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Arsenic (As), chromium (Cr), and vanadium (V) are naturally occurring, redox-active elements that can become human health hazards when they are released from aquifer substrates into groundwater that may be used as domestic or irrigation source. As such, there is a need to develop incisive conceptual and quantitative models of the geochemistry and transport of potentially hazardous elements to assess risk and facilitate interventions. However, understanding the complexity and heterogeneous subsurface environment requires knowledge of solid-phase minerals, hydrologic movement, aerobic and anaerobic environments, microbial interactions, and complicated chemical kinetics. Here, we examine the relevant geochemical and hydrological information about the release and transport of potentially hazardous geogenic contaminants, specifically As, Cr, and V, as well as the potential challenges in developing a robust understanding of their behavior in the subsurface. We explore the development of geochemical models, illustrate how they can be utilized, and describe the gaps in knowledge that exist in translating subsurface conditions into numerical models, as well as provide an outlook on future research needs and developments.

We have developed a general-purpose sensor to measure several flow properties simultaneously. The instrument is very compact, simple to use, accurate, and cost-effective. VDV can measure 3dimensional velocity, buoyancy flux and vorticity using advanced ultrasonics. The measurements are simultaneous and are sampled in the same volume ofwater. This guarantees very high correlation between the velocity, density and vorticity data. This is essential in energetic, rapidly fluctuating coastal environments, as well as in some low-speed deep ocean applications. We have completed a series of tests in a large laboratory tow-tank and in a wave flume at the Canada Centre for Inland Waters. This paper will report on the initial results of the tests.