A comparison of carbonyl compound concentrations at urban roadside and indoor sites

Measurements of formaldehyde, acetaldehyde, hexanal, crotonaldehyde, acrolein, propanal, benzaldehyde and iso-valeraldehyde concentrations were made at two locations (four sites) in London, UK. One location was in Ealing, West London, while the other was in Wood Green, North London. At each location, a residential and commercial roadside site was identified and monitored. The measurements were made using a derivatisation technique in which sample air was pumped through an acidified solution of 2,4-dinitrophenylhydrazine, producing hydrazones which were separated and quantified using High Performance Liquid Chromatography (HPLC). Quantitative determinations were made for 26 and 47 samples at the Ealing and Wood Green locations respectively during 1991 and 1992. The average concentrations determined at the Ealing location for formaldehyde, acetaldehyde, hexanal and crotonaldehyde (taking into account concentrations below the detection limits) were 15.0, 2.5, 1.5 and 1.2 ppb, respectively (residential site), and for the commercial site the corresponding values were 19.2, 1.6, 1.2 and 0.5 ppb. Similarly, at the residential site in Wood Green, the average concentrations for formaldehyde, acetaldehyde, hexanal and crotonaldehyde were 3.4, 1.9, 0.5 and 0.5 ppb, respectively, while at the commercial site the average concentrations for formaldehyde, acetaldehyde and hexanal were 7.4, 2.3 and 0.6 ppb. Acrolein, propanal, benzaldehyde and iso-valeraldehyde were not detected at either survey location. At the residential location in Wood Green, sufficient samples were collected to allow the data to be statistically divided into morning and afternoon collection periods, and the data show that the aldehyde concentrations were generally slightly higher in the afternoon. The observed concentrations reported here are compared with previously reported measurements in the UK and with indoor measurements taken at the Bounds Green Campus of Middlesex University. The advantages and limitations of the method employed are also discussed and compared with a solid-phase extraction technique.