Measurements of Atmospheric Carboxylic Acids and Carbonyl Compounds in São Paulo City, Brazil

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• 作者：L. Montero ; P. C. Vasconcellos ; S. R. Souza ; M. A. F. Pires ; O. R. Sá ; nchez-Ccoyllo ; M. F. Andrade ; and L. R. F. Carvalho
• 刊名：Environmental Science & Technology
• 出版年：2001
• 出版时间：August 1, 2001
• 年：2001
• 卷：35
• 期：15
• 页码：3071 - 3081
• 全文大小：188K
• 年卷期：v.35,no.15(August 1, 2001)
• ISSN：1520-5851

文摘

Winter atmospheric measurements of gaseous lowercarbonyl and carboxylic acids were carried out simultaneously(in 1999) at two distinct urban sites located in the city ofSão Paulo, Brazil. The greater metropolitan area of São Paulois the largest industrialized region of Latin America andhas a highly polluted atmosphere. It has an unconventionalmix of vehicle types in that a variety of gasoline blends,including oxygenated ones, are used. Mixing ratios of formicand acetic acids ranged, respectively, from 0.6 to 19.4and from 0.1 to 10.6 ppbv in one of the sites studied andfrom 1.4 to 18.4 and from 0.4 to 6.7 ppbv in the other site. Highvalues of formic to acetic ratios were found, especiallyin the latter site (average = 4.3), suggesting that photochemicalproduction was the predominant source of the formicand acetic acid during the afternoon. Differing from theacids, levels of carbonyls were similar at both sites. Higheraverage mixing ratios of acetaldehyde and formaldehydewere found in the morning (18.9 and 17.2 ppbv) and graduallydecreased from midday (9.5 and 11.8 ppbv) to evening(7.2 and 10.2 ppbv). In the morning, vehicular direct emissionseemed to be the main primary source of formaldehydeand acetaldehyde, whereas at midday and evening thesecompounds appeared to be mainly formed by photochemistry. Secondary photochemical production of organicacids and aldehydes (rather than primary emissions fromvehicles) was shown to be more important in São Paulo'satmosphere from midday to evening, particularly on dayswith strong solar radiation.