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)
Nitrogen dioxide across regional airsheds [A Indicator 4.6]
Also contributing to the formation of ozone, nitrogen dioxide irritates the throat and lungs in humans, and can in some circumstances lead to severe illness and even death (Table 4). Although ambient air monitoring data are reported in terms of nitrogen dioxide, emissions are generally expressed as oxides of nitrogen (NOx). Although some 5 to 10% of total nitrogen oxides emitted directly by combustion processes is nitrogen dioxide, most is made in a reaction between nitric oxide and ambient ozone. According to the Air NEPM, acceptable air quality is maintained when ambient nitrogen dioxide concentrations averaged over one hour are no more than 0.12 ppm for no more than one day per year.
The National Pollutant Inventory (NPI 1998, 2001) will soon be able to provide emissions information for Australia for nitrogen oxides. In the interim, it is useful to draw on the 1998 National Greenhouse Gas Inventory (AGO 2000) (for updated information see http://www.greenhouse.gov.au/inventory/index.html ). Estimates of emissions of NOx since 1990, sector by sector (Figure 150), using a technique recommended by the Intergovernmental Panel on Climate Change, show that the total from all sources for 1998 is given as 2595 kt, up from 2245 kt in 1990.
From a minimum in about 1992 to 1993, emissions of NOx from 'Agriculture' and 'All Energy' have been increasing (Figure 150).
Figure 150: Emissions of nitrogen oxides by sector and year for Australia.
Estimates for 'Industrial Processes' and 'Waste' were not estimated; estimates for 'Solvents & Others' were not applicable.
Source: AGO (2000)
Figure 150: Emissions of nitrogen oxides by sector and year for Australia.
Estimates for 'Industrial Processes' and 'Waste' were not estimated; estimates for 'Solvents & Others' were not applicable.
Source: AGO (2000)
Three examples of inventories of emissions of nitrogen oxides in different regions are shown in Table 32. (The present value for the Latrobe Valley is likely to be more than twice the value reported in Table 32, as is the case for emissions of sulfur dioxide (see Table 30). At the time of writing, the NPI (2001) does not include important sources Loy Yang A, nor Yallourn, power stations.) In an industrial valley such as the Latrobe, industry is the dominant emitter, whereas in towns such as Launceston, motor vehicles are the largest source group.
| Location | NOx emission (kt/y) | Mobile A (%) | Industry (%) | Area-based (%) |
|---|---|---|---|---|
| Latrobe Valley | 52 (1984) | 3 | 97 | <1 |
| Port Pirie | 0.4 (1994) | 65 | 33 | 2 |
| Launceston | 0.6 (1994) | 72 | 8 | 20 |
A For example motor vehicles.
Source: from NEPC (1998).
Available monitoring data for nitrogen dioxide in regional Australia show that the maximum values are low by comparison with the Air NEPM. There have been no reported exceedences of the Standard since 1984 (Figure 151).
Figure 151: Maximum one-hour concentrations of nitrogen dioxide in regional centres of Australia.
Source: data from EPAs and EPA (1990)
An illustrative result for regional Australia for ambient nitrogen dioxide concentrations (Dampier, WA, Figure 152) shows that peak hourly average concentrations were low throughout 1999.
Figure 152: Measured one-hour average nitrogen dioxide concentrations during 1999 in Dampier (WA).
The Air NEPM Standard is 0.125 ppm.
Source: Department of Environmental Protection, WA
Implications
By comparison with the one-hour Air NEPM Standard, nitrogen dioxide is not a pollutant of concern in rural and regional Australia except possibly in certain instances of interregional transport for which there are presently no monitoring data.
The Air NEPM annual Standard is certain to be met everywhere in rural and regional areas.
Interregional transport and transformation of nitrogen dioxide
Just as for regional ozone concentrations (see Ozone across regional airsheds), nitrogen dioxide levels can be high downwind of major urban centres. The case that has received a lot of attention (EPAN 1996) is transport from the Sydney basin to the Illawarra and further south. Figure 153, an example from the Metropolitan Air Quality Study, shows the photochemical transformation of Sydney emissions during a summer afternoon as they are carried in the wind to the south-southwest of Sydney. Ozone levels increased as the morning peak in emissions moved further from Sydney; nitrogen dioxide levels increased behind the ozone peak.
Figure 153: Modelled ozone and nitrogen dioxide concentrations across regional Wollongong, Sydney and NSW Central Coast during the afternoon of 9 February 1994 (units: ppb; 1000 ppb = 1 ppm).
Source: Cope and Ischtwan (1996)