Transform Ion Cyclotron Resonance Mass Research Articles

Two-Dimensional Fourier Transform Ion Cyclotron Resonance Mass Spectrometry of N-Linked Glycopeptides.

Glycosylation is a common modification across living organisms and plays a central role in understanding biological systems and disease. Our ability to probe the gylcome has grown exponentially in the past several decades. However, further improvements to the analytical toolbox available to researchers would allow for increased capabilities to probe structure and function of biological systems and to improve disease treatment. This article applies the developing technique of two-dimensional Fourier transform ion cyclotron resonance mass spectrometry to a glycoproteomic workflow for the standard glycoproteins coral tree lectin (CTL) and bovine ribonuclease B (BRB) to demonstrate its feasibility as a tool for glycoproteomic workflows. 2D infrared multiphoton dissociation and electron capture dissociation spectra of CTL reveal comparable structural information to their 1D counterparts, confirming the site of glycosylation and monosaccharide composition of the glycan. Spectra collected in 2D of BRB reveal correlation lines of fragment ion scans and vertical precursor ion scans for data collected using infrared multiphoton dissociation and diagonal cleavage lines for data collected by electron capture dissociation. The use of similar techniques for glycoproteomic analysis may prove valuable in instances where chromatographic separation is undesirable or quadrupole isolation is insufficient.

Novel use of the electrocatalytic oxidation process with Fe-DSA dual anode configuration for leachate treatment: Significance of in situ ferrate generation

The leachate produced by waste transfer stations (WTSs) contains substantial amounts of refractory organic matter and ammonia, necessitating on-site treatment. In this study, a novel electrocatalytic oxidation (ECO) process with Fe-DSA dual anode configuration was established for leachate pretreatment. In this configuration, chloride in the leachate was converted to active chlorine by the DSA anode, while ferric hydroxide (Fe(OH)3) was produced from Fe anode. As a result, Fe (VI) was in situ formed through the reactions between active chlorine and Fe(OH)3. Simultaneous and efficient removal of COD and NH4+-N in the ECO process with Fe-DSA dual anode configuration was achieved, significantly improving leachate biodegradability compared with the Fe–Fe and DSA-DSA dual anode configurations. The transformation characteristics of organic compounds in the ECO process were investigated through the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) analysis. The ECO process with Fe-DSA dual anode configuration promoted the removal and transformation of lignins/carboxylic rich alicyclic molecules (CRAM)-like and tannins compounds with biologically refractory properties, as well as S-containing compounds with biological toxicity. Further X-ray photoelectron spectroscopy (XPS) analysis revealed that iron oxides, amorphous Fe-(oxy) hydroxide, and amorphous Fe(OH)3 produced by Fe (VI) decomposition in the ECO process with Fe-DSA dual anode configuration enhanced removal performance through coagulation. In addition, the contribution of different active species to organic matter removal in the ECO process was quantified by quenching experiments. High-valent iron oxidation dominated the ECO process with Fe-DSA dual anode configuration, while active chlorine oxidation, •OH oxidation and coagulation synergistically contributed to organic matter removal.

Ranking the oil contribution of individual layers in a lacustrine shale oil system based on non-hydrocarbon analysis by FT-ICR MS

Identifying the dominating oil-producing layer(s) within a shaly system, typically characterized by multiple layers with similar properties, is always a critical yet formidable task, as the oil component disparities among these closely adjacent layers are too minor to be resolved by the traditional geochemical fingerprints. This challenge is now likely addressed by high-resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), which can resolve thousands of non-hydrocarbons that could serve as new fingerprints. Taking a typical shaly system in the Ordos Basin in China as an example, the specific proportions of non-hydrocarbon compounds from the retained petroleum of different source rock layers (rock extracts) and the produced oil at the wellhead were identified by FT-ICR MS. Their compositional similarity was calculated using a multidimensional scaling (MDS) method, and the layers hosting the retained petroleum with higher compositional similarity to the produced oils are considered to be the main contributors to oil production. The results show that the main producing layers identified by FT-ICR MS differ from those proposed based on traditional fingerprints like the Rock-Eval parameters. A typical example is that the thick low-TOC shales, conventionally proposed to be unessential to oil production, seem to have a similar contribution, if not higher, to their thick silty counterparts. This divergence may be attributed to the fact that the conventional fingerprints primarily rely on the rock extracts from a vertical well section, which may only represent a limited lateral area, while the non-hydrocarbon similarity approach involving the produced oil appears to be more realistic, as it can consider the engineering processes, like the horizontal well track and the hydraulic fracturing effects. The current approach provides a novel route for identifying the dominating producing layer(s) in a shale oil system, which may have extensive potential for optimizing the production strategy of shale oil wells.

