Sep 24 2020
According to a new study, performed by the University of Liverpool relating to the UK’s air pollution during the first 100 days of pandemic lockdown, while nitrogen oxide (NO2) levels had reduced by half, levels of sulfur dioxide (SO2) have increased by more than 100%.
Image Credit: University of Liverpool.
Scientists from the School of Environmental Sciences at the University of Liverpool examined data from DEFRA air-quality sensors and UK Met Office stations to observe how lockdown measures had influenced the levels of SO2, NO2, ozone, and particle matter (PM2.5), and to compare it to the data collected from the past seven years.
The latest study demonstrated that during this period (that is, from March 23rd to June 13th, 2020), NO2 levels were reduced by half which could be associated with the reduction in vehicle emissions.
But more unexpectedly, the study also noted that SO2 levels, usually produced by the UK sector but in sharp decline, were more than double that of earlier years.
Impacts of Lockdown on Localized Air-Quality
The team also looked at the localized impacts of lockdown on air-quality, on seven major cities in the UK—London, Newcastle, Manchester, Birmingham, Liverpool, Belfast, and Glasgow.
This showed that NO2 levels in all the seven cities decreased on average between 37% and 41%, even though this figure was slightly higher in Glasgow where it reduced by 44%. But the team also found that northern cities experience greater increases in SO2 levels.
In the UK, lockdown came into effect on March 23rd, 2020 when Boris Johnson informed the nation that people “must” stay at home and that specific businesses should close.
This led to a considerable reduction in the usage of motor vehicles with the initial day of lockdown seeing a reduction to 69% of normal. This reached an all-time low of 23% on April 13th, 2020, before gradually rising back up to 77% of normal use 100 days post the lockdown. Moreover, the first 100 days of pandemic lockdown coincided with less humidity and higher temperature.
The results of our analysis are surprising. It is evident that the reduction in motor vehicles and human activity had a substantial impact on air quality as demonstrated by the reduction in nitrogen oxide. However, although it reduced one pollutant there has been a big increase in another pollutant.
Dr Jonny Higham, Study Lead and Lecturer in Contemporary and Dynamic Processes, University of Liverpool
Dr Higham continued, “We think these changes could be driven by an in-balance in the complex air chemistry near to the surface exacerbated by the meteorological conditions in particularly low humidity levels and changes in pollutions concentrations.”
It is important to note that the complex and relatively stable air composition in the near surface layer can be disrupted in a short period of time by the significant reduction of primary emissions from human activities. For the case of UK, getting cleaner air from a large NO2 reduction may not be as straightforward as it seems.
Dr Jonny Higham, Study Lead and Lecturer in Contemporary and Dynamic Processes, University of Liverpool
Journal Reference:
Higham, J. E., et al. (2020) UK COVID-19 lockdown: 100 days of air pollution reduction? Air Quality, Atmosphere & Health. doi.org/10.1007/s11869-020-00937-0.