Karst and Cave RSS news feed Like us on Facebook! follow us on Twitter!
What is Karstbase?

Search KARSTBASE:

keyword
author

Browse Speleogenesis Issues:

KarstBase a bibliography database in karst and cave science.

Speleogenesis issues:

Republished from Proc. 8th Conference on Limestone Hydrogeology, Neuchâtel (Switzerland) 21-23 sep. 2006, p. 253-258, Presses universitaires de Franche-Comté, Besançon, France

UIS KHS Commission
Comparative tracing experiments to investigate epikarst structural and compositional heterogeneity
Abstract:

Comparative tracer testing may be used to evaluate the vulnerability of groundwater to specific contaminants by comparing reactive tracer response to that of a simultaneously injected non-reactive “conservative” substance. Conversely, knowledge of tracer reaction with specific materials permits information about subsurface heterogeneity to be inferred. A series of tests completed in the vadose zone overlying a limestone aquifer employed a cocktail of particles along with reactive and
non-reactive solute tracers to investigate transport rates between the ground surface and monitoring points approximately 10 m below ground. Short pulse tests revealed both solutes and particulate contaminants could travel at rates of over 10 m/h. Comparison of particle (microorganisms) and non-reactive solute tracer breakthrough revealed that particle tracers experience pore exclusion resulting in higher peak relative concentrations which arrive earlier than those of the solute. Prolonged tracer injection during subsequent experiments confirmed the response observed and illustrated that over 40 % of flow paths between
injection and monitoring points were inaccessible to particles, but could allow solutes to pass through them. Similarly, the difference in response between various reactive tracers demonstrated tracers reached monitoring points via multiple flow paths and suggests geochemical heterogeneity plays an important role in influencing tracer behaviour. The results of this investigation highlight the complexity of water flow through the epikarst and the vulnerability of groundwater in karst aquifers to contamination when soil cover is thin to absent.