276 research outputs found
Evaluation of measured dissolved and bio-met predicted bioavailable Cu, Ni and Zn concentrations in runoff from three urban catchments
Urban runoff is a diffuse source of pollution contributing to the poor ecological and chemical status of surface waters. Whilst the EU Priority Hazardous Substances Directive now identifies environmental quality standards for selected metals in relation to the bioavailable metal fraction the relationship between analytically determined metal size fractions transported by urban runoff and the often variably defined concept of bioavailability has not been thoroughly evaluated. This paper provides a review of the terminology used within urban runoff studies to characterise metal fractions and behaviour. Measured dissolved and truly dissolved (determined by ultrafiltration; <3000 molecular weight cutoff) Cu, Ni, and Zn concentrations are also compared to the bioavailable metal fraction (as predicted using Bio-met, a simplified biotic ligand model) in snowmelt and rainfall derived runoff samples from three urban catchments. The study shows that predicted bioavailable concentrations were significantly lower than truly dissolved concentrations for all metals and discusses current bioavailability modelling parameters in relation to rainfall and snowmelt runoff data sets. Statistical analysis of relationships between field and predicted bioavailable data sets indicate that the bioavailable fractions originate from both colloidal and truly dissolved fractions
Metal size distribution in rainfall and snowmelt-induced runoff from three urban catchments
The size distribution of metals transported by urban runoff has implications for treatment type and design, predicting their mobility and evaluating their potential impact on receiving waters. There is an urgent need to better understand the distribution of metals between fractions, particularly those in the sub-dissolved fractions. As a contribution to addressing this need, this study characterises the size distribution of Cd, Cr, Cu, Ni, V and Zn using conventional and novel techniques. Data is presented as event mean concentrations (EMC) of a total of 18 rainfall and snowmelt events at three urban sites. For all studied metals in all events and at all sites, the contribution of the truly dissolved fraction made a greater contribution to the total concentrations than the colloidal fraction. Truly dissolved Cd and Zn concentrations contributed (on average) 26% and 28% respectively, of the total EMCs with truly dissolved Cu and Ni contributing (on average) 18%. In contrast, only 1% (V) and 3% (Cr) were identified in the truly dissolved fraction. The greatest contribution of truly dissolved Cd, Cu and Zn concentrations (relative to total oncentrations) were reported during rainfall events. However, no seasonal differences were identified and differences between the sites regarding the EMCs distribution by fractions were not at a statistically significant level (p N 0.05) for any metal or event. The loads of truly dissolved and colloidal metals did not follow the patterns of particulate metal loads indicating particulates are not the main source of subdissolved metals. The data suggests that ultrafiltration as a treatment technique would not efficiently mitigate the risks posed by metals to receiving water cologie
Ion counting efficiencies at the IGISOL facility
At the IGISOL-JYFLTRAP facility, fission mass yields can be studied at high
precision. Fission fragments from a U target are passing through a Ni foil and
entering a gas filled chamber. The collected fragments are guided through a
mass separator to a Penning trap where their masses are identified. This
simulation work focuses on how different fission fragment properties (mass,
charge and energy) affect the stopping efficiency in the gas cell. In addition,
different experimental parameters are varied (e. g. U and Ni thickness and He
gas pressure) to study their impact on the stopping efficiency. The simulations
were performed using the Geant4 package and the SRIM code. The main results
suggest a small variation in the stopping efficiency as a function of mass,
charge and kinetic energy. It is predicted that heavy fragments are stopped
about 9% less efficiently than the light fragments. However it was found that
the properties of the U, Ni and the He gas influences this behavior. Hence it
could be possible to optimize the efficiency.Comment: 52 pages, 44 figure
Fractionnement granulométrique de métaux dissous dans les eaux pluviales à Umeå, Suède
Colloque avec actes et comité de lecture. Internationale.International audienc
Light-ion Production And Fission Studies Using The Medley Facility At Tsl
oS(FNDA2006)001 © Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence
Effective triplet interactions in nematic colloids
Three-body effective interactions emerging between parallel cylindrical rods
immersed in a nematic liquid crystals are calculated within the Landau-de
Gennes free energy description. Collinear, equilateral and midplane
configurations of the three colloidal particles are considered. In the last two
cases the effective triplet interaction is of the same magnitude and range as
the pair one
Propagation of nuclear data uncertainties for ELECTRA burn-up calculations
The European Lead-Cooled Training Reactor (ELECTRA) has been proposed as a
training reactor for fast systems within the Swedish nuclear program. It is a
low-power fast reactor cooled by pure liquid lead. In this work, we propagate
the uncertainties in Pu-239 transport data to uncertainties in the fuel
inventory of ELECTRA during the reactor life using the Total Monte Carlo
approach (TMC). Within the TENDL project the nuclear models input parameters
were randomized within their uncertainties and 740 Pu-239 nuclear data
libraries were generated. These libraries are used as inputs to reactor codes,
in our case SERPENT, to perform uncertainty analysis of nuclear reactor
inventory during burn-up. The uncertainty in the inventory determines
uncertainties in: the long-term radio-toxicity, the decay heat, the evolution
of reactivity parameters, gas pressure and volatile fission product content. In
this work, a methodology called fast TMC is utilized, which reduces the overall
calculation time. The uncertainty in the long-term radiotoxicity, decay heat,
gas pressure and volatile fission products were found to be insignificant.
However, the uncertainty of some minor actinides were observed to be rather
large and therefore their impact on multiple recycling should be investigated
further. It was also found that, criticality benchmarks can be used to reduce
inventory uncertainties due to nuclear data. Further studies are needed to
include fission yield uncertainties, more isotopes, and a larger set of
benchmarks.Comment: 4 pages, 4 figures, Proc. 2013 International Conference on Nuclear
Data for Science & Technology (ND2013), March 4-8, 2013, New York, USA, to be
published in Nuclear Data Sheet
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