Molecular characterization of organic matters in complex matrixes is a challenge in environmental and analytical researches for a long time.The organic composition of the matrixes is extremely complex in regard to the existence of tens of thousands of chemical species and a broad distribution of physicochemical properties.Traditional techniques such as chromatographic separation coupling mass spectrometry(MS)are insufficient for molecular characterization of organic matters in complex matrixes due to the inherent low-resolution defects of the equipments.With the advance of mass spectrometry,high resolution mass spectrometry(HRMS)are gradually gaining popularities and applications in many scientific fields.Molecular characterization of organic matters in complex matrixes,screening and identification of emerging organic pollutants,and exploring the changing patterns of organic composition and molecular structures during environmental migration and transformation have become research hotspots in environmental science.By applications of the ultrahigh resolution Fourier transform ion cyclotron resonance mass spectrometry(FT-ICR MS),comprehensive molecular characterization methods for organic matters based on accurate masses and fine isotopic structures were developed and validated.Further researches were carried out on the molecular composition of organics in complex matrixes(i.e.,surface treatment agents,surface waters,and atmospheric aerosols)and molecular feature changes in environmental processes(i.e.,oxidation,photodegradation,and cloud treatment).The main contents of this dissertation are summarized as follows:In the first part,the classifications,environmental fates and behaviors,as well as classic analytical methods of organic matters in complex matrixes are introduced.The focus is on the MS methods and sample pre-treatment techniques.In addition,the principle of ultrahigh resolution FT-ICR MS and its applications are highlights.And the main contents,innovations and scientific significances of this research are outlined.In the second part,a qualitative and quantitative detection method for the determination of polyfluoroalkylsilanes(PFASis)in anti-fingerprint(AF)liquid products was established based on ultrahigh resolution FT-ICR MS combined with ultrahigh performance liquid chromatography coupling triple quadrupole MS(UPLC-QqQ MS).The occurrence of PFASis and studies on their degradation potentials in the environment as precursors of perfluoroalkyl carboxylic acids(PFCAs)were reported.Based on the CF2-scaled Kendrick Mass Defect(CF2-KMD)analysis in conjunction with isotope fine structure elucidation,the occurrence of 8:2 polyfluoroalkyl trimethoxysilane(8:2 PTrMeOSi),8:2 polyfluoroalkyl triethoxysilane(8:2 PTrEtOSi),as well as their cationic adducts,solvent substitutions,and other compound analogues,were successfully identified in commercial AF liquid products.In both the-OH-based total oxidizable precursor assay(TOP Assay)and the simulated photodegradation experiment,differential molar yields and carbon-chain lengths(C4-Cn+1)of PFCAs were observed depended on varied structures of PFASis.Conversion intermediates like 8:2 fluorotelomer carboxylic acid(8:2 FTCA)and 8:2 fluorotelomer unsaturated carboxylic acid(8:2 FTUCA)were detected simultaneously.This reserch is of great significance for identifying per-and polyfluoroalkyl substances(PFASs)and their precursors,discovering new transformation pathways and sources of exposure to PFCAs in the environment,and assessing the potential health risks of fluorinated products.In the third part,the specific molecular composition and properties of dissolved organic matters(DOM),and the effects of silver sulfide nanoparticles(Ag2SNPs)with photocatalytic activity on the photochemical reaction efficiency of the DOM under simulated sunlight irradiation were evaluated using ultrahigh resolution FT-ICR MS.And the changes of DOM composition and molecular characteristics during photochemical processes were further analyzed at the molecular level.Under direct sunlight irradiation,photochemical reactions promoted the photolytic elimination of higher unsaturated compounds in the DOM and favored the photooxidative generation of high oxygen content compounds,which were characterized in molecular terms by decreasing MWw,H/Cw and DBEw values,and increasing O/Cw and(OSC)W values.The presence of Ag2SNPs significantly reduced the TOC contents of samples(ATOC>-0.7 mg/L),and increased the numbers and overall proportion of newly generated compounds(n=235,5%),indicating that Ag2SNPs could enhance the photochemical degradation process of DOM.In addition,the results of CO2-scaled KMD(CO2-KMD)analysis showed that homoseries with different degrees of carboxylation(e.g.,polycarboxylic acids)were prevalent in the DOM.The addition of Ag2SNPs promoted the oxidation of active groups in the DOM molecular structures to form oxygen-containing functional groups such as carboxyl groups,which was more pronounced in high-MW region.While in the low-MW region,the carboxyl compounds were mainly degraded and mineralized by decarboxylation under sunlight irradiation.The results suggested that the presence of Ag2SNPs in the environment could accelerate the photochemical carboxylation and decarboxylation degradation behavior of DOM in natural surface waters,which might have important implications for the environment and climate change,and contribute to a better understanding the biogeochemical cycle of organic carbon.In the fourth section,the biogenic characteristics and potential formation pathways of nitrogenous compounds(CHON)in atmospheric organic matters(AOM),and the influence of cloud processing on the molecular characteristics of CHON were investigated by means of ultrahigh resolution FT-ICR MS.In this study,cloud water samples from a representative cloud process event and corresponding aerosol samples from pre-cloud,in-cloud and post-cloud stages were collected.Based on the established biogenic maker identification method,it was found that approximately 54%of formulas corresponding to 74%of the instrumental response(IR)for CHO were identical to the laboratory-imitated secondary organic aerosols(SOA)in smog chambers by ozonolysis reactions of isoprene,monoterpene(i.e.,a-pinene,d-limonene)and sesquiterpene(i.e.,β-caryophyllene).The strategy of reverse derivation precursors of CHON revealed that approximately 30%of atmospheric CHON might be formed from biogenic volatile organic compounds(BVOCs)ozonolysis precursors through the carbonyl-NH3/NH4’/amine or acid-base reaction channels.Comparison of non-cloud and in-cloud samples revealed that cloud processing significantly altered the molecular-level characteristics of CHON,promoted the elimination of unsaturated polycyclic N-aromatics and the transformation of poly-nitrogenous compounds(e.g.,CHON4 subgroup)to produce relatively saturated olefins or aliphatic nitrogenous compounds and low nitrogenous compounds(e.g.,CHONi,CHON2 subgroups)involving complex cloud chemistry.This study gives insight into the atmospheric evolution of CHON,and evaluates and dissects the impact of cloud processing on AOM.In summary,molecular-level characterization and identification methods for AF liquid products,DOM,and AOM were develoved based on ultrahigh resolution FT-ICR MS.Meanwhile,the degradation potential of PFASis as precursors of PFCAs in the environment was evaluated.Then,the photodegradation behaviors of DOM were investigated.Next,the source contributions,possible formation pathways of atmospheric CHON,and the influence of cloud processing on CHON were explored.Finally,the results reveal that FT-ICR MS owing ultrahigh mass resolution and accuracy is a powerful tool for the molecular characterization of organics in complex matrix samples.The outcomes of this research provide methodological references for the molecular-level characterization of complex component organic compounds,and for the identification and discovery of emerging environmental organic contaminants,as well as for exploring the changing patterns of organics during environmental migration and transformation. |