北极拉普捷夫海夏、秋季颗粒有机碳的分布与来源

Distribution and source of particulate organic carbon in the Arctic Laptev Sea during late summer and early fall

随着全球变暖的加剧,北极陆架边缘海碳的源汇过程对全球碳循环的影响及其气候环境效应日益显著。拉普捷夫海作为北冰洋典型的陆架边缘海,在大河、海冰、海洋初级生产力及海岸侵蚀的影响下,该区沉积有机碳的来源、输运和埋藏等过程独具特色。本文基于2018年中俄第二次北极联合科考获得的悬浮颗粒物样品和水文资料,研究了夏末秋初拉普捷夫海颗粒有机碳的分布特征、来源及其影响因素。结果表明,颗粒有机碳(POC)的浓度位于35.27~1 185.58μg/L之间,平均为172.65μg/L。受河流输入、海岸侵蚀和海洋初级生产力的影响,表层POC浓度分布呈现近岸高、远岸低趋势;底层POC浓度分布主要受控于沉积再悬浮作用,高浓度POC出现在勒拿河三角洲的东部区域。总悬浮颗粒物浓度与POC浓度总体呈显著正相关,显示出其对POC空间分布的直接影响,且两者在底层中的相关性要高于表层,表明不同层位的POC可能存在来源差异。研究区POC的δ^(13)C值处于-31.03‰~-25.79‰之间,表层δ^(13)C值较底层明显偏负,且部分站位的δ^(13)C值甚至低于周边陆源有机碳的端元,这反映了可能除陆源输入的贡献外,近海浮游植物直接利用大量陆源有机质降解产生的溶解无机碳的过程也对该区域POC的供应和来源解析具有重要的影响。

With the intensification of global warming, the source sink process of carbon in the Arctic shelf-edge sea is becoming more and more important in the study of global carbon cycle. As a typical continental shelf marginal sea in the Arctic Ocean, the source, transportation and burial of sedimentary organic carbon in this area are unique under the influence of rivers, sea ice, marine primary productivity and coastal erosion. Based on the sampling of suspended particulate matter(SPM) and hydrological data obtained from the second Sino-Russian Arctic joint expedition during late summer and early fall in 2018, we foucus on the distribution characteristics, sources and influencing factors of particulate organic carbon(POC) in the Laptev Sea. The results show that POC ranges from35.27 μg/L to 1 185.58 μg/L, with an average of 172.65 μg/L. Under the effect of river input, coastal erosion and marine primary productivity, the distribution of surface POC shows a decreased trend from near shore towards offshore;the bottom POC is mainly controlled by sediments resuspension, and the high content of POC appears in the east of Lena River Delta. There was a significant positive correlation between SPM concentration and POC concentration, indicating its direct impact on the occurrence of POC;a more positive relation is found among the bottom layer samples, which may indicate the varied origin of POC in different layers. The value of δ^(13)CPOC in study area value is between-31.03‰ and-25.79‰, and the value of δ^(13)C in surface layers is obviously depleted compared with the bottom layer, which is even lower than the end-member of the surrounding terrestrial contributor, suggesting that these POC is not derived from land-based origin. The utilization of the terrestrial POC degraded dissolved inorganic carbon by offshore phytoplankton maybe responsible for this depletion of δ^(13)C offshore, which could also be an important process on the supply and source apportionment of POC in this Arctic coastal area.