Exercise 19 Solution

Chloride is more conservative. Neither plot is a perfect bell curve in time, which indicates mixing of tagged groundwater with other water along the path. The normalized chloride graph is more symmetric and closer to a bell-shaped curve. It is likely that background chloride is present, which is why the chloride graphs from both springs never show zero values. The dye doesn’t have a symmetric normalized curve and has what is called a long tail before returning to zero. This indicates the dye is being delayed in the system, perhaps because it is temporarily sorbed to the surface of aquifer minerals or stored in dead-end pores, then released with passing groundwater and thus concentration declines slower than the rise in concentration. Neither the dye nor the salt is perfectly conservative, but the normalized chloride curve is always greater than zero because some dissolved solids including chloride were in the system before salt is added, whereas the normalized dye curves have a starting value of zero. The normalized chloride curves at both springs are more symmetric than the normalized dye curves, which indicates the chloride is a more conservative tracer (that is, it is not getting sorbed onto aquifer minerals or being delayed by other processes).

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Introduction to Karst Aquifers Copyright © 2022 by Eve L. Kuniansky, Charles J. Taylor, and Frederick Paillet. All Rights Reserved.