Tutorials Information

Abstract: This tutorial is the first of two that introduce the broad field of aerosol science. We begin with the particle size distribution, which provides a concise physical description of the aerosol that determines its size-dependent properties. We then turn our attention to the behavior of individual particles that governs how the aerosol evolves, its impacts, and enables measurements. The drag forces that act on a particle determine its settling velocity and whether it can follow the motions of the surrounding gas. Stokes law describes the drag forces on spherical particles moving at modest velocities, but corrections are needed if the particles are small relative to the mean-free-path of the gas molecules, too large to be in the creeping flow regime, or not spherical. Knowledge of these scaling principles makes it possible to relate particle aerodynamics in seemingly disparate systems. The equations of motion for an aerosol particle reveal a measurable property, the aerodynamic relaxation time, that determines its sedimentation velocity and whether the particle will follow changes in velocity or direction of the gas in which it is entrained. We will examine how these inertial effects lead to deposition of large particles in the respiratory tract, filters, and sampling systems, and how they can lead to biases in aerosol sampling. Inertial effects are also used to determine an inertial size of the aerosol particles. Instruments for measuring this aerodynamic equivalent diameter will be briefly discussed. We will end this first introductory tutorial with a brief look at how inertial effects alter the size distribution of the aerosol released from a cough in a closed, well-mixed room.

Bio: Richard C. Flagan is the McCollum/Corcoran Professor of Chemical Engineering and Environmental Science and Engineering at the California Institute of Technology. He has served as the President of AAAR, and as Editor-in-Chief of Aerosol Science and Technology. His research spans the field of aerosol science, including atmospheric aerosols, aerosol instrumentation, homogeneous nucleation, aerosol synthesis of nanoparticles and other materials, bioaerosols ranging from pollen to the SARS-CoV-2 virus, and aerosols in the atmospheres of other worlds. His many contributions to the field of aerosol science have been acknowledged with the Sinclair Award of the AAAR, the Smoluchowski Award of the Gesellschäft für Aerosolforschung, and the Fuchs Award. He is a member of the National Academy of Engineering.

Abstract: Microfluidics is a powerful platform for precise, high-throughput, low-cost measurements with small volumes of sample. The microscale platform is already widely established in fields of biology, medicine, chemistry, and rheology, and, as highlighted in this tutorial, is rapidly emerging as an important platform for aerosol science measurements. This tutorial on aerosol measurements with microfluidics will involve three main sections:

• Basic operating principles of microfluidic flows, with emphasis on two-phase flows for aerosol science applications. General techniques for generating, detecting, trapping, sorting, filtering, and manipulating droplets and particles in microscale flows will be presented.
• Current and emerging aerosol science microfluidic measurements, with comparison to conventional aerosol experimental methods where applicable. In addition, methods for sample collection will be discussed.
• Step-by-step guidance on designing, fabricating, and operating devices, with a practical hands-on demonstration of assembling a device and generating fluid flows.

Bio: Dr. Cari S. Dutcher is an Associate Professor of Mechanical Engineering (ME) and Chemical Engineering and Materials Science (CEMS) at the University of Minnesota, Twin Cities, with research interests in aerosol science and multiphase fluids. Cari has served on the AAAR board of directors, AAAR aerosol physics working group chair, and currently serves as secretary on the AAAR Executive Board. She has received a number of early faculty awards, including the 3M Non-Tenured Faculty Award, NSF CAREER and AAAR Kenneth T. Whitby Award. Cari received her Ph.D. from the University of California, Berkeley in Chemical Engineering and was a postdoc at the University of California, Davis in the Air Quality Research Center.

Bio: Dr. Andrew R. Metcalf is an Assistant Professor in Environmental Engineering and Earth Sciences at Clemson University. Andrew’s research interests are in atmospheric aerosols, with a focus on black carbon aerosol, and on developing new technologies for detecting airborne particles, including using microfluidics. Andrew is the PI for the SP2 NSF community instrument facility. Andrew received his Ph.D. from Caltech and was a postdoc at the Combustion Research Facility at Sandia National Lab and at the University of Minnesota.

Abstract: A number of population-based epidemiological studies as well as toxicological and clinical studies indicate a strong association between ambient particulate matter (PM) exposure and adverse health outcomes. The national ambient air quality standards in both developed and developing nations are currently based on mass concentration of the particles. This mass-centered approach is flawed because toxicological studies have shown a substantial heterogeneity in the toxicities of ambient PM2.5 coming from different emission sources. It is clear that there is a necessity to search for alternative metric(s) than mass to represent PM in the epidemiological models, which in turn requires clarity on the exact mechanisms underlying PM toxicity. Currently, some progress has been made in this regard in the past two decades, which indicates that PM sources, atmospheric processes, chemical composition and pathology of diseases share a complex relationship with each other. Recently, oxidative potential (OP) has emerged as a proxy for PM toxicity, although currently there is a lack of consensus regarding the most appropriate method to measure PM OP. There are also a range of toxicity endpoints, e.g. cell death, metabolic activity, cell membrane integrity, and DNA damage that one could choose from, which has often led to the debate on whether or not a single endpoint could adequately represent PM toxicity. We target to address some of these questions in this tutorial. We will first start with the basic definitions of common OP and toxicity endpoints. Next, we will describe various methods to measure these endpoints. Here, we will also discuss recent developments in formulating newer endpoints, as well as the newly built automated and high-throughput instruments to measure PM oxidative and toxicological properties. And, finally, we will present the results from numerous studies, including from our own investigations, showing the biological relevance of measuring these properties of the ambient particles.

