Preliminary Study On The Characters Of Elemental Geochemistry And High Resolution Sedimentary Record In The Process Of Land-sea Interaction In The East China

Yangtze River and Yellow River transport numerous materials, including a lot ofpollutant, to the marginal seas of China, and the dust storm of the East China is animportant passage, delivering the materials to the Pacific. The mud areas in theSouthwest of the Cheju Island, the South Yellow Sea, the Bohai Sea, and along theFujian-Zhejiang Coast are the sedimentary center of the fine matter.Firstly, the mechanism of the colloidal flocculation is described and introduced todiscuss the formation of fine mud areas in ocean in my dissertation. The mud areas inthe marginal seas of China are all formed in the upwelling areas where the conditionof the physical chemistry (temperature and salinity and so on) changes regularly,which leads to the flocculation and sink of the colloidal solid.Major elements of 118 surface sediment samples in the Bohai Sea and the West ofthe North Yellow Sea and 57 sediment samples of sediment core B18 in the BohaiBay were analyzed by the ICP-AES, minor elements, including REE, of all sedimentsamples above were determined by the ICP-MS, and the compositions ofthe grainsize of all samples were analyzed by the Laser particle size analyzer. Three sedimentcores of B178, B18, and A435 from East to west in the Bohal Bay were dated by themethod of ²¹⁰pb.The distributions of the toxic elements showed that clear anthropogenic inputs oftoxic elements mainly from the rivers to the Bohai Sea, and the Dalian industrialregion was the important source of the toxic-elements in the West of the North YellowSea. The results indicated the potential pathways of trace metals via the transport ofsediment from the coast to the Bohai Sea and the West of the North Yellow Sea. The high concentrations of toxic elements near the Yellow River Delta were caused by theprocesses of adsorption and coagulation of dissolved trace metals with particulates aswell as aggregation of particulates between freshwater and marine water zones. Theresults of EFs and the correlation with the Fe indicated that As and Sb may be derivedmore from the anthropogenic sources, and Ers of As and Cd indicated that they maylead to heavier ecological risks in the studied region. The results of PCA indicated themost of the elements analyzed may be derived from the natural sources, and the BohaiBay may be the heaviest polluted areas among the four parts of the Bohai Sea. Theremay be considerable ecological risk in the most of the Bohai Bay, the Yellow Rivermouth and the southwest of the Liaodong Bay. In the West of the North Yellow Sea,the pollution of toxic elements, especially As, near Dalian may be much heavier, andthe sea area near Dalian may be in moderate or considerable ecological risk,influenced by the Dalian Industrial area region.The distributions of the major elements in the Bohai Sea and the West of the NorthYellow Sea, the compositions of the major elements of the sediment core B18(0-40cm), and the ²¹⁰pb dating results of three sediment cores were used to study thetransport process of the Yellow River material into the sea. The results indicated thatCaO/TiO₂ and CaO/Al₂O₃ were the effective indicators of the diffusing range of theYellow River materials in to the sea, and CaO/TiO₂=6 and CaO/Al₂O₃=0.3 were theboundary values of the diffusing range of the Yellow River material in to the sea.There were two centers of the fine sediments near the Yellow River delta, influencedby the flocculation process. The sediments near the Yellow River mouth wereresuspended, and transported to the Bohai Bay by the tidal current. Impacted by thewind in winter, the sediments near the Yellow River delta were transported to the east,and the fine materials could enter the South Yellow Sea through the tip of theShandong Peninsula. The Yellow River's contribution to the center of the NorthYellow Sea may be small, indicated by the CaO/TiO₂ and CaO/Al₂O₃. The ²¹⁰Pbdating results of three sediment cores indicated that the materials from the YellowRiver were transported more to North-Northeast and the west along the south coast ofthe Bohai Bay than it to the Northwest. B18 was a mixture of the Yellow River and Luan River materials. Since 1976, the grain size composition, CaO/TiO₂ and CIA ofB18 had changed remarkably, indicating that the Yellow River materials transportedinto the Bohai Bay had decreased distinctly since 1976, which was caused by theman-made changing of the Yellow River channel, the decreasing of the Yellow Riversediments into the sea, and the changing of the salinity field and the circulationstructure in the Bohai Sea.∑REE,∑HREE and∑LREE were positive relation with the clay content (%) of thesurface sediments of the Bohai Sea and the West of the North Yellow Sea. In the westof the Liaodong Peninsula near the Changxing Island, Liaodong shallow bank, theBohai Strait, the Luan River mouth, and the Northeast area near the Yantai,∑LREE/∑HREE, La/Yb and La/Sm, were higher than them of other regions, andEu/Eu^* was higher than 1, indicating that the sediments in these regions may be partlyderived from the Archean rock on the land. Ce/Ce^* was higher than 1 in the South ofDalian, around Caofeidian, near Yantai, and the center mud of the North Yellow Sea,indicating that the oxidized condition was relatively stronger in these regions.All the analyzed elements in the aerosols of Qingdao displayed strong seasonalvariations: the concentration of Fe, Ti, Mn, V, Ni, Cu, Pb, Zn, Cd was the lowest inthe summer, and the highest in the winter. As an exception, the concentration of S insummer is higher than those in spring and autumn. During the dust episode, theconcentration of Fe, Ti, Mn, V, Ni, Cu increased remarkably, while the concentrationsof Pb, Zn, Cd, S were obviously lower than that in winter though they also increasedremarkably. Ti, Mn are mainly derived from the soil source. V in the atmosphere ismainly derived from the soil source, with minor contribution from ship emission. Theanthropogenic source has a relatively higher contribution to Ni and Cu in the non-dustsamples, while Cu is mainly from soil source during the dust episode. The S, Pb, Znand Cd are mainly derived from the anthropogenic source, even during the dustepisodes. The natural sources contributed about 60% to the sum of measured elementsand anthropogenic sources contributed about 30%.The rapid economic development in the Yangtze River Delta (YRD), China in thelast three decades has had a significant impact on the environment of the East China Sea (ECS). Lead isotopic compositions of a ²¹⁰pb dated sediment core collected fromthe coastal ECS adjacent to the Yangtze River Estuary were analyzed to track the Pbpollution in the region. The baseline Pb concentration in the coastal ECS adjacent tothe YRE was 32μg g^-1, with the corresponding ²⁰⁶pb/²⁰⁷pb of 1.195. The Pbconcentrations (average, 31^-2 mg g^-1) and fluxes (average, 30^-2 mg cm^-2 yr^-1) wererelatively constant from w1860 to mid-1980s, and they increased rapidly from themid-1980s to 1999, peaking in 1999 at 65 mg g^-1 for the concentration and 61 mgcm^-2 yr^-1 for the flux before decreasing sharply to 36 mg g^-1 and 31 mg cm^-2 yr^-1,respectively, in 2002. ²⁰⁶pb/²⁰⁷pb was constant from w1860 to mid-1960s (average,1.195), and decreased from the mid-1960s to 1.165 in 2000 before rising to 1.185 in2002. The variations of Pb flux and stable Pb isotopic composition in the study areareflected the impacts of the economic development, in particular the leaded gasolineusage in China. The severe flood of the Yangtze River could contribute moreanthropogenic Pb to the coastal ECS. Due to the different time of economicdevelopment, especially about 20 years lag of the phasing-out of leaded gasoline inChina, the historical records of Pb in the environment of China were obviouslydifferent from those of most European countries and the United States.