High throughput identification of carbonyl compounds in natural organic matter by directional derivatization combined with ultra-high resolution mass spectrometry

Carbonyl compounds are important components of natural organic matter (NOM) with high reactivity, so that play a pivotal role in the dynamic transformation of NOM. However, due to the lack of effective analytical methods, our understanding on the molecular composition of these carbonyl compounds is still limited. Here, we developed a high-throughput screening method to detect carbonyl molecules in complex NOM samples by combining chemical derivatization with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR-MS). In six different types of dissolved organic matter (DOM) samples tested in this study, 20%-30% of detected molecules contained at least one carbonyl group, with relative abundance accounted for 45% to 70%. These carbonyl molecules displayed lower unsaturation level, lower molecular weight, and higher oxidation degree compared to non-carbonyl molecules. More importantly, the measured abundances of carbonyl molecules were consistent with the results of 13C nuclear magnetic resonance (NMR) analysis. Based on this method, we found that carbonyl molecules can be produced at DOM-ferrihydrite interface, thus playing a role in shaping the molecular diversity of DOM. This method has broad application prospects in screening carbonyl compounds from complex mixtures, and the same strategy can be used to directional identification of molecules with other functional groups as well.

Mechanistic insights of efficient aromatic organic compounds oxidation using biochar derived from coking wastewater sludge

Coking wastewater sludge possessed potential environmental hazards and pyrolysis was a desirable approach which could converted it into one functional carbonous material. The sludge-based biochar (SC-N3) originated from the feedstock of sludge from the regenerated water treatment had various iron-containing species and exhibited the effective catalytic ability. Compared with the degradation of the four pollutants (i.e., phenol, pyridine, quinoline and indole) alone, the mixed of the four pollutants in simulated coking wastewater exhibited a prominent different degradation trend, where the removal rates of indole and quinoline were enhanced from 45% and 30% to 98.9% and 82.3%, respectively. The quinone intermediates from phenol degradation, played a critical role in enhancing the removal rates of indole and quinoline as the electron transfer medium. Both the free radical pathway dominated by •OH and non-radical pathway with 1O2 play the main role in indole degradation, while •OH was the main factor in the catalytic degradation of phenol, quinoline and pyridine. By analysis the intermediates elucidated by Fourier transform ion cyclotron resonance mass spectrometry and three-dimensional excitation-emission matrix fluorescence spectra, the degradation molecular characteristics and pathways of the four pollutants in simulated coking wastewater were deciphered. The findings indicated that the catalyst SC-N3 prepared from the coking wastewater sludge presented unique catalytic properties and possessed a promising application in the degradation of refractory wastewater.

Tracking the history of polycyclic aromatic compounds in London through a River Thames sediment core and ultrahigh resolution mass spectrometry

Polycyclic aromatic compounds (PACs), including polycyclic aromatic hydrocarbons (PAHs) and heteroatom-containing analogues, constitute an important environmental contaminant class. For decades, limited numbers of priority PAHs have been routinely targeted in pollution investigations, however, there is growing awareness for the potential occurrence of thousands of PACs in the environment. In this study, untargeted Fourier transform ion cyclotron resonance mass spectrometry was used for the molecular characterisation of PACs in a sediment core from Chiswick Ait, in the River Thames, London, UK. Using complex mixture analysis approaches, including aromaticity index calculations, the number of molecular PAC components was determined for eight core depths, extending back to the 1930s. A maximum of 1676 molecular compositions representing PACs was detected at the depth corresponding to the 1950s, and a decline in PAC numbers was observed up the core. A case linking the PACs to London’s coal consumption history is presented, alongside other possible sources, with some data features indicating pyrogenic origins. The overall core profile trend in PAC components, including compounds with oxygen, sulfur, nitrogen, and chlorine atoms, is shown to broadly correspond to the 16 priority PAH concentration profile trend previously determined for this core. These findings have implications for other industry-impacted environments.

