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ABSTRACT It is known that decreasing the hydrogenation temperature results in a loss of hydrogen capacity of Mg powders. Based on the model that hydrogen capacity is reached when hydride colonies/crystals formed on the surface of... more
ABSTRACT It is known that decreasing the hydrogenation temperature results in a loss of hydrogen capacity of Mg powders. Based on the model that hydrogen capacity is reached when hydride colonies/crystals formed on the surface of particles impinge on each other and form a continuous layer, it is elucidated, through a two-step hydrogenation experiment and detailed microstructural analysis, that the reduced hydrogen capacity at low temperatures is associated with an increase in the hydride nucleation rate.
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... CONTRIBUTED COMMENTS BY LISA M. COREY, GRETCHEN M. BRUCE, AND DR. ... 15. Frampton, MW; Utell, MJ; Zareba, W.; Oberdörster, G.; Cox, C.; Huang, LS; Morrow, PE; Lee, FE; Chalupa, D.; Frasier, LM; Speers, DM; Stewart, J. Effects of... more
... CONTRIBUTED COMMENTS BY LISA M. COREY, GRETCHEN M. BRUCE, AND DR. ... 15. Frampton, MW; Utell, MJ; Zareba, W.; Oberdörster, G.; Cox, C.; Huang, LS; Morrow, PE; Lee, FE; Chalupa, D.; Frasier, LM; Speers, DM; Stewart, J. Effects of Exposure to Ultrafine Carbon ...
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ABSTRACT The 35th annual A&WMA Critical Review addresses the broad topic of nanoparticles and the environment. Complementing recent treatments of this topic in the literature, the review offers a broad overview of environmental... more
ABSTRACT The 35th annual A&WMA Critical Review addresses the broad topic of nanoparticles and the environment. Complementing recent treatments of this topic in the literature, the review offers a broad overview of environmental origins, consequences, and applications of nanoparticles, or particles with diameters in the range of 1 to 50 or 100 nanometers. The four key elements discussed in the review are (1) sources of nanoparticles, (2) their control, (3) the application of nanoparticles in environmental and energy sectors, and (4) exposure and health effects. 18 refs., 4 figs., 1 tab.
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ABSTRACT A bench-scale system consisting of a high-temperature flow reactor was used to study aerosol formation and growth in a multicomponent system containing lead species. The effect of chlorine on the resultant particle size... more
ABSTRACT A bench-scale system consisting of a high-temperature flow reactor was used to study aerosol formation and growth in a multicomponent system containing lead species. The effect of chlorine on the resultant particle size distribution was studied by varying the chlorine to lead (Cl/Pb) ratio. The particle size was observed to increase as the Cl/Pb ratio increases, Species such as laurionite and lead oxide chloride hydrate were observed at intermediate Cl/Pb ratios for high lead feed rates, revealing the role of hydroxide radicals in the oxidation processes and the occurrence of multicomponent nucleation of miscible lead species. For lower lead feed rates, the number and volume concentrations increased as the Cl/Pb ratio increased; for higher feed rates, they reached a maximum at intermediate Cl/Pb ratios, then decreased upon a further increase of Cl/Pb ratios. Coagulation and condensation characteristic times were also calculated to study the importance of various mechanisms in the system. Condensation was found to be the main mechanism for aerosol growth of lead species. A two-component log-normal model incorporating three previously reported nucleation theories was used to study lead aerosol formation and growth.
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Our career-forward approach to general chemistry laboratory for engineers involves the use of design challenges (DCs), an innovation that employs authentic professional context and practice to transform traditional tasks into... more
Our career-forward approach to general chemistry laboratory for engineers involves the use of design challenges (DCs), an innovation that employs authentic professional context and practice to transform traditional tasks into developmentally appropriate career experiences. These challenges are scaled-down engineering problems related to the US National Academy of Engineering’s Grand Challenges that engage students in collaborative problem solving via the modeling process. With task features aligned with professional engineering practice, DCs are hypothesized to support student motivation for the task as well as for the profession. As an evaluation of our curriculum design process, we use expectancy–value theory to test our hypotheses by investigating the association between students’ task value beliefs and self-confidence with their user experience, gender and URM status. Using stepwise multiple regression analysis, the results reveal that students find value in completing a DC (F(5...
