The Atomic Spectra and Light Pollution

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At night, nature tries to clean the air of the mix of molecules from all the factories and cars. The nitrate radical, a special form of nitrogen oxide, helps to clean the air under the cover of darkness. This radical helps to break down chemicals that would otherwise create smog and ozone. Chemical compounds that become oxidized and removed from the air are due to contact with NO or NO₂. When the sun rises, the process stops because sunlight breaks down the nitrate radical.

Image: www.atmosphere.mpg.de/enid/24z.html Scheme by Elmar Uherek

A study presented at the American Geophysical Union meeting, indicated that nighttime light pollution over Los Angeles slowed the cleansing process by up to 7%. At the same time, the city lights can increase the necessary components for ozone pollution the next by up to 5%, as presented by Harald Stark from the US National Oceanic and Atmospheric Administration. Stark also noted that city lights had wavelengths and intensities that drives nitrate radical photolysis. Different street lights have different photolysis rates. Photolysis is a process in which molecules are broken down into smaller units by the absorption of light.

The electromagnetic spectrum is a wide range of energy frequencies that extend from radio waves to gamma waves. Energy (E) from the sun is electromagnetic energy. This energy is dependent upon the frequency (v) of the wave. Energy can be calculated by the following formula: E =hv. The letter h represents Planck’s constant. Planck’s constant relates the energy of a photon to the frequency of the electromagnetic wave.

From CoreChem: 21.0: Prelude to Spectroscopy

References:

Amos, Jonathan. "BBC News - City lighting 'boosts pollution'." BBC - Homepage. N.p., 14 Dec. 2010. Web. 26 July 2011. <http://www.bbc.co.uk/news/science-environment-11990737>.
Kemsley, Jyllian N. . "Monitoring The Skies | Cover Story | Chemical & Engineering News." ACS Publications - Cookie absent. N.p., 7 Feb. 2011. Web. 26 July 2011. <http://pubs.acs.org/cen/coverstory/89/8906cover.html>.
Uherek, Elmar. "- night & nitrate." Atmospheric Chemistry: Start Page. Max Planck Institute for Chemistry, 16 Feb. 2006. Web. 26 July 2011. <www.atmosphere.mpg.de/enid/24z.html>.

Contributors and Attributions

Ed Vitz (Kutztown University), John W. Moore (UW-Madison), Justin Shorb (Hope College), Xavier Prat-Resina (University of Minnesota Rochester), Tim Wendorff, and Adam Hahn.