The Source Of Organic Matter And Paleoenvironmental Implication Of Organic Matter Related Proxies Of Lake Surface Sediments Of Inner Mongilia Plateau And Its Adjacent Area,China

The Total Organic Carbon?TOC?,Total Nitrogen?TN?,carbon/nitrogen ratio?C/N?and organic carbon isotope(?¹³C)of surface sediment from 55 lakes of the Inner Mongolia Plateau and its adjacent area were measured,and its relationships with influencing variables were explored.Furthermore,the predominant source of organic matter was distinguished preliminarily.The main conclusions are as follow:?1?The content of Total Organic Carbon?TOC?in surface sediments of lakes from Inner Mongolia Plateau ranges from 0 to 11%.And the TOC contents are less than 3% in most lakes,reflecing the the low productivity of lakes in the Inner Mongolia Plateau.?2?The Carbon/Nitrogen ratio?C/N?of organic matter are generally low,ranging from 8 to 19.The organic carbon isotope(?¹³C)vary from-28 ‰ to-21 ‰,reflecting a mixed source of aquatic and terrestrial components with authentic fraction dominated.The terrestrial organic matter mainly comes from terrestrial C3 plants,and the lacustrine organic matter is from aquatic plants predominantly.?3?There was a significant negative correlation between ?¹³C and mean annual precipitation,which reflects the response of ?¹³C of lake sediment to terristrail vegetation and therefore the precipitation.That is,the influence of authengentic organic matter can be neligiable because that the authengentic organic matter of lake center surface sediments in the study area are mainly controlled by the submerged plant with similar ?¹³C value.Therefore,the ?¹³C of the lake center surface sediment are mainly controlled by terristrail organic matter.Hence,the vegattion pattern determine the change of ?¹³C.With change from C4 plant dominated desert to C3 plant dominated forest steppe,the ?¹³C changes to the negative.?4?The total organic carbon?TOC?content was significantly positively correlated with water depth,suggesting that the reducing environment,the less input of terristrial inorganic particles and the increasing adsorption might be responsible for dynamic.In addition,there were no significant correlation between Carbon to Nitrogen ratio?C/N?and lake basin scale varibles,indicating that C/N can not be used to reflect the chagne in lake basin scale.The characteristics of organic carbon isotope(?¹³C)are same as the Carbon to Nitrogen ratio?C/N?.