溶质（或污染物）在非饱和-饱和带中迁移转化规律是水环境保护与污染治理的重要理论基础。溶质随降水入渗进入非饱和-饱和带，经地下径流排入河流。河流中溶质浓度的波动往往是对地下径流系统的动态响应。由于地下介质的复杂性，我们对溶质迁移过程的认识仍十分有限。近来研究发现，河流中溶质的波动存在时间分形性，隐含着溶质来源及迁移路径的重要信息。因此，研究溶质波动的分形特征及机理有助于理解复杂的溶质迁移过程。本项目采用非平稳谱和概率配点等随机方法，求解描述溶质在非饱和-饱和带迁移过程的随机微分方程，研究输入源、水流和介质非均质性对溶质波动分形性的影响，分析分形特征及机理；选取典型流域，进行野外观测，建立流域溶质运移模型，验证理论分析的结论。通过理论研究、实测数据分析与流域模拟，揭示溶质分形波动的机理及物理意义。研究成果对深刻理解流域地下径流特征、反求溶质来源、预测溶质波动具有重要的理论与现实意义。

The mechanism of solutes (contaminants) transport in unsaturated-saturated zones is an important theoretical basis for water quality protection and pollution management. Our knowledge of the mechanism and process of solute transport in an unsaturated-saturated system is limited due to its complexity. The Solute access into unsaturated-saturated zone by rainfall carrying or driving and travel through the saturated zone to the stream. The fluctuations of solute concentration in streams are dynamic responses of the unsaturated-saturated system. Recently, many researchers found that the solute concentration in steams fluctuates as temporal fractal processes, and thus contains significant amount of information about the sources and transport path of solutes in the catchment. Therefore, it is necessary to investigate the mechanisms and characteristics of temporal fractal of solute fluctuations in order to understand the complex solute transport processes in the unsaturated-saturated zone. In this study we will to solve the stochastic differential equation description solute transport in the hillslope use the non-stationary spectral and probabilistic collocation methods to investigate the effects of solute sources, water flow, and heterogeneity of hydraulic conductivity on temporal fractal of the solute concentrations, and analyze the mechanisms and characteristics of temporal fractal. In order to verify the results of theoretical analysis, we will also conduct the analysis of the observation data and numerical simulations of solute transport modeling in a realistic catchment. It is expected to reveal mechanisms and the physical meaning behind the temporal fractal of solute fluctuations, and to improve our understanding of the characteristic of solutes transport in the subsurface flow of catchments, identifying sources of solutes, and predicting of solute fluctuations with the study proposed in this project.