网湖沉积物正构烷烃分布特征及其记录的环境变化

发布时间：2018-07-11 10:32

本文选题：长江中游 + 网湖　；参考：《环境科学》2017年09期

【摘要】：通过对网湖沉积岩芯中正构烷烃含量和组成特征的分析,探讨了网湖近百年来的湖泊环境变化.结果表明,网湖沉积岩芯中正构烷烃的碳数范围在n-C14~n-C33之间,其中以高碳数组分为主,并具有明显的奇偶优势,反映了沉积物有机质以大型水生植物和陆生植物贡献为主,较低的2n-C31/(n-C27+n-C29)比值指示陆源输入中以木本植物输入为主.根据正构烷烃参数指示的沉积物有机质来源变化特征,近百年来网湖水体环境变化具有如下3个阶段:20世纪50年代以前,网湖与长江水体交换频繁,湖泊水体处于低营养环境状态,沉积物正构烷烃高/低分子量正构烷烃比值(H/L)和陆/水生类脂物比值(TAR)较高,沉积物有机质主要来源于陆生植物和大型水生植物,湖泊浮游藻类贡献少;20世纪50~80年代,H/L和TAR值明显下降,中、短链正构烷烃的比例略有升高,表明陆源植被对沉积物有机质的贡献降低,水生植物和浮游藻类贡献的有机质增加,但较低的2n-C17/(n-C23+n-C25)值表明浮游藻类有机质较低,此时湖泊水体较为稳定,湖泊受长江水位影响减小,湖泊营养水平有所升高;1980s以来,总体上湖泊受流域人类活动影响明显,湖泊水体营养水平升高,沉积物正构烷烃表现为H/L和TAR值升高后下降,正构烷烃总量和2n-C17/(n-C23+n-C25)比值显著升高,2000年后尤其明显,表明湖泊沉积物有机质输入增加,其中湖泊浮游藻类贡献明显增加.
[Abstract]:Based on the analysis of the content and composition of n-alkanes in the depositional core of the reticustrine lake, the changes of the lake environment in the last hundred years are discussed. The results show that the carbon number of n-alkanes is in the range of n-C14n-C33, in which the high carbon array is dominant, and the advantages of parity and even are obvious, which indicates that the organic matter of sediments is mainly contributed by macroaquatic plants and terrestrial plants. The lower ratio of 2n-C31 / (n-C27 n-C29) indicates that woody plant input is the main input. According to the source characteristics of organic matter in sediments indicated by normal alkane parameters, the environmental changes of the water body of the net lake in the last hundred years have three stages: before the 1950s, the water bodies of the net lake and the Yangtze River are exchanged frequently. The lake water was in a low nutrient environment, and the ratio of normal alkanes (H / L) and lipids (tar) in sediments was higher. The organic matter in sediments was mainly derived from terrestrial plants and macroaquatic plants. The contribution of phytoplankton in lakes was less than that in the 1950s and 1980s, and the ratio of n-alkanes of short chain and middle chain decreased obviously, indicating that the contribution of terrestrial vegetation to sediment organic matter decreased, and that of aquatic plants and phytoplankton increased. However, the lower value of 2n-C17 / (n-C23n-C25) indicates that the organic matter of phytoplankton is low, the lake water is stable, the lake is affected by the Yangtze River water level and the lake nutrition level has been increased since 1980's, and the lake is obviously affected by the human activities in the basin. The nutrient level of lake water increased, the normal alkanes in sediments decreased after the increase of H / L and tar values, the total amount of normal alkanes and the ratio of 2n-C17 / (n-C23 n-C25) increased significantly, especially after 2000, which indicated that the input of organic matter in lake sediments increased. Among them, the contribution of phytoplankton in lakes is obviously increased.
【作者单位】：中国科学院南京地理与湖泊研究所湖泊与环境国家重点实验室;中国科学院大学;
【基金】：国家自然科学基金项目(41373017,41576171)
【分类号】：X524

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