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Research Interests: Mechanical Engineering, Chemical Engineering, Chemistry, Halide, Fuel, and 3 moreAmmonium, Char, and husk
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Research Interests: Engineering, Environmental Science, Environmental Impact Assessment, Air pollution, Public Health, and 15 moreRisk Analysis, Policy making, Environmental Sciences, Natural Gas, global Climate change, Humans, Exposure, Environmental Impact, Diesel Fuel, Fuel Consumption, Exhaust Gas Recirculation, Particulate Matter, Equipment Design, Environment, and Public Policy
Impregnated filters treated with alkali and humectant were first used as collection media to assess occupational exposure to sulfur dioxide (SO2), as outlined in the National Institute for Occupational Safety and Health Method 6004 in... more
Impregnated filters treated with alkali and humectant were first used as collection media to assess occupational exposure to sulfur dioxide (SO2), as outlined in the National Institute for Occupational Safety and Health Method 6004 in 1979. Since then, updated treatment protocols have been proposed with decreased amounts of alkali and glycerol, which claim the same filtering capacity. However, there has been no report on how the collection of SO2 on such impregnated media is influenced by relative humidity (RH). This study investigated the role of glycerol (G) amount on impregnated filters (G2 and G10, referring to 2 and 10% glycerol, respectively) in the collection of SO2 (100 l of 10 ppm at 1 l per minute) under low, medium, and high RHs. The testing results show that RH significantly impacted G2 filters with respect to breakthrough time, capacity, and recovery. At low RH, the 5% breakthrough time was less than 10 min and its recovery was merely 42%; at medium and high RHs, although the recovery was satisfactory, the 5% breakthrough time was still less than 100 min. By contrast, G10 filters illustrated nearly 100% recovery and evaluation by analysis of variance showed no significant effect of RH on recovery. In summary, the current treatment protocol of 2% glycerol leads to a significant underestimation of the exposure to SO2 in a low-RH environment; increasing the glycerol content can be an effective alternative to compensating for the effect of RH.
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Pathways of transmission of coronavirus (COVID-19) disease in the human population are still emerging. However, empirical observations suggest that dense human settlements are the most adversely impacted, corroborating a broad consensus... more
Pathways of transmission of coronavirus (COVID-19) disease in the human population are still emerging. However, empirical observations suggest that dense human settlements are the most adversely impacted, corroborating a broad consensus that human-to-human transmission is a key mechanism for the rapid spread of this disease. Here, using logistic regression techniques, estimates of threshold levels of population density were computed corresponding to the incidence in the human population. Regions with population densities greater than 3000 person per square mile in the United States have about 95% likelihood to get infected with COVID-19. Since case numbers of COVID-19 dynamically changed each day until November 30, 2020, ca. 4% of US counties were at 50% or higher risk of COVID-19 transmission. While threshold on population density is not the sole indicator for predictability of coronavirus in human population, yet it is one of the key variables on understanding and rethinking human...
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Chromated copper arsenate (CCA) treated wood is the popular treated wood found in the wood waste disposal sector. Incineration has been a key disposal pathway for CCA-treated wood waste; however, the potential for emissions of toxic... more
Chromated copper arsenate (CCA) treated wood is the popular treated wood found in the wood waste disposal sector. Incineration has been a key disposal pathway for CCA-treated wood waste; however, the potential for emissions of toxic metals from combustion, and their accumulation and subsequent leaching from ash has raised public concerns. Earlier studies by our group focused on evaluating combinations of CCA chemical with sorbents for their ability to minimize leaching of ash. The objective of this study was to evaluate the ability of sorbents to minimize the leaching of CCA-treated wood and to compare the results to evaluate the influence of the wood matrix on the effectiveness of sorbents to minimize leaching. Experiments were carried out using CCA wood with alkaline earth, alumino-silicate and iron-based sorbents combusted at 700 C and 1100 C. A portion of the residual was leached using the toxicity characteristic leaching procedure (TCLP). ---------------------------------------...