Bio: Dr. Verma is an Assistant Professor at the University of Illinois Urbana-Champaign and his current work is focused on measuring the oxidative and toxicological properties of ambient air pollutants, investigating their emission sources and linkages with the observed health effects. In his 15 years of research, he has published 45 peer-reviewed articles in highly ranked journals and has presented his work in more than 50 various seminars/meetings and conferences, including several invited talks. He was the past chair of the Health-Related Aerosol working group at AAAR and has earned numerous awards and recognitions for his work including the NSF CAREER award (2019), Honorable Mention for the James J. Morgan Early Career Award from Environmental Science and Technology journal, Center for Advanced Study Fellow (2021-22), and invited chair for special symposiums/sessions on Air Pollution and Health in the annual AAAR and AGU conferences.

Abstract: This AAAR tutorial session will expand on the editor-invited tutorial article by the presenter and include additional resources to help with implementation: Suresh, V., and R. Gopalakrishnan (2021). "Tutorial: Langevin Dynamics methods for aerosol particle trajectory simulations and collision rate constant modeling." Journal of Aerosol Science 155: 105746. The Langevin Dynamics (LD) method (also known in the literature as Brownian Dynamics) is routinely used to simulate aerosol particle trajectories for transport rate constant calculations as well as to understand aerosol particle transport in internal and external flow fields. This tutorial intends to explain the methodological details of setting up a LD simulation of a population of aerosol particles and visualize the obtained classical trajectories. The applicability and limitations of the translational Langevin equation to model the combined stochastic and deterministic motion of particles in fields of force or fluid flow will be presented. The drag force and stochastic “diffusion” force terms that appear in the Langevin equation will be discussed along with a summary of common forces relevant to aerosol systems (electrostatic, gravity, van der Waals, …); commonly used first order and a fourth order Runge-Kutta time stepping schemes for linear stochastic ordinary differential equations are to be presented. Illustrative demonstrations of particle trajectory simulations such as particle settling under gravity, particle-ion interactions (charging), particle-particle hydrodynamic interactions (coagulation), non-spherical particle rotation, … will be presented. Implementation of coupling between system of Langevin equations and Eulerian field variable(s) such as the background gas velocity field described by Navier-Stokes equation, or the electric potential described by Poisson equation will also be discussed. The tutorial session will be concluded with potential applications and caveats to the usage of LD.

Bio: Dr. Ranganathan Gopalakrishnan is currently the UMRF Ventures Assistant Professor in the Department of Mechanical Engineering at The University of Memphis since 2016, following postdoctoral stints at University of California-Berkeley (2014-15) and California Institute of Technology (2013-14). He obtained his PhD in Mechanical Engineering from the University of Minnesota in 2013 and Bachelor of Technology degree in Mechanical Engineering from the National Institute of Technology, Tiruchirappalli, India in 2008. His research interests include particulate transport processes in aerosols, dusty plasmas, and ionized gases. He is a recipient of the DOE EARLY CAREER award for the year FY2020 from the Office of Fusion Energy Sciences, US Department of Energy Office of Science (SC). He has authored several articles on the use of Langevin Dynamics trajectory simulations for modeling particle processes such as charging, coagulation and condensation.

Abstract: This tutorial continues the basic introduction to aerosol science, continuing the discussion of the physics of a single particle, and then examining particle diffusion, and finally turning our attention to the dynamics of aerosol populations. While large particles can be separated due to their inertia, inertial methods are difficult to use for small ones, but aerodynamic drag can be used for small particles if they are first charged and then subjected to an electric field. This method is applied in differential mobility analysis to obtain the particle size distribution in terms of a mobility equivalent diameter in the scanning mobility particle sizer (SMPS). Small particles can also deviate from the gas motion because Brownian motion causes them to diffuse, enhancing deposition of small particles in the respiratory tract, sampling systems, and filters. Diffusion also degrades the performance of the SMPS for small particles, which will be discussed. Aerosol particles can change size due to diffusion of vapors to or from them. Vapors can alter the particles and their size distribution by condensing on them or evaporating from them. We will examine the thermodynamics and vapor transport processes, their use in aerosol particle counting in the condensation particle counter (CPC), and examine effects on the particle size distribution. Under extreme conditions, vapors form new particles directly from the vapor phase through homogeneous nucleation of one or more vapor species, which we shall briefly examine. The particle size distribution is also altered by coagulation in which two particles combine through collision to form one large particle. These diverse processes can be combined to form a general dynamic equation for aerosols, which will be the final topic of these introductory aerosols.

Bio: Richard C. Flagan is the McCollum/Corcoran Professor of Chemical Engineering and Environmental Science and Engineering at the California Institute of Technology. He has served as the President of AAAR, and as Editor-in-Chief of Aerosol Science and Technology. His research spans the field of aerosol science, including atmospheric aerosols, aerosol instrumentation, homogeneous nucleation, aerosol synthesis of nanoparticles and other materials, bioaerosols ranging from pollen to the SARS-CoV-2 virus, and aerosols in the atmospheres of other worlds. His many contributions to the field of aerosol science have been acknowledged with the Sinclair Award of the AAAR, the Smoluchowski Award of the Gesellschäft für Aerosolforschung, and the Fuchs Award. He is a member of the National Academy of Engineering.

