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[en] Solutions are proposed for enhancement of the in-service safety of hydraulicked ash-slag dumps with consideration of their hydrothermal regime. An assessment is given for the minimum dimensions of the settling basins and top surface of ash-slag dumps.
[en] Rice husk ash (RHA) which contains more than 90 percent silica is proven to be an active silica source in zeolite synthesis. In this study, nano sodalite has been successfully synthesized hydrothermally at 60 degree Celsius using RHA as silica source in alkaline medium at various crystallization times. Commercial fumed silica was used as comparison for the silica source. Analysis by XRD has shown that pure nano sodalite was formed in 3 hours and stable up to more than 24 hours when using RHA as silica source. On the other hand, fumed silica produced pure nano sodalite only at 4 hours while a mixture of zeolites was observed outside this time range. FESEM shows a worm-like morphology of nano sodalite in the size range of 50-100 nm while FTIR shows the formation of aluminosilicates bonds. Analysis on the dissolved silica in the gel reaction mixture demonstrates the decreasing mass of silica after prolong time of crystallization which indicates the consumption of the dissolved silica in crystal growth of nano sodalite. This study shows that RHA is a better silica source in stabilizing the nano sodalite phase in oxide gel reaction mixture as compared to fumed silica. (author)
[en] The calculations of the optical characteristics of fractal aggregates find important applications in a wide spectrum of disciplines. Consequently, considerable research efforts have been invested to develop models to predict the scattering properties of aggregates. A comprehensive understanding of the accuracy of these models is highly desirable for the users. Therefore, this study assessed two commonly-used fractal scattering models, in terms of their accuracy for predicting both the integrative scattering properties (e.g., the scattering cross section) and the angular scattering properties (e.g., the elements of the Mueller scattering matrix). The results were organized as contour plots with respect to scattering angle and aggregate size to facilitate the estimation of error introduced by these models in practical applications. Meanwhile, a direct comparison and evaluation of these models was also performed, which can potentially enable a hybrid model for better accuracy. This study was conducted under the context of scattering by soot aggregates; hence, the results are expected to be directly applicable for soot characterization by laser scattering
[en] Full text: In this study the ash method has been applied for environmental sample treatment in order to decrease of the detection limit in gamma-ray spectrometry for low level radioactivity measurements. Detection limit in gamma ray spectrometry is the smallest expectation value of the net counting rate that can be detected on given probabilities. The environmental test samples have been changed into ash using a suitable oven. The heating were made under controlled temperature to avoid the escape of some radionuclides such as radiocaesium. The ash samples were measured by high resolution gamma-ray spectrometry system. (author)
[en] In this paper, we show that concentrations of manufactured carbon-based nanoparticles (MCNPs) in aquatic sediments will be negligible compared to levels of black carbon nanoparticles (BCNPs). This is concluded from model calculations accounting for MCNP sedimentation fluxes, removal rates due to aggregation or degradation, and MCNP burial in deeper sediment layers. The resultant steady state MCNP levels are compared with BCNP levels calculated from soot levels in sediments and weight fractions of nanosized fractions of these soot particles. MCNP/BCNP ratios range from 10-7 to 10-4 (w:w). This suggests that the often acclaimed effect of MCNPs on organic pollutant binding and bioavailability will likely be below the level of detection if natural BCNPs are present, even if binding to MCNP is one to two orders of magnitude stronger than to BCNPs. Furthermore, exposure and toxic effects of MCNPs in sediments and soils will be negligible compared to that of BCNPs. - Concentrations of manufactured carbon-based nanoparticles in sediments and soils will be negligible compared to levels of black carbon (soot) nanoparticles
