Character and Paleoenvironm ental Significance of the Pigment and Organic δ<sup>13</sup>C in Sediments of Nansihu Lake

Abstract

湖泊沉积物中的色素含量与种类是研究湖泊初始生产力和湖泊环境的有效手段之一.而有机碳同位素比值反映了沉积有机物来源信息.本文在对南四湖沉积剖面中总有机碳含量分析的基础上,测定了有机碳的同位素比值,同时通过剖面中色素指标的分析,揭示该湖泊环境演化历史.研究表明,南四湖成湖时代为2.45kaB.P,成期水体主要来自黄河泛滥；其次,南四湖东西沉积环境差异较大,西部(微山湖)主要受黄河泛滥影响,东部(独山湖)则为山麓碎屑沉积；近代南四湖中蓝藻大量繁盛,湖泊具有逐步向富营养化发展的趋势.;Content of total organic carbon in lake sedim ents is usually used to obtain the lake paleoprimary productivity．Such organic matter will conduct a series of chemicaI and biological reaction after it deposits in the lake bo ttom． Therefore the total organic carbon in lake sediments only offers rough information about lake paleoprim ary productivity． Based on the content of total organic carbon and the organic 8 C of the sedim ents．the source of sediment has been distinguished． By analyzing the pigment index， the environmental evolution history of the lake has been recovered， These researches made it clear that Nana ihu Lake has formed in 2，45kaBP with the lake water mainly coling from the Yellow River． The deposition environment of the east part of the lake is different from that of the west， In the west part(W eishanhu Lake)the sediments mainly com e from the flood plain materials of the Yellow River．while in the east part (Dushanhu Lake)the sediments mainly come from the footslope materials，Recently，the Cyanophyta is flourishing in the lake and the lake gradually comes into the eutrophication stage.