岩溶地下河污染物运移模型对比研究

两区模型（TRM）和暂时存储模型（TSM）为两种常用的岩溶地下河（管道）污染物运移模型，为了更好表征岩溶地下河污染物运移过程，开展模型对比研究.采用两种模型拟合室内管道示踪实验穿透曲线，从概念模型框架、模型优缺点、参数校正过程和物理意义、参数敏感性等方面对比分析两种模型的异同.结果表明，OTIS软件提供TSM的数值解，而CXTFIT软件提供TRM的解析解，但两者均能通过下游不同位置的穿透曲线分段表征地下河不同阶段的污染物运移过程.两种模型的物理意义相近，均可近似描述岩溶地下河中溶质的暂时性存储现象，较好地拟合溶质运移曲线.采用TSM可校正得到暂时存储区的横截面积，但采用TRM只能获得非流动区所占的比例.两种模型中弥散系数和传质/交换系数的敏感度较低，并且弥散系数的变化对穿透曲线拖尾无显著影响.研究结果为岩溶地下河污染物运移模型的选取与应用提供了依据.

A comparative study on two contaminant transport models used in karst underground rivers

In order to better characterize contaminant transport process in karst underground rivers, a comparative study of two models, two-region nonequilibrium model (TRM) and transient storage model (TSM), was conducted to simulate tracer breakthrough curve (BTC) in the conduits, and their similarities and differences were analyzed from the aspects of conceptual model framework, calibration process, parameter physical meanings and parameter sensitivities. The advantages and disadvantages of these two models were also summarized. The results show that OTIS software provides the numerical solution of TSM, while CXTFIT software provides the analytical solution of TRM. OTIS and CXTFIT both allow discretizing the karst underground river into several reaches of homogeneous parameters with multiple observed points. The physical meanings of the two models are also similar, both of which can approximately describe the temporary storage of solute in karst underground rivers and fit the BTCs well. The cross-sectional area of the storage zone can be estimated by using TSM, while only the ratio of the immobile zone to the whole water zone can be obtained using TRM. In the two models, the sensitivity of dispersion coefficient and mass transfer/exchange coefficient is low, and the variation of dispersion coefficient has few influence on the tailing of BTC. The results provide a good basis for the selection and application of solute transport models in karst underground rivers.