Abstract The fate of terrigenous organic carbon (OCterr) in the ocean remains an enigma for four decades. Hadal trenches, the deepest ocean realm (6–11 km deep), were recently proposed to be OC depocenters, but whether and how much OCterr was sequestrated there remain elusive. Here we conducted comprehensive analyses for four sediment cores from the New Britain Trench (NBT) close to Papua New Guinea to assess source, translocation and burial of OC. The bulk and molecular radiocarbon data suggest that the NBT landward slope and axis sediments mainly receive young and biogenic rather than petrogenic OC. The three-endmember mixing model based on Δ14C, δ13C and OC contents reveals that sediments of the NBT axis (8225 m) comprise relatively high OC contents (0.66 ± 0.08%), of which biogenic OCterr accounts for 62 ± 10%. The high proportion of biogenic OCterr was attributed to the selective translocation of OCterr-enriched coarse particles and rapid delivery of sediments supported by unique V-shape feature of the trench. In contrast, the sediment OC at the oceanward slope is primarily of a marine origin, suggesting that OCterr was efficiently trapped in the trench bottom. It is estimated that the burial rate is 2.75 ± 0.32 g C m−2 yr−1 for OC and 1.69 ± 0.41 g C m−2 yr−1 for OCterr in the NBT. Given a fact that many trenches are close to the landmasses, we propose that the hadal trenches may contribute significantly to the burial of OCterr in the ocean.

中文翻译：

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新不列颠海沟陆源有机碳的有效封存

摘要 四十年来，海洋中陆源有机碳 (OCterr) 的命运一直是个谜。哈达尔海沟，最深的海洋领域（6-11 公里深），最近被提议作为 OC 沉积中心，但是否以及有多少 OCterr 被隔离在那里仍然难以捉摸。在这里，我们对来自巴布亚新几内亚附近的新不列颠海沟 (NBT) 的四个沉积岩心进行了综合分析，以评估 OC 的来源、易位和埋藏。大量和分子放射性碳数据表明，NBT 陆坡和轴心沉积物主要接收年轻和生物而不是岩源 OC。基于Δ14C、δ13C和OC含量的三端元混合模型表明，NBT轴（8225 m）沉积物中OC含量相对较高（0.66±0.08%），其中生物OCterr占62±10%。高比例的生物 OCterr 归因于富含 OCterr 的粗颗粒的选择性易位和由沟渠独特的 V 形特征支持的沉积物的快速输送。相比之下，向海斜坡的沉积物 OC 主要来自海洋，这表明 OCterr 被有效地困在海沟底部。据估计，NBT 中 OC 的埋藏率为 2.75 ± 0.32 g C m-2 yr-1，OCterr 的埋藏率为 1.69 ± 0.41 g C m-2 yr-1。鉴于许多海沟靠近陆地的事实，我们提出，深海海沟可能对海洋中的 OCterr 埋葬做出了重大贡献。向海斜坡的沉积物 OC 主要来自海洋，这表明 OCterr 被有效地困在海沟底部。据估计，NBT 中 OC 的埋藏率为 2.75 ± 0.32 g C m-2 yr-1，OCterr 的埋藏率为 1.69 ± 0.41 g C m-2 yr-1。鉴于许多海沟靠近陆地的事实，我们认为，深海海沟可能对海洋中的 OCterr 埋葬做出了重大贡献。向海斜坡的沉积物 OC 主要来自海洋，这表明 OCterr 被有效地困在海沟底部。据估计，NBT 中 OC 的埋藏率为 2.75 ± 0.32 g C m-2 yr-1，OCterr 的埋藏率为 1.69 ± 0.41 g C m-2 yr-1。鉴于许多海沟靠近陆地的事实，我们认为，深海海沟可能对海洋中的 OCterr 埋葬做出了重大贡献。