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

Abstract

We measured stable hydrogen isotope ratios (delta D) 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 dD values of the C-27, C-29 and C-31 n-alkanes (delta D-ALK) show a significant negative correlation with the CPI values of n-alkanes (r(2) = 0.26, p < 0.01), suggesting that the delta D-ALK variations are partly attributed to a superimposed contribution from fossil fuel hydrocarbons. Seasonal variations in the concentrations of the C-22-C-28 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 C-26/FA and low C-24/FA ratios in spring, autumn and winter samples suggest that the C-26 n-fatty acids are more abundantly transported from the Asian continent during these seasons. Seasonal variations in the delta D of the C-22-C-26 even-carbon numbered n-fatty acids exhibit significant enrichment with D (by similar to 40 parts per thousand) in May and June to August samples, whereas the delta D of the C28 n-fatty acids gradually decrease during summer. The magnitude of the delta D offsets (similar to 45 parts per thousand) between the C-28 n-fatty acid and the other homologues are much larger than those observed in East Asia spanning 18 degrees N-50 degrees N latitude (ca. 30 parts per thousand), suggesting that the decoupling is likely attributed to the mixing of distinct source vegetation with different delta D ratios. Comparison of the weighted-mean delta D values of n-fatty acids (delta D-FA) between air mass source categories revealed relatively low values (similar to-170 parts per thousand) in samples with trajectories from the northeastern part of the Asian continent, supporting that the delta 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 delta 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. (C) 2013 Elsevier Ltd. All rights reserved.