Concentrations of Volatile Organic Compounds in the Megacity of São Paulo in 2006 and 2011/2012 - A Comparative Study

The focus of this study was to measure the Volatile Organic Compounds (VOCs) concentrations in the megacity – Sao Paulo Metropolitan Area (SPMA). The measurements analyzed in this study included 78 hydrocarbon (HC) samples collected during 2006, and 66 samples of HC, 62 of aldehydes and 42 of ethanol collected during 2011-2012. The observational results showed that the consumption of ethanol, gasoline and diesel from 2006 to 2012 increased by 64 %, 23 % and 25 %, respectively, with substantial changes in the atmospheric composition. The 10 most abundant VOCs in the atmosphere found during 2011/2012 at CETESB IPEN/USP air quality monitoring station were ethanol, acetaldehyde, formaldehyde, acetone, propane, ethene, ethane, butane, 1-ethyl-4-methyl benzene, and 1,2,4-trimethyl benzene. During the 2006 campaign, alkanes represented 54.8 % of the total HC concentration, alkenes 29.2 %, aromatics 13.6 %, and alkadienes 2.4 %. On the other hand, during the 2011-2012 campaign, aldehydes represented 35.3 % of the VOCs, ethanol 22.6 %, aromatics 15.5 %, alkanes 13.5 %, acetone 6.8 %, alkenes 6.0 %, and alkadienes with less than 0.1 %.  An increase in VOCs concentrations in the SPMA atmosphere from 2006 to 2012, such as aldehydes and aromatics (which are important ozone precursors) was measured.