Laboratory and temporal moment analysis of tracer-based solute transport in karst conduits

Abstract

Tracer test is an effective tool for characterizing the complex conduits and exploring the solute transport law for karst aquifers. In this study, three generalized karst conduit models were established, including auxiliary side conduit, cave, and waterfall. A series of tracer tests were conducted to obtain tracer residence time distribution curves. These tracer curves were used for performing temporal moment analysis to estimate fluid flow characteristics and solute transport process of karst conduit models. The results demonstrate that the residence time distribution curves are mainly constrained to the length and path differences of auxiliary side conduits, the lengths and geometries of pools, and the lengths and numbers of waterfalls. Although the multi-peaked residence time distribution curve is the basis for judging the existence of multiple karst conduits with path differences, the number of paths cannot be determined directly. Moreover, it can be presumed that there are some caves or waterfalls when the residence time distribution curve has a long tail. This study provided some useful references for the development of solute transport theory in karst conduits.

Keywords

karst conduits / tracer tests / solute transport / temporal moment analysis

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