They are ubiquitous, nearly invisible and may determine the future of our planet. Known as aerosols, the small specks of matter can be found in nearly every ecosystem, in the air over oceans, above deserts and mountains, deep in forests and compressed under ice.
When you see your breath on an autumn morning, those are aerosols carried along in water vapor from your lungs. Aerosols are created when small solid particles or liquid droplets are suspended in air. The tiny particles play a big role in influencing air quality and could determine the future of Earth’s climate.
While some aerosols occur naturally, others are man-made. The smoke above a wildfire, the haze over a city, the wind-blown dust over croplands are all anthropogenic sources of aerosols and generally understood to contribute to climate change.
Lesser understood is how those aerosols form in the atmosphere. Sometimes molecules will stick to one another and grow into entirely new particles or they’ll condense on pre-existing particles and form secondary organic aerosols, an area of expertise for Nathan Kidwell, assistant professor of chemistry at William & Mary.
“The greatest uncertainty in atmospheric chemistry right now is how well we know if aerosols will warm or cool the atmosphere,” Kidwell said. “It's all dependent on what kind of molecules make up the aerosol and the size of the aerosol. What we really want to understand is how molecules form aerosols and also change how aerosols absorb or reflect light. That will tell us about energy balance, which has implications for climate change and public health at large.”
Kidwell’s lab inside the Integrated Science Center has been designed to mimic the way molecules interact with the sun. It is equipped with a series of high-powered lasers that emit wavelengths matching the sun’s frequencies. The lasers zap aerosol-relevant molecules pulsed into a vacuum chamber, breaking them apart. The fragments are directed down to a detector, which captures an image of what the products look like when these molecules interact with sunlight.
“In our lab, we actually simulate these processes,” Kidwell said. “We can gain a molecular-level perspective of aerosol formation in a controlled environment. This new project aims to understand how they behave in the wild, which is a complementary and interesting way of studying atmospheric chemistry.”
Meet the AIRduino, a hand-held multisensor device based on Arduino microcontroller technology that makes atmospheric measurements in the actual atmosphere and streams them back to a smartphone app in real time. The device was designed and built by William & Mary undergraduate students and their high school protégés this summer in the Kidwell lab. The project was entirely funded by the W&M Committee on Sustainability Green Fee Program.
“This device is a great way to engage students and inspire people in general,” said Kelly Rodriguez-Vasquez ’20, who served as team leader for the project. “It makes it possible for them to collect data and help the environment by monitoring the changes going on.”
Essentially, the AIRduino is a portable measurement lab. It’s an array of sensors that measure the air for concentrations of ozone, volatile organic compounds, temperature, humidity and aerosols of different sizes. Air is drawn through a 3D-printed box onto the sensors by a built-in fan. As the air passes over the sensors, the AIRduino records all measurements simultaneously. The device is small and lightweight enough that it can be mounted on a drone, which is the next phase for the project.
“We plan to partner with local schools and the Virginia Institute of Marine Science to monitor how regional atmospheric chemistry impacts aerosol formation with changes in geography and season,” Kidwell said.
There are 22 different interchangeable options for sensors, which can check for a myriad of compounds, like the carbon-based aerosols made from burning coal, oil, diesel fuel, wood and natural gas. The AIRduino is paired with a smartphone via Bluetooth and the data is streamed back to an app interface so it can be viewed in real time. The results are also recorded with on-board storage using an SD card.
Students developed every aspect of the device, Rodriguez-Vasquez said. She’s a chemistry major and she taught herself to code in order to build the app. The other students, Aaron Cole ’19, high schoolers Lehman Montgomery, Rachel Smith and Desislava Yordanova, also taught themselves elements of coding, chemistry and engineering.
“We really worked as a team,” Rodriguez-Vasquez said. “And we all wore a lot of hats.”
She added that the democratic nature of the AIRduino’s development process made its way into the final product. They used open-source technology to encourage citizen scientists to use (and even improve) their design.
Arduino microcontrollers and 3D printers are readily available in makerspaces, libraries and classrooms throughout the country. The code for the app is available for free online. The team also wrote a paper that will soon be published in The Journal of Chemical Education that serves as an instruction booklet for a build-your-own AIRduino, app and all.
“I know since we’re really in a time of discussing climate change, people feel like they want to make a difference, but they have no idea how,” Rodriguez-Vasquez said. “If we make this accessible and people see they can do it on their own, they'll feel more inclined to do it. I’m sure there are scientists out there who can improve upon it, or other educators who may want to make adjustments to it. It’s all about sharing what we’ve made, so we can build a greater scientific community.”
The “makers” ethos that fueled the AIRduino project began in the classroom, specifically in the course Introduction to Engineering Design taught by the university’s makerspace director Jonathan Frey. Last year was the first year the course was offered and members of Team AIRduino were in both semesters of the class.
“The interdisciplinary nature of this project and others like it is what the Makerspace Program is all about,” Frey said. “You get innovation as an outcome when you have people from all different backgrounds coming together. I look at makerspaces as the modern manifest of liberal arts.”
“If you go back to the days of Plato,” he added. “The liberal arts were the skills that you needed to be a productive citizen in modern society. It used to be that if you couldn’t read, you had more difficulty getting certain jobs. Nowadays, if you don’t understand 3D modeling, you’re going to have trouble getting a lot of jobs. Those skills change over time, even if the values stay the same.”
Students from the AIRduino team saw professional engineering skills in action when they visited the NASA Langley Research Center to calibrate their atmospheric sensors. The students worked with NASA scientist Margaret Pippin and the Virginia Department of Environmental Quality (DEQ) to share atmospheric results, comparing them to those collected at NASA’s Chemistry and Physics Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton.
“That was really the cherry on top,” Kidwell said. “Here are all these different students, from local high schools, from William & Mary, and they’re all working together and taking measurements with NASA’s atmospheric scientists. They were showing the students how to calibrate their sensors using these top-of-the line instruments. It was really cool.”
Conventional means to measure aerosols in the wild include land-based probes like CAPABLE, which requires a wide array of instrumentation for consistent, long- term surveillance of regional air quality, Kidwell explained. There are also air quality probes that can be launched via aircraft to measure air pollution during an event like a wildfire.
While these methods are, and will continue to be, extremely useful for the scientific community and society at large, the high cost of the instruments keeps them from being deployed over a larger area, Kidwell added. That means there are swathes of the country without good data. A low-cost and readily accessible device like AIRduino could make all the difference for getting air quality data in underserved regions — including the Tidewater.
“There’s a really interesting question about how chemical composition influences aerosol production here in the Tidewater region of Virginia,” Kidwell said. “Because of this accessible technology, we are empowering students to act as citizen scientists and be informed about these processes that are occurring right in their backyard.”