Air quality 2009/10
Key points:
• Air pollution levels are typically low in the region with only occasional episodes of poor air quality in some valley areas during winter.
• Particulate matter (PM10) is the only pollutant measured that failed to meet the national environmental standard for air quality.
• During winter 2010, high pollution levels were recorded on four nights in Masterton, one night in Carterton and on one night in Wainuiomata. In winter 2009, there was only one high pollution night, recorded in Masterton.
• Air pollution levels measured beside busy roadsides in central Wellington and Lower Hutt meet national environmental standards and guidelines.
What happened in 2009/10?
Regional air quality
Greater Wellington monitored air quality at selected sites in the region. Three key pollutants were measured – particulate matter (PM10), carbon monoxide and nitrogen dioxide – and the results compared against the national environmental standards and guidelines set to protect public health.
Levels of PM10 in air throughout the year are mostly “good”. Masterton and Wainuiomata are susceptible to pollution from domestic fires. On still, cold and clear nights, smoke containing particulate matter (PM10) accumulates and is not dispersed until the following morning when the ground heats up and the air starts to circulate. In 2009 air quality reached the “alert” level on 15 days in Masterton and four days in Wainuiomata. The national environmental standard was exceeded only on one day and this occurred in Masterton.
Carbon monoxide concentrations were mostly “excellent” and reflect the national trend for lower emissions from petrol vehicles due to improvements in vehicle technology. Nitrogen dioxide levels were generally “excellent”, except for the central Wellington site where levels were mostly “good”.
Roadside air quality
Air quality measured at our central Wellington monitoring station showed that levels of PM10, nitrogen dioxide and carbon monoxide in 2009 were all well within the limits set by the national environmental standards. Traffic count data supplied by Wellington City Council were matched to average hourly concentrations of nitrogen dioxide. During week days the level of nitrogen dioxide (NO2) reflects the morning and evening rush hour as vehicles travel southeast along Vivian Street and southwest along Victoria Street. During the weekend levels of nitrogen dioxide show a flatter, more sustained peak as traffic volumes are spread over most of the day.
The graphs show the average hourly traffic volumes during one week in August 2009 passing the central Wellington air quality station on the corner of Victoria and Vivian streets. Average concentrations of nitrogen dioxide (NO2) are also shown.
Winter air quality in 2010
In winter 2010 we expanded our Wairarapa PM10 monitoring programme to include Carterton. Air quality reached the “alert” level on 19 days in Masterton, nine days in Carterton and three days in Wainuiomata. The national environmental standard was exceeded on four days in Masterton, and on one day in both Carterton and Wainuiomata.
This dot graph shows the number of high pollution days (red dots) and “alert” days (orange dots) recorded over May to August 2010 in Masterton, Carterton and Wainuiomata
Air quality investigation in Carterton
In winter 2009 we collected samples of particulates in air over a two-week period for source ‘finger-printing’ by GNS Science. Most of the PM10 measured in air was made up of the smaller-sized particles measuring less than 2.5 microns (PM2.5). These smaller particles present the greatest risk to health because they can penetrate deep into the lungs. The majority of the PM2.5 was composed of organic compounds and black carbon (soot) typically associated with emissions from woodburners. Natural sources such as sea salt and soil made only a minor contribution to PM10 levels in air.
Scanning electron microscopy image of a filter used to collect particulate matter. The larger particles are sea salt. The extremely small particles (white specks) that can just be seen at this magnification are combustion particles that are 50 times smaller than the width of a human hair.
What is Greater Wellington doing?
• Monitoring air quality at selected sites around the region, including Wellington, Lower Hutt, Upper Hutt, Wainuiomata, Karori, Tawa and Masterton.
• Carrying out a short-term study on winter air quality in Raumati South, Kapiti Coast.
• Offering financial assistance for home insulation and clean heating in connection with the EECA Energywise programme through the ‘Warm Greater Wellington’ targeted rate scheme (http://www.gw.govt.nz/warmer-gw).
What can you do?
• Insulate your house effectively and burn only dry untreated wood in your fireplace. After starting the fire, leave the air vent open for at least half an hour to create a hotter, cleaner burning fire.
• Don’t burn rubbish or treated timber in your fireplace or outside. Send paper and plastic for recycling and compost green waste.
• Keep your vehicle tuned and serviced to reduce smoke and fumes.
More information
Some of the information on this card is a summary of the 2009 annual air quality monitoring report, which is available at www.gw.govt.nz/envreports
If you would like to know more about air quality, visit our website or contact us:
Phone: 04 384 5708 (Wellington office) or 06 378 2484 (Masterton office)