Smoke Plume Research Articles

Photooxidation potential of fine particles from desulfurization flue gas aerosol

In China, desulfurization flue gas from coal-fired power plants (CFPPs) has been the focus of research for many years. In this study, for the first time, we simulated the emission process of flue gas and prepared photocatalysts by deposition. An innovative photocatalytic perspective was applied to study the composition, photocatalytic properties, hygroscopicity, and redox properties of the fine particles from flue gas aerosols. The characterization results of XRD, HRTEM, and XPS of freeze-dried desulfurized flue gas samples indicated that aerosol condensation occurred during the smoke plume transportation process, resulting in the formation of well-crystallized fine particles primarily consisting of soluble salts and metal oxides. The UV–vis and ESR results confirmed that desulfurized flue gas has UV light utilization and photocatalytic potential for producing oxidation groups such as hydroxyl radicals and superoxide radicals in light. The subsequent photocatalyst experiments revealed an 85.4 % reduction of 7 ppm isoprene in 30 min; ozone production (373 μg/m3) was observed under more complicated conditions (NO2 = 80 ppb, VOCs = 7 ppm). As a result of the study, a new research approach was proposed for exploring the photoactive potential of flue gas aerosol produced by CFPPs, as well as its impact on the concentration of VOCs and ozone. The finding provided a new possible pathway for desulfurization flue gas emissions and a reference for futureresearch on the observation and control of atmospheric pollution.

The extreme forest fires in California/Oregon in 2020: Aerosol optical and physical properties and comparisons of aged versus fresh smoke

Wildfire activity in the western United States during August to October 2020 was exceptional in terms of the fire severity and area burned. Extremely dry biomass fuels from near historic multi-year drought conditions were further exacerbated with very hot and dry conditions in 2020. These conditions when coupled with strong offshore flow allowed many ignitions to grow into extremely large and severe wildfires. Long-term monitoring at a few AERONET sites in California showed that the number of days with high Aerosol Optical Depth at 440 nm (AOD440>1) in 2020 was greater than any other year going back to the beginning of the data records in 2002. A wide range of fine mode particle volume median radii were retrieved from AERONET data over the course of these fires suggesting significant variability in combustion conditions and aging processes. Additionally, the fine mode radii in some of these smoke plumes in 2020 were very large especially at high AOD (∼0.22–0.32 μm volume median radius), likely due to both coagulation and condensation occurring during aging at very high particulate concentrations. The largest fine mode particle radii combined with narrow distributions resulted in some very rare AOD spectra showing peak AOD at 500 nm and decreasing to lower AOD at both shorter and longer wavelengths. The most extreme retrieved size distributions and associated measured AOD spectra were principally observed in long-distance transported smoke plumes from these western United States fires at sites in Colorado, Maryland and Virginia, possibly due to further aging during transport. Additionally, strong absorption was sometimes observed at short wavelengths with much lower single scattering albedo at 440 nm compared to 675 nm in some plumes consistent with significant brown carbon (BrC) and/or coated black carbon (BC) absorption in biomass burning particles. This strong spectral absorption signature observed at some California sites and dates remained similarly strong in some smoke plumes observed at some east coast sites in Maryland and Virginia, thereby suggesting that the lifetime of these particular BrC and/or coated BC absorbing species was greater than 5 days.

Automatic early detection of wildfire smoke with visible-light cameras and EfficientDet

The ability of EfficientDet, a framework developed in 2019 for object detection, to automatically detect smoke plumes at a distance of several kilometers is demonstrated. Recent articles have raised concerns about the effectiveness of EfficientDet in fire detection applications, with over 40% of false positives reported. The proposed EfficientDet model achieved a true detection rate of 80.4% and a false-positive rate of 1.13% on a testing set. The data set used in this study, which includes 14,125 smoke and 21,203 non-smoke images, is one of the largest, or even the largest, of its kind reported in the literature for images containing smoke plumes. Our results surpass those of a previous study that used the same data set and are more reliable and realistic than those reported by others, which may seem better, but were calculated using smaller and less representative data sets.

