Outdoor Air Quality monitoring

Pegasor Urban Air Monitoring System

Pegasor Urban Air Monitoring System (PUAMS) is based on a dense Pegasor Particle Sensor (PPS) network.  The network provides real-time spatial information on particle concentration (both PM2.5 and PN2.5) in the urban area.  Air Quality network design is an important issue for the network functionality. The PPS sensors need to be placed at representative spots, like highways, local streets, parks, industrial areas, areas with small scale combustion, etc. The design is preferably carried out with the city authorities or local environmental officers. The design will be done in accordance with local air quality standards and criteria for air quality monitoring. The online fixed air quality monitoring network can be used to assess the compliance with the air quality standards and limit values. The network design will be done with Finnish experts, including such authorities like Finnish Meteorological Institute.

PPS has been designed to be sensitive to all particles smaller than 2.5 micrometers in diameter (PM2.5). Urban combustion emissions typically produce particles smaller than 500 nm in diameter and PPS is extremely sensitive to such particles, thus making the sensor network very suitable for local emission sourcing. It should be noted that optical particle sensors cannot detect particles smaller than 200 nm, thus missing most of urban particles.

The sensors are continuously calibrated with the help of reference PM2.5 and PN2.5 equipment. The system hardware also includes meteorological sensors placed to the reference equipment stations. 

All data is transferred from sensors and reference stations to a platform (data storage) via internet.  The platform includes modules for data reliability analysis.

Data, software and graphic interfaces

The key software of the system is the FUSION model. It has originally been developed by the Finnish Meteorological Institute (FMI) and Helsinki Region Environmental Services Authority (HSY) in the European PESCaDO project.

The model analyses and combines the available sensor data and provides, on a map, a detailed model about the air quality of the urban area. The data from all nodes is fused to ensure the availability of a most reliable and comprehensive data set as basis for further processing stages. This implies an assessment of the quality of the contributing services and data.

Optionally PUAMS can be developed to include Air Quality Forecasting model. This is possible if the local weather forecast data is available and provided. The Fusion model can be used for air quality forecasting if the numerical weather forecast data is available and can be used as input data for the model. Model needs to be evaluated after it has started operation against the fixed air quality monitoring results.

Configuration of PUAMS

The core of the system is the dense particle sensor network based on PPS. The network is designed by Finnish guidance together with local experts to find representative placement of sensors. Calibration equipment and meteorological sensors are placed on calibration stations. Information on the location of the sensors needs to be provided by the local experts. 

Data platform is installed to a suitable server and the platform collects quality assured interoperable data from the sensors and calibration stations. Data (weighted by reliability factor) is used in the fusion model to calculate spatially accurate information on air quality distribution in the urban area. If weather forecast data is available (input to fusion model), also air quality forecasts can be provided.

Data is visualized on map, one interface providing overall view (to be used by citizens) and another interface providing the authority view (measurement results from each individual sensor available). If the data is opened for use, also various applications can be built on the data.