和80年代的S期间，CO一直以每年约1%的速度增长，但在过去的三到五年里，这一趋势发生了逆转，全球CO一直以每年6%-7%的速度下降。这些年际变化的原因尚不清楚。分析CO的同位素组成有助于限制相对来源速率。PI提议建立一个清洁的空气采样系统和低温真空提取线，以便能够收集、分离和分析一氧化碳(14CO、13CO和C18O)的空气样本，然后开始从莫纳罗亚天文台收集的空气样本(与美国国家海洋和大气局CMDL设施合作)和从加州和新西兰之间的飞行中收集的样本测量这些同位素。