Sources and Fates of sedimentary polycyclic aromatic hydrocarbons along the East Siberian Arctic Shelf: Implications for input pathways and black carbon constraint

The East Siberian Arctic Shelf (ESAS) is undergoing faster climate changes such as the decreasing sea ice, thawing permafrost and wildfires, which elevated the polycyclic aromatic hydrocarbons (PAHs) levels in the Arctic Ocean, and this region is expected to become a potential PAHs sink in sediments. Here we investigated the spatial heterogeneity of deposition and fate of PAHs together with black carbon (BC) within the ESAS. Our results explored the mixed petrogenic and pyrogenic sources of PAH. Furthermore, we found that disparate input pathways led to distinct PAH fates in coastal and open-sea regions of the ESAS, and BC likely exerts significant constraints on the behavior and fates of PAH. These carbonaceous compounds in the western ESAS is mainly affected by terrestrial inputs such as fluvial discharge and permafrost erosion, while the open-sea regions of the eastern shelf are largely driven by atmospheric delivery and biological deposition. The strong signals of emissions from permafrost along the coastal margins highlight the importance of seriously considering permafrost erosion might become a potential PAH contributor, especially with climate changes.

东西伯利亚北极大陆架（East Siberian Arctic Shelf, ESAS）正经历着更为剧烈的气候变化，具体表现为海冰消退、永久冻土融化与野火频发，上述变化已导致北冰洋内多环芳烃（polycyclic aromatic hydrocarbons, PAHs）浓度升高，且该区域有望成为沉积物中多环芳烃的潜在汇。本研究针对东西伯利亚北极大陆架内多环芳烃与黑碳（black carbon, BC）的沉积空间异质性及其归趋展开了系统调查。研究结果揭示了多环芳烃兼具油源与热解源的混合成因特征。进一步分析发现，不同的输入路径使得东西伯利亚北极大陆架的近岸与远海区域呈现出截然不同的多环芳烃归趋，且黑碳可能对多环芳烃的环境行为与归趋产生显著约束作用。东西伯利亚北极大陆架西部的这类含碳化合物主要受河流径流、永久冻土侵蚀等陆源输入影响，而东部大陆架的远海区域则主要由大气输送与生物沉积作用主导。沿海岸带区域的永久冻土排放信号显著，这凸显出在气候变化背景下，永久冻土侵蚀或成为多环芳烃的潜在贡献源，该问题亟需得到足够重视。