NSW annual air quality statement 2020: gases

Carbon monoxide (CO)

The national standard for carbon monoxide is:

• 8-hour average – 9 parts per million (9 ppm).

Eight-hour carbon monoxide averages

There were no days over the 8-hour CO standard in 2020. The maximum 8-hourly CO average was 3.3 ppm, recorded at Wollongong in the Illawarra on 8 January 2020. However, the temporary Katoomba air quality monitoring station recorded a higher maximum 8-hour average CO value of 7.0 ppm, on 5 January 2020, during the bushfire emergency period.

The Bradfield Highway roadside monitoring station recorded a maximum 8-hourly CO average of 2.6 ppm on 8 January 2020.

Nitrogen dioxide (NO₂)

The national standards for nitrogen dioxide are:

• one-hour average – 12 parts per hundred million (12 pphm)
• annual average – 3 parts per hundred million (3 pphm).

One-hour nitrogen dioxide averages

There were no days over the one-hour NO₂ standard in 2020. The maximum hourly average NO2 level was 9.9 pphm, recorded at Goulburn in the Southern Tablelands on 5 January 2020, during the extreme 2019–20 bushfire period.

The Bradfield Highway roadside monitoring station (north of the Sydney Harbour Bridge, adjacent to one of the State’s busiest roads) recorded a maximum hourly NO₂ level of 6.8 pphm on 2 March 2020 at 3pm.

Annual nitrogen dioxide averages

Annual average NO₂ levels remained well below the national standard in 2020. The maximum annual NO₂ average at the non-roadside monitoring stations was 1.3 pphm, recorded at Cook and Phillip in Sydney East.

At the Bradfield Highway roadside monitoring station, the annual NO₂ average was 2.2 pphm.

Ozone (O₃)

The national standards for ozone are:

• one-hour average – 10 parts per hundred million (10 pphm)
• 4-hour average – 8 parts per hundred million (8 pphm).

One-hour and 4-hour ozone averages

There were 6 days in 2020 when ozone levels exceeded the national standards at one or more stations in NSW, meeting the national standards on 98% of days. The exceedance days all occurred during the extreme 2019–20 bushfire period. For comparison, there were 33 days in 2019 when ozone levels exceeded national standards.

The maximum hourly ozone average was 11.6 pphm, recorded at Oakdale in Sydney South-west. The maximum four-hour average was 10.7 pphm, recorded at St Marys in Sydney North-west. These events occurred on 31 January 2020, during the extreme 2019–20 bushfire period.

Within the Greater Metropolitan Region (GMR, comprising Sydney, Lower Hunter, Central Coast and Illawarra regions), ozone levels were over the national standards on 4 days (meeting the standards 99% of the time). This counted as 25 fewer days than 2019 when the ozone standards were exceeded on 29 days.

Ozone levels peaked in the warmer months during January and February. Within the GMR, ozone events occurred on:

• 4 days at two or more stations in the Sydney region (compared to 28 days in 2019)
• 1 day each in the Central Coast and Illawarra regions (compared to 3 days in 2019)
• No days in the Lower Hunter region (compared to 5 days in 2019).

In NSW regional centres, ozone events occurred on:

• 4 days at Goulburn in the Southern Tablelands (compared to 4 days in 2019, from site establishment on 6 November to 31 December 2019). These events were associated with bushfire smoke transported from Warragamba, Wollemi National Park and the New South Wales South Coast.
• no days at Gunnedah in the North-west Slopes (compared to 2 days in 2019)
• no days at Coffs Harbour on the Mid-north Coast (compared to one day in 2019, from site establishment on 22 November to 31 December 2019)
• no days at Port Macquarie on the Mid-north Coast (compared to two days in 2019, from site establishment on 27 July to 31 December 2019).

The most extensive ozone events in 2020 are outlined below:

• On 31 January 2020, ozone levels above the national standards were recorded at 10 stations – 5 stations in Sydney South-west, 4 in Sydney North-west and at Goulburn in the Southern Tablelands. The maximum hourly ozone was 11.6 pphm, recorded at Oakdale in Sydney South-west. This event was due to heatwave conditions across New South Wales. A blocking high-pressure system in the Tasman Sea and low-pressure trough over central New South Wales combined to bring hot air from central Australia towards the east coast. The maximum temperature in Sydney was 40.5°C at Richmond in Sydney North-west.
• On 1 February 2020, ozone levels above the national standards were recorded at 8 stations – 2 stations each in Sydney South-west, Sydney North-west and Illawarra, 1 in Sydney East and at Goulburn in the Southern Tablelands. The maximum hourly ozone was 10.8 pphm at Campbelltown West in Sydney-South-west. This event also was due to the heatwave event that impacted New South Wales on 31 January 2020. Stable atmospheric conditions combined with afternoon sea-breezes, resulting in elevated ozone levels across Sydney. The maximum temperature in Sydney was 46.4°C at St Marys in Sydney North-west.

Days above the 1-hour and 4-hour ozone standards – 2020

Note: Values in brackets are the maximum ozone levels at each station on the day. pphm = parts per hundred million in volume. Ozone data from the new air quality monitoring stations are available from 4 July 2020 at Penrith, 14 August 2020 at Merriwa and 26 November 2020 at Morisset. “-“ indicates no exceedances recorded.

Sulfur dioxide (SO₂)

The national standards for sulfur dioxide are:

• one-hour average – 20 parts per hundred million (20 pphm)
• daily average – 8 parts per hundred million (8 pphm)
• annual average – 2 parts per hundred million (2 pphm).

One-hour sulfur dioxide averages

There were no days over the one-hour SO₂ standard in 2020. The maximum hourly SO₂ average was 13.5 pphm, recorded at Muswellbrook in the Upper Hunter on 19 May 2020.

The Bradfield Highway roadside monitoring station recorded a maximum hourly SO₂ level of 1.2 pphm on 30 August 2020.

Daily sulfur dioxide averages

There were no days over the daily SO₂ standard in 2020. The maximum daily SO₂ average was 1.5 pphm, recorded at Muswellbrook in the Upper Hunter on 30 December 2020.

The Bradfield Highway roadside monitoring station recorded a maximum daily SO₂ level of 0.3 pphm on 19 March 2020.

Annual sulfur dioxide averages

Annual average SO₂ levels remained well below the national standard in 2020. The maximum annual average was 0.22 pphm, recorded at Muswellbrook in the Upper Hunter.

At the Bradfield Highway roadside monitoring station, the annual SO₂ average was 0.08 pphm.