Metal-support interaction in supported Pt single-atom catalyst promotes lattice oxygen activation to achieve complete oxidation of acetone at low concentrations.

A precious metal catalyst with loaded Pt single atoms was prepared and used for the complete oxidation of C3H6O. Detailed results show that the T100 of the 1.5Pt SA/γ-Al2O3 catalyst in the oxidation process of acetone is 250 °C, the TOF of Pt is 1.09 × 10-2 s-1, and the catalyst exhibits good stability. Characterization reveals that the high dispersion of Pt single atoms and strong interaction with the carrier improve the redox properties of the catalyst, enhancing the adsorption and dissociation capability of gaseous oxygen. DFT calculations show that after the introduction of Pt, the oxygen vacancy formation energy on the catalyst surface is reduced to 1.2 eV, and PDOS calculations prove that electrons on Pt atoms can be quickly transferred to O atoms, increasing the number of electrons on the σp * bond and promoting the escape of lattice oxygen. In addition, in situ DRIFTS and adsorption experiments indicate that the C3H6O oxidation process follows the Mars-van Krevelen reaction mechanism, and CH2 =C(CH3)=O(ads), O* (O2-), formate, acetate, and carbonate are considered as the main intermediate species and/or transients in the reaction process. Particularly, the activation rate of O2 and the cleavage of the -C-C- bond are the main rate-determining steps in the oxidation of C3H6O. This work will further enhance the study of the oxidation mechanism of oxygenated volatile organic pollutants over loaded noble metal catalysts.

Characterization of Low-Molecular-Weight Dissolved Organic Matter Using Optional Dialysis and Orbitrap Mass Spectrometry.

Low-molecular-weight (LMW, <1000 Da) dissolved organic matter (DOM) plays a significant role in metal/organic pollutant complexation, as well as photochemical/microbiological processes in freshwater ecosystems. The micro size and high reactivity of LMW-DOM hinder its precise characterization. In this study, Suwannee River fulvic acid (SRFA), a commonly used reference material for aquatic DOM, was applied to examine the optical features and molecular composition of LMW-DOM by combining membrane separation, ultraviolet-visible absorption and Orbitrap mass spectrometry (MS) characterization. The 100-500 Da molecular weight cut-off (MWCO) membrane had a better performance in regard to separating the tested LMW-DOM relative to the 500-1000 Da MWCO membrane. The ultraviolet-visible absorbance decreased dramatically for the retentates, whereas it increased for the dialysates. Specifically, carbohydrates, lipids and peptides exhibited high selectivity to the 100-500 Da MWCO membrane in early dialysis. Lignins, tannins and condensed aromatic molecules displayed high permeability to the 500-1000 Da MWCO membrane in late dialysis. Overall, the retentates were dominated by aromatic rings and phenolic hydroxyls with high O/Cwa (weighted average of O/C) and low H/Cwa. Conversely, such dialysates had numerous aliphatic chains with high H/Cwa and low O/Cwa compared to SRFA. In particular, LMW-DOM below 200 Da was identified by Orbitrap MS. This work provides an operational program for identifying LMW-DOM based on the SRFA standard and MS analysis.

Bioenergetic mapping of 'healthy microbiomes' via compound processing potential imprinted in gut and soil metagenomes.