New piperazine and morpholine derivatives: mass spectrometry characterization and evaluation of their antimicrobial activity

Recently, pharmaceutical research has been focused on the design of new antibacterial drugs with higher selectivity towards several strains. Major issues concern the possibility to obtain compounds with fewer side effects, at the same time effectively overcoming the problem of antimicrobial resistance. Several solutions include the synthesis of new pharmacophores starting from piperazine or morpholine core units. Mass spectrometry-based techniques offer important support for the structural characterization of newly synthesized compounds to design safer and more effective drugs for various medical conditions. Here, two new piperazine derivatives and four new morpholine derivatives were synthesized and structurally characterized through a combined approach of Fourier transform-ion cyclotron resonance (FT-ICR) and Linear Trap Quadrupole (LTQ) mass spectrometry. The support of both high-resolution and low-resolution mass spectrometric data namely accurate mass measurements, isotopic distribution and MSn spectra, was crucial to confirm the success of the synthesis. These compounds were further evaluated for inhibitory activity against a total of twenty-nine Gram-positive and Gram-negative bacteria to determine the action spectrum and the antimicrobial effectiveness. Results demonstrated compounds’ antimicrobial activity against many tested bacterial species, providing an inhibitory effect linked to different chemical structure and suggesting that the new-synthesized derivatives could be considered as promising antimicrobial agents.

Quality evaluation of natural monomer flavors for Chinese tobacco industry based on dual mode combined Fourier transform ion cyclotron resonance mass spectrometry and isotopic fine structures.

Natural monomer flavors can modify the taste of cigarettes. However, no report was published to establish the quality control method for their chemical compositions. In this study, licorice, a traditional natural monomer flavor used in tobacco aroma processing, was selected, and the fingerprint was developed by high-performance liquid chromatography (HPLC). Next, the chemical markers of samples from different places of origin were discovered by multivariate statistical analysis. Then, its chemical constituents were identified by combination of HPLC-Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), direct infusion FT-ICR-MS (DI-FT-ICR-MS), and the technology of isotopic fine structures (IFSs). Moreover, its characteristic constituents were quantitatively analyzed using HPLC. The 14 common peaks were assigned in the fingerprint, and 8 of them were considered as qualitative markers by multivariate statistical analysis. A total of 42 chemical constituents were detected using HPLC-FT-ICR-MS, and 13 of them were unambiguously identified by references. Meanwhile, the elemental compositions of other eight unknown chemical components were decisively determined using IFSs. Subsequently, the contents of five characteristic constituents in 11 batches of samples were determined. The integration strategy established here can discover and quantify the chemical markers for improving the quality control standard of natural monomer flavor of licorice. It is expected that the strategy will be valuable for further quality control of other natural monomer flavors in Chinese tobacco industry.

Two-Dimensional Fourier Transform Ion Cyclotron Resonance Mass Spectrometry by Matrix-Assisted Laser Desorption Ionization.

Two-dimensional Fourier transform ion cyclotron resonance (2D FTICR) mass spectrometry is a developing form of data-independent acquisition that allows for the simultaneous fragmentation and correlation of fragment ions to their precursors across a range of m/z values. The modern usage of 2D FTICR is performed using electrospray ionization (ESI) as the dried droplet preparation for matrix-assisted laser desorption ionization (MALDI) does not produce a consistent packet of ions over a number of scans. This work uses pneumatic spray techniques from mass spectrometry imaging to create a homogeneous surface for use with MALDI as an ionization source for 2D FTICR. A mixture of peptides and matrix was deposited onto a glass slide using an HTX pneumatic sprayer. MALDI was then used to ionize the peptide mixture for use with a standard 2D FTICR pulse sequence. The generated 2D spectrum reveals comparable structural information to spectra collected in a 1D experiment. Artifacts observed in the collected 2D MALDI spectra do not significantly differ from those expected from 2D ESI spectra.