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Chromated copper arsenate (CCA) was the dominant wood preservative used for outdoor wood products to prevent structural decay prior to its phase down starting from 2004. Incineration is one key disposal alternative for CCA-treated wood;... more
Chromated copper arsenate (CCA) was the dominant wood preservative used for outdoor wood products to prevent structural decay prior to its phase down starting from 2004. Incineration is one key disposal alternative for CCA-treated wood; however, it results in volatilization of metals at high temperature and accumulation of metals in ash. The objective of this study was to assess alkaline earth and iron based sorbents for their capability to minimize leaching of metals from the incinerator ash. Experiments were carried out by heating CCA metal spikes combined with sorbents to temperatures of 700, 900 and 1100 o C. The residual ash was analyzed for leaching retention using the toxicity characteristic leaching procedure (TCLP) and speciation by X-ray diffraction (XRD). Results show that alkaline earth sorbents (cement, calcium hydroxide and magnesium hydroxide) were the most promising for reducing the leaching of arsenic from the ash below the 5 mg/L TCLP limit and retaining copper at ...
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Past studies have shown that many alumino-silicate mineral sorbents are effective in controlling heavy metal emission during incineration. The objective of this study was to identify Al-Si based mineral sorbents that can minimize leaching... more
Past studies have shown that many alumino-silicate mineral sorbents are effective in controlling heavy metal emission during incineration. The objective of this study was to identify Al-Si based mineral sorbents that can minimize leaching of heavy metals from the incinerator ash of Chromated Copper Arsenate (CCA-) treated wood. Experiments were carried out using CCA metal spikes combined with Al-Si sorbents, heated to 700 o C, 900 o C and 1100 o C for 30 minutes. The residual ash was leached using the toxicity characteristic leaching procedure (TCLP). X-Ray Diffraction (XRD) analysis was conducted to determine the crystalline speciation of the products. Results showed that low leaching was observed for chromium, below the 5 mg/L TC limit, by alumina and silica at all temperatures, and kaolin at higher temperatures (900 o C and 1100 o C). For copper, all sorbents displayed low leaching values (< 51 mg/l) as compared to the baseline. For arsenic, all sorbents exceeded the TC limit...
Research Interests: Chemistry, Arsenic, Municipal Solid Waste Management, Air pollution, Sorbents, and 15 moreSolid Waste Management, Adsorption, Incineration, Alumina, Copper, Silica, Chromium, Metal, Chromated Copper Arsenate, Silicate, Kaolin, Hazarous Waste Management, Alumino Silicates, Mineral Attapulgite, and Sorbent
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The topic of global warming as a result of increased atmospheric CO2 concentration is arguably the most important environmental issue that the world faces today. It is a global problem that will need to be solved on a global level. The... more
The topic of global warming as a result of increased atmospheric CO2 concentration is arguably the most important environmental issue that the world faces today. It is a global problem that will need to be solved on a global level. The link between anthropogenic emissions of CO2 with increased atmospheric CO2 levels and, in turn, with increased global temperatures has been well established and accepted by the world. International organizations such as the United Nations Framework Convention on Climate Change (UNFCCC) and the Intergovernmental Panel on Climate Change (IPCC) have been formed to address this issue. Three options are being explored to stabilize atmospheric levels of greenhouse gases (GHGs) and global temperatures without severely and negatively impacting standard of living: (1) increasing energy efficiency, (2) switching to less carbon-intensive sources of energy, and (3) carbon sequestration. To be successful, all three options must be used in concert. The third option is the subject of this review. Specifically, this review will cover the capture and geologic sequestration of CO2 generated from large point sources, namely fossil-fuel-fired power gasification plants. Sequestration of CO2 in geological formations is necessary to meet the President&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Global Climate Change Initiative target of an 18% reduction in GHG intensity by 2012. Further, the best strategy to stabilize the atmospheric concentration of CO2 results from a multifaceted approach where sequestration of CO2 into geological formations is combined with increased efficiency in electric power generation and utilization, increased conservation, increased use of lower carbon-intensity fuels, and increased use of nuclear energy and renewables. This review covers the separation and capture of CO2 from both flue gas and fuel gas using wet scrubbing technologies, dry regenerable sorbents, membranes, cryogenics, pressure and temperature swing adsorption, and other advanced concepts. Existing commercial CO2 capture facilities at electric power-generating stations based on the use of monoethanolamine are described, as is the Rectisol process used by Dakota Gasification to separate and capture CO2 from a coal gasifier. Two technologies for storage of the captured CO2 are reviewed--sequestration in deep unmineable coalbeds with concomitant recovery of CH4 and sequestration in deep saline aquifers. Key issues for both of these techniques include estimating the potential storage capacity, the storage integrity, and the physical and chemical processes that are initiated by injecting CO2 underground. Recent studies using computer modeling as well as laboratory and field experimentation are presented here. In addition, several projects have been initiated in which CO2 is injected into a deep coal seam or saline aquifer. The current status of several such projects is discussed. Included is a commercial-scale project in which a million tons of CO2 are injected annually into