Abstract: Secondary aerosol is an important component of atmospheric fine particles that generally consists of organic compounds, sulfates, and nitrates. The processes that lead to the formation of this material are often complex, and can involve gas- and particle-phase chemistry, nucleation, and gas-particle partitioning. In this tutorial I will discuss the major chemical reactions and partitioning processes involved in the formation of secondary organic and inorganic aerosol (with a strong emphasis on organic aerosol) using examples from laboratory and field studies.

Bio: Dr. Paul Ziemann is a Professor in the Department of Chemistry and a Fellow in the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder. He received a doctorate in chemistry from Penn State University and was a postdoctoral researcher in the Particle Technology Laboratory at the University of Minnesota. His research interests include laboratory studies of the kinetics, products, and mechanisms of organic oxidation reactions and their effects on the composition of gases, particles, and surfaces in outdoor and indoor air. He was a recipient of the AAAR Whitby Award in 2001 and served as President of AAAR from 2009–2010.

Abstract: This tutorial will overview biological aerosols and methods for their measurement and study. Specifically, this tutorial will cover three primary areas: bioaerosol measurement, laboratory techniques, and field studies. Each topic will be covered from environmental bioaerosol and infectious aerosol perspectives. Both real-time and offline techniques for bioaerosol measurement will be covered, as well as laboratory techniques for bioaerosol study. Field studies will cover a range of situation from outdoor measurements to studies in clinical settings.

Bio: Dr. Joshua L. Santarpia is the Research Director for Counter WMD programs at the National Strategic Research Institute, Associate Professor of Microbiology and Pathology, and Program Director for Biodefense and Health Security Degree Program at the University of Nebraska Medical Center. His work is generally in the field of aerobiology, the study of airborne microorganisms. His group focuses on the development of novel bioaerosol measurement tools, including real-time sensors and the integrated UAS samplers, understanding the optical and other signatures that can be used to detect and identify biological aerosol and studied how those signatures change over time, and the study of bioaerosol in medical environments. Most recently, he has applied these methods to characterizing SARS-CoV-2 aerosol in the patient environment and characterizing aerosol risk in public spaces.

Bio: Alex Huffman is an Associate Professor of Analytical and Environmental Chemistry at the University of Denver after having earned his Ph.D. in Analytical/Atmospheric Chemistry from the University of Colorado. His research group focuses on the development and application of new scientific approaches to detecting bioaerosols in the atmosphere and heterogeneous chemical reactions on bioaerosol surfaces. During the COVID-19 pandemic Dr. Huffman added research focus on transmission and removal of aerosols in indoor environments, including relevant aerosol modeling, mitigation, and monitoring efforts. Dr. Huffman has more than 19 years of experience with atmospheric aerosol science and has published more than 40 papers related to bioaerosols. Dr. Huffman has been involved with AAAR since 2005, has served on several committees, and was the bioaerosol special session and working group chair from 2013-2015.

Abstract: Three-dimensional Chemical Transport Models (CTMs) are mathematical representations of physical and chemical processes relevant to trace gas and particle pollutants and are used to support policy actions to mitigate negative human health impacts and understand climate change. Here we discuss three different aspects of using CTMSs to address atmospheric aerosol science and applications. First, CTMs integrate all our understanding of complex processes governing aerosols based on decades of work combining laboratory and field measurements with theoretical parameterizations. Yet, when they are challenged to predict aerosol states within a new region, model-measurement differences provide clues about processes that are not understood or well-represented in models. To be particularly useful for diagnosing key missing processes in models, applying a high resolution 3D CTM to a new field experiment requires careful design and characterization of the region of interest, which often requires significant efforts. We will discuss broadly the key considerations for careful design of a modeling study to explain field measurements of secondary organic aerosols.

Second, we will discuss the CTMs with different levels of complexity, which forecast the 3D concentrations of different aerosol and other chemical constituents on regional and global scales. Some of these CTMs are integrated with operational weather models to provide smoke forecasts critical for informing susceptible populations or responding to emergency events like wildland fires. NOAA’s high-resolution coupled smoke-weather model simulates the smoke transport by incorporating the real-time biomass burning emissions algorithm, fire plume rise parameterization, advection and turbulent mixing, and removal processes of the aerosol. The high aerosol loadings in the atmosphere also affect weather and visibility. We will present some examples on how the coupled aerosol-meteorology models simulate these processes, and how simulating aerosols explicitly in the numerical weather prediction models can help us to improve weather forecasting. The offline CTMs that forecast primary and secondary aerosol pollution from anthropogenic and other sources will be discussed. Additionally, we will present NOAA's global aerosol forecast model and its application to some long-range aerosol transport case studies.

Lastly, we will survey a number of analysis techniques that leverage CTM predictions along with data from other sources (e.g. ambient monitoring data, satellite retrievals, health data, etc.) to understand the impact of particle air pollution on public health. The results of these analysis techniques provide necessary support for driving air pollution policy decisions. Through a discussion of each of these examples, this tutorial will offer context for how large-scale models can be used to demonstrate the impact of aerosol research findings and how they may further support prioritization of future research efforts.