Deciphering linkages between DON and the microbial community for nitrogen removal using two green sorption media in a surface water filtration system

The presence of dissolved organic nitrogen (DON) in stormwater treatment processes is a continuous challenge because of the intertwined nature of its decomposition, bioavailability, and biodegradability and its unclear molecular characteristics. In this paper, 21 T Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in combination with quantitative polymerase chain reaction was applied to elucidate the molecular change of DON and microbial population dynamics in a field-scale water filtration system filled with two specialty adsorbents for comparison in South Florida where the dry and wet seasons are distinctive annually. The adsorbents included CPS (clay-perlite and sand sorption media) and ZIPGEM (zero-valent iron and perlite-based green environmental media). Our study revealed that seasonal effects can significantly influence the dynamic characteristics and biodegradability of DON. The microbial population density in the filter beds indicated that three microbial species in the nitrogen cycle were particularly thrived for denitrification, dissimilatory nitrate reduction to ammonium, and anaerobic ammonium oxidation via competition and commensalism relationships during the wet season. Also, there was a decrease in the compositional complexity and molecular weight of the DON groups (CnHmOpN1, CnHmOpN2, CnHmOpN3, and CnHmOpN4), revealed by the 21 T FT-ICR MS bioassay, driven by a microbial population quantified by polymerase chain reaction from the dry to the wet season. These findings indirectly corroborate the assumption that the metabolism of microorganisms is much more vigorous in the wet season. The results affirm that the sustainable materials (CPS and ZIPGEM) can sustain nitrogen removal intermittently by providing a suitable living environment in which the metabolism of microbial species can be cultivated and enhanced to facilitate physico-chemical nitrogen removal across the two types of green sorption media.

From the grapevine to the glass: A wine metabolomics tale by FT-ICR-MS.

Wine is one of the most consumed beverages around the world. Its unique characteristics arise from numerous processes, from the selection of grapevine varieties and grapes, the effect of the terroir and geographical origin, through the biochemical process of fermentation by microorganisms, until its aging. All molecules found in wine define its chemical fingerprint and can be used to tell the story of its origin, production, authenticity and quality. Wine's chemical composition can be characterized using an untargeted metabolomics approach based on extreme resolution mass spectrometry. Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) is currently the most powerful analytical technique to analyse such complex sample, providing the most comprehensive analysis of the chemical fingerprint of wine.

Dissolved organic matter isolates obtained by solid phase extraction exhibit higher absorption and lower photo-reactivity: Effect of components

Notable differences in photo-physical and chemical properties were found between bulk water and solid phase extraction (SPE) isolates for dissolved organic matter (DOM). The moieties extracted using modified styrene divinylbenzene cartridges, which predominantly consist of conjugated aromatic molecules like humic acids, contribute mainly to light absorption but exhibit lower quantum yields of fluorescence and photo-produced reactive intermediates (PPRIs). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed lignin as the moieties displaying most significant variance in abundance. In Van Krevelen-Spearman plot, we observed molecules positively or negatively correlated with DOM's optical and photochemical properties (including SUVA254, steady-state concentrations of ·OH, 1O2 quantum yield, etc.) were confined to specific regions, which can be delineated using a threshold modified aromaticity index (AImod) of 0.3. Based on the relationships between optical properties and PPRI production, it is suggested that the energy gap between ground state and excited singlet state (△ES1→S0), governing the inner conversion rate, serves as a determinant for apparent quantum yield of PPRIs in DOM, with intra-molecular charge transfer (CT) interactions potentially playing a pivotal role. Regarding DOM's photoreactivity with pollutants, this study has revealed, for the first time, that protein/amino sugars/amino acids could act as antioxidant groups in addition to phenols on the photolysis of sulfadiazine. These findings provide valuable insights into DOM photochemistry and are expected to stimulate further research in this area.

Appearance of Recalcitrant Dissolved Black Carbon and Dissolved Organic Sulfur in River Waters Following Wildfire Events.

