Aircraft Sampling

Ground-based measurements of aerosol properties are very useful but to validate their models climate modelers also need information about how aerosol properties change at higher levels in our atmosphere. Without validated climate models the uncertainties in our predictions of future climate change will remain high. At Brechtel, we are making a commitment to provide the key sampling tools, like isokinetic and counterflow virtual impactor aircraft sampling inlets, so scientists can take the high quality data they need to validate their models and test their hypotheses.

Aircraft Sampling-SEMS

The Brechtel Scanning Electrical Mobility Sizer (SEMS, see Lopez-Yglesias et al. (2014) Aer. Sci. & Tech.) was used on-board the Environment Canada Convair 580 research aircraft to perform rapid 40 second size scans between 20 and 100 nm during vertical profiles to 9,500 feet. The SEMS performed very well with no down time over the three weeks of intensive flights performed from Resolute Bay, Nunavut (Alaska). The vertical profile data from the SEMS captured particle production and growth events that were a primary focus of the research.

Richard Leaitch, Ph.D.
Research Scientist, Science and Technology Branch
Environment Canada

Air Quality Monitoring

The health impacts of ultrafine (or nano-) particles are still poorly understood. The very smallest particles are thought to pass through the walls of the human respiratory system and pass into the blood stream, where they can damage the nervous system. Particles smaller than 100 nanometers are difficult to measure since they are too small to be directly detected by light scattering techniques.

Brechtel’s Mixing-based Condensation Particle Counter (MCPC) has been successfully deployed in southern California over a 3 month period to monitor nanoparticle concentrations near an extremely busy freeway in collaboration with the South Coast Air Quality Monitoring District.  The measurement results indicated very high concentrations, often above several hundred thousand particles per cubic centimeter.  The goal of the measurements was to assess the nanoparticle exposure to people living near the freeway.

Calibration Standards

The Brechtel Scanning Electrical Mobility Sizer (SEMS, see Lopez-Yglesias et al. (2014) Aer. Sci. & Tech.; Leaitch et al. (2013) Elementa: Science of the Anthropocene) was used for more than a two year period during 2010 to 2012 at the Alert, Alaska Global Aerosol Watch station to generate monodisperse calibration aerosols. The generated particles were used to challenge and test a competitor’s scanning mobility particle sizer system as well as to calibrate an Aerodyne Research Inc. Aerosol Chemical Speciation Monitor (ACSM) using monodisperse nitrate particles. A major focus of the measurements was to determine the conditions under which new particles were formed at the site. The SEMS played a key role in validating the sizing performance of other instruments and worked very well over the entire period.

Richard Leaitch, Ph.D.
Research Scientist, Science and Technology Branch
Environment Canada

Dr. Radovan Krejci in the Department of Applied Environmental Science (ITM) of Stockholm University deployed Brechtel Model 1205 Ground-CVI from during the Cloud and Aerosol Experiment Åre (CEASAR) from July to October 2014. This was the first field deployment of the GCVI. The measurements were made at 1200 MSL on top of Mt. Åreskutan, within the famous Swedish ski resort Åre.

The project is focused on aerosol-cloud interactions and contrasting clean marine air masses with air influenced by terrestrial boreal forest biogenic emissions and anthropogenically influenced European air masses.  Special attention is being paid in the data analysis to partitioning of absorbing aerosol between interstitial aerosol and cloud droplets as well as aerosol removal processes. The project is a collaboration between ITM, the Finnish Meteorological Institute and the Paul Scherrer Institute. During the experiment several hundred hours of aerosol and cloud microphysical data have been collected, including key properties of the dried cloud residual CCN from the GCVI.

GCVI CCN Res 20140709_CESAR2014_013

GCVI CCN Res 20140708_CESAR2014_000

GCVI CCN Res 20140709_CESAR2014_014

Climate Impacts

Most of us know about the global warming caused when CO2 and other green-house gases absorb the sun’s energy and then re-emit that energy as heat that warms the air. Airborne particles also interact with the sun’s energy and influence our climate in two major ways: first by directly blocking the sun’s energy from reaching the Earth’s surface and second by acting as the seeds for cloud droplets and changing how reflective clouds are to the sun’s energy.

