Citation:

Scruggs, C., M. Briggs, F. Day-Lewis, D Werkema, AND J. Lane. The Dual‐Domain Porosity Apparatus: Characterizing Dual Porosity at the Sediment/Water Interface. Groundwater. Wiley-Blackwell, Hoboken, NJ, 57(4):640-646, (2019). https://doi.org/10.1111/gwat.12846

Impact/Purpose:

Groundwater contamination hydraulically connected to surface water pose a threat to aquatic species and human health. Understanding the movement of contamination within groundwater and at the interface with surface water features is critical to protect these environments and health of organisms dependent on these environments. This paper presents the Dual-Domain Porosity Apparatus, which can be used at field scales to understand the mobile and less-mobile porosity within such environments. This is important to understand the fate and transport of contaminants into surface water bodies. Regional partners, state, local, tribal, and the scientific public will find this useful for site characterization, conceptual site model development, contaminant fate and transport studies, and contaminated site decision making.

Description:

The characterization of pore-space connectivity in porous media at the sediment/water interface (SWI) is critical to understanding contaminant transport and reactive biogeochemical processes in zones of groundwater and surface-water exchange. Previous in situ studies of dual-domain (i.e., mobile/less-mobile porosity) studies have been limited to solute tracer injections at scales of meters to 100's of meters and subsequent numerical model parameterization using fluid concentration histories. Pairing fine-scale (e.g., sub-meter) geoelectrical measurements with fluid tracer data over time alleviates dependence on flowpath-scale experiments, enabling spatially targeted characterization of shallow SWI media where biogeochemical reactivity is often high. The DDPA is a field-tested device capable of variable rate-controlled downward flow experiments. The Dual-Domain Porosity Apparatus facilitates meter-scale inference of dual-domain parameters, i.e., mobile/less-mobile exchange rate coefficient and the ratio of less mobile to mobile porosity. The DDPA experimental procedure uses water electrical conductivity as a conservative tracer of differential loading and flushing of pore spaces within the region of measurement. Variable injection rates permit the direct quantification of the flow-dependence of dual-domain parameters, which has been theorized for decades but remains challenging to assess using existing experimental methodologies.

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