Carbon isotopic composition of fatty acids in the marine aerosols from the western North Pacific: implication for the source and atmospheric transport.

A combined molecular and isotopic approach was used in this study to reveal the source and transport of aerosols at a remote oceanic site. Fatty acid distributions and stable carbon isotopic compositions of individual fatty acids were determined in the aerosol samples collected at Chichi-Jima in the western North Pacific over a period of 41 months. Fatty acid concentration and isotopic composition delta13C (vs PDB) exhibited temporal variations. Concentrations of fatty acids (C12-C34) ranged from 7.6 to 20.7 ng/m3. The concentrations of lower molecular weight (LMW) fatty acids (C12 -C19) tend to decrease in winter and increase in summer, whereas the higher molecular weight (HMW) C20-34 fatty acids exhibited a reversed trend. Compound-specific isotopic analysis revealed that the LMW fatty acids exhibited consistently less negative delta13C values than the HMW fatty acids. However, both the LMW and HMW fatty acids displayed a similar trend of temporal variations in delta13C, suggesting thatthe fatty acids experienced similar atmospheric pathways and transport processes to the remote marine atmosphere, whereas the difference in absolute delta13C reflects the different sources of the fatty acids.