Volatile carbonylic compounds in downtown Santiago, Chile.
Formaldehyde, acetaldehyde, acetone, propanal, butanal, 2-butenal, 3-methylbutanal, hexanal, benzaldehyde, 2-methylbenzaldehyde, and 2,5-dimethylbenzaldehyde were measured during six spring days at downtown Santiago de Chile. Measurements were performed 24h/day and averaged over three hour periods. The averages of the maxima (ppbv) were, formaldehyde: 3.9+/-1.4; butanal: 3.3+/-3.4; acetaldehyde: 3.0+/-0.9; acetone: 2.4+/-1.0; 2-butenal: 0.56+/-0.52; propanal: 0.46+/-0.21; benzaldehyde: 0.34+/-0.3; 3-butanal: 0.11+/-0.05; hexanal: 0.11+/-0.08; 2-methylbenzaldehyde: 0.08+/-0.05; 2,5-dimethylbenzaldehyde: 0.05+/-0.03. Aliphatic aldehydes (C1-C3) are strongly correlated among them and weakly with primary (toluene) and secondary (ozone plus nitrogen dioxide or PAN) pollutants. In particular, the correlation between acetaldehyde and propanal values remains even if diurnal and nocturnal data are considered separately, indicating similar sources. All these aldehydes present maxima values in the morning (9-12h) and minima at night (0-3h). The best correlation is observed when butanal and 2-butenal data are considered (r=0.99, butanal/2-butenal=6.2). These compounds present maxima values during the 3-6h period, with minima values in the 0-3h period. These data imply a strong pre-dawn emission. Other aldehydes show different daily profiles, suggesting unrelated origins. Formaldehyde is the aldehyde whose concentration values best correlate with the levels of oxidants. The contribution of primary emissions and photochemical processes to formaldehyde concentrations were estimated by using a multiple regression. This treatment indicates that (32+/-16)% of measured values arise from direct emissions, while (79+/-23)% is attributable to secondary formation.
Rubio
María A
MA
Faculty of Chemistry and Biology, University of Santiago, P.O. Box 40, C-33, Santiago, Chile. mrubio@lauca.usach.cl
Zamorano
Natalia
N
Lissi
Eduardo
E
Rojas
Alicia
A
Gutiérrez
Luis
L
von Baer
Dietrich
D
D000096:Acetone / Q000032:analysis; D000393:Air Pollutants / Q000032:analysis*; D000447:Aldehydes / Q000032:analysis*; D002677:Chile; D002947:Cities; D004784:Environmental Monitoring; D009585:Nitrogen Dioxide / Q000032:analysis; D010083:Oxidants, Photochemical / Q000032:analysis*; D010126:Ozone / Q000032:analysis; D010463:Peracetic Acid / Q000031:analogs & derivatives / Q000032:analysis; D014050:Toluene / Q000032:analysis
D000393:Air Pollutants; D000447:Aldehydes; D010083:Oxidants, Photochemical; D000096:Acetone; D014050:Toluene; D010126:Ozone; D010463:Peracetic Acid; D009585:Nitrogen Dioxide; C004185:peroxyacetyl nitrate