Department of Geophysics, Yunnan University, Kunming, Yunnan 650091, P.R. China.
Ground Water. 2011 Jul-Aug;49(4):584-92. doi: 10.1111/j.1745-6584.2010.00777.x. Epub 2010 Dec 9.
Often the water flowing in a karst conduit is a combination of contaminated water entering at a sinkhole and cleaner water released from the limestone matrix. Transport processes in the conduit are controlled by advection, mixing (dilution and dispersion), and retention-release. In this article, a karst transport model considering advection, spatially varying dispersion, and dilution (from matrix seepage) is developed. Two approximate Green's functions are obtained using transformation of variables, respectively, for the initial-value problem and for the boundary-value problem. A numerical example illustrates that mixing associated with strong spatially varying conduit dispersion can cause strong skewness and long tailing in spring breakthrough curves. Comparison of the predicted breakthrough curve against that measured from a dye-tracing experiment between Ames Sink and Indian Spring, Northwest Florida, shows that the conduit dispersivity can be as large as 400 m. Such a large number is believed to imply strong solute interaction between the conduit and the matrix and/or multiple flow paths in a conduit network. It is concluded that Taylor dispersion is not dominant in transport in a karst conduit, and the complicated retention-release process between mobile- and immobile waters may be described by strong spatially varying conduit dispersion.
在喀斯特管道中流动的水通常是污染水从落水洞进入和石灰岩基质释放的清洁水的混合物。管道中的传输过程受对流、混合（稀释和弥散）以及滞留-释放控制。本文开发了一个考虑对流、空间变化弥散和稀释（基质渗流）的喀斯特传输模型。利用变量变换，分别得到了初值问题和边值问题的两个近似格林函数。数值实例表明，与强空间变化管道弥散相关的混合会导致泉水突破曲线的强烈偏态和长尾。将预测的突破曲线与佛罗里达州西北部阿梅斯落水洞和印第安泉之间示踪实验测量的突破曲线进行比较，表明管道弥散度可达 400 米。这样大的数值被认为意味着在管道和基质之间存在强烈的溶质相互作用，或者在管道网络中存在多个流动路径。结论是，泰勒弥散在喀斯特管道中的传输中并不占主导地位，而可动水和不可动水之间复杂的滞留-释放过程可以用强空间变化的管道弥散来描述。
