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

含碳燃料不完全燃烧产生的黑碳(BC)是导致气候变化和降低区域空气质量的两大大气污染物之一。BC的升温潜力仅次于CO2，由于其在大气中的保留时间较短，以及对各种排放源的混合、沉积和贡献知之甚少，因此对气候模拟的不确定性最大。化石燃料和生物质燃烧产生的BC具有不同的光吸收特性和老化过程，因此具有不同的升温潜势。因此，改进源特征对于确定目标、制定缓解战略以及提高气候模型中人为气溶胶输入的准确性至关重要。然而，传统的自下而上的排放清单(EI)方法存在着固有的局限性，如排放因子不准确、源/汇覆盖不完整导致很大的不确定性。*本研究旨在开发一种创新的、基于14C-13C的自上而下方法来将BC分配到主要源，因为该方法消除了测量排放因子或全面调查源的需要。近期的目标是通过改进实验程序来建立这种方法，通过在艾伯塔省进行一项试点研究，将干扰水平降至最低或量化，加拿大BC的三分之一来自多个相互竞争的来源。分子示踪研究结合遥感数据和气团轨迹分析，将在野火季节验证该方法的结果。为了解释自下而上和自上而下两种方法之间的差异，设计了一种机理研究来研究这两种类型的生物滤池的去除机理。中长期目标是将这种方法应用于加拿大重要的BC排放区的调查，以建立一个包含源解析的BC排放量的多区域数据库，在此基础上将评估来源分异的BC对区域气候的影响。*这项研究的结果有望给BC社区带来立竿见影的好处，因为这种方法具有更强的适应性，可能被世界上其他重要排放区的其他研究采用。从中长期来看，这项研究中收集的数据集将通过提供更准确的源参数来更好地模拟加拿大的气候系统。模拟结果将反过来通过为自下而上的排放清单提供具体的约束来影响监管部门，这将帮助政策制定者通过选择适当的目标部门来制定针对黑碳的区域定制的缓解战略。

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.***