52 research outputs found
Dataset to accompany "Deposition of brown carbon onto snow: changes of snow optical and radiative properties" by Beres et al., 2020
No full textThis dataset, organized in an Excel spreadsheet, accompanies:
Beres, N. D., Sengupta, D., Samburova, V., Khlystov, A. Y., and Moosmüller, H.: Deposition of brown carbon onto snow: changes in snow optical and radiative properties, Atmos. Chem. Phys., 20, 6095–6114, https://doi.org/10.5194/acp-20-6095-2020, 2020.
Each tab of the spreadsheet represents data presented in Tables and Figures of the manuscript, which allows for the replication of the figure or for use in calculations presented throughout the manuscript.
Any questions or comments should be forwarded to the corresponding author
Ambient Observations of Aerosols, Novel Aerosol Structures, And Their Engineering Applications
No full textThe role of atmospheric aerosols remains a crucial issue in understanding and mitigating climate change in our world today. These particles influence the Earth by altering the Earth's delicate radiation balance, human health, and visibility. In particular, black carbon particulate matter remains the key driver in positive radiative forcing (i.e., warming) due to aerosols. Produced from the incomplete combustion of hydrocarbons, these compounds can be found in many different forms around the globe. This thesis provides an overview of three research topics: (1) the ambient characterization of aerosols in the Northern Indian Ocean, measurement techniques used, and how these aerosols influence local, regional, and global climate; (2) the exploration of novel soot superaggregate particles collected in the Northern Indian Ocean and around the globe and how the properties of these particles relate to human health and climate forcing; and (3) how aerogelated soot can be produced in a novel, one-step method utilizing an inverted flame reactor and how this material could be used in industrial settings
Deposition of light-absorbing aerosols on snow: method development and changes to snow optical and radiative properties
No full textSnow and ice cover a significant portion of the Earth’s surface, and not only provide fresh water to billions of people, but also contribute to the Earth’s energy balance through a high surface albedo, reflecting most incident solar radiation back towards space. The surface albedo and reflected radiation can be greatly reduced by small amounts of light-absorbing impurities within the snowpack, such as black carbon (BC), mineral dust aerosol, and microbial growth. A wealth of observations and modelling of snow optical and radiative properties recognize BC and mineral dust aerosol as dominating the reduction of snow albedo after deposition, but growing research into atmospheric, light-absorbing organic carbon (OC) aerosol, known as brown carbon (BrC), encourages a greater understanding of the impacts of this impurity in the snowpack. Little is known about how BrC deposition onto snow surfaces affects the spectral snow albedo and what radiative forcing results from BrC deposition. This is of special importance for areas of the Arctic where wildfires burn fuels, such as peat, that emit BrC aerosol in close proximity to snow and ice. The goal of this dissertation is to explore this snow-BrC aerosol relationship. A simple apparatus was developed to generate and deposit aerosols onto a snow surface to study aerosol deposition and its effect on snow albedo experimentally and to compare with theory. This portable apparatus was used to deposit combustion and mineral dust aerosol �" including black carbon, brown carbon, and hematite �" in situ onto snow surfaces. Aerosols were generated and continuously transported into a deposition chamber placed on the snow surface, where there were evenly deposited, thereby modifying the snowpack’s optical and radiative properties. Field operation of this apparatus was demonstrated and changes in snow surface reflectivity were monitored by measuring the spectral directional reflectance of the deposited areas and of adjacent natural snowpack. The apparatus was further used for the artificial deposition of emissions from Alaskan peat combustion onto a natural snow surface. This combustion occurs mostly in the smoldering phase, emitting mainly BrC aerosol designated by strongly enhanced light absorption at short-visible and ultraviolet wavelengths. This wavelength dependence was validated by observing a strong reduction in measured spectral snow albedo after deposition, mainly at these same wavelength regions predicted from previous studies of the optical properties of these aerosols generated under similar conditions of combustion. The imaginary refractive index spectrum of deposited BrC was derived from UV-vis absorption spectra of melted snow samples and total organic carbon (TOC) concentrations in the snow before and after deposition, which agreed well with results of other investigations into the refractive indices of smoldering peat combustion emissions. The optical properties of deposited BrC aerosol were calculated with Mie theory and incorporated into a snow/impurity radiative transfer model calculating surface albedo spectra of snow with BrC impurities. Measured and modelled surface albedo spectra were shown to be in good agreement �" to within approximately 5% �" across the UV-visible wavelength region. Finally, the amount of energy absorbed by the snowpack due to the presence of impurities before deposition to be about 40 W/m2. After depositing BrC, the instantaneous radiative forcing was increased by over 10 