广西红树林表层沉积物中活性铁氧化物对有机碳的保存  

The preservation of organic carbon by active iron oxides in surface sediments from Guangxi mangroves

作　　者：相志远 张芬芬[1] 魏金娥 杜金洲[1] Xiang Zhiyuan;Zhang Fenfen;Wei Jine;Du Jinzhou(State Key Laboratory of Estuarine and Coastal Research,East China Normal University,Shanghai 200241,China)

机构地区：[1]华东师范大学河口海岸学国家重点实验室,上海200241

出　　处：《海洋学报》2024年第11期13-33,共21页

基　　金：国家重点研发计划项目“气候变化和人类活动对海上丝路沿线国家滨海蓝碳生态系统的耦合影响机制与合作研究”(2022YFE0209300);国家自然科学基金面上项目“北部湾典型砂质海岸海底地下水溶解有机碳结构组成及其入海通量研究”(No.41373119)。

摘　　要：铁氧化物在全球土壤(沉积物)有机碳(Organic Carbon,OC)存储中具有重要作用。红树林湿地同时具有陆源与海源输入,为活性铁氧化物(Fe_(R))对OC的保存提供了独特的生境。然而红树林表层沉积物中Fe_(R)对OC保存过程中的影响因素以及Fe_(R)对OC组分的选择性尚不明确。本研究选择广西大风江入海口和茅尾海周围受到潮汐与河流影响的天然红树林生境中的表层沉积物,研究沉积物中铁结合有机碳(Fe-OC)含量以及组分的变化。结果表明,大风江入海口与茅尾海表层沉积物中Fe-OC平均含量分别为0.16%±0.07%与0.17%±0.07%,在总有机碳(TOC)中所占比例(f_(Fe-OC))分别为16.2%±5.04%与10.9%±5.63%,主要保存方式为吸附。Fe_(R)对OC的保存受到沉积物粒度、Fe_(R)含量与形态以及TOC来源与组分的影响。TOC、Fe_(R)与Fe-OC主要分布在粒度较小的沉积物组分中。表层沉积物中铁的存在形式以Fe_(3+)为主,占总铁的87.42%,在高盐度沉积物中相对更高。Fe_(R)会选择性保存结合δ^(13)C值(稳定性碳同位素自然丰度)偏正的OC与芳香族OC。与茅尾海相比较,大风江入海口表层沉积物Fe-OC中类蛋白荧光组分占总荧光组分的比例更高。类蛋白荧光组分占比随Fe-OC∶Fe摩尔比升高而升高。本研究有助于明确广西红树林表层沉积物中Fe_(R)对OC的选择性保存机制,加深对陆海界面沉积物中OC的保存过程的了解。Iron oxides play a significant role in the global soil(sediment)organic carbon(OC)storage.Mangrove wetlands,receiving both terrestrial and marine inputs,provide a unique habitat for the preservation of organic carbon by reactive iron oxides(FeR).However,the impact ofFe_(R)in the surface sediments of mangroves on the preservation process of OC,as well as the selectivity ofFe_(R)towards different OC components,is still unclear.The surface sediments in the present work was collected in the natural mangrove areas around the estuaries of the Dafeng River and Maowei Sea in Guangxi,which are highly influenced by tides and rivers.The research was focused on the changes in the content and composition of iron-bound organic carbon(Fe-OC)in sediments.The results indicated that the average content of Fe-OC in surface sediments in the estuaries of Dafeng River and Maowei Sea was 0.16%±0.07%and 0.17%±0.07%,respectively.These values represented 16.2±5.04%and 10.9±5.63%of the total organic carbon(TOC)content in the respective sediments,which were primarily preserved through adsorption.Furthermore,the preservation of OC byFe_(R)was influenced by the sediment particle size,the content and form of FeR,and the source and composition of TOC.TOC,FeR and Fe-OC were mainly distributed in the smaller grain size sediment fractions.The predominant form of iron in surface sediments was Fe3+,accounting for 87.42%of the total iron,and was relatively higher in high salinity sediments.FeR selectively preserved OC with higherδ^(13)C(stable carbon isotope natural abundance)and aromatic OC.Compared with the Maowei Sea,the proportion of protein-like fluorescent components in Fe-OC of surface sediments from the Dafeng River estuary was higher and the proportion of protein-like fluorescent components increased as the molar ratio of Fe-OC∶Fe increased.This study helps to clarify the selective preservation mechanism of OC byFe_(R)in mangrove surface sediments in Guangxi,and deepen our understanding of the preservation process of OC in land-sea in

关 键 词：红树林 沉积物 铁结合有机碳 稳定性碳同位素 

分 类 号：P736.4[天文地球—海洋地质]