基于相空间重构理论的天津市近海水质混沌特性研究

Study on chaotic characteristics of Tianjin coastal water quality by phase space reconstruction theory

针对我国近海水质污染呈现的复杂非线性特征,通过对混沌理论中的相空间重构方法进行研究,提出了一种新的完全基于环境监测数据的近海水质分析方法。以天津市近岸海域为例,首先,根据相空间重构理论,对近海各监测点的1维COD时间序列进行多维相空间重构,求得最佳嵌入维数mmin和吸引子关联维数D;然后,采用Wolf方法计算最佳嵌入维数mmin下重构相空间的最大Lyapunov指数λ1。计算结果显示各个监测点的关联维数D均在3.3左右,最大Lyapunov指数λ1均大于0,表明近海水质COD时间序列具有明显的混沌特征,近海水质系统是一个多维系统,貌似随机无规律的近海水质系统具有内在的、固有的规律。应用表明,该方法实用性强,为进一步采用混沌理论对近海水质进行预测提供了理论依据,非常有利于近海水环境的管理。

Against the nonlinear pollution characteristics of Chinese coast ,a new method for analyzing the characteristics of coastal water pollution was proposed based on the chaos theory. Taking the Tianjin coast as an example, firstly, the phase space reconstruction method was used to reconstruct the multi-dimension phase space for COD time series of each monitoring point. And the best embedded space dimension mmin and attraetor＇s association dimension D were computed. Secondly ,the Wolf method was used to compute the biggest Lyapunov exponent minin. The results showed that all the association dimensions λ1 were around 3.3, and the biggest Lyapunov exponents λ1 〉0. It proved that the coastal water quality pollution presented the chaotic characteristics. The coastal water quality system is a multi-dimension system,and has inherent orderliness. The conclusion summarized in this paper could provide the theory basis for the coastal water quality forecasting which based on the chaos theory. It can be found from the application that the method proposed in this paper is practical and suitable for the environmental management in the coastal water.