Temporal And Spatial Distributions Of River Carbon And Impact Of Land Cover In The Headwater Region Of The Yellow River

River carbon cycle is the key content of global carbon cycle,climate change and evolution of watershed ecological environment.This study systematically monitored and sampled rivers in different land cover types?glacier,permafrost,wet and grass?in the Yellow River source area in April,June,August and October 2016,and dissolved organic carbon?DOC?,dissolved inorganic carbon?DIC?,particulate organic carbon?POC?,stable carbon isotope and other basic geochemical indicators were measured in the field and indoors,using a variety of methods for comprehensive analysis.The results showed that the DOC content of river water in the headwater region of the Yellow River was between 0.2-12.2 mg/L,with an average of 4.7±2.7 mg/L,which showed seasonal variation characteristics from April>August>June>October,and Spatial variation characteristics from wetland>permafrost>grassland>glacier;POC contents are between0.14-81.13 mg/L,showing seasonal changes from August>June>October>April,and the spatial variation characteristics from glacier>wetland>grassland>permafrost,the?¹³C value of POC ranged from-27.7‰to-6.25‰,with an average of-23.18±2.01‰;the DIC contents was between 0.86-1.98mmol/L,with an average of 1.36±0.38mmol/L,and its?¹³C value is between-9.85‰and-2.87‰,with an average of-6.55±1.90‰.The organic carbon in the river source area of the Yellow River mainly comes from the land source input,and it is easy to oxidize and decompose after entering the water body,especially in the glacier and permafrost area.River DIC sources and their?¹³C may be significantly affected by atmospheric CO₂ intrusion.The carbon pool in the source area of the Yellow River has a high carbon content and is sensitive to temperature and precipitation.However,the proportion of carbon transported by rivers is not the same.Among them,the glacier is mainly lost in POC,and permafrost is mainly dominated by DOC loss.The proportion of DOC and POC loss in wetland is similar.This study is of great significance for understanding the mechanism of watershed carbon cycle in the context of global change,and provides a scientific basis for ecological environment protection and governance in the headwater of the Yellow River.