东西伯利亚陆架炭屑分布特征及其控制因素

Charcoal distribution in surface sediments of the East Siberian Shelf and its controlling factors

炭屑是指示火灾事件的重要指标。全球变暖背景下,环北极地区野火频发,了解炭屑的产生、迁移和埋藏对理解北极气候变化的环境效应及陆源碳源汇过程具有重要意义,而前人对北极海域的炭屑研究十分匮乏。东西伯利亚陆架是全球最大的陆架区,接收和封存着巨量的陆源碳,也是海冰融化、沿岸侵蚀、周边野火频发最显著的地区,因此成为研究北极炭屑记录的重要区域。本文基于2016年首次中俄北极联合科学考察取得的表层沉积物样品,研究了东西伯利亚陆架区不同粒度炭屑的空间分布特征、输运方式及其控制因素。结果表明,东西伯利亚陆架区表层沉积物中炭屑总浓度为4.4×10^(4)~4.1×10^(6)粒·g^(–1),平均浓度为9.3×10^(5)粒·g^(–1)。沉积物中炭屑呈现近岸粗、远岸细的总体分布特征。由于受到水动力、大气等长距离搬运,研究区炭屑颗粒以超细粒为主(平均占83%)。河口水动力作用、沿岸侵蚀、大气传输、海冰搬运、水平向和垂向上的海流搬运等多重控制因素,可能共同影响炭屑的跨陆架输运过程。

Charcoal is a direct indicator of fire events.In the context of global warming and frequent circumpolar Arctic wildfires,the generation,migration and burial of charcoal are key elements contributing to the understanding of the environmental effects of Arctic climate change and the source–sink trajectory of terrestrial carbon.However,there are few studies on charcoal in the Arctic Ocean.The East Siberian Shelf(ESS)is the largest continental shelf in the world,receiving and sequestering large amounts of terrestrial carbon.It is also one of the Arctic regions where the melting of sea ice,coastal erosion,and wildfires are the most pronounced,making it a favorable area to study the charcoal record in the Arctic.On the basis of the surface sediment samples obtained from the first Sino-Russian joint Arctic research expedition in 2016,the distribution,concentration,relative abundance,transport process,and the controlling factors of charcoal on the ESS of different sizes were studied.The results show that the total concentration of charcoal in the ESS surface sediments lies between 4.4×10^(4) and 4.1×10^(6) grains·g^(–1),with an average of 9.3×10^(5) grains·g^(–1).Coarse charcoal particles were found near shore and fine particles were found offshore.As a result of long-distance transport by hydrodynamics and wind,charcoal particles in the study area are dominated by ultrafine grains(83%on average).River input,coastal erosion,atmospheric transport,sea ice and current processes may jointly influence the cross-shelf pathway of charcoal.