Estimating Upper Silesian coal mine methane emissions from airborne in situ observations and dispersion modeling

摘要

Abundant mining and industrial activities located in the Upper Silesian Coal Basin (USCB) lead to large emissions of the potent greenhouse gas (GHG) methane (CH 4 ). The strong localization of CH 4 emitters (mostly confined to known coal mine ventilation shafts) and the large emissions of 448 and 720? kt?CH 4 ?yr ?1 reported in the European Pollutant Release and Transfer Register (E-PRTR?2017) and the Emissions Database for Global Atmospheric Research (EDGAR?v4.3.2), respectively, make the USCB a prime research target for validating and improving CH 4 flux estimation techniques. High-precision observations of this GHG were made downwind of local (e.g., single facilities) to regional-scale (e.g.,?agglomerations) sources in the context of the CoMet 1.0 campaign in early summer 2018. A quantum cascade–interband cascade laser (QCL–ICL)-based spectrometer adapted for airborne research was deployed aboard the German Aerospace Center (DLR) Cessna 208B to sample the planetary boundary layer (PBL) in situ. Regional CH 4 emission estimates for the USCB are derived using a model approach including assimilated wind soundings from three ground-based Doppler lidars. Although retrieving estimates for individual emitters is difficult using only single flights due to sparse data availability, the combination of two flights allows for exploiting different meteorological conditions (analogous to a sparse tomography algorithm) to establish confidence on facility-level estimates. Emission rates from individual sources not only are needed for unambiguous comparisons between bottom-up and top-down inventories but also become indispensable if (independently verifiable) sanctions are to be imposed on individual companies emitting GHGs. An uncertainty analysis is presented for both the regional-scale and facility-level emission estimates. We find instantaneous coal mine emission estimates of 451/423? ± ?77 / 79? kt?CH 4 ?yr ?1 for the morning/afternoon flight of 6?June?2018. The derived fuel-exploitation emission rates coincide ( ± 6? % ) with annual-average inventorial data from E-PRTR?2017 although they are distinctly lower ( ?28 ? % / ?32 ? % ) than values reported in EDGAR?v4.3.2. Discrepancies in available emission inventories could potentially be narrowed down with sufficient observations using the method described herein to bridge the gap between instantaneous emission estimates and yearly averaged inventories.