A methodological study on the analysis of organic matter associated with iron oxides in marine sediments

IF 3.1 3区地球科学 Q1 GEOCHEMISTRY & GEOPHYSICS

Applied Geochemistry Pub Date : 2025-02-01 DOI:10.1016/j.apgeochem.2025.106295

Milad Ezzati , Yves Gélinas

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Abstract

Coastal shelves significantly contribute to the burial of natural organic matter (NOM) in marine sediments, with about 21.5 ± 8.6% of NOM associated with reactive iron oxides, which preserve NOM from biodegradation. Quantifying this preserved NOM requires a method to release bound carbonaceous molecules from iron minerals. The citrate-bicarbonate-dithionate (CBD) method is commonly used to liberate NOM from iron oxides through reductive dissolution. This method includes a control experiment using an NaCl solution to distinguish NOM associated with iron oxides from that leaching out from other minerals. This study aims to determine if desorbed NOM during the control experiment comes from other minerals or is loosely bound to iron oxides. We synthesized lepidocrocite (γ-FeOOH) in the presence and absence of plankton-extracted NOM to mimic sorption and conducted similar experiments on kaolinite, montmorillonite, and their mixture, representing common clay minerals in sediments. Quantifying the carbon content revealed that NOM associated with γ-FeOOH is 1.5–9.0 times greater than with other minerals. Post-treatment results indicate a 22.2%–42.7% loss of NOM associated with iron oxides, suggesting that deducting NOM lost during the control step underestimates the amount of carbon preserved by iron minerals in marine sediments.

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沿海陆架对海洋沉积物中天然有机物（NOM）的埋藏起了重要作用，约 21.5 ± 8.6% 的天然有机物与活性氧化铁有关，活性氧化铁可使天然有机物免于生物降解。要量化这些保存下来的 NOM，需要一种从铁矿物中释放出结合碳质分子的方法。柠檬酸盐-碳酸氢盐-二硫酸盐（CBD）法通常用于通过还原溶解从氧化铁中释放 NOM。该方法包括一个使用氯化钠溶液的对照实验，以区分与铁氧化物相关的 NOM 和从其他矿物中沥滤出的 NOM。本研究旨在确定对照实验中脱附的 NOM 是来自其他矿物还是与铁氧化物松散结合。我们在浮游生物提取的 NOM 存在和不存在的情况下合成了鳞片铁氧体（γ-FeOOH）来模拟吸附，并对高岭石、蒙脱石及其混合物（代表沉积物中常见的粘土矿物）进行了类似的实验。对碳含量进行量化后发现，与 γ-FeOOH 相关的 NOM 是其他矿物的 1.5-9.0 倍。后处理结果表明，与铁氧化物相关的 NOM 损失了 22.2%-42.7%，这表明扣除控制步骤中损失的 NOM 会低估海洋沉积物中铁矿物保存的碳量。

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

Applied Geochemistry 地学-地球化学与地球物理

CiteScore

6.10

自引率

8.80%

发文量

272

审稿时长

65 days

期刊介绍： Applied Geochemistry is an international journal devoted to publication of original research papers, rapid research communications and selected review papers in geochemistry and urban geochemistry which have some practical application to an aspect of human endeavour, such as the preservation of the environment, health, waste disposal and the search for resources. Papers on applications of inorganic, organic and isotope geochemistry and geochemical processes are therefore welcome provided they meet the main criterion. Spatial and temporal monitoring case studies are only of interest to our international readership if they present new ideas of broad application. Topics covered include: (1) Environmental geochemistry (including natural and anthropogenic aspects, and protection and remediation strategies); (2) Hydrogeochemistry (surface and groundwater); (3) Medical (urban) geochemistry; (4) The search for energy resources (in particular unconventional oil and gas or emerging metal resources); (5) Energy exploitation (in particular geothermal energy and CCS); (6) Upgrading of energy and mineral resources where there is a direct geochemical application; and (7) Waste disposal, including nuclear waste disposal.