The Distribution And Source Analysis Of Main Organics In Sediments From Laizhou Bay

Study of marine sedimentary organic matter is mainly focused on the composition, distribution, biological sources and diagenesis in the early stages of bio-geochemical conversion of organic matter in marine sediments. N-alkanes widespread in modern marine sediments and the relative abundance of different carbon number n-alkanes could reflect the source and thermal maturity of organic matter in sediments. The study of aromatic compounds is mainly focused on environmental pollution control, but rarely in the study of modern marine sediments. The major sources of aromatic compounds are forest fires, burning of coal and oil, vehicle exhaust and oil spills and so on.N-alkanes and polycyclic aromatic hydrocarbons in sediments are extracted by a specific pretreatment method and then obtain their spectrum by instrumental analysis. Analysis the spectrum and carry out calculation to determine their content and the distribution and origin. N-alkanes in sediments can easily change with the environmental conditions changing. So n-alkanes are widely used in organic geochemical studies to illustrate the impact of accumulation and transportation of organic matter on the environment. The polycyclic aromatic hydrocarbons mainly come from human pollution and the studies on the distribution of polycyclic aromatic hydrocarbons could strengthen its source pollution control.The n-alkanes and polycyclic aromatic hydrocarbons in sediments of Laizhou Bay are analyzed and the rivers into Laizhou Bay are investigated in this paper. The results are shown as follow:(1)There are high value areas in the eastern and southwestern sea waters, where there are rivers inputs such as Yellow River and Xiaoqinghe river and so on as well as the fishing operations in the Bohai Sea. The n-alkanes in surface sediments of the Laizhou Bay are mainly from three kinds of sources which comprise the type of terrigenous input, the mixed type of terrigenous input sources and marine sources and type of oil pollution. Pairs of isoprenoid hydrocarbons pristane and phytane analysis, Pr/Ph (Pristine/Phytane) is from 0.62 to 1.43, indicating the oxidation-reduction depositional environment of the Laizhou Bay.(2)The concentration of polycyclic aromatic hydrocarbons (PAHs) in the surface sediments of Laizhou Bay showing that the distribution of the values is higher in eastern area than that in western area and the central area is low. Toward the shore from the estuary there is a decreasing trend followed by the distribution. There are Yellow River, Xiaoqinghe River and other rivers inputs, as well as the rotation of the tide in the central part of Laizhou Bay which affect the distribution of the polycyclic aromatic hydrocarbons. The source qualitative analysis of polycyclic aromatic hydrocarbons in surface sediments of Laizhou Bay show that the sources of polycyclic aromatic hydrocarbons indicate mixed characteristics including oil pollution, fossil fuels burning and combustion of firewood and coal. Meanwhile, the different ring combinations of polycyclic aromatic hydrocarbons also illustrate that the main source of polycyclic aromatic hydrocarbons in the Laizhou Bay is oil pollution.(3)The petroleum hydrocarbon concentrations of 11 terrestrial stations from Laizhou Bay exceedâ…¢water quality standard (1mg/L). The petroleum hydrocarbon concentrations of Yuhe River and the Mihe River are as high as 40.01mg/L and 39.82mg/L respectively. The COD concentrations of most stations meet I water quality standard (2mg/L). Wanghe River and Jiehe River are beyond II water quality standard (4mg/L) slightly and Zehe River are beyond III water quality standard (6mg/L). The petroleum hydrocarbons with high concentrations from the rivers into the sea-shore waters is one of the main sources for the polycyclic aromatic hydrocarbons and n-alkanes in Laizhou Bay, while the water and sediments in rivers are rich in organic matter which is a terrestrial input source for sea waters. The main rivers of petroleum hydrocarbons input are Yuhe River, Mihe River and Xiaoqinghe River.