浙江三门湾柱样沉积中长链烯酮、正构烷烃和多环芳烃组成、分布特征及对厄尔尼诺/拉尼娜事件的追踪

The composition and distribution characteristics of the long-chain ketene, n-alkanes and Polycyclic Aromatic Hydrocarbon(PAH)in the sediments of core in the Sanmen Bay of Zhejiang, and the tracking the Nio/La Nia events

利用气相色谱对浙江三门湾H30柱样沉积中长链烯酮、正构烷烃和多环芳烃组成和来源进行分析,并对柱样沉积中相关有机地化指标与厄尔尼诺/拉尼娜事件的关联性进行了探讨。正构烷烃GC谱图显示碳数分布范围为C14～C35,呈双峰型,低碳峰群的主峰为C17～C19,高碳峰群的主峰为C27～C31,这种分布特征表明三门湾沉积物中陆地高等植物和海洋菌藻类的烷烃共存。根据多环芳烃的菲/蒽比值、荧蒽/芘比值、2～3环化合物总量和4环以上化合物总量等可推断,三门湾沉积地层中的多环芳烃主要来源于化石燃料的不完全燃烧物和石油源(航运事件)。基于精确的210Pb定年,1822—2005年间正构烷烃和多环芳烃含量分布、分子组合特征指数可能与厄尔尼诺/拉尼娜事件具有一定的关联。具体表现在,长链正构烷烃的含量与总多环芳烃含量变化具有良好的一致性,二者含量和苝、CPI、烷烃C15-C19在厄尔尼诺年增加(尤其在厄尔尼诺结束年),指示陆源有机质输入和海洋菌藻类一致增加;而二者含量和∑C21-/∑C22+、烷烃C15-C19在拉尼娜事件时降低,表明海洋菌藻类减少。

Gas chromatographic （GC） measurements were performed to exploring the compositions and sources of the long-chain ketene, n-alkanes and polycyclic aromatic hydrocarbons （PAHs） in the sediment of Core H30 obtained from the Sanmen Bay, Zhejiang. Furthermore, the relationship between some organic geochemical indexes and the ENSO dynamics were explored. According to the GC map of N-alkanes, the carbon numbers distributed as a bimodal type, ranging between C 14 and C35. The main peak of the group of smaller carbon numbers is C17-C19; and that of the group of larger carbon numbers is C27-C31. Such carbon numbers distribution of n-alkanes suggested that the alkanes of both terrestrial higher plants and the marine phycomycetes coexisted in the sediment of Sanmen Bay. According to the phenanthrene/anthracene ratio, the fluoranthene/pyrene ratio, the total PAHs with 2-3 rings and the total PAHs with≥4 rings, the PAH in the Sanmen Bay sediment mainly originated from incomplete combustion of fossil fuels and oil spill in shipping accidents. On the basis of accurate 210pb determination, between 1822 and 2005 A.D., the total PAHs, the contents of long-chain n-alkanes and pyrylo, the alkanes C15-C19 and the carbon preference index increased during the E1 Nifio years, especially in end years of the E1 Nino events, which indicated the increase in both terrestrial organism input and marine phycomycetes. While during the La Nifia years, the total PAHs, the content of long-chain n-alkanes, the alkanes C15-4219 and ∑C21-/∑C22＋ were reduced, suggesting the decrease in marine phycomycetes.