Clean air in Berlin is not a straightforward matter. Contrary to popular opinion, there are still uncertainties about the actual extent of air pollution. Although the Berlin Air Quality Monitoring Network (BLUME) measures air quality across the city, it is not able to record it in every street. This is precisely why many citizens showed an interest in taking a close look at the extent of air pollution as part of the Graefekiez pilot project, located in Berlin’s Kreuzberg district. The aim of the measurement campaign was quite simple: to measure the levels of particulate matter and soot in Graefekiez before and after a car park redevelopment, which began on July 17. Residents were equipped with air quality sensors to collect high-resolution spatial and temporal data in order to test the effects of the policy measure.
The measurement campaign ran from June to October 2023.
How were the measurements taken?
The network of participants in the neighbourhood was set up in such a way that measurements were taken not only on the road sections where car parks were redeveloped, but also in the side streets. The side streets served as a control group so that any changes in air quality could be attributed to the redevelopment measures as much as possible. With this in mind, residents measured two airborne particles - soot and particulate matter (PM2.5) - as well as traffic flow throughout the period.
It was of particular interest to record changes in the soot concentration before and after the measure. While there is already a lot of data on the influence of traffic on the relatively larger particulate matter (PM2.5), this is not the case for the smaller soot particles, especially on the local level. In order to test the development of the soot concentration in Graefekiez, measurements were taken exclusively with soot sensors on the streets with car park changes.
The particulate matter measurements, on the other hand, provided a detailed insight into the development of local air quality over a period of several months. To increase the credibility of the data, the particulate matter measurements were compared with two BLUME measuring stations, one in Nansenstraße and one at Müggelsee.
Figure 1. Red lines indicate road sections where car parks are being receveloped
Results of the measurement campaign
Particulate matter
According to the World Health Organisation (WHO), the average daily exposure to particulate matter PM2.5 should not exceed 15 µg/m3 on more than three to four days per year. In this context, the figures below show the average particulate matter pollution and how often it exceeded the limit value.
The average particulate matter pollution of the citizen science measurements was below 5µg/m3 over the entire period. This means that the values are among the lower average values for the entire year. This is not surprising, as higher pollution levels are to be expected during the winter period. In contrast, the average particulate matter pollution at the two BLUME stations was 7-8 µg/m3. Although the values from local residents are slightly lower compared to official measurements, the difference is not that big. The dispersion of the values - i.e. the differences between the maximum and minimum values - is also quite small, which indicates good, consistent measurements.
Figure 2. Comparison of citizen science sensors with reference-grade BLUME stations
Looking at the time interval of the measurements (Figure 3), there are also no major differences between the official BLUME and COMPAIR measurements, although the official values tend to be slightly higher. The reason for the small differences is largely due to the sensor technology itself. The high-quality sensors utilise a highly developed measuring technique that is better able to detect the concentration of particulate matter in the event of major weather fluctuations. Nonetheless, all measurements follow similar trends, such as the peaks in mid-June or mid-September. According to COMPAIR partner VMM (Flemish Environment Agency), these peaks were caused by the forest fires in Canada during the summer period.
Figure 3: The time interval of measurements collected by citizen science and reference monitors
Soot
The effects of the car park redevelopment were primarily tested for soot concentrations. The data was analysed using measurements at two locations. One location was in the section of Graefestraße where the measure was implemented, the other was in the section of Schönleinstraße where no measures were taken. It must be pointed out that the data was not always collected continuously, which makes it difficult to draw clear conclusions regarding the effect of the car park unsealing. This applies in particular to the measurements in Böckhstraße, where no data was collected, and in Graefestraße, where no data could be collected between June 23 and August 8. The reason for this were technical errors. In addition, some measurements were also taken during the holiday period when the traffic flow was generally lower. These patterns can be seen in Figures 4 and 5.
Figure 4. Soot concentrations in Schönleinstraße
Figure 5. Soot concentrations in Graefestraße
As can be seen above, the values in Graefestraße were always lower than in Schönleinstraße, both before and after the implementation of the measures. Nevertheless, the boxplots below summarise the data and show a relative reduction in soot concentration. The result is all the more meaningful because, despite incomplete data collection, very similar time periods were compared. In fact, the measurements covered the exact same time period after the implementation of the measure. . Although the reduction in soot pollution could have been caused by many other factors (in addition to the low traffic flows in summer, weather conditions also play a major role), the effect of car park redevelopment cannot be completely ruled out - especially in view of the fact that the results reflect the inclusion of at least one suitable "control street" (Schönleinstraße). In addition, as with the particulate matter measurements, the dispersion of the values was relatively low, which strengthens the validity of the measurements.
Figure 6. Emissions in the Graefekiez before and after car park recevelopment
The Policy Monitoring Dashboard (PMD) will offer even better insight into the results of citizen science experiments in the future. The two version of the dashboard can be accessed via the two links below.
Prospects for further projects
After the Graefekiez pilot project it became clear that the implementation of citizen science experiments is not only possible, but also offers promising prospects for cooperation between citizens and the city administration. With the right tools, inquisitive residents, a forward-thinking administration and a clear idea, citizen science experiments can be used for concrete research projects, such as monitoring mobility measures.
In the future, ambitious residents or the administration itself can initiate such projects to test the impact of various policy measures. The PMD services this purpose well. The Berlin Senate Department for Mobility, Transport, Climate Protection and the Environment has been informed about the opportunity and already showed interest in supporting the dissemination of the tool. Berlin’s District Offices in particular could benefit from this open source product.
Before that happens, however, the public round of measurement campaigns has yet to take place, which will run from February to June 2024. This time, the mobility measures in the Bellermann neighbourhood in Wedding will be compared with the Neukölln neighbourhoods of Donaustraße and Flughafenstraße, where there are no traffic measures in place. You can expect more results to be published here in the coming months. Stay tuned!
Berlin pilot managers
Vlatko Vilovic: vilovic@inter3.de
Gesine Wilbrandt: wilbrandt@inter3.de