by Bonne Ford

In recent years, we have seen an uptick in large wildfires and smoke events. As the climate continues to get hotter and drier in many places in the West (conditions that are more conducive to starting and spreading wildfires) and the fire season lengthens, we expect this trend to continue. Many ecosystems depend on fire, and fires can be a natural part of a forest’s lifecycle. However, to protect life and property, for much of the last century, the focus was on suppressing fires. This allowed fuels to build up across the U.S.; thus, once fires get started, there is still lots of fuel to burn and keep feeding the fires. We are seeing the number of fire ignitions also increasing, both from natural (lightning) and humans. As more people are moving into the wildland urban interface (WUI) and interacting more with forested lands, fire incidences increase.

In addition to the threat of the fire itself (to life and property destruction), wildfires are also a significant source of PM_2.5in the U.S. Regulations have helped to reduce many other emission sources (like from automobiles and industry), and wildfire emissions are now a dominant source of the primary PM_2.5 emissions in the U.S. Some models project that this wildfire emission source could continue to increase and offset many of the PM_2.5 air quality improvements we have made in the U.S.

We hear about the large fires in the western U.S., but fires occur throughout the U.S. Generally, fires in the East are smaller. There are also more agricultural and prescribed burns in the Southeast and Midwest. These smaller fires produce less smoke but may occur more frequently. While we generally think of the risk of large fires as primarily occurring in the West, the smoke from these wildfires can travel long distances and impact the rest of the U.S. The past few years we have seen significant smoke events in Canada and the western U.S. that have blanketed much of the continental U.S. with heavy smoke.

Our 2021 SARP student measurements caught some of these smoke events. We saw smoke from fires in Canada and the western U.S. impact the air quality at our measurement sites all over the Midwest and eastern U.S. this summer.

Below is a figure showing the extent of the smoke plumes from a satellite analysis product, the Hazard Mapping System (HMS) Fire and Smoke Product. These show smoke plumes on 21-23 July 2021. The red triangles are locations of fires, and the gray polygons are outlines of smoke (the darker gray represents thicker smoke). On the 21^st, we see thick smoke all along the eastern coast. The smoke decreases over the next few days, and the plumes are shifted more through the Midwest and into the southeastern U.S.

If we look at time series of PM_2.5 concentrations (uncorrected values from the AMOD's Plantower sensor) at a few of our SARP locations, we can see that surface concentrations were elevated during this week compared to the previous week (July 13-18, 2021). The higher concentrations coincide with days with smoke. For example, the site in New York has the highest concentrations on the 20^thand 21^st, while the site in Georgia has the highest concentrations on the 23^rd.

We can also see the enhancement in AOD. The plot below shows AOD measurements from two of the SARP locations on the east coast: New York and Rhode Island. They have similar magnitudes in AOD, but when you compare back to the surface PM_2.5 concentrations, the New York site has much higher surface concentrations. This could suggest that more smoke is aloft than at the surface.

For those in SARP this year, you can log into the website (csu-ceams.com) and check out your data to see where your sensor falls for this past week. If you need a reminder, here's a video tutorial on how to interact on the website: https://youtu.be/PSgawuwMBQk

Have you thought about comparing your site with the nearest EPA measurements? You can check out the air quality on their Interactive Map of Air Quality Monitors: https://www.epa.gov/outdoor-air-quality-data/interactive-map-air-quality-monitors

By Jeff Pierce

In our earlier blog post, “What are our devices measuring and why?”, we discussed that satellites do not directly measure values of fine particulate matter (PM2.5), but rather satellites retrieve a property called aerosol optical depth (AOD). Our CEAMS measurements of both PM2.5 and AOD help us understand typical ratios of PM2.5:AOD, which can be used to convert satellite-retrieved AOD to surface PM2.5.

AOD is measured from several NASA satellite instruments, including two Moderate Resolution Imaging Spectroradiometer (MODIS) instruments on the Terra and Aqua satellites, the Multi-angle Imaging SpectroRadiometer (MISR) on the Terra satellite, and the Visible Infrared Imaging Radiometer Suite (VIIRS) instrument on the Suomi NPP satellite. These instruments measure the amount of radiation reflected by the Earth in visible and near infrared wavelengths, which can be used to retrieve AOD when/where there are no clouds in the atmosphere.

