SEDIMENTARY GEOCHEMICAL RECORDS: INDICATIONS OF ENVIRONMENTAL CHANGES IN BOHAI BAY

Based on the analysis of ²¹⁰Pb radioactivity,grain size and element geochemical contents (Corg,As,Hg etc) of 2 cores collected from subtidal zone of the west coast of Bohai Bay in 2007,the results show that the deposition rate is divided into different subsections with different depths.The average deposition rate is 19.1 mm/a and 24.3 mm/a in QHYH 01 and QHYH 02 stations. Above the depth of 120 cm,sediments mainly came from Haihe River and then from Yellow River.Multiple geochemistry gyration of high content of Ca,low content of Cl,low content of Cl,high content of Ca occurred in the early geochemistry environment,and the corresponding trace elements of As and Hg were regular in QHYH 01 station.From 1950s,the contents of Hg and As have the rising trend in QHYH 02 station,but the rising content of Hg may be caused by the second pollution of re-suspension in QHYH01 station.