Black carbon (BC) has emerged as an integral part of the global carbon (C) cycle, constituting 12% ± 5% of the organic C pool in rivers and soils, with the potential to generate negative climate feedback. However, its ability to sequester C depends on the recalcitrant nature of BC in the environment, which is under debate. Using CTO-375 method and by measuring concentrations and isotopic compositions of particulate BC (δ¹³C_PBC), we explore the transformation of particulate black carbon (PBC) along the atmosphere-river-ocean continuum. Significantly high δ¹³C_PBC in the ocean compared to rivers and atmospheric particulate matter indicates (a) degradation of PBC, potentially through photodegradation and leaching, and/or (b) availability of an enriched source other than fluvial or aeolian inputs. This evidence for degradation of PBC in aquatic systems warrants rethinking on its C sequestration potential and role in aquatic C biogeochemistry and further raises concerns regarding the use of sedimentary BC as a paleoenvironmental proxy.

中文翻译：

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海洋中颗粒状黑碳降解的同位素证据

黑碳 (BC) 已成为全球碳 (C) 循环的一个组成部分，占河流和土壤中有机碳库的 12% ± 5%，有可能产生负气候反馈。然而，其隔离 C 的能力取决于 BC 在环境中的顽固性质，这一点尚有争议。利用CTO-375方法，通过测量颗粒BC（δ ¹³ C _PBC）的浓度和同位素组成，我们探索了颗粒黑碳（PBC）沿大气-河流-海洋连续体的转化。与河流和大气颗粒物相比，海洋中的 δ ¹³ C _PBC显着升高，表明 (a) PBC 可能通过光降解和浸出而降解，和/或 (b) 除河流或风成输入之外还存在富集来源。 PBC 在水生系统中降解的证据值得重新思考其碳封存潜力和在水生碳生物地球化学中的作用，并进一步引起了对使用沉积物碳化物作为古环境替代物的担忧。