Tracing Suspended Sediment in the Subsurface Using Beryllium-7 Isotope

Abstract

As water that flows through areas of limestone, karst inevitably develops creating sinking streams that transport alumino-silicate soil particles from the surface into the subsurface. Sediment budget studies on short term scales through karst are rare. Thus, a feasibility study using beryllium-7 that attaches to soil particles and can thus be used as a short-term tracer of sediment movement in karst is proposed.

Sediment and soil samples were collected from the Green River Basin, both on the surface and in the subsurface along a cave stream. Samples were collected prior to and immediately after a recharge event that transported sediment into the subsurface. The pre-event samples were analyzed for the activity of beryllium-7 to establish a baseline activity for the isotope. The post-event samples that were collected from the same locations as the pre-event samples were collected, and then analyzed beryllium-7 activity as well. The expectation is that the activity of beryllium-7 will be higher in the samples collected after the recharge event and will show that beryllium-7 is a viable short-term sediment tracer through karst systems. Grain size analysis on a representative number of the samples will be performed in order to find correlation between grain surface area and beryllium-7 absorption rate to soil particles to examine the effectiveness of beryllium-7.

AAPG Datapages/Search and Discovery Article #90219 © 2015 GCAGS, Houston, Texas, September 20-22, 2015