Influence of aerosol source regions and transport pathway on δD of terrestrial biomarkers in atmospheric aerosols from the East China Sea

We measured stable hydrogen isotope ratios (δD) of terrestrial biomarkers (n-alkanes and n-fatty acids) in atmospheric total suspended particles collected at Jeju Island in the East China Sea, from April 2001 to March 2002, to better understand the influence of long-range atmospheric transport on their seasonal variations. The δD values of the C₂₇, C₂₉ and C₃₁ n-alkanes (δD_ALK) show a significant negative correlation with the CPI values of n-alkanes (r²=0.26, p<0.01), suggesting that the δD_ALK variations are partly attributed to a superimposed contribution from fossil fuel hydrocarbons. Seasonal variations in the concentrations of the C₂₂-C₂₈ even-carbon numbered n-fatty acids revealed relatively high concentrations in spring, autumn and winter seasons, in which the air masses are transported from northeast Asia. In contrast, the concentrations are low in summer when the air masses are transported from Southeast Asia and the Pacific. Relatively high C₂₆/FA and low C₂₄/FA ratios in spring, autumn and winter samples suggest that the C₂₆ n-fatty acids are more abundantly transported from the Asian continent during these seasons. Seasonal variations in the δ D of the C₂₂-C₂₆ even-carbon numbered n-fatty acids exhibit significant enrichment with D (by ~40‰) in May and June to August samples, whereas the δ D of the C₂₈ n-fatty acids gradually decrease during summer. The magnitude of the δ D offsets (~45‰) between the C₂₈ n-fatty acid and the other homologues are much larger than those observed in East Asia spanning 18 ° N-50 ° N latitude (ca. 30‰), suggesting that the decoupling is likely attributed to the mixing of distinct source vegetation with different δ D ratios. Comparison of the weighted-mean δ D values of n-fatty acids (δ D _FA) between air mass source categories revealed relatively low values (~-170‰) in samples with trajectories from the northeastern part of the Asian continent, supporting that the δ D analyses may be a powerful tool in deciphering the source regions of terrestrial biomarkers in atmospheric aerosols from the Asian continent. The results of this study provides important implications for paleoclimate studies that the δ D variations of long-range transported terrestrial biomarkers in remote ocean sediments may have recorded past changes in source strengths of the biomarkers and therefore have a potential to reconstruct paleo-wind patterns and transport of terrestrial carbon over the Pacific.