Report: TR05/07

Author: Emily Wilton (Environet)

Abstract

This report presents results of ambient air quality monitoring carried out by Environment Waikato during 2004. Monitoring sites were located in Hamilton, Tokoroa, Te Kuiti and Taupo.

The main air contaminant of concern in the Waikato region is suspended particles (PM10). In September 2004, the Ministry for the Environment introduced a National Environmental Standard (NES) for PM10 of 50 µg m-3 (24-hour average) with one allowable exceedence each year. The NES is effective from September 2005.

Concentrations of PM10 were measured at all locations, with the Hamilton site also measuring carbon monoxide (CO), and benzene. Benzene was also monitored at a "traffic peak" monitoring site in Bridge Street, Hamilton.

Tokoroa measured the worst PM10 concentrations in terms of both magnitude and frequency of exceedence. During 2004, the maximum measured PM10 concentration was 97 µg m-3 and 41 exceedences of 50 µg m-3 were measured. This compares with a previous maximum of 75 µg m-3 (measured in 2001) and a maximum of 15 measured exceedences (for 2002).

In Hamilton, measured PM10 concentrations exceeded 50 µg m-3 on one occasion reaching 55 µg m-3 (24-hour average). Monitoring was carried out using a TEOM analyser with a sample temperature of 40 ° C. Additional monitoring of PM10 at the Hamilton site was carried out using a high-volume sampler to determine the relativity between this reference method and the TEOM. Unlike other locations in New Zealand, the difference between the TEOM and high-volume sampling methods was not significant. No adjustments for gravimetric equivalency were therefore made to 2004 or historical TEOM data. The annual average PM10 concentration in Hamilton during 2004 was 17 µg m-3, which is less than the annual average guideline of 20 µg m-3.

Carbon monoxide concentrations in Hamilton during 2004 were well within air quality guidelines and the NES for CO. Results were consistent with previous years with most measurements falling within the "excellent" or "good" air quality indicator categories. The maximum hourly average CO concentration of 9 mg m-3 compares to an hourly guideline of 30 mg m-3. The maximum 8-hour average concentration was 7 mg m-3, over two thirds of the 8-hour guideline of 10 mg m-3.

In Te Kuiti, concentrations exceeded 50 µg m-3 (24-hour average) on 5 occasions with a maximum measured 24-hour average of 62 µg m-3. In Taupo, monitoring was carried out every third day rather than daily. Two breaches of 50 µg m-3 were measured during 2004, with a maximum PM10 concentration of 65 µg m-3. If data are extrapolated statistically for missing data, the number of breaches could be around 6.

Annual average PM10 concentrations in Te Kuiti and Taupo are estimated at less than the 20 µg m-3 guideline.

All areas show similar seasonal variations in PM10 concentrations, with higher values occurring during the winter months.

No clear trends in contaminant concentrations were apparent at any of the monitoring sites.

Air Quality Monitoring 2004 [PDF, 627 KB]