NASA Worldview is a great tool to visualize satellite-retrieved AOD. To view AOD on the map:

• Click on the red “+ Add Layers” button on the left, then click on “Aerosol Optical Depth” under “Air Quality”.
• There are many AOD options to choose from, but for now click on “Terra/MODIS” and then “Merged DT/DB Aerosol Optical Depth (Land and Ocean)”, which will give the most complete picture of AOD for the current day. (Note that if you’re doing this early in the day, Terra may not have made a measurement over your location yet, so switch to yesterday using the date selectors on the bottom left.)
• Exit the layers menu (the x in the top-right corner of the menu).
• I like to click on the eyeball for “Place Labels” and “Coastlines / Borders / Roads”, and then I drag AOD to the bottom of this list, so I can see place locations more easily.
• You can easily toggle through different years, months, and days on the bottom left.

Can you visualize the AOD over the time period of your measurements? Were there days where AOD was higher? Play around to see what other layers you can add.

By Michael Cheeseman

In partnership with the NASA SARP program and the participation of students all around the US, the CEAMS network of coincident PM2.5 and AOD sensors (known as the Aerosol Mass and Optical Depth [AMOD] sampler) are capturing interesting atmospheric phenomena throughout the summer of 2020. Below I present an example of SARP participants capturing the shifting ambient conditions of particulate matter over the Northern Colorado Front Range. During a series of fires occurring in Arizona, we observe an enhancement of surface level PM2.5 near Denver and Fort Collins, CO (Figure 1 and 2, left). Then we see a sharp decrease in mean daytime PM2.5 (Figure 1, right) likely due to a shift in winds that carried clean air over Northern Colorado (Figure 2, right). The time series of the real-time PM2.5 (Figure 3) reveals correlated PM2.5 measurements in the Front Range as smoke begins to impact local air quality, followed by a sharp decrease as the wind likely shifts smoke away from the area.

There were two major fires that were captured here--the Magnum Fire and the Bush Fire. As seen in Figure 2 (right), the smaller plume coming from north central Arizona was the Magnum fire, and the larger plume from the southwest was the Bush Fire.

The Magnum Fire started on Monday June 8, 2020 in the afternoon, 30 miles south of Fredonia, AZ. This wildfire was closer to being contained in the first couple days of the fire due to low winds, but the winds intensified.  With this intensification, red flag winds aided in the fire's growth. Locals were seeing poor air quality as early as June 14, 2020. The Magnum fire continued to be fueled by sage-grassland, growing larger and more of a potential threat to the area. This fire led to the closure of US 89A and SR 67, closing off the North Rim of Grand Canyon National Park to the public. Additionally, evacuations were issued for areas along House Rock Road east of Jacob Lake on June 17. The smoke plumes shown on June 17 and 18 (Figure 2) show the magnitude of the first on the first two days of evacuations, giving us an interesting view into the sheer size of the fire. At its final containment on July 27,2020, the Magnum fire ultimately burned 71,450 acres.

The Bush fire was a human-caused wildfire during this time period, starting on June 13, 2020 from brush on the side of the road that ignited from a vehicle. This fire started in the Tonto National Forest northeast of Phoenix, Arizona. The Bush fire grew immense quickly, and was difficult to contain. Notably in our June 17 and 18 time period, the Bush fire had burned 25,882 acres overnight, at an overall 5% containment for both days. At this time period, the Bush fire was the largest active fire in the United States. Six areas were issued evacuation orders between June 16 and 18, showcasing the magnitude of this fire during early in its lifetime. At its containment on July 6, 2020, 193,455 acres were burned.

Capturing these wildfires with our samplers is valuable to compare with satellites. NOAA/NASA’s Suomi NPP satellite, for example, captures images of these fires that are used by the many different sectors that work on fire mitigation and management. In this time period of June 2020, six active wildfires across Arizona and New Mexico could be seen from the satellites. We are excited that our network could capture two of the major plumes' transported smoke in Colorado.

If you want to learn more about the active fires at this time, as well as the satellites that can see them, please check out this article from NASA, as well as the hyperlinks throughout this blog:

https://blogs.nasa.gov/firesandsmoke/2020/06/23/multiple-fires-stretch-across-arizona-and-new-mexico/

By Zoey Rosen

Poor air quality days are a problem. Not all air quality problems are the same though! There are different types of air pollution--like particulate pollution or ozone pollution--even if they come from similar point sources. Knowing the difference between the types can help you understand your risk, and learn more about what’s going on in the air above you.