Multiwavelength fluorescence lidar observations of smoke plumes

Abstract. A five-channel fluorescence lidar was developed for the study of atmospheric aerosol. The fluorescence spectrum induced by 355 nm laser emission is analyzed in five spectral intervals using interference filters. Central wavelengths and the widths of these five interference filters are, respectively, as follows: 438 and 29, 472 and 32, 513 and 29, 560 and 40, and 614 and 54 nm. The relative calibration of these channels has been performed using a tungsten–halogen lamp with a color temperature of 2800 K. This new lidar system was operated during summer–autumn 2022, when strong forest fires occurred in the Moscow region and generated a series of smoke plumes analyzed in this study. Our results demonstrate that, for urban aerosol, the maximal fluorescence backscattering is observed in a 472 nm channel. For the smoke, the maximum is shifted toward longer wavelengths, and the fluorescence backscattering coefficients in 472, 513 and 560 nm channels have comparable values. Thus, from the analysis of the ratios of fluorescence backscattering in available channels, we show that it is possible to identify smoke layers. The particle classification based on single-channel fluorescence capacity (ratio of the fluorescence backscattering to the elastic one) has limitations at high relative humidity (RH). The fluorescence capacity indeed decreases when water uptake of particles enhances the elastic scattering. However, the spectral variation of fluorescence backscattering does not exhibit any dependence on RH and can be therefore applied to aerosol identification.

Ground solar absorption observations of total column CO, CO2, CH4, and aerosol optical depth from California's Sequoia Lightning Complex Fire: emission factors and modified combustion efficiency at regional scales

Abstract. With global wildfires becoming more widespread and severe, tracking their emissions of greenhouse gases and air pollutants is becoming increasingly important. Wildfire emissions have primarily been characterized by in situ laboratory and field observations at fine scales. While this approach captures the mechanisms relating emissions to combustion phase and fuel properties, their evaluation on regional-scale plumes has been limited. In this study, we report remote observations of total column trace gases and aerosols during the 2020 wildfire season from smoke plumes in the Sierra Nevada of California with an EM27/SUN solar Fourier transform infrared (FTIR) spectrometer. We derive total column aerosol optical depth (AOD), emission factors (EFs) and modified combustion efficiency (MCE) for these fires and evaluate relationships between them, based on combustion phase at regional scales. We demonstrate that the EM27/SUN effectively detects changes in CO, CO2, and CH4 in the atmospheric column at ∼10 km horizontal scales that are attributed to wildfire emissions. These observations are used to derive total column EFCO of 120.5±12.2 and EFCH4 of 4.3±0.8 for a regional smoke plume event in mixed combustion phases. These values are consistent with in situ relationships measured in similar temperate coniferous forest wildfires. FTIR-derived AOD was compared to a nearby AERONET (AErosol RObotic NETwork) station and observed ratios of XCO to AOD were consistent with those previously observed from satellites. We also show that co-located XCO observations from the TROPOspheric Monitoring Instrument (TROPOMI) satellite-based instrument are 9.7±1.3 % higher than our EM27/SUN observations during the wildfire period. Finally, we put wildfire CH4 emissions in context of the California state CH4 budget and estimate that 213.7±49.8 Gg CH4 were emitted by large wildfires in California during 2020, about 13.7 % of the total state CH4 emissions in 2020. Our work demonstrates a novel application of the ground-based EM27/SUN solar spectrometers in wildfire monitoring by integrating regional-scale measurements of trace gases and aerosols from smoke plumes.

Retrieving 3D distributions of atmospheric particles using Atmospheric Tomography with 3D Radiative Transfer – Part 1: Model description and Jacobian calculation