Despite mounting evidence of their importance in human health and ecosystem functioning, the definition and measurement of 'healthy microbiomes' remain unclear. More advanced knowledge exists on health associations for compounds used or produced by microbes. Environmental microbiome exposures (especially via soils) also help shape, and may supplement, the functional capacity of human microbiomes. Given the synchronous interaction between microbes, their feedstocks, and micro-environments, with functional genes facilitating chemical transformations, our objective was to examine microbiomes in terms of their capacity to process compounds relevant to human health. Here we integrate functional genomics and biochemistry frameworks to derive new quantitative measures of in silico potential for human gut and environmental soil metagenomes to process a panel of major compound classes (e.g., lipids, carbohydrates) and selected biomolecules (e.g., vitamins, short-chain fatty acids) linked to human health. Metagenome functional potential profile data were translated into a universal compound mapping 'landscape' based on bioenergetic van Krevelen mapping of function-level meta-compounds and corresponding functional relative abundances, reflecting imprinted genetic capacity of microbiomes to metabolize an array of different compounds. We show that measures of 'compound processing potential' associated with human health and disease (examining atherosclerotic cardiovascular disease, colorectal cancer, type 2 diabetes and anxious-depressive behavior case studies), and displayed seemingly predictable shifts along gradients of ecological disturbance in plant-soil ecosystems (three case studies). Ecosystem quality explained 60-92 % of variation in soil metagenome compound processing potential measures in a post-mining restoration case study dataset. With growing knowledge of the varying proficiency of environmental microbiota to process human health associated compounds, we might design environmental interventions or nature prescriptions to modulate our exposures, thereby advancing microbiota-oriented approaches to human health. Compound processing potential offers a simplified, integrative approach for applying metagenomics in ongoing efforts to understand and quantify the role of microbiota in environmental- and human-health.

Catalytic Oxidation of Chlorobenzene over HSiW/CeO2 as a Co-Benefit of NOx Reduction: Remarkable Inhibition of Chlorobenzene Oxidation by NH3.

There is an urgent need to develop novel and high-performance catalysts for chlorinated volatile organic compound oxidation as a co-benefit of NOx. In this work, HSiW/CeO2 was used for chlorobenzene (CB) oxidation as a co-benefit of NOx reduction and the inhibition mechanism of NH3 was explored. CB oxidation over HSiW/CeO2 primarily followed the Mars-van-Krevelen mechanism and the Eley-Rideal mechanism, and the CB oxidation rate was influenced by the concentrations of surface adsorbed CB, Ce4+ ions, lattice oxygen species, gaseous CB, and surface adsorbed oxygen species. NH3 not only strongly inhibited CB adsorption onto HSiW/CeO2, but also noticeably decreased the amount of lattice oxygen species; hence, NH3 had a detrimental effect on the Mars-van-Krevelen mechanism. Meanwhile, NH3 caused a decrease in the amount of oxygen species adsorbed on HSiW/CeO2, which hindered the Eley-Rideal mechanism of CB oxidation. Hence, NH3 significantly hindered CB oxidation over HSiW/CeO2. This suggests that the removal of NOx and CB over this catalyst operated more like a two-stage process rather than a synergistic one. Therefore, to achieve simultaneous NOx and CB removal, it would be more meaningful to focus on improving the performances of HSiW/CeO2 for NOx reduction and CB oxidation separately.

Non-Oxidative Coupling of Methane: Interplay of Catalyst Interface and Gas Phase Mechanisms.

Non-oxidative coupling of methane (NOCM) is a sought-after reaction that has been studied for decades. Harsh reaction conditions (T >800°C) in the face of limited catalyst stability lead to rapid catalyst deactivation and strong coking, preventing application thus far. Recent reports have shown the significance of an interplay of catalyst nature and reaction conditions, whereas metal carbides have prevailed to play a crucial role which involves incorporation of carbidic carbon in C2Hx and aromatic products. This perspective gives an overview of proposed mechanistic pathways and considerations about experiment conditions in order to foster a rational catalyst design platform for NOCM.

A Comparison of the Reactivity of the Lattice Nitrogen in Tungsten Substituted Co3 Mo3 N and Ni2 Mo3 N.

