| As a major link of two carbon pools, the land and the sea, the river carbon cycle plays an important role in the global carbon cycle. The export and cycle processes of the riverine carbon are closely related to coastal zone environment, dynamics of the ocean carbon pool and the global climate system. Characteristics of the river carbon transport not only reflect the natural processes and the impacts of human activities on the rivers, the history and current status of the basin, but also have important impacts on the deposition and environment of coastal waters. So change of properties and organic carbon flux of river is one of the important research contents of the riverine carbon cycle, it is very important to understand river carbon cycle correctly.In this paper, concentrations of dissolved organic carbon (DOC) were measured monthly over a12-month period from March2013to February2014at the Jiaozhou section of Dagu River by choosing7monitoring sections. At the same time, discussed the temporal and spatial distribution characteristics of DOC in Dagu River, analyzed its influence factors, estimated the flux of DOC and compared with other rivers in the world by combining with synchronous observation data of hydrological elements. The main conclusions are as follows:(1) The law of spatial distribution of DOC was studied. The results indicated that the change of DOC content in different sites between1.32mg/L and12.56mg/L. In these7monitoring sections, the maximum value of DOC content appeared at the first sampling site in Taoyuan river area near G204, and the minimum value appeared at the third sampling site in Rubber Dam of Dagu River or the second sampling site G204near Dagu River. Analysis shows that the spatial variation of DOC not only associated with the source of DOC, but also related with the river flow, the soil and the change of vegetation, the different land use patterns of Dagu river also affect the distribution of DOC content in space.(2) The monthly change of DOC content in Dagu River was studied. The results found that the DOC content in Dagu River change with the river flow. From the whole study period, there is a certain relationship between the DOC content and the river flow, but did not show a synchronization to increase or decrease with the river flow. The Dagu river water flow are difference in each month, and the DOC content changes with the flow changes. It mainly because that the surface runoff of catchment rainfall on the formation of DOC in soil leaching efficiency was related to river flow changes. The average DOC content of Dagu River is5.14mg/L, slightly lower than the average DOC content of main rivers in the world (about5.75mg/L). (3) The DOC in different rivers obviously exist differences between regional and inter basin in flux and properties respect. The output DOC flux of Dagu river in a whole hydrological year is about1.6×105gC/km2/yr, which is significantly lower than average DOC flux that of most rivers, about2.04×106gC/km2/yr. The Dagu river DOC export flux in summer accounted for about90%of the annual total output. The Dagu River rainfall mainly concentrate in summer, and the water flow of the river accounts for about95%of the total. It is because of the river flow is the main reason for the DOC output flux, so the DOC flux in Dagu River is mainly concentrated in summer. |
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