| , As an important part of the urban ecosystem urban rivers is essential to the city’secological system. In this thesis, a typical urban river-Baitabuhe River in the northeastof China was selected for study. The nutrients’ space distribution features of itsoverlying water, pore water and sediment were analyzed. The diffusion flux betweensediment and water interface of N and P was calculated, and their correlation inoverlying water and pore water analyzed. The3D-fluorescence spectroscopy andUV-visible absorption spectra to represent the composition, source, structure andhumification degree of the dissolved organic matter (DOM) in the overlying water andpore water was used, The distribution characteristics of the sediment nutrient andcarbon-nitrogen-phosphorus coupling relationship were analyzed.The study reached the following conclusions:(1) In overlying water and pore water, the concentration of nitrogen in the river isthe lowest in the rural region, followed by the town region and the urban region, so isphosphorus. It is considered that the nutrients in the rural region came from the ruralgrey water and non-point source pollution, in the town region from the domestic sewageand industrial drainage, and in the urban region from the industrial wastewater and thedomestic sewage. The concentrations of the nutrients in the pore water are higher thanthose in the overlying water. The spatial distribution of the nutrients in the surface wateris similar to that of the pore water. The average diffusion flux across sediment-waterinterface is0.429μmol/(m2d) for NH3-N,0.134μmol/(m2d) for NO2--N,0.080μmol/(m2d) for NO3--N, and0.143μmol/(m2d) for PO43--P. The results show thatsediment is one of the important input sources of nitrogen and phosphorus. The concentration of ammonia nitrogen in sediment pore water has a significant correlationwith overlying water; the concentration of phosphate also has a significant correlationwith overlying water; but the concentration of nitrite nitrogen between pore water andoverlying water is not high; the nitrate nitrogen is lower. It shows that the nitrogen ofpore water mainly diffuses ammonium to the overlying water; and the phosphorus ofpore water mainly diffuses phosphate to the overlying water. The average compositeindex of eutrophication is66.12, water quality is moderate eutrophication, and theeutrophication degree gradually increases from upstream to downstream.(2) Using3D-fluorescence spectral characteristics to analyze the organic matter inthe overlying water and sediment pore water, we found that the organic matter can bedivided into five components: tyrosine, tryptophan, fulvic acid, humic acid andmicrobial metabolites. Tyrosine has the largest share in Baitabuhe River overlyingwater and pore water organics, humic acid has the least. But in the pore water DOM,fulvic acid and humic acid proportion significantly increased, indicating that the organicmatter in sediments may diffuse to the pore water, that results to acid and humic acid inpore water are higher than the overlying water. SPSS was used to analyze thecomponent concentration of organic matter in five systematic clusters. Results showthat32sampling points can be divided into three groups, coinciding with the rural area,the town area and the urban area.32water samples were collected from mainstream ofthe river, and DOM UV spectra of sediment pore water and comprehensively analyzed,from which nine indices ((SUVA254、E2/E4、E4/E6、E2/E3、S275-295、S350-400、A2/A1、A3/A1and A3/A2) were deduced. These indices could indicate structural compositionsand assess humification level of DOM. Humification level of DOM in the rural region isdifferent from the urban region, and it is obviously higher in the urban region than thatin the rural region. A2/A1、A3/A1and A3/A2show negative correlations with other indices,indicating that humification degree increase with the rise of A2/A1、A3/A1and A3/A2,while decrease with the rise of other indices. Moreover A2/A1、A3/A1and A3/A2areaccuracy indices to completely assess humification level of DOM and discriminatehumification process of the samples.(3)The average of total nitrogen content in sediments of Baitabuhe River is3.86g/kg; total phosphorus content is0.56g/kg; organic matter content is4.85%. Total nitrogen, total phosphorus and organic matter basically has the same trends, which aregradually increased from the upstream to the downstream; sediment carbon-nitrogen-phosphorus coupling relations and environmental significance of the study results showthat: TOC/TN reflects the source of organic matter may be endogenous inputs, and hassignificant positive correlation. The average of TOC/TP is46.93, the value of TOC/TPwas lower in upstream and downstream, the midstream is higher; the average of N/P is5.79, downstream of the N/P is higher, indicating that the eutrophication status isincreasing along the flow direction. |
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