Volcanic mountains

Low-cost sensors measure exposure to volcanic smog in real time

When the Kīlauea volcano erupted in 2018, lava covered parts of the island of Hawaii, but volcanic smog, known as “vog”, flooded it. The vog contained dangerous levels of fine particulates and sulfur dioxide, which threatened the health of the population downwind of the island.

In a new study, a team of scientists used a network of low-cost air quality sensors to map residents’ pollution exposure in real time, for the first time. New air quality measurement solution could help prevent people from getting sick in the future, as air pollution is the world’s biggest environmental risk factor for premature mortality

“We were able to estimate fine-scale population exposures to multiple pollutants, measure the chemical transformation of volcanic emissions, and provide real-time observations as part of emergency management efforts,” said Benjamin CrawfordPhD, lead author and assistant professor in the Department of Geography and Environmental Sciences at the University of Colorado at Denver. Crawford collaborated with researchers from the Massachusetts Institute of Technology and the University of Hawai’i.

the study was published in the journal PNAS.

Real-time monitoring during a catastrophic event

Benjamin Crawford, Ph.D.

Prior to 2018, Kīlauea Volcano had been continuously erupting on a much smaller scale for 35 years. In late 2017, the Crawford team launched a project to measure air quality downwind of the smoldering volcano, partnering with local schools to host sensors.

“We thought there was no rush,” said Crawford, who was then working as a postdoc at the Massachusetts Institute of Technology. The team had a handful of low-cost sensor (LCS) prototypes and had begun laying the groundwork for the island when the volcano began to erupt in earnest in May 2018. The group swung into action. “We took off and built the network in 10 days,” Crawford said.

The team used 30 nodes designed and deployed specifically to monitor a mix of primary volcanic sulfur dioxide (SO2) and secondary particles (PM2.5) that make up vog. Their study became the first to use a low-cost, real-time sensor network during an extreme air quality event.

Monitoring of the chemical transformation of the plume

Downwind of the eruption, the team found that stations in the array measured peak hourly concentrations of PM2.5 and SO2 that could exceed 75 micrograms per m-3 and 1200 ppb, respectively. The density of the LCS network allowed very accurate estimates of human exposure to the two pollutants during the eruption, which was impossible with pre-existing air quality measurements.

The plume dynamics exposed a much larger proportion (46.7%) of the island’s population to elevated levels of fine PM2.5 compared to SO2 (2%). In addition, the network was able to follow the chemical evolution of the volcanic plume downwind of the eruption. The measurements found an average SO2 conversion time of around 36 hours, demonstrating for the first time the ability of distributed LCS arrays to observe reaction kinetics and quantify chemical transformations of air pollutants in a real environment.

“We had a good idea of ​​where the pollution was going, so we were able to track and measure the chemical transformation of the plume,” Crawford said. “It was the first time that we could observe both the chemistry of the plume and its movement downwind. It was gratifying to see our approach work.

Pollutants covering the sky
First, the researchers measured and monitored the chemical transformation of pollutants during the eruption.

Allow other people to measure air quality

Air quality (AQ) monitoring is essential to understanding and ultimately minimizing people’s exposure to harmful air pollutants; however, surface measurements remain relatively rare in much of the world. Indeed, most air quality measurements come from networks run by governments, such as the states or the Environmental Protection Agency (EPA) in the United States. These extremely precise instruments are expensive, which limits the number of sensors deployed. On the Big Island of Hawaii, there were six permanent monitoring stations in operation before the eruption, including one destroyed by lava early in the eruption.

In contrast, the low-cost sensors in this study are self-contained, solar-powered units that can communicate via cellular networks and operate in remote locations. The affordability of the units also allows the team to hand them out to community members to measure the air quality themselves. Whether it’s during a volcanic eruption, wildfires, or everyday urban pollution and smog, it’s important to empower communities to measure data themselves.

“There’s a demand for this kind of information,” Crawford said. “It’s a great way to democratize data and allow communities to monitor air quality violations independently of anyone else. You can give people the knowledge to make their own decisions. »