State of the Environment

2001

Atmosphere Theme Report

Australia State of the Environment Report 2001 (Theme Report)
Lead Author: Dr Peter Manins, Environmental Consulting and Research Unit, CSIRO Atmospheric Research, Authors
Published by CSIRO on behalf of the Department of the Environment and Heritage, 2001
ISBN 0 643 06746 9

Regional Air Quality (continued)

Particles across regional airsheds [A Indicator 4.2]

Sulfur and nitrogen oxides emissions from isolated industrial sources, such as smelters, transform to acid aerosol as they are blown downwind. The wet and dry deposition of these aerosol particles can have significant effects on vegetation and ecosystems (Manton & Jasper 1998). However, there is as yet little information to assess this for Australia. Most of the concern is with human health. Inhalation of excessive levels of a wide variety of fine particles may cause breathing difficulties and worsen respiratory diseases, leading to premature death (Table 4). Four indicators [A Indicators 4.2, 4.3, 4.8 and 4.12] dealing with particles are discussed in this section:

No attempt is made here to estimate particle emissions across regional Australia, neither as TSP nor PM10, since the uncertainty in such estimates is very large. Airborne particles are frequently the dominant environmental concern for emissions to air from many Australian mining and mineral process operations. Environment agencies have made available few monitoring results from regional Australia for this Report, though many mining operations are required to monitor ambient concentrations of particles as part of their performance and licence conditions. Some information is available in companies' annual environmental reports. With the mandating of the Air NEPM in 1998, there is a move away from TSP to PM10 monitoring.

Australian 24-hour average PM10 levels peak at around 90 to 110 gm/3 , especially in autumn and winter in regional urban areas. However, maximum PM10 concentrations vary greatly (Figure 133); high levels are strongly related to the weather. In warmer regions, dry conditions are important, leading to bushfires, burning off and dust. In cooler regions, domestic wood fires can produce high levels of particles. An extreme example is Launceston in winter. Another for which no PM10 data are available is Armidale (NSW).

The 24 hour average PM10 concentration exceeded 50 g/m3 in several regional centres (Figure 134). The Air NEPM allows five exceedences a year. Most regions comply, but Launceston is an obvious exception. Over the past three years, there have been around 40 exceedences per year with a declining trend. The decrease may be as a result of weather conditions but is more likely to be due to increased awareness of the harm smoke can do to health, a better understanding of the way to operate heaters to minimise pollution and an increase in the price of wood such as in the ACT.

Figure 133: Maximum daily average PM10 concentrations measured at regional centres in Australia.
Measurements are either every day or every sixth day. Several sites monitor only on a one-day-in-six cycle.

Figure 133: Maximum daily average PM10 concentrations measured at regional centres in Australia

Source: data from EPAs

Figure 134: Number of occasions daily average PM10 was above current Air NEPM level of 50 g/m3 in regional centres of Australia.
Negative values represent zero exceedences. Some sites have monitored only on a one-day-in- six cycle.

Figure 134: Number of occasions daily average PM10 was above current Air NEPM level

Source: data from EPAs

Figure 135: Daily PM10 concentrations measured in Dampier, WA, throughout 1999.

Figure 135: Daily PM10 concentrations measured in Dampier, WA, throughout 1999.

Source: Department of Environmental Protection, WA

In Bendigo (Vic.), Bendigo Mining reports (Bendigo 1999) that their near-site monitoring in 1999 showed a maximum 24 hour average PM10 of 49 g/m3 with 99% of measurements below 40 g/m3.

In the Pilbara (Karratha, Dampier and Port Hedland), WA, locally generated dust is the only significant air quality issue. BHP (1999) reports that at the BHP hot briquetted iron plant at Booarie (Port Hedland), PM10 levels exceeded the Air NEPM 14 times throughout 1998 and 17 times in 1999. The levels were influenced by strong winds and were attributed to natural sources. Measurements of particles in Dampier are generally well below the Air NEPM standard (Figure 135). One exceedence on 1 February 1999 is attributed to nearby ship loading activities.

