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Air Quality
~ Te kounga o te hau

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Air Monitoring & Research

Air Monitoring Reports

We monitor air pollution levels, the sources of pollutants and trends in air pollution for Hawke’s Bay.The government has identified a number of air pollutants that are considered important nationally and have set National Environmental Standards (NES) for them. Locally, the main pollutant of concern is PM10 because it is known to exceed acceptable levels in the region’s urban areas, mainly during late autumn and winter. This is mostly due to fires being used to heat homes on chilly, calm nights when smoke from the fires is prevented from dispersing by an inversion layer in the atmosphere.

The PM10 Monitoring Network

Continuous monitoring

The Hawke’s Bay Regional Council’s air quality monitoring network includes three stations with automatic beta attenuation PM10 monitors which continuously record PM10. These are located in Napier, Hastings and Awatoto. The Napier and Hastings sites have been operating for over five years, while the Awatoto monitor has been at its present location since February 2012 after being moved from Meeanee where it was used for a traffic impact monitoring project.   

The objective at these sites is to monitor ambient PM10 levels rather than focus on a particular single source. The Marewa Park and St John’s College sites reflect typical residential areas, have average traffic levels and are not dominated by any particular industrial source. The site at Waitangi Road reflects an area dominated by industrial activity. Measurements from these sites are used to monitor the State of the Environment (SOE) and to report on compliance with the new NES for air quality. 

Screening monitoring

In addition to continuous monitoring, the Council conducts fixed period monitoring (typically one year) at different locations in Hawke’s Bay using MicroVol monitoring equipment. The purpose of this type of monitoring, called screening monitoring, is to target areas in Hawke’s Bay where no monitoring data exists, to assess whether PM10 is likely to be a problem or not. Sampling occurs every 3 days and sample filters are processed the following month in a laboratory.

In past years, screening monitoring has been carried out in Havelock North, Wairoa, Greenmeadows, Waipukurau and Waipawa. The results are shown in the pie charts below. 

airmonitoring 24hravg

Trends in air quality

Amendments to the National Environmental Standards (NES) in 2011 mean that by 1 September 2016 PM10 concentrations must not exceed 50µgm-3 (24 hour average) on any more than one day per year in Napier and three days per year in Hastings and by 1 September 2020 no more than one day per year in Hastings. Since 2006, when continuous monitoring was established in both cities, the number of times PM10 concentrations have exceeded 50µgm-3 has varied in Napier between 0 to 5 occasions per year and between 10 and 28 in Hastings.   

Weather conditions during winter influence PM10 concentrations in the air. On windy days the PM10 emitted into the air will be dispersed but on cold, still days a temperature inversion can form in the atmosphere which effectively traps particulates near the earth’s surface. Variations in weather from year to year make it difficult to determine any trends in PM10 concentrations over time.

One way of removing the influence of meteorological conditions is to analyse concentrations on days with similar weather. An analysis was undertaken by Dr Emily Wilton of Environet Ltd which looked at PM10 levels only on days when high levels might be expected – on cold days with light winds – referred to as “normalised” PM10 concentrations. The results indicate that there has been no obvious decrease in levels in Napier since 2006 while it is possible that levels are trending downward in Hastings.

Emissions from domestic fires will need to decrease if we are to achieve the NES. The Council has implemented a clean heat programme to help residents reduce the amount of PM10 emitted from fires used for home heating, including offering financial assistance to convert to cleaner forms of heat.

Identifying the sources of air pollutants

Air Emission Inventories

Air emission inventories are used to identify sources of contaminants within a region and to quantify the contaminants being emitted over a period of time. Quantities are estimated using average emission rates for an activity based on the amount of material used, and, where available, actual emission data, such as from stack monitoring. Inventories undertaken on a regular basis can help to determine the effectiveness of measures undertaken by the Council to reduce emissions.

In June 2005 an Air Emission Inventory was completed for the Hawke’s Bay region. This report quantified sources of PM10 and other contaminants in the air, and was carried out for Hawke's Bay Regional Council by Environet Ltd.

The report provides details of emissions in: Napier, Hastings, Flaxmere and Havelock North; the three areas of Wairoa, Waipawa and Waipukurau jointly; and the rest of the region. It assessed PM10 sources such as domestic heating, motor vehicles, industrial and commercial activities, outdoor burning, orchard heaters, shipping and aviation.

The report’s main finding was that domestic heating (mostly from woodburners) is the largest source of PM10 in Napier and Hastings in winter, which is when concentrations of PM10 exceed the NES for air quality.

