Update on the Australian Air Quality after the implementation of the COVID-19 mobility restrictions

Written by Simon Welchman and Manning Young

 

Following the article published on the Clear Skies Newsletter in April 2020, this is an update on the investigation into whether the COVID-19 mobility restrictions have affected Australian Air Quality.

The graphs show diurnal profiles of nitrogen dioxide and PM2.5 at two sites in Brisbane (South Brisbane and Woolloongabba), two sites in Melbourne (Alphington and Footscray) and two sites in Sydney (Randwick and Rozelle). The graphs compare measurements for 16 March 2020 to 1 May 2020 with the same period in the previous four years (2016, 2017, 2018, 2019). The monitoring stations are managed by the Department of Environmental Sciences in QLD and by the Department of Environmental, Energy and Science in NSW.

 

Sydney

In Sydney, there have been distinct daily patterns and weekly cycles of NO2 concentrations even after the social distancing measures. On average, we observe marginally lower levels of NO2 at both sites (Randwick -17%, Rozelle -10%) in 2020 compared with earlier years.

Figure 1 – NO2 Concentrations for New South Wales for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – Randwick and Rozelle

 

Daily and weekly cycles are not so obvious for PM2.5 concentrations at the Sydney sites. On average, marginally lower levels of PM2.5 are observed at both sites (Randwick -21%, Rozelle -12%) in 2020 compared with earlier years.

Figure 2 – PM2.5 Concentrations for New South Wales for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – Randwick and Rozelle

 

Melbourne

In Melbourne, characteristic daily and weekly cycles of NO2 concentrations are also observed in 2020. On average, levels of NO2 are lower at Alphington (-29%) in 2020 compared with earlier years.

Figure 3 – NO2 Concentrations for Melbourne for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – Alphington

 

Characteristic daily and weekly cycles of PM2.5 concentrations are observed at Footscray. On average, lower levels of PM2.5 are observed at both sites (Alphington -23%, Footscray -24%) in 2020 compared with earlier years.

Figure 4 – PM2.5 Concentrations for Victoria for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – Alphington and Footscray

 

Brisbane

In Brisbane, we notice characteristic daily and weekly cycles of NO2 concentrations in 2020. On average, we observe marginally lower levels of NO2 at South Brisbane (-8%) and slightly higher levels at Woolloongabba (+5%) in 2020 compared with earlier years.

Figure 5 – NO2 Concentrations for Queensland for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – South Brisbane and Woolloongabba

 

Daily and weekly cycles of  PM2.5 concentrations are not so obvious in Brisbane in 2020. On average, marginally lower levels of PM2.5 were found at both sites (South Brisbane -2%, Woolloongabba-7%) in 2020 compared with earlier years.

Figure 6 – PM2.5 Concentrations for Queensland for the period between 16 March 2020 to 1 May 2020 compared with the same period in the previous four years (2016, 2017, 2018, 2019) – South Brisbane and Woolloongabba

 

What are the complications?

Some reasons why we don’t always see the reduction we are expecting are the following:

  • Weather conditions are an important influence on air quality. For example, strong winds will disperse air pollutants, whilst lighter winds and calm conditions lead to generally higher concentrations of traffic-related air pollutants.
  • Seasonal factors play an important role in air quality analyses. We generally see higher average levels of NO2 and PM2.5 in the cooler months due to more stable atmospheric conditions.
  • The influence of industrial activities is quite important in terms of air pollutants. In places where intensive industrial activities occur and those activities are not reduced due to COVID-19 emission levels and air pollutant concentrations may not be reduced.
  • Collecting air quality data is not easy. So, there is always potential for failures of equipment and data loss that will impact on the analysis.

 

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