The effect of the partial substitution of Mo with W in Co3 Mo3 N and Ni2 Mo3 N on ammonia synthesis activity and lattice nitrogen reactivity has been investigated. This is of interest as the coordination environment of lattice N is changed by this process. When tungsten was introduced into the metal nitrides by substitution of Mo atoms, the catalytic performance was observed to have decreased. As expected, Co3 Mo3 N was reduced to Co6 Mo6 N under a 3 : 1 ratio of H2 /Ar. Co3 Mo2.6 W0.4 N was also shown to lose a large percentage of lattice nitrogen under these conditions. The bulk lattice nitrogen in Ni2 Mo3 N and Ni2 Mo2.8 W0.2 N was unreactive, demonstrating that substitution with tungsten does not have a significant effect on lattice N reactivity. Computational calculations reveal that the vacancy formation energy for Ni2 Mo3 N is more endothermic than Co3 Mo3 N. Furthermore, calculations suggest that the inclusion of W does not have a substantial impact on the surface N vacancy formation energy or the N2 adsorption and activation at the vacancy site.

Characterization of the Nonpolar and Polar Extractable Components of Glanded Cottonseed for Its Valorization.

Cottonseed is the second major product of cotton (Gossypium spp.) crops after fiber. Thus, the characterization and valorization of cottonseed are important parts of cotton utilization research. In this work, the nonpolar and polar fractions of glanded (Gd) cottonseed were sequentially extracted by 100% hexane and 80% ethanol aqueous solutions and subjected to 13C and 1H nuclear magnetic resonance (NMR) spectroscopy and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), respectively. The nonpolar (crude oil) extracts showed the characteristic NMR peak features of edible plant oils with the absence of ω-3 linolenic acid. Quantitative analysis revealed the percentage of polyunsaturated, monounsaturated, and saturated fatty acids as 48.7%, 16.9%, and 34.4%, respectively. Both general unsaturated fatty acid features and some specific olefinic compounds (e.g., oleic, linolenic, and gondonic acids) were found in the nonpolar fraction. In the polar extracts, FT-ICR MS detected 1673 formulas, with approximately 1/3 being potential phenolic compounds. Both the total and phenolic formulas fell mainly in the categories of lipid, peptide-like, carbohydrate, and lignin. A literature search and comparison further identifies some of these formulas as potential bioactive compounds. For example, one compound [2,5-dihydroxy-N'-(2,3,4-trihydroxybenzylidene) benzohydrazide] identified in the polar extracts is likely responsible for the anticancer function observed when used on human breast cancer cell lines. The chemical profile of the polar extracts provides a formulary for the exploration of bioactive component candidates derived from cottonseed for nutritive, health, and medical applications.

Characterization of Corn Silk Extract Using HPLC/HRMS/MS Analyses and Bioinformatic Data Processing.

In addition to having different biological activities of interest, corn silks play a role in the defense of plants. While benzoxamines and flavonoids have already been identified as molecules of plant defense and growth mechanisms, knowledge on the phytochemical composition of corn silk is lacking. Such knowledge would make it possible to better select the most effective varieties to improve resistance or bioactive properties. In this article, an approach was implemented to map a corn silk extract in two complementary ways. The first one involved working with UHPLC/HRMS data and Kendrick and van Krevelen plots to highlight a homologous series of compounds, such as lipids from 17 to 23 carbons, monoglycosylated flavonoids from 21 to 24 carbons, diglycosylated flavonoids of 26 to 28 carbons and organic acids of 14 to 19 carbons. The second way was to analyze the sample in UHPLC/HRMS2 and to plot mass spectral similarity networks with the GNPS platform and Cytoscape software to refine identification. By combining the information obtained, we were able to propose an identification for 104 detected molecules, including 7 nitrogenous, 28 lipidic and 67 phenolic compounds, leading to the first detailed phytochemical analysis of corn silk extract.

Soil Organic Matter Molecular Composition Shifts Driven by Forest Regrowth or Pasture after Slash-and-Burn of Amazon Forest.