Bio: Dr. Ben Murphy is a physical scientist at the U.S. EPA where he develops chemical transport models for regulatory applications. A member of the Community Multiscale Air Quality (CMAQ) model development team, he primarily focuses on formation, processing and loss of organic aerosol and ultrafine particles. He is also interested in developing models for quantifying the atmospheric fate and transport of Per- and PolyFluoroAlkyl Substances (PFAS).

Bio: Dr. Manish Shrivastava is currently a senior Earth Systems Scientist at the Pacific Northwest National Laboratory (PNNL). His research bridges measurements and modeling of secondary organic aerosols (SOA), and their interactions with clouds, radiative forcing and human health. Over the past decade, he has developed and implemented several new model formulations of SOA within community regional and global models based on laboratory and field measurements. In 2018, he was awarded the highly prestigious and competitive U.S. Department of Energy Early Career Award to conduct research on finding missing links associated with aerosol-cloud interactions.

Bio: Dr. Ahmadov is a research scientist at CU Boulder CIRES, working for NOAA’s Global Systems Laboratory. His main research areas are air quality modeling, atmospheric model development, and impact of fire emissions on air quality and weather. Dr. Ahmadov is the primary developer of NOAA’s operational smoke forecasting model HRRR-Smoke.

Abstract: Ambient meteorological conditions have a profound impact on the lifecycle and lifetime of aerosol populations that contributes to complex spatiotemporal variations in aerosol properties observed in the atmosphere. While short-term and small-scale processes are important for urban air quality, the accumulation of these smaller-scale effects coupled with longer temporal variability have implications for climate. This tutorial will describe how a range of meteorological parameters and processes influence the formation, transformation, and fate of aerosols. More specifically, we will focus on how meteorology affects emissions of primary aerosols and their precursors, new particle formation, chemistry, gas-to-particle partitioning, transport and mixing, wet scavenging, and dry deposition. The special role of clouds and their impact on aerosols will be discussed. In addition, we will describe basic feedback mechanisms associated with radiation and clouds in which aerosols perturb meteorological conditions, that in turn, alter the evolution of aerosols. This talk will use examples from field studies measurements and modeling to illustrate the importance of meteorological conditions.

Bio: Dr. Fast obtained a Ph.D. in Meteorology from Iowa State University in 1990, has been a research scientist at Pacific Northwest National Laboratory since 1994, and became a Laboratory Fellow in 2018. He is currently principal investigator of the Integrated Cloud, Land-surface, and Aerosol System Study (ICLASS) science focus area supported by the U.S. Department of Energy’s (DOE) Atmospheric System Research (ASR) program that consists of ~30 scientists. Dr. Fast’s research interests and experience encompasses a wide range of atmospheric phenomena including: transport and dispersion processes, complex terrain circulations, boundary layer meteorology, mesoscale systems, trace gas and particulate chemistry, and aerosol-radiation-cloud interactions. He is an expert in developing, using, and interpreting atmospheric models to address key outstanding science questions associated with these atmospheric phenomena that are important for weather forecasting, air quality, and climate. While Dr. Fast is primarily a modeler, he has led and/or contributed to eight field campaigns since 1997, some of which had many participants from multiple agencies laboratories, and universities.

Bio: Dr. Mary Barth received her Ph.D. in Atmospheric Sciences from the University of Washington in 1991. She is a Senior Scientist at the National Center for Atmospheric Research with a joint appointment in the Atmospheric Chemistry Observations and Modeling (ACOM) Laboratory and Mesoscale and Microscale Meteorology (MMM) Laboratory. She heads the Multiscale Model Development Cross Cutting Group in ACOM that is developing the Multiscale Infrastructure for Chemistry and Aerosols (MUSICA) framework. Dr. Barth has served on a number of international steering committees and is currently a vice-president of the International Commission on Atmospheric Chemistry and Global Pollution. In 2017 she became a Fellow of the American Meteorological Society and currently serves as an editor for the AMS Journal of the Atmospheric Sciences. Throughout her career, Dr. Barth’s research focus has been on interactions between clouds and chemistry. She led the NSF/NASA Deep Convective Clouds and Chemistry field campaign, a multi-disciplinary study on storm dynamics, physics, lightning, and chemistry. Much of her recent research includes studies on convective transport of trace gases and aerosols, their scavenging by precipitation, and lightning production of nitrogen oxides. She has facilitated modeling studies on aerosol-cloud interactions in deep convection and in fog and led the evaluation of aqueous-phase chemistry modeling for a mountain-top cloud.

Abstract: Although it is known that multiphase chemistry in clouds/fogs is important in forming sulfate aerosols and creating acid rain events, it wasn’t clear until about 2 decades ago that multiphase chemistry plays a central role in aerosol processes (i.e., formation and evolution) in the troposphere.

The first half of the tutorial will discuss the types of analytical and experimental techniques used during this time that uncovered/characterized the importance of multiphase chemistry to aerosol processes. Some specific examples of multiphase chemical reactions to be discussed include acid-catalyzed, heterogeneous oxidation, and peroxide-based reactions. We will discuss how these reactions can lead to changes in measured aerosol physicochemical properties as well as discuss remaining measurement gaps.

The second half of this tutorial will also discuss the phase state (liquid vs. semisolid vs. glassy) of organic aerosols and its impacts on aerosol processes. The tutorial will also cover modeling multiphase aerosol processes by the resistor model and kinetic multilayer modeling approach by outlining key processes including diffusion, mass accommodation, and multiphase reactions.

