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 Mak 羟基自由基 (OH) 是地球大气中的主要氧化剂，因此其浓度在很大程度上决定了许多痕量气体的寿命。 一氧化碳 (CO) 是一种活性物质，它控制着遥远大气中许多地方的 OH 浓度。 大气一氧化碳的同位素可用于限制 OH 浓度以及 CO 的相对来源强度。在第一种情况下，测量 14CO 来限制 OH 浓度。 由于 14CO 宇宙生成速率已知，如果确定了大气库存，则可以推断出其损失率以及平均 OH 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 CO 来源具有特征同位素特征。 CO的主要来源是甲烷被OH氧化、非甲烷烃被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。 确定二氧化碳同位素的大气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 1970 年代和 1980 年代，二氧化碳以每年约 1% 的速度增加，但在过去的三到五年里，这一趋势发生了逆转，全球二氧化碳以每年 6-7% 的速度减少。 这些年际变化的原因尚不清楚。 CO 同位素组成分析有助于限制相对源速率。 项目负责人建议建造一个清洁空气采样系统和低温真空提取线，以便收集、分离和分析空气样本中的一氧化碳同位素（14CO、13CO 和 C18O），然后开始测量这些同位素来自莫纳罗亚天文台（与 NOAA CMDL 设施合作）收集的空气样本以及加利福尼亚和新西兰之间飞行中收集的样本。