Distribution, Source and Burial of Black Carbon in the Aleutian Trench: Local Effects and Global Implication

Recent studies of low‐ and mid‐latitude trench systems have identified the hadal zone, the deepest region of the ocean, as a significant sink for black carbon (BC). However, the BC in high‐latitude trenches remains largely unexplored. In this study, we employed the chemothermal oxidation method (CTO‐375), benzene polycarboxylic acid (BPCA) analysis, and carbon isotope ( δ 13 C) to quantify the content and composition of BC in 11 sediment cores collected from the Aleutian Trench, the northernmost hadal trench. The BC CTO content ranged from 0.08% to 0.27%, with higher concentrations observed in the eastern and central sections compared to the western section. The mean BC to total organic carbon ratio was 0.30 ± 0.06, significantly higher than the value reported for low‐ and mid‐latitude trenches (0.12 ± 0.04). The mixing stable isotope analysis in R (MixSIA) based on δ 13 C BC indicated that fossil fuel combustion is the primary regional source of BC, accounting for 72%–78%. The estimated accumulation rate of BC in the Aleutian Trench was 0.9 ± 0.1 g m −2 yr −1 , which is twice the previously reported average for low‐ and mid‐latitude trench regions. When scaled to the hadal region of the Aleutian Trench, this corresponds to a burial rate of 0.08 ± 0.03 Tg per year. Our findings underscore the distinctive nature of the Aleutian Trench regarding carbon transport and burial. Although significant spatial variability may occur at both inter‐ and intra‐trench scales, our study supports the importance of hadal environments as sinks for BC.