Compound-specific carbon isotope compositions of individual long-chain n-alkanes in severe Asian dust episodes in the North China coast in 2002

The molecular compositions and compound-specific carbon isotope compositions of individual long-chain n-alkanes of atmospheric aerosols collected during two severe Asian dust episodes in Qingdao in spring of 2002 were analyzed using gas chromatography/mass spectrometry (GC/MS) and gas chromatography/isotope ratio mass spectrometry (GC/IRMS). Typical plant wax n-alkanes (C-29 and C-31) had lower delta C-13 values than those from anthropogenic (engine exhaust) sources (C-21-C-23). The average delta C-13 value of plant wax n-alkane C-29 in non-dust episode periods was -30.5 parts per thousand. (-30.3 parts per thousand--31.9 parts per thousand), while -31.3 parts per thousand. (-31.1 parts per thousand - -31.5 parts per thousand) in dust episode periods; for C31, it was -31.4%. (-31.1 parts per thousand - -33.0 parts per thousand) in non-dust episode periods, and -31.7 parts per thousand (-31.3 parts per thousand - -32.6 parts per thousand) in dust episode periods. Plant wax in the dust episode samples was mainly from herbaceous plants via long-range transport, while local plant wax was mainly from deciduous plants and woody plants. In North China coast, 83.3% of the plant wax in the severe dust episode samples was from C-3 plants while 80.0% for the non-dust samples, indicating that plant wax transported to the northwestern Pacific Ocean by airborne dust from East Asia was mainly from C-3 plants. The results suggest that the molecular and molecular-isotopic compositions of individual long-chain n-alkanes can, as an effective indicator, identify the terrestrial organic components in the dust from East Asia and sediments in the northwest Pacific Ocean.