Report: TR 2005/52R

Author: Emily Wilton, Environet Ltd

Abstract

Environment Waikato has monitored air quality in Hamilton since 1997. Contaminants monitored include suspended particles (PM₁₀) and carbon monoxide (CO) and intermittent monitoring of nitrogen dioxide (NO₂), benzene and ozone. Results show concentrations of PM₁₀ in excess of the Ministry for the Environment’s ambient air quality guideline and National Environmental Standard (NES) of 50 µgm^-3 (24-hour average) have occurred up to four times per year. Concentrations of other contaminants are within guideline values and the NES.

This inventory evaluates the contribution of different sources to air emissions in Hamilton for 2005. Contaminants evaluated include PM₁₀, CO, nitrogen oxides (NOx), sulphur oxides (SOx), volatile organic compounds (VOC) and carbon dioxide (CO₂). Sources included in the inventory were domestic heating, motor vehicles, outdoor rubbish burning and industrial and commercial discharges.

Domestic home heating emissions were assessed based on a survey of home heating methods and fuels used in Hamilton during 2005. The survey found that gas was the most common heating method in Hamilton and was used by 64 per cent of households to heat their main living area. Electricity use was also common, with 36 per cent of household using this method in their main living area. Of those households using gas, about half used unflued gas heating.

The main source of daily wintertime PM₁₀ emissions across the whole of Hamilton was found to be domestic home heating, which accounted for around 72 per cent of emissions. The remaining 28 per cent was distributed between motor vehicles (11 per cent), outdoor burning (13 per cent) and industrial emissions (4 per cent). Motor vehicles also accounted for 68 per cent and 76 per cent of the CO and CO₂ and 91 per cent of the NOx emissions.

Significant seasonal variations in emissions were found, with motor vehicles and outdoor burning contributing 41 per cent and 38 per cent of the daily summer PM₁₀ emissions respectively. Domestic heating contributed 47 per cent of the annual PM₁₀ emissions, with motor vehicles and outdoor burning each contributing 22-23 per cent of emissions.

In the central (CBD) area, motor vehicles contributed as much PM₁₀ as domestic heating (both around 45 per cent), whereas in the Melville (hospital) area, industry was the second most dominant source contributing 26 per cent of the daily winter PM₁₀.

Note: This report was originally published in June 2005. This new edition corrects a minor data error which appeared in Table 3.2 of the original report. While addressing this error, the opportunity was taken to make some minor changes to data, based on updated methodology that has been developed since the original report was published - but makes no difference to the interpretation or conclusions.

Hamilton Emission Inventory 2005 [PDF, 454 KB]