长江中游尺八湖现代沉积物营养元素富集的环境意义

MODERN SEDIMENTARY NUTRIENT ELEMENTS ENRICHMENT CHARACTERISTICS AND ITS ENVIRONMENTAL SIGNIFICANCE OF CHIBA LAKE IN THE MIDDLE YANGTZE RIVER, CHINA

通过基于^(210)Pb与环境事件分析相结合的定年方法,在建立沉积年代序列的基础上,对长江中游尺八湖CB-1孔现代沉积物营养元素(TOC、TN、TP)及C/N值进行分析,并结合尺八湖所在的监利县志有关记载,对沉积物营养元素富集与人口数据进行相关分析。结果表明:1尺八湖近70a来沉积物营养元素富集可分为2个主要阶段:上世纪80年代以前TOC、TN、TP值变化平稳,富集系数EF值反映营养元素富集尚在自然水平范围内;上世纪80年代以来TOC、TN、TP值呈显著上升,EF值反映营养元素的富集超越了自然水平。2尺八湖现代沉积物营养元素的变化与湖泊流域所在地区(监利县)人口数量呈显著相关关系,TP值与人口数量在突变点上相一致。3上世纪70年代末、80年代初以来,是尺八湖营养元素快速富集阶段,这当与该时间段人口增长、人类生产活动旺盛、农业种植中化肥使用量增加等因素具有密切关系。

High-resolution nutrient elements enrichment characteristics for modern lake sediments（last 50-100 years） are essential for quantitative paleoclimate research. CB-1 core（91cm） of Chiba Lake in Jingjiang section of the Yangtze River was selected for understanding the relations between nutrient elements enrichment characteristics and human activities.Dating of the 210 Pb, grain size and nutrient elements（TOC, TN, TP, C/N） were analyzed. Then environmental change events were found by the sedimentary characteristics of CB-1 core and the local historical data of study area. Furthemore,according to the results of correlation analysis between nutrient elements and demographic data, the following conclusions were drawn as follows.（1） The nutrient enrichment in the Chiba lake sediment can be divided into two main stages for nearly 70 years： before the 1980 s, the TOC, TN and TP values were very stable, the EF values reflected that the nutrient enrichment was within the natural level; since the 1980 s, the nutrient element concentrations increased significantly and the EF values reflected that the nutrient enrichment was beyond the natural level.（2） The variation of TOC and TN values in modern sediments in the Chiba lake was significantly correlated with demographic data in the area（Jianli County）,moreover, the value of TP and demographic data suddenly changed at the same time.（3） In the late 70 s and early 80 s of the twentieth century, nutrient elements in the Chiba lake were in rapid enrichment stage, which had a close relationship with the population growth, human activities and increased fertilizer use in Chinese agriculture during this period.