Sources And Form Distribution Of Lipids Biomarkers In Representative Oceanic Sediments

In recent decades, lipids in sediments are widely used as biomarkers to reconstruct paleoenvirenment and paleoclimate situation in long-term time scale, and prove to be effective, but the application in short-term time scale is infrequent, so what is the relationship between the environmental information conserved in lipids biomarkers and the real variation of environment in short-term time scale? Researches show that lipids biomarkers in sediments, especially fatty acids, occur in different forms, and the distribution in forms seems to be various in different sediments, so what is the pattern of form distribution of lipids biomarkers in sediments in inshore of China?To dissolve questions brought above, two sediments cores in frequent harmful algal bloom areas of the East China Sea and surficial sediments in southern coastal area of Shandong Peninsula were collected, and then two pools of lipids were obtained by sequential treatment: (1) an organic solvent-extractable free fraction, (2) an bound fraction released by alkaline hydrolysis of the solvent-extracted material. Results reveal that composition of fatty acids in all sediments from East China Sea and southern coastal area of Shandong Peninsula are similar, the fatty acids are in obvious even carbon number predominance, with C16 fatty acids as the main peak and characteristic of single peak distribution, the chain length between 12 to 32 indicate mixture sources of autochthonous and allochthonous input, but mainly by autochthonous input; fatty acids exist as bound forms in majority; the vertical form distribution of fatty acids in the two cores performs oppositely, and the differences in degration of organic matter between two cores may be the reason.Alcohols and ketones (A&K) in the sediments indicate that autochthonous input is the main source and sterols are the primary component of A&K, except in surficial sediments in zd-21, the concentration of C29 sterol are the highest, C37 alkenones and C30 diols are detected in the sediments, which proves the existence of haptophytes and eustigmatophytes in upper water, the form pattern of A&K is complex, in sediments of zd-21 core,southern coastal area of Shandong Peninsula and upper 10cm fractions of hb-8 core, A&K mainly exist in free forms, and in rest samples of hb-8 core bound form are predominant, in addition, phytols are mainly in bound forms, but diols and ketones are mainly free. The results of reconstruction for phytoplankton community by dinosterol brassicasterol and alkenone reveal that haptophytes are in minority in the study areas, and in recently several decades, the ratio of haptophytes exhibits a decreasing trend, and the radio of dinoflagellates performs oppositely, which may be due to the aggravation of eutrophication.Results of hydrocarbons reveal that terrestrial input is the main source of hydrocarbons in the sediments, hydrocarbon index show that, in zd-21 grassland vegetation is predominant in hydrocarbon's sources areas, but in southern coastal area of Shandong Peninsula, woody plants are the most, and in hb-8, the vegetation of sources areas present an obvious trend: in recently decades herbage is replaced by woody plant gradually.