No breathing easy in Tokoroa just yet
A Waikato Regional Council official has told South Waikato District Councillors that he found no evidence to suggest air quality in Tokoroa is getting better or worse.
The message came from WRC’s Environmental chemist Jonathan Caldwell who presented his findings using Pearson’s Correlation Method and the Seasonal Mann- Kendall Analysis of air quality in the South Waikato, notably Tokoroa.
During last week’s Corporate and Environment Committee meeting Mr Caldwell said monitoring data shows 15 exceedances in Tokoroa this year, on a par with previous years.
‘‘ If we average the PM10 concentrations over a year, we are looking at 18 micrograms per cubic metre, which is quite consistent with previous years.’’
There is a guideline of annual measures of 20 micrograms.
‘‘So we are tracking below the annual average guideline. But it is still up there. The maximum readings do seem to have come down a little bit in the last couple of years that may indicate to you perhaps that things might be improving.’’
Mr Caldwell used the statistical data to determine whether there are trends developing.
‘‘ Pearson’s Correlation Method . . . is where we looked at some key summary statistics, changes in the annual averages per year. From statistical analysis using Pearson’s Correlation there is no evidence that the air quality is getting better or worse.’’
The Seasonal Mann-Kendall test was subsequently used and came to the same conclusion.
Councillor Herman van Rooijen questioned whether the test considered weather conditions.
‘‘One thing we have looked at [is] that nine per cent of the time when there has been exceedances we’ve had cool temperatures below 12 degrees [day time temperatures] and also wind speeds below two metres per second,’’ Mr Caldwell said.
The Emissions Inventory System also revealed 93 per cent of PM10 emissions in 2012 were a result of domestic heating appliances.
‘‘The monitoring data shows what’s actually happening with PM10 in the air, so we are monitoring the concentrations of PM10. All the Emission Inventory shows is how many kilograms of PM10 are emitted from wood burners, how much is likely to be from industry and how much is likely to be emitted from vehicles.’’
Air dispersion and how PM10 is dispersed in the air will have an affect on how the air quality is, Mr Caldwell said.
‘‘ So one kilogram of PM10 emitted from a wood burner will be dispersed quite differently from one kilogram dispersed from the industry where you get a much better dispersion.’’