ClairCity newsletter ClairCity newsletter May 2020 | Page 4

Conference update It was with a heavy heart that we had to cancel our conference in Brussels back in March. A lot of work went into the preperations for this event and many were looking forward to hearing our findings and celebrating in our successes. The team had secured a venue, confirmed speakers, arranged accomodation and travel, prepared communications materials, written presentations and promoted widely. Yet all was not lost. Out of the ashes comes our online webinar series and the hope of a belated celebration after the end of the project and after lockdown restrictions have eased. We would like to take this opportunity to thank everyone who was involved during this process, and hope you can find some solice in the upcoming webinar series! Air quality news Earlier this month the American Geophysical Union’s journal Geophysical Research Letters published two papers that take a look at the effect of lockdowns on air quality - and the results may not be what one might expect. One of the studies supports claims that levels of nitrogen dioxide and particulate matter pollution over China, Western Europe, and the United States have fallen dramatically due to lockdown measures. However, the other shows levels of surface ozone in China have increased. The first paper drew of satellite measurement and found that while results varied, most of the coronavirus epicentres they measured showed reductions. For example, NO 2 levels were down by 40% over urban areas in China, 20% over Belgium and Germany, and 19–40% in different areas of the U.S. There was no decrease in Iran however, and this is believed to be due to a less stringent lockdown. Experts have not observed reductions of such magnitude since satellite-based air quality monitoring began in the 1990s, according to Stavrakou. The second paper focused on northern China, measuring the levels of nitrogen dioxide, particulate matter, and surface ozone after the lockdown began on January 23, 2020. This time the authors reported a 60% reduction in NO 2 and a 35% reduction in particulate matter. So far so good. However, secondary pollutant surface ozone increased by 150–200%. Surface ozone can cause “severe health problems, including pulmonary and cardiac diseases,” state the authors. A variety of household cleaning products and paints, and industrial sources release volatile organic compounds. And it is these compounds, when mixed with NO 2 , that produce surface ozone. Sunlight and higher temperatures create the perfect conditions for this reaction to take place, so the change in seasons may have gone some way to amplifying this situation. Lockdown has offered scientists unprescedented insight into the impact of emission regulations - a silver lining during this tragic situation. Indeed, our modellers throughout Europe have been doing their own investigations and are in the process of writing papers on these emerging dynamics. We will update you when we have further details. 4