Isotope Fractionation Effect During Soil Uptake of Methane, Carbon Monoxide, and Hydrogen

土壤对甲烷、一氧化碳和氢的吸收过程中的同位素分馏效应。本研究已提交给环境地球化学和生物地球化学（EGB）征求，NSF 06-152。它由海洋科学部和大气科学部联合资助。本研究的目的是测量土壤在吸收一氧化碳（CO）、甲烷（CH4）和氢气（H2）过程中的同位素分馏。对这些分馏效应进行量化是很重要的，这样对这些温室气体的持续大气测量就可以充分利用同位素数据来确定具体的源和汇。这将使我们对这些具有重要放射性的微量气体的全球循环的理解取得重大进展。PI的建议，经验测量同位素分馏效应使用土壤围护和测量空气样本收集作为一个时间序列在顶空。利用土壤特征（如温度、湿度、孔隙度、成分等），将特定地点的数据外推到区域和全球尺度。总的来说，拟议的测量，与正在进行的CH4、CO同位素组成的时间序列测量和预期的H2测量相结合，将提供所需的框架，以确定土壤吸收对温带北纬地区这些气体浓度和同位素组成的季节性变化的影响，以及对其同位素组成的半球间不对称性的影响。

Isotope fractionation effect during soil uptake of methane, carbon monoxide and hydrogen This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry (EGB) solicitation, NSF 06-152. It is being jointly funded by the Divisions of Ocean Sciences and Atmospheric Science. The objective of this proposal is to measure isotope fractionation during soil uptake of carbon monoxide (CO), methane (CH4) and hydrogen (H2). These fractionation effects are important to quantify so that continued atmospheric measurements of these greenhouse gases can take full advantage of isotopic data to fingerprint specific sources and sinks. This will allow for a significant advancement in our understanding of the global cycles of these radiatively important trace gases. The PI's propose to empirically measure the isotopic fractionation effect using soil enclosures and measuring air samples collected as a time-series in the headspace. The site specific data will be extrapolated to regional and global scales using soil characteristics (e.g. temperature, moisture, porosity, composition, etc.). Overall, the proposed measurements, when coupled with on-going time series measurements of the isotopic composition of CH4, CO and anticipated measurements of H2, will provide the framework needed to determine the influence of soil uptake on the seasonal changes in the concentration and isotopic composition of these gases in temperate northern latitudes and on the interhemispheric asymmetry of their isotopic composition.