an aquifer under the North Sea in Norway. The review makes the case that this can all be accomplished safely with off-the-shelf technologies. However, substantial research and development must be performed to reduce the cost, decrease the risks, and increase the safety of sequestration technologies. This review also includes discussion of possible problems related to deep injection of CO2. There are safety concerns that need to be addressed because of the possibilities of leakage to the surface and induced seismic activity. These issues are presented along with a case study of a similar incident in the past. It is clear that monitoring and verification of storage will be a crucial part of all geological sequestration practices so that such problems may be avoided. Available techniques include direct measurement of CO2 and CH4 surface soil fluxes, the use of chemical tracers, and underground 4-D seismic monitoring. Ten new hypotheses were formulated to describe what happens when CO2 is pumped into a coal seam. These hypotheses provide significant insight into the fundamental chemical, physical, and thermodynamic phenomena that occur during coal seam sequestration of CO2.
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The Critical Review of Hoff and Christopher, along with the discussants, provides an important perspective on the interface between satellite measurement science and air quality observations. A top-down picture of the usefulness of... more
The Critical Review of Hoff and Christopher, along with the discussants, provides an important perspective on the interface between satellite measurement science and air quality observations. A top-down picture of the usefulness of satellite observations in terms of air quality regulatory and technical support requirements can be summarized. The air quality requirements are (1) determination of compliance with the ambient air quality standards, (2) inference of human and ecosystem exposure, (3) identification of intra- and intercontinental events relevant to EE, (4) establishment of trends in ambient concentrations relevant to accountability, (5) regulatory and forecast model applications, and (6) extension of fundamental knowledge relevant to air quality. Each of these topics is important to air quality management, and each has detailed technical issues associated with spatial and temporal resolution, accuracy, and precision, etc. In any case, one can summarize the broad capabilities of measurement systems to address these requirements as listed in Table 1. From this rather superficial summary table, investigators should be encouraged to forward increased interaction between the various measurement communities and to facilitate the utility of a comprehensive portfolio of measurements and adjunct analyses for improved air quality applications. The Critical Review has done much to educate air quality scientists on the possibilities for using satellite remote sensing for various purposes. However, space scientists also need a better education on air quality science. Recently published reviews on PM air quality measurements are available that complement the Hoff-Christopher paper on this topic. The need for greater collaboration of air quality and space scientists is evident in an article published in the July issue of the journal. Al-Hamdan et al. provide an interesting and useful analysis of relationships between surface air quality and space-based satellite AOD to estimate human exposure. They obtain mostly urban PM data from EPA&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s Air Quality System (AQS), but they neglect the potentially more useful PM2.5 and chemical speciation data from the nonurban Interagency Monitoring of Protected Visual Environments (IMPROVE) and the Southeastern Aerosol Research and Characterization (SEARCH) networks. They correlate PM2.5 mass with optical depth, although visibility assessments show that light extinction is better represented by a weighted sum of PM2.5 sulfate, nitrate, organic carbon, elemental carbon, and soil dust. Their comparison of hourly measurements with filter measurements does not specify the source of the hourly values as TEOM or BAM. Spatial outliers for ground-level measurements are removed to improve the correlation of PM2.5 with AOD, although these…
Research Interests: Engineering, Environmental Engineering, Environmental Science, Air Quality, Light Scattering, and 15 moreEnvironmental Monitoring, Air pollution, Medicine, Event Detection, Environmental Sciences, Chlorine dioxide, Nitric oxide, Industrial Revolution, Aerosol Optical Depth, Nitrogen Dioxide, Fine Particles, Air Pollutants, Fine Particulate Matter, Air Quality Index, and Optical Phenomena
In this study, two standalone weather-resistant EDS prototypes were tested in the laboratory to investigate the effect of surface charge on dust removal efficiency. Dust was deposited using a sieve deposition method, and a... more
In this study, two standalone weather-resistant EDS prototypes were tested in the laboratory to investigate the effect of surface charge on dust removal efficiency. Dust was deposited using a sieve deposition method, and a micro-photomicrography method was used to quantify the dust removal efficiency of the prototypes at various locations on the EDS surface, after a single activation of the EDS, also known as the single-operation mode. Both "dry clean" and "wet clean" were used to prepare the EDS surface prior to each experimental run. The method of cleaning prior to the experiment affected the dust removal efficiency, apparently because the different cleaning actions led to different conditions of surface charge. Dry clean resulted EDS efficiency than was only 1/3 that of wet clean. Meanwhile, dry clean left more than twice as much negative charge on the EDS surface as wet clean, measured at 6 min after the cleaning action. This laboratory study shows the effect of surface charge on EDS efficiency, and it can be used to explain the location dependence of dust removal efficiency observed in the field study. Further research is needed to better understand the role of surface charge in the performance of EDS and potentially improve the technology.