Abstract. Our global understanding of clouds and aerosols relies on the remote sensing of their optical, microphysical, and macrophysical properties using, in part, scattered solar radiation. These retrievals assume that clouds and aerosols form plane-parallel, homogeneous layers and utilize 1D radiative transfer (RT) models, limiting the detail that can be retrieved about the 3D variability in cloud and aerosol fields and inducing biases in the retrieved properties for highly heterogeneous structures such as cumulus clouds and smoke plumes. To overcome these limitations, we introduce and validate an algorithm for retrieving the 3D optical or microphysical properties of atmospheric particles using multi-angle, multi-pixel radiances and a 3D RT model. The retrieval software, which we have made publicly available, is called Atmospheric Tomography with 3D Radiative Transfer (AT3D). It uses an iterative, local optimization technique to solve a generalized least squares problem and thereby find a best-fitting atmospheric state. The iterative retrieval uses a fast, approximate Jacobian calculation, which we have extended from Levis et al. (2020) to accommodate open and periodic horizontal boundary conditions (BCs) and an improved treatment of non-black surfaces. We validated the accuracy of the approximate Jacobian calculation for derivatives with respect to both the 3D volume extinction coefficient and the parameters controlling the open horizontal boundary conditions across media with a range of optical depths and single-scattering properties and find that it is highly accurate for a majority of cloud and aerosol fields over oceanic surfaces. Relative root mean square errors in the approximate Jacobian for a 3D volume extinction coefficient in media with cloud-like single-scattering properties increase from 2 % to 12 % as the maximum optical depths (MODs) of the medium increase from 0.2 to 100.0 over surfaces with Lambertian albedos <0.2. Over surfaces with albedos of 0.7, these errors increase to 20 %. Errors in the approximate Jacobian for the optimization of open horizontal boundary conditions exceed 50 %, unless the plane-parallel media providing the boundary conditions are optically very thin (∼0.1). We use the theory of linear inverse RT to provide insight into the physical processes that control the cloud tomography problem and identify its limitations, supported by numerical experiments. We show that the Jacobian matrix becomes increasing ill-posed as the optical size of the medium increases and the forward-scattering peak of the phase function decreases. This suggests that tomographic retrievals of clouds will become increasingly difficult as clouds become optically thicker. Retrievals of asymptotically thick clouds will likely require other sources of information to be successful. In Loveridge et al. (2023a; hereafter Part 2), we examine how the accuracy of the retrieved 3D volume extinction coefficient varies as the optical size of the target medium increases using synthetic data. We do this to explore how the increasing error in the approximate Jacobian and the increasingly ill-posed nature of the inversion in the optically thick limit affect the retrieval. We also assess the accuracy of retrieved optical depths and compare them to retrievals using 1D radiative transfer.

The Dynamics of Megafire Smoke Plumes in Climate Models: Why a Converged Solution Matters for Physical Interpretations

AbstractAs the climate system warms, megafires have become more frequent with devastating effects. A byproduct of these events is the creation of smoke plumes that can rise into the stratosphere and spread across the globe where they reside for many months. To gain a deeper understanding of the plume dynamics, global climate simulations of a megafire were performed at a wide range of grid spacings from 2.0° down to 7 km, including a 7 km nonhydrostatic experiment. The analysis focuses on how the resolved dynamics affects the specification of the plume characteristics such as injection height and black carbon (BC) mass. Prior studies initialize the smoke plume at one or a few grid points and this is shown here to produce severely dissipative dynamics. In order to validate such simulations with observations, enhancements of the plume characteristics to offset the dissipation is necessary. Using a numerically converged simulation, sensitivity tests show that to approximate the observed stratospheric lifetime, a reduction in BC fraction by 50% is necessary for external mixtures. The vorticity dynamics of the plume is also analyzed with a Lagrangian budget to understand the mechanisms responsible for the evolution of a collocated anticyclonic vortex. The results can be distilled down into a simple conceptual model. As the plume rises, the air diverges at the top of the updraft where the largest concentrations of smoke are found. This divergence induces a dilution of the background cyclonic absolute vorticity producing an anticyclonic vortex. Vortex decay occurs from opposite arguments.

Simple and Inexpensive Downdraft Table to Limit Aerosol Exposure from Patients, Aerosol-Generating Procedures, and Surgical Smoke

Pathogenic aerosols are common, especially in clinical settings. Aerosols are released from quiet and forced respiration, non-respiratory movements (e.g., coughing and sneezing), aerosol-generating procedures, and surgical smoke plumes. Aerosols may contain viruses (e.g., coronaviruses, influenza viruses, adenoviruses) and bacteria (e.g., Streptococcus pneumoniae, Stapylococcus aureus, Pseudomonas aeruginosa, Mycobacterium tuberculosis). Surgical smoke plumes may contain harmful volatile organic compounds (e.g., formaldehyde), viral particles (e.g., human papillomavirus), or cancerous cells. Thus, the containment of airborne pathogenic organisms, xenobiotics, and bioaerosols is of the utmost importance. Yet, despite the importance of negative airflow and exhaust ventilation, many clinical environments do not have adequate ventilation systems— often due to significant monetary expenses or other barriers to access such as remote locations. Recently, a relatively inexpensive downdraft table (< 200 USD), made of wood, tarps, rebar, and corrugated steel roofing material and a simple local exhaust ventilation system (~ 300 USD) have been demonstrated to eliminate airborne VOCs, including VOCs found in surgical smoke. However, the table has not been assessed regarding the capacity to remove water-based aerosols. Therefore, the purpose of this research was to assess the ability of the downdraft table and local exhaust ventilation system to exhaust varied water-based and organic aerosols. The study identifies that a simple and inexpensive downdraft table can effectively exhaust aerosols like those found in clinical environments. This study represents an innovation in accessible medical technology that will improve health and safety in regions that include developing countries and remote locations.

