The isotope tracer technique plays a key role in identifying the sources and atmospheric processes affecting pollution. The sources of brown carbon (BrC) at Guangzhou during 2017–2018 were characterized by positive matrix factorization with radiocarbon isotope constraints and multiple linear regression analysis. The primary emission factors of fossil fuel combustion (FF) and biomass burning (BB) accounted for 34% and 27% of dissolved BrC absorption at λ = 365 nm (Abs₃₆₅), respectively. The total mean light absorption contributed by secondary sources was 39%. The FF‐origin Abs₃₆₅ changed insignificantly throughout the year and was dominant in the summer monsoon period, whereas the Abs₃₆₅ from BB and secondary nitrate formation increased and contributed larger fractions during the winter monsoon period. Transported BrC was estimated using an index of ⁷Be/(⁷Be + n²¹⁰Pb). Higher values were generally accompanied by lower Abs₃₆₅, whereas lower values were associated with higher Abs₃₆₅, indicating that BrC absorption of aerosols transported from the upper‐atmosphere is lower than that of aerosols transported near the surface. Based on the positive correlations between ²¹⁰Pb and Abs₃₆₅ and non‐fossil dissolved organic carbon in the winter monsoon period, we estimated that the contribution of invasive BrC (include ground and upper‐atmosphere level) to total absorption during the period of elevated BrC was ∼50%. The transported BrC was likely related to BB organic aerosols and secondary nitrate formation processes. This study supports radionuclides as a novel method for characterizing the sources and transport of BrC that can be applied in future atmospheric research.

中文翻译：

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使用放射性核示踪剂和模型确定棕色碳的来源和运输

同位素示踪技术在确定影响污染的来源和大气过程中起着关键作用。广州市2017-2018年间褐碳（BrC）的来源特征是具有放射性碳同位素约束的正矩阵分解和多元线性回归分析。化石燃料燃烧（FF）和生物质燃烧（BB）的主要排放因子分别占λ  = 365 nm（Abs ₃₆₅）时溶解的BrC吸收的34％和27％。次级光源贡献的总平均光吸收为39％。FF起源的Abs _365全年变化不大，在夏季风季期间占主导地位，而Abs ₃₆₅冬季季风期间，BB和次生硝酸盐的形成增加并贡献了较大的比例。使用⁷ Be /（⁷ Be + n ²¹⁰ Pb）的指数估算运输的BrC 。较高的值通常伴随着较低的Abs ₃₆₅，而较低的值则伴随着较高的Abs ₃₆₅，这表明从高大气层输送的气溶胶的BrC吸收低于在地面附近输送的气溶胶的BrC吸收。基于²¹⁰ Pb和Abs ₃₆₅之间的正相关以及冬季季风期间非化石溶解的有机碳，我们估计在BrC升高期间，侵入性BrC（包括地面和高层大气水平）对总吸收的贡献约为50％。运送的BrC可能与BB有机气溶胶和二次硝酸盐形成过程有关。这项研究支持放射性核素作为表征BrC的来源和传输的新方法，可用于未来的大气研究中。