Military exercise in Brecht: Follow the smoke plume

Introduction

In April 2021, the army held a shooting exercise on the Groot Schietveld military domain in Brecht. Things did not go as planned, resulting in a huge forest fire. No less than 570 hectares of nature reserve went up in flames. A northeasterly wind blew the smoke plume all the way to Lille in France. We spoke with David Roet and Christophe Stroobants of the Flemish Environment Agency ( VMM ) about how citizen measurements are a nice addition to official models.

On a weekday working from home in April 2021, David Roet looks out of the window in Mortsel. Like thousands of other residents in and around the city of Antwerp, he sees a kind of mist and smells the typical smell of wood burning outside. The news sites soon report on an army exercise that caused a gigantic forest fire.

At the same time, David realises, this is also a unique opportunity to follow the smoke plume live as an experiment. 'Colleagues from the IRCEL (Interregional Cell for the Environment) are making model maps based on our measurements. You can see that the dots on the map – our measuring stations for fine dust – turn completely red around Antwerp at around 3 p.m. This extreme situation leads to very high fine dust concentrations of several hundred micrograms per cubic metre.'

'We thought it would be a good idea to compare the map with fine dust sensors from citizens with our data. We saw that the plume was already at Oudenaarde around 15:20. You can also find that on Sensor.community where the measurement results of fine dust meters appear. And so you see that the fine dust meters cover almost all of Flanders.'

Cheap sensor, expensive measuring station

Do these sensors perform as well as the expensive measuring stations? 'No,' says David. 'But with the fire on the military domain, for example, it wasn't so important that the measured concentrations were exact. Whether it was 200 or 300 micrograms per cubic meter: the concentration of fine dust was extremely high. You can easily display that on a map. That's why I deliberately chose a scale that stops at 70 micrograms. In reality, those values were hundreds of micrograms high, but here I colored everything above 70 micrograms dark red.'

This brings us to a major difficulty when using citizen measurements, says David: 'in normal circumstances, a dark red sensor means that you are picking up a local phenomenon such as a barbecue, or it indicates a malfunctioning sensor. You have to manually select which sensors are working correctly and which are not. You cannot automate that so easily.'

Rewarding citizens who measure

Christophe also likes to look at the interaction with citizens. 'It is not always easy to find cases where the measurements of citizens provide exactly the missing information. In this case – the fire started on Friday afternoon, just before the weekend – we were also too late to immediately publicly highlight the added value.'

'It did teach us that we want to give something back to people who perform measurements. We want to show that we recognize their efforts,' says Christophe. 'We tend to communicate mainly about those very exceptional cases. But even when the measurement results of citizens and our sensors point in the same direction, it is useful to explain this. This gives people insight into why their measured value has increased, for example. That also makes it clearer why we organize certain actions.'

Model cards and data portal

The VMM therefore has a number of projects in the pipeline, says Christophe. 'David did that exercise after the fire in Brecht, and in the future we want to integrate this permanently into our model maps. That is an important point in our strategy.'

'A second project in which citizen measurements play an important role is our own data portal, ' Christophe explains. 'That quickly provides an overview of the citizen measurements in combination with our reference measurements. Our own models also cover the entire territory, but for certain regions the results are based on assumptions. For example, we know that there is industrial activity in a certain neighbourhood, and we adjust our estimates accordingly. Citizen measurements then provide additional local input and supplement our data. In order to utilise the added value of these sensors even more, the VMM and VITO (Flemish Institute for Technological Research) are also part of a European forum working group on air quality modelling.'

Sharing projects such as the integrated model maps and the data portal with the public also ensures that citizens do not drop out. This way they see that something actually happens with their measurements. Moreover, some citizens and governments attach more value to measurements than to models.

Measurements as a canary in the coal mine

Sensor measurements may not always be reliable, but they do fill in the blind spots. In this way, this information can help to monitor fires or other disasters. The fire in Brecht demonstrated the potential in extreme situations for the first time.'

An additional advantage of this type of measurement is that you make citizens aware of their impact when they light a charcoal barbecue, stove or fire basket. 'We do give stoking advice based on our own measurements, not on the citizen measurements. That is then included in the weather forecast, for example, but the debate about wood burning is much fiercer and more active in the Netherlands than here.'

'You can also work on school routes and measure children's exposure to fine dust,' Christophe adds. 'But in addition to these hard targets, we want to recognize the citizens who faithfully perform measurements for their efforts and show our appreciation with our integrated model maps and the data portal. We also hope for more cases in the future where citizen measurements make a difference, although these do not necessarily have to be gigantic fires (laughs).'

Watch and learn: tips and experiences from the VMM

1. Let us use the sensor measurements above all: Sensor measurements always provide valuable information: sometimes crucial input, sometimes supplementary. Now it is important to make this information readily available.
2. To the measuring citizen: keep measuring : We really use the data you collect. And in return we try to make sure that you learn something from it too.
3. We don't say it enough: thank you, merci!