SAMPLE PREPARATION FOR RADIOCARBON (C-14) MEASUREMENTS OF CARBONYL-COMPOUNDS IN THE ATMOSPHERE - QUANTIFYING THE BIOGENIC CONTRIBUTION

A method has been developed for the preparation of samples for radioca rbon(C-14) measurements of carbonyl compounds in the atmosphere. Sampl ing on 25 mi 2,4-dinitrophenylhydrazine (DNPH)-coated silica gel cartr idges can be carried out with up to 10.000 l of ambient air with no ad verse effects on sample integrity. Methods for the selective clean-up of the extracts have been investigated. This is a necessary step in pr eparing ambient carbonyl samples for a measurement of the radiocarbon (C-14) content. The method which gave the best results include extract ion of the DNPH cartridge with CH3CN and purification of the carbonyl hydrazones over activated silica gel to remove excess DMPH and non tar get compounds. This method has been validated with laboratory samples and has been proved to give reliable results The radiocarbon data from the first field experiment showed that ambient air over a semi-rural test site in Ispra, Italy on a late summer day contained mainly five c arbonyls (formaldehyde > acetaldehyde > acetone > propanal > butanal) of a mixed biogenic (41-57%) and anthropogenic (43-59%) origin. The me thod will be used in future monitoring of radiocarbon (C-14) on a numb er of test sites in Europe. (C) 1998 Elsevier Science Ltd. All rights reserved.