Organic Precursors Research Articles

Formation of Aromatic Halogenated Disinfection Byproducts in Swimming Pool Water during Chlorination: Organic Precursors and Mechanisms.

Disinfection byproducts (DBPs) in swimming pool water are a significant public health concern. The formation of aromatic halogenated DBPs in swimming pool water has not been clarified previously. In this study, the occurrence of aromatic halogenated DBPs in swimming pool water was examined, and it was found that halohydroxybenzoic acids (HBAs) and halobenzoquinones (HBQs) were the most dominant aromatic halogenated DBPs in swimming pool water that were continuously formed. Thus, the formation of HBAs and HBQs in swimming pool water from different organic precursors, including natural organic matter (NOM), pharmaceuticals and personal care products (PPCPs), during chlorination was examined. The results demonstrate that the formation of HBAs and HBQs from the PPCPs was relatively high compared with that from NOM, suggesting that the PPCPs from human inputs might be important organic precursors of aromatic halogenated DBPs in swimming pool water. The formation mechanisms of HBAs and HBQs from three typical PPCPs (benzophenone-3 (BP-3), methyl p-hydroxybenzoate (MeP) and carbamazepine) were further explored. The results show that the PPCPs containing phenolic groups with higher degradation rates (BP-3 and MeP) possessed higher formation of HBAs and HBQs. The three organic precursors underwent a series of substitution, hydrolysis, oxidation, rearrangement, and intramolecular cyclization reactions to form HBAs and HBQs, while the phenolic groups and ring structures may significantly affect the reactions. The chlorine dose, bromide/iodide concentration, and temperature significantly affected the formation of HBAs and HBQs from MeP during chlorination.

Regulating Room-Temperature Phosphorescence of Organic Luminophores Through Stepwise Stabilization by Coordination and In-Situ Precipitation Reaction.

Developing efficiency and long-lived room-temperature phosphorescence (RTP) materials through straightforward methods is highly desired. In this work, a stepwise stabilization strategy was proposed by the coordination and in-situ precipitation reactions among organic precursors, inorganic cation and anions, producing room-temperature phosphorescence materials with high emission efficiency (phosphorescence quantum yield of 45 %). Structural and photophysical characterizations revealed the coordination reaction reduced the energy gaps between singlet and triplet states and stabilized the excited states of the guest molecules. The in-situ precipitation reaction produced a solid matrix, which provided isolated environments for protecting the excitons from quenching. The applications of RTP materials in information encryption were demonstrated. The presented results provided a new clue for producing RTP materials, and extended their applications in wide fields.

Synthesis of Homochiral N-Heterocyclic Carbene-Based Nanosheets for Enhanced Asymmetric Catalysis.

Utilizing ultrathin 2D metal-organic framework nanosheets (2D MONs) as supports for incorporating chiral catalysts represents a highly promising avenue in the field of asymmetric catalysis. In this study, four pairs of isostructural chiral metal-organic layers (MOLs) adorned with N-Heterocyclic carbene (NHC) groups are successfully synthesized. Notably, the obtained bulky (S)-1-Zn crystals can be readily delaminated into ultrathin MONs consisting of 1-2 layers through an ion intercalation-assisted exfoliation process. Subsequent asymmetric catalysis studies revealed that the NHC sites can be effectively activated by a proton sponge while maintaining structural integrity for the subsequent benzoin condensation. Due to their well-exposed catalytic sites, ultrathin morphology, and porous structure, the (S)-1-Zn nanosheets exhibited significantly enhanced yield and enantioselectivity compared to their bulk counterparts and organic precursors. This research highlights an efficient strategy for incorporating chiral NHC species onto 2D MONs, thereby unlocking their immense potential for heterogeneous asymmetric catalysis.

Tracing the origin of volatiles on Earth using nitrogen isotope ratios in iron meteorites

