The Waikato region has 20 gazetted urbain airsheds: Cambridge, Hamilton, Huntly, Matamata, Morrinsville, Ngaruawahia, Otorohanga, Paeroa, Putaruru, Taupō, Te Aroha, Te Awamutu-Kihikihi, Te Kūiti, Thames, Tokoroa, Tuakau, Turangi, Waihi, Whangamata and Whitianga. The seven airsheds identified in bold are currently monitored by Waikato Regional Council for PM10. We suspect these areas are at risk because they are susceptible to build of PM10 during periods of calm, settled weather.
PM10 data are collected daily at all sites and reported as an average level for each 24 hour period, with the exception of Taupō prior to 2006 where data were collected on a one-in-six day (prior to 2002) or one-in-three day (2002 to 2006) monitoring regime. This 24-hour period is significant in determining adverse effects on human health. We also analyse hourly average data so that we can assess variations in concentrations during the day.
Daily PM10 measurements have been collected during the following years for each location:
Waikato Regional Council currently uses three types of PM10 monitoring equipment:
GT640 (optical) monitoring method was used prior to 2001 and a Met One 1020 BAM was used from 2001 to September 2005 to measure PM10 concentrations in Tokoroa.
Monitoring results are reported in relation to the regional guideline, using the Ministry for the Environment air quality indicator reporting framework outlined in the table below. This framework is used to report on air quality for a range of contaminants relative to their respective guidelines.
Table 1 shows the percentage of times the 24 hour average PM10 levels fell into each category, and the number of times the 24 hour average PM10 levels went above the national environmental standard during the periods each site was monitored.
Table 1: Ministry for the Environment categories for air quality
|Category||Value relative to guideline||Comment|
|Good||Between 0% and 33% of the guideline||Peak measurements in this range are unlikely to affect air quality|
|Acceptable||Between 33% and 66% of the guideline||A broad category, where maximum values might be of concern in some sensitive locations but generally they are at a level which does not warrant dramatic action|
|Alert||Between 66% and 100% of the guideline||A warning level, which can lead to the guideline being exceeded if trends are not curbed|
|Action||More than 100% of the guideline||Exceeding the guideline is a cause for concern and warrants action if it occurs regularly|
The Waikato Regional Plan (Regional Ambient Air Quality Guidelines) sets the regional guideline at 50 µg/m3 for a 24 hour period. The Ministry for the Environment guidelines for particulate matter are 50 µg/m3 for a 24 hour period and 20 µg/m3 for an annual average. During 2004 the Ministry for the Environment introduced a National Environmental Standard for PM10 of 50 µg/m3 for a 24 hour period. The standard allows one breach of 50 µg/m3 per year and is effective from September 2005. In 2011 the NES was amended and as a result, all urban airsheds, except for Tokoroa, must meet the target of no more than one exceedance per year by 1 September 2016. Tokoroa is required to achieve a target of no more than three exceedances per year by 1 September 2016 and no more than one exceedance per year by 1 September 2020.
Waikato Regional Council has limited PM10 data in some areas. We need data from several years at each site to adequately determine annual and seasonal PM10 concentrations.
Equipment malfunction means there can be periods of missing data on occasions.
In Tokoroa monitoring of PM10 was carried out during 1999 from 19 February to 30 November at the South Waikato District Council Offices. The method of measurement used during the 1999 monitoring was a light scattering technique and is subject to limitations, such that it does not hold USEPA reference or equivalency status. Subsequent monitoring from 2001 to September 2005 was conducted with a MET One BAM which meets USEAP equivalency status. However, subsequent analysis suggests this method may not have been accurately recording PM10 concentrations.
Prior to 2006, in Taupō there was limited data available due to the one-in-six and subsequent one in three day monitoring regime.
Environment Waikato, 1999: Environmental Monitoring Technical Manual. Environment Waikato, Hamilton. (unpublished).
Environment Waikato, 2003: Quality Assurance Procedures Manual for ambient air quality monitoring at Environment Waikato. Environment Waikato, Hamilton. (unpublished).