Abstract
The karst development makes aquifer have strong anisotropy and heterogeneity. In order to reveal the characteristics of solute transport in the karst fissure–conduit aquifer system, this study presents a physical model of fissure–conduit in laboratory experiments to carry out the solute transport simulation. In this paper, the tracer tests of fissure–conduit combination, fissure, and conduit solute transport process in saturated flow are designed. We found that different aquifer structures and tracer injection points have an influence on the shape of the breakthrough curve. Besides, the two-dimensional dispersion model of tracer injection of the instantaneous point was used to calculate the dispersion parameters of each group of experiments. Then, the dynamic responses of the linear distance (x) between the injection point and the receiving point, initial time (t0), peak time (tm), peak concentration (cm), average tracer transport velocity (V), and porosity (p) of aqueous media to the longitudinal dispersion coefficient are discussed. In addition, according to the measured data, Gaussian multi-peak fitting can be used to reflect the overall shape and change trend of the multi-peak BTC. These results demonstrate the solute transport behaviors in the saturated karst aquifer system, which have important reference significance for solving the engineering environmental problems in the karst area.
Highlights
Diameter has little influence on the equivalent dispersion, while the length of pipe path, number difference, and pipe diameter difference has a great influence on the equivalent dispersion, and the number of pipes and pipe surface has a positive correlation with the equivalent dispersion
The values of each parameter are correlated with the longitudinal dispersion coefficient to discuss solute transport process in karst aquifers
The results demonstrate that the porosity has a better linear correlation with the DL under the condition of fissure–conduit water-filling
Summary
Diameter has little influence on the equivalent dispersion, while the length of pipe path, number difference, and pipe diameter difference has a great influence on the equivalent dispersion, and the number of pipes and pipe surface has a positive correlation with the equivalent dispersion. There are relatively few indoor simulation studies that consider rainfall recharge, epikarst zones, dolines, fissures, conduits, and springs based on the field with highly similar aquifer s tructure[13,14,15]. A similar physical simulation experiment is necessary to further study the solute transport in the complex karst aquifer medium. In response of these problems, we have verified a physical model considering the hydrological cycle process of the karst aquifer system by analyzing the conceptual model and establishing a similar physical m odel[14]. A quantitative tracing test is a powerful tool, which can determine the hydraulic connection between the two points and provide direct information on the trajectory of groundwater movement, as well as the BTC, from which the solute transport in karst aquifer can be o btained[20,21]
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