摘要
在野外现场调查的基础上,对三亚湾近海沉积物及海滩沉积物进行粒度、有机质、铁形态等地球化学分析及扫描电镜显微观察,结果显示,三亚湾近海表层沉积物以粉砂质为主且由岸向海粒径变细,砂含量减少,粉砂和黏土含量增多,指示湾内水动力较弱,近岸水动力有所增强。三亚湾海滩黑化的有机污染物来源主要有雨污水外溢、三亚河沉积物中的“腐泥”以及三亚湾历史排污口底泥再悬浮和再沉积等。三亚湾海滩缺少细粒沉积物,黏土矿物不是造成有机质富集的主要原因。扫描电镜及能谱分析显示海滩致黑矿物主要为铁氧化物,铁形态分析结果表明氧化铁、游离铁络合度皆与有机碳含量呈明显正相关关系。在弱碱性的氧化环境中,铁氧化物通过配体交换形成的络合作用吸附有机质,金属离子通过阳离子架桥作用促进铁氧化物对有机质的吸附。因此,铁氧化物-有机质-重金属元素三者相互作用可能是导致污染有机质胶结及三亚湾海滩黑化现象的发生的主要作用机制。
Recently,Sanya Bay,Hainan Island,South China,suffered from beach blackening,which has become an environmental issue affecting local tourism and ecological health.After the field investigation,we conducted a geochemical analysis on grain size,organic matter content,and different iron forms of offshore and beach sedi-ments in Sanya Bay.Results show that the surface sediments are mainly silty.The grain sizes become finer with less sandy and more silty and clayey contents from nearshore to offshore.This distribution pattern indicates that the hydrodynamic force in the bay is weak and it is enhanced in the nearshore.The main sources of organic mat-ter of beach blackening in surface sediments of the Sanya Bay are the overflow of rainwater and sewage,the"sap-ropel"from the sediments of Sanya River,and the resuspension and redeposition of sediment loaded from the pre-viously discharge of organic pollutants.Clay minerals are not the main reason for the enrichment of organic mat-ter.SEM-EDS analysis shows that the main blackening minerals are iron oxides.Iron morphology analysis show that the complexities of iron oxides and free iron are positively correlated with organic carbon content.In the weakly alkaline oxidation environment,iron oxides adsorb organic matter via complexation by ligand exchange,and metal ions promote the adsorption of organic matter by cation bridging.Therefore,the interaction of iron ox-ides,organic matter,and heavy metals shall be responsible for the cementation of polluted organic matter and formation of the beach blackening in Sanya Bay.
作者
高琛
胡梦茜
吴自军
GAO Chen;HU Mengxi;WU Zijun(State Key Laboratory of Marine Geology,Tongji University,Shanghai 200092,China;Guangzhou Marine Geological Survey,China Geology Survey,Guangzhou 510760,China)
出处
《海洋地质前沿》
CSCD
北大核心
2022年第8期28-36,共9页
Marine Geology Frontiers
基金
中国地质调查局项目(DD20190308)
国家自然科学基金(41976057)。
关键词
三亚湾
海滩黑化
有机质
铁氧化物
吸附作用
Sanya Bay
beach blackening
organic matter
iron oxide
adsorption