Increasing wildfire frequency, a consequence of global climate change, releases incomplete combustion byproducts such as aquatic pyrogenic dissolved organic matter (DOM) and black carbon (DBC) into waters, posing a threat to water security. In August 2022, a series of severe wildfires occurred in Chongqing, China. Samples from seven locations along the Yangtze and Jialing Rivers revealed DBC, quantified by the benzene poly(carboxylic acid) (BPCA) method, comprising 9.5-19.2% of dissolved organic carbon (DOC). High concentrations of BPCA-DBC with significant polycondensation were detected near wildfire areas, likely due to atmospheric deposition driven by wind. Furthermore, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS) revealed that wildfires were associated with an increase in condensed aromatics, proteins, and unsaturated hydrocarbons, along with a decrease in lignins. The condensed aromatics primarily consisted of dissolved black nitrogen (DBN), contributing to abundant high-nitrogen-containing compounds in locations highly affected by wildfires. Meanwhile, wildfires potentially induced the input of recalcitrant sulfur-containing protein-like compounds, characterized by high oxidation, aliphatic nature, saturation, and low aromaticity. Overall, this study revealed the appearance of recalcitrant DBC and dissolved organic sulfur in river waters following wildfire events, offering novel insights into the potential impacts of wildfires on water quality and environmental biogeochemistry.

Kinetics, products and mechanisms of unsaturated alcohols and NO3 radicals

Unsaturated alcohols are emitted in the atmosphere from anthropogenic and biological sources. Although NO3 radical-initiated reaction of unsaturated alcohols constitute a significant portion to SOA formation, less studies have been reported. In this study, the rate constants of the reactions between NO3 radicals with 2-methyl-2-propen-1-ol (2M2P1O), (E)-4-hexen-1-ol (t-4H1O) and 4-penten-2-ol (4P2O) were measured at 298 ± 2 K by using relative rate methods. The rate constants were 3.41 ± 0.51 (2M2P1O), 6.45 ± 0.66 (t-4H1O) and 0.56 ± 0.15 (4P2O) (in units of 10−13 cm3molecule−1s−1), respectively. The reaction rates were also estimated by structure-activity relationships (SARs) method and compared with the experimental results. It showed that the estimated rate constant of 4-penten-2-ol by SARs was unreasonable due to the lack of group parameters. In addition, large amounts of organic nitrates were identified based on fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). The MS results showed that dinitrates were primary SOA components. The obtained reaction rate constants and the formation mechanisms of organic nitrates provide an important experimental basis for future atmospheric chemical models.

Evaluations of Weathering of Polar and Nonpolar Petroleum Components in a Simulated Freshwater-Oil Spill by Orbitrap and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry.

The comprehensive chemical characterization of crude oil is important for the evaluation of the transformation and fate of components in the environment. Molecular-level speciation of naphthenic acid fraction compounds (NAFCs) was investigated in a mesoscale spill tank using both negative-ion electrospray ionization (ESI) Orbitrap mass spectrometry (MS) and positive-ion atmospheric pressure photoionization Fourier transform ion cyclotron resonance mass spectrometry (APPI-FT-ICR-MS). Both ionization techniques are coupled to high-resolution mass spectrometric detectors (ESI: Orbitrap MS; APPI: FT-ICR-MS at 9.4 T), enabling insight into the behavior and fate of petrogenic compounds during a simulated freshwater crude oil spill. Negative-ion ESI Orbitrap-MS reveals that oxygen-containing (Ox) classes are detected early in the spill, whereby species with more oxygen per molecule evolve later in the simulated spill. The O2-containing species gradually decreased in relative abundance, while O3 and O4 species increased in relative abundance throughout the simulated spill, which could correspond to a relative degree of oxygen incorporation. Nonpolar speciation by positive-ion APPI 9.4 T FT-ICR-MS allowed for the identification of water-soluble nonpolar and less polar acidic species. Molecular-level graphical representation of elemental compositions derived from simulated spill water-soluble and oil-soluble species suggest that biological activity is the primary degradation mechanism and that biodegradation was the dominant mechanism based on the negative-ion ESI Orbitrap-MS results.

