(1) Owing to luxuriant aquatic plant growth, some elements such as C, N and Ca are enriched in the surface sediment. The concentrations of nutrient elements reduce in the process of cultivation.

(2) Because of the high and frequent removal of the groundwater level in cultivation area, many elements such as Ca, Mg, Fe and Mn are removed. The loss of Ca is nearly 80%.

(3) In the evolution of the lake, Changes in cultivation and in dry and wet processes of the lake have altered the sedimentation processes, the order of sediment layers and the distribution of elements.