Report: TR 2008/02

Author: Emily Wilton and Melanie Baynes, Environet Ltd

Abstract

Air quality monitoring in Tokoroa and Te Kuiti has shown that concentrations of PM₁₀ breach the National Environmental Standard (NES) for air quality regularly during winter months. The NES is set at 50 µg m^-3 (24-hour average), which can be exceeded only once per year. The Waikato Regional Plan sets a more stringent target for PM₁₀ of 33 µg m^-3 (24-hour average).

The highest measured PM₁₀ concentration for Tokoroa is 75 µg m^-3, which was measured during 2001. Recent measurements have recorded higher values but significant concerns exist about the accuracy of the monitoring equipment during these times (Smith, 2006). An evaluation of recent data estimates a higher maximum PM₁₀ concentration for Tokoroa is likely but indicates that an assumed maximum of around 75 µg m^-3 is reasonable for air quality management purposes (Kim, 2007). For Te Kuiti, the highest measured PM₁₀ level is 69 µg m^-3 and was measured in 2006.

Previous emission inventory assessments for Tokoroa and Te Kuiti suggest that the main source of PM₁₀ during winter months was solid fuel burning used for domestic home heating. This report outlines the results of an air emissions inventory for Tokoroa and Te Kuiti for 2007.

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 it is the only contaminant in breach of the NES in Tokoroa and Te Kuiti.

Domestic heating, motor vehicles, industrial and commercial activities and outdoor burning are the sources of PM₁₀ which were included in the emissions inventory.

A domestic home heating survey was carried out for Tokoroa and Te Kuiti to determine the proportions of households using different heating methods and fuels. Tokoroa results show that wood burners are the most common method of heating in the main living area with 45 per cent of households using them. Thirty three percent of householders use electricity as the main form of heating and 23 per cent of householders use gas to heat their main living area. Many households used more than one method to heat the main living area of their home.

Te Kuiti results show that wood burners are the most common method of heating in the main living area with 45 per cent of households using them. Forty two percent of householders use electricity to as their main form of heating and 20 per cent of householders use gas to heat their main living area. As with Tokoroa many households in Te Kuiti used more than one method to heat the main living area of their home.

The main source of PM₁₀ emissions for Tokoroa was domestic home heating, which accounted for 86 per cent of total emissions. Other sources in Tokoroa included motor vehicles (seven percent) industry (one percent) and outdoor burning (six percent). In Te Kuiti the main source was domestic heating (67 per cent). The industry contribution was higher than at Tokoroa, at 20 per cent, and motor vehicles and outdoor burning contributed seven percent and five percent respectively.

The industrial contribution to measured PM₁₀ concentrations may be less because of the additional dispersion associated with the higher discharge heights of most industrial chimneys and the locations of industry on the outskirts of the Te Kuiti township.

Air Emission Inventory - Tokoroa and Te Kuiti 2007 [PDF, 1.2 MB]