W/m2, yielding a direct estimate of the mass weighted radiative forcing, or forcing efficiency, for the conditions during the experiment of 1.2 ± 0.2 W/m2 per ppm of deposited BrC. In addition to estimating the impact from the artificial deposition of BrC, the snow surface spectral albedo, TOC concentration and absorption spectra of melted snow at three depths, and instantaneous radiative forcing was measured for the natural snowpack at the field site in the Sierra Nevada; these results can provide this much needed information for a spatial understanding of snow and impurity properties both locally and worldwide.In summary, this work has developed and characterized a novel apparatus for artificial deposition of aerosols onto snow and has used it, together with other measurements and radiative transfer theory, to determine the changes to snow optical properties and radiative forcing due to the deposition of BrC aerosol produced from smoldering peat combustion
Apparatus for dry deposition of aerosols on snow
No full textDeposition of light-absorbing aerosol on snow can drastically change the albedo of the snow surface and the energy balance of the snowpack. To study these important effects experimentally and to compare them with theory, it is desirable to have an apparatus for such deposition experiments. Here, we describe a simple apparatus to generate and evenly deposit light-absorbing aerosols onto a flat snow surface. Aerosols are produced (combustion aerosols) or entrained (mineral dust aerosols) and continuously transported into a deposition chamber placed on the snow surface where they deposit onto and into the snowpack, thereby modifying its surface reflectance and albedo. We demonstrate field operation of this apparatus by generating black and brown carbon combustion aerosols and entraining hematite mineral dust aerosol and depositing them on the snowpack. Changes in spectral snow reflectance are demonstrated qualitatively through pictures of snow surfaces after aerosol deposition and quantitatively by measuring hemispherical-conical reflectance spectra for the deposited areas and for adjacent snowpack in its natural state. Additional potential applications for this apparatus are mentioned and briefly discussed
Snow Surface Albedo Sensitivity to Black Carbon: Radiative Transfer Modelling
No full textThe broadband surface albedo of snow can greatly be reduced by the deposition of light-absorbing impurities, such as black carbon on or near its surface. Such a reduction increases the absorption of solar radiation and may initiate or accelerate snowmelt and snow albedo feedback. Coincident measurements of both black carbon concentration and broadband snow albedo may be difficult to obtain in field studies; however, using the relationship developed in this simple model sensitivity study, black carbon mass densities deposited can be estimated from changes in measured broadband snow albedo, and vice versa. Here, the relationship between the areal mass density of black carbon found near the snow surface to the amount of albedo reduction was investigated using the popular snow radiative transfer model Snow, Ice, and Aerosol Radiation (SNICAR). We found this relationship to be linear for realistic amounts of black carbon mass concentrations, such as those found in snow at remote locations. We applied this relationship to measurements of broadband albedo in the Chilean Andes to estimate how vehicular emissions contributed to black carbon (BC) deposition that was previously unquantified
Soot Superaggregates from Flaming Wildfires and Their Direct Radiative Forcing
No full textWildfires contribute significantly to global soot emissions, yet their aerosol formation mechanisms and resulting particle properties are poorly understood and parameterized in climate models. The conventional view holds that soot is formed via the cluster-dilute aggregation mechanism in wildfires and emitted as aggregates with fractal dimension D(sub f) approximately equals 1.8 mobility diameter D(sub m) (is) less than or equal to 1 micron, and aerodynamic diameter D(sub a) (is) less than or equal to 300 nm. Here we report the ubiquitous presence of soot superaggregates (SAs) in the outflow from a major wildfire in India. SAs are porous, low-density aggregates of cluster-dilute aggregates with characteristic D(sub f) approximately equals 2.6,D(sub m) (is) greater than 1 micron, and D(sub a) is less than or equal to 300 nm that form via the cluster-dense aggregation mechanism.We present additional observations of soot SAs in wildfire smoke-laden air masses over Northern California, New Mexico, and Mexico City. We estimate that SAs contribute, per unit optical depth, up to 35% less atmospheric warming than freshly-emitted (D(sub f) approximately equals 1.8) aggregates, and approximately equals 90% more warming than the volume-equivalent spherical soot particles simulated in climate models
Unintended Consequences of COVID-19 on Pediatric Falls From Windows: A Multicenter Study
