Metal(loid) liberation from Alaskan coal combustion products as a function of time in various aqueous media

Thesis (M.S.) University of Alaska Fairbanks, 2018Little is known about the fate and potential toxicity of metal(loid)s that could be leached from coal combustion products by a (sub- )Arctic environment. Several potentially toxic elements are enriched in coal combustion products relative to the average crustal abundance including As, Cu, Se, and Sb. The overarching goal of this project is to examine the release of these and other metal(loid)s from early stage coal ash and fly ash from the University of Alaska Fairbanks (UAF) power plant and identify transformations in the presence of aqueous environmental media. Bioaccessibility experiments performed indicate that early stage coal ash and fly ash contain bioaccessible Cr, As, Se, Sb, and Pb. Bioaccessible concentrations of these commonly known toxic metal(loid)s were found to exceed EPA drinking water and freshwater regulations. Early stage coal ash and fly ash was reacted with 18 MΩ H₂O (control) or simulated rainwater to quantify metal(loid) liberation as a function of time. Leachate pH increased to ca. 12.5 within the first hour. Some metal(loid)s quickly reached the maximum measured concentration and consistently decreased in concentration with time such as Ba, Pb, and Zn, while other metal(loid)s increased in concentration with increased reaction time (e.g., Al, V, and Cr). Leaching behavior of between early stage coal ash and fly ash may be controlled by total initial concentrations present in the two ashes, differences in particle size, dissolution and precipitation reactions, and heterogeneity of metal(loid) distribution within the particles. Early stage coal ash and fly ash were also reacted with reconstituted dissolved organic matter solutions to simulate possible environmental interactions. It was found that for some elements (e.g., Ca), dissolved organic matter did not affect the mobility. Other metal(loid) mobilities were affected by the presence of dissolved organic matter, such as that of Sb, As, Zn, Se, Mo, and V. Some metal(loid) concentrations decreased while others increased with increasing dissolved organic carbon concentrations. Through these experiments, we have obtained a quantitative understanding of the kinetic controls of metal(loid) release from coal ash leaching with various aqueous media. Results from these experiments can help to improve storage and remediation processes for coal combustion products in an effort to protect human and the ecosystem health.UAF Undergraduate Research and Scholarly Activity, Biomedical Learning and Student Training, The IDeA Network of Biomedical Research ExcellenceChapter 1: Introduction -- 1.1 Coal combustion products -- 1.2 Environmental impacts of accidental coal combustion product releases -- 1.3 Toxicity characteristic leaching procedure and synthetic precipitation leaching procedure -- 1.4 Previous coal combustion product leaching studies -- 1.5 Metal(loid)-organic matter interactions -- 1.6 This study. Chapter 2: Site description -- 2.1 Travelling grate combustion. Chapter 3: Methods -- 3.1 Sample collection, preparation, and preservation -- 3.1.1 Dissolved organic matter collection, isolation, and storage -- 3.2 Chemicals and reagents -- 3.3 Wavelength dispersive X-ray fluorescence and multi-acid digestion -- 3.4 Brunauer-Emmett-Teller surface area analysis -- 3.5 Environmental scanning electron microscopy -- 3.6 Solid-state 13C nuclear magnetic resonance -- 3.7 Fly ash and early stage coal ash leaching -- 3.8 Synthetic precipitation leaching procedure -- 3.9 Physiological based extraction tests -- 3.10 Elemental analysis of aqueous samples -- 3.11 Statistical analysis -- 3.12 Coal combustion product-dissolved organic matter interactions -- 3.13 Geochemical modeling. Chapter 4: Results -- 4.1 Physiochemical properties -- 4.1.1 Elemental composition -- 4.1.2 Particle morphology -- 4.1.3 Organic composition -- 4.2 Synthetic precipitation leaching procedure -- 4.3 Leaching experiments -- 4.3.1 pH trends with time -- 4.3.2 Calcium leaching trends -- 4.3.3 Barium leaching trends -- 4.3.4 Aluminum leaching trends -- 4.3.5 Iron leaching trends -- 4.3.6 Lead leaching trends -- 4.3.7 Vanadium leaching trends -- 4.3.8 Molybdenum leaching trends -- 4.3.9 Chromium leaching trends -- 4.3.10 Copper leaching trends -- 4.3.11 Zinc leaching trends -- 4.3.12 Selenium leaching trends -- 4.3.13 Manganese leaching trends -- 4.3.14 Antimony leaching trends -- 4.3.15 Cobalt leaching trends -- 4.3.16 Arsenic leaching trends -- 4.3.17 Tellurium leaching trends -- 4.3.18 Bismuth leaching trends -- 4.4 Initial coal combustion product-dissolved organic matter leaching observations -- 4.4.1 Calcium-dissolved organic matter leaching -- 4.4.2 Iron-dissolved organic matter leaching -- 4.4.3 Vanadium-dissolved organic matter leaching -- 4.4.4 Molybdenum-dissolved organic matter leaching -- 4.4.5 Cobalt-dissolved organic matter leaching -- 4.4.6 Zinc-dissolved organic matter leaching -- 4.4.7 Selenium-dissolved organic matter leaching -- 4.4.8 Manganese-dissolved organic matter leaching -- 4.4.9 Antimony-dissolved organic matter leaching -- 4.4.10 Arsenic-dissolved organic matter leaching -- 4.4.11 Tellurium-dissolved organic matter leaching -- 4.5 Coal combustion product metal(loid) bioaccessibility -- 4.5.1 Chromium bioaccessibility -- 4.5.2 Arsenic bioaccessibility -- 4.5.3 Selenium bioaccessibility -- 4.5.4 Antimony bioaccessibility -- 4.5.5 Lead bioaccessibility. Chapter 5: Discussion -- 5.1 Physical and chemical characteristics of fly ash and early stage coal ash -- 5.1.1 Carbon -- 5.1.2 Major elements -- 5.1.3 Solid phase equilibrium modeling of major elements -- 5.1.4 Minor and trace elements -- 5.1.5 Solid phase equilibrium modeling of minor and trace elements -- 5.2 Competing controlling processes -- 5.2.1 pH controls -- 5.2.2 Total initial concentration -- 5.2.3 Dissolution reactions -- 5.2.4 Higher early stage coal ash leached concentrations -- 5.2.5 Particle size -- 5.2.6 Possible equilibrium -- 5.2.7 Other metal(loid) trends -- 5.3 Synthetic precipitation leaching procedure and other leaching comparisons -- 5.4 Dissolved organic matter leaching trends -- 5.4.1 Dissolved organic carbon independent metal(loid) mobility -- 5.4.2 Dissolved organic carbon dependent metal(loid) mobility -- 5.5 Unreacted coal combustion product metal(loid) bioaccessibility -- 5.5.1 Reacted early stage coal ash metal(loid) bioaccessibility. Chapter 6: Conclusions -- References

