长江口表层沉积物孢粉相特征及其在碳循环中的意义

选自长江口F2-F5站住的4个表层沉积物及其粒度分级（1～8Ф）样品，经过孢粉相和热解检测，探讨有机质特征及其在碳循环中的命运。未分级样品的孢粉相主要由木质组织、丝炭和黑团块组成，显示陆地输入有机质的贡献巨大。样品分级后，孢粉相面貌发生显著变化。细粒的8函中无定形为主，其他粒级（2～7Ф）中主要由结构有机质组成。细粒的...

The characteristics of Palynofacies of surface sediments collected from the Changjiang Estuary and its significance in carbon cycle

Palynofacies and pyrolysis were applied to four surface sediment samples(F2-F5) from the Changjiang estuary and their 1-8Φ particle size fractions to discuss the characteristics of organic matter(OM) and their fate in carbon cycle.The palynofacies of bulk samples are mainly comprised of woody tissue,charcoal,and black mass OM,which indicates a large contribution of terrestrial organic matter input.After fractionation,the feature of palynofacies changed significantly.Fine particle size fraction(8Φ) dominated in amorphous OM,while other fractions(2-7Φ) were comprised of structural OM.Fine particle size fraction(8Φ) was characterized by high HI,S2 and low Tmax value,which suggests an aquatic organic matter origin.However,the OMs of other size fractions(2-7Φ) were characterized by terrestrial organic matter input and great oxidative degradation.In samples of F4 and F5,which are far from the Changjiang estuary,about 70% of the TOC was contributed by fine particle size fraction(8Φ),while the TOC is homogeneous in different size fractions of samples of F2 and F3 which are near the estuary.The amorphous OM in fine size fraction(8Φ) was protected by clay minerals from biodegradation and oxidative degradation.These OM flocculate and precipitate rapidly,and shortened the process from biosphere,hydrosphere to lithosphere.As a result,this may prolong the period of carbon cycling.The OMs in other fractions(2-7Φ) underwent oxidative degradation and were preserved in sediments with the longest period of carbon cycling.Consequently,the relationship between sedimentary OM and clay mineral and their influence on the time of carbon cycling should be concerned.This may help us to get some future understanding of carbon cycle which is still uncertain.