1 Summary

The GEMS monitoring sites were established to measure key air pollutants associated with adverse effects on people's health and well-being. The GEMS sites include some of the longest- running air quality monitoring sites in New Zealand. For example, various air quality monitoring has been undertaken at the Gavin Street, Penrose site in Auckland since 1964. These sites were established to determine the effects of policies for air quality management and are important for recording trends in pollution levels in New Zealand. The GEMS sites have provided long-term continuity in monitoring data for Auckland and Christchurch and provide an important snapshot of air quality for two of New Zealand's largest cities.

The two Auckland monitoring sites include a site dominated by residential and vehicle emissions (Kowhai Intermediate School, Kingsland) and a site representative of vehicle and industrial emissions (Gavin Street, Penrose). The Greers Road, Burnside site in Christchurch is located within a residential area and represents emissions from domestic properties.

Air pollutants arise from a number of different sources. Particulate matter (PM₁₀) arises from stationary and mobile combustion sources, principally domestic heating, industrial processes and vehicle emissions (as well as natural processes such as soil erosion and sea salt). Sulphur dioxide is produced from the burning of fossil fuels, particularly coal and oil. Carbon monoxide is a product of incomplete combustion of carbon containing fuels, especially from motor vehicles. Volatile organic compounds (VOCs) are organic chemicals, such as hydrocarbons, that are closely tied to vehicle emissions and many industrial processes. Historically, lead was a petrol additive but since the significant reduction of lead in petrol from 1996, levels have declined in New Zealand.

Five ambient air quality standards for carbon monoxide, nitrogen dioxide, ozone, PM₁₀ and sulphur dioxide were promulgated in October 2004. These standards are the minimum requirements that outdoor air quality must meet to guarantee a set level of protection for human health and the environment. The ambient standards are based on existing ambient air quality guidelines. Guideline levels for pollutants (and averaging periods) not covered by the standards still apply.

For most of the time, air pollutants at all sites during 2005 were below the standards. However, there were times when these standards were exceeded. One exceedance of the nitrogen dioxide 1-hour standard at Gavin Street, Penrose was found to be caused by local construction works where machinery was operating several metres from the monitoring site. The ambient air standard for NO₂ makes allowance for nine 1-hour exceedances per year before the standard is breached. At Greers Road, Burnside, there were 18 exceedances of the 24-hour standard for PM₁₀, mainly during the winter months from June to August 2005. These exceedances were most likely caused by home heating emissions. The standard allows for one exceedance of the PM₁₀ 24-hour threshold per year.