In the Earth’s atmosphere, each cloud is made up of thousands to billions of tiny droplets and each drop had to originally form on a seed particle by the condensation of water vapor. Clouds that have more numerous smaller drops tend to be more reflective to the sun’s energy – as we emit more particles that can act as cloud droplet seeds, there is a chance that we will make clouds more reflective resulting in a cooling effect on climate.

On the face of it this may sound like a good thing – with the worry about global warming by CO2, some global cooling would seem to work in our favor. Unfortunately, the average lifetime of a particle in the atmosphere before it is removed by rain is thought to be only around two weeks, while that for a typical CO2 molecule is five years. In two weeks a particle emitted into the air in San Francisco will travel (on average) all the way to New York, likely participating in several cloud formation and evaporation cycles along the way before it falls to the ground inside a rain drop. This means that the cooling effect on climate caused by particles acting as cloud droplet seeds will likely be greatest over the areas immediately downwind of large sources of particles, like power plants, industrial activities and major urban areas. The end result is that the cooling effects of particles are likely to be limited to certain ‘continental scale’ areas while the warming effects of green-house gases are distributed more uniformly over the entire globe.

Through the development of miniaturized and cost-effective particle measurement technologies like the ACCESS, Brechtel is helping to supply the tools required by climate scientists to better understand the roles of particles in our future climate.

Climate Monitoring

Global climate change will likely be the defining issue of the twenty-first century. Although most of us know about the warming by CO2, fewer people are aware that airborne particles can also alter climate by interacting with the sun’s energy. Particles can cool climate by directly blocking the sun’s energy from reaching the Earth’s surface. They can also affect climate by acting as the seeds for cloud droplets and changing how reflective clouds are to the sun’s energy. It turns out that where in the atmosphere particles act as cloud seeds determines whether the altered cloud will have a cooling or a warming effect on climate.

Scientists at the National Oceanic and Atmospheric Administration have established a network of Global Aerosol Watch (GAW) stations to monitor changing particle properties in the atmosphere so climate modelers can better simulate our changing climate.

To monitor the total concentration of airborne particles they turned to Brechtel to provide a reliable particle counter solution that could be deployed for years at their remote GAW stations.

Through the development of ruggedized and cost-effective particle concentration measurement technologies like the Mixing Condensation Particle Counter (MCPC), Brechtel is helping to supply the tools required by climate scientists to better understand the roles of particles in our future climate.

Health Impacts

Airborne particles impact human health when we inhale them and they penetrate deep into the lung. Especially small particles can damage the human nervous system when they pass through the air-blood boundary of the lung and hitch a ride on our circulatory system until they deposit at a nerve ending, where they can ‘short-circuit’ the nerve. Soot (black carbon) particles with small bits of metal (from combustion engines) are especially worrisome as the very smallest nodules of soot are small enough to get into the nervous system through the process described above. Brechtel has developed the Tricolor Absorption Photometer (TAP) to measure soot in an easy-to-use, cost effective and compact package.

Current particulate matter (PM) standards for health are based on total mass rather than specific chemical species concentrations like soot because 1) mass is easy to measure, and 2) chemistry measurements are relatively expensive, not robust enough for routine monitoring applications and require a high degree of operator expertise. Recent research indicates that chemical composition, and not total mass, dictates a particle’s impact on human health. Brechtel developed the TAP to make it easier to measure soot without requiring a highly trained operator.

Pope (2004) found that exposure to particles of a certain size, for example, smaller than 0.1um, may also control the health impacts of PM. Particles in this size range tend to be dominated by sulfur, organic and nitrogen-containing species, as well as soot. These smaller particles also tend to dominate the cloud condensation nucleus (CCN) sub-population of the ambient aerosol that serves as the nuclei for all cloud drops in the Earth’s atmosphere.

