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Determining VOCs Reactivity for Ozone Forming Potential in the Megacity of São Paulo

Category: Air Pollution Modeling

Article In Press
DOI: 10.4209/aaqr.2017.10.0361
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Débora Souza Alvim 1,6, Luciana Vanni Gatti2,6, Sergio Machado Corrêa3, Júlio Barboza Chiquetto4, Guaciara Macedo Santos5, Carlos de Souza Rossatti6, Angélica Pretto6, José Roberto Rozante2, Silvio Nilo Figueroa2, Jayant Pendharkar2, Paulo Nobre2

  • 1 Center of Natural Sciences and Humanities (CCNH), Federal University of ABC (UFABC), Santo André, SP, Brazil
  • 2 Center for Weather Forecasting and Climate Studies (CPTEC), and Earth System Science Center (CCST), National Institute for Space Research, Cachoeira Paulista, SP, Brazil
  • 3 Faculty of Technology, Rio de Janeiro State University (UERJ), Resende, RJ, Brazil
  • 4 Department of Geography, University of Sao Paulo (USP), São Paulo, SP, Brazil
  • 5 Department of Earth System Science, University of California, Irvine, CA 92697, USA
  • 6 Chemistry and Environment Center, Institute of Nuclear Energy Research (IPEN), São Paulo, SP, Brazil

Highlights

During 2016, the 1-hour national standard for ozone was exceeded on 76 days.
Carbonyls VOCs emissions will increase worldwide due to the increase in ethanol use.
Aldehydes were 35.3 % of total VOCs mass, ethanol was 22.6% and aromatics 15.7%.
Ozone forming potential: 74% from aldehydes (61.2% acetaldehyde), aromatics 14.5%.
The most effective solution to limit the O3 levels is to reduce the oxygenated VOCs.


Abstract

High ozone (O3) concentrations are a major concern about air quality in the São Paulo Metropolitan Area (SPMA). During 2016, the 8-hour state standard of 140 µg m–3 was exceeded on 32 days, whereas the 1-hour national standard of 160 µg m–3 was exceeded on 76 days. Exposure to such unhealthy O3 levels and other pollutants can lead to respiratory disease. The focus of this study is to determine the main O3 precursor in terms of the volatile organic compounds (VOCs) in order to provide a scientific basis for controlling this pollutant. In this work, 66 samples of hydrocarbons, 62 of aldehydes and 42 of ethanol were taken during the period from September 2011 to August 2012 from 7:00 to 9:00 a.m. The OZIPR trajectory model and SAPRC atmospheric chemical mechanism were used to determine the major O3 precursors. During the studied period, aldehydes represented 35.3% of the VOCs, followed by ethanol (22.6%), aromatic compounds (15.7%), alkanes (13.5%), ketones (6.8%), alkenes (6.0%) and alkadienes (less than 0.1%). Considering the concentration of VOCs and their typical reactivity, the simulation results showed that acetaldehyde contributed 61.2% of the O3 formation. The total aldehydes contributed 74%, followed by aromatics (14.5%), alkenes (10.2%), alkanes (1.3%) and alkadienes (e.g., isoprene; 0.03%). Simulation results for the SPMA showed that the most effective alternative for limiting the O3 levels was reducing the VOC emissions, mainly the aldehydes.

Keywords

Ozone forming potential Air quality VOCs Incremental reactivity


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