Air quality in Palmerston and Milton goes under the microscope

Palmerston is to become part of the Otago Regional Council’s continuous programme of air quality monitoring, after an ORC study found that parts of the town are prone to pollution from smoke and soot during winter.

ORC director of environmental information and science John Threlfall said monitoring of air particulate levels around the town had uncovered a low-lying corridor of land running from the southern part of town to the northeast corner where emissions accumulate during evenings and early mornings.

Just one exceedance is allowed in a 12-month period of the 50 micrograms per cubic metre particulate limit in the Government’s National Environmental Standard  (NES).

ORC’s spatial monitoring enables the variability of air particulates in an area to be identified so that decisions can be made about existing and future monitoring locations.

Dr Threlfall said little was known about air quality patterns in Palmerston before the study was done last winter. The town was designated as part of Air Zone 2 based on one winter’s monitoring in 2003.

The results from the latest monitoring provided information about short-term pollution trends, including some of the highest readings obtained from mobile monitoring anywhere in Otago.

Continuous monitoring would yield more information on the number of exceedances of the NES and about long-term pollution trends. Dr Threlfall said.

An inter-related study of air particulate levels based on mobile monitoring in Milton confirmed the location of ORC’s permanent monitor as being at the site of some of the worst air quality in town.

Mobile monitoring was done on six occasions during the winters of 2010 and 2011 and included evening and morning sampling. Except for some small differences between nights due to changing wind patterns, the distribution pattern of PM10  was relatively stable.

Dr Threlfall said the results were consistently highest in the south eastern part of town surrounding the monitor.

Both the Milton and Palmerston results were valuable because they offered an overall  picture of typical winter-time particulate pollution in each town, he said.