What is particulate pollution?

Particulate pollution is when small, hazardous particles are spread throughout the air. These particles range in size (from PM2.5 to PM10), and can be from a natural or industrial sources. Soot from fires, dust, factory debris, and fossil fuel emissions are examples of particulate matter (PM) that contribute to poor air quality. PM is a threat all year, not just “fire season.”

Man-made and natural sources of PM are known as primary PM sources. A secondary PM source is a source that directly emits vapors and chemical compounds into the air, that form or help form PM. These compounds are as volatile organic compounds (VOCs), sulfur oxides, ammonia, or Nitrogen oxides. Once in the air, these compounds can lead to chemical reactions that have a different effect on air pollution.

What is ozone pollution?

Ozone pollution happens when sunlight reacts with VOCs or Nitrogen oxides in the air. This chemical reaction often removes an oxygen atom from the compounds, which bonds with the oxygen (O2) in the air. Common at the ground-level and in higher altitude locations, ozone pollution has a greater risk in the summer, when there are higher temperatures.

How does this affect our health?

Breathing in particulate matter can be harmful to your health. The small particles can lead to problems with breathing, like with asthma, or cardiovascular issues, like heart attacks. Ozone has a similar effect on breathing issues, leading to irritation of the throat, asthma, or lung disease.

Both PM and ozone pollution are hard to see, and must be taken seriously. While you can see a haze sometimes for PM pollution, ozone is harder to notice without Air Quality (AQ) alerts. The negative health effects of both types of pollution can be avoided by taking the proper measures to protect you and your family.

By Christian L'Orange

The number and intensity of wildfires in the United States has increased in recent years. An average of ~7 million acres a year have burned since 2000, which is double the rate than between 1990-2000 (1). These wildfires pose great danger to people, wildlife, and structures, but also release harmful pollutants. High temperatures from wildfires and strong winds can result in pollutants being transported, literally, around the world (2). Figure 1 is a good example of how = far that smoke can travel.

Wildfires are the single largest source of smoke emitted into the atmosphere every year (4). Wildfires release gases and particles that can reduce visibility and harm the health of both us and the environment. Exposure to smoke can have both short-term and long-term health effects. Short-term exposure can lead to chest pain, shortness of breath, and eye irritation (5). Long-term exposure has been linked to bronchitis, asthma, and high blood pressure (6,7, 8).

Although it can be challenging to avoid exposure to wildfire smoke completely, you can take a few simple steps to reduce the health risks of smoke exposure and feel better during wildfire season:

• Home Filters: Make sure your home furnace and air conditioning system have a high efficiency particle air (HEPA) filter. Ideally, this HEPA filter should have a MERV rating of at least 13. A MERV rating is a measure of what size particles a filter can capture. The higher the number, the better the filter is at getting rid of small particles. Portable air cleaners with these filters can further improve the air quality in your home (9). Make sure the portable air filter you choose is appropriate for the room size. Bedrooms and living rooms are the best locations for these extra filters.
• Reduce Your  Exposure: Although it’s tempting to enjoy the outdoors when the weather is nice, try to limit the amount of time you are exposed to  wildfire smoke. This can be as simple as keeping your doors and windows closed (as long as you have clean indoor air) and skipping outdoor activities when air pollution levels are particularly high.
• Personal Air Filter: You can wear a facemask when you are outside. When purchasing these masks, look for a rating of N95 or higher. A simple dust mask or surgical mask is not enough; these masks can’t filter out the extremely small particles coming from wildfires (1). Facemasks need to be properly fitting and should have double straps; they will not work for children or men with beards.