Understanding the relationships between the nitrogen (N) isotope ratios of early solar system planetesimals and terrestrial reservoirs is crucial for tracing the origin of volatiles on Earth. The Earth primarily grew from planetesimals and planetary embryos that accreted rapidly (within ∼1–2 Ma after CAIs) in the inner solar system, also known as the non-carbonaceous (NC) reservoir. Magmatic iron meteorites, which sample the metallic cores of the earliest solar system planetesimals, have emerged as a promising proxy in this exercise. NC irons are distinctly 15N-poor compared to their CC (carbonaceous or outer solar system) counterparts. However, the utility of this proxy is limited by the lack of knowledge of N isotope fractionation during core crystallization. Using high pressure-high temperature experiments, we show that equilibrium N isotopic fractionation between solid and liquid metal (Δ15Nsolid–liquid = δ15Nsolid − δ15Nliquid) is limited (≤1.2 ‰) under conditions relevant for core crystallization. This, combined with the siderophile character of N and limited equilibrium N isotope fractionation during core-mantle differentiation, suggests that the δ15N values of iron meteorites accurately represent the N isotopic composition of their parent bodies. Unlike the variation in the N isotope ratios of NC and CC chondrites, which can be attributed to the effects of parent-body processes acting on organic precursors, the 15N-poor nature of NC irons relative to CC irons likely offers the most definitive evidence for the distinct N isotopic compositions of the earliest inner and outer solar system planetesimals. The N isotopic composition of Earth’s primordial mantle (δ15N = <−40 ‰) suggests that it retains the memory of the early accretion of 15N-poor NC iron meteorite parent body-like planetesimals. The early accreted 15N-poor nitrogen may be stored in the deep mantle, segregated into the core, or lost to space during atmospheric loss caused by impacts. This signature was overprinted by the subsequent accretion and admixing of CC materials, which is reflected in the relatively 15N-rich nature of Earth’s atmosphere (δ15N = 0) and convecting mantle (δ15N = −5 ‰).

Nanometer-thick TiO2 channel thin film transistors as radical monitors for plasma enhanced atomic layer deposition

Nanometer-thick-TiO2-channel thin-film transistors (TFTs) are examined as oxidizing-agent monitors for room-temperature atomic layer deposition (RTALD). RTALD is a plasma-based process using plasma-excited humidified argon where OH radicals oxidize the precursor-gas adsorbed surface. In the TFT, the anatase TiO2 channel, with a thickness of 16 nm, is attached to a 300 nm thick gate capacitor of SiO2, while the channel surface is exposed to the ALD ambient. A heavily doped n-type Si substrate attached to the gate SiO2 is used as the gate electrode. The gate width and length are 1000 and 60 μm, respectively. When the TFT is installed in the RTALD chamber, the drain-current waveform is recorded in the course of the metal organic gas adsorption, evacuation of the residual gas, oxidization, and evacuation. In the present study, three kinds of metal organic (MO) precursors, tetrakis(dimethyl)amino titanium, tris(dimethyl)amino silane, and trimethyl aluminum are examined. The drain current exhibits strong responses upon the exposure of the plasma excited humidified argon. This suggests that OH radicals in the plasma might oxidize the adsorbed MO precursors to produce the OH moieties, where the surface polarization of OH moieties might enhance channel conductivity. The experimental results suggest the applicability of the present TFT as a plasma monitor in RTALD.

Carbon-Doped TiO2 Nanofiltration Membranes Prepared by Interfacial Reaction of Glycerol with TiCl4 Vapor.

In the pursuit of developing advanced nanofiltration membranes with high permeation flux for organic solvents, a TiO2 nanofilm was synthesized via a vapor-liquid interfacial reaction on a flat-sheet α-Al2O3 ceramic support. This process involves the reaction of glycerol, an organic precursor with a structure featuring 1,2-diol and 1,3-diol groups, with TiCl4 vapor to form organometallic hybrid films. Subsequent calcination in air at 250 °C transforms these hybrid films into carbon-doped titanium oxide nanofilms. The unique structure of glycerol plays a crucial role in determining the properties of the resulting nanopores, which exhibit high solvent permeance and effective solute rejection. The synthesized carbon-doped TiO2 nanofiltration membranes demonstrated impressive performance, achieving a pure methanol permeability as high as 90.9 L·m-2·h -1·bar-1. Moreover, these membranes exhibited a rejection rate of 93.2% for Congo Red in a methanol solution, underscoring their efficacy in separating solutes from solvents. The rigidity of the nanopores within these nanofilms, when supported on ceramic materials, confers high chemical stability even in the presence of polar solvents. This robustness makes the carbon-doped TiO2 nanofilms suitable for applications in the purification and recovery of organic solvents.

Organic macromolecules transport a significant proportion of the calcium precursor for nacre formation

The mechanism of nacre formation in gastropods involves a vesicular system that transports organic and mineral precursors from the mantle epithelium to the mineralization chamber. Between them lies