Central Otago’s air quality is improving, but more work is needed to bring it up to scratch this winter.
Air quality reports for areas throughout Otago were presented to the Otago Regional Council (ORC) last month, outlining the air quality.
The annual air quality report 2023 outlined monitoring efforts over the past year and compared data gathered against the current national environmental standards for air quality (NESAQ) limit.
The annual report also noted improvements being made to the State of the Environment monitoring network to include monitoring for PM2.5 (particulate matter with a diameter of less than 2.5 micrometres) particles which are smaller and therefore can be harmful to health.
Particulate matter was a term for a mixture of solid particles and liquid droplets found in the air.
National Institute of Water and Atmospheric Research (Niwa) conducted a spatial study in Alexandra using 42 temporary sensors to understand more about the variation in PM concentrations across the town and found peak average concentrations to be in the northwest of the town.
These concentrations were about double the concentrations in other parts of Alexandra and quite far away from ORC’s monitoring site. This was likely due to topography and wind patterns in Alexandra.
Recent research provided evidence air pollution was more dangerous at lower concentrations than previously thought and supports the lowering of existing guidelines.
Significant reductions in emissions are required to meet the NESAQ for PM10 in many Otago towns.
Continuous monitoring of PM10 was carried out in the Alexandra, Arrowtown, Central Dunedin and Mosgiel airsheds during 2023.
All sites except for Central Dunedin recorded exceedances of the NESAQ during the winter months; the limit for 24-hour PM10 being 50 micrograms per cubic metre of air.
PM2.5 was monitored in Arrowtown, Central Dunedin, Clyde, Cromwell, Milton and Wānaka. Arrowtown had the highest annual and winter average concentrations for PM2.5.
ORC’s State of the Environment monitoring network was being upgraded to include PM2.5 monitoring.
The council had the opportunity to conduct a trial study in Arrowtown and monitor black carbon from March to October last year.
Air quality appears to be improving in Arrowtown although there is plenty of room for improvement.
Data collected showed a strong seasonal pattern, with higher concentrations during winter, similar to that of PM10 in Arrowtown, but on a much smaller scale.
The two time periods in the day where black carbon was highest was between 8am-9am and between 7pm-9pm which is similar to home heating patterns found in PM10 monitoring.
Black carbon comes from incomplete combustion and size, shape and composition of black carbon particles can change as they age and react to other chemicals in the atmosphere. New Zealand research shows that black carbon concentrations are likely to be highest in areas of high traffic and high use of solid fuel burning for home heating.