In 2010 the inventory was updated for Napier, Hastings and Havelock North.

The results from this study confirmed that domestic heating was the main source of PM10 in the cities, this time contributing 92% of average daily winter PM10 emissions in Napier and 95% in Hastings. However, the total amount of PM10 emitted from all sources was estimated to have reduced over the 5 year period between the reports. In both the 2005 and 2010 studies the amount of emissions from domestic sources was not measured directly but estimated from information provided by participants in a telephone survey.

Source Apportionment Investigations

Compared to emission inventories, source apportionment studies provide a more direct measure of the nature and sources of particles in the air through analytical techniques. It requires the collection and analysis of air samples and because of this is limited to identifying contributions to air quality at specific locations.

A GENT sampler has been located at St John’s College, Marewa Park and near the beach at Awatoto for limited periods, to enable us to identify which sources contribute to fine particulates in those areas.

The contribution of different sources to PM10 concentrations in Hastings was examined as part of a national study. PM2.5 (particles less than 2.5 microns in diameter) was also examined.

Contribution of sources to annual PM10 concentrations at Hastings


In Hastings, five sources were found to contribute to the PM10 concentrations. These were identified as domestic home heating, marine aerosol, motor vehicles, sulphate and soil. For this report, domestic heating sources also included outdoor burning of domestic waste. The main contributor to PM10 concentrations in Hastings was domestic heating, which was responsible for most of the annual concentrations and the winter concentrations in particular. This is consistent with the findings of the emission inventories.

The total background or “natural” contribution for Hastings during winter is estimated to be 13-15% of total PM10 (soil and sea spray). The background component of the PM10 needs to be accounted for when developing strategies for reducing PM10 concentrations in order to achieve the NES.

A similar type of study was conducted in Marewa, Napier. The main sources of particulates were divided into domestic heating; soil, sea spray and a combination of domestic heating and sea spray. Conclusions from this study were that domestic heating was the main source of total PM10 but that the contribution from natural sources was higher than observed in the Hastings study - as much as 23% on high pollution days.

The research at Awatoto was conducted over a very short time period (February to May 2010) and focussed on trialling a methodology for estimating sea spray and soil contributions to PM10. The instrument taking samples was located very close to the beach and at that location the amount of sea spray and soil was found to be quite high during the period of the study, comprising on average around 58% of total PM10.

Airshed Modelling

An airshed modelling study in Hawke’s Bay was carried out by NIWA for the Regional Council in 2006. An airshed is an area where air quality is likely, or known, to exceed the NES.

The model simulated the National Environment Standard breaches for a typical year in Napier and Hastings.

Hastings has higher PM10 levels than Napier. Havelock North and Flaxmere may exceed the NES but the area of exceedance is small.

Modelling showed that Wairoa is compliant with the NES, but with PM10 concentrations reaching two-thirds of the NES level. The other urban areas (for example Waipukurau, Waipawa and Otane) appear to have low PM10 concentrations.

To attain the NES, the model estimates that emissions from domestic heating should decrease for PM10 by 79% in Hastings and 55% in Napier.

The modelling study of PM10 concentrations in Napier and Hastings was updated in 2011/12 by Golder Associates, using  monitoring data up to 2010. The purpose was to provide an estimate of the spatial distribution of PM10, to quantify transport of the pollutant between and within airsheds and to update projected reductions in emissions required to meet the NES.

The main findings from this exercise were:

  • The peak modelled PM10 (24 hour average) was relatively high in Marewa (the site of monitoring) but the concentration is potentially higher in Pirimai.
  • The St John’s site in Hastings is relatively well placed to measure peak concentrations, being within a ring of peak PM10 levels around central Hastings.
  • Very little of the PM10 in Napier’s Airzone 1 originates in Hastings and vice versa. Nearly all exceedances of the NES in Napier would still occur if there were no emissions in Hastings and vice versa.
  • Dispersion within airsheds is significant. Approximately 30-40% of modelled PM10 at Marewa Park originates within the Marewa Census Area Unit (CAU) with the largest contributions from other CAUs coming from those lying to the west and south. Approximately 30-60% of modelled PM10 at St John’s College originates from the Mayfair CAU, with the largest contribution from other CAUs coming from Parkvale to the south.
  • The overall reduction in emissions, from 2010 levels, required to meet the NES is 44% in Napier and 48% in Hastings.  This includes an “unmanageable” contribution from natural sources so the estimated reduction in emissions from domestic heating is 47% and 50% for Napier and Hastings respectively.

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