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Air quality monitoring for PM10 in the Otago region has been carried out by the Otago Regional Council since 1997. A variety of gravimetric methods have been used including both low and high-volume sampling. Concentrations of PM10 have been measured in nine urban centres.
Details of the 13 ambient air quality PM10 monitoring sites within the Otago region are shown in Table 12.1. The sites are mainly residential neighbourhood and use either high volume gravimetric sampling or the low volume mini-vol samplers.
Concentrations of PM10 are of concern in many of the urban centres where air quality monitoring has been carried out in Otago. In particular, guideline value exceedences are observed in Alexandra on around 40-65% of the days monitored during the months May to August inclusive (Table 12.2). Other areas also experience regular guideline value exceedences during the winter months. Annual average PM10 concentrations in excess of the ambient air quality guidelines are also likely for a number of areas within the Otago region. However, the limited number of samples collected each year precludes a detailed assessment of annual average concentrations in most areas. Estimates of annual average PM10 concentrations in Alexandra indicate breaches of the guideline value during both 1999 and 2000.
Table 12.2 also shows an estimate of the number of days that the guideline values may have been exceeded if monitoring had been carried out on all days. This is referred to in the table as the 'equivalent' number of exceedences.
Figure 12.1 shows 24-hour average PM10 concentrations are regularly within the alert and action air quality categories for most areas. With the exception of the Alexandra and Dunedin North monitoring sites, data represent winter monitoring only.