Research On Spectral Characteristics And Detection Method Of Fluorescent Ogranic Contaminants In Seawater Using Three-Dimensional Fluorescence Spectroscopy

Fluorescent dissolved organic matter is a kind of important substance in the ocean,playing an irreplaceable role in the process of material conversion and energy cycle in the ecological environment.Studying their composition and properties is very conducive to understanding the biochemical processes of the Earth and controlling water pollution.Fluorescent dissolved organic matter has special optical properties,which can produce a fluorescent response when irradiated with incident light.This property can be used to analyze and study the matter.Because of its high detection efficiency and good selectivity,three-dimensional fluorescence spectroscopy has been widely used in the field of water quality detection in recent years.At the same time,it has good results in qualitative discrimination and quantitative prediction models.This thesis discusses the composition and sources of organic matter in Zhoushan and Tianjin sea areas in combination with the project of National Natural Science Foundation analyzes the spectral characteristics of typical organic substances,namely tryptophan and tyrosine in seawater and their fluorescence characteristic peaks and concentrations,It also has established a quantitative analysis model of soluble fulvic acid and total organic carbon in humus.The main work and innovation points of the paper are as follows:(1)The application of three-dimensional fluorescence spectroscopy in analyzing the composition of fluorescent organic compounds in seawater is studied.By taking seawater samples as research objects,collecting fluorescence spectrum data,using the Delaunay triangle interpolation method to correct the scattering region in the spectrum,decomposing the samples through the PARAFAC model,the fluorescent components of the sample are obtained.According to the fluorescent characteristic peak information in each component,the components of the fluorescent substance in the sample can be analyzed.From the experimental results,it can be seen that the fluorescent organic matter in the seawater sample mainly includes two types of substances,which are protein-like and humus-like substance.(2)Aiming at the protein-like substances in seawater,the typical substances tryptophan and tyrosine were selected as the research objects,and we studied their spectral characteristics under high concentration and the relationship between the fluorescence peak intensity and the concentration.First,the spectral data of tryptophan and tyrosine were obtained through experiments.The smoothing method of SG was used to eliminate the interference of random noise on the spectrum.The alternating trilinear decomposition(ATLD)algorithm was used to extract the spectral characteristics.The fluorescence intensity of the respective fluorescence peaks changes with the concentration.The experimental results show that the fluorescence quenching will occur when the concentration of tryptophan and tyrosine are around 15mg/L and 20mg/L.(3)Aiming at the humic substance with high carbon content in seawater,taking the important part of fulvic acid as the research object,the quantitative relationship between the fulvic acid’s fluorescence characteristics and the total organic carbon(TOC)content was studied;(FRI)and Gradient Lifting Decision Tree(GBDT)combined quantitative model to predict the total organic carbon(TOC)content of fulvic acid.By comparing with the analysis results of multi-line linear regression,it is found that the GBDT model can reduce the prediction error well,and has better discrimination effect.For the fluorescent dissolved organic matter in seawater,this thesis first studied the types of organic matter in the coastal areas of Zhoushan and Tianjin,next analyzed the spectral characteristics,the influence brought by solution concentration to the fluorescence intensity and the relation with the water quality index.Our work provides a further understanding of the properties of some important organic substances in seawater and meanwhile verifies the feasibility and effectiveness of the application of three-dimensional fluorescence spectroscopy in water quality detection.