Report: TR04/31

Author: Emily Wilton (Environet Ltd.)

Abstract

Monitoring of ozone concentrations was carried out by Waikato Regional Council at the Peachgrove Road monitoring site during the summer of 2003/04. This report details the results of the monitoring including a comparison to national ambient air quality guidelines for ozone, an assessment of the meteorological conditions during the monitoring period and an evaluation of the likelihood that results are typical of summer ozone concentrations in Hamilton.

The maximum measured ozone concentrations during the monitoring period were 80 µg m-3 (1-hour average) and 63 µg m-3 (8-hour average). These compare to ambient air quality guidelines of 150 µg m-3 and 100 µg m-3 respectively. The proposed national environmental standard for ozone is 150 µg m-3 (1-hour average).

A comparison of ozone concentrations to meteorological conditions in Hamilton indicates that highest concentrations occur under low wind speeds (less than 3 m s-1) and elevated temperatures (over 20 ° C). In most instances the maximum concentrations occurred during the evening (4pm to 6pm) period and are likely to be as a result of precursor emissions from the evening traffic peak. These coincided with days when temperatures remained high during the early evening period.

Daily variations in ozone concentrations show that, on average, concentrations are highest during the early afternoon (around 2pm) coinciding with the highest average daily temperatures. Concentrations of ozone typically increase from around 7am and decrease from around 2pm to 9pm.

It is likely that peak summer ozone concentrations in Hamilton would be higher than those measured during the summer of 2003/04. This conclusion is based on a comparison of wind speeds and temperatures during January to March 2004 to similar periods for 2003 and 2002. This comparison showed similar meteorology for 2003 and 2004 but higher temperatures and lower wind speeds during 2002. Concentrations of ozone in 2002 were therefore likely to be higher than those measured during 2004.

Ozone concentrations in Hamilton - Summer 2003/04 [PDF, 620 KB]