Roelof Versteeg

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[1] Arsenic concentrations measured by graphite furnace atomic absorption range from < 5 to 900 mg/L in groundwater pumped from 6000 wells within a 25 km area of Bangladesh. The proportion of wells that exceed the Bangladesh standard for drinking water of 50 mg/L arsenic increases with depth from 25% between 8 and 10 m to 75% between 15 and 30 m, then(More)
Sediment and groundwater profiles were compared in two villages of Bangladesh to understand the geochemical and hydrogeological factors that regulate dissolved As concentrations in groundwater. In both villages, fine-grained sediment layers separate shallow aquifers ( 28 m) high in As from deeper aquifers (40–90 m) containing 10 g/L As. In one village(More)
Lamont-Doherty Earth Observatory of Columbia University, Palisades, New York 10964, USA e-mail: avangeen@ldeo.columbia.edu, Phone: (845) 365 8644, Fax: (845) 365 8154. Queens College, City University of New York, Flushing, New York 11367, USA Idaho National Environmental and Engineering Laboratory, Idaho Falls, ID 83404, USA Barnard College, New York, New(More)
Previous work in the Instrumented Oil-Field DDDAS project has enabled a new generation of data-driven, interactive and dynamically adaptive strategies for subsurface characterization and oil reservoir management. This work has led to the implementation of advanced multiphysics, multi-scale, and multi-block numerical models and an autonomic software stack(More)
High frequency asymptotic approximation of the acoustic Green's function leads to eecient modeling and migration methods for primaries only reeection seismograms. A volume (as opposed to interface) oriented description of reeectivity allows symmetry between modeling and migration. With proper selection of amplitudes and dis-cretization, the migration and(More)
Calcium carbonate is a secondary mineral precipitate influencing zero valent iron (ZVI) barrier reactivity and hydraulic performance. We conducted column experiments to investigate electrical signatures resulting from concurrent CaCO(3) and iron oxides precipitation under simulated field geochemical conditions. We identified CaCO(3) as a major mineral phase(More)
The predictive capability of groundwater flow models is frequently restricted by insufficient characterisation of a typically heterogeneous and anisotropic subsurface. Trace levels of volatile organic compounds have been detected at municipal water supply wells in Gray, Maine. Groundwater flow modelling based on available hydrogeologic data defines a(More)
We describe the design and implementation of a web-accessible scientific workflow system for environmental performance monitoring. This workflow environment integrates distributed automated data acquisition with server side data management and information visualization through flexible browser-based data access tools. Component technologies include a rich(More)
CMMAD is a risk reduction effort for the AMDS program. As part of CMMAD, multiple instances of semi autonomous robotic mine detection systems were created. Each instance consists of a robotic vehicle equipped with sensors required for navigation and marking, countermine sensors and a number of integrated software packages which provide for real time(More)
Three-dimensional variably saturated flow and multicomponent biogeochemical reactive transport modeling, based on published and newly generated data, is used to better understand the interplay of hydrology, geochemistry, and biology controlling the cycling of carbon, nitrogen, oxygen, iron, sulfur, and uranium in a shallow floodplain. In this system,(More)