Our ranking of Romanian municipalities in terms of air quality has sparked a lot of debate in this country. Here is a text explaining in more detail how this list was created and what criteria we adopted.
Why do we need Airly sensors?
Airly has a much higher range of measured concentrations than official stations. It is a result of the fact that Airly sensors are located everywhere clients want them to be located, while official stations must fulfill location requirements. This means they might be located far from emitters – like congested roads and industrial plants.
This means official stations are often located in remote places – like sparse gardens in cities. Conversely, Airly sensors are located in places where people live, spend their time and breathe polluted air.
The figure below shows the minimum and maximum daily pollution, recorded by the Airly network (dashed area) and official stations (green area). We can see how much more information about air pollution we can get when we install the Airly sensor network and the concentrations measured by the official stations are underestimated. For example in May, the maximum daily pollution measured by official stations was equal to 25-30 ug/m3 while Airly sensors have been persistently measuring daily concentrations above 75 ug/m3.
Network of measurements – identifying of hotspots and emitters
The maps below show the difference between measurements of PM10 pollution, made only by official stations, and measurements made with Airly sensors. Airly stations are quite densely spread out in Bucharest, so we can observe more separated places with greater pollution. Also, we can predict with higher certainty pollution concentration in places without sensors. There are too few official stations to get full information about specific hotspots without using Airly ones.
The map below shows selected councils with mean PM10 concentration during the heating season 2020/2021 and 2 Airly sensors/official stations per council – one with the maximum and one with the minimum concentration of PM10. Internal diversity of pollution within each council is greater than the diversity between the neighbouring councils, which points to the need for local pollution monitoring.
Ranking of councils
The greatest particulate matter pollution occurs during the cold months, due to the combustion of solid fuels and atmospheric conditions which are favorable to pollution during the winter. Therefore we developed our ranking for the heating period – from the beginning of November 2020 to the end of February 2021.
Several councils, especially Bucharest, Dolj and Iaşi, have experienced a substantial increase of the measured air pollution after taking into account the Airly sensors measurements. It clearly proves that official measurements in those areas were underestimated, mostly due to the location parameters of the monitoring stations.
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