The Characteristics Of Chemical Component Composition Of The Mud Sediments In The East China Sea And Their Response To The Environmental Factors

Continental margin seas are active zones between continental and open ocean, which has both terrestrial and biogenic sources in the benthal sediments. The major components of marine sediment contain efficient information to understand the biological production and the material sources in a sea area. It is important to study their distribution for understanding the changes of coastal environment and primary productivity both temporally and spatially. Calcium carbonate, iron and manganese oxy-hydroxides, organic matter, biogenic silica and residual lithogenic detritus, i.e., the major components of surface sediment samples from the southern Yellow Sea were separated and measured with a sequential extraction method, which the extraction efficiency, precision and recovery were examined and discussed. The content of major components of surface sediments collected from in the East China Sea (ECS) in June 2007 are measured with this sequential extraction method to identify the material sources of each mud area. The major components in a sediment core collected from coastal mud off Zhejiang and Fujian Provinces (CMZF) in June 2003,were also determined, of which the analog variety, the relationship and the response to environmental factors were clarified.This sequential extraction method is effective to separate and determine the five major components in coastal sediment, which resulted fairly fine precision and recovery of 98.1～99.1%. The contents of calcium carbonate, organic matter are consistent with the inorganic and organic carbon contents determined with an element analyzer, and it is thus proved that the reliability of the sequential extraction method in determination of major components of coastal sediment. The content of CaCO3 in mud sediment area in ECS ranges from 6.75% to 14.25%, increases gradually from inshore to open sea and reaches highest value in the Southwestern Cheju Island Mud Area (SCIMA). The contents of opal and organic carbon are 0.33%～0.83% and 0.44%～0.67%, respectively, and the C/N ratio ranges from 6.42 to 10.11. The CaCO3 content had no distinct variety trend vertically with average 6.5% in sediment core S5, while the content of OC and BSi increased markedly after 1930s, especially since 1980s. The Cu content of EXC+CARB (exchangeable and carbonate) and ERO (easily reducible oxides) had ascended distinctly since 1980s, except for OSM (organic/sulfide matter).Conclusions were summarized as follow:1. The sources of each mud area in ECS are markedly different. The mud area near the Yangtz River estuary and CMZF are influenced in a large extent by the terrestrial material from the Yangtz River and the CaCO3 originates mostly terrestrially. The organic matter in mud area near the Yangtz River estuary is dominated of lithogenic source, while the biogenic source is preponderant in Cheju Island Mud Area (SCIMA).2. The CaCO3 in sediment core S5 in CMZF mostly originates terrestrial source and the content peaks in special periods might reflect the influences on depositing process aroused by extreme climate events in Yangtz River drainage area.3. As well as the early diagenesis, the increase of OC in sediment core might be due to the upgrowth of diatoms and other algae stimulated by the eutrophication in water system.4. The content of EXC-Cu and ERO-Cu in S5 core are successfully used to track the economic development and the influences by anthropic activity in coastal Zhejiang and Fujian Provinces. The change characteristics of EXC-Cu has responded to the flood event in Yangtz River drainage area.