Bio: Dr. Manabu Shiraiwa is an Associate Professor of Chemistry at University of California, Irvine. He received his Ph.D. at Max Planck Institute for Chemistry and had a postdoc training at California Institute of Technology. He is a recipient of the Sheldon K. Friedlander and Kenneth T. Whitby Awards for his research contributions.

Bio: Dr. Jason D. Surratt is a Professor of Environmental Sciences and Engineering and Chemistry at the University of North Carolina in Chapel Hill. He received B.A. and B.S. in chemistry and meteorology, respectively, from North Carolina State University in 2003. He received a Ph.D. in chemistry from the California Institute of Technology in 2010. He has served on AAAR’s Board of Directors, Particulars Newsletter Committee, and the Aerosol Chemistry Working Group. His research spans the fields of aerosol chemical characterization, multiphase (heterogeneous) chemistry of atmospheric aerosols, aerosol-related health effects, and more recently, characterization of emerging contaminants in aerosols. He has received the Sheldon K. Friedlander and Kenneth T. Whitby Awards from AAAR for his research contributions.

Abstract: The recent proliferation of low-cost aerosol and gas sensors has sparked much interest among the scientific community. Such devices show promise to enable measurements at unprecedented spatial and temporal scales, which, in turn, can lead to the creation of distributed sensor networks to support both traditional research and community-based research. With these exciting prospects, however, come challenges of sensor performance, sensor reliability, and data management. This tutorial will review basic principles of statistics and data science for real-time aerosol sensors, with a focus on low-cost (<$2,000) devices. Topics to be covered will include data management and cleaning, exploratory data analysis, linear models, troubleshooting techniques (and potential solutions), statistical issues relevant to time-series data (such as autocorrelation), and determination of analytic figures of merit (e.g., accuracy, bias, prevision, limit of detection). Participants need not have formal training in data science beforehand; self-help resources for learning basic data science in the R and MATLAB programming languages will be provided.

Bio: Dr. Josh Apte is an assistant professor in the Department of Civil and Environmental Engineering at the University of California, Berkeley. He studies human exposure to air pollution in the built environment to understand the relationships between emissions, atmospheric transformations, concentrations, human exposures and health effects. His work is interdisciplinary and draws methods from environmental engineering, aerosol science, exposure assessment, and environmental health, with the goal of applying these insights to designing healthy, energy-efficient, and sustainable cities for the world. His research on air pollution mapping using Google Street View Cars has won numerous awards and has garnered both national and international attention for impact. His paper “High-Resolution Air Pollution Mapping with Google Street View Cars: Exploiting Big Data” won the “Top Environmental Technology Paper” award from Environmental Science and Technology in 2017.

Bio: Dr. John Volckens is a professor of Mechanical Engineering and the Director of the Center for Energy Development and Health at Colorado State University (CSU). He holds affiliate appointments in Environmental Health, Biomedical Engineering, the Colorado School of Public Health, and the CSU Energy Institute. His research interests involve air quality, low-cost sensors, exposure science, and air pollution-related disease. He is a founding member of the CSU Partnership for Air Quality, Climate, and Health – an organization that seeks to develop practical, science-vetted solutions to intertwined problems of air quality, climate, and health that we face as a society. He holds a BS in Civil Engineering from the University of Vermont and MS, PhD degrees in Environmental Engineering from the School of Public Health at the University of North Carolina at Chapel Hill. He then went on to a Postdoctoral position at the U.S. EPA's National Exposure Research Laboratory in Research Triangle Park, NC. At CSU, he has pioneered the development of several new pollution sensor technologies, which have been deployed for public health research in over 30 different countries and as far away as the International Space Station. He has published over 100 manuscripts related to exposure science, aerosol technology, and air pollution-related disease.

Abstract: Despite the increasingly recognized role of the indoor environment in spreading pathogens, the mechanisms underlying environmental effects on the transmission of airborne bioparticles including viruses, bacteria and fungi remain poorly understood. The aerial path of pathogens from the source to recipients or surfaces and their survivability is determined by many factors. Heating, ventilation, and air conditioning (HVAC) systems not only provide a means of transport for infectious aerosols but also affect bioparticle resuspension and trigger resistance in pathogens by a largely unknown mechanism.

HVAC systems are often regarded to improve room sanitation by maintaining lower temperatures and clean airflow. Studies found that ventilation has a significant effect on the transmission of diseases and created optimized airflow patterns based on room design to minimize pathogen spread. However, aerosolized bioparticles entrained in the airflow may be transported from contaminated spaces to clean areas and impact on surfaces. Being airborne imposes osmotic and mechanical stress on bacteria that may trigger their defense mechanism. The resuspension of bioaerosols in ventilation airflow may change their behavior, including the infectivity of viruses. Therefore, it is critical to optimize the airflow patterns in facilities to minimize the entrainment of bioaerosols. Complex indoor/outdoor environments with critical obstructions can be modeled to track and mitigate the movement of bioaerosols that enter the air due to respiratory events or natural erosion and spread to nearby areas and communities. Based on the spatial and temporal knowledge gained through bioaerosol collection, analysis and computational airflow simulation, the facility layout and mechanical floorplan can be modified to control the transport and behavior of bioaerosols, opening new avenues for engineering to combat their spread. This workshop aims at filling the knowledge gap between ventilation airflow characteristics and bioaerosol distribution and transmission that would allow developing mitigation strategies to reduce the risk of airborne infections.