Sources:

1. “Wildfire Statics.” Congressional Research Service. November 16 2018. URL: https://fas.org/sgp/crs/misc/IF10244.pdf. Accessed February 08 2019.
2. Martin, M. Val, et al. "Smoke injection heights from fires in North America: analysis of 5 years of satellite observations." Atmospheric Chemistry & Physics 10.4 (2010).
3. NOAA. High-Resolution Rapid Refresh Model. URL: https://rapidrefresh.noaa.gov/hrrr/HRRRsmoke. Accessed Feb 15, 2019.
4. Scott Paper
5. “Health Recommendations for Wildfire Smoke.” National Jewish Health. URL: https://www.nationaljewish.org/health-insights/air-pollution-and-healthy-homes/wildfire-smoke. Accessed February 08 2019.
6. Cohen, Aaron J., et al. "The global burden of disease due to outdoor air pollution." Journal of Toxicology and Environmental Health, Part A 68.13-14 (2005): 1301-1307.
7. Brook, Robert D., et al. "Air pollution and cardiovascular disease: a statement for healthcare professionals from the Expert Panel on Population and Prevention Science of the American Heart Association." Circulation 109.21 (2004): 2655-2671.
8. Pope III, C. Arden, et al. "Cardiovascular mortality and long-term exposure to particulate air pollution: epidemiological evidence of general pathophysiological pathways of disease." Circulation 109.1 (2004): 71-77.
9. “Guide to Air Cleaners in the Home.” United States Environmental Protection Agency. EPA-402-F-08-004.
10. “Masks and N95 Respirators.” US Food and Drug Administration. URL: https://www.fda.gov/MedicalDevices/ProductsandMedicalProcedures/GeneralHospitalDevicesandSupplies/PersonalProtectiveEquipment/ucm055977.htm. Accessed February 08 2019.

By Zoey Rosen

Simply stated, the Air Quality Index (AQI) is a scale used for reporting air quality levels. In the United States, the Environmental Protection Agency (EPA) established this index to connect air pollution levels to human health effects

The AQI ranges from 0 to 500; the higher the number, the worse the air quality. While an AQI value under 50 means that the air quality is good, readings under 100 are generally considered to be satisfactory (EPA AirNow). When readings are higher than 100, we worry about the health of sensitive groups, such as people with respiratory problems, the elderly, and small children. Readings between 201 and 500 signal to the public that the air quality is very unhealthy and can have negative effects on everyone’s health.

An AQI value is generated for five major pollutants: ground-level ozone, particulate matter (PM) like PM2.5 and PM10, carbon monoxide, sulfur dioxide, and nitrogen dioxide (NOAA). While all of these pollutants affect air quality, PM and ozone pose the greatest risk to human health in the United States (NOAA). The value that is the highest concentration of the five major pollutants becomes the AQI value for the area.

Individual states and local agencies calculate AQIs. The national standard for acceptable values of each pollutant in the air differs, which is taken into consideration for each calculation. These values are also produced at different times, based on the unique pollutant. For example, the AQI value for ozone is based on an 8-hour time frame, while particle-pollution values are made every 24 hours (EPA AirNow).

The AQI can be calculated both as a forecast and as a nowcast. Like we see in air temperature forecasts, AQI can be reported as a prediction of the AQI values for the next day (forecast) or as the current state of the air (nowcast). AQI forecasts are typically made for PM and ozone levels because of their greater risk to human health (NOAA). An AQI forecast is made from hourly measurements of each pollutant, while a nowcast is an estimated value of the current, hourly measurements of PM and ozone levels in the air AND two different EPA algorithms. Satellites and ground-based measurements are used to monitor the levels of pollution in order to produce accurate nowcasts (NOAA).

When you check the air quality in your area, whether through the EPA’s website, ground measurement sites like PurpleAir or the CEAMS network, you’re most likely reading a nowcast of the AQI.  Whether you use the AQI as a forecast or as a nowcast, you should take its values into consideration when you are planning on doing outdoor activities because poor air quality is hazardous for your health. If you would like to learn more about air quality, here are a few links you can check out:

·       Health effects from poor air quality

·       Steps you can take to protect yourself from poor outdoor air quality

·       AQI calculator

·       Network of EPA air quality monitors and downloadable data

We’re proud to be a large group of scientists from many different fields. Our researchers come from four groups on Colorado State University’s campus, and we'd like to showcase our lab groups and what they're all about.

The Volckens Group

Based in Mechanical Engineering, the Volckens’ Group mission is to use engineering fundamentals to solve air pollution problems that we face as a society. Their work is best described as Engineering for Public Health; they aim to develop innovative leaders with the interdisciplinary skills needed to solve today’s complex public and environmental health problems.

