EROSION POTENTIAL AND SOLUTE TRANSPORT BY CAPILLARY SOLITONS WITHIN THE EPIKARST

Within the epikarst, hydrogeochemical evolution is inherently entwined with the characteristics of fluid movement. Even though large flux events through the crack system can be expected during precipitation events, during the majority of time the system is likely to seep moisture downward through the porous and fracture system. In connected crack networks, surface films are capable of transporting high volumes of liquid, while hugging the matrix wall and sustaining a gas-liquid interface. Chemical erosion potential of these thin films is associated with diffusion limited processes. The shape, thickness and meandering quality of these films are affected by matrix chemistry, surface texture, crack inclination and geometry. Here we present a newly uncovered fluid mode, non-dissipating capillary droplets, that may play a significant role in the chemical erosion of the matrix walls. While these droplets do not appear to change the fluid transport rate, they are capable of significantly increasing the solute transfer from the rock matrix, thereby accelerating the geochemical evolution of the karst matrix wall.

Under specific circumstances, liquid films can become unstable, leading to the development of a wavy gas-liquid interfacial surface with waves that grow in time. These waves can grow to amplitudes more than 10 times that of the original film. When these waves touch the opposite crack wall, the fluid situation and geochemical erosion potential dramatically changes, wherein upon contact a wave immediately produces a droplet that is under capillary tension, creating a new hydraulically persistent entity. They do not re-merge with the liquid film, but rather absorb liquid and solutes in their path leaving behind a ‘dry’ patch. This poster will show visualization data of developing and evolving capillary droplets, discuss the criteria for droplet formation, pressure gradient calculations and solute transport potential.