南黄海北部表层沉积物中生物标志物的组成特征及其地球化学意义

Characteristics of biomarkers composition and geochemical significance of surface sediments in the northern part of south Yellow Sea

通过对南黄海北部14个站位的19个表层沉积物样品进行了粒度、有机碳、GC-FID和GC-MS-MS测定,探讨沉积物有机质中生物标志物组成特征及地球化学意义。研究区表明,沉积物有机碳含量较高,正构烷烃呈双峰分布,具有明显奇偶优势、平均L/H为0.36,说明沉积物中陆源高等植物贡献占优,分析对比表明其沉积物可能主要来自古黄河输入。类异戊二烯烃Pr/Ph均值0.46,表明有机质沉积于强还原环境;Pr/C_(17)和Ph/C_(18)值均小于1,并且随深度有减小的趋势,反映了研究区微生物的降解作用。甾类化合物C_(29)豆甾烷>C_((?))胆甾烷>C_(28)麦角甾烷,说明萜类化合物和甾类化合物主要为陆相输入。较高OEP值、高丰度的藿烯和莫烷及甾烷S构型含量均反映了现代沉积物中有机质未熟-低熟特征,但由于原始母质影响和微生物发育,Ts/Tm和C_(31)αβS/(S+R)、C_(32)αβS/(S+R)、C_(33)αβS/(S+R)和C_(29)αββ/(ααα+αββ)值较高。

19 surface sediment samples collected from the 14 sites in the northern part of the South Yellow Sea were analyzed in grain size,total organic carbon （TOC） and biomarker detected by GC-FID and GC-MS-MS. The TOC of sediments was characterized by coastal deposition. Their n-alkanes showed a bimodal distribution with the obvious odd- even predominance. The mean value of L/H （C21-/ nC22=＋） was 0.4. These parameters implied that the organic matter （OM） came from terrestrial high plants. Further more,the OM was transported into the sea by ancient Yellow River. The mean value of Pr/Ph was 0.46 ,which indicated that the environment of deposition was intense reduction condition. Most of Pr/C17 and Ph/C18 values were less than 1 and had the reduction tendency along with the increase of depth. This may be resulted by the microbial degradation. The distribution of steranes displayed C：9〉C27〉C2s,revealing that they were mainly input from terrestrial plant. The maturity of OM was immature,and characterized by high contents of hopenoid alkenes （TJ3） ,moretanoids and S-steranes. However,these values of Ts/Tm, C31αβS/（S＋R）,C32αβS/（S＋R）, C33αββS/（S＋R） and C29 αββ（ααα＋αββ） displayed high maturity as a result of the original parent materials and microbial degradation.