Recent projects include:

• Development of low-cost instruments for air pollution monitoring and human exposure assessment
• Quantifying the short-term health effects from exposure to woodsmoke and other forms of combustion air pollution
• Delivering solar power and clean cooking technologies to rural Rwandan households
• Measuring air quality (in collaboration with NASA scientists) aboard the International Space Station

Aerosol and Cloud Research Group

The research group of Dr. Jeff Pierce in the Atmospheric Science department at Colorado State University. Their research focuses on atmospheric particles and gases and their interactions with human health, clouds and climate. Specifically:

1. Aerosols and climate
2. Aerosols and health
3. Wildfire smoke
4. New-particle formation and growth

Center for Science Communication

Housed in the Department of Journalism and Media Communication  the Center for Science Communication is a hub for interdisciplinary, stakeholder-engaged scholarship in science communication. The center brings together faculty experts, professionals, and students who pursue research-driven strategies for effectively communicating about science and science-related topics. The center’s goal is to foster better communication in support of socially sustainable agricultural, environmental, and health systems. Current and recent work by center-affiliated faculty has been funded by the National Park Service, U.S. Department of Agriculture, NASA, U.S. Forest Service, U.S. Geological Survey, and the National Institute of Standards and Technology.

Laboratory for Air Quality Research (LAQR)

Led by Dr. Shantanu Jathar, through the Mechanical Engineering Department, this group conducts laboratory, field, and numerical studies to probe the emissions and formation of air pollutants arising from energy and combustion sources. Some recent projects include

1. Studying the formation and evolution of fine particles in wildfire plumes
2. Improving the representation of fine particles in mesoscale climate models
3. Quantifying the potential for air pollution from emerging sources including biofuels and consumer products

If you have any questions about the work these groups are doing, please ask!

By Jeff Pierce

Our devices measure two qualities of particles in the atmosphere. The first is called “PM2.5”, which is the mass of small particles in the air that we breathe at the Earth’s surface (more technically, it’s the total mass of particles that have diameters smaller than 2.5 micrometers per volume of air). To get a sense for how small these PM2.5 particles are, see the Figure 2 below.

Many studies have shown that breathing in a lot of PM2.5 is bad for your health. Bad air quality can affect asthma and even lead to heart attacks. The EPA watches over PM2.5 levels to help protect our health (PM2.5 has dropped dramatically in the US over the past 50 years, and we’re still getting cleaner!). However, the EPA’s PM2.5 monitors are limited to only a few per county. Some counties even have just one monitor. Many regions of the world completely lack PM2.5 measurements with air quality that is getting worse!

As PM2.5 is bad for human health, but is lacking in global measurements, scientists have been using measurements from satellites to help estimate PM2.5 around the Earth. Scientists can use how hazy a location on Earth looks from space to estimate aerosol optical depth (AOD). AOD is a measure of how much sunlight is scattered or absorbed by particles. In Figure 3, our eyes can easily see where there’s thick smoke, clouds, and clear sky. Like what our eyes can do, scientists can calculate locations of high AOD and low AOD.

However, satellite AOD values are not always a great measure of the PM2.5 that we breathe at the surface. What if the smoke in the image above was way up in the atmosphere, and not at the surface? The AOD would still look high to the satellite, but the air we were breathing would be clean.

We need measurements of both AOD and PM2.5 from the same location to help us understand the relationship between what the satellites “see” and what we breathe. The measurements that we are making will help scientists estimate the air quality in places where we do not have PM2.5 measurements!

The CEAMS team is made up of a large group of scientists, across many different fields. With project scientists, professors, and post-doctoral scholars, being a part of CEAMS means working with interesting people from fascinating backgrounds.

We'd like to showcase our graduate students and what they're all about:

Michael Cheeseman

I am a PhD student working on the CEAMS project. My primary job is to analyze the data that our participants collect and display them in fun and informative ways for the public. Then I take that data and attempt to answer the primary science questions of the project. For example, I want to use satellite data in conjunction with CEAMS data to assess how wildfire smoke impacted days may affect our ability to predict ground-level air pollution over Denver.

I went to school in the Appalachian mountains of North Carolina, where forest fires would blow smoke as thick as fog over our town. We’d be stuck inside in order to protect our lungs. I didn’t know back then, looking out into the suddenly gray world that had descended, that I would eventually study wildfires as a career. It was experiences like this, as well as learning about the climate crisis and global scale pollution, that motivated me to study environmental science. I hope to use what I learn working with the CEAMS team, and the Denver community, to pursue a career in policy and science communication.