Implications

There are three distinct issues related to high PM10 that require consideration:

  1. Woodsmoke - sometimes an issue in the major cities, woodsmoke is a problem in some regional centres such as Launceston and Armidale, both of which have well-documented concerns (see Woodsmoke in Launceston). It is likely to be a problem in all valley regions that rely on wood for domestic heating. Mitigation actions have been under way for several years, including development of standards for the emissions performance of wood heaters, new wood heater designs and campaigns to heighten awareness of correct fuel selection and heater operation, and potential new actions such as banning wood heaters in some regions. If improvement in winter air quality is to rely solely on the uptake of heaters that meet emissions standards, it will probably take a long time for acceptable air quality in compliance with the Air NEPM to be achieved.
  2. Mining industry particle emissions - industry's environmental awareness has increased greatly since the 1990s and their willingness to undertake substantial measures to reduce dust emissions, including surveillance monitoring of the effect of their operations in their communities, appears to be working. Dust emissions are generally being well controlled (see Deposition of dust across regional airsheds). The evidence to support this claim is held by the regulators, who should report on the large quantities of licensing data that they receive from industry each year.
  3. Smoke from bushfires or fuel-reduction burns on the outskirts - smoke may drift into major urban airsheds, and can reduce visibility for several days. Some of the major air pollution episodes recorded in capital city airsheds have occurred when smoke from regional controlled burning was trapped by air recirculation (SoE 1996, p. 5-24). See also the discussion in this report on ozone, and Urban air quality. The Air NEPM restricts the number of times that fire-control authorities can burn-off excess vegetation in situations where the exercise might lead to excessive urban PM10 levels. It is not yet clear whether such restrictions affect safe management of the bush.

Further, as suggested by investigations of woodsmoke in Launceston, it may be necessary to add determinations of particles finer than PM10 (perhaps PM2.5 or even PM1) to the Air NEPM for adequate protection of human health. This is recognised by the NEPC, which has just approved a review of the particle standard and consideration of the need for a national PM2.5 standard.

Woodsmoke in Launceston

Launceston (pop. 70 000) in the Tamar Valley, northern Tasmania, is a city of winter woodsmoke. Winter fogs create extended periods of poor visibility and contribute to obvious woodsmoke odour.

From 1991, the Launceston Air Pollution Study (1996) undertook a four-year investigation of smoke in the region, including detailed monitoring at up to five sites as well as an epidemiological study. Since then, the Tasmanian government has undertaken daily monitoring from the beginning of May through to the end of September, and on a six-day cycle for the remainder of the year (Carnovale 1997). About 40 exceedences of the Air NEPM standard for PM10 occur per year (Figure 134), with annual average concentrations between 1997 and 1999 between 22 and 24 g/m3 (see Figure 136). Reanalysis of the earlier data by Department of Primary Industries, Water and Environment indicates that the Air NEPM standard for PM10 was exceeded on an estimated 60 to 70 days per year.

A pilot study of the chemical and physical properties of fine particles in Launceston (Keywood et al. 2000) confirmed that woodsmoke makes a significant contribution to winter particles and that these woodsmoke particles are below 1 conclusion is that it may be difficult to interpret relationships between PM10 and health outcomes in a centre such as Launceston: there is a need to determine fine particles in smaller sizes such as PM2.5 or PM1.

Considerable effort will be required to reduce winter particle levels to acceptable values. Indeed DPIWE estimates that if the Air NEPM is to be attained in Launceston by 2008, PM10 emissions will have to be more than halved (DPIWE 2000).

Figure 136: 24-hour average PM10 measurements every six days at Ti-Tree Bend, Launceston, Tas.
Winter maxima as a result of use of wood heaters dominate.

Figure 136: 24-hour average PM10 measurements every six days at Ti-Tree Bend, Launceston, Tasmania

Source: Tasmania DPIWE