The hadal trenches (>6000 m) are considered to be ultimate sinks of organic carbon (OC) from biosphere. However, highly spatial heterogeneity of geographic background and organic matter in different zones make significant influences on the OC cycling, and further the carbon burial. In this study, three sediment cores were drilled across the northern Yap Trench axis (9.8–9.9°N, 138.3–138.7°E). The elemental compositions, stable carbon isotopes of organic matter, mineral-specific surface area, and grain size composition were analyzed to investigate the spatial variations of organic sources, distribution, and its degradation in the northern Yap Trench. The surface sedimentary OC (SOC) contents in the northern Yap Trench increase from 0.25% at abyssal depth (4435 m) to 0.50% at hadal depth (~6674 m). Higher OC content (0.27% ± 0.08%) and sedimentation rate (5.8 cm kyr⁻¹) occur in the station on the gradual oceanward slope (~4.2°) compared to those on the steep landward slope (~10°) (0.17% ± 0.13%, 0.52–1.8 cm kyr⁻¹), suggesting enhanced accumulation of OC on the gradual slope. The allochthonous OC (i.e. marine phytoplankton-derived (55% ± 7%) and terrestrial (16% ± 8%)) dominates the SOC pool on the oceanward slope, whereas autochthonous microbe reworked OC contributes more than 50% in the steep landward slope, based on the evaluation of a three-end-member mixing model using δ¹³C composition and OC/N ratios as source markers. Correspondingly, radiocarbon age of SOC in the gradual slope is ~700 years younger than that in the steep slope with similar depth, indicating that the relatively fresh allochthonous OC is selectively deposited on the gradual slope. A multi-G degradation model demonstrates that OC degradation rates in the northern Yap Trench range from 0.00015 yr⁻¹ to 0.00068 yr⁻¹, which can be comparable with abyssal plain (3000–6000 m) and are lower than those of neritic environments (<1000 m). Mass accumulation model calculation shows that accumulation rate of surface OC in the northern Yap trench is ~2.7 × 10⁻² g C m⁻² yr⁻¹, much lower than those from other deep ocean seafloors. This study suggests an inefficient SOC preservation within the northern Yap Trench, which might be induced by high labile marine phytoplankton-derived OC inputs and active heterotrophic microbial activity, and the results have important implications for better understanding the effects of sediment dynamics on OC cycling in hadal zones.

地下沟（> 6000 m）被认为是生物圈中有机碳（OC）的最终汇。但是，不同区域的地理背景和有机质在空间上的高度异质性对OC循环以及碳埋藏有重大影响。在这项研究中，在北雅浦海沟轴线（9.8-9.9°N，138.3-138.7°E）上钻了三个沉积物岩心。通过分析元素的组成，有机质的稳定碳同位素，矿物比表面积和晶粒尺寸组成，研究了北邑沟北部有机源的空间变化，分布及其降解。Yap海沟北部的表面沉积OC（SOC）含量从深渊深度（4435 m）的0.25％增加到海底深度（〜6674 m）的0.50％。OC含量较高（0.27％±0。^-1）发生在站台上，逐渐向海倾斜（〜4.2°），而陡峭的陆上倾斜（〜10°）（0.17％±0.13％，0.52–1.8 cm kyr ^-1），表明OC逐渐倾斜。异源OC（即海洋浮游植物来源的（55％±7％）和陆生的OC（16％±8％））在海向斜坡上的SOC池中占主导地位，而土生微生物重做的OC在陡峭的陆上斜坡上的贡献超过50％的基础上，一个三端员混合模型的使用δ评价¹³C成分和OC / N比作为来源标记。相应地，与坡度相似的陡坡相比，坡度SOC的放射性碳年龄要年轻约700岁，这表明较新鲜的异质OC有选择地沉积在坡度上。多重G降解模型表明，北部Yap海沟的OC降解率范围为0.00015 yr ^-1至0.00068 yr ^-1，可以与深海平原（3000-6000 m）相媲美，并且低于苛刻环境（ <1000 m）。物质积累模型计算表明，Yap北部沟渠表面OC的积累率为〜2.7×10 ^-2  g C m ^-2  yr ^-1，远低于其他深海海底的。这项研究表明，北雅普海沟内的SOC保藏效率低下，这可能是由不稳定的海洋浮游植物来源的OC输入和活跃的异养微生物活动引起的，其结果对于更好地了解沉积物动力学对OC循环的影响具有重要意义。哈达尔区。