The Research Of Element Geochemical Characteristcs And Hundred Years’ Element Record Of Human Activties In The Liaodong Bay Sediments

With the development of economy,the marine environmental pollution has become one of the most important research topics. A large number of human-produced pollutants are driven into the sea through a variety of ways,such as rivers, industrial vertical mouths, breeding and so on.These pollutants will influence the marine environment,and these information will be well documented in marine sediments. Therefore, the study of offshore sediment, especially element geochemistry, the instruction factors of sedimentary environment evolution has a great significance to the study of depositional environment of the study area and the sedimentary record of human activities.The element geochemistry, heavy metals and paleoproductivity of345surface samples and two typical cores S26, E15were studied. Combining with210Pb、137Cs dating system, a series of results and viewpoints with regard to chemical characteristics and elements record of hundred years’human activities in the Liaodong Bay area were presented.In Liaodong bay surface sediment, the abundance of most of the major and trace elements are close to that in the China offshore shallow sea, but lower than that in the Yangtze and yellow rivers. High value area of heavy metal elements about As Cd,Cu, Cr, Hg, Pb and Zn in Liaodong Bay surface sediments is mainly distributed at the area near Huludao, and showing a decreasing trend in near-shore to the off-shore; And part of the Liaodong Bay Stations surface sediments have been polluted by heavy metals in the study sites. Cleaning stations accounted for65.5%, accounted for13.04%of light pollution, and severe polluters accounted for21.45%. Most of the polluted stations locate at the area near Huludao.The control factors to elements contents in sediments are grain size, the influence of human activity, biological components and salt remnants.The particle size component in the core is silt, followed by clay, and sand is the lowest.Core S26and E15are about hundred years’deposition by radioisotope dating analysis, their deposition rate is roughly same,and core S26is0.583cm/a, while E15is0.523cm/a. Most of the major and trace elements in addition to individual elements such as Zn and Cu, showing no significant change in the vertical direction, and on the whole remains constant.Heavy metals, organic carbon and biogenic silica in two cores were measured. And a series of results were presented; Heavy metal elements Pb,Zn and As within the study area are relatively enriched. And heavy metals are showing a slightly lower after rising trend in vertical. Biogenic silica content is in the range between0.31%-0.81%, slightly higher than the average content of the southern part of Bohai Sea, South Yellow Sea and the Yangtze Delta region, but lower than other parts of the world. Biogenic silica are first increased and then decreased in vertical. And correlation with the particle size is very small. The organic carbon content is between0.31%-0.86%, slightly higher than the southern region of Bohai Sea, and comes from both the sea source and land-based sources.The correlation between organic carbon and total nitrogen is good, but small between organic carbon the particle size.The evolution of heavy metals and paleoproductivity shows a good agreement with the construction of major projects of the Liaodong Bay and China’s national economic development. Heavy metals and organic carbon, biogenic silica in vertical show corresponding fluctuations with the built of Liaodong Bay port, heavy industry factory, etc. And response to China’s national economy is divided into four stages:The first stage:from the1860s to the1920s. In this stage, the modern economy in China starts difficultly, the Chinese national industry is just emerging and the economic level is at a very low stage. The content heavy metals and organic carbon chang little during this time. While the biogenic silica content shows an upward trend.The second stage:from the1920s to the1970s. The heavy metals don’t change significantly, while the organic carbon, nitrogen and biogenic silica, has emerged as a fluctuating trend. Human life and production activities have been gradually enhanced since the beginning of the20th century. This period, China broke the feudal society which bounded the development of productive forces, introduced modern western science and technology, freed productivity initially, especially since the1950s, large-scale socialist construction was started.The third stage:from the1970s to the1990s. Both heavy metals and organic carbon have an increasing trend, and C/N ratio, an enrichment factor is increased. This period is the Cultural Revolution and the early stages of reform and opening, and the rapid development of productive.The fourth stage:the1990s to present. Most of the content of heavy metals and paleoproductivity indicators shows a downward trend during this period,And the economic develops fast and environmental protection is rapily strengthened in this period.