Slash-and-burn of Amazon Forest (AF) for pasture establishment has increased the occurrence of AF wildfires. Recent studies emphasize soil organic matter (SOM) molecular composition as a principal driver of post-fire forest regrowth and restoration of AF anti-wildfire ambience. Nevertheless, SOM chemical shifts caused by AF fires and post-fire vegetation are rarely investigated at a molecular level. We employed pyrolysis-gas chromatography-mass spectrometry to reveal molecular changes in SOM (0-10, 40-50 cm depth) of a slash-burn-and-20-month-regrowth AF (BAF) and a 23-year Brachiaria pasture post-AF fire (BRA) site compared to native AF (NAF). In BAF (0-10 cm), increased abundance of unspecific aromatic compounds (UACs), polycyclic aromatic hydrocarbons (PAHs) and lipids (Lip) coupled with a depletion of polysaccharides (Pol) revealed strong lingering effects of fire on SOM. This occurs despite fresh litter deposition on soil, suggesting SOM minimal recovery and toxicity to microorganisms. Accumulation of recalcitrant compounds and slow decomposition of fresh forest material may explain the higher carbon content in BAF (0-5 cm). In BRA, SOM was dominated by Brachiaria contributions. At 40-50 cm, alkyl and hydroaromatic compounds accumulated in BRA, whereas UACs accumulated in BAF. UACs and PAH compounds were abundant in NAF, possibly air-transported from BAF.

Reactivity of Lattice Oxygen in Ti-Site-Substituted SrTiO3 Perovskite Catalysts.

An environmental catalyst in which a transition metal (Mn, Fe, or Co) was substituted into the Ti site of the host material, SrTiO3, was synthesized, and the reactivity of lattice oxygen was evaluated. For CO oxidation, Mn- and Co-doped SrTiO3 catalysts, which provided high thermal stabilities, exhibited higher activities than Pt/Al2O3 catalysts despite their low surface areas. Temperature-programmed reduction experiments using X-ray absorption fine structure (XAFS) measurements showed that the lattice oxygen of Co-doped catalyst was released at the lowest temperature. Isotopic experiments with CO and 18O2 revealed that the lattice oxygen was involved in CO oxidation on Fe- and Co-doped catalysts; that is, CO oxidation on these catalysts proceeded via the Mars-van Krevelen mechanism. On the other hand, for Mn-doped catalyst, the contribution of lattice oxygen to CO oxidation was relatively negligible, indicating that the reaction proceeded according to the Langmuir-Hinshelwood mechanism. This paper clearly demonstrates that the catalytic mechanism can be adjusted by substituting transition metals into SrTiO3.

Molecular level characterization of the effect of roasting on the extractable components of glandless cottonseed by Fourier transform ion cyclotron resonance mass spectrometry.

Roasting is a technological process in some food applications of agricultural products. To investigate the composition changes of the extractable functional/bioactive components of cottonseed, in this work, glandless cottonseed kernels were roasted at 110, 120, 140 and 150 °C for 15 min, respectively. The UV/vis data of the 80 % ethanol extracts found that roasting increased the level of phenolic compounds. Electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry of the extracts identified about 44 % to 55 % of total formulas as potential phenolic compounds. Roasting (up to 140 °C) mainly increased carbohydrate-, lignin-, and tannin-like compounds while lipid-like compounds decreased. The compositional changes at 150 °C were less than those at 140 °C, attributed to devolatilization at the higher temperature. The information of chemical profiling of cottonseed and the roasting impact would be greatly useful in enhanced utilization of cottonseed as nutrient and functional foods or food supplements.

Untargeted metabolomic analysis by ultra-high-resolution mass spectrometry for the profiling of new Italian wine varieties.

