1 Introduction
This report provides a summary of the results of air quality monitoring of carbon monoxide (CO), nitrogen dioxide (NO2), sulphur dioxide (SO2), ozone (O3), benzene and benzo(a)pyrene in New Zealand from 1992 to 2002.
Prior to the introduction of the Resource Management Act (RMA) in 1991, air quality monitoring in New Zealand was the responsibility of the then Department of Health. Monitoring at that time was mainly conducted in the larger urban centres of Christchurch and Auckland, although some smoke monitoring was carried out in the smaller towns. Air quality monitoring in Auckland and Christchurch prior to 1991 included CO, NOx, SO2, lead and particles. Concentrations were typically compared to international guidelines such as those set by the World Health Organisation (WHO).
With the RMA came a shift in the responsibility for air quality to regional councils. Specific requirements under Sections 35 and 30 of the RMA include air quality monitoring and management. As a result, air quality monitoring networks were established and expanded throughout the country during the 1990s.
In 1994, the Ministry for the Environment developed a set of ambient air quality guidelines for key air contaminants in New Zealand (MfE, 1994). These included health related guideline values for CO, PM10, SO2, NO2, O3, hydrogen sulphide (H2S), and lead. A review of these guideline values and their application was carried out during the late 1990s and a discussion document on this review was released in December 2000 (MfE, 2000). In May 2002, the final updated ambient air quality guideline values were released (MfE and MoH, 2002). This document includes revised guideline values of the contaminants in the 1994 document as well as guideline values for new contaminants including benzene, 1,3 butadiene, formaldehyde, acetaldehyde, benzo(a)pyrene, mercury, chromium and arsenic. The guideline values for contaminants that are discussed in this report are shown in Table 1.2.
The Ministry for the Environment has also established an Environmental Performance Indicators programme to collate and report air quality data. The programme aims to improve the quality, quantity and reporting of air quality monitoring. Through the signing of partnership agreements, councils have agreed to undertake specific monitoring and to provide the data for reporting over a national website. As part of the obligations under the agreements, councils will have the opportunity to comment on this report prior to its release.
The monitoring procedures used by regional councils mostly follow the recommendations outlined in the Ministry's Good Practice Guide for Air Quality Monitoring and Data Management. This document includes a description of monitoring methods and data collection and processing protocols for New Zealand. One of the recommended reporting methods for presenting air quality data is the use of air quality categories based on a proportion of the guideline value (Table 1.1). These categories are used to present air quality data. These are generally presented based on air quality monitoring results for each year of monitoring. However, in locations where monitoring was limited to shorter time periods, results have been presented on a monthly basis.
Other data reported includes the number of guideline breaches, the maximum measured concentration, the 99.5 percentile concentration for 24-hour averages and the 99.9 percentile concentration for hourly and eight-hour averages. The number of guideline exceedences has been extrapolated for each year based on the proportion of days or hours monitored. For example, if three guideline value exceedences were measured, but sampling only took place for one half of the year, the estimated number of exceedences would be six. This extrapolation includes an adjustment for seasonal variations. An example of the equation used to estimate the number of exceedences per year for a 24-hour average guideline value is shown in Equation 1.1.
Equation 1.1: No. > guideline (May-August) x [123/days monitored (May-August)] + No. > guideline (January-April, September-December) x [242/days monitored (January-April, September-December)]
Table 1.1: Ministry for the Environment's air quality categories
View Ministry for the Environment's air quality categories (large table)
Table 1.2: Summary of the ambient air quality guidelines for contaminants discussed in this report
| Contaminant | 2002 guideline valuesa | |
|---|---|---|
| Concentration | Averaging period | |
|
Carbon monoxide |
30 mg m-3 |
One-hour |
|
Nitrogen dioxide |
200 µg m-3 |
One-hour |
|
Sulphur dioxideb |
350 µg m-3 |
One-hour |
|
Ozone |
150 µg m-3 |
One-hour |
|
Benzene (year 2002) |
10 µg m-3 |
Annual |
|
Benzo(a)pyrene) |
0.0003 µg m-3 |
Annual |
Source: MfE and MoH, 2002
Notes:
a All values apply to the gas measured at standard conditions of temperature (0°C) and pressure (1 atmosphere).
b The sulphur dioxide guideline values do not apply to sulphur acid mist.
Each section in this report provides a brief description of the recommended monitoring methods for that contaminant, followed by sections outlining the state or concentrations in each region where monitoring is carried out.
1.1 Air quality monitoring in New Zealand
The number of air quality monitoring sites and the range of contaminants monitored in New Zealand has expanded over the last decade. While suspended particulate (PM10) is the priority contaminant for air quality monitoring in most regions, measurements of other contaminants such as CO and NO2 are also common. In Auckland, extensive monitoring has also been carried out for O3 and in Christchurch, concentrations of SO2 are also routinely measured. Concentrations of benzene and benzo(a)pyrene have been measured in some locations in recent years, although this monitoring tends to be for a shorter term, rather than continuous sampling. A summary of the air quality monitoring sites within New Zealand and the contaminants that have been measured is provided in Appendix One.
