Study On DOM Composition Characteristics Of Qihulinhe River And Its Influence On Water Quality

Dissolved organic matter（DOM）is a class of substances widely present in the water environment,which is an active component in the water body,and its structure and source affect the physical and chemical properties of the water body.Studying the composition,source characteristics,and influence on water quality can provide a reference for the assessment of water environment quality.This thesis took three different types of river sections in the upper reaches of the Qihulinhe River in Heilongjiang Province as the research area,analyzed the physical and chemical properties of water,discussed the composition structure and source characteristics of DOM in watersheds,constructed the regression relationship between conventional water quality indicators and spectral indicators,and revealed the influence of DOM on water quality.The main conclusions are as follows:（1）COD and COD_Mn in the upper reaches of the Qihulinhe River could not stably meet Class III environmental quality standards for surface water in GB 3838-2002during the spring and summer flood periods,and the remaining indicators showed good water quality.After flowing through the human activity area,the concentration of NH₃-N and TP increased significantly.The water quality indicators of different section types were significantly different,and the water quality in the river was better than that of Yunshan Reservoir.（2）The DOM concentration of water bodies in the spring and summer flood periods in the river was significantly higher than that in other seasons,the aromatic carbon content of DOM in water bodies was higher,and the characteristics of terrestrial sources were significant.Different section types and seasons had different spectra characteristics,the terrestrial source characteristics of the river sections above and below the reservoir were stronger,the proportion of endogenous DOM in the reservoir section was higher,the terrestrial source characteristics were significantly stronger in the spring and summer flood periods,and the endogenous characteristics were the strongest in winter.（3）The results of soil DOM extract analysis showed that the soil DOM content in the surface layer was higher,and the aromatization and humification were stronger.As the depth increases,the DOM gradually decomposed macromolecular matter under the action of microorganisms.Freeze-thaw simulation experiments showed that plant litter was the main source of soil DOM,and eventually migrated to the water body,forming the natural background value of the water DOM.（4）According to the principal component and regression analysis of the spectral index of the water body of the Qihulinhe River,the main source of the DOM of the water body was the terrestrial DOM represented by the first principal component.In terms of time,the regression model of the reservoir with high forest coverage in space had a better prediction effect during the spring and summer flood periods,which further proved that the proportion of terrestrial DOM in the water body of the Qihulinhe River was high,and the section of the reservoir in the spring and summer flood periods was seriously affected by the background value of organic matter.