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Key findings - Sulphur dioxide

Current situation

In 2008, the only site to exceed (but not breach) the 1-hour national standard for sulphur dioxide was Christchurch (Woolston).

All other sites in New Zealand monitoring sulphur dioxide did not exceed the 1-hour standard. The 24-hour national guideline was met by all sites monitored in New Zealand, however, the Tauranga and Christchurch (Woolston) sites did not meet the 24-hour WHO guideline.

The Christchurch (Woolston), Auckland and Tauranga sites, the results of which are shown in figures 7, 8 and 9, are located close to industry. Industry locations are likely to be affected by elevated levels of sulphur dioxide. The Auckland site is also located close to major roads. The Christchurch (St Albans) monitoring site is located in a residential area.

Figure 7: Maximum sulphur dioxide levels 1-hour average, 1988–2008

Figure 7: Maximum sulphur dioxide levels 1-hour average, 1988–2008

Source: Auckland Regional Council,9 Environment Bay of Plenty,11 Environment Canterbury10

Year Auckland (Penrose)
(µg/m3)
Tauranga (Mt Maunganui)
(µg/m3)
Christchurch (St Albans)
(µg/m3)
Christchurch (Woolston)
(µg/m3)
1988     239  
1999     124  
1990     193  
1991     319  
1992     95  
1993     80  
1994     120  
1995     85  
1996     124  
1997     106  
1998     34  
1999     67  
2000     82  
2001 164.7   65  
2002 48.0   52  
2003 47.8   54  
2004 40.0   46  
2005 54.2 192.5 37 570
2006 35.2 674.3 63 472
2007 43.2 303.2 28 439
2008 31.1 244.0 53 441

Figure 8: Maximum sulphur dioxide levels 24-hour average, 1988–2008

Figure 8: Maximum sulphur dioxide levels 24-hour average, 1988–2008

Source: Auckland Regional Council,9 Environment Bay of Plenty,11Environment Canterbury10

Year Auckland (Penrose)
(µg/m3)
Tauranga (Mt Maunganui)
(µg/m3)
Christchurch (St Albans)
(µg/m3)
Christchurch (Woolston)
(µg/m3)
1988     59  
1999     36  
1990     73  
1991     81  
1992     41  
1993     18  
1994     39  
1995     34  
1996     37  
1997     34  
1998     9  
1999     19  
2000     20  
2001 69.3   22  
2002 12.8   23  
2003 16.3   17  
2004 13.9   13  
2005 20.6 107.2 14 121
2006 15.8 192.1 18 83
2007 11.9 77.8 14 64
2008 11.8 68.7 10 102

Figure 9: Annual sulphur dioxide levels, 1988–2008

Figure 9: Annual sulphur dioxide levels, 1988–2008

Source: Auckland Regional Council,9 Environment Bay of Plenty,11Environment Canterbury10

Notes:
(1) Annual averages are not presented for some sites in some years due to data limitations.
(2) The methodology used at the Auckland site changed in 2000. The trend of the annual average at this site remains comparable.

Year Auckland (Penrose)
(µg/m3)
Tauranga (Mt Maunganui)
(µg/m3)
Christchurch (St Albans)
(µg/m3)
Christchurch (Woolston)
(µg/m3)
1988 3.2   -  
1999 2.5   5  
1990 2.1   14  
1991 2.2   -  
1992 4.8   10  
1993 4.5   -  
1994 4.3   5  
1995 3.5   -  
1996 6.8   7  
1997 9.5   7  
1998 13.3   2  
1999 15.1   4  
2000 12.1   4  
2001 7.7   5  
2002 2.2   5  
2003 3.9   5  
2004 5.1   3  
2005 6.5 13.4 3 -
2006 3.5 28.5 4 11
2007 3.1 19.1 3 9
2008 2.9 - 3 8

Trend

Recent trend

Sulphur dioxide was reported on in Environment New Zealand 2007. Since then, results for the 1-hour and 24-hour maximums and annual averages for the Auckland and Christchurch (St Albans) sites have been relatively constant while results for the Tauranga and Christchurch (Woolston) sites have fluctuated (see the new data presented in figures 7–9).

In 2006, there were 24 exceedances and 11 breaches of the 1-hour national standard for sulphur dioxide. Twenty-one of the exceedances and all 11 of the breaches occurred at the Tauranga site. The remaining three exceedances occurred at the Christchurch (Woolston) site. In 2006, the 24-hour national guideline was not met by the Tauranga site on six occasions.

In 2007, there were two exceedances of the 1-hour national standard for sulphur dioxide. Both these exceedances occurred at the Christchurch (Woolston) site.

In recent years the Tauranga and Christchurch (Woolston) sites have not met the 24-hour WHO guideline.

All other monitoring sites in New Zealand have not exceeded the 1-hour national standard or national and WHO guidelines for sulphur dioxide in recent years.

Long-term trend

Annual levels of sulphur dioxide at the Christchurch (St Albans) site show a general decreasing (improving) trend. This reflects the continuing reductions in the amount of sulphur in diesel fuel and coal use over this period.

The annual levels at the Auckland site have fluctuated over this period. The increasing levels at this site in the mid- to late-1990s coincided with an increase in the registration of new and used diesel vehicles and levels subsequently decreased with the improvement in fuel quality.

Text box 4: Global air quality guidelines for sulphur dioxide

In October 2006, the World Health Organization (WHO) published its first global air quality guidelines. WHO’s new guidelines reduced the 24-hour average sulphur dioxide guideline from 120 micrograms per cubic metre to 20 micrograms per cubic metre. New Zealand’s ambient guideline (2002) is set at 120 micrograms per cubic metre. Most of New Zealand is likely to meet the new WHO guideline. However, some areas, particularly those downwind of refineries, coal-burning industrial plants, and ports, may exceed the WHO guideline over a 24-hour period.