Sediment Organic Carbon Characteristics And Environmental Evolution Of Baiyangdian Lake In The Past 70 Years

Baiyangdian lake is the largest freshwater lake in North China,and its sediment plays an irreplaceable role in carbon sink.Affected by climate and the economic development around the basin in the last century,the ecological environment has been seriously damaged,and the process of organic carbon accumulation in the lake has been seriously affected.This question with the characteristics of baiyang lake area sediment organic carbon accumulation process to reveal the ecological environment evolution of nearly seventy years in the past,using column of core information combined with human activity history,discusses the external natural environment and human activities on the organic carbon humification process,clear over the years,the characteristics of the baiyangdian lake carbon sequestration process The results provide theoretical and data basis for predicting the future carbon accumulation process in Baiyangdian lake.The main conclusions are as follows:（1）Sedimentary characteristics of baiyang Lake characteristic area were studied by ²¹⁰Pb_ex and ¹³⁷Cs specific activity.The specific activity of ¹³⁷Cs had special time scales of 1963,1975 and 1986,and the average deposition rate calculated by ²¹⁰Pb_exwas 0.962 cm·a^-1.（2）The pH values of ZX1 and ZX2 ranged from 7.02 to 8.00 and 7.20 to 8.18.The grain size becomes fine from bottom to top,and the coarse silt component has the most grain size.TOC and TN contents showed a decreasing trend from top to bottom,with C/N values ranging from 11.65 to 15.34 and 10.61 to 18.37.（3）According to the source analysis of organic carbon,the main source of organic carbon in sediments is the lake,in which macroaquatic plants are the dominant,but the number of algae has increased significantly in recent years,and the contribution of exogenous sources to sediment organic carbon is relatively small.（4）The organic carbon components were obtained by continuous extraction:water-soluble organic carbon（WSOC）,pyrolytic organic carbon（THOC）,acidolytic organic carbon（HHOC）,alkali-soluble organic carbon（AHOC）and insoluble organic carbon（WISOC）,and the content characteristics were WISOC>AHOC>HHOC>THOC>WSOC.The humification degree of each organic carbon component was consistent with the change trend of molecular weight.WSOC and HHOC showed an increasing trend with the increase of depth,while THOC showed a decreasing trend with the increase of depth.AHOC first decreased and then increased from top to bottom.（5）According to the variation characteristics of various indicators in the paper,the succession history of ecological environment in the study area was reconstructed by combining the human historical activities in the study area.During 1953-1961,the level of primary productivity of the lake was low,the ecological environment was good,and the lake was in a state of natural evolution.During 1961-1983,water conservancy facilities were built in the upper reaches of the lake,and sediment grain size gradually became fine and nutrient content increased slowly,but the lake was in a healthy state.From 1983 to 2004,human activities increased significantly,a large amount of nutrients were imported,and the eutrophication level of water body increased.From 2004 to2015,industry and agriculture continued to develop,and lake eutrophication was severe,and lake productivity was at a high level.After 2015,the production level of Baiyangdian is still high,but the degree of eutrophication has eased,and the treatment of baiyangdian waters has achieved initial results.