渤海湾表层沉积物元素地球化学分布特征与影响因素

对取自渤海湾的307个表层沉积物进行了元素测试和粒度分析。渤海湾表层沉积物的常微量元素呈现4种组合:富集于粗粒沉积区的SiO_2、Na_2O亲碎屑元素组合;富集于细粒沉积区的以Al_2O_3和重金属元素为代表的亲黏土元素组合;与缺氧环境有关的MnO、V、TOC元素组合和与河流输入有关的陆源CaO、TiO_2元素组合。粒度粗细主导了渤海湾元素含量分布的整体格局;海域河流物源供应不同较大影响了渤海湾南部(富Na_2O、CaO和SiO_2)和北部(富Ba和P_2O_5)在元素含量上的差异;高流速潮流对海底的冲刷再分配导致曹妃甸南侧Sr、Ca元素的条带状富集异常;有机质在细粒沉积区的富集导致缺氧环境的形成和K_2O、Mn、V、自生黄铁矿的海洋自生化学沉积;人类活动导致以Pb为代表的重金属污染在河流入海口、港口及沿岸海域的元素分布异常;曹妃甸沙坝内侧的泻湖(海洋钙质生物沉积)与沙坝外侧水下岸坡(陆源碎屑沉积)的截然不同的物源,导致了独特地貌沉积环境下元素分布的局部差异。

Geochemical distribution and its controlling factors of the surface sediments in the Bohai Bay

The geochemistry and particle size of 307 surface sediment samples collected from the Bohai Bay were analyzed. The surface sediments in the Bohai Bay show 4 element assemblages:philo-clastic element assemblage (SiO₂ and Na₂O) enriched in coarse-grained deposition area, philo-clay element assemblage (Al₂O₃ and most of the heavy metal elements) enriched in fine-grained deposition area, redox sensitive elements assemblage (MnO, V, and TOC) associated with anoxic environment and terrestrial element assemblage (CaO and TiO₂) related to river input. Particle size dominates the overall distribution pattern of the element contents in the sediment from the Bohai Bay; different river sources strongly affect the element content differences between the southern (rich in Na₂O, CaO and SiO₂) and the northern (rich in Ba and P₂O₅) parts of the Bohai Bay; the erosion and redistribution of fast flowing tidal currents to the sediments lead to a strip-like enrichment of Sr and Ca in south of Caofeidian; the enrichment of organic matter in fine-grained deposition area leads to the formation of anoxic environment and marine autogenous chemical deposition of K₂O, Mn, V and authigenic pyrite; human activities cause an abnormal enrichment of heavy metal elements (represented by Pb) in river estuaries, ports and coastal waters; the distinct sources between the lagoon (marine calcareous deposition) on the inner side of the Caofeidian sand bar and the underwater bank slope (terrigenous clastic deposition) on the outside of the Caofeidian sand bar, leads to local element differences under the unique geomorphic sedimentary environment.