Geochemistry of Fe, Mn, Ca, Mg in Sediments from Hangzhou Estuary and it's Adjacent Shore

As the study of the open estuary, Fe, Mn, Ca, Mg elements concentration, source and geochemistry characteristics in sediments are discussed in detail. The results are as follows: 1) Fe, Mn, Mg in sediments of Hangzhou estuary are higher and Ca is lower than that in sediments of the Prydz estuary and Antractics, the average value of Fe, Mn, Mg and Ca are 3. 76%, 0. 074%, 1.73%and 3.08% respectively.It shows that the characteristics of high Ca and Mg in sediments of the studying area. 2) The horizontal distribution of Fe, Mn and Ca, Mg in sediments are both the same and different.The distribution law of Fe, Mn, Ca and Mg are as follows: Fe, Mn increase from estuary tothe centre of estuary and decrease from Nanwei mouth to the centre of the estuary, the distribution of Fe, Mn tongue into centre of estuary; There are also two tongues of Ca with 30°30 'north latitude as boundary line; The distribution of Mg is more complex than that Fe, Mn, Ca, there are three thongues from Qiantangjiang runoff, Shoushan island and the dilute water of Yongjiang to the centre of the area respectively. 3) Fe, Mn, Mg in sediments exist in fine sediments, and Fe, Mn came mainly from movement of the dilute water of Yongjiang and Qiantangjiang runoff and controlled by clay; Mg came mainly from the absorption of clay to Mg²⁺in sea water and effected by the salinity of overlying water; Ca of south area came mainly from Qiantangjiang runoff and the weathering of rock in the coastal area and probably came mainly from biological shells and deposition of inorganic chemistry in north area. 4) The relation of elements in north area are stronger obviously than that in south, especially, except for correlation between Fe and Mn, Mg, there are no correlation in the south.It shows that the sources and exist forms of elements in south sediments are more complex than that in the north. 5) The study of the correlation between ratio of elements (Mg / Ca) in sediments shows that Mg / Ca in sediments increases from the mouth to the near shore and there is positive correlation between the organic carbon in sediments and Mg / Ca, it is found that there are bitter spar on manily section, it shows that the reaction of original calcium cabonate in sediments with Mg²⁺in seawater was processed