Speciated Ambient Carbonyls in Rio de Janeiro, Brazil

Abstract

Carbonyls in urban air continue to receive scientific and regulatory attention as toxic air contaminants and for their important role in photochemical smog. However, few data are available for speciated carbonyls in urban air. Ambient concentrations of up to 61 carbonyls have been measured in Rio de Janeiro, Brazil. The most abundant carbonyls were formaldehyde and acetaldehyde (study-averaged concentrations of 10.8 +/- 4.1 and 10.4 +/- 4.6 microg m(-3), respectively, in samples of 3-h duration collected from May to November 2000 at a downtown location during the morning vehicle commute) followed by acetone, 2-butanone, and benzaldehyde. Ambient concentrations of other carbonyls (except acetophenone) correlated well with those of acetaldehyde and of formaldehyde. This study examines the ambient acetaldehyde/ambient formaldehyde concentration ratio in Brazilian cities since the mid-1980s in the context of changes in Brazil's reliance on ethanol as a vehicle fuel. This ratio has begun to decrease in recent years due to fleet turnover and is likely to decrease further as older cars fueled with ethanol are replaced by lower-emitting models that run on a gasoline-ethanol blend. The carbonyls measured are ranked with respect to ozone formation potential (using MIR coefficients) and reaction with OH (using carbonyl-OH reaction rate constants). Ozone formation is dominated by formaldehyde (43% of total) followed by acetaldehyde (32%) and methylglyoxal (8%); other carbonyls each contributed < or = 4% of total. For reaction with OH, acetaldehyde ranks first closely followed by formaldehyde.

Atmospheric BTEX and carbonyls during summer seasons of 2008–2010 in Beijing

“…Besides, photolysis of the carbonyls is an important source for atmospheric hydroxyl radical (OH) and peroxy radicals (HO 2 , RO 2 ) which are further involved in photochemical reactions (Atkinson and Arey, 2003). Carbonyls and BTEX in the urban air have also aroused great attention due to their toxicity, mutagens, and carcinogens (Grosjean et al, 2002), e.g. the life risk of chronic leukaemia is 4.4e7.6 Â 10 À6 when atmospheric concentration of benzene is equal to 1 mg m À3 (Crump, 1994).…”

Influences of characteristic meteorological conditions on atmospheric carbonyls in Beijing, China

“…Carbonyls play a crucial role in the formation of photochemical smog and secondary organic aerosol (SOA) because the free radicals produced from the photolysis of carbonyls can react rapidly with OH radical and serve as the precursors of ozone (Finlayson-Pitts and Pitts, 1997). In metropolitan air, carbonyls are primarily emitted by mobile vehicles and stationary sources and secondarily produced by the photo-oxidation of their precursors (Grosjean et al, 2002). Any meteorological variations affecting the atmospheric conditions will influence the atmospheric carbonyls and accordingly change the levels of ozone and aerosol.…”

Comparison of rural and urban atmospheric aldehydes in Londrina, Brazil

“…14 Another reason for the increase in interest is that ethanol is produced from different types of biomass, mainly sugar cane in Brazil, making it a renewable fuel that limits the discharge of fossil carbon dioxide (CO 2 ) which most probably contributes to the global climate changes. 15 Published aldehyde measurements in the urban atmosphere in Brazil have been limited to the largest Brazilian centers like Rio de Janeiro, São Paulo, Salvador and Porto Alegre [7][8][9][10][11][16][17][18][19] and data for rural areas are even scarcer.…”