Report: TR 2009/04

Author: Emily Wilton, 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 National Environmental Standard (NES) for PM10 requires that by 2013 a maximum concentration of 50 µg m-3 (24-hour average) is not exceeded more than once a year. Under the NES any subsequent breach of the PM10 standard must be publicly notified within a month of it occurring. The NES requires air quality monitoring to take place in areas that are likely to exceed the standard for PM10.

During 2008, PM10 monitoring was carried out at Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata, Putaruru, Ngaruawahia and Waihi. Monitoring for benzene, toluene and xylenes and polycyclic aromatic hydrocarbons (PAHs) also took place in Hamilton. Dual measurements were undertaken at the Hamilton, Tokoroa, Taupo and Te Kuiti monitoring stations, allowing external validation and (where necessary) site-specific correction of PM10 data from those locations.

Results from air quality monitoring throughout 2008 show that PM10 concentrations in excess of the NES were measured in Tokoroa, Taupo, Te Kuiti and Putaruru. Twelve exceedences of the NES for PM10 were recorded in Tokoroa and Taupo, and three exceedences were recorded in Te Kuiti. In Putaruru two concentrations in excess of 50 µg m-3 were recorded in the summer months and occurred as a result of roadworks. Overall, the highest measurement for the monitoring period was 85 µg m-3 (24-hour average) and was measured in Tokoroa. Taupo recorded a maximum PM10 concentration of 76 µg m-3 (24-hour average). This represents the highest 24-hour average PM10 concentration measured in Taupo with the previous maximum of 72 µg m-3 being measured in 2007. The maximum recorded PM10 concentration for Te Kuiti was 69 µg m-3. The maximum wintertime PM10 concentration for Putaruru was 50 µg m-3 (24-hour average), which is not considered an exceedence of 50 µg m-3.

Concentrations of PM10 in Hamilton, Matamata, Ngaruawahia and Waihi were within the NES. Results suggest that it is unlikely that PM10 concentrations in Matamata would be in breach of the NES in the near future. The Ministry for the Environment’s air quality guideline for annual ambient concentrations of PM10 is 20 µg m-3. The annual average PM10 concentrations for Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata, Putaruru, Ngaruawahia and Waihi were 15, 16, 17, 18, 15, 18, 14 and 12 µg m-3 respectively.

Air quality monitoring of benzene, toluene and xylene was carried out at six monitoring sites in Hamilton. The highest average annual concentration during 2008 of 3.5 µg m-3 was measured at the Greenwood Street monitoring site and is within the 2010 guideline for benzene of 3.6 µg m-3 (annual average). Concentrations of toluene and xylene were well within acceptable levels.

Results of PAH monitoring in Hamilton indicated an annual average for benzo(a)pyrene of 0.40 ng m-3. With a 95% confidence interval of 0.20-0.60 ng m-3 this concentration is statistically indistinguishable from the guideline for benzo(a)pyrene of 0.3 ng m-3.

Air Quality Monitoring 2008 for Hamilton, Tokoroa, Taupo,Te Kuiti, Matamata, Putaruru, Ngaruawahia and Waihi [PDF, 1.7 MB]