PNAS:协调甲烷排放的估计

摘要 : 美国环境防御基金会在美国德克萨斯州Barnett页岩油气产区进行的一项研究发现，反复的大气测量以及对排放源的改善的清查能够协调此前对来自天然气基础设施的甲烷排放的自上而下和自下而上的估计的不一致。

美国环境防御基金会在美国德克萨斯州Barnett页岩油气产区进行的一项研究发现，反复的大气测量以及对排放源的改善的清查能够协调此前对来自天然气基础设施的甲烷排放的自上而下和自下而上的估计的不一致。根据大气测量确定的自上而下的甲烷估计，通常会超过在源头处测量排放的自下而上的估计。为让自上而下和自下而上的排放估计协调一致，Steven P. Hamburg及其同事整合了2013年的一场量化Barnett页岩排放的运动得到的数据集合，结果发现自上而下和自下而上的该地区天然气甲烷排放估计在10%的范围内一致。这组作者发现，高排放设施看上去在空间和时间上可变，在任何给定时间，大约2%的设施产生了大约一半的甲烷排放。这组作者把这种一致性部分归结于重复的自上而下的质量平衡估计飞行，它测量乙烷从而区别生物产生的甲烷排放和天然气基础设施的排放。此外，这种自下而上的估计包含了一个比此前的估计更准确的设施清查，并且使用了统计估计得到大型排放源的影响。这组作者说，这些结果提示，甲烷排放可能构成了该地区至多1.5% 的天然气产量，而真实的排放可能比美国环保署数据预计的大至多90%。

原文链接：

Reconciling divergent estimates of oil and gas methane emissions

原文摘要：

Published estimates of methane emissions from atmospheric data (top-down approaches) exceed those from source-based inventories (bottom-up approaches), leading to conflicting claims about the climate implications of fuel switching from coal or petroleum to natural gas. Based on data from a coordinated campaign in the Barnett Shale oil and gas-producing region of Texas, we find that top-down and bottom-up estimates of both total and fossil methane emissions agree within statistical confidence intervals (relative differences are 10% for fossil methane and 0.1% for total methane). We reduced uncertainty in top-down estimates by using repeated mass balance measurements, as well as ethane as a fingerprint for source attribution. Similarly, our bottom-up estimate incorporates a more complete count of facilities than past inventories, which omitted a significant number of major sources, and more effectively accounts for the influence of large emission sources using a statistical estimator that integrates observations from multiple ground-based measurement datasets. Two percent of oil and gas facilities in the Barnett accounts for half of methane emissions at any given time, and high-emitting facilities appear to be spatiotemporally variABLe. Measured oil and gas methane emissions are 90% larger than estimates based on the US Environmental Protection Agency’s Greenhouse Gas Inventory and correspond to 1.5% of natural gas production. This rate of methane loss increases the 20-y climate impacts of natural gas consumed in the region by roughly 50%.

doi: 10.1073/PNAS.1522126112

作者：Daniel Zavala-Araiza

;