UAV-Based Wildland Fire Air Toxics Data Collection and Analysis.

Smoke plumes emitted from wildland-urban interface (WUI) wildfires contain toxic chemical substances that are harmful to human health, mainly due to the burning of synthetic components. Accurate measurement of these air toxics is necessary for understanding their impacts on human health. However, air pollution is typically measured using ground-based sensors, manned airplanes, or satellites, which all provide low-resolution data. Unmanned Aerial Vehicles (UAVs) have the potential to provide high-resolution spatial and temporal data due to their ability to hover in specific locations and maneuver with precise trajectories in 3-D space. This study investigates the use of an octocopter UAV, equipped with a customized air quality sensor package and a volatile organic compound (VOC) air sampler, for the purposes of collecting and analyzing air toxics data from wildfire plumes. The UAV prototype developed has been successfully tested during several prescribed fires conducted by the California Department of Forestry and Fire Protection (CAL FIRE). Data from these experiments were analyzed with emphasis on the relationship between the air toxics measured and the different types of vegetation/fuel burnt. BTEX compounds were found to be more abundant for hardwood burning compared to grassland burning, as expected.

Influence of stubble burning on air quality of Northern India: a case study of Indo-Gangetic plains of India

Stubble burning is an emerging environmental issue in Northern India, which has severe implications for the air quality of the region. Although stubble burning occurs twice during a year, first during April-May and again in October-November due to paddy burning, the effects are severe during October-November months. This is exacerbated by the role of meteorological parameters and presence of inversion conditions in the atmosphere. The deterioration in the atmospheric quality can be attributed to the emissions from stubble burning which can be perceived from the changes observed in land use land cover (LULC) pattern, fire events, and sources of aerosol and gaseous pollutants. In addition, wind speed and wind direction also play a role in changing the concentration of pollutants and particulate matter over a specified area. The present study has been carried out for the states of Punjab, Haryana, Delhi, and western Uttar Pradesh to study the influence of stubble burning on the aerosol load of this region of Indo-Gangetic Plains (IGP). In this study, the aerosol level, smoke plume characteristics, long-range transport of pollutants, and affected areas during October-November from year 2016 to 2020 were examined over the Indo-Gangetic Plains (Northern India) region by the satellite observations. By MODIS-FIRMS (Moderate Resolution Imaging Spectroradiometer-Fire Information for Resource Management System) observations, it was revealed that there was an increase in stubble burning events with the highest number of events being observed during the year 2016 and then a decrease in the number of events in subsequent years from 2017 to 2020. MODIS observations revealed a strong AOD gradient from west to east. The prevailing north-westerly winds assist the spread of smoke plumes over Northern India during the peak burning season of October to November. The findings of this study might be used to expand on the atmospheric processes that occur over northern India during the post-monsoon season. The pollutant, smoke plume features, and impacted regions of biomass-burning aerosols in this region are critical for weather and climate research, especially given the rising trend in agricultural burning over the previous two decades.

Impacts of estimated plume rise on PM2.5 exceedance prediction during extreme wildfire events: a comparison of three schemes (Briggs, Freitas, and Sofiev)

Abstract. Plume height plays a vital role in wildfire smoke dispersion and the subsequent effects on air quality and human health. In this study, we assess the impact of different plume rise schemes on predicting the dispersion of wildfire air pollution and the exceedances of the National Ambient Air Quality Standards (NAAQS) for fine particulate matter (PM2.5) during the 2020 western United States wildfire season. Three widely used plume rise schemes (Briggs, 1969; Freitas et al., 2007; Sofiev et al., 2012) are compared within the Community Multiscale Air Quality (CMAQ) modeling framework. The plume heights simulated by these schemes are comparable to the aerosol height observed by the Multi-angle Imaging SpectroRadiometer (MISR) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). The performance of the simulations with these schemes varies by fire case and weather conditions. On average, simulations with higher plume injection heights predict lower aerosol optical depth (AOD) and surface PM2.5 concentrations near the source region but higher AOD and PM2.5 in downwind regions due to the faster spread of the smoke plume once ejected. The 2-month mean AOD difference caused by different plume rise schemes is approximately 20 %–30 % near the source regions and 5 %–10 % in the downwind regions. Thick smoke blocks sunlight and suppresses photochemical reactions in areas with high AOD. The surface PM2.5 difference reaches 70 % on the West Coast of the USA, and the difference is lower than 15 % in the downwind regions. Moreover, the plume injection height affects pollution exceedance (>35 µg m−3) predictions. Higher plume heights generally produce larger downwind PM2.5 exceedance areas. The PM2.5 exceedance areas predicted by the three schemes largely overlap, suggesting that all schemes perform similarly during large wildfire events when the predicted concentrations are well above the exceedance threshold. At the edges of the smoke plumes, however, there are noticeable differences in the PM2.5 concentration and predicted PM2.5 exceedance region. For the whole period of study, the difference in the total number of exceedance days could be as large as 20 d in northern California and 4 d in the downwind regions. This disagreement among the PM2.5 exceedance forecasts may affect key decision-making regarding early warning of extreme air pollution episodes at local levels during large wildfire events.