Atmospheric pressure field desorption-trapped ion mobility-mass spectrometry coupling.

While field ionization (FI) and field desorption (FD) are established soft vacuum ionization methods in mass spectrometry (MS), the technique of atmospheric pressure field desorption (APFD) has only recently been added to the repertoire. Similar to FI and FD, APFD can yield both positive even-electron ions of highly polar or ionic compounds and positive molecular ions, M+•, e.g., of polycyclic aromatic compounds. Thus, a dedicated APFD source assembly has been constructed and demonstrated to allow for robust APFD operation. This device also enabled observation of the emitter during operation and allowed for resistive emitter heating, thereby speeding up the desorption of the analytes and expanding the range of analytes accessible to APFD. While initial work was done using a Fourier transform-ion cyclotron resonance (FT-ICR) mass spectrometer, the new APFD source offered the flexibility to also be used on a trapped ion mobility-quadrupole-time-of-flight (TIMS-Q-TOF) instrument, and thus, it would be possible to be mounted to any Bruker mass spectrometer featuring an atmospheric pressure (AP) interface. Operating an APFD source at a TIMS-Q-TOF instrument called for the exploration of the combined use of APFD and TIMS. Here, operation, basic properties, and capabilities of this new atmospheric pressure field desorption-trapped ion mobility-mass spectrometry (APFD-TIMS-MS) coupling are described. APFD-TIMS-MS is employed for the separation of individual components of oligomers and for the accurate determination of their collision cross section (CCS). This work describes the application of APFD-TIMS-MS on poly(ethylene glycol) forming [M + Na]+ ions by cationization and on an amine-terminated poly(propylene glycol) yielding [M + H]+ ions. Some compounds forming molecular ions, M+•, by field ionization such as [60]fullerene and a mixture of four polycyclic aromatic hydrocarbons (PAHs) are examined. In APFD-TIMS-MS, the limits of detection (LODs) of fluoranthene and benzo[a]pyrene M+• ions are determined as ≈100pg and <1pg, respectively. Finally, [60]fullerene is analyzed by negative-ion APFD-TIMS-MS where it yields a molecular anion, M-•.

Photochemical evolution of the molecular composition of dissolved organic carbon and dissolved brown carbon from wood smoldering

Recently, extreme wildfires occur frequently around the world and emit substantial brown carbon (BrC) into the atmosphere, whereas the molecular compositions and photochemical evolution of BrC remain poorly understood. In this work, primary smoke aerosols were generated from wood smoldering, and secondary smoke aerosols were formed by the OH radical photooxidation in an oxidation flow reactor, where both primary and secondary smoke samples were collected on filters. After solvent extraction of filter samples, the molecular composition of dissolved organic carbon (DOC) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FTICR MS). The molecular composition of dissolved BrC was obtained based on the constraints of DOC formulae. The proportion of dissolved BrC fractions accounted for approximately 1/3–1/2 molecular formulae of DOC. The molecular characteristics of dissolved BrC showed higher levels of carbon oxidation state, double bond equivalents, and modified aromaticity index than those of DOC, indicating that dissolved BrC fractions were a class of organic structures with relatively higher oxidation state, unsaturated and aromatic degree in DOC fractions. The comparative analysis suggested that aliphatic and olefinic structures dominated DOC fractions (contributing to 70.1%-76.9%), while olefinic, aromatic, and condensed aromatic structures dominated dissolved BrC fractions (contributing to 97.5%-99.9%). It is worth noting that dissolved BrC fractions only contained carboxylic-rich alicyclic molecules (CRAMs)-like structures, unsaturated hydrocarbons, aromatic structures, and highly oxygenated compounds. CRAMs-like structures were the most abundant species in both DOC and dissolved BrC fractions. Nevertheless, the specific molecular characteristics for DOC and dissolved BrC fractions varied with subgroups after aging. The results highlight the similarities and differences in the molecular compositions and characteristics of DOC and dissolved BrC fractions with aging. This work will provide insights into understanding the molecular composition of DOC and dissolved BrC in smoke.

