17 August 2015
In a first-of-its-kind study, researchers have determined that natural sunlight triggers the release of smog-forming nitrogen oxide compounds from the grime that typically coats buildings, statues and other outdoor surfaces in urban areas. The finding confirms previous laboratory work using simulated sunlight and upends the long-held notion that nitrates in urban grime are ‘locked’ in place.
http://www.sciencedaily.com/releases/2015/08/150817085434.htm
