Ozone levels in air

Methods - how we monitored

• Where and how we collected the data

  Monitoring sites

  Hamilton's ozone monitoring site was at Peachgrove Road. We suspected Hamilton had the highest concentrations of nitrogen dioxide and volatile organic compounds present in the air anywhere in the Waikato. These are the pollutants that react to form ozone.

  Monitoring frequency

  Ozone data were collected continuously in Hamilton during the summer months (November to April) and reported as hourly average concentrations.

  Monitoring history

  Monitoring for ozone in the air we breathe is not a priority in many areas of New Zealand, because conditions are not considered conducive to ozone formation. However, a 1997 report identified Hamilton as having the potential for elevated ozone concentrations. This was based on an assessment of meteorological conditions, and because of the presence of emissions of the precursor contaminants, nitrogen dioxide and volatile organic compounds.

  The first monitoring of ozone was carried out in Hamilton during the summer of 2003/04.

  Measurement technique

  Monitoring was carried out using a Thermo Environmental model 49 ozone analyser. This uses the technique of UV absorption to determine concentrations of ozone. Concentrations of ozone were measured in parts per billion and converted to micrograms per cubic metre (µg/m³) based on standard New Zealand conversions.

   
• How this indicator was compiled

  Monitoring results are reported in relation to the Waikato Regional Plan, using the Ministry for the Environment air quality indicator reporting framework outlined in the table below. This framework is used to report on air quality for a range of contaminants relative to their respective guidelines.

  Table 1: Ministry for the Environment categories for air quality

  Category	Value relative to guideline	Comment
  Excellent	Less than 10% of the guideline	Of little concern, if maximum values are less than a tenth of the guideline, average values are likely to be much less
  Good	Between 0% and 33% of the guideline	Peak measurements in this range are unlikely to affect air quality
  Acceptable	Between 33% and 66% of the guideline	A broad category, where maximum values might be of concern in some sensitive locations but generally they are at a level which does not warrant dramatic action
  Alert	Between 66% and 100% of the guideline	A warning level, which can lead to the guideline being exceeded if trends are not curbed
  Action	More than 100% of the guideline	Exceeding the guideline is a cause for concern and warrants action if it occurs regularly

  Tables 2 and 3 show the percentage of times ozone levels fell into each category, the maximum level for the month and the number of times ozone levels went above the proposed regional guideline during the periods each site was monitored.

  Table 2: Summer 2003/04 one hour carbon monoxide levels at Hamilton

  Year	Categories					Maximum value (µg/m3)	Number of times levels exceeded the proposed regional guidelines
  	Excellent	Good	Acceptable	Alert	Action
  December 03	28%	71%	1%	0%	0%	65	0
  January 04	42%	55%	3%	0%	0%	80	0
  February 04	19%	80%	1%	0%	0%	56	0
  March 04	54%	44%	1%	0%	0%	66	0

  Table 3: Summer 2003/04 eight hour carbon monoxide levels at Hamilton

  Year	Categories					Maximum value (µg/m3)	Number of times levels exceeded the proposed regional guidelines
  	Excellent	Good	Acceptable	Alert	Action
  December 03	8%	82%	10%	0%	0%	49	0
  January 04	20%	67%	14%	0%	0%	63	0
  February 04	5%	86%	9%	0%	0%	48	0
  March 04	40%	55%	5%	0%	0%	46	0

   
• Guidelines and standards

  The proposed regional guidelines and national ambient air guidelines for ozone have been set at:

  • 150 µg/m³ (one hour average)
  • 100 µg/m³ (eight hour average, MfE, 2002).

  In 2004 the Ministry for the Environment (2003) released National Environmental Standards for air quality which include a value for ozone of 150 µg/m³ averaged over one hour.

   
• Limitations

  Waikato Regional Council only has ozone data for Hamilton. Other areas where ozone concentrations may be elevated include rural areas on the outskirts of Hamilton, and possibly on the Coromandel, as a result of transportation of emissions from the Auckland Region.