Study On Geochemical Characteristics Of Surface Sediments From The Bohai Bay

The paper comes from the geological survey project "The technological research of the regional geochemical survey". According the geochemical analysis of100samples of surface sediments, combing with precedent achievements related, thepaper covers the geochemical characteristics of the surface sediments from the Bohai Bay, summarizes the change laws of the main elements and trace elements, expounds the distribution pattern of the elements, the trace sense of REE, interrelated relationship and combination. In addition, the current situation is found out by evaluation of the heavy metal in the marine sediment. The extensive study of the geochemical characteristics of the surface sediments from the Bohai Bay tells some results below:(1) From the near to the distance sea, the main elements show different varying tendency of their contents:SiO2, Al2O3decreases, MgO、CaO increases, TFe2O3, Na2O, K2O almost unchanged. Most of the trace elements don’t change apparently, The contents of Zr、Hf、Hg、Pb, which deeply suffer from the terrigenous fragments, decrease. As, Br, Cl, Cd, Co, Cr, Cs, Cu, Ga, Mn, Mo, Ni, Sb, Sn, Zn, V, W, which have been affected from oil and gas accumulation, slightly incease.In the affection of the elements’characteristical and source of infalling material, some typiacal distribution patterns are found: the patterns of Al, Fe, K are similar and Ca, Na are opponent. The high value area of Rb, Co, Ga, Cs, Ni, V locate similiarly in the northeastern. The high value area of Hf, I, Zr, Sr locate in the northwestern, the high value area Mn, Mo, Sb locate similiarly in southwestern.(2)According to the results of the factor analysis and cluster analysis, all the elements can be divided in to four groups:As, Sb, Mn, Mo, Pb, I, Cl, Br; Sr, CaO, TC; Zr, Hf; Co, Ni, Cs, Cu, Ga, Cr, V, Rb, Zn. Every group has certain indicator meaning. Source of infalling material control the distribution of most elements.(3) The quality of the sediments in the Bohai Bay is measured by three indicators:the quality standards for marine sediments, index of geoaccumulation, the Potential Ecological Risk Index. Results show that the contents of the heavy metal elements-As, Hg, Pb, Cu, Zn, Cd, Cr are in the grade of safety, the sediments are clean and the ecological risk is slight, although Pb, Cd, Hg should attract more attention.