Sedimentary Records Of Heavy Metals In The Coastal Mud Area Of The East China Sea

Heavy metal pollution is one of the top scientific topics of LOICZ (Land-Ocean Interactions in the Coastal Zone) and marine environment study. Mud areas are the depositional centers for the modern continental shelf in the East China Sea (ECS), thus they are ideal areas to study the historical variation for the pollutants to the sea. Based on the study of vertical distribution of metals in a core from the coastal mud area of the ECS, this paper is in order to reveal human activity's effects on the coastal environment and to find geochemistry indicators to identify heavy metal pollutants from human activities.The Changjiang and Huanghe Rivers are main sediment sources for the ECS, which are important in the LOICZ study. Geochemical characteristics of the suspended particles in downstream of the Huanghe and the Changjiang Rivers show that the contents of elements such as Fe, Pb, Cu, Zn, V and Ni corresponds to the control rules of grain-size of sediments. Their contents increase with the decreasing of sediment's grain-size. The contents of Pb and Zn are higher in summer compared to those in winter, indicating that the Chiangjiang River's pollution in summer is more serious than that in winner. The suspended particles in downstream of the Huanghe River are characterized by high contents of Ca and Na, and the contents of other metals are lower than those in the Changjiang River. Ratios of Ca/Mg, Mn/Cu, K/Na, K/Ca, Al/Na are of great difference between the Changjiang and Huanghe Rivers, meaning that they can be used as indictors to identify the sediment source of these two rivers.S6 core is located in the south of the coastal mud area in the ECS. It consists mainly of silt and clay with poor sorting from the top to 182cm, indicating that the source and sedimentary environment are stable and continuous. Ratios of Mn/Fe, Mn/Cu, Cr/Ti and Cu/Ni support that the sediments from core S6 are mainly from the Changjiang River. The average rate of sediment accumulation is 0.98cm/a accordingto 210Pb data. Its age is about 101a at depth of 100cm. Before this time, there are few industries, so pollutants from the Changjiang to the ECS are very low. Thus, generally the mean contents of polluted metals from 100cm to 182cm can be regarded as background values. The background content of various heavy metals are as follows: Cr 95.14ug/g, Ni 46.87ug/g, Pb 31.76 ug/g, As 13.21 ug/g, Cu 33.73ug/g, Zn 115.11 ug/g.From 3 cm to 23cm(corresponding to 1990-1980), contents of major, trace elements of core S6 increase rapidly. From surface to 3cm, concentration of Pb decreases quickly, indicating that the content of Pb has reduced due to the strict restriction of lead-gasoline use in 2000. Pb can be used as an effective geochemistry indicator to identify the human emission to the coastal mud of the ECS. The coastal environment in the ECS has been polluted seriously since Chinese reform and open to the world. The historical variation of heavy metal pollution in the coastal mud of ECS has a good response to the development of Chinese industry and agriculture.