Self-lofting of wildfire smoke in the troposphere and stratosphere: simulations and space lidar observations

Abstract. Wildfire smoke is known as a highly absorptive aerosol type in the shortwave wavelength range. The absorption of sunlight by optically thick smoke layers results in heating of the ambient air. This heating is translated into self-lofting of the smoke up to more than 1 km in altitude per day. This study aims for a detailed analysis of tropospheric and stratospheric smoke lofting rates based on simulations and observations. The main goal is to demonstrate that radiative heating of intense smoke plumes is capable of lofting them from the lower and middle free troposphere (injection heights) up to the tropopause without the need of pyrocumulonimbus (pyroCb) convection. The further subsequent ascent within the lower stratosphere (caused by self-lofting) is already well documented in the literature. Simulations of absorbed solar radiation by smoke particles and resulting heating rates, which are then converted into lofting rates, are conducted by using the ECRAD (European Centre for Medium-Range Weather Forecasts Radiation) scheme. As input parameters thermodynamic profiles from CAMS (Copernicus Atmosphere Monitoring Service) reanalysis data, aerosol profiles from ground-based lidar observations, radiosonde potential temperature profiles, CALIOP (Cloud–Aerosol Lidar with Orthogonal Polarization) aerosol measurements, and MODIS (Moderate Resolution Imaging Spectroradiometer) aerosol optical depth retrievals were used. The sensitivity analysis revealed that the lofting rate strongly depends on aerosol optical thickness (AOT), layer depth, layer height, and black carbon (BC) fraction. We also looked at the influence of different meteorological parameters such as cloudiness, relative humidity, and potential temperature gradient. To demonstrate the applicability of our self-lofting model, we compared our simulations with the lofting processes in the stratosphere observed with CALIOP after major pyroCb events (Canadian fires in 2017, Australian fires in 2019–2020). We analyzed long-term CALIOP observations of smoke layers and plumes evolving in the UTLS (upper troposphere and lower stratosphere) height region over Siberia and the adjacent Arctic Ocean during the summer season of 2019. Our results indicate that self-lofting contributed to the vertical transport of smoke. We hypothesize that the formation of a near-tropopause aerosol layer, observed with CALIOP, was the result of self-lofting processes because this is in line with the simulations. Furthermore, Raman-lidar-based aerosol typing (in Leipzig and the High Arctic) clearly indicated the dominance of smoke in the UTLS aerosol layer since August 2019, most probably also the result of smoke self-lofting.

