On-site Transportation Research Articles

Uranium Solubility of Carbonate-Rich Uranium-Contaminated Soils

A 300 d solubility study involving two carbonate-rich, uranium-contaminated soils from the Department of Energy's Fernald Environmental Management Project site was conducted to predict the behavior of uranium during on-site remediation of these soils. Geochemical modeling was performed on the aqueous species dissolved from these soils following the solubility measurements to predict the on-site uranium leaching and transport potential. Results showed that the soluble levels of the major components (total uranium, calcium, magnesium, and carbonate) increased continually for the first 4 weeks. After the first 4 weeks, these components either reached a steady-state or continued to increase linearly throughout the study. Soluble uranium levels of both soils and their correlation with alkalinity was strongly mediated by the source term of the contamination. Geochemical modeling predicted and anion exchange experiments confirmed that uranyl-carbonate complexes were the most stable and abundant complexes. Further modeling showed that uranium solubility in these soils and in onsite groundwater wells is controlled by UO2(H2PO4)2, but is also mediated by complexation with carbonate and the oxidation state of the uranium. For assessing the risk related to off-site transport of uranium, it should be recognized that the solubility of uranium-bearing minerals is the critical factor in controlling uranium solubility of these soils rather than sorption/desorption processes as measured by the uranium distribution coefficient (Kd) in these soils.

Proton exchange membrane fuel cell systems engineering at Vickers Shipbuilding and Engineering Limited (VSEL)

A project, jointly funded by VSEL and CJB Developments Limited, is aimed at the development of complete power generation systems based on PEM fuel cell technology. Potential markets for such systems are seen as being very broadly based, ranging from military land and marine systems through to commercial on-site power generation and transport. From the outset the project was applications driven, the intent being to identify market requirements, in terms of system specifications and to use these to produce development targets. The two companies have based their work on the Ballard PEM stack and have focused their efforts on the development of supporting systems. This benefits all three companies as it allows Ballard to obtain applications information on which to base future research and VSEL/CJBD are able to capitalise on the advanced development of the Ballard stack. Current work is focused on the production of a 20 kW, methanol fuelled, power generation system demonstrator, although work is also in hand to address a wider range of fuels including natural gas. The demonstrator, when complete, will be used to indicate the potential benefits of such systems and to act as a design aid for the applications phase of the project. Preliminary work on this next phase is already in hand, with studies to assess both systems and fuel cell stack design requirements for specific applications and to generate concept designs. Work to date has concentrated on the development of a methanol reformer, suitable for integration into a fuel cell system and on extensive testing and evaluation of the Ballard fuel cell stacks. This testing has covered a wide range of operating parameters, including different fuel and oxidant combinations. The effect of contaminants on the performance and life of the fuel cells is also under evaluation. PEM fuel cells still require a great deal of further development if they are to gain widespread commercial acceptance. A recent study conducted by VSEL in conjunction with the UK Department of Energy has addressed the fuel cell cost and performance requirements in order to both focus future research and to aid understanding of the time-scale to reach full commercialisation.

Transportation Demand Management Planning, Development, and Implementation

Abstract Transportation demand management (TDM) is the art of modifying travel behavior, usually to avoid more costly expansion of the transportation system. TDM is not a panacea, but it can help ease some transportation problems. TDM requires the cooperation of many actors, who may include developers; landowners; employers; business associations; and municipal, county, regional, and state levels of government. This article reviews new TDM organizational forms, including transportation management associations, trip reduction ordinances, and negotiated public-private agreements. More flexible approaches appear to work best. TDM evaluation is difficult, because reductions in trip generation rates, i.e., relative changes in travel demand, are not easy to measure. Evidence suggests that TDM can be applied in a wide variety of situations, with equally variable, and sometimes quite good, overall results. TDM strategies that often have proven to be effective include on-site employee transportation coordination, parking management provisions, and alternative work schedules.

Characterization of transport in an acidic and metal‐rich mountain stream based on a lithium tracer injection and simulations of transient storage

Physical parameters characterizing solute transport in the Snake River (an acidic and metal‐rich mountain stream near Montezuma, Colorado) were variable along a 5.2‐km study reach. Stream cross‐sectional area and volumetric inflow each varied by a factor of 3. Because of transient storage, the residence time of injected tracers in the Snake River was longer than would be calculated by consideration of convective travel time alone. Distributed inflows along the stream were a significant source of in‐stream chemical variations. These transport characteristics of the Snake River were established on the basis of the assumption of lithium as an ideally conservative tracer and use of simulations of advection, dispersion, and transient storage. Evaluations of the validity of this combined tracer and simulation approach lend confidence to the estimation of the physical transport parameters, but further development is warranted for methods of onsite transport experimentation in hydrologically complex, chemically reactive environments.

Modeling the formation of Early Stone Age artifact concentrations

The nature of stone artifact concentrations at early Plio-Pleistocene sites in East Africa is evaluated with regard to hominid transport behaviors responsible for their formation. These archaeological occurrences indicate ranging behaviors involving deliberate and repeated transport of flaked stone artifacts. The stone transported to archaeological sites within the time range of Homo habilis indicates planned transport of tools or material for tool manufacture to an extent far beyond transport behaviors reported among living apes, even stone hammer-using chimpanzees. Analysis of technological evidence in a lithic assemblage at a Plio-Pleistocene site at Koobi Fora (c. 1·5 ya) indicates on-site manufacturing activities and transport of flaked stone both to and from the site locale. Possible explanations for transport of stone artifacts are discussed in view of hominid strategies of environmental exploitation and resource utilization. A model is proposed for planned, habitual transport of artifacts by hominids positively correlated with distance of planned foraging range. In this model, larger-scale sites tended to develop at locales favorably located near abundant resources, where stone imports were high but export was relaxed due to the proximity of resources to be processed.