Dr. Maria King is Assistant Professor at the Department of Biological and Agricultural Engineering, and the Director of the Aerosol Technology Laboratory at Texas A&M University. She is an expert in the collection and analysis of aerosolized nano- and bioparticles, including viruses, bacteria and fungi, and the application of chemistry and molecular biology for real-time aerosol quantification and microbiome analysis. Her research focuses on using molecular dynamics design to delineate environmental factors that affect virus attachment and trigger the development of antibiotic resistance in bacteria and performing computational air flow modeling to reduce the resuspension and spread of pathogenic bacteria and infectious viruses in critical infrastructures. She has published numerous papers and book chapters and enjoys teaching the stacked graduate course “Bioaerosols and Modeling” and two core classes, “Thermodynamics” and “Fundamentals of Biological Engineering”.

Dr. Sunil Kumar is an Associate Research Scientist at the Department of Biological and Agricultural Engineering at Texas A&M University. He is an expert in the experimental and computational Heat and Mass Transfer, aerosol technologies, and drying of porous materials. He has simulated critical facilities such as hospital rooms, fabrication rooms of food processing facilities, and full-scale plants for characterizing contaminated droplets’ movement using Computational Fluid Dynamics (CFD). He investigated the use of low-flow air curtains and partitions to prevent the spreading of droplets and hence COVID-19. He has delivered numerous talks at conferences and invited talks. He has published papers on energy, phase change materials, and bioaerosols and enjoys teaching the graduate course “Bioaerosols and Modeling” for CFD modeling.

Abstract: This tutorial will enable the participants to get an "under the hood" look at a broad spectrum of currently available aerosol instruments. Whether you are an experimentalist, modeler, or both, this is an opportunity to learn how fundamental aerosol science principles are used in actual aerosol measurement technologies. Key capabilities, as well as limitations, of each technique will be described in order to instill a better appreciation of what different instruments can and cannot do. In this session, six aerosol instrumentation suppliers will present the concepts and engineering design processes that led to the successful development of different aerosol instruments. The tutorial is not a marketing and sales opportunity for participating vendors; this is an education session with an emphasis entirely on technology and the key physical concepts employed by the instruments. The goal is that by the end of the tutorial, participants no longer consider the instruments a "black box," but rather have some understanding of the principles and design consideration that went into the development of the various instruments. Furthermore, the information presented on measurement uncertainties and limitations will help the participants better interpret (avoid over-interpreting) measurement results.

Aethlabs – MA200 and MA350
The microAeth® MA200 is a compact, real-time, wearable 5-wavelength UV-IR Black Carbon monitor with a 17 sampling location automatic filter tape advance system, enabling up to 12 weeks of continuous measurements with low-power operation. The microAeth® MA350 is a real-time, 5-wavelength UV-IR Black Carbon monitor housed in an outdoor-rated case with an 85 sampling location automatic filter tape advance system, enabling up to 15 months of continuous measurements with low maintenance and infrequent site visits.

Brechtel – Miniature Scanning Electrical Mobility Sizer (mSEMS Model 9404)
The mSEMS provides fast electrical mobility-based aerosol number size distribution measurements in a compact package that can be deployed on UAVs, balloons, and other mobile platforms where space, weight and power are limited. The time response and size resolution of the device make it an ideal solution for studying transient aerosol populations in flow tubes, urban areas and other dynamic sampling situations.

Cooper Environmental/SCI – Xact 625i Ambient Metals Monitor
The Xact 625i Ambient Metals Monitor is a near real time monitor for monitoring metals and other elements in particulate matter (PM). The instrument utilizes X-ray Fluorescence (XRF) as an analytical technique and is capable of monitoring up to 67 different elements simultaneously.

Dekati Ltd. – Dekati® Oxidation Flow Reactor (DOFR™)
Dekati® Oxidation Flow Reactor (DOFR™) is a constant flow reactor designed for secondary aerosol formation studies. It brings the aging process that takes several days in the atmosphere to the timescale of just one minute.

Magee Scientific – Total Carbon Analyzer
The Total Carbon Analyzer collects the aerosol sample on a fixed quartz-fiber filter, and uses flash combustion into CO2 to measure the carbon content with time resolution as rapid as 20 minutes. When combined with the optical analysis of the Aethalometer®, this provides a complete real-time characterization of the carbonaceous component of ambient aerosols.

URG Corporation – Ambient Ion Monitor
The Ambient Ion Monitor is a scientifically-advanced, multi-pollutant monitoring method which allows for time resolved direct measurements of particle sulfate, nitrate, ammonium, chloride, potassium, magnesium, calcium, and sodium. This state-of-the-art real-time air sampling system has the ability to separate and analyze each ion individually.

Abstract: Understanding and predicting initiation of ice in clouds and its potential relation to the changing state of atmospheric aerosol composition remains as an enigmatic topic. Yet such knowledge and capabilities are critical to ultimately understanding and quantifying the role of aerosols and clouds in affecting clouds and climate. To be certain, advances are occurring in our knowledge. This tutorial will rather broadly review present understanding of ice formation by atmospheric aerosols. Emphasis will be on techniques for measuring ice nucleating particles (INPs), current understanding of INP sources and distribution, how ice nucleation processes are conceptualized and treated for use in numerical modeling of clouds and climate, and future challenges and directions.

