| The Three Gorges Project (TGP) on Changjiang (Yangtze), the largest hydropower-complex project ever built in the world, completed its Phase-II construction and Phase-I water storage in 2003. Its effects on environment and ecology also attracted many scientists` attentions. In this reason, two cruises were taken in Phase-I water storage (2003) and three years after the storage (2006), and surface sediments and core were collected at the Changjiang (Yangtze) Estuary and its surrounding coastal area. In this thesis, we have analysized grain size and total concentrations of heavy metals in surface sediments and core, compared the distribution of heavy metals in the surface sediments during two different periods, discussed the evaluation of heavy metals in the core Y16 which was located off the Changjiang (Yangtze) estuary, and investigated the response of heavy metals to human activities.Supported by the"National Basic Research Program of China for Land-Sea interaction and its effect on the environment in the typical estuaries and offshore areas of China"(Project No: 2002CB412400), the thesis discussed the key question of the Program: effects of pollution (including heavy metals) from Changjiang (Yangtze) on the costal environment. The main results in the thesis were drawn as follows:(1) From Phase-I water storage (2003) to 2006, the water discharge of Changjiang (Yangtze) reduced from 924.8 billion m3 to 688.6 billion m3. Along with water discharge, there is a gap between transportation intensity of diluted water from Changjiang in 2003 and 2006. Compared with 2003, the transportation intensity of diluted water reduced in Northeast and Southeast off Changjiang estuary in 2006 and enhanced in North. Obviously, the effect of Subei coastal current reduced in North area because of enhanced transportation intensity of diluted water in this direction.(2) Compared with 2003, the pattern of grain size distribution was not changed in 2006, but the concentration of clay was increased significantly. And there was a high value area in north off Changjiang estuary. The transportation intensity of fine-grain material has changed in the deriction of north, northeast and southeast. This change is similar with the transportation of diluted water.(3) During 2003, the distribution of heavy metals in the surface sediment is: The low concentration and band type distribution of heavy metals were observed and heavy metals were enriched in mud area. And two hotpots of heavy metal concentration were located in the turbidity maximum zone and west of plume front which caused by the mixing between diluted water and marine waters. There was a decreased trend of the heavy metals concentration in the east of the plume front. Terrigenous discharge, hydrographic dynamics, adsorption, flocculation and redox condition were main factor for the distribution of heavy metals.(4) Compared with the distribution of heavy metals in 2003, the pattern of heavy metal distribution was not changed in 2006. The heavy metal also enriched in mud area.But from Phase-I water storage in 2003 to three years after the storage in 2006, the concentration of heavy metals was decreased. It is difficult to determine the factor, whether it is caused by the Phase-I water storage of TGP or the effect of the environmental protection in Changjiang drainage. Obviously, the high concentration of heavy metals which presented in northeast of Yangtze estuary is correlated with the increasing concentration of clay. The gradient concentration of heavy metals was decreased in southeast of Changjiang estuary (east of Hangzhou bay) in 2006. It may reflect that ouside of Hangzhou bay is another important"sink"of heavy metal except Changjiang estuary. Above result may illustrate that along with the changing of water discharge, the amount of the fine-grain material changed, which was transported to northeast and southeast directions.(5) Compared with the results in 2003, the contribution of terrigenous input reduced for the total variance, and the contribution of the effect in human activity enhanced in the principle analysis of 2006. It may concern that the changing concentration of heavy metals is related to the reducing sediment dischanrge. Moreover the effect of human activity enhanced. It was difficult to determine the factor, whether it was caused by reduced sediment dischanrge or enhanced contamination or the two mixed. It may need more research work to improve this.(6) From 1986 to 2003, the sediment discharge of Changjiang was low, and the yearly average sediment discharge was about 7.60×108t. During this period, the decreasing of sediment discharge was significantly. The concentration of Cu and Ni were invariable in the core, and the concentration of Cr,Pb,Zn were increased. After normalized by Al , the trend of increasing concentration of Cr,Pb,Zn was increased, especially after the late 90s. This may be reflected the economy development in China, more pollution were discharged into the Yangtze estuary. In brief it may reflect enhanced effects of human activity.
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