VARIABILITY OF STABLE CARBON ISOTOPIC COMPOSITIONS IN INDIVIDUAL FATTY-ACIDS FROM COMBUSTION OF C4 AND C3 PLANTS - IMPLICATIONS FOR BIOMASSBURNING

The isotopic characterization of trace organic species produced during biomass burning may allow a better understanding of the source and fa te of combustion-derived organic matter. In order to assess the utilit y of compound specific isotope analysis (CSIA) of fatty acids as a mea ns to distinguish the sources of these species in atmospheric aerosols , the isotopic signatures of fatty acids extracted from unburned C-4 a nd C-3 vegetation have been determined. Carbon isotopic signatures of fatty acids from unburned C-4 vegetation ranged from -21.1 parts per t housand to -28.2 parts per thousand, whereas those from C-3 vegetation ranged from -32.4 parts per thousand to - 38.5 parts per thousand. Fa tty acids isolated from aerosols produced during controlled laboratory burns of C-4 vegetation showed an isotopic depletion of 2 parts per t housand to 6 parts per thousand relative to those extracted from the u nburned plant. However, the opposite relationship was observed for C-3 vegetation, with the aerosol fatty acids exhibiting and isotopic enri chment of 2 parts per thousand to 7 parts per thousand relative to tho se from the unburned plant. Combustion-derived fatty acids may be dist inguished from those species that arise from erosion of unburned plant debris. CSIA of fatty acids produced during field burns of C-4 and C- 3 vegetation suggests that isotopic characterization of these species in atmospheric aerosols may be useful in determining the fate of organ ic matter produced during biomass burning. (C) 1998 Elsevier Science B .V. All rights reserved.