Source, Sink And Its Environmental Record Of Sediments In Yellow Sea And East China Sea

The behavior and late of trace elements and organic matter in the process of Land-Sea interection, is not noly the key for the material cycle (such as carbone cycle and mercury cycle), but also relate to human activities (such as Dam Construction, urbanization, land use, industrial pollution and air pollution). If combine the nature process, human activities and oceanic environmental conditions in a typical estuary or shelf, and assists the avilible proxy, it is possible to recognize source and sink of trace metals and organic matter in the oceanic process. Therefore, the Changjiang, the Yellow Sea and the East China Sea are one of the best places to study the source to sink of the sediment.This research is supported by the Natural Science Foundation of China (No.41076022) and the National Basic Research Program of China (No.2002CB412400). Four cruises were accupied on the Changjiang estuary, the Yellow Sea and the East China Sea during summer of2003and2006, winter of2009and autumn of2010. The concentration of suspended sediment, grain size, clay mineral content, total organic carbon, total nitrogen, heavy metals and rare earth elements were determined, and transportation of suspended sediments, source of sediments were analysised and discussed. Based on other research, sediment deposition in the Yellow sea and the East China Sea were also estimated, and a complete discussion was taken to the sediment source and environmental records. The major conclution were drawn below:(1) The concentration of suspended sediments range from0.1to300mg/L, and the suspended sediment concentration with less than5mg/L distributes in the most study area. The high concentration of suspended matter is in the shallow water along the northeastern coast of Jiangsu Province. The low is mostly in the south area of Shandong Peninsula and the mud area of the South Yellow Sea. The distribution of suspended sediments is controlled by the circulation system and the resuspcnded process. The mud of North Yellow Sea and the mud of Shandong Peninsula are the sink of sediment from the Bohai Straits. However, the Changjiang diluted water could carry parts of sediments to the mud of North Yellow Sea by the Yellow Sea Warm Current, and the sediment from old Yellow River is the major contribution for the mud of the middle part in the South Yellow Sea. The sediment accumulacation in the mud of the North Yellow Sea is about20Mt/yr, for the mud of the Shandong Peninsula is about25-75Mt/yr and the mud area of the South Yellow Sea is about49Mt/yr. Based on this, we could conclude that there are more than43Mt/yr sediment from the Bohai Strait and more than50Mt/yr sediment from old Yellow River are transported to the Fast China Sea.(2) The max concentration of suspened sediment in the Changjiang estuary at summer is presented in turbidity maximum zone. High value is in the near shore mud area, and low value is preseted in the relict sediment of the East China Sea. The distribution of suspended sediments is controlled by the coastal current, the Changjiang dillutied water and Taiwan Warm Current, especially the max gradient of suspened sediment concentration presented in the shear front off the Changjiang estuary. The concentration of surface suspended sediment is controlled by the Changjiang diluted water, and part of the suspended sediment could be transported to the northeast direction. The max concentration of bottom suspended sediment is about1000mg/L in the turbidity maximum zone and shows a dcreased trend to the sea. Most of the suspended sediments are transported to the south off the Changjiang estuary by the coast current. It is about186Mt/yr sediment deposited in the mud of Minzhe coast. I lowever, the sediment depositon in the area of the Changjiang offshore mud is less than in the mud of Minzhe coast, but there is a high accumulacation rate in the Changjiang offshore mud area and its sediment deposition flux is about137Mt/yr. Therefor, the sediment deposited in the Changjiang offshore area is about323Mt/yr, above than the deposition flux caculated from the shallow seismic profile (240Mt/yr).(3) The source of organic materr in the sediment of the North Yellow Sea mud area is mainly from terrigenous input. The near shore sediment of the mud area off the Changjiang estuary is controlled by the terrigenous input, and the ocean source effection is increasing to the sea. In the mud area of the South Yellow Sea, terrigenous input is still the main source for the organic matter, and in the east part, ocean source input is increased which may correlated to the Warm Current of Yellow Sea. During the hundand year time scale, there is about0.19Mt organic carbon depositions in the mud of North Yellow Sea every year. And0.59Mt organic carbon buried in mud of South Yellow Sea every year,1.24Mt/yr organic carbon in mud of the Changjiang estuary which is below the value of the Minzhe Coast mud area (2.10Mt/yr). The burry flux of organic carbon in the East China Sea is above the flux in the Yellow Sea. More than50%organic carbon is buried in the mud area off the Changjiang estuary.(4) High value of heavy metals in the Changjiang estuarine sediment is presented near the estuary, and shows a dreaseaing trend to the sea. Most of low vlues of heavy metals are presented in the relict sediment of the East China Sea. Fe-Mn oxide fraction is the major fraction for the sediment of Changjiang estuary. Non residual fraction of Cu correlated to the sediment flux of the Changjiang, and non residual fraction of Pb is affected by the atmospheric input. The concentration of Pb and Zn in the core Y16presents an increasing trend from1990s, which is mainly controlled by the Changjiang input, biogenic sedimentation, and human activities. Moreover, the sediment flux of Changjiang presents a negative correlation with the concentration of Pb and Zn. From1990. the concentration of Pb and Zn is affected by the anthropugenic pollution. But. such huge sediment flux from Changjiang significantly diluted the pollution in the sediment.(5) The distribution of clay mineral in the sediment of the Yellow Sea and the East China Sea is mainly controlled by the Changjiang and the Yellow River. The clay from the North Yellow Sea in mainly controlled by the Yellow River input, and the clay from the mud of Minzhe coast is affected by the Chanjiang. However, the clay mineral in the mud of South Yellow Sea is not only effects by the Old Yellow River, but also effects by the Changjiang and Yellow River input. However, the contribution of clay mineral from the Korea River is neglectable in the mud of South Yellow Sea.The REE concentrations of suspeneded sediment and surface sediment arc range from20to300μg/g. The REE distribution pattern normalized to North America Shale present two typies:one is that there is no distinguish of the REH distribution pattern in the different layers of suspended sediment. The other is thai REE distribution pattern in the bottom layers is same to the sediment of Yellow River. But, REE distribution pattern in the surface and10m layers are riched in HREE, and TREE is lower than others. The REE distribution pattern in the Yellow Sea is mainly controlled by the terrigenous input and others (such as surface suspended sediment) may affect by the REE in the water. It could be interperated that the suspeneded sediment adsorbs the HREE of the water.The innovation point of this paper is about:firstly, based on the mineralogy, geochemistry and sediment transports, we analysis the sediment transportation pattern and souce in the Yellow Sea and the East China Sea, recalculated the sediment flux, burry flux of organic matter and the environment effection of heavy metals. Secondly, a detail work for the REE in the suspended sediment of Yellow Sea is carried out. Parts of REE distribution pattern in the surface and10m Layers suspended sediment present nearly a line, but the HREE is related rich. The related rich HREE in the surface of suspended sediment is may attributed by the asorbtion of HREE from the water.