Spatial And Temporal Distribution And Source Analysis Of Dissolved Organic Matter In A Inland Typical Small Watershed Of Northwest China

Dissolved organic matter(DOM)plays an extremely important role in the global carbon cycle and is closely related to important links in the ecosystem.Because of its active environmental role,it has an important impact on the terrestrial and aquatic ecosystem environment.In order to further systematically study the environmental impact characteristics of DOM in the inland northwest watershed,the typical small watershed of the inland northwest as the research object,the spatial and temporal distribution laws and sources of DOM in the small watershed were analyzed.By using three-dimensional fluorescence spectrum analysis technology and parallel factor analysis(PARAFAC)method,the temporal and spatial migration and transformation rules of DOM in P River and T River in northwest small watershed were studied,and the influence of P River confluence on the main stream DOM fluorescence spectrum characteristics was analyzed.The composition and spectral characteristics of soil DOM under different land use and vegetation sparsity in the watershed were studied.Through correlation analysis,the correlation between DOM of water body and conventional pollution indexes was made clear.The results show that:(1)Despreading the surface water samples of P and T rivers in summer and autumn revealed that the two rivers identified three types of fluorescence peaks,namely humus-like fluorescence peaks(A,C peaks)and protein-like fluorescence peaks(T peak).There were two types of fluorescent components in P River,namely fulvic acid-like component C1 and tryptophan like component C2.In T River,besides C1 and C2,there were humic acid-like component C3.(2)The DOM concentration change in the two rivers had a significant seasonal variation.By using fluorescence parameters to analyze the source of the P and T rivers,the source of DOM was the common action of both land and internal sources.Correlation analysis between DOM fluorescent components and conventional physical and chemical indicators showed that the sources of fluorescent components were homologous,and the tryptophan-like components in P DOM were closely related to the migration and transformation of N and P elements,and the composition was closely related to the phosphorus-containing substance.(3)The water body at the intersection would have a certain impact on the river DOM.The three-dimensional fluorescence spectrum analysis technology was used to identify the main presence of humus-like fluorescence peaks(A and C peaks)and protein-like fluorescence peaks(T and D peaks).Due to the mixing effect of the water flow,the fluorescence intensity of the A,C,T peaks of the water samples at the intersection was weakened.All the fluorescence parameters indicated that there were many anthropogenic sources in the main stream,and the flow at the confluence contributes to the DOM spectral characteristics and sources of the main stream,but it was not the dominant factor.(4)The soil DOM of different land types mainly includes peak A and peak C,and the intensity of the fluorescence peak had certain differences under the degree of density and density of different utilization types of soil and vegetation.PARAFAC identified the presence of humic acid fluorescent component C1 and fulvic acid fluorescent component C2 in different utilization types of soil.At the same time,the fluorescence parameters showed that the DOM sources of different land-use soils had both human activities and internal microbial activities.