The chemical composition of wine samples comprises numerous bioactive compounds responsible for unique flavor and health-promoting properties. Thus, it's important to have a complete overview of the metabolic profile of new wine products in order to obtain peculiar information in terms of their phytochemical composition, quality, and traceability. To achieve this aim, in this work, a mass spectrometry-based phytochemical screening was performed on seven new wine products from Villa D'Agri in the Basilicata region (Italy), i.e., Aglianico Bianco, Plavina, Guisana, Giosana, Malvasia ad acino piccolo, Colata Murro and Santa Sofia. Ultra-high-resolution mass spectrometry data were processed into absorption mode FT-ICR mass spectra, in order to remove artifacts and achieve a higher resolution and lower levels of noise. Accurate mass-to-charge ratio (m/z) values were converted into putative elemental formulas. Therefore, 2D van Krevelen diagrams were used as a tool to obtain molecular formula maps useful to perform a rapid and more comprehensive analysis of the wine sample metabolome. The presence of important metabolite classes, i.e., fatty acid derivatives, amino acids and peptides, carbohydrates and phenolic derivatives, was assessed. Moreover, the comparison of obtained metabolomic maps revealed some differences among profiles, suggesting their employment as metabolic fingerprints. This study shed some light on the metabolic composition of seven new Italian wine varieties, improving their value in terms of related bioactive compound content. Moreover, different metabolomic fingerprints were obtained for each of them, suggesting the use of molecular maps as innovative tool to ascertain their unique metabolic profile.

Hydrophobicity of soils affected by fires: An assessment using molecular markers from ultra-high resolution mass spectrometry.

Soil water repellency (SWR) is a physical property due to a complex interaction of factors (e.g., fire, soil organic matter, soil texture) that reduces the soil water infiltration capacity. Traditionally, SWR is attributed to the accumulation and redistribution of hydrophobic compounds within soil profile. To obtain further insight into chemical compounds, which could be associated with SWR, a study was done on coarse (1-2 mm) and fine (< 0.05 mm) granulometric fractions of burned and unburned sandy soils under two Mediterranean vegetation biomes from Doñana National Park (Spain). The water drop penetration time (WDPT) test was used to assess the SWR. The molecular composition of extracted humic substances from the soil organic matter (SOM) was determined by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS). Partial least squares (PLS) regressions showed that the SWR can be predicted (P = 0.006) solely based on the abundances of approximately 1200 common compounds determined by FT-ICR/MS. This model confirmed the significant correlation between a specific SOM molecular composition and the SWR. The comparative analysis revealed that the SWR in the burned samples was significantly (P < 0.05) related to the abundance of aromatic and condensed compounds, while in the unburned samples there was a significant influence of aromatic hydrocarbons and lignin compounds. In the fine fraction, lipid compounds were significantly associated with the SWR. Contrastingly, the coarse fraction did not show any correlation. Alternatively, soils with a high SWR were significantly related to the presence of lipids and lignin. This analysis showed that combining FT-ICR/MS molecular characterizations with statistical treatments is a powerful approach for exploratory analysis suggesting that the structural features associated with SWR in the studied soils are different depending on the types of vegetation or the soil physical fractions with different particle size.

Experiment and Theory Clarify: Sc+ Receives One Oxygen Atom from SO2 to Form ScO+ , which Proves to be a Catalyst for the Hidden Oxygen-Exchange with SO2.

Using Fourier-transform ion cyclotron resonance mass spectrometry, it was experimentally determined that Sc+ in the highly diluted gas phase reacts with SO2 to form ScO+ and SO. By 18 O labeling, ScO+ was shown to play the role of a catalyst when further reacting with SO2 in a Mars-van Krevelen-like (MvK) oxygen exchange process, where a solid catalyst actively reacts with the substrate but emerges apparently unchanged at the end of the cycle. High-level quantum chemical calculations confirmed that the multi-step process to form ScO+ and SO is exoergic and that all intermediates and transition states in between are located energetically below the entrance level. The reaction starts from the triplet surface; although three spin-crossing points with minimal energy have been identified by computational means, there is no evidence that a two-state scenario is involved in the course of the reaction, by which the reactants could switch from the triplet to the singlet surface and back. Pivotal to the oxygen exchange reaction of ScO+ with SO2 is the occurrence of a highly symmetric four-membered cyclic intermediate by which two oxygen atoms become equivalent.

