Report: TR 2008/11

Author: Emily Wilton and Melanie Baynes, Environet Ltd

Abstract

The main air contaminant of concern in the Waikato region is PM₁₀ (particles in the air less than 10 microns in diameter). The Ministry for the Environment introduced a National Environmental Standard (NES) for PM₁₀ of 50 µg m^-3 (24-hour average) in September 2004. The NES requires air quality monitoring to take place in areas that are likely to exceed the standard for PM₁₀. However, one allowable exceedence is permitted each year. Under the NES any subsequent breach of the PM₁₀ standard must be publicly notified within a month of it occurring.

During 2007, PM₁₀ monitoring was carried out at Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata and Putaruru. In addition, monitoring of benzene, toluene and xylene was carried out in several locations in Hamilton.

In 2006 Environment Waikato decided to report air quality monitoring results on a yearly basis from 1 September to 31 August each year. This 2007 report continues with the September to August reporting period.

Results from the 2006 and 2007 monitoring period show that concentrations of PM₁₀ in excess of the NES were measured in Tokoroa, Taupo, Te Kuiti and Putaruru. The highest measurement for the monitoring period was 91 µg m^-3 (24-hour average) and was measured in Tokoroa. The maximum PM₁₀ concentration of 72 µg m^-3 (24-hour average) measured at Taupo was higher than concentrations recorded in previous years. Te Kuiti recorded a maximum PM₁₀ concentration of 58 µg m^-3 while Putaruru recorded a maximum PM₁₀ concentration of 56 µg m^-3 over a 24 hour period. Concentrations of PM₁₀ in Matamata were within the NES despite the apparent prevalence of meteorological conditions conducive to elevated concentrations. Based on these data, it would seem unlikely that PM₁₀ concentrations in Matamata would be in breach of the NES in the near future.

Eleven exceedances of the NES for PM₁₀ were recorded in Tokoroa. Six exceedances were recorded in Taupo, four in Te Kuiti and two exceedances of the NES for PM₁₀ were recorded in Putaruru.

In addition to the NES, MfE provides guidelines for ambient air quality. An annual guideline of 20 µg m^-3 is provided for PM₁₀. The (1 Sept 2006 to 31 Aug 2007) annual average PM₁₀ concentrations for Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata and Putaruru were 15, 17, 14, 17, 12 and 16 µg m^-3 respectively.

Air quality monitoring of benzene, toluene and xylene was carried out at a number of monitoring sites in Hamilton. The results suggest a decrease in benzene concentrations in Hamilton with 2007 concentrations all less than the 2010 guideline for benzene of 3.6 µg m^-3 (annual average). Concentrations of toluene and xylene were well within acceptable levels.

Air Quality Monitoring 2007 for Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata and Putaruru [PDF, 1.4 MB]