Zoey Rosen

My focus is on the social science side of the CEAMS project. I am in the PhD program for public communication and technology, so I focus on how science is communicated.The CEAMS project and the data we collect will help me learn more about the social processes behind citizen science, and what brings people to participate in an effort like this. I hope to use what we learn from this project in my doctoral work and grow as a scientist.

I grew up in Los Angeles, California, so poor air-quality days were part of our yearly fire season. When I lived in Reno, Nevada, especially during the 2013 fires, I learned about how altitude, inversion layers, and mountains affect air quality. Now living in northern Colorado, my interest in the air quality is only growing with each day. From the places I've lived, I've gotten to learn about how unique the environment is in each area, and how influential air quality is on the people who live there.

Eric Wendt

I am a mechanical engineering PhD student and my primary role on the CEAMS project is leading the design and testing of our air pollution monitoring instrument, the Aerosol Mass and Optical Depth (AMOD) monitor. Our engineering team designed the AMOD specifically for deployment in large citizen-science networks, with low-cost and ease-of-use our primary design criteria.

I started in our group as an undergraduate intern. My interests in cyber-physical systems and atmospheric measurement motivated me to continue on as a graduate student. For the remainder of my program, I plan to continue my study of cyber-physical systems and work to make low-cost, high-quality air pollution measurement more accessible across the globe.

By Bonne Ford

So, the AMOD sampler is set up in your backyard, and you’ve logged on to the website and started seeing your data. What does the data tell you?

Remember, the instrument is taking different air-quality measurements. It measures small particles (“particulate matter” [PM]) down here at the surface where you breathe and it measures the particles in the column of the atmosphere above you (this value is often called “aerosol optical depth” [AOD]). When these particle values go up, it means that air quality has gone down. These two values will change throughout the day, and the values in your backyard might differ  from those in a backyard just a few blocks away. There are a lot of different sources of particles in the air, both natural (like dust or sea salt) and from human activities (like from vehicle or power plant emissions).

There are many reasons why air quality varies in time and place. For example, we often see higher values during rush hour, because more cars are on the road (emission sources). So, your backyard air quality might be slightly worse than your neighbors’ if you live closer to a busy street. You could also see a spike in particle mass if someone drives an old pickup by your house, you use a gas-powered lawn mower,  or if you like to grill in your backyard.    The weather can also affect air quality. Rain can wash out particles. Wind can stir up particles. Cold, calm nights can allow particles to just hang around and build up.  

Sometimes the two measurements (AOD and PM2.5) will show similar changes, and sometimes one value will change more than the other. This difference is mostly because particle concentrations can change with height. While there are a lot of emission sources at the surface, particles can also come from higher up (for example, volcanoes, big forest fires, or smoke stacks). Particles can also be lifted up into the air by the wind. If particles are higher up in the air, you might see your AOD reading go up while your PM2.5 reading stayed the same. If particles are all near the surface, you might see more change in PM2.5 and not much change in AOD.

We finished our first round in Denver last month, and all the AMODs are back in our possession. We learned a lot during the deployment and are using that knowledge to hopefully improve our AMODs and our CEAMS network.

We had 32 citizen scientists from across the Denver-Metro area. Coming from the Community Collaborative Rain, Hail and Snow Network (CoCoRAHS) and the CBS4 community, our citizen scientists have lived in the area for an average of 33 years. CEAMS participants set up our AMODs in their backyards and collected filter measurements, along with taking 2 surveys each. We are grateful for the incredible data that will give us new, local insight into Denver air quality, and that would not have been possible to collect without all of our CEAMS network participants.

The CEAMS citizen scientists captured nearly 60,000 real-time PM2.5 measurements, over 160 filter PM2.5 measurements, and 1,300 AOD measurements between November 2019 and January 2020. From the collected data, we saw several stagnation events (when air masses sit over Denver and pollutants build up over time), which are a common air quality issue for Denver in the wintertime. An example of one of these events is shown through the time series of the PM2.5 concentrations for December 21st -December 29th, 2019 in the graph below. The red line is the average concentration (average over 3 hours and across all locations) and the faint gray lines are all the individual locations (3 hour average).

