Organic aerosol (OA) constitutes a substantial fraction of fine particles and affects both human health and climate. It is becoming clear that OA absorbs light substantially (hence termed Brown Carbon, BrC), adding uncertainties to global aerosol radiative forcing estimations. The few current radiative-transfer and chemical-transport models that include BrC primarily consider sources from biogenic and biomass combustion. However, radiocarbon fingerprinting here clearly indicates that light-absorbing organic carbon in winter Beijing, the capital of China, is mainly due to fossil sources, which contribute the largest part to organic carbon (OC, 67 ± 3%) and its sub-constituents (water-soluble OC, WSOC: 54 ± 4%, and water-insoluble OC, WIOC: 73 ± 3%). The dual-isotope (Δ14C/δ13C) signatures, organic molecular tracers and Beijing-tailored emission inventory identify that this fossil source is primarily from coal combustion activities in winter, especially from the residential sector. Source testing on Chinese residential coal combustion provides direct evidence that intensive coal combustion could contribute to increased light-absorptivity of ambient BrC in Beijing winter. Coal combustion is an important source to BrC in regions such as northern China, especially during the winter season. Future modeling of OA radiative forcing should consider the importance of both biomass and fossil sources.
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机译：有机气溶胶（OA）构成了很大一部分的细小颗粒，并影响人类健康和气候。越来越明显的是，OA会大量吸收光（因此称为棕碳，BrC），为全球气溶胶辐射强迫估算增加了不确定性。目前包括BrC在内的少数几种辐射传递和化学传递模型主要考虑来自生物和生物质燃烧的来源。但是，这里的放射性碳指纹图谱清楚地表明，在中国首都北京冬季，吸收光的有机碳主要来自化石源，这些化石源对有机碳及其亚成分的贡献最大（OC，67％±3％） （水溶性OC，WSOC：54±4％，水不溶性OC，WIOC：73±3％）。双同位素（Δ 14 C /δ 13 C）特征，有机分子示踪剂和北京量身定做的排放量清单表明，这种化石源主要来自新疆的燃煤活动。冬天，尤其是住宅领域。对中国居民用煤燃烧的源测试提供了直接的证据，表明密集的煤燃烧可能有助于增加北京冬季周围BrC的光吸收率。在中国北方等地区，尤其是在冬季，燃煤是BrC的重要来源。 OA辐射强迫的未来建模应考虑生物量和化石源的重要性。
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