A COMPARISON OF CARBONYL COMPOUND CONCENTRATIONS AT URBAN ROADSIDE AND INDOOR SITES

Measurements of formaldehyde, acetaldehyde, hexanal, crotonaldehyde, a crolein, propanal, benzaldehyde and iso-valeraldehyde concentrations w ere made at two locations (four sites) in London, UK. One location was in Ealing, West London, while the other was in Wood Green, North Lond on. At each location, a residential and commercial roadside site was i dentified and monitored. The measurements were made using a derivatisa tion technique in which sample air was pumped through an acidified sol ution of 2,4-dinitrophenylhydrazine, producing hydrazones which were s eparated 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 form aldehyde, acetaldehyde, hexanal and crotonaldehyde (taking into accoun t concentrations below the detection limits) were 15.0, 2.5, 1.5 and 1 .2 ppb, respectively (residential site), and for the commercial site t he 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 fo rmaldehyde, 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 locati on in Wood Green, sufficient samples were collected to allow the data to be statistically divided into morning and afternoon collection peri ods, and the data show that the aldehyde concentrations were generally slightly higher in the afternoon. The observed concentrations reporte d here are compared with previously reported measurements in the UK an d with indoor measurements taken at the Bounds Green Campus of Middles ex University. The advantages and limitations of the method employed a re also discussed and compared with a solid-phase extraction technique .