Effect of the Configuration of Copper Oxide-Ceria Catalysts in NO Reduction with CO: Superior Performance of a Copper-Ceria Solid Solution.

Various copper-ceria-based composites have attracted attention as efficient catalysts for the reduction of NO with CO. In this comparative study, we have examined the catalytic potential of different configurations of copper oxide-ceria catalysts, including catalysts based on a copper-ceria solid solution, copper oxide particles supported on ceria, and ball-milled copper oxide-ceria. The structurally different interfaces between the constituents of these catalysts afforded very different catalytic performances. The solid solution catalyst outperformed the corresponding ceria-supported and ball-milled CuO-CeO2 catalysts. The copper cations incorporated into the ceria lattice strongly improved the activity, N2 selectivity, and water vapor tolerance compared to the other catalyst configurations. The experimental observations are supported by first-principles density functional theory (DFT) studies of the reaction pathway, which indicate that the incorporation of Cu cations into the ceria matrix lowers the energy required for activating the lattice oxygen, thereby enhancing the formation and healing of oxygen vacancies, and thus promoting NO reduction with CO.

Influence of active pharmaceutical ingredient structures on Hansen solubility parameters.

In drug development, preformulation is the key step, where compatibility between active pharmaceutical ingredient (API) and excipients is the crucial parameter. To simplify this process, reliable and suitable prediction models are needed. In this case, Hansen solubility parameters (HSPs) can be used. Moreover, HSPs can also describe and characterize the surface properties of the measured substances. Precisely, the surface properties of APIs and excipients affect the compatibility of the resulting dosage form. In this work, HSPs of six selected APIs of different chemical nature were determined (tadalafil, vardenafil-hydrochloride trihydrate, mefenamic acid, bisoprolol hemi-fumarate, meloxicam and indomethacin) using inverse gas chromatography (IGC) according to Snyder and Karger adsorption model. This study aimed to investigate the influence of APIs structure on HSPs and to prove the sensitivity of this method to different chemical nature of measured substances. Our results showed the influence of selected APIs chemical nature on HSPs. These results can provide a better understanding of API behaviour during the drug development process.

Emission of (chlorinated) reclaimed water into a Mediterranean River and its related effects to the dissolved organic matter fingerprint.

High resolution mass spectrometry (HRMS) was used to investigate the dissolved organic matter (DOM) profile of a reclamation water trial performed in the Llobregat River (Spain) during summer 2019. 23 water samples (including tertiary effluents, surface river and drinking water), taken during five sampling campaigns, were analyzed and their van Krevelen diagrams were compared. The reclaimed water fingerprint was substantially different from the natural profile of the river, showing a higher number of heteroatomic signals (i.e. CHON, CHOS and CHONS) and the presence of high-intensity S-containing features. As a result, reclaimed water discharge introduced substantial changes in the signature of the lignin-like and soot-like compositional-spaces of the river DOM fingerprint. However, the effect on the drinking water fingerprint was, ultimately, very limited. Only a limited number of features (up to 34) were detected as exclusively emitted with the reclaimed water. During the second phase of the trial, the tertiary effluent was chlorinated for disinfection purposes. This process triggered the unexpected formation of a myriad of new features along the Llobregat River. Notably, 109 brominated/chlorinated features were detected, probably generated as a consequence of the photochemical decay of the emitted chloramines and their free-radical reaction with DOM, and three of them persisted in the final drinking water. The formation of halogenated species in situ in the Llobregat River entails uncertainty at ecological and water treatment levels and should be studied carefully to fully disclose the risks associated to wastewater effluent disinfection.

Biofilm development of Bacillus siamensis ATKU1 on pristine short chain low-density polyethylene: A case study on microbe-microplastics interaction.

