陆架边缘海环境下金属元素与有机质富集关系探讨——以南黄海表层沉积物为例

Relationship Between Metallic Elements and Organic Matter Enrichment in Self-margin Seas: Example from surface sediments in the South Yellow Sea

陆架边缘海是"河口—陆架"体系重要的碳汇,黏土矿物作为主要载体将有机质与金属元素吸附于表面或层间,通常表现为粒度、有机质和金属元素含量之间高度正相关。本文通过分析南黄海中部沉积物粒度、总有机碳、主微量元素,探讨三者之间分布特征和相互关系,进一步开展金属元素、有机质与黏土矿物吸附模拟实验,结果表明,酸性条件(pH=4)下适量的金属离子(Zn2+、Ni2+、Pb2+)明显促进伊利石对腐殖酸(有机质主要组成部分)吸附,腐殖酸吸附量达到20.06 mg/g,其中金属离子加入使腐殖酸吸附量提高6.25%;同时碱性条件(pH=8)下金属离子也能够促进伊利石对腐殖酸吸附,腐殖酸吸附量达到15.7 mg/g,金属离子加入使腐殖酸吸附量提高38.9%。金属离子的阳离子键桥作用促进伊利石吸附腐殖酸,且酸性环境下腐殖酸的吸附量高于碱性环境。证实了陆架边缘海背下金属元素的参与对黏土矿物吸附腐殖酸具有明显促进作用,有利于在全球碳循环过程形成边缘海"碳库",同时海洋酸化可能造成海洋溶解有机质降低和重金属离子浓度升高,对陆架边缘海海洋生态系统平衡构成威胁。

Continental margin sediments are an important ocean carbon repository of the estuary-continental shelf.Clay minerals as carriers adsorb organic matter and metal elements on their surface or between layers. It is usually expressed as a highly positive correlation between grain size,organic matter and metallic element content. This study analyzed the distribution and interrelationship of sediment grain size,total organic carbon,and major and trace elements in the middle of the South Yellow Sea. The study was further conducted for adsorption simulation experiments on metallic elements,organic matter and clay minerals. The experiments indicated that the correct amount of Zn2+,Ni2+,Pb2+under acidic conditions(pH = 4)significantly promoted the adsorption of humic acid(the main component of organic matter)by illite. The humic acid adsorption reached 20.06 mg/g,within which the addition of metallic ions increased the adsorptive capacity of humic acid by 6.25%. The metals under alkaline conditions(pH = 8)also promoted the adsorption of humic acid by illite,and the adsorption of humic acid reached 15.7 mg/g. The addition of metallic ions increased the adsorption of humic acid by 38.9%. The cationic bond bridging of metallic ions promoted the adsorption of humic acid by illite,and the adsorption amount of humic acid in an acidic environment was higher than in an alkaline environment. It is confirmed that the participation of metallic elements has an obvious promoting effect on the adsorption of humic acid by illite at the edge of the shelf,and is conducive to the formation of a marginal sea“carbon pool”in the global carbon-cycle process. In addition,ocean acidification may reduce the amount of dissolved organic matter and increase heavy-metal ion concentration,which would pose a threat to the balance of the marine ecosystem in a shelf-margin sea.