Bio: Dr. Paul DeMott is a Senior Research Scientist in the Department of Atmospheric Science at Colorado State University. He received his B.S. degree in Atmospheric Sciences at the State University of New York University at Albany, and his M.S. and Ph.D. degrees in Atmospheric Science from Colorado State University. His current research involves development and application of laboratory and atmospheric measurements to understand the ice nucleation properties of particles of natural and anthropogenic origin.

Abstract: Models for simulating atmospheric aerosols are a key component of air quality simulations, as well as regional and global climate models. Developing aerosol models is a challenging task because of the complexity of the many different particle types in the atmosphere and their changes in physical and chemical properties during transport. Tracking these changes is important since they determine aerosol impacts on weather, climate, and human health, but it is not always clear how much detail needs to be included. This tutorial will provide an overview of how this challenge has been tackled by our research community. We will start out with a discussion of the aerosol life cycle and how the relevant processes are formulated as governing equations. We will then compare and contrast three different approaches of numerical discretization commonly used in state-of-the-art atmospheric aerosol modeling applications---modal, sectional, and particle-resolved techniques---highlighting their assumptions, strengths, and weaknesses. Finally, we will discuss strategies for model verification and validation, and ways to deal with structural and parametric model uncertainty.

Bio: Dr. Nicole Riemer is a Professor at the Department of Atmospheric Sciences and an Affiliate of the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Champaign. She received her Doctorate degree in Meteorology from the University of Karlsruhe, Germany. Her research focus is the development of computer simulations that describe how aerosol particles are created, transported, and transformed in the atmosphere. Her group uses these simulations, together with observational and satellite data, to understand how aerosol particles impact human health, weather, and climate. Nicole Riemer received the NSF CAREER award and the AGU Ascent award. She is an editor for Aerosol Science & Technology and Journal of Geophysical Research.

Abstract: Many flame-based processes produce particles that are either pollutant by-products, primarily in the form of a carbonaceous material (i.e., soot) or engineered materials synthesized with tailored properties for commercialization (e.g., carbon black, titanium dioxide, fumed silica, etc.). Consequently, the unraveling of the mechanisms that lead a fraction of the gaseous reactants to pyrolyze and transition to particles is not only crucial from a fundamental perspective but has also substantial practical impacts.

The multiscale details of the physics and chemistry at play behind the formation of particles in flames have been at the forefront of scientific research for hundreds of years and continue to be of high relevance in the 21st century. Indeed, much work is still needed because particle nucleation occurs rapidly and, equivalently, in narrow spatial regions with relatively steep gradients and encompasses ranges of sizes and masses that are so broad that several complimentary sampling and analysis techniques are necessary to investigate it with the necessary spatial resolution and to figure out the biases in the results of each technique that may limit our fundamental understanding.

This tutorial reviews a variety of experimental methods to inquire both the growth chemistry of the gas phase, the clustering of gas molecules, and the physics of the aerosol in the nanometric dimensional scale of relevance to particle nucleation. Several sampling and analysis techniques will be presented accompanied by an overview of the type of results that they can provide and, in some instances, by the results of simple modeling. The discussion will be focused on highlighting the advantages and limitations of each technique in terms of the achievable spatial resolution, perturbation of the source flame, and occurrence and extent of sample modifications before the analysis is performed. The probing methods to be discussed will include in-situ optical diagnostics and capillary, dilution, and thermophoretic sampling. The discussion will also touch upon the implementation of the pre-analysis ionization/charging and its effects on the results of Gas Chromatographic, Mass Spectrometric, Microscopy, and Ion/Particle Mobility analyses. The methods described herein can bring to the fore problems in established beliefs and contribute to shed light on particle nucleation in flames and, more broadly, high-temperature reacting flows.

Bio: Francesco Carbone joined the Department of Mechanical Engineering at the University of Connecticut as an Assistant in Fall 2109 after serving at Yale University in the Department of Mechanical Engineering and Materials Science as Research Faculty from 2014 to 2019 as well as Lecturer in 2018. He held research positions also in the Department of Aerospace and Mechanical Engineering at the University of Southern California from 2012 to 2014, in the Department of Mechanical Engineering at Yale University from 2010 to 2012, and in the Combustion Research Institute at the Italian National Research Council from 2008 to 2010. Francesco earned his M.Sc. in Mechanical Engineering and his Ph.D. in Chemical Engineering from the University of Naples Federico II (Italy) in 2005 and 2008, respectively. His research in the combustion, aerosols, and nanoparticle synthesis fields encompasses aspects of transport phenomena and reaction kinetics and is relevant for advancing energy systems and mitigating their environmental impact. Dr. Carbone develops experimental approaches to interrogate the physics and chemistry of flames and their aerosol products but also leverages theory and computational tools to interpret the experimental results. He authored more than thirty articles published in prominent peer-reviewed journals in the fields of combustion and aerosols. The primary focus of his published work is on the formation mechanisms of nanoparticles in flames that are eventually emitted in the atmosphere by combustion devices.

Abstract: Quantifying aerosol exposure is important for many applications, including supporting epidemiology studies, risk assessments, development of mitigation strategies, and sustainability efforts for cities and communities. This tutorial will review current measurement and modeling methods for estimating aerosol exposure in non-industrial indoor and in-cabin microenvironments, such as homes, schools, hospitals, commercial buildings, and vehicles. In this tutorial, we will discuss existing as well as promising future approaches for quantifying aerosol exposure.

