New insights on black carbon in pelagic Atlantic sediments

IF 3 3区地球科学 Q2 CHEMISTRY, MULTIDISCIPLINARY

Marine Chemistry Pub Date : 2023-09-12 DOI:10.1016/j.marchem.2023.104312

Kari St.Laurent , Mark Cantwell , Rainer Lohmann

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Abstract

Black carbon (BC) is ubiquitous in pelagic sediments and presumed to have an older radiocarbon age due to long ocean residence times and pre-aging in terrestrial soils. Here, we analyzed sediments from five regions in the subtropical Atlantic Ocean to quantify the black carbon fraction of the total organic carbon pool. Black carbon, derived from the chemothermal oxidation method, comprised between 17 ± 6% of the sedimentary organic carbon in the Northwest Argentina Basin and 65 ± 18% in the Amazon Delta. Black carbon sediment accumulation rates were six times greater in the Sierra Leone Rise (8.4 ± 4.1 mg cm⁻² kyr⁻¹) compared to the remote Northwest Argentina Basin (1.3 ± 0.4 mg cm⁻² kyr⁻¹), possibly due to enhanced regional atmospheric deposition from annual African grassland fires. The radiocarbon age for BC from subtropical Atlantic sediments were more modern compared to the bulk total organic carbon, and BC source was apportioned as biomass burning byproducts from their stable carbon isotopic signatures and characteristic ratios of polycyclic aromatic hydrocarbons. This study demonstrated that subtropical Atlantic Ocean sediments serve as an important sink for young BC.

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对远洋大西洋沉积物中黑碳的新认识

黑碳（BC）在远洋沉积物中普遍存在，由于海洋停留时间长和在陆地土壤中预老化，被认为具有较老的放射性碳年龄。在这里，我们分析了亚热带大西洋五个地区的沉积物，以量化总有机碳库中的黑碳部分。黑碳来源于化学热氧化法，在阿根廷盆地西北部占沉积有机碳的17±6%，在亚马逊三角洲占65±18%。与偏远的阿根廷西北盆地（1.3±0.4 mg cm−2 kyr−1）相比，塞拉利昂海隆的黑碳沉积物积累率（8.4±4.1 mg cm−1 kyr−2）高出六倍，这可能是由于每年非洲草原大火增强了区域大气沉积。与总有机碳相比，亚热带大西洋沉积物中BC的放射性碳年龄更为现代，BC来源根据其稳定的碳同位素特征和多环芳烃的特征比例被分配为生物质燃烧副产物。这项研究表明，亚热带大西洋沉积物是年轻BC的重要汇点。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Marine Chemistry 化学-海洋学

CiteScore

6.00

自引率

3.30%

发文量

审稿时长

4.5 months

期刊介绍： Marine Chemistry is an international medium for the publication of original studies and occasional reviews in the field of chemistry in the marine environment, with emphasis on the dynamic approach. The journal endeavours to cover all aspects, from chemical processes to theoretical and experimental work, and, by providing a central channel of communication, to speed the flow of information in this relatively new and rapidly expanding discipline.