GEOCHEMICAL RECORDS OF ENVIRONMENTAL CHANGES IN THE GAOYOU LAKE AND THEIR RESPONSE TO HUMAN ACTIVITIES

Based on the parameters of the core sediments taken from the Gaoyou Lake, such as grain-size, sedimention rate and contents of geochemical elements, environmental changes during the modern period and their response to human activities and regional events were studied with reference to historical records. It is concluded that the contents of heavy metals increased with the decrease in water depth of the lake in the recent 300 years. The great regional events, such as the northward shift of the Yellow River contributed greatly to the changes in the contents of heavy metal elements. The human factors, which lead to the abnormal fluctuation of the contents of heavy metal elements, include the construction of Gaojia Levee along the Grand Canal for the purpose of shipping, and the significant increase in population owing to the changes of the tax system in the Qin Dynasty. However, the increase in the heavy metals in the recent century is mainly due to the increase in population and the intensification of human activities.