Report: TR 2010/23
Author: T Mathieson
Stratospheric ozone performs the beneficial role of reducing the intensity of ultraviolet light reaching earth. In contrast, ozone causes several undesirable effects at ground level and is the key indicator of photochemical air pollution that results from vehicular exhaust fumes.
Regional councils are instructed under the Ministry for the Environment’s National Environmental Standards to monitor locations most at risk of significant ozone accumulation. Given that the two main prerequisites for photochemical air pollution are traffic
emissions and sunlight, and photochemical air pollution often materializes downwind from the source of precursor molecules it was thought likely that the highest concentrations of ozone over land in the Waikato region may be downwind of air pollutants generated by vehicles within the Auckland region. Prevailing westerly winds will drive these pollutants toward the western coast of the
Waikato Regional Council commissioned Watercare Services to conduct continuous ambient monitoring at the town of Coromandel, rationalising that reactive air masses generated from Auckland traffic are primarily transported in that direction by the prevailing westerly winds. During three consecutive monitoring periods in 07/08, 08/09 and 09/10, the highest level of ozone detected was 90.5 μg/m3, calculated as a one hour mean, which is significantly less than the NES threshold of 150 μg/m3.
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