What other methods can be used for air quality monitoring?

Description

Besides sensing device technologies, several other methods can be used for environmental monitoring in the context of Citizen Observatories, each with its own advantages and limitations. By employing a combination of these methods, air quality monitoring initiatives can obtain comprehensive and reliable data to assess air quality, identify sources of pollution, and inform decision-making to protect public health and the environment.

Why is this relevant?

For some pollutants, sensing devices are still expensive or their data quality is not good enough for the needs of the COs’ initiative. Understanding the different types of monitoring is crucial for Citizen Science initiatives aimed at engaging volunteers in environmental data collection efforts. By familiarizing themselves with various monitoring methods, Citizen Science practitioners can select approaches that are accessible, cost-effective, and suitable for non-experts. This knowledge enables organizers to design monitoring protocols that align with the skills and resources of citizen scientists while ensuring the collection of meaningful and reliable data. One of the most common alternatives for sensing devices used by citizen scientists is passive sampling.

How can this be done?

Some alternative methods to sensor devices include:

Reference and regulatory monitoring stations: These are sophisticated monitoring stations operated by government agencies or research institutions. They use high-quality, calibrated instruments to measure air pollutants according to established regulatory standards. Reference stations provide accurate and reliable data for compliance monitoring and trend analysis but are expensive to operate and maintain, limiting their spatial coverage. Although they cannot be operated by non-experts, their data is usually open and accessible for all to read and use.
Remote sensing: Remote sensing techniques, such as satellite imagery and aerial surveys, can provide valuable information on air quality over large geographical areas. Remote sensing data can be used to monitor pollutants such as particulate matter, ozone, and nitrogen dioxide, and to identify sources of pollution. The advantage of satellite data is that the measurements are usually collected globally with the same instrument. There are also disadvantages. Remote sensing often still lacks the spatial resolution needed for detailed localized monitoring. Also, the satellite measurements are done over a column (e.g. it accounts for the air pollutants from the ground to the top of the atmosphere), at a certain overpass time during the day, when there are no clouds. Satellite data are complex to work with and many satellite images are not open data or need to be purchased. Nevertheless, the global coverage means that also places were other types of data are scarce or unavailable are reached. In some cases, Citizen Science data and satellite data may complement and strengthen each other, see Citizen_Science_meets_Remote_Sensing_December 2024.
Passive sampling: Passive sampling involves deploying samplers, such as diffusion tubes or badges, at various locations to collect air samples over a specific period. These samples are then analyzed in a laboratory to measure pollutant concentrations. Passive sampling is cost-effective and suitable for long-term monitoring but may provide less real-time data compared to active monitoring methods. Most common are passive samplers for nitrogen dioxide (NO2), but passive samplers for ammonia (NH3), sulpur dioxide (SO2) or ozone (O3) are also available. The most used passive samplers are the Palmes diffusion tubes, which are particularly useful for dense coverage in a specific geographic region, such as a city. The tubes are about 7 cm long and contain a cap with a chemical on a metal mesh that can bind e.g. NO2 or NH3. By hanging the tube outside for typically a month or four weeks, the pollutant collects in the chemical in the tube. A chemical analysis is done to determine the average NO2 or NH3 concentration at the location where the tube was placed. This measurement method provides monthly averaged concentration values. The analysis takes a few weeks to complete, so results are slow, and the data is not collected automatically. Passive samplers are used by scientists and authorities, but they are also being used in Citizen Science projects where dense coverage is desired or financial resources for Sensing Devices are limited. For NO2, passive samplers have the added value that they are accepted as “indicative” measurement method. This gives the possibility to use them for compliance assurance. The quality of the data produced by NO2 passive samplers is well defined and relatively high. Also, the tubes are very simple to use, do not need electricity or Wi-Fi, and the price per tube is low, around 15 euro per tube including analysis.
Collection of air samples: Chemical analysis techniques, such as gas chromatography and mass spectrometry, can be used to quantify air pollutants with high precision and accuracy. These methods are typically performed in laboratory settings using collected air samples. Chemical analysis provides detailed information on pollutant concentrations and composition but may require specialized equipment and expertise. Although collecting air samples usually involves experts, it is possible also to develop protocols for citizens to be able to collect samples.
Collection of pollution on surfaces: A very simple technique to determine air pollution is to look at particulate matter deposited on surfaces. Strawberry plant leaves were used in the AIRbezen project in Antwerp, Belgium. The leaves were analyzed for the presence of heavy metals. Pieces of paper covered with a thin layer of Vaseline were used in the Fresh Air for All project in Norway. Here school children analysed the pieces of paper left outside by counting the particles collected on the paper.
Air quality modelling: Models are not a monitoring method, but they are complementary to monitoring and, in many circumstances, used together to enhance our knowledge about air pollution spatial and temporal distribution. Air quality models simulate the transport, transformation, and dispersion of air pollutants in the atmosphere based on meteorological data, emission inventories, and chemical reactions. These models can predict air pollutant concentrations and assess the impacts of emissions reduction strategies. Air quality modeling provides insights into complex atmospheric processes but requires specialized software and input data. More and more models are also be made open and accessible, with the code published online as well as the data.

