Visual Data Analysis as an Integral Part of Environmental Management.

The U.S. Department of Energy's (DOE) Office of Environmental Management (DOE/EM) currently supports an effort to understand and predict the fate of nuclear contaminants and their transport in natural and engineered systems. Geologists, hydrologists, physicists and computer scientists are working together to create models of existing nuclear waste sites, to simulate their behavior and to extrapolate it into the future. We use visualization as an integral part in each step of this process. In the first step, visualization is used to verify model setup and to estimate critical parameters. High-performance computing simulations of contaminant transport produces massive amounts of data, which is then analyzed using visualization software specifically designed for parallel processing of large amounts of structured and unstructured data. Finally, simulation results are validated by comparing simulation results to measured current and historical field data. We describe in this article how visual analysis is used as an integral part of the decision-making process in the planning of ongoing and future treatment options for the contaminated nuclear waste sites. Lessons learned from visually analyzing our large-scale simulation runs will also have an impact on deciding on treatment measures for other contaminated sites.

Feedbacks between hydrological heterogeneity and bioremediation induced biogeochemical transformations.

For guiding optimal design and interpretation of in situ treatments that strongly perturb subsurface systems, knowledge about the spatial and temporal patterns of mass transport and reaction intensities are important. Here, a procedure was developed and applied to time-lapse concentrations of a conservative tracer (bromide), an injected amendment (acetate) and reactive species (iron(II), uranium(VI) and sulfate) associated with two field scale biostimulation experiments, which were conducted successively at the same field location over two years. The procedure is based on a temporal moment analysis approach that relies on a streamtube approximation. The study shows that biostimulated reactions can be considerably influenced by subsurface hydrological and geochemical heterogeneities: the delivery of bromide and acetate and the intensity of the sulfate reduction is interpreted to be predominantly driven by the hydrological heterogeneity, while the intensity of the iron reduction is interpreted to be primarily controlled by the geochemical heterogeneity. The intensity of the uranium(VI) reduction appears to be impacted by both the hydrological and geochemical heterogeneity. Finally, the study documents the existence of feedbacks between hydrological heterogeneity and remediation-induced biogeochemical transformations at the field scale, particularly the development of precipitates that may cause clogging end flow rerouting.

Ferrographic tracking of bacterial transport in the field at the narrow channel focus area, Oyster, VA.

The first results from an innovative bacterial tracking technique, ferrographic capture, applied to bacterial transport in groundwater are reported in this paper. Ferrographic capture was used to analyze samples during an October 1999 bacterial injection experiment at the Narrow Channel focus area of the South Oyster site, VA. Data obtained using this method showed that the timing of bacterial breakthrough was controlled by physical (hydraulic conductivity) heterogeneity in the vertical dimension as opposed to variation in sedimentsurface or aqueous chemical properties. Ferrographic tracking yielded results that compared well with results from other tracking techniques over a concentration range of 8 orders of magnitude and provided a low detection limit relative to most other bacterial tracking techniques. The low quantitation limit of this method (approximately 20 cells/mL) allowed observation of transport of an adhesion-deficient bacterium over distances greater than 20 m in the fine sand aquifer underlying this site.