DIFFUSION SAMPLERS AS A GROUND-WATER/SURFACE-WATER INTERFACE MONITORING TOOL

Diffusion samplers have been widely used for determining ground-water solute concentrations. Their use dates back to at least the 1970's when “peeper” and other sampling devices were first deployed to determine small-scale spatial variations in pore-water chemistry in the bottom sediment of lakes. Diffusion samplers have been used since at least the 1990s to examine volatile organic compounds in pore water. Since that time, the use of diffusion samplers has been subjected to rigorous testing, obtained widespread regulatory acceptance, and expanded into other areas of ground-water monitoring. This presentation will discuss the evolution of the diffusion sampler as a tool for resolving the spatial heterogeneity of solute concentrations in streambeds and lakebeds, which is a critical part of determining mass fluxes across the ground-water surface-water interface (GWSWI). It also will examine diffusion samplers as a tool to easily determine dissolved hydrogen (H2) concentrations in pore water at the GWSWI. H2 is an important indicator of redox conditions, which can influence degradation and transformation of solutes at the GWSWI, thereby influencing solute flux.