In the first part of the time series graph, we see a normal (wintertime) daily cycle in PM2.5. PM2.5 concentrations begin to rise each day in the afternoon, during rush hour, and continue to rise overnight when the boundary layer height is low and the winds are generally calmer. The lowest daily average during this period was on Christmas day (probably because of less traffic as people stayed home and businesses and restaurants were closed).  However, a large spike in PM2.5 then occured on Dec. 26th and Dec. 27th with the stagnation event.

We are also able to see variability in the PM2.5 concentrations in the different areas of Denver. Over the entire time period (November 2019 - January 2020) the average PM2.5 concentration was generally higher in northern Denver (Figure below on left), while the average measured AOD values were similar across Denver (Figure below on right). AOD is a measure of all the aerosols in the atmospheric column (provides a more regional view of air quality), and PM2.5 is a measure of the small particles at the surface (provides a more local view of air quality). Thus, PM2.5 concentrations are going to be more impacted by local emission sources.

We still have much more analysis to do (we have the graduate students hard at work!), but we are already excited about the potential of this data set. We will be adding more data as we are going to be putting out AMODs in Denver again for this spring.

While we have had the AMODs back at our lab, we have been able to recalibrate instruments and make some improvements. Our Denver deployment and feedback from our participants gave us useful insights that led us to improve the mechanical design for the AOD turret, better battery connections, and some major software updates to increase Wi-Fi reliability and sun tracking.

Our first Denver deployment was invaluable in helping us improve the design of the AMOD (thanks, participants, for all your observations and feedback!). We have worked on the mechanical design to improve the motion of the AOD turret and sealed our battery connections to ensure full five-day runtimes. We have also revised the software to improve Wi-Fi reliability and sun tracking. And for those AMODs that got buried in snow and ice back in November and sustained some water damage, we made some repairs and changed our sealing. After all those changes and repairs, we have put all the AMODs through several multi-day functionality tests (picture below).

We are looking forward to wrapping up our final testing and putting our AMODs back out in Denver!

First off, what is CEAMS?

CEAMS stands for “Citizen-Enabled Aerosol Measurements for Satellites.” That sounds cool, but it doesn’t tell you what CEAMS is. CEAMS is a network of citizen scientists taking air-quality measurements in their backyards.

"A partnership implies that we are working together, and we hope that you will see CEAMS that way."

What (or who!) are “citizen scientists”? There isn’t one universal definition of citizen science. For us, citizen science is a collaborative effort wherein volunteers help researchers collect scientific data. And this data isn’t just collected for fun; it is collected to help answer research questions, provide meaningful information to communities, and, hopefully, increase participants’ understanding of air quality science. In CEAMS, this collaboration, or partnership, is between volunteers and scientists at Colorado State University. Scientists at CSU designed the sampler that participants will use to collect data (pictured below). Participants set this sampler up in their backyards and use it to take measurements. Those measurements are sent back to the CSU scientists who will analyze it. And by “analyze,” we mean that they will study how the air-quality measurements change over time, compare measurements at different locations, and try to better understand regional air quality in general.

Okay, so we keep mentioning “air quality”, what are we talking about? “Air quality” refers to the condition of the air, and poor air quality means that the air contains pollutants like gases and small particles. These small particles can come from a variety of sources (vehicle exhaust, wood burning, road dust, etc.).Breathing in these particles can impact your health. The device used in the CEAMS network measures these particles in the air in three different ways. We will discuss those different measurements more in a future blog post, but our measurements will show how air quality changes throughout the day and season, how air quality varies across neighborhoods in a city, and what different sources impact local air quality. There is a lot of exciting information we hope to gain from CEAMS measurements.

You are probably still wondering “How are these measurements for satellites?” Right, that is an important part of this project! CEAMS is funded by NASA. NASA has satellites that take pictures of the Earth. Some of these satellites monitor global air quality from space. These satellites give us a big-picture idea of air quality, but they cannot always tell us what air quality is like at the ground in different communities.  By having citizen scientists take the same air-quality measurements in their backyards that the satellites do, we hope that our CEAMS measurements will help connect these big-picture views of air quality and local, on-the-ground air quality.

