Development And Application Of High-resolution Mass Spectrometry Analytical Method And Programs Of Dissolved Organic Matter In Groundwater And Molecular Level Analyzing Programs

Dissolved organic matter（DOM）is an important composition in groundwater.The composition of DOM in groundwater is very complex and affected by the biogeochemical environment and human behavior in the region,and it affects the occurrence of metal ions,the transformation of pollutants and other chemical activities in the water.However,due to its complexity,molecular level analyst of DOM is still a research hotspot.In this paper,the accurate m/z data of DOM in groundwater was obtained by auto-solid phase extract（auto-SPE）,ultra-performance liquid chromatography（UPLC）and Q-Orbitrap high-resolution mass spectrometry（HRMS）technology,and,combining with chemometrics algorithm,a fine molecular characterization program system of DOM was established.And it was then applied to the research on the molecular characteristics of groundwater DOM in typical areas.The main research results are as follows:An analytical method using Bond Elut PPL SPE column to enrich DOM in groundwater,Kinetex Polar C₁₈ UPLC column for separation,electrospray ionization source（ESI）and Q-Orbitrap HRMS to detect the accurate molecular mass of DOM was established.The Bray-Curtis（B-C）dissimilarity between the spiked samples and the standard samples was 23.24%～38.48%;the intraday B-C dissimilarity of the matrix spiked samples was 17.98%～33.04%;the interday B-C dissimilarity was between 19.72%and 39.08%.The sensitive,accurate and stable detection of DOM in groundwater was realized.By establishing a DOM target molecule seed library,restricting the values of carbon-hydrogen ratio,carbon-oxygen ratio and unsaturation,the m/z and the molecular formula were matched.After ruling out the background response,a variety of statistics based on substance concentration were determined.A fast,high-throughput,and automated fine characterization system of DOM was designed and established.The system can simultaneously output four kinds of molecular maps including Van Krevelen map and Kendrick Mass Deviation（KMD）map,realizing multi-angle,three-dimensional visual characterization of molecular composition.The analytical method and the characterization program were applied to 41 groundwater samples from Heilongjiang and Hebei provinces.The overall concentration of DOM in groundwater in Daxinganling area is significantly higher.The distribution characteristics of molecular species and concentration are very similar,with high plant-derived DOM up to 40%,except two abnormal samples from Hongwei Town.The molecular characteristic of samples in Hebei Province shows no uniform feature,and the overall concentration of DOM is significantly lower.The reason for this phenomenon may be related to the differences in DOM sources,land use patterns and human activities between the two areas.