基于ARIMA模型的洞庭湖第四纪沉积物中镉演化及意义

在对洞庭湖区沉积物钻探取样的年代学和地球化学研究基础上,分别建立第四纪和全新世时期Cd和Cd/Ca的时间序列演化ARIMA模型,并据模型的拟合值及未来预测值对区域地球化学环境中Cd的演化规律进行了探讨,结果显示区内Cd的演化有较显著的周期性——环境地球化学旋回,与气候多次冷暖的交替有关;沉积物Cd/Ca受气候环境等控制,分析该比值的变化规律可推测区域环境地球化学的演变历史;Cd和Cd/Ca两者的变化基本同步,说明该区Cd的演化主要为自然演化;未来30年内沉积层的Cd含量仍有逐渐增高的趋势,之后转为降低。从本区环境地球化学指标的时间变化规律及其与全球环境变化的相关联中说明自然条件是区域镉等元素沉积的主控因素。

The evolution of Cd in sediment of Dongting lake area and its significance based on ARIMA model

Based on the study of chronology and geochemistry of Cd in sediments of the Dongting lake area,we have established an ARIMA model of Cd and Cd/Ca in Quaternary and Holocene period respectively,and discussed Cd evolutionary regularity according to the fitted value and predicted value of the model.The results revealed that the Cd evolution has remarkable periodicity of ecogeochemistry cycles,and is correlated with the climate change of alternative cold and warm.Cd/Ca is changed with climate,from which the evolutionary history of regional ecogeochemistry can be inferred.The changes of Cd and Cd/Ca are basically simultaneous,which showed that the change of Cd is mainly a natural evolution.Cd in sediments will rise in the next 30 years and then tend to decrease.From the regularity of ecogeochemistry indexes and global environment variation,it is concluded that the natural environment is the dominant factor affecting the Cd deposition.