Molecular composition and characteristics of Sediment-adsorbed Dissolved Organic Matter (SDOM) along the coast of China

Sediment-adsorbed Dissolved Organic Matter (SDOM) in coast plays a crucial role in the terrestrial and marine carbon cycle processes of the global environment. However, understanding the transport dynamics of SDOM along the coast of China, particularly its interactions with sediments, remains elusive. In this study, we analyzed the δ13C and δ15N stable isotopic compositions, as well as the molecular characteristics of SDOM collected from coastal areas spanning the Bohai Sea (BS), Yellow Sea (YS), East China Sea (ECS), and South China Sea (SCS), by using isotope ratio mass spectrometry and Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). We identified the predominant sources of carbon and nitrogen in coastal sediments, revealing terrigenous origins for most C and N, while anthropogenic sources dominated in the SCS. Spatial variations in SDOM chemodiversity were observed, with diverse molecular components influenced by distinct environmental factors and sediment sources. Notably, lignins and saturated compounds (such as proteins/amino sugars) were the predominant molecular compounds detected in coastal SDOM. Through Mantel tests and Spearman's correlation analysis, we elucidated the significant influence of spatial environmental factors (temperature, DO, salinity, and depth) and sediment sources on SDOM molecular chemodiversity. These findings contribute to a more comprehensive understanding of the carbon cycle dynamics along the Chinese coast.

Insights into the transformation of natural organic matter during UV/peroxydisulfate treatment by FT-ICR MS and machine learning: Non-negligible formation of organosulfates

Natural organic matter (NOM) is a major sink of radicals in advanced oxidation processes (AOPs) and understanding the transformation of NOM is important in water treatment. By using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) in conjunction with machine learning, we comprehensively investigated the reactivity and transformation of NOM, and the formation of organosulfates during the UV/peroxydisulfate (PDS) process. After 60 min UV/PDS treatment, the CHO formula number and dissolved organic carbon concentration significantly decreased by 83.4% and 74.8%, respectively. Concurrently, the CHOS formula number increased substantially from 0.7% to 20.5%. Machine learning identifies DBE and AImod as the critical characteristics determining the reactivity of NOM during UV/PDS treatment. Furthermore, linkage analysis suggests that decarboxylation and dealkylation reactions are dominant transformation pathways, while the additions of SO3 and SO4 are also non-negligible. According to SHAP analysis, the m/z, number of oxygens, DBE and O/C of NOM were positively correlated with the formation of organosulfates in UV/PDS process. 92 organosulfates were screened out by precursor ion scan of HPLC-MS/MS and verified by UPLC-Q-TOF-MS, among which, 7 organosufates were quantified by authentic standards with the highest concentrations ranging from 2.1 to 203.0 ng L‒1. In addition, the cytotoxicity of NOM to Chinese Hamster Ovary (CHO) cells increased by 13.8% after 30 min UV/PDS treatment, likely responsible for the formation of organosulfates. This is the first study to employ FT-ICR MS combined with machine learning to identify the dominant NOM properties affecting its reactivity and confirmed the formation of organosulfates from sulfate radical oxidation of NOM.

Warming Leads to Changes in Soil Organic Carbon Molecules Due to Decreased Mineral Protection.

Climate change affects the content and composition of soil organic carbon (SOC). However, warming-induced changes in the SOC compounds remain unknown. Using nuclear magnetic resonance spectroscopy, molecular mixing models, and Fourier transform ion cyclotron resonance mass spectrometry, we analyzed the variations and relationships in molecular compounds in Mollisol with 10-56 g C kg-1 soil-1 by translocating soils under six climate regimes. We found that increased temperature and precipitation were negatively correlated with carbohydrate versus lipid and lignin versus protein. The former was consistent across soils with varying SOC contents, but the latter decreased as the SOC content increased. The carbohydrate-lipid correlations were related to dithionite-citrate-extractable Fe, while the lignin-protein correlations were linked to changes in moisture and pyrophosphate-extractable Fe/Al. Our findings indicate that the reduction in the mineral protection of SOC is associated with molecular alterations in SOC under warming conditions.