In order to fully assess the impacts of aerosols on human health, epidemiologists require new measurement tools that can be deployed at not a few, but hundreds, of sampling locations. Measurement techniques must be repeatable, insensitive to operator expertise, and robust when deployed in the field. Indeed, the lack of consensus among health experts regarding PM health effects is partially due to the limited amount of available size-resolved and chemical species-resolved ambient aerosol data. The TAP is a small, field-robust instrument capable of network deployment that can satisfy new study needs.

Until large-scale datasets of nanoparticle (smaller than 0.1um) and fine-particle (smaller than 1um) number concentration size distribution and chemical composition are readily available over regional scales, it will be extremely difficult to elucidate their potential human health impacts.

Hong Kong Air Quality

The Brechtel Humidified Tandem Differential Mobility Analyzer (HTDMA, see Lopez-Yglesias et al. (2014) Aer. Sci. & Tech.) and a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS) were used to study the impact of air mass origins on the hygroscopic growth of aerosol at the Hong Kong University of Science and Technology Supersite, located at a coastal suburban site in Hong Kong. Particle water uptake at 90% relative humidity showed a clear decrease when the air mass changed from maritime or coastal to continental with corresponding increases observed in the aerosol organic loading. The HTDMA allowed rapid and continuous water uptake measurements to be made in the field so that correlations with changes in chemical composition could be explored with fine detail (see M. C. Yeung et al (2014) JGR) for more detail.

Chak K. Chan, Ph.D.
Professor, Dept. of Chemical and Biomolecular Engineering
Hong Kong University of Science and Technology

Ice Nuclei Research – PCVI

A unique deployment of the PCVI involves coupling it to a new ice nucleation chamber as well as a cloud condensation nucleus counter CCN (see Hiranuma et al. (2011) AMTD reference). Ice nuclei, particles that can form ice crystals in cirrus and other cold-temperature clouds, are poorly understood in our atmosphere but have important climate impacts. Tools like the PCVI allow careful studies of particle ice nucleating properties as a function of particle size.

Dan Cziczo
Professor of Chemistry
MIT Program in Atmospheres, Oceans and Climate

Ice Nuclei Research – SEMS

We use the SEMS as a means to prepare aerosol for our cloud chamber experiments. The ability of the SEMS to separate based on mobility allows us to take one of the variables we find in the atmosphere – particulate size – out of the equations. When particles are then ‘activated’ into droplets or ice crystals we can interpret the results as due to composition or morphology without the task of decoupling particle volume or surface area (see Hiranuma et al. (2011) AMTD reference).

Dan Cziczo
Professor of Chemistry
MIT Program in Atmospheres, Oceans and Climate

Why is ice in the Arctic melting so quickly? Why are glaciers around the world shrinking at such a high rate? These and other climate change-related questions need to be answered using measurements that can be deployed in more places and at lower cost. Inexpensive, long-term measurements are especially necessary high in the atmosphere so that climate models can be validated. Currently, 99+% of all measurements are performed at the Earth’s surface and usually don’t represent what’s happening higher in the atmosphere.

At Brechtel, we are working on miniaturized instruments to measure pollutants from Unmanned Aerial Vehicles (UAVs) so that measurements can be made inexpensively, even in very remote locations. The US Department of Energy has funded us under the Small Business Innovation Research (SBIR) program to develop small instruments that measure airborne particle physical, chemical and optical properties. Black carbon is one especially important species we’ve targeted due to its large global biomass burning source.

Through the development of miniaturized and cost-effective particle measurement technologies like the ACCESS, Brechtel is helping climate scientists better understand the roles particles play in our climate.

Click below to view a video describing a UAV application where we helped NOAA scientists measure black carbon in the Arctic.

  • My group has used the Brechtel CVI inlet on-board research aircraft extensively to explore the CCN properties of stratocumulus clouds off the coast of California with great success. Intercomparisons of the cloud drop concentrations measured by wing-mounted optical sizing probes and the CCN number concentrations measured at the same time by a condensation particle counter deployed on the CVI sample flow showed excellent agreement, in part because Brechtel dedicated the effort to characterize the drop size dependent losses in their system. Working with Brechtel over the years, they have consistently demonstrated their commitment to quality and customer service.

    Dr. Armin Sorooshian Assistant Professor, Chemical and Environmental Engineering
    University of Arizona