Chemistry of Volatile Organic Compounds in the Los Angeles basin: Nighttime Removal of Alkenes and Determination of Emission Ratios Journal of Geophysical Research: Atmospheres

We reanalyze a data set of hydrocarbons in ambient air obtained by gas chromatography-mass spectrometry at a surface site in Pasadena in the Los Angeles basin during the NOAA California Nexus study in 2010. The number of hydrocarbon compounds quanti fied from the chromatograms is expanded through the use of new peak- fitting data analysis software. We also reexamine hydrocarbon removal processes. For alkanes, small alkenes, and aromatics, the removal is determined by the reaction with hydroxyl (OH) radicals. For several highly reactive alkenes, the nighttime removal by ozone and nitrate (NO 3) radicals is also signi ficant. We discuss how this nighttime removal affects the determination of emission ratios versus carbon monoxide (CO) and