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Black Carbon Mapper

The VITO “Black Carbon Mapper" is a powerful platform which allows to get a detailed view on the street level exposure to BC of cyclists. The BC maps are constructed based on measurements by city personal and volunteers. This approach allows to map BC concentrations at a cost feasible for cities and villages. The same approach can also be used to map the exposure of pedestrians to traffic pollution.

Context

Cyclists (and pedestrians) are exposed to traffic pollution while moving around in city centers and urban environments. Their level of exposure can differ significantly from street to street. Fixed monitoring networks offer high quality data, but are unable to offer street level exposure levels. On the other hand, air quality models are able to offer detailed exposure information, but are often complex and require high-quality, up-to-date input data (e.g. detailed traffic situation, street composition, weather conditions, ...) which is not always available. Constructing detailed exposure maps based on mobile air quality measurements allows to take the numerous influencing factors into account while being able to offer a high level of detail.

Measurement methodology

Black Carbon (BC) is the ‘soot’ component of particulate matter. It is recognized by the World Health Organization (WHO) as a better indicator of harmful particulate substances from traffic than undifferentiated particulate matter (PM) mass. This makes BC an interesting component to measure for the construction of traffic pollution exposure maps. Due to both large spatial and temporal variations in BC exposure levels, repeated measurements have to be conducted. Our research indicates that to determine the average BC exposure level 10 till 20 repeated measurements are required for most streets, for each time interval of interest. To collect the required BC measurements in a cost effective way we cooperate with volunteers and city personnel. In so-called opportunistic measurement campaigns they collect measurements while commuting or while conducting their daily work tasks on the streets. This type of measurements is opportunistic because it is largely uncoordinated. With targeted measurements exposure levels on streets of interest can be mapped in a relative short time frame of a few weeks. In this case city personnel and volunteers are asked to conduct measurements on a well-defined trajectory at certain hours of the day.

Black Carbon Mapper

The “Black Carbon Mapper” is a platform from VITO to collect mobile BC measurements and to process them into street-level BC exposure maps. It contains two parts: the first part is formed by easy to use measurement devices which allow city personnel and volunteers to collect mobile BC measurements. This includes compact BC monitors, GPS and netbooks with software to transmit data and synchronize instruments. The second part is an automated data processing infrastructure, shown in the figure on the left, which constructs and updates the BC map. Processing steps include enhancement and validation of noisy second BC measurements and distorted GPS tracks (due to reflection of the GPS signal on high buildings), background correction and spatiotemporal data aggregation.

Obtained results

The “Black Carbon Mapper” platform has been successfully tested in the cities of Antwerp and Ghent. On the figure on the right interactive, online air quality maps are presented with the average BC exposure and summary statistics of multiple time intervals for each street section. The map on the left is based on opportunistic measurements by three teams of Antwerp city guards patrolling through the city during a 12 month period. The map on the right is based on two months of targeted measurements in a limited number of streets in Ghent by volunteers.