The Department for Environment Food & Rural Affairs (DEFRA) have an approved list of monitors which provide high quality data that can be used for compliance and regulatory purposes.
- Gravimetric Measurements: Particulates are captured on a filter which is weighed before and after sampling. The concentration of PM10 or PM5 can be calculated as the increase in mass of the filter divided by the volume of the sample.
- Tapered Element Oscillating Microbalances (TEOM): Particles are collected on a small oscillating filter and the change in oscillation frequency is proportional to the change in PM10 and PM5 concentrations.
- Filter Dynamics Measurement Systems (TEOM-FDMS): This operates like a TEOM but at 30⁰C rather than 50⁰C thereby reducing the loss of volatile components.
- Beta Attenuation Monitors (BAMs): Particulates are captured on a filter material and the increase in mass is determined by the attenuation of beta radiation.
- Light Scattering Monitors: This technique measures pulses from light scatted in a particular direction and generates a signal determined by the size and concentrations of particles in the same stream.
Unfortunately, due to high costs of the technology it is not currently possible to establish and maintain extensive networks that measure particulate matter pollution.
Bristol current has two PM10 monitors and two PM2.5 BAMs that are used to monitor how the city’s air quality complies with EU limits and UK Air Quality Objectives. Data from these monitors are available on the Open Data Bristol platform.
Citizen science and low-cost sensors
Citizen science is a term used for projects where volunteers or networks of volunteers carry out research-related tasks such as observation or measurement. It can help scientists with research and is great for encouraging more people to get involved with research and science in general.
In recent years, there’s been a growth of low-cost sensors for citizen science purposes. Sensors include Luftdaten, Smart Citizen Kit, Plantower and Alphasense.
These sensors have some limitations, but they can improve our understanding of particulate matter pollution. The sensors aren’t accurate enough to measure particulate matter concentrations or compliance with limit values but do provide indications of general pollution levels and pollution changes from day or day.
The real value in these low-cost sensors is how they can be used to raise awareness of air pollution and encourage people to become citizen scientists.
Bristol has a number of these sensors in operation that are owned and maintained by and the data for these sensors is also available on the Open Data Bristol platform.
Citizen sensing in Ashley, Bristol
As part of the Slow the Smoke project, we’re installing a Beta Attenuation Monitor in Ashley and a small number of low cost Luftdaten sensors. These will help us understand daily and seasonal variations of particulate matter concentrations. We will compare data from the monitors with weather and meteorological data to get a better understanding of the impact of wood and coal burning on Bristol’s air quality.