The challenge of reconciling bottom-up agricultural methane emissions inventories with top-down measurements
The challenge of reconciling bottom-up agricultural methane emissions inventories with top-down measurements
复制标题
DOI：
10.1016/j.agrformet.2017.09.003
复制
发表时间：
2018-01
影响因子：
6.2
通讯作者：
R. Desjardins;D. Worth;E. Pattey;A. VanderZaag;R. Srinivasan;M. Mauder;D. Worthy;C. Sweeney;S. Metzger
中科院分区：
文献类型：
--
作者：
R. Desjardins;D. Worth;E. Pattey;A. VanderZaag;R. Srinivasan;M. Mauder;D. Worthy;C. Sweeney;S. Metzger
据估计，农业产生了超过40%的人为甲烷（CH4）排放，加剧了全球气候变化。自下而上的、以IPCC为基础的方法通常用于估计农业部门的贡献，但由于分离分散的来源的挑战，这些估计很少在农场大门之外得到验证。本文介绍了利用基于飞机的测量平台获得的涡动相关方差（EC）、松弛涡动累积（REA）和小波协方差对CH4通量的测量，并将这些自上而下的估算结果与自下而上的足迹调整后的CH4排放清单估算结果进行了比较。自上而下的ch4通量吻合良好（平均±1标准误差：EC = 17±4 mg CH4m−2d−1;REA = 19±3 mg CH4m−2d−1，小波协方差= 16±3 mg CH4m−2d−1），且无统计学差异，但显著高于自下而上的基于畜牧业的ch4排放清查估计值（8±1 mg CH4m−2d−1）。自上而下和自下而上估算结果的差异与通量足迹中湿地面积的增加和地表温度的升高有关。当通量足迹中湿地面积小于10%分数覆盖度时，自上而下和自下而上的估算值均在测量误差范围内。这一结果首次在区域尺度上对农业甲烷排放清单进行了独立验证。利用提供空间分辨通量的小波分析，试图从管理和非管理的ch4源中分离ch4排放。讨论了利用飞机通量测量系统验证农业甲烷排放清单所面临的挑战。
Agriculture is estimated to produce more than 40% of anthropogenic methane (CH4) emissions, contributing to global climate change. Bottom-up, IPCC based methodologies are typically used to estimate the agriculture sector’s contribution, but these estimates are rarely verified beyond the farm gate, due to the challenge of separating interspersed sources. We present flux measurements of CH4,using eddy covariance (EC), relaxed eddy accumulation (REA) and wavelet covariance obtained using an aircraft-based measurement platform and compare these top-down estimates with bottom-up footprint adjusted inventory estimates of CH4emissions for an agricultural region in eastern Ontario, Canada. Top-down CH4fluxes agree well (mean ± 1 standard error: EC = 17 ± 4 mg CH4m−2d−1; REA = 19 ± 3 mg CH4m−2d−1, wavelet covariance = 16 ± 3 mg CH4m−2d−1), and are not statistically different, but significantly exceed bottom-up inventory estimates of CH4emissions based on animal husbandry (8 ± 1 mg CH4m−2d−1). The discrepancy between top-down and bottom-up estimates was found to be related to both increasing fractional area of wetlands in the flux footprint, and increasing surface temperature. For the case when the wetland area in the flux footprint was less than 10% fractional coverage, the top-down and bottom-up estimates were within the measurement error. This result provides the first independent verification of agricultural methane emissions inventories at the regional scale. Wavelet analysis, which provides spatially resolved fluxes, was used to attempt to separate CH4emissions from managed and unmanaged CH4sources. Opportunities to minimize the challenges of verifying agricultural CH4emissions inventories using aircraft flux measuring systems are discussed.