Testing the proposed link between cosmic rays and cloud cover

A decrease in the globally averaged low level cloud cover, deduced from the ISCCP infra red data, as the cosmic ray intensity decreased during the solar cycle 22 was observed by two groups. The groups went on to hypothesise that the decrease in ionization due to cosmic rays causes the decrease in cloud cover, thereby explaining a large part of the presently observed global warming. We have examined this hypothesis to look for evidence to corroborate it. None has been found and so our conclusions are to doubt it. From the absence of corroborative evidence, we estimate that less than 23%, at the 95% confidence level, of the 11-year cycle change in the globally averaged cloud cover observed in solar cycle 22 is due to the change in the rate of ionization from the solar modulation of cosmic rays

Dissecting the knee - Air shower measurements with KASCADE

Recent results of the KASCADE air shower experiment are presented in order to shed some light on the astrophysics of cosmic rays in the region of the knee in the energy spectrum. The results include investigations of high-energy interactions in the atmosphere, the analysis of the arrival directions of cosmic rays, the determination of the mean logarithmic mass, and the unfolding of energy spectra for elemental groups

KASCADE: Astrophysical results and tests of hadronic interaction models

KASCADE is a multi-detector setup to get redundant information on single air shower basis. The information is used to perform multiparameter analyses to solve the threefold problem of the reconstruction of (i)the unknown primary energy, (ii) the primary mass, and (iii) to quantify the characteristics of the hadronic interactions in the air-shower development. In this talk recent results of the KASCADE data analyses are summarized concerning cosmic ray anisotropy studies, determination of flux spectra for different primary mass groups, and approaches to test hadronic interaction models. Neither large scale anisotropies nor point sources were found in the KASCADE data set. The energy spectra of the light element groups result in a knee-like bending and a steepening above the knee. The topology of the individual knee positions shows a dependency on the primary particle. Though no hadronic interaction model is fully able to describe the multi-parameter data of KASCADE consistently, the more recent models or improved versions of older models reproduce the data better than few years ago.Comment: to appear in Nucl. Phys. B (Proc. Suppl.), Proc. of the XIII ISVHECRI, Pylos 2004 - with a better quality of the figure

Energy Spectra of Elemental Groups of Cosmic Rays: Update on the KASCADE Unfolding Analysis

The KASCADE experiment measures extensive air showers induced by cosmic rays in the energy range around the so-called knee. The data of KASCADE have been used in a composition analysis showing the knee at 3-5 PeV to be caused by a steepening in the light-element spectra. Since the applied unfolding analysis depends crucially on simulations of air showers, different high energy hadronic interaction models (QGSJet and SIBYLL) were used. The results have shown a strong dependence of the relative abundance of the individual mass groups on the underlying model. In this update of the analysis we apply the unfolding method with a different low energy interaction model (FLUKA instead of GHEISHA) in the simulations. While the resulting individual mass group spectra do not change significantly, the overall description of the measured data improves by using the FLUKA model. In addition data in a larger range of zenith angle are analysed. The new results are completely consistent, i.e. there is no hint to any severe problem in applying the unfolding analysis method to KASCADE data.Comment: accepted for publication in Astroparticle Physic

Results from the KASCADE, KASCADE-Grande, and LOPES experiments

The origin of high-energy cosmic rays in the energy range from 10^14 to 10^18 eV is explored with the KASCADE and KASCADE-Grande experiments. Radio signals from air showers are measured with the LOPES experiment. An overview on results is given.Comment: Talk at The ninth International Conference on Topics in Astroparticle and Underground Physics, TAUP 2005, Zaragoza, September 10-14, 200

First results of the air shower experiment KASCADE

The main goals of the KASCADE (KArlsruhe Shower Core and Array DEtector) experiment are the determination of the energy spectrum and elemental composition of the charged cosmic rays in the energy range around the knee at ca. 5 PeV. Due to the large number of measured observables per single shower a variety of different approaches are applied to the data, preferably on an event-by-event basis. First results are presented and the influence of the high-energy interaction models underlying the analyses is discussed.Comment: 3 pages, 3 figures included, to appear in the TAUP 99 Proceedings, Nucl. Phys. B (Proc. Suppl.), ed. by M. Froissart, J. Dumarchez and D. Vignau