There are lots more details and information we can give you, and we will. Keep reading our weekly blog to learn more about CEAMS!

Want to know more about how to participate? Check out this video:

by Jessica Tryner

Is Colorado meeting the National Ambient Air Quality Standards? Is the air outside healthy to breathe today? To help answer these questions, the Colorado Department of Public Health and Environment (CDPHE) monitors the mass of fine particulate matter suspended in each cubic meter of air (the “PM2.5 concentration”) at five sites in Denver. These sites are in the Globeville, Sunnyside, Five Points, Hale, and Lincoln Park neighborhoods. The sites in Globeville and Lincoln Park are close to I-25 (see Figure 1).

A single monitor (either a GRIMM EDM Model 180 or Teledyne T640) is installed at each site. Each monitor costs tens of thousands of dollars! These monitors determine the PM2.5 concentration in real-time by sampling the air, passing the particles in the air through a sheet of laser light, and measuring the amount of light scattered by each particle (see Figure 2). The monitors used by CDPHE have gone through a lot of testing and are approved by the U.S. Environmental Protection Agency for outdoor monitoring**. You can look up the hourly PM2.5 concentrations reported by the CDPHE monitors here.

The AMOD is more affordable than the monitors used by CDPHE. One AMOD costs approximately $1000. The AMOD measures the same quantity as the monitors installed by CDPHE (the PM2.5 concentration), but it uses a different approach. First, the AMOD samples air through an inlet that only allows particles smaller than 2.5 μm to enter. Next, the air passes through a filter, where particles in the air are captured (see Figure 3). We weigh the filter before and after sampling to determine the mass of the captured particles (see Figure 4). The AMOD records the volume of air that it pulled through the filter. Finally, we use the known mass of particles and volume of air to calculate the average concentration of PM2.5 in the air sampled by the AMOD over a five-day period.

The AMOD also measures another quantity that the monitors installed by CDPHE do not measure: aerosol optical depth (AOD). What is aerosol optical depth and why do we want to measure it? You can read more about that here!

Because the AMOD is cheaper than the monitors installed by CDPHE, volunteers (like you!) can set up more AMODs across Denver. By putting more monitors in more locations, we can find out how outdoor PM2.5 concentrations vary over shorter distances. What do PM2.5 concentrations look like in your neighborhood? Are they lower than, higher than, or similar to concentrations in other Denver neighborhoods?

How does the AMOD Compare to Low-cost PM2.5 Monitors?

Even though the AMOD is pretty affordable, there are air quality monitors on the market that cost even less. For example, you might have heard of the PurpleAir monitor; there are currently a handful installed around Denver.

The PurpleAir monitor is popular for a few reasons: it’s small, costs less than $300, requires very little upkeep from the user, and reports PM2.5 concentrations in real-time. Data from PurpleAir monitors are streamed to a website where you can see how PM concentrations vary with time in thousands of locations all over the world.The PM sensors inside of most low-cost monitors, like the PurpleAir, estimate the mass of particles in the air by measuring the amount of light scattered by a group of particles (see Figure 5). Unfortunately, the amount of light scattered by a group of particles depends on more than just the mass of the particles! The amount of light scattered also depends on things like the sizes of the particles. As a result, a low-cost monitor might report a real PM2.5 concentration of 10 μg·m-3 (for example) as 7 μg·m-3, 10 μg·m-3, 15 μg·m-3, or some other value depending on the weather and the sources of the particles***.

In the AMOD, we sample particles onto a filter so that we can measure the mass of particles directly. This approach produces a more accurate measurement of the PM2.5 concentration outside your home. Unfortunately, collecting and analyzing filter samples requires a little more effort from us and from you. We need to pre-weigh each filter and send it to you. You need to regularly replace the filter inside the AMOD and return each used filter to us. After you return your filter, we need to post-weigh it and calculate the PM2.5 concentration in the air that was sampled (learn more here). We think the more accurate measurement is worth this extra effort!

Sources:

*:https://www.epa.gov/outdoor-air-quality-data/interactive-map-air-quality-monitors

**:https://www3.epa.gov/ttn/amtic/files/ambient/criteria/AMTIC_List_June_2017_update_6-19-2017.pdf

***:https://doi.org/10.1016/j.envpol.2018.11.065

****:https://doi.org/10.1016/j.envpol.2016.12.039