No full textINTRODUCTION: In attempts to quell the spread of COVID-19, shelter-in-place orders were employed in most states. Increased time at home, in combination with parents potentially balancing childcare and work-from-home duties, may have had unintended consequences on pediatric falls from windows. We aimed to investigate rates of falls from windows among children during the first 6 mo of the COVID-19 pandemic. METHODS: Patients <18 y old admitted to three pediatric trauma centers (two - level 1, one - level 2) between 3/19/20 and 9/19/20 (COVID-era) were compared to a pre-COVID cohort (3/19/19 to 9/19/19). The primary outcome was the rate of falls from windows. Secondary outcomes included injury severity score (ISS), injuries sustained, and mortality. RESULTS: Of 1011 total COVID-era pediatric trauma patients, 36 (3.6%) sustained falls from windows compared to 23 of 1108 (2.1%) pre-COVID era patients (OR 1.7, P = 0.05). The median ISS was seven pre-COVID versus four COVID-era (P = 0.43). The most common injuries sustained were skull fractures (30.5%), extremity injuries (30.5%), and intracranial hemorrhage (23.7%). One-fifth of patients underwent surgery (21.7% pre-COVID versus 19.4% COVID-era, P = 1.0). There was one mortality in the COVID-era cohort and none in the pre-COVID cohort (P = 1.0). CONCLUSIONS: Despite overall fewer trauma admissions during the first 6 mo of the COVID-19 pandemic, the rate of falls from windows nearly doubled compared to the prior year, with substantial associated morbidity. These findings suggest a potential unintended consequence of shelter-in-place orders and support increased education on home safety and increased support for parents potentially juggling multiple responsibilities in the home
Redcliff hard red spring wheat
No full textRedcliff hard red spring wheat was developed at the University of Alberta using a modified bulk breeding method. In three years of evaluation in the Parkland Cooperative test from 2018 to 2020, Redcliff produced 7.3% more grain and matured 1.9 days earlier than the highest yielding check Carberry. Redcliff had 3.9 cm taller plants than Carberry but shorter than the other checks and displayed good lodging tolerance. The test weight of Redcliff was slightly higher than Carberry and Parata but lower than Glenn. The grain weight of Redcliff was higher than Parata and similar to the other checks. Grain protein content was within the range of the checks. Redcliff was rated ‘Resistant’ to the prevalent races of stem rust, ‘Resistant’ to ‘Moderately Resistant’ to Fusarium head blight, ‘Intermediate’ to leaf and stripe rusts, whereas ‘Moderately Susceptible’ to common bunt. Three years of end-use quality evaluation have indicated that Redcliff is acceptable for the CWRS wheat market class, with improvements in flour yield.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Effects of reduced pesticide use on winter wheat production in the Canadian Prairies
No full textWinter wheat (Triticum aestivum L.) is a highly competitive crop with the potential to enhance on-farm revenue and reduce reliance on crop protection inputs. The adoption of winter wheat in the Canadian Prairies has varied significantly over recent decades; however, improved weed and disease management practices could facilitate stability of hectares cultivated. To assess current and alternative pesticide management practices, we conducted a study across 15 site-years at four locations over four years (2018-2022). Experimental treatments included pre-plant weed management (glyphosate vs. glyphosate mixed with pyroxasulfone+carfentrazone-ethyl), in-crop weed management (no in-crop herbicide vs. fall-applied 2,4-D vs. fall-applied 2,4-D+spring-applied site-year-specific herbicides) and in-crop fungicide management (no in-crop fungicide vs. one prothioconazole+tebuconazole application at ZGS60 vs. two prothioconazole+tebuconazole applications at ZGS32 and ZGS60). Pre-plant glyphosate alone and glyphosate tank-mixed with pyroxasulfone+carfentrazone-ethyl exhibited comparable effects on grain yield, quality parameters, and agronomic characteristics. In-crop weed management had no significant influence on these factors compared to the no in-crop herbicide control, suggesting that in-crop herbicide applications are unnecessary due to the high competitiveness of winter wheat against weeds. However, disease mitigation was prudent as single and double application of fungicide increased grain yield while maintaining grain protein concentration levels. A high-yielding, stable system for optimal grain yield typically required pre-plant weed management coupled with two fungicide applications. These observations confirm herbicide inputs can be reduced in a winter wheat cropping system but disease pressure requires careful cultivar selection with an emphasis on disease resistance as multiple applications of fungicides were needed to optimize grain yield.The presentation of the authors' names and (or) special characters in the title of the pdf file of the accepted manuscript may differ slightly from what is displayed on the item page. The information in the pdf file of the accepted manuscript reflects the original submission by the author
Trapping and aerogelation of nanoparticles in negative gravity hydrocarbon flames
No full textWe report the experimental realization of continuous carbon aerogel production using a flame aerosol reactor by operating it in negative gravity (−g; up-side-down configuration). Buoyancy opposes the fuel and air flow forces in −g, which eliminates convectional outflow of nanoparticles from the flame and traps them in a distinctive non-tipping, flicker-free, cylindrical flame body, where they grow to millimeter-size aerogel particles and gravitationally fall out. Computational fluid dynamics simulations show that a closed-loop recirculation zone is set up in −g flames, which reduces the time to gel for nanoparticles by ≈10[superscript 6] s, compared to positive gravity (upward rising) flames. Our results open up new possibilities of one-step gas-phase synthesis of a wide variety of aerogels on an industrial scale
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