A top-down approach for apportioning black carbon aerosols to emission sources in regions with multiple competing contributors

黑碳是由含碳燃料不完全燃烧产生的，是导致气候变化和降低区域空气质量的两大空气污染物之一。由于其在大气中的停留时间短，以及对各种排放源的混合、沉积和贡献的了解甚少，其增温潜势仅次于CO2，因此对气候模拟的不确定性最大。来自化石燃料和生物质燃烧的BC具有不同的光吸收特性和老化过程，因此具有不同的变暖潜势。因此，改进源表征对于确定目标、制定减缓策略以及提高气候模式中输入人为气溶胶的准确性至关重要。然而，传统的自下而上的排放清查（EI）方法存在固有的局限性，如排放因子不准确，源/汇覆盖不全，导致较大的不确定性。*******本研究旨在开发一种创新的，基于双同位素（14C-13C）的自上而下的方法来分配BC到主要来源，因为这种方法消除了测量排放因子或综合测量来源的需要。最近的目标是通过改进实验程序来建立方法，通过在阿尔伯塔省进行的一项试点研究来最大限度地减少或量化干扰水平，其中加拿大BC的1/3来自多个竞争源。分子示踪剂研究结合遥感数据和气团轨迹分析将有助于在野火季节验证该方法的结果。机制研究旨在探讨两种类型BC的清除机制，以解释自下而上和自上而下方法的差异。中长期目标是将该方法应用于调查加拿大重要的BC排放区域，以构建包含源解析BC排放的多区域数据库，并在此基础上评估源分化BC对区域气候的影响。*******这项研究的结果预计将为BC社区带来直接的好处，因为这种方法具有更高的适应性，可以被其他研究采用，在世界上其他重要的排放区域采购BC。从中长期来看，本研究收集的数据集将提供更精确的源参数化，从而更好地模拟加拿大气候系统。模拟结果将反过来影响监管部门，为自下而上的排放清单提供具体限制，这将有助于决策者通过选择合适的目标部门，制定适合区域的黑碳缓解战略

Black carbon (BC), generated from incomplete combustion of carbonaceous fuels, is one of the two major airborne pollutants that drive climate change and degrade regional air quality. With a warming potential second to CO2, BC contributes the most uncertainty to climate modeling due to its short retention time in the atmosphere and poorly understood mixing, deposition, and contribution from various emission sources. BC from fossil fuel and biomass burning possesses distinct light absorbing properties and aging processes, and hence differing warming potentials. Therefore, improved source characterization is crucial for determining targets, formulating mitigation strategies, and increasing the accuracy of input anthropogenic aerosols in climate models. However, conventional bottom-up emission inventory (EI) methods have intrinsic limitations such as inaccurate emission factors, incomplete coverage of sources/sinks that cause large uncertainties.*******This research aims to develop an innovative, dual-isotope (14C-13C) based top-down approach to apportion BC to major sources as this approach eliminates the need of measuring emission factors or comprehensive surveying of sources. The near objective is to establish the method by improving the experimental procedures to minimize or quantify the level of interferences through a pilot study in Alberta where 1/3 of Canada BC is emitted from multiple competing sources. Molecular tracer studies combined with remote sensing data and air mass trajectory analysis will serve to validate the results of this method during the wildfire season. A mechanistic study is designed to investigate the removal mechanism of the two types of BC, so as to explain the discrepancy between the bottom-up and top-down approaches. The mid- and long term objectives are to apply this approach for investigating important BC emission regions in Canada to construct a multi-region database containing source-resolved BC emissions, based on which the impact of source-differentiated BC on the regional climate will be assessed.*******The outcome of this research is anticipated to bring immediate benefit to the BC community in that this method, with increased adaptivity, can possibly be adopted by other researches for sourcing BC at other important emission regions in the world. In the mid-long run, the datasets to be collected in this research will enable a better simulation of the Canadian climate system by providing more accurate source parameterization. The simulation results will in turn impact the regulatory sector by providing specific constraints for bottom-up emission inventories, which will assist policymakers to develop regionally tailored mitigation strategies for black carbon by selecting the right sector to target.***