Environment Canterbury has permanent air pollution monitoring stations.
Monitoring
Environment Canterbury has permanent air pollution monitoring stations in 7 Canterbury towns: Kaiapoi, Rangiora, Christchurch (St Albans, Riccarton and Woolston), Ashburton, Timaru (town and Washdyke), Waimate and Geraldine. The Ministry for the Environment also operates a monitoring station in Christchurch (Burnside). In the past monitoring has shown that air pollution, mainly PM10, is a problem in these areas and the National Environmental Standards (NES) require us to monitor there.
What we monitor
The main contaminant that seems to be a problem in Canterbury towns is PM10. All monitoring stations ,except Riccarton, monitor this contaminant. In 2009 carbon monoxide (CO) is monitored at all permanent stations, sulphur dioxide (SO2) is monitored in Christchurch, Timaru and Ashburton. Nitrogen dioxide (NO2) is only monitored in Christchurch (St Albans, Riccarton, Burnside).
How the permanent monitoring stations work
We use a TEOM (Tapered Element Oscillating Microbalance) with a FDMS (Filter Dynamic Measurement System) to find out how much suspended particulate PM10 is in the air.
A small pump sucks air through a filter at a constant rate. The weight of the filter changes with more or less PM10 in the air, and this in turn changes the frequency of a small vibrating element in the machine. The amount of PM10 is calculated from the changed vibration, and then automatically sends the information to Environment Canterbury via the phone lines.
The hourly PM10 readings are averaged into a daily (from midnight to midnight) reading, and are also displayed as daily averages for the past week, month and winter season at each of the seven sites. More than one day a year with more than 50 micrograms of PM10 per cubic metre of air is a breach of the National Environmental Standards.
The FDMS is an additional device on the TEOM which overcomes a limitation of the TEOM system, where a quantity of particulate is vapourised along with water captured by the filter. The FDMS is able to measure both the solid and vapourised components of the particulate and meets the National Environmental Standard for air quality. FDMS have been installed in Christchurch in 2003, in Timaru in 2005, in Kaiapoi, Ashburton and Waimate in 2006 and in Geraldine and Rangiora in 2007.