Environmental Geosciences

Recent research includes: Studies which seek to understand ground-water flow and contaminant transport at multiple scales; studies in environmental geochemistry; and the study of phyllosilicates.

Personnel

Richelle Allen-King, Hydrogeochemistry, ground-water contaminant transport, nutrients in watersheds, organic pollutants, environmental geochemistry
Matthew Becker, Ground-water contaminant transport, colloid and microbe transport in ground water, fractured rock hydrology, numerical ground-water modeling
Rossman Giese, Mineralogy with emphasis on clay minerals, surface thermodynamic measurement of minerals, interactions with organic minerals, especially biomoleculres

Tracy Bank, Biogeochemistry

Zhangshuan Hou, Near Surface Geophysics, Geostatistics and Stochastic Hydrogeology, Vadose Zone Hydrology, Climate Change.

Description

We work to understand how pollutants cycle through terrestrial water, with particular attention to ground water. This research is conducted in the laboratory, the field, and even from satellites. Our study areas are as small as a pore volume or as large as a whole watershed.

Remote Sensing of Ground Water

Ground water resources was once a problem of finding water. It has now become a problem of finding CLEAN water. Aquifers can be contaminated from so many sources that new technology must be developed to characterize ground water systems at the regional scale and organize tremendous amounts of water quality monitoring data.

We are using satellite data to help quantify regional ground water flow and pollution [Becker, in press]. For example, the figure on the left is a ASTER false infra-red image of the Albuquerque, New Mexico area. The Rio Grande loses water to the aquifer in this area and is consumed by water-table tapping vegetation (phreatophytes), irrigation wells, and drinking wells. By measuring energy budgets for the region, a water balance between subsurface and surface water is calculated.

With the UB Groundwater Group we are developing regional ground-water models using the Analytic Element Method. In this modeling approach ground water flow is solved using superposition of analytic equations. It allows more flexibility with respect to scale of analysis because the resolution of the model depends on the amount of information (number of elements) rather than a grid cell size. This example is for the Northern Highland Lakes Region. At left, the Analytic Element representation of the problem, at right the calculated water table with topography superimposed.

   

Hydrogeophysical Investigations of Fractured Rock

Water is thought to form complex flow channels as it moves through fractured bedrock. Channelled flow makes it difficult to predict how fast ground water contaminants will migrate in bedrock systems or develop monitoring systems that can detect contaminants in bedrock. The simulations below illustrate the problem.

Our group produced the first images channelized flow through bedrock using ground penetrating radar (GPR). Saline fluid was injected into a shallow fracture which reflected the GPR energy to the surface [Talley et al., 2005].

The figure below shows an image before after saline injection. At left is the difference between two background radar maps (no saline injected) and before and after saline injection. The channelized nature of flow is clear from the image. Where would a monitoring well be placed if one wanted to be sure to capture this contamination?

Aquifer Heterogeneity and Contaminant Transport:

Contaminant transport in groundwater can be strongly affected by reactions with aquifer materials. But, determining how aquifer sediment heterogeneity at both the grain (and subgrain) and contaminant plume scales vary and affect contaminant movement are simple problems! Our group has taken on these challenges by looking at contaminant reactions to sediments at both small and large scales. Our hypothesis is that the processes that sort sediments into mappable units also create packages of sediments with chemically, as well as physically, distinct properties that affect contaminant transport (Figure 1).

In order to test the hypothesis, we have collected cores of material from below the groundwater table at the Borden site. Then we map the lithology of the scanned cores, and measure the permeability and sorption behavior for the contaminant perchloroethene or PCE (Figure 2).

Figure 3 shows the results of sorption measurements for a wide concentration range alongside components isolated from the sediment. Our model suggests that different components of the sediment control sorption behavior over different concentration ranges.

Figure 4 shows the only map of the distribution of chemical reactivity (as the ln Kd for PCE) for an organic pollutant available, to our knowledge. There is obvious layering of contaminant reactivity that is associated with the layered structure of the aquifer.

If the hypothesis is supported, then mapping sedimentary ithofacies will provide important insights on the variability of aquifer reactivity. We are approaching this aspect of the work by comparing geophysical and sedimentological logs of a cut that we created in the sedimentary materials. This is a collaborative project with geophysicist R. Knight from Stanford University and sedimentologist D. Gaylord from Washington State University. An example of the outcrop that we created as well as one of our many site visitors are presented in Figure 5.

References:

Becker, M.W., Potential for satellite remote sensing of ground water, Ground Water, in press.

Talley, J., G.S. Baker, M.W. Becker, and N. Beyrle, Four dimensional mapping of tracer channelization in subhorizontal bedrock fractures using surface ground penetrating radar, Geophys. Res. Lett., 32 (doi:10.1029/2004GL021974), 2005.