From Rosa Mistika, Chapter 7

from Rosa Mistika, Chapter 7 Euphrase Kezilahabi (bio) and Jay Boss Rubin (bio) Strict as he was when it came to raising his daughters, Zakaria still wanted to see them married off as quickly as possible. When he heard Rosa had gotten herself a fiancé, he was delighted. Zakaria could already feel the load being lifted from his shoulders. Around this time, Zakaria was accustomed to saying, "Having so many daughters is a real hassle! You wouldn't believe the number of visitors we get. People stopping by to ask for directions," he'd complain. "People asking for a glass of water, then getting up to leave after a single sip." Five daughters in one location did attract a lot of attention. Boys in the area referred to Zakaria's compound as "the zoo." Zakaria and Regina awaited the arrival of Rosa's fiancé with great anticipation. They also wondered, Where is he going to sleep? It would be a shame for a guest—especially an important one—to have to cram into an already-crowded house. They'd ask him to sleep in the living room, they decided. That was the best they could do. Their other daughters all heard the whispers that a visitor would soon be in their midst—the man who'd proposed to Rosa, they gathered. When Deogratias finally arrived, he was given the royal treatment. Each day, a chicken was slaughtered in his honor. No one rushed into the official business they had to discuss, and Deogratias was given ample time to spend with his fiancé. There was only one thing that bothered Zakaria and Regina: while he was eating, and even when he paused to utter greetings of respect to passing elders, Deogratias failed to take off his hat. Somehow, he failed to understand this most basic custom, even though he was an African like them. Zakaria and Deogratias were seated at the fire one evening when Deogratias first braved the matter of the mahari, the dowry he had come to pay. Zakaria was well prepared. "Aaa, yes, my child, the mahari," he began. "My wife and I have started discussing it, but I can't yet give you our final answer. I'll just tell you our initial requests, so you can get your affairs in order. For starters"—Zakaria paused and motioned with his mouth over to their dilapidated dwelling—"you won't be shocked to hear we need a house." Zakaria went into great detail about how he envisioned the new structure. "If you can help me out with the roof," he said, "I can manage the rest. The mahari should also include," he continued, "four cows, two goats, a pestle [End Page 129] and mortar set, three chairs, and a thousand shillings. Last but not least, for now, one jug of moonshine. Not as part of the official dowry, but for me personally." "None of that is a problem," Deogratias responded after Zakaria was done. "Back home," he said with pride, "we pay up to 30 cows for the mahari, sometimes more." "Don't speak too soon!" Zakaria said right away. "That was only my partial list. And I still have to send you to my relatives. And the relatives from my wife's side of the family must have their needs met, too. After all," he explained, "the child is not mine alone to give away." "Sawa," Deogratias agreed. "None of what you say is unfair." The following day, Zakaria intended to show his guest around the island. Deogratias wasn't opposed to it; it was his first time visiting Ukerewe. For Zakaria, there was only one place such a tour could take them: to a location he was already quite familiar with. Zakaria led Deogratias to the edge of a clump of trees. From somewhere inside, plumes of smoke were issuing and a soft murmur could be heard. Deogratias knew right away where they were headed. He was a boozer, after all, just like Zakaria. Deogratias could booze it up like a full-grown man. Inside the thicket, Zakaria and Deogratias joined the small crowd gathered around the fire. They stayed at the village distillery the entire...

Particulate Levels Underneath Landscape Fire Smoke Plumes in the Sydney Region of Australia

Smoke pollution from landscape fires is a major health problem, but it is difficult to predict the impact of any particular fire. For example, smoke plumes can be mapped using remote sensing, but we do not know how the smoke is distributed in the air-column. Prescribed burning involves the deliberate introduction of smoke to human communities but the amount, composition, and distribution of the pollution may be different to wildfires. We examined whether mapped plumes produced high levels of particulate pollution (PM2.5) at permanent air quality monitors and factors that influenced those levels. We mapped 1237 plumes, all those observed in 17 years of MODIS imagery over New South Wales, Australia, but this was only ~20% of known fires. Prescribed burn plumes tended to occur over more populated areas than wildfires. Only 18% of wildfire plumes and 4% of prescribed burn plumes passed over a monitor (n = 115). A minority of plumes caused a detectable increase in PM2.5: prescribed burn plumes caused an air quality exceedance for 33% of observations in the daytime and 11% at night, wildfire plumes caused exceedances for 48% and 22% of observations in the day and night-time, respectively. Thus, most plumes remained aloft (did not reach the surface). Statistical modelling revealed that wind speed, temperature, and mixing height influenced whether a plume caused an exceedance, and there was a difference between prescribed and wild fires. In particular, in wind speeds below 1 kmhr−1, exceedance was almost certain in prescribed burns. This information will be useful for planning prescribed burning, preparing warnings, and improving our ability to predict smoke impacts.

