Spatiotemporal Variation Of Dissloved Inorganic Carbon In Middle And Lower Reaches Of Lancang River:Related To Water Environment

Climate change had become a global environmental problem and attracted wide attention and concern.The global carbon cycle is playing an important role in it.The dissolved inorganic carbon(DIC)is an important component of river carbon flux.The paper selected the middle and lower reaches of the Lancang River in and confirmed twelve sampling points of the main stream in Yunnan Province and four points of the main tributary,than sampled water and measured content of DIC during 2016.Combined with other data of each section,we analyzed the spatio-temporal distribution characteristics of DIC in different sections of Lancang River and the relation with river environment factors.Finally we could discuss the interaction of river environment and carbon content and indicate the carbon geochemical process of river-reservoir.The results showed that:(1)The DIC content:The content of DIC in the middle and lower reaches of the Lancang River varied from 1.1840 mmol/L to 3.1440 mmol/L,and the mean value was 2.2155 mmol/L.From the point of view of time,the content of DIC in the Lancang River Basin in dry season(spring,autumn and winter)is higher than in rainy season(sunmmer).From the point of view of space,the DIC content in the middle and lower reaches of the Lancang River is decreasing from north to south,and the content of DIC before the dam is lower than that under the dam.Compared with other similar rivers,the range of DIC content in the middle and lower reaches of the Lancang River is at a normal level.The Lake Effect of the Lancang River is not obvious,and the DIC content before the dam is slightly stratified.(2)Influence factors:According to the water temperature,pH,turbidity,conductivity data of the Lancang River,water temperature is on the gradual increase from north to south,pH value is on the other hand,turbidity and conductivity have obvious seasonal changes.After the correlation analysis of those factors and DIC content,we could know that water temperature,conductivity and turbidity are important factors affecting the DIC content of water,then the influence of pH value and oxidation and reduction potential on the DIC content of water is relatively small.In addition,Interception of dam,biological action of aquatic organisms,release and absorption of CO2,precipitation and dissolution of calcium carbonate,input of tributary and exogenous things would have an impact on DIC.Some natural factors such as watershed terrain,geological conditions,climate change will have a certain impact on the DIC content.The reservoir age and the content of DIC have a certain correlation,as well as the reservoir operation time.