In Auvergne-Rhône-Alpes, citizens equipped with micro-sensors have recently been participating in citizen observatories to measure air quality. Their data now makes it possible to refine conclusions on the impact of lockdown.
Experts' findings refined through citizen participation
Does lockdown improve air quality in our region? Globally yes, and this from the very first days. It has a particularly positive impact on pollutants emitted mainly by road traffic, such as nitrogen oxides, which on some days are reduced by up to 80%. A spectacular decrease, even never seen before, testify the engineers and forecasters of Atmo Auvergne-Rhône-Alpes. For fine particles, whose sources are multiple, the impact seems more mitigated. Observations to be found entirely in their evaluation of the impact of the first days of confinement on air quality in Auvergne-Rhône-Alpes.
But what about more locally, and more particularly on fine particles?
Precisely, citizens throughout the region are seeing these results for the first time on their own, thanks to the deployment by Atmo Auvergne-Rhône-Alpes of several citizen observatories to measure air quality. They consist of the installation, by citizens and civil society actors, of micro measurement stations in their homes and buildings as well as the monitoring of data produced on a daily basis.
Example of the high school observatory of the Arve Valley
One of these first projects of citizen measures is the Arve Valley High School Observatory. Bringing together Atmo Auvergne-Rhône-Alpes, the Bontaz group and the high schools of Passy and Cluses, this project has enabled nearly 40 students to build an experimental network of 30 micro-stations for measuring fine particles throughout their school year.
Antonin, one of the students, explains the project to us:
Micro-measuring stations that are now deployed throughout the Arve valley, and whose data, which can be consulted on the captotheque.fr platform, allow us to refine our understanding of the local impact of containment, particularly in terms of particulate pollution.
The map of the micro-stations of the high school air quality observatory
In the Arve valley, an increase in particulate matter observed by high school students
By analyzing the data from this high school observatory, the high school students and citizens present on the platform actually noticed an increase in fine particles for all the micro-stations, as early as March 18th, the day after the lockdown. This increase is continuous for nearly 2 weeks, until the end of March.
Data measured on one of the micro-stations of the Arve High School Observatory, from the Captotheque. The particles increase from the beginning of the lockdown until the end of March, with a peak around March 26th, almost 10 days after the confinement.
On some sites, concentrations of up to 40 µg/m3 are measured as a daily average, especially on March 26th, when activity and personal travel are considerably restricted by the confinement.
Another micro-station of the Arve Valley High School Observatory, which recorded concentrations up to nearly 40µg/m3 on March 29th, in full confinement
A phenomenon also observed in Grenoble and the Lyon metropolitan area.
In the Grenoble conurbation, in Seyssins and Herbeys, other micro-sensors are deployed in private homes. On this territory, the same phenomena are observed, as shown in the graph below, leaving the citizen at the origin of the measure perplexed :
Here is my measurement over more than a month with confinement since March 17, we see a peak around March 29/30 that I can't explain - JLC, an experimenter who installed a micro-station in his house of Herbeys
An experimenter who hosts one of the micro-stations of the captotheque wonders about the increase of particles during confinement.
In Bron, in the metropolis of Lyon, a microstation has also been installed in a private home since March 20th. Here too, he notes an increase in particles measured until the end of March, with a peak of 32 µg/m3 of particles measured on March 29th. Thus, even in peri-urban environments, where containment has the greatest impact, particles may continue to increase.
I was surprised to see that the particles measured by my sensor did not go down, it's even the opposite! Yet since the confinement the environment has never been so quiet around my home, especially in terms of road traffic - AFREI, experimenter at the Captothèque in Bron
In urban areas, where a priori containment has the greatest impact on air quality, particulate matter also continues to increase.
Is individual wood heating involved?
This increase in airborne particulate concentrations, despite a sharp decrease in activity, may indicate an increased impact of the residential sector, such as home heating, on particulate pollution.
Wood heating, which is known to be the primary source of fine particulate pollution in winter in the region, appears to be a major contributor. The drop in temperatures, observed in the second half of March, supports this analysis by an increased use of heating.
I'm in a suburban area, at the entrance of Lyon, in a residential area with a lot of individual houses. With the confinement and at the sight of the data from my micro-sensor, I observed a little bit my surrounding environment... and it is true that we notice a lot of plume coming from chimneys. I didn't think that there were so many houses equipped with chimneys so close to the city!
Exogenous sources, and technical reserves to be taken into account
The engineers of Atmo Auvergne-Rhône-Alpes also mention the secondary particles resulting from agricultural activity as well as the presence of "large scale" air masses transporting desert dust, the discrimination of these sources being possible only thanks to the advanced analyses carried out within the framework of the classical Observatory of Atmo Auvergne-Rhône-Alpes.
Advances in micro-sensor technologies will soon make it possible to integrate other pollutants, such as nitrogen oxides, and to further expand the capacity of these citizen observatories to improve our understanding of the phenomena influencing the air quality of a territory. Also, the offer of micro-sensors proposed within the Captotheque device is constantly evolving, and tends to become more reliable and diversified in the near future.