City-Sonde Science (CSS)

Innovative air quality measurements from a bicycle basket

How clean is the air we breathe when commuting on our bicycles? Since June 2015, researchers and students at KNMI have been cycling trying to find the answer to this question by measuring nitrogen dioxide (NO2) in a project that is called “City-Sonde Science” (CSS). KNMI has developed a nitrogen dioxide sensor suitable for monitoring nose-level air pollution that is coupled to a mobile weather station and GPS. Hereby measurement of the amount of nitrogen dioxide at street level is possible. Highlights of this project include the identification of NO2 hotspots, impact of car-free zones, and the influence of highways on local air quality.

High resolution and manageable size
Accurate measurement of NO2 and high temporal resolution of one measurement per second combined with a manageable size (fits in a bicycle basket) is unique in the world of nitrogen dioxide sensors. These features make the NO2-sonde suitable for deployment on mobile platforms such as drones, bicycles, and balloons. These bicycle measurements are ideal for fast and accurate, high spatial resolution mapping of NO2 since its concentration changes rapidly.

New measurement applications
This innovative, flexible way of measuring is a valuable addition to stationary air quality monitoring methods that yield hourly or monthly averages. The increasing spatial resolution of future satellite instruments, requires new validation techniques to gather information about NO2 variability on a city scale. The NO2-sonde bicycle measurements bridge spatial and temporal coverage gaps inherent to other measurement techniques and can be used to investigate local-scale air quality issues. As our project name implies, this approach is accessible and therefore well-suited for citizen science including community and educational (high school) outreach. The full scientific and societal potential of this multi-faceted instrument and platform are just beginning to be explored.

Go on a bicycle ride and measure nitrogen dioxide!