The current lockdown measures in place to control the spread of the Covid-19 pandemic has resulted in a dramatic drop in road traffic within Scotland’s cities. It is well established that road traffic is the main source of oxides of nitrogen (NOx) within these cities and so it is safe to assume that nitrogen dioxide (NO2) concentrations will have decreased during the lockdown. The current situation provides an opportunity to investigate what improved air quality within Scotland’s cities could look like in the future.
In addition to NO2, particulate matter (PM10 and PM2.5) is of great interest. Analysis of PM is more difficult due to the secondary nature where particles are formed through chemical reactions of other pollutants; and transboundary nature, where PM forms and travels over long distances. As a result, both the weather e.g. where the air mass originated from, and emissions from elsewhere (e.g. Europe) can have a much greater impact on local concentrations.
The following summary analysis provides an indication of the extent of the reduction in NO2 and PM10 concentrations at a the following sites:
It is important to note that this type of analysis doesn’t take into account the important influence of weather on ambient pollutant concentrations. More detailed analysis for NOx can be found here.
Note that the 2020 data are provisional at the time of carrying out this analysis and will be subject to further quality control.
Figures 1 to 7 show NO2 concentrations measured between 23 March and 29 April in the years 2015 to 2020 at the seven sites. The data indicate that NO2 concentrations have dropped by between 45% and 82% from previous years.
The Time Variation plot shows pollurant concentrations by day of the week, mean hour of day and a combined hour of day – day of week plot and a monthly plot. Also shown on the plots is the 95 % confidence interval in the mean, which can be helpful when trying to determine whether there is a significant difference between the comparison years. In this case, a clear difference in NO2 concentrations can be seen during 2020 when compared to the previous five years.
Figure 1 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Aberdeen Union Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Aberdeen Union Street | 52 | 45 | 44 | 45 | 37 | 20 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -62% | -56% | -55% | -56% | -46% | - |
Figure 2 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Dundee Lochee Road (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Dundee Lochee Road | 42 | 39 | 41 | 43 | 34 | 17 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -60% | -56% | -59% | -60% | -50% | - |
Figure 3 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Edinburgh St John’s Road (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Edinburgh St John’s Road | 74 | 58 | 57 | 36 | 36 | 13 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -82% | -78% | -77% | -64% | -64% | - |
Figure 4 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Fife Dunfermline (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Fife Dunfermline | 24 | 21 | 21 | 21 | 19 | 9 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -62% | -57% | -57% | -57% | -53% | - |
Figure 5 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Glasgow Kerbside (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Glasgow Kerbside (Hope St) | 59 | 69 | 58 | 71 | 66 | 23 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -61% | -67% | -60% | -68% | -65% | - |
Figure 6 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Inverness (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Inverness | NaN | 24 | 19 | 15 | 15 | 6 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -NaN% | -75% | -68% | -60% | -60% | - |
Figure 7 - NO2 concentrations between 23 March and 29 April in the years 2015 to 2020 at Perth Atholl Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Perth Atholl Street | 57 | 37 | 41 | 43 | 35 | 15 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -74% | -59% | -63% | -65% | -57% | - |
Figures 8 to 13 show PM10 measured between 23 March and 29 April in the years 2015 and 2020 at six sites accross Scotland. The potential reduction in concentrations is less clear, but it can be seen that average PM10 concentrations during the lockdown have decreased by between 8% and 48% compared to previous years. Note that these figures should be treatred with caution due to the reasons outlined in the introduction. This is especially the case for 2019 where a PM episode was experienced, caused by fires in Europe and Russia at the end of April 2019.
Figure 8 - PM10 concentrations between 23 March and 29 April in the years 2015 to 2020 at Aberdeen Union Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Aberdeen Union Street | 17 | 13 | 14 | 17 | 13 | 9 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -47% | -31% | -36% | -47% | -31% | - |
Figure 9 - PM10 concentrations between 23 March and 29 April in the years 2015 to 2020 at Dundee Lochee Road (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Dundee Lochee Road | 23 | 18 | 19 | 14 | 21 | 12 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -48% | -33% | -37% | -14% | -43% | - |
Figure 10 - PM10 concentrations between 23 March and 29 April in the years 2017 to 2020 at Edinburgh St John’s Road (µg m-3)
2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|
Edinburgh St John’s Road | 13 | 14 | 22 | 12 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -8% | -14% | -45% | - |
Figure 11 - PM10 concentrations between 23 March and 29 April in the years 2015 to 2020 at Fife Dunfermline (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Fife Dunfermline | 16 | 13 | 10 | 12 | 21 | 11 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -31% | -15% | –10% | -8% | -48% | - |
Figure 12 - PM10 concentrations between 23 March and 29 April in the years 2015 to 2020 at Glasgow High Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Glasgow Kerbside (Hope St) | 17 | 13 | 14 | 15 | 17 | 12 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -29% | -8% | -14% | -20% | -29% | - |
Figure 13 - PM10 concentrations between 23 March and 29 April in the years 2015 to 2020 at Perth Atholl Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Perth Atholl Street | 23 | 19 | 22 | 17 | 22 | 14 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -39% | -26% | -36% | -18% | -36% | - |
Figures 14 to 19 show PM2.5 measured between 23 March and 29 April in the years 2015 and 2020 at six sites accross Scotland. The potential reduction in concentrations is not clear - it can be seen that average PM2.5 concentrations during the lockdown have decreased by between 0% and 56% compared to previous years (excluding 2019), however, there is no clear pattern accross the sites. Note again that these figures should be treated with caution due to the reasons outlined in the introduction. Again, this is especially the case for 2019 where a PM episode was experienced; caused by fires in Europe and Russia at the end of April 2019.
Figure 14 - PM2.5 concentrations between 23 March and 29 April in the years 2015 to 2020 at Aberdeen Union Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Aberdeen Union Street | 9 | 7 | 7 | 7 | 7 | 4 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -56% | -43% | -43% | -43% | -43% | - |
Figure 15 - PM2.5 concentrations between 23 March and 29 April in the years 2018 to 2020 at Dundee Lochee Road (µg m-3)
2018 | 2019 | 2020 | |
---|---|---|---|
Dundee Lochee Road | 6 | 11 | 6 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | 0% | -45% | - |
Figure 16 - PM2.5 concentrations between 23 March and 29 April in the years 2017 to 2020 at Edinburgh St John’s Road (µg m-3)
2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|
Edinburgh St John’s Road | 6 | 6 | 12 | 6 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | 0% | 0% | -50% | - |
Figure 17 - PM2.5 concentrations between 23 March and 29 April in the years 2017 to 2020 at Fife Dunfermline (µg m-3)
2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|
Fife Dunfermline | 5 | 6 | 12 | 6 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | +20% | 0% | -50% | - |
Figure 18 - PM2.5 concentrations between 23 March and 29 April in the years 2015 to 2020 at Glasgow High Street (µg m-3)
2015 | 2016 | 2017 | 2018 | 2019 | 2020 | |
---|---|---|---|---|---|---|
Glasgow Kerbside (Hope St) | 8 | 7 | 7 | 7 | 11 | 6 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | -25% | -14% | -14% | -14% | -45% | - |
Figure 19 - PM2.5 concentrations between 23 March and 29 April in the years 2018 to 2020 at Perth Atholl Street (µg m-3)
2018 | 2019 | 2020 | |
---|---|---|---|
Perth Atholl Street | 5 | 12 | 7 |
% drop in 2020 concentrations relative to comparison year (23 March - 29 April) | +40% | -42% | - |