21 research outputs found
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Work to save dose: contrasting effective dose rates from radon exposure in workplaces and residences against the backdrop of public and occupational limits
Office workers are exposed to radon while at work and at home. Though there has been a multitude of studies reporting the measurements of radon concentrations and potential lung and effective doses associated with radon and progeny exposure in homes, similar studies on the concentrations and subsequent effective dose rates in the non-mine workplaces are lacking. Additionally, there are few, if any, comparative analyses of radon exposures at more 'typical' workplace with residential exposures within the same county. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico, USA. The sampling periods for these measurements were generally about three months. The measured concentrations were used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about 8 times greater exposure at home than while in the office (2.3 mSv yr-! versus 0.3 mSv yr-!). The estimated effective dose rate for a more homebound person was about 3 mSv yr-!. Estimating effective doses from background radon exposure in the same county as Los Alamos National Laboratory, with thousands of'radiological workers,' highlights interesting contrasts in radiation protection standards that span public and occupational settings. For example, the effective dose rate from background radon exposure in unregulated office spaces ranged up to 1.1 mSv yr-!, which is similar to the 1 mSv yr-! threshold for regulation ofa 'radiological worker,' as defined in the Department of Energy regulations for occupational exposure. Additionally, the estimated average effective dose total of> 3 mSv yf! from radon background exposure in homes stands in contrast to the 0.1 mSv yr-! air pathway effective public dose limit regulated by the Environmental Protection Agency for radioactive air emissions
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Adaptive management: a paradigm for remediation of public facilities
Public facility restoration planning traditionally focused on response to natural disasters and hazardous materials accidental releases. These plans now need to integrate response to terrorist actions. Therefore, plans must address a wide range of potential vulnerabilities. Similar types of broad remediation planning are needed for restoration of waste and hazardous material handling areas and facilities. There are strong similarities in damage results and remediation activities between unintentional and terrorist actions; however, the uncertainties associated with terrorist actions result in a re-evaluation of approaches to planning. Restoration of public facilities following a release of a hazardous material is inherently far more complex than in confined industrial settings and has many unique technical, economic, social, and political challenges. Therefore, they arguably involve a superset of drivers, concerns and public agencies compared to other restoration efforts. This superset of conditions increases complexity of interactions, reduces our knowledge of the initial conditions, and even condenses the timeline for restoration response. Therefore, evaluations of alternative restoration management approaches developed for responding to terrorist actions provide useful knowledge for large, complex waste management projects. Whereas present planning documents have substantial linearity in their organization, the 'adaptive management' paradigm provides a constructive parallel operations paradigm for restoration of facilities that anticipates and plans for uncertainty, multiple/simUltaneous public agency actions, and stakeholder participation. Adaptive management grew out of the need to manage and restore natural resources in highly complex and changing environments with limited knowledge about causal relationships and responses to restoration actions. Similarities between natural resource management and restoration of a facility and surrounding area(s) after a disruptive event suggest numerous advantages over preset linearly-structured plans by incorporating the flexibility and overlap of processes inherent in effective facility restoration. We discuss three restoration case studies (e.g., the Hart Senate Office Building anthrax restoration, Rocky Flats actinide remediation, and hurricane destruction restoration), that implement aspects of adaptive management but not a formal approach. We propose that more formal adoption of adaptive management principles could be a basis for more flexible standards to improve site-specific remediation plans under conditions of high uncertainty
Interactive effects of grazing and burning on wind- and water-driven sediment fluxes: Rangeland management implications
Rangelands are globally extensive, provide fundamental ecosystem services, and are tightly coupled human-ecological systems. Rangeland sustainability depends largely on the implementation and utilization of various grazing and burning practices optimized to protect against soil erosion and transport. In many cases, however, land management practices lead to increased soil erosion and sediment fluxes for reasons that are poorly understood. Because few studies have directly measured both wind and water erosion and transport, an assessment of how they may differentially respond to grazing and burning practices is lacking. Here, we report simultaneous, co-located estimates of wind- and water-driven sediment transport in a semiarid grassland in Arizona, USA, over three years for four land management treatments: control, grazed, burned, and burned + grazed. For all treatments and most years, annual rates of wind-driven sediment transport exceeded that of water due to a combination of ongoing small but nontrivial wind events and larger, less frequent, wind events that generally preceded the monsoon season. Sediment fluxes by both wind and water differed consistently by treatment: burned + grazed > burned >> grazed >/= control, with effects immediately apparent after burning but delayed after grazing until the following growing season. Notably, the wind: water sediment transport ratio decreased following burning but increased following grazing. Our results show how rangeland practices disproportionally alter sediment fluxes driven by wind and water, differences that could potentially help explain divergence between rangeland sustainability and degradation.Peer reviewedNatural Resource Ecology and Managemen
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Skin Dose Equivalent Measurement from Neutron-Deficient Isotopes.
