Report: TR 2007/13

Author: Jeff Smith (Environment Waikato), Emily Wilton (Environet Ltd.)

Abstract

Air quality monitoring and other air quality investigations are required to better characterise the extent of NES compliance within the region. Air quality monitoring in the Waikato region has been carried out in Hamilton, Tokoroa, Taupo, Te Kuiti, Matamata and Putaruru. Concentrations of PM₁₀ in excess of National Environment Standards (NES) have been observed in Hamilton, Tokoroa, Taupo and Te Kuiti. Emission inventory studies, which estimate the quantity of PM₁₀ and other contaminants discharged into air and the relative contribution of different sources, have been carried out in these areas.

This report outlines the results of an air emission inventory carried out in the areas of Matamata, Putaruru and Waihi. Contaminants included were: particles (PM₁₀ and PM_2.5), carbon monoxide, nitrogen oxides, sulphur oxides, volatile organic compounds and carbon dioxide. This report primarily focuses on emissions of particles (PM₁₀), as the only contaminant in breach of the NES in the Waikato Region. Sources included in the inventory were: domestic heating, motor vehicles, industrial and commercial activities, and outdoor rubbish burning.

A survey of household heating methods and the frequency of outdoor rubbish burning was carried out for each of the areas. Results showed that wood burners were used by 49 per cent of households in Putaruru and were the main heating method in the town. Electricity was the main heating method used in Matamata, with 53 per cent of households using this method of heating. Woodburners (39 per cent) and gas appliances (21 per cent) were the next most common methods of heating Matamata. In Waihi, woodburners (42 per cent) and electrical appliances (41 per cent) were the most common methods of heating. In all towns, many households used more than one method to heat the main living area of their home.

The main source of PM₁₀ emissions in all three areas during the winter was domestic home heating, which accounted for 92, 58 and 59 per cent of total emissions in Matamata, Putaruru and Waihi respectively. PM₁₀ emissions of 229, 354 and 346 kilograms per day in winter were estimated for each town respectively.

Industry contributes 39 per cent of winter PM₁₀ emissions in Putaruru, and the main industrial sources are CHH timber plant and Rapid Mineral’s lime processing operation. The industrial contribution to contaminant concentrations in Putaruru air is likely to be much less than the contribution to total emissions because industrial discharge is via high stacks that promote more effective dispersion of contaminants.

In Waihi, there is considerable uncertainty about fugitive emissions from the Martha Mine pit, although the best estimate is that 37 per cent of winter emissions are from industry. Waihi’s PM₁₀ emissions in summer may be as high as 806 kilograms per day which is around twice those in winter. However, the summer emissions are dominated by industrial discharges and the uncertainty makes it very difficult to accurately interpret the results. When discontinuous compliance monitoring data are considered in light of the best estimates of emissions, continuous monitoring of PM₁₀ is recommended at Waihi.

While survey monitoring has only recently commenced in Putaruru, PM₁₀ concentrations in Matamata have been relatively low since monitoring began in June 2005. There has been a decrease in PM₁₀ emissions at Matamata since 2001, so cessation of PM₁₀ monitoring in the town would be justified if similarly low concentrations are observed in winter 2007.

Air Emission Inventory - Matamata, Putaruru and Waihi 2006 [PDF, 733 KB]