Exploration And Application Of Pollution Source Apportionment Method Based On Hydrochemical Characteristics And Fluorescent Fingerprint

Excessive pollutants were discharged with the development of urbanization and the intensification of human activities,which led to the aggravation of water eutrophication and the serious impact on water ecosystem.The water environment problems have become a global problem.Restraining the input of point source and non-point source pollution is the fundamental method to address water pollution problems.Hence,it is necessary to carry out the pollution source apportionment,that is,to qualitatively and quantitatively evaluate the contribution of point source?PS?and non-point source?NPS?pollution in order to provide basic data for water pollution control and clear control priorities.At present,the common methods for evaluating pollution sources have problems such as high test cost,difficulty,and large data demand.Moreover,most methods cannot quantitatively evaluate pollution sources,which caused certain difficulties in the pollution source apportionment.The Danjiangkou Reservoir and its main tributaries were selected as the study area.The spatiotemporal variation of water quality indicators,main ions and dissolved organic matter?DOM?were analyzed to clarify the water quality.This study regarded the result of pollution source apportionment using the isotope method as the standard,and explored how to use the hydrogeochemical characteristic analysis method and the DOM three-dimensional?3D?fluorescence spectrum characteristic analysis method to monitor the water quality simply and evaluate qualitatively and quantitatively PS and NPS pollution,which provided a reference for water pollution control and water environment management.The main conclusions of this thesis are as follows:?1?The water was weakly alkaline in this study area.In the tributaries,the concentrations of total nitrogen?TN?and nitrate?NO₃^--N?were highest in the dry season,total phosphorus Cl^-were lowest in the wet season,K⁺was highest in the dry-to-wet transition season,Si was reservoir area,the water quality indicators and main ion concentration were low and were no obvious seasonal change.?2?The DOM was decomposed into six components.C1 was a protein-like substance from wastewater.C2 and C3 were UVC and UVA humic-like substances from terrestrial sources,respectively.C4 and C6 were tryptophan-like substance and tyrosine-like substance derived from the decomposition of microorganisms,respectively.C5 was a tryptophan-like substance secreted by seasonal phytoplankton.The content of DOM was highest in Dinghe River and lowest in Sheweihe River for the whole year,and most watersheds had the lowest DOM content during the wet season.?3?The quantitative analysis method of characteristic ion/TN was established.Cl^-/TN,were selected as NPS pollution tracers.The contribution rate of NPS of TN was quantified concentration and discharge.For the dry,dry-to-wet transition,and wet seasons,the average contribution ratios of NPS of TN for the tributaries were 79%,83%,and 93%,respectively,and the average TN loads were 1419.2 t a^-1,696.6 t a^-1,and 2007.8 t a^-1,respectively.?4?The more humic-like substances,the greater the contribution of NPS pollution,and the more protein-like substances,the greater the contribution of PS pollution.The greater the Fluorescence index?FI?,the greater the contribution of PS pollution and the smaller the contribution of NPS pollution;the greater the specific UV absorbance value(SUVA₂₅₄),the greater the contribution of PS pollution.Moreover,FI,humification index?HIX?and Slope ratio?S_R?have a quantitative relationship with the nitrogen stable isotope(?¹⁵N)and oxygen stable isotope(?¹⁸O)of nitrate.Therefore,the source of pollution can be qualitatively and quantitatively analyzed by measuring the DOM three-dimensional fluorescence spectrum characteristics.?5?The establishment of linear relationships between the DOM three-dimensional fluorescence spectrum characteristics and water quality indicators and the concentrations of NPS pollutants have achieved the purpose of quantifying the pollutant load and the contribution rate of NPS pollution.