Bio: Dr. Andrea Ferro is a professor of Civil and Environmental Engineering at Clarkson University, the Clarkson Institute for a Sustainable Environment Associate Director for Research, a faculty affiliate of the Clarkson Center for Air and Aquatic Resources Engineering and Science (CAARES), and the immediate past president of AAAR. Her technical expertise is focused on indoor air quality and human exposure to aerosols. She has worked directly with communities, schools, and hospitals and to measure, understand and mitigate sources of PM exposure. She has been conducting research in the field of particle resuspension for more than 20 years, including measurement and modeling of particle adhesion, detachment and transport at multiple scales, as well as the quantification of human exposure to resuspended particles for various exposure scenarios.

Andrea and Phil are co-authors of a chapter entitled “Fundamentals of Exposure Science” in the soon to be published Zhang, Hopke and Mandin, eds-in-chief., Handbook of Indoor Air Quality: Chemical Pollutants, Springer Publishing Company, New York, NY.

Bio: Dr. Philip K. Hopke is the Bayard D. Clarkson Distinguished Professor Emeritus at Clarkson University and Adjunct Professor in the Department of Public Health Sciences of the University of Rochester School of Medicine and Dentistry. He was the founding Director of the Center for Air Resources Engineering and Science (CARES), and the Director of the Institute for a Sustainable Environment (ISE). He has been studying indoor and ambient air pollution for more than 50 years. His research interests: Chemical characterization of ambient aerosol samples; Multivariate statistical methods for data analysis; Emissions and properties of solid biomass combustion systems; Characterization of source/receptor relationships for ambient air pollutants; Experimental studies of homogeneous, heterogeneous, and ion-induced nucleation; Indoor air quality; Exposure and risk assessment.

Andrea and Phil are co-authors of a chapter entitled “Fundamentals of Exposure Science” in the soon to be published Zhang, Hopke and Mandin, eds-in-chief., Handbook of Indoor Air Quality: Chemical Pollutants, Springer Publishing Company, New York, NY.

Abstract: This tutorial will enable the participants to get an "under the hood" look at a broad spectrum of currently available aerosol instruments. Whether you are an experimentalist, modeler, or both, this is an opportunity to learn how fundamental aerosol science principles are used in actual aerosol measurement technologies. Key capabilities, as well as limitations, of each technique will be described in order to instill a better appreciation of what different instruments can and cannot do. In this session, six aerosol instrumentation suppliers will present the concepts and engineering design processes that led to the successful development of different aerosol instruments. The tutorial is not a marketing and sales opportunity for participating vendors; this is an education session with an emphasis entirely on technology and the key physical concepts employed by the instruments. The goal is that by the end of the tutorial, participants no longer consider the instruments a "black box," but rather have some understanding of the principles and design consideration that went into the development of the various instruments. Furthermore, the information presented on measurement uncertainties and limitations will help the participants better interpret (avoid over-interpreting) measurement results.

Aerosol Devices – BioSpot-GEM
The BioSpot-GEM™ bioaerosol sampler was designed for easy and portable sampling of bioaerosol particles, and collects all particles between <10 nm and 10 micron with high efficiency using the proprietary condensation growth capture method. In this tutorial, we will demonstrate how this instrument can be used in field research applications, industrial hygiene uses as well as a companion product for our research grade samplers.

Cambustion – M2AS
The Cambustion Mass and Mobility Aerosol Spectrometer (M2AS) is a novel technique for measurement of aerosol mass, mobility and density; finally enabling efficient and accurate characterisation of agglomerate aerosols.

CH Technologies – RespAer-Meter and Partector 2
The Naneos Partector 2 is a revolutionary, hand-held, diffusion-charging nanoparticle monitor which measures Lung Deposited Surface Area (LDSA), Particle Number and Particle Size. The Palas Resp-Aer-Meter is an Optical Aerosol Spectrometer designed to quantify human breath particulate emissions in terms of their Particle Number and Particle Size.

QuantAQ – MODULAIR and MODULAIR-PM Sensors – Aerosol Exposure System with SmartStudy
DSI’s inhalation system can now close a single port in a nose-only inhalation system, while still aerosolizing the rest. This long sought after capability allows the user unseen before lung dosing precision to multiple subjects, all within the simple to use automated user interface.

Durag Group (Grimm) – 11-D Spectrometer & SMPS+C Model 5416
DURAG’s Grimm 11-D is a handheld laser aerosol spectrometer to determine particle number & size distribution as well as 12 different mass fractions. The Grimm SMPS+C is a Scanning Mobility Particle Sizer with Condensation Particle Counter (Model 5416) for recording particle size distributions from 10-1094 nm.

TSI – Scanning Mobility Particle Sizer™ with Differential Mobility Analyzer, Sampling System for Atmospheric Particles, and Aerosol Diluter
TSI® will showcase the Scanning Mobility Particle Sizer™ (SMPS™) spectrometer equipped with the new wide-range Differential Mobility Analyzer (DMA) 3083, which enables covering 10 nm to 800 nm in a single scan. Additionally, TSI® will demonstrate the new Sampling System for Atmospheric Particles 3750200 and Aerosol Diluter 3333-10, accessories designed to work perfectly in concert with the SMPS™ for long-term continuous ambient monitoring of ultrafine particles.