Measurement report: Emission factors of NH3 and NHx for wildfires and agricultural fires in the United States

Abstract. During the 2019 Fire Influence on Regional to Global Environments and Air Quality (FIREX-AQ) study, the NASA DC-8 carried out in situ chemical measurements in smoke plumes emitted from wildfires and agricultural fires in the contiguous United States. The DC-8 payload included a modified proton-transfer-reaction time-of-flight mass spectrometer (PTR-ToF-MS) for the fast measurement of gaseous ammonia (NH3) and a high-resolution time-of-flight aerosol mass spectrometer (AMS) for the fast measurement of submicron particulate ammonium (NH4+). We herein report data collected in smoke plumes emitted from 6 wildfires in the Western United States, 2 prescribed grassland fires in the Central United States, 1 prescribed forest fire in the Southern United States, and 66 small agricultural fires in the Southeastern United States. Smoke plumes contained double to triple digit ppb levels of NH3. In the wildfire plumes, a significant fraction of NH3 had already been converted to NH4+ at the time of sampling (≥2 h after emission). Substantial amounts of NH4+ were also detected in freshly emitted smoke from corn and rice field fires. We herein present a comprehensive set of emission factors of NH3 and NHx, with NHx=NH3+NH4+. Average NH3 and NHx emission factors for wildfires in the Western United States were 1.86±0.75 g kg−1 and 2.47±0.80 g kg−1 of fuel burned, respectively. Average NH3 and NHx emission factors for agricultural fires in the Southeastern United States were 0.89±0.58 and 1.74±0.92 g kg−1, respectively. Our data show no clear inverse correlation between modified combustion efficiency (MCE) and NH3 emissions. The observed NH3 emissions were significantly higher than measured in previous laboratory experiments in the FIREX FireLab 2016 study.

Potential Airborne Releases and Deposition of Radionuclides from the Santa Susana Field Laboratory during the Woolsey Fire.

The Santa Susana Field Laboratory (SSFL), located in southern California, is a former research facility, and past activities have resulted in residual radioactive contamination in Area IV of the Site. The Woolsey Fire burned across the site, including some of the contaminated areas, on 8-11 November 2018. Atmospheric transport modeling was performed to determine where the smoke plume went while the fire burned across the SSFL and the deposition footprint of particulates in downwind communities. Any radionuclides on vegetation and in surface soil released by the fire were assumed to follow particulate matter transport path and deposition. The predicted deposition footprint was used to guide confirmatory soil sampling at 16 locations including background. Highest offsite deposition was determined to be northeast of the Oak Park community, which is located about 6 km southwest of SSFL. Depth-profile sampling was used to evaluate whether radionuclides of SSFL origin were potentially emitted and deposited during the Woolsey Fire. If radionuclides had been deposited from the Woolsey Fire at sufficient concentrations, then they would be detected in the surface layer and would be expected to be higher within the plume footprint than outside it. An upper bound estimate of the hypothetical effective dose to a person in Oak Park based on measured radionuclide concentrations in soil and vegetation on the SSFL was less than 0.0002 mSv. The occurrence of naturally occurring radionuclides at concentrations above the established background for the SSFL was attributed to natural variability in geologic formations and not SSFL. No anthropogenic radionuclides were measured at levels above those expected from global fallout. The soil sampling confirmed that no detectable levels of SSFL-derived radionuclides migrated from SSFL at the locations sampled because of the Woolsey Fire or from past operations of the SSFL.

Fire smoke dispersion inside and outside of a warehouse building in moderate and strong wind conditions

A moderate-sized (8 MW) fire was modelled in a warehouse located in an urban area with diverse architecture, in wind conditions. The investigation includes the effects of neighbouring architecture on the wind field, and in consequence on the smoke control performance and the smoke dispersion in the near-field of the building. Overall, 25 CFD simulations were performed with ANSYS Fluent CFD code, for wind velocities of 5 m/s (moderate), 10 m/s (strong) at 12 wind angles each (0°–330°, 30° increment), and at 0 m/s for reference. The building smoke venting system's performance was affected by the wind, reaching 74%–114% and 78%–158% of the reference mass flow at the moderate and strong wind velocities, respectively. Surprisingly, in multiple cases the exhaust flow rate of ventilators was increased, rather than hindered by the wind. We attribute this to the arrangement of inlets and outlets on façades and the resulting pressure difference between the wall and roof openings. The smoke plume was highly dependent on the wind angle, and the type of architecture up- and downwind of the fire. Significant urban canyon effects and large vortices forming behind tall buildings were observed, leading to smoke accumulation in a large distance from the fire.

Surgical Management of Inferior Turbinate Hypertrophy in the Era of Widespread Communicable Disease.