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Research Interests: Engineering, Environmental Engineering, Materials Engineering, Mechanical Engineering, Chemical Engineering, and 15 moreCivil Engineering, Materials Science, Analytical Chemistry, Organic Chemistry, Mass Spectrometry, Powder technology, Photocatalysis, Physical sciences, Magnetic separation, Methylene Blue, CHEMICAL SCIENCES, Food Sciences, Aqueous Solution, Nanoscience and nanotechnology, and Food control
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The complexity of transmission of COVID-19 in the human population cannot be overstated. Although major transmission routes of COVID-19 remain as human-to-human interactions, understanding the possible role of climatic and weather... more
The complexity of transmission of COVID-19 in the human population cannot be overstated. Although major transmission routes of COVID-19 remain as human-to-human interactions, understanding the possible role of climatic and weather processes in accelerating such interactions is still a challenge. The majority of studies on the transmission of this disease have suggested a positive association between a decrease in ambient air temperature and an increase in human cases. Using data from 19 early epicenters, we show that the relationship between the incidence of COVID-19 and temperature is a complex function of prevailing climatic conditions influencing human behavior that govern virus transmission dynamics. We note that under a dry (low-moisture) environment, notably at dew point temperatures below 0°C, the incidence of the disease was highest. Prevalence of the virus in the human population, when ambient air temperatures were higher than 24°C or lower than 17°C, was hypothesized to be...
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State-of-the-art bioaerosol samplers have poor collection efficiencies for ultrafine virus aerosols. This work evaluated the performance of a novel Growth Tube Collector (GTC), which utilizes laminar-flow water-based condensation to... more
State-of-the-art bioaerosol samplers have poor collection efficiencies for ultrafine virus aerosols. This work evaluated the performance of a novel Growth Tube Collector (GTC), which utilizes laminar-flow water-based condensation to facilitate particle growth, for the collection of airborne MS2 viruses. Fine aerosols (<500 nm) containing MS2 coliphage were generated from a Collison nebulizer, conditioned by a dilution dryer and collected by a GTC and a BioSampler. The GTC effectively condensed water vapor onto the virus particles, creating droplets 2-5 μm in diameter, which facilitated collection. Comparison of particle counts upstream and downstream revealed that the GTC collected >93% of the inlet virus particles, whereas the BioSampler's efficiency was about 10%. Viable counts of the GTC-collected viruses were also one order of magnitude higher than those of the BioSampler (p = 0.003). The efficiency of the GTC for the viable collection of MS2 viruses exceeds that of in...
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Welding stainless steel generates hazardous air pollutants (HAPs). Two technologies were developed to reduce these HAPs. The first, tetramethylsilane is added to the welding shielding gas, and welding proceeds as normal. Reactive oxygen... more
Welding stainless steel generates hazardous air pollutants (HAPs). Two technologies were developed to reduce these HAPs. The first, tetramethylsilane is added to the welding shielding gas, and welding proceeds as normal. Reactive oxygen species are consumed, and the resulting metal fume particles are encapsulated. In the second technique, new chromium-free welding consumables are introduced nearly eliminating Cr(VI) in the welding fume.