Tyndall Centre for Climate Change Research, School of Environmental Sciences, University of East Anglia, Norwich, UK.
Department of Geography, University of Zurich, Zürich, Switzerland.
Nat Commun. 2020 Jun 3;11(1):2791. doi: 10.1038/s41467-020-16576-z.
Black carbon (BC) is a recalcitrant form of organic carbon (OC) produced by landscape fires. BC is an important component of the global carbon cycle because, compared to unburned biogenic OC, it is selectively conserved in terrestrial and oceanic pools. Here we show that the dissolved BC (DBC) content of dissolved OC (DOC) is twice greater in major (sub)tropical and high-latitude rivers than in major temperate rivers, with further significant differences between biomes. We estimate that rivers export 18 ± 4 Tg DBC year globally and that, including particulate BC fluxes, total riverine export amounts to 43 ± 15 Tg BC year (12 ± 5% of the OC flux). While rivers export ~1% of the OC sequestered by terrestrial vegetation, our estimates suggest that 34 ± 26% of the BC produced by landscape fires has an oceanic fate. Biogeochemical models require modification to account for the unique dynamics of BC and to predict the response of recalcitrant OC export to changing environmental conditions.
黑碳（BC）是由景观火灾产生的一种顽固有机碳（OC）形式。BC 是全球碳循环的重要组成部分，因为与未燃烧的生物源 OC 相比，它在陆地和海洋库中被选择性地保存。在这里，我们表明，在主要（亚热带和高纬度）河流中，溶解有机碳（DOC）中的溶解 BC（DBC）含量是主要温带河流的两倍，并且在生物群系之间存在进一步的显著差异。我们估计全球河流每年排放 18±4Tg 的 DBC，包括颗粒态 BC 通量，总河川排放量为 43±15Tg 的 BC 年（OC 通量的 12±5%）。虽然河流每年仅排放出陆地植被固定 OC 的 1%，但我们的估计表明，景观火灾产生的 BC 中有 34±26%最终进入海洋。生物地球化学模型需要进行修改，以考虑到 BC 的独特动态，并预测对变化的环境条件下难降解 OC 排放的响应。