Useful resources

Official measurements in Europe Up-to-date air quality data — European Environment Agency (europa.eu)
Infographic on how Palmes tubes work for NO2 Over CurieuzeNeuzen – Curieuzeneuzen.
Article in English about a citizen science project with Palmes tubes to help interpret NO2 satellite data Citizen_Science_meets_Remote_Sensing_December 2024

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Description

Why is this relevant?

How can this be done?

Some alternative methods to sensor devices include:

Reference and regulatory monitoring stations: These are sophisticated monitoring stations operated by government agencies or research institutions. They use high-quality, calibrated instruments to measure air pollutants according to established regulatory standards. Reference stations provide accurate and reliable data for compliance monitoring and trend analysis but are expensive to operate and maintain, limiting their spatial coverage. Although they cannot be operated by non-experts, their data is usually open and accessible for all to read and use.

Remote sensing: Remote sensing techniques, such as satellite imagery and aerial surveys, can provide valuable information on air quality over large geographical areas. Remote sensing data can be used to monitor pollutants such as particulate matter, ozone, and nitrogen dioxide, and to identify sources of pollution. The advantage of satellite data is that the measurements are usually collected globally with the same instrument. There are also disadvantages. Remote sensing often still lacks the spatial resolution needed for detailed localized monitoring. Also, the satellite measurements are done over a column (e.g. it accounts for the air pollutants from the ground to the top of the atmosphere), at a certain overpass time during the day, when there are no clouds. Satellite data are complex to work with and many satellite images are not open data or need to be purchased. Nevertheless, the global coverage means that also places were other types of data are scarce or unavailable are reached. In some cases, Citizen Science data and satellite data may complement and strengthen each other, see Citizen_Science_meets_Remote_Sensing_December 2024.

Passive sampling: Passive sampling involves deploying samplers, such as diffusion tubes or badges, at various locations to collect air samples over a specific period. These samples are then analyzed in a laboratory to measure pollutant concentrations. Passive sampling is cost-effective and suitable for long-term monitoring but may provide less real-time data compared to active monitoring methods. Most common are passive samplers for nitrogen dioxide (NO2), but passive samplers for ammonia (NH3), sulpur dioxide (SO2) or ozone (O3) are also available. The most used passive samplers are the Palmes diffusion tubes, which are particularly useful for dense coverage in a specific geographic region, such as a city. The tubes are about 7 cm long and contain a cap with a chemical on a metal mesh that can bind e.g. NO2 or NH3. By hanging the tube outside for typically a month or four weeks, the pollutant collects in the chemical in the tube. A chemical analysis is done to determine the average NO2 or NH3 concentration at the location where the tube was placed. This measurement method provides monthly averaged concentration values. The analysis takes a few weeks to complete, so results are slow, and the data is not collected automatically. Passive samplers are used by scientists and authorities, but they are also being used in Citizen Science projects where dense coverage is desired or financial resources for Sensing Devices are limited. For NO2, passive samplers have the added value that they are accepted as “indicative” measurement method. This gives the possibility to use them for compliance assurance. The quality of the data produced by NO2 passive samplers is well defined and relatively high. Also, the tubes are very simple to use, do not need electricity or Wi-Fi, and the price per tube is low, around 15 euro per tube including analysis.

Collection of air samples: Chemical analysis techniques, such as gas chromatography and mass spectrometry, can be used to quantify air pollutants with high precision and accuracy. These methods are typically performed in laboratory settings using collected air samples. Chemical analysis provides detailed information on pollutant concentrations and composition but may require specialized equipment and expertise. Although collecting air samples usually involves experts, it is possible also to develop protocols for citizens to be able to collect samples.

Collection of pollution on surfaces: A very simple technique to determine air pollution is to look at particulate matter deposited on surfaces. Strawberry plant leaves were used in the AIRbezen project in Antwerp, Belgium. The leaves were analyzed for the presence of heavy metals. Pieces of paper covered with a thin layer of Vaseline were used in the Fresh Air for All project in Norway. Here school children analysed the pieces of paper left outside by counting the particles collected on the paper.

Air quality modelling: Models are not a monitoring method, but they are complementary to monitoring and, in many circumstances, used together to enhance our knowledge about air pollution spatial and temporal distribution. Air quality models simulate the transport, transformation, and dispersion of air pollutants in the atmosphere based on meteorological data, emission inventories, and chemical reactions. These models can predict air pollutant concentrations and assess the impacts of emissions reduction strategies. Air quality modeling provides insights into complex atmospheric processes but requires specialized software and input data. More and more models are also be made open and accessible, with the code published online as well as the data.