Neutron-deficient-isotopes decay via positron emission and/or electron capture often followed by x-ray, gamma-ray, and 0.511 MeV photons from positron annihilation. For cases of significant area and/or personnel contamination with these isotopes, determination of skin dose equivalent (SDE) is required by 10CFR835. For assessment of SDE, we evaluated the MICROSPEC-2(TM) system manufactured by Bubble Technology Industries of Canada which uses three different probes for dose measurement. We used two probes: (1) the X-probe which measures lower energy (4 - 120 keV) photon energy distributions and determines deep dose equivalent, SDE and dose equivalent to eyes, and (2) the B-probe which measures electron (positron) energy distributions, and determines skin dose equivalent. Also, the measured photon and beta spectra can be used to identify radioactive isotopes in the contaminated area. Measurements with several neutron-deficient sources showed that this system provided reasonably accurate SDE rate measurements when compared with calculated benchmark SDE rates with an average percent difference of 40%. Variations were expected because of differences between the assumed geometries used by MlCROSPEC-2 and the calculations when compared to the measurement conditions
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The ecology of dust: local- to global-scale perspectives
Emission and redistribution of dust due to wind erosion in drylands drives major biogeochemical dynamics and provides important aeolian environmental connectivity at scales from individual plants up to the global scale. Yet, perhaps because most relevant research on aeolian processes has been presented in a geosciences rather than ecological context, most ecological studies do not explicitly consider dust-driven processes. To bridge this disciplinary gap, we provide a general overview of the ecological importance of dust, examine complex interactions between wind erosion and ecosystem dynamics from the plant-interspace scale to regional and global scales, and highlight specific examples of how disturbance affects these interactions and their consequences. Changes in climate and intensification of land use will both likely lead to increased dust production. To address these challenges, environmental scientists, land managers and policy makers need to more explicitly consider dust in resource management decisions
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Estimated effective dose rates from radon exposure in workplaces and residences within Los Alamos county in New Mexico
Many millions of office workers are exposed to radon while at work and at home. Though there has been a multitude of studies reporting the measurements of radon concentrations and potential lung and effective doses associated with radon and progeny exposure in homes, similar studies on the concentrations and subsequent effective dose rates in the workplace are lacking. The purposes of this study were to measure radon concentrations in office and residential spaces in the same county and explore the radiation dose implications. Sixty-five track-etch detectors were deployed in office spaces and 47 were deployed in residences, all within Los Alamos County, New Mexico, USA. The sampling periods for these measurements were generally about three months. The measured concentrations were then used to calculate and compare effective dose rates resulting from exposure while at work and at home. Results showed that full-time office workers receive on average about nine times greater exposure at home than while in the office (691 mrem yr{sup -1} versus 78 mrem yr{sup -1}). The estimated effective dose rate for a more homebound person was 896 mrem yr{sup -1}. These effective dose rates are contrasted against the 100 mrem yr{sup -1} threshold for regulation of a 'radiological worker' defined in the Department of Energy regulations occupational exposure and the 10 mrem yr{sup -1} air pathway effective public dose limit regulated by the Environmental Protection Agency
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Computational modeling and analysis of airflow in a tritium storage room
In this study, a commercial computational fluid dynamics (CFD) code, CFX-5.5, was utilized to assess flow field characteristics, and to simulate tritium gas releases and subsequent transport in a storage room in the tritium handling facility at Los Alamos. This study was done with mesh refinement and results compared. The results show a complex, ventilation-induced flow field with vortices, velocity gradients, and stagnant air pockets. This paper also explains the timedependent gas dispersion results. The numerical analysis method used in this study provides important information that is possible to be validated with an experimental technique of aerosol tracer measurement method frequently used at Los Alamos. Application of CFD can have a favorable impact on the design of ventilation systems and worker safety with consideration to facility costs
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Computational modeling and analysis of a flow in a storage room
When a radioactive material gas is accidentally released with a room, the present of the hazardous gas will directly affect the people safety inside. In this study, the flow field and gas dispersion in a ventilated tritium storage room at Los Alamos National Laboratory was simulated using CFX-5.5, a commercially available CFD package using a finite volume methodology. CFD models provide a simultaneously numerical solution of continuity, Navier-Stokes, and energy equations for a flow field geometry with specified boundary conditions. CFX-5 uses a coupled solver, which solves the hydrodynamic equations (for u, v, w, p) as a single system. This reduces the number of iterations required for convergence to a steady state, and to a transient analysis solution for each time step in time-dependant gas dispersion as well
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Towards a phoenix phase in aeolian research: shifting geophysical perspectives from fluvial dominance
Aeolian processes are a fundamental driver of earth surface dynamics, yet the importance of aeolian processes in a broader geosciences context may be overshadowed by an unbalanced emphasis on fluvial processes. Here we wish to highlight that aeolian and fluvial processes need to be considered in concert relative to total erosion and to potential interactions, that relative dominance and sensitivity to disturbance vary with mean annual precipitation, and that there are important scale-dependencies associated with aeolian-fluvial interactions. We build on previous literature to present relevant conceptual syntheses highlighting these issues. We then highlight the relative investments that have been made in aeolian research on dust emission and management relative to that in fluvial research on sediment production. Literature searches highlight that aeolian processes are greatly understudied relative to fluvial processes when considering total erosion in different environmental settings. Notably, within the USA, aeolian research was triggered by the Dust Bowl catastrophe of the 1930s, but the resultant research agencies have shifted to almost completely focusing on fluvial processes, based on number of remaining research stations and on monetary investments in control measures. However, numerous research issues associated with intensification of land use and climate change impacts require a rapid ramping up in aeolian research that improves information about aeolian processes relative to fluvial processes, which could herald a post-Dust Bowl Phoenix phase in which aeolian processes are recognized as broadly critical to geo- and environmental sciences