Spatial Distribution Characteristics And Source Analysis Of Organic Matter In Surface Sediments Of Chenghai Lake

Lake is an important part of terrestrial ecosystem,and it is also an effective information collection of lake basin.With the development of social economy and human society on the lakes interference activities,a large number of lakes under severe major issues,such as ecosystem degradation,serious eutrophication for lake water body,lake area shrink as well as the reduction in flood storage capacity in the lake,the existence of these problems seriously restrict the sustainable development of ecological economy in the basin.Surface sediment is an effective carrier to record lake information.The study of surface sediment can not only effectively understand the hydrological characteristics and sedimentary environment of the lake and the basin itself,but also reflect the current ecological environment of the lake as well as the nutrient status and pollution level of the lake water.Therefore,35 surface samples from Chenghai Lake,Yunnan province were collected in this paper.By using organic carbon,nitrogen and their stable isotopes,as well as water quality parameter characteristics of chenghai and sediment grain size and other indicators,spatial distribution characteristics and sources of organic matter of Chenghai surface sediments were discussed,and the following conclusions were drawn:?1?The experimental results showed that the total organic carbon?TOC?in Chenghai surface sediments ranged from 0.724%to 5.559%,(7.24⁵5.59mg·g^-1),with an average value of 31.24mg·g^-1.TN content ranged from 0.883‰to 5.966‰,(0.88⁵.97mg·g^-1),with an average value of 3.27mg·g-1.Compared with previous research results,TOC content increased by 11.65%and TN content increased by37%.There is a significant correlation between TOC content and TN content,and the relationship between the two indicates that the spatial distribution of TOC is controlled by TN.It indicates that the primary productivity of Chenghai lake is improved and the eutrophication of lake is intensified.?2?The C/N ratio?C/N?of Chenghai Lake surface sediments is between7.147¹3.821,with an average value of 9.506,with a large change range.The surface sediments in different lake regions have different C/N ratios.?3?The carbon isotope value of the organic matter(?¹³C_org)is between-29.402‰²3.775‰,and the average value is-26.6‰,with a small change range.¹⁵N is between 2.33 4.817 and 3.731.In addition,there is a significant negative correlation between ¹³C and the corresponding depth and TN content,while there is a significant positive correlation between ¹⁵N and the corresponding depth and TN content.?4?Based on the comprehensive analysis of C/N ratio and organic carbon isotope(¹³C_org),it is found that the organic matter sources in the surface sediments of Chenghai in Yunnan province mainly belong to the category of aquatic plants and algae,which is a mixture of submerged plants,floating plants and algae.In addition,human life and agricultural activities in chenghai have a negative impact on eutrophication in Chenghai,and the change of delta ¹⁵N is to some extent affected by agricultural fertilizer and industrial activities in Chenghai river basin.