[en] 'Full text:' From 1816 to about 1960, thousands of manufactured gas plants (MGP) throughout North America produced gas for lights and heating. Although most plants were decommissioned in the mid-1900's, much of the waste residues legally disposed at MGP sites may now pose a risk to humans and the environment. The residues from the various MGP processes contain large amounts of soot and other carbonaceous material. The presence of this carbon results in material that visually appears different than a normal soil. In addition, the aromatic structure of the residue can effect the release of the chemicals from MGP soils. In this investigation, the chemicals of concern in the residue were polycylic aromatic hydrocarbons (PAHs). Despite being found at relatively high concentrations, PAHs in MGP soils can be relatively immobile and not available to human and organisms. The focus of this research was to investigate what circumstances cause PAHs to be mobile or immobile in MGP site soils. The fast release fraction, an indicator of mobility, of PAHs in ten MGP site soils was determined using a four-month batch water extraction study. In addition, each soil was analyzed to determine site specific soil matrix and PAH compositions. The structural composition of the carbonaceous material in the MGP soil and the weathering of PAHs present in the MGP soils were both used to infer mechanisms of sequestration and desorption for PAHs from MGP site soils. In addition, deuterated PAHs were spiked onto some MGP sites soils prior to a four month batch water extraction. The comparison of the spiked deuterated PAHs and the resident PAHs illustrated site specific mechanisms for PAHs in MGP site soils. The knowledge of the mechanisms of desorption from PAHs from MGP soils can enhance the selection a proper remediation strategy at MGP sites. The laboratory work for this research has been completed, the data is currently being analyzed and the results will be fully evaluated by early 2002. (author)
[en] The 124 papers of these proceedings are arranged under the following topical sections: Minerals education; Hydrology--Characterization and monitoring; Tailings--Reclamation; Reforestation; Mine drainage--Biogeochemical processes; Mine drainage--Treatment, general; Mine drainage--Passive treatment, wetlands; Mine drainage--Prediction and monitoring; Acid soils--Reclamation practices; Wildlife and fisheries habitat; Subsidence--Engineering practices and environmental effects; OSM acid forming materials mini workshops; RUSLE--Erosion prediction techniques on mined construction and reclaimed lands; IDNR wetlands technology transfer program; Mine planning and postmining land use; Vegetation establishment--Principles and practices; Vegetation establishment--Warm season grasses; Coal combustion by-products--General; Coal combustion by-products--Mine drainage treatment; and Prime farmland reclamation and mine soils management. Papers within scope have been processed separately for inclusion on the data base
[en] Highlights: • The PaSR-based soot model proposed by the authors’ group has been further improved. • The present model is physically more sound. • The improved model has been implemented into the in-house version of the FireFOAM code. • New formulas have been proposed to compute characteristic time for soot formation and oxidation. • The predictions have achieved improved agreement with the experimental measurements. - Abstract: The extension of the laminar smoke point based approach to turbulent combustion using the partially stirred reactor (PaSR) concept proposed by Chen et al. (2014) has been further improved to overcome the limitation in the formulations of Chen et al. (2014) which assumed infinitely fast soot oxidation chemistry and constant soot formation characteristic time. In the PaSR approach, each computational cell is split into two zones: the reacting zone and the non-reacting zone. Soot formation and oxidation are assumed to take place at finite rates in the reacting zone and computed from the corresponding laminar rates and the mass fractions for soot formation and oxidation, which are evaluated in each computational cell from the characteristic time scales for turbulent mixing, soot formation and oxidation. Since soot would be produced in not only the fine structures but also surrounding fluids in the Eddy-Dissipation-Concept (EDC) model, the average field parameters between the fine structure and surrounding fluid are employed instead of those Favre-averaged values in Chen et al.’s soot formation model. The newly extended model has been implemented in FireFOAM, a large eddy simulation (LES) based solver for fire simulation based on the open source CFD code OpenFOAM®. Numerical simulations of a 30 cm diameter heptane and toluene pool fires tested by Klassen and Gore (1992) were performed for validation. The predicted soot volume fraction and temperature have achieved improved agreement with the experimental measurements in comparison with that of Chen et al. (2014), demonstrating the potential of the improved PaSR-based soot model for fire applications.
[en] A light scattering method based on the Rayleigh-Debye approach quantifying the angular scattering from poly-disperse aggregates was tested in an attempt to measure the mean radius of gyration of diesel soot aggregates in diesel exhaust. The aggregate size measured by this method under steady operating conditions showed qualitative agreement with the mode peak mobility diameter obtained by the scanning mobility particle sizer. After the assessment, the method was applied to measure the temporal variation of the mean radius of gyration of diesel soot aggregates under transient mode operation