Inferior turbinate reduction procedures have been performed for decades. After significant evolution, turbinoplasty and other mucosal-sparing techniques have become the main method to successfully reduce turbinate hypertrophy. The debate of which technique produces the most effective and durable outcomes is ongoing. During this critical era of widespread communicable diseases, including but not limited to COVID-19, HIV, and hepatitis, additional attention is necessary to balance outcomes with a degree of generation of airborne particles when selecting a technique. This review article aims to identify the optimal method for inferior turbinate reduction that weighs both outcomes and aerosol production. The MEDLINE database was searched to discover relevant publications through August 2022. Key search terms included inferior turbinate hypertrophy, turbinate reduction surgery, turbinoplasty methods, surgical management of turbinate hypertrophy, surgical aerosol generation, COVID-19 surgery, surgery smoke plume, SARS-CoV-2 transmission during surgery, and nasal procedures COVID-19 aerosols. Surgical management of the inferior turbinates includes radiofrequency ablation (RFA), microdebrider-assisted turbinoplasty (MAIT), electrocautery, laser, and ultrasound. Piezo-assisted turbinoplasty and a turbinate-specific coblation wand are new additions to the literature. All techniques appear to improve patient symptoms of nasal obstruction. MAIT and RFA are comparable, although MAIT demonstrated better long-term outcomes in some studies and appears to generate fewer airborne particles. Studies evaluating the production of aerosols due to RFA are lacking. Ultrasound outcomes are also excellent and generate no aerosols, but the technique has not been compared against the microdebrider. Electrocautery can result in increased pain and crusting for patients and causes the highest amount of aerosols. Deficiencies of current studies, including a lack of comparison of aerosol generation, duration of follow-up, omission of outfracture, and inadequate randomized controlled trials among existing and new techniques, have limited the identification of the best inferior turbinate reduction method. Given the durability of MAIT and its minimal aerosol production, it can be reinforced as the most sensible technique until further evidence is available.

Predicting wind-driven spatial deposition through simulated color images using deep autoencoders

For centuries, scientists have observed nature to understand the laws that govern the physical world. The traditional process of turning observations into physical understanding is slow. Imperfect models are constructed and tested to explain relationships in data. Powerful new algorithms can enable computers to learn physics by observing images and videos. Inspired by this idea, instead of training machine learning models using physical quantities, we used images, that is, pixel information. For this work, and as a proof of concept, the physics of interest are wind-driven spatial patterns. These phenomena include features in Aeolian dunes and volcanic ash deposition, wildfire smoke, and air pollution plumes. We use computer model simulations of spatial deposition patterns to approximate images from a hypothetical imaging device whose outputs are red, green, and blue (RGB) color images with channel values ranging from 0 to 255. In this paper, we explore deep convolutional neural network-based autoencoders to exploit relationships in wind-driven spatial patterns, which commonly occur in geosciences, and reduce their dimensionality. Reducing the data dimension size with an encoder enables training deep, fully connected neural network models linking geographic and meteorological scalar input quantities to the encoded space. Once this is achieved, full spatial patterns are reconstructed using the decoder. We demonstrate this approach on images of spatial deposition from a pollution source, where the encoder compresses the dimensionality to 0.02% of the original size, and the full predictive model performance on test data achieves a normalized root mean squared error of 8%, a figure of merit in space of 94% and a precision-recall area under the curve of 0.93.

Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ)

AbstractThe NOAA/NASA Fire Influence on Regional to Global Environments and Air Quality (FIREX‐AQ) experiment was a multi‐agency, inter‐disciplinary research effort to: (a) obtain detailed measurements of trace gas and aerosol emissions from wildfires and prescribed fires using aircraft, satellites and ground‐based instruments, (b) make extensive suborbital remote sensing measurements of fire dynamics, (c) assess local, regional, and global modeling of fires, and (d) strengthen connections to observables on the ground such as fuels and fuel consumption and satellite products such as burned area and fire radiative power. From Boise, ID western wildfires were studied with the NASA DC‐8 and two NOAA Twin Otter aircraft. The high‐altitude NASA ER‐2 was deployed from Palmdale, CA to observe some of these fires in conjunction with satellite overpasses and the other aircraft. Further research was conducted on three mobile laboratories and ground sites, and 17 different modeling forecast and analyses products for fire, fuels and air quality and climate implications. From Salina, KS the DC‐8 investigated 87 smaller fires in the Southeast with remote and in‐situ data collection. Sampling by all platforms was designed to measure emissions of trace gases and aerosols with multiple transects to capture the chemical transformation of these emissions and perform remote sensing observations of fire and smoke plumes under day and night conditions. The emissions were linked to fuels consumed and fire radiative power using orbital and suborbital remote sensing observations collected during overflights of the fires and smoke plumes and ground sampling of fuels.