A low-density polyethylene (LDPE) degrading bacterial strain (ATKU1) was isolated (99.86% similar with Bacillus siamensis KCTC 13613T) from a plastic dumping site to study interactions between microplastics (< 5 mm) and microorganisms. The strain was found (by scanning electron microscopy) to form biofilm on the microplastic surface after its interaction with LDPE (avg. Mw~4,000 Da and avg. Mn~1,700 Da) as a sole carbon source. Atomic force microscopy (AFM) showed the biofilm's 3-D developmental patterns and significantly increased Young's modulus of the LDPE surface after microbial treatment. Most of the viable bacteria attached to biofilms rather than media, which suggested their ability to utilize LDPE. Absorption bands of carbonyl, alkenyl, acyl, ester, primary-secondary alcohol, alkene groups and nitric oxides were found on the treated LDPE particles using Fourier-transform infrared spectroscopy. Fourier transform-ion cyclotron resonance mass spectrometry of the media indicated compositional shifts of the compounds after treatment (i.e., increase in the degree of unsaturation and increment in oxygen-to-carbon ratio) and presence of unsaturated hydrocarbons, polyketides, terpenoids, aliphatic/peptides, dicarboxylic acids, lipid-like compounds were hinted. The plastic degrading abilities of Bacillus siamensis ATKU1 suggest its probable application for large scale plastic bioremediation facility.

Application of Fourier transform ion cyclotron resonance mass spectrometry in deciphering molecular composition of soil organic matter: A review.

Swiftly deciphering soil organic matter (SOM) composition is critical for research on soil degradation and restoration. Recent advances in analytical techniques (e.g., optical methods and mass spectrometry) have expanded our understanding of the composition, origin, and evolution of SOM. In particular, the use of Fourier transform ion cyclotron resonance mass spectrometers (FTICR-MS) makes it possible to interpret SOM compositions at the molecular level. In this review, we discuss extraction, enrichment, and purification methods for SOM using FTICR-MS analysis; summarize ionization techniques, FTICR-MS mechanisms, data analysis methods, and molecular compositions of SOM in different environments (providing new insights into its origin and evolution); and discuss factors affecting its molecular diversity. Our results show that digenesis, combustion, pyrolysis, and biological metabolisms jointly contribute to the molecular diversity of SOM molecules. The SOM thus formed can further undergo photodegradation during transportation from land to fresh water (and subsequently oceans), resulting in the formation of dissolved organic matter (DOM). Better understanding the molecular features of DOM therefore accelerates our understanding of SOM evolution. In addition, we assess the degradation potential of SOM in different environments to better inform soil remediation methods. Finally, we discuss the merits and drawbacks of applying FTICR-MS on the analysis of SOM molecules, along with existing gaps in knowledge, challenges, and new opportunities for research in FTICR-MS applications and SOM identification.

Characterization of organic matter by HRMS in surface waters: Effects of chlorination on molecular fingerprints and correlation with DBP formation potential.

In order to understand and minimize the formation of halogenated disinfection by-products (DBPs), it is important to investigate how dissolved organic matter (DOM) contributes to their generation. In the present study, we analysed the DOM profile of water samples from the Barcelona catchment area by high resolution mass spectrometry (HRMS) and we studied the changes after chlorination. Chlorination produced significant changes in the DOM, decreased the average m/z and Kendrick mass defect (KMD) of their spectra and decreased the number and abundance of lignin-like features. The Van Krevelen (VK) fingerprint exhibited several noticeable changes, including the appearance of highly oxidized peaks in the tannin-like region (average O/C, 0.78 ± 0.08), the appearance of features with low H/C and the disappearance of more than half of the lipids-like features. Up to 657 halogenated peaks were generated during sample chlorination, most of which in the condensed hydrocarbons-like and the lignin-like region of the VK diagram. Around 200 features were found to be strongly correlated (ρ ≥ 0.795) to the formation potential of trihalomethanes (THMs) and 5 were correlated with the formation potential of haloacetonitrile (HANs). They all were plotted in the lignin fraction of the VK diagram, but both groups of features exhibited different nitrogen content: those features related to HANs FP had at least one nitrogen atoms in their structures, whilst those related to THMs did not.