Ozone and NO2 time-lapse in Philly

Back by popular demand, more time-lapse Philly movies with Air Quality relevant measurements. This video was made for a presentation at the Franklin Institute to STEM Scholars, a group of STEM minded high students in the city of Philadelphia. It’s always a good thing when the students ask if there are anymore videos to watch!

Philadelphia Time Lapse with Ozone from DeCarlo Laboratory on Vimeo.

The NO2 and O3 data are provided by the Philadelphia Air Management Services.

A quick overview of what is going on with the video:

12AM to 6AM – not a lot happening
6AM to 7 AM – Emissions of NO from cars, reacts with O3 making NO2 and reducing O3 concentrations
7AM – noon – Sun rises and photolyzes NO2 (NO2 breaks down to NO + O in sunlight), increasing O3 levels, along with photochemical production of Ozone.
noon – 6 PM – Afternoon gets cloudy – dips are seen in the solar radiation measurement with cloudy conditions
6PM – midnight – At sunset NO2 is no longer photolyzed and increases in concentration. Continued emissions of NO from cars decrease O3 concentration until emissions slow down and the evening settles down into a quasi steady state from about 10 PM onwards.

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