Detection of Fossil and Biogenic Methane at Regional Scales Using Atmospheric Radiocarbon
Detection of Fossil and Biogenic Methane at Regional Scales Using Atmospheric Radiocarbon
复制标题
DOI：
10.1029/2018ef001064
复制
发表时间：
2019-03-01
期刊：
影响因子：
8.2
通讯作者：
Zazzeri, G.
中科院分区：
文献类型：
--
作者：
Graven, H.;Hocking, T.;Zazzeri, G.
区域甲烷排放量及其归因于各种来源目前存在很大的不确定性。测量甲烷（CH 4）中的放射性碳（C-14）可以提供一种方法，用于识别来自化石源和生物源的区域CH 4排放，因为添加不含C-14的化石碳比生物源碳更能降低大气CH 4中的C-14/C比率（Delta（CH 4）-C-14）。我们描述了一种方法，估计化石和生物甲烷在区域尺度上使用大气三角洲（CH 4）-C-14观测。作为一个案例研究，以证明预期的德尔塔（CH 4）-C-14和德尔塔（CH 4）-C-14-CH 4的关系，我们模拟和比较德尔塔（CH 4）-C-14在加州的网站网络使用两个网格CH 4排放量估计（全球大气研究排放数据库，埃德加和网格环境保护局，GEPA）和2014年的CarbonTracker-Lagrange模型，以及2030年的“一切照旧”和减缓设想方案。CH 4（F）的化石部分与模拟的Delta（CH 4）-C14-CH 4斜率密切相关，2014年埃德加与GEPA的F中值差异为2-21%，2030年照常和减缓情景的差异为7-10%。对于>200 ppb的添加的CH 4，F的差异为10%，产生Delta（CH 4）-C-14的差异>10，这可能从常规观测中检测到。核电厂（CH 4）-C-14排放量通常对Delta（CH 4）-C-14（0-7）的模拟中值影响较小，但在某些大气条件下，它们可能更强（>30），这表明在加州应用Delta（CH 4）-C-14时必须考虑它们。这项研究表明，大气Delta（CH 4）-C-14测量可以对区域CH 4排放量提供强有力的限制，补充其他监测技术。
Regional emissions of methane and their attribution to a variety of sources presently have large uncertainties. Measurements of radiocarbon (C-14) in methane (CH4) may provide a method for identifying regional CH4 emissions from fossil versus biogenic sources because adding C-14-free fossil carbon reduces the C-14/C ratio (Delta(CH4)-C-14) in atmospheric CH4 much more than biogenic carbon does. We describe an approach for estimating fossil and biogenic CH4 at regional scales using atmospheric Delta(CH4)-C-14 observations. As a case study to demonstrate expected Delta(CH4)-C-14 and Delta(CH4)-C-14-CH4 relationships, we simulate and compare Delta(CH4)-C-14 at a network of sites in California using two gridded CH4 emissions estimates (Emissions Database for Global Atmospheric Research, EDGAR, and Gridded Environmental Protection Agency, GEPA) and the CarbonTracker-Lagrange model for 2014, and for 2030 under business-as-usual and mitigation scenarios. The fossil fraction of CH4 (F) is closely linked with the simulated Delta(CH4)-C-14-CH4 slope and differences of 2-21% in median F are found for EDGAR versus GEPA in 2014, and 7-10% for business-as-usual and mitigation scenarios in 2030. Differences of 10% in F for >200 ppb of added CH4 produce differences of >10 in Delta(CH4)-C-14, which are likely detectable from regular observations. Nuclear power plant (CH4)-C-14 emissions generally have small simulated median influences on Delta(CH4)-C-14 (0-7), but under certain atmospheric conditions they can be much stronger (>30) suggesting they must be considered in applications of Delta(CH4)-C-14 in California. This study suggests that atmospheric Delta(CH4)-C-14 measurements could provide powerful constraints on regional CH4 emissions, complementary to other monitoring techniques.