Centre for Earth Evolution and Dynamics (CEED), University of Oslo, Oslo, Norway.
Istituto Nazionale di Geofisica e Vulcanologia, via di Vigna Murata 605, 00143, Rome, Italy.
Sci Rep. 2021 Feb 18;11(1):4138. doi: 10.1038/s41598-021-83369-9.
Quantifying natural geological sources of methane (CH) allows to improve the assessment of anthropogenic emissions to the atmosphere from fossil fuel industries. The global CH flux of geological gas is, however, an object of debate. Recent fossil (C-free) CH measurements in preindustrial-era ice cores suggest very low global geological emissions (~ 1.6 Tg year), implying a larger fossil fuel industry source. This is however in contrast with previously published bottom-up and top-down geo-emission estimates (~ 45 Tg year) and even regional-scale emissions of ~ 1-2 Tg year. Here we report on significant geological CH emissions from the Lusi hydrothermal system (Indonesia), measured by ground-based and satellite (TROPOMI) techniques. Both techniques indicate a total CH output of ~ 0.1 Tg year, equivalent to the minimum value of global geo-emission derived by ice core CH estimates. Our results are consistent with the order of magnitude of the emission factors of large seeps used in global bottom-up estimates, and endorse a substantial contribution from natural Earth's CH degassing. The preindustrial ice core assessments of geological CH release may be underestimated and require further study. Satellite measurements can help to test geological CH emission factors and explain the gap between the contrasting estimates.
量化自然地质成因的甲烷（CH）排放有助于提高对化石燃料工业向大气排放人为 CH 的评估。然而，全球地质成因 CH 通量是一个存在争议的问题。最近在工业化前冰芯中对化石（无碳）CH 的测量表明，全球地质排放量非常低（1.6Tg 年），这意味着化石燃料工业的排放量更大。然而，这与之前公布的自下而上和自上而下的地质排放估算值（45Tg 年），甚至是区域性排放值（~1-2Tg 年）相矛盾。在这里，我们报告了印度尼西亚 Lusi 热液系统中显著的地质 CH 排放，这些排放是通过地面和卫星（TROPOMI）技术测量的。这两种技术都表明，总 CH 排放量约为 0.1Tg 年，与冰芯 CH 估算得出的全球地质排放最低值相当。我们的结果与全球自下而上估算中使用的大型渗漏排放因子的数量级一致，这支持了地球 CH 释放的大量自然贡献。工业化前冰芯对地质 CH 释放的评估可能被低估了，需要进一步研究。卫星测量可以帮助测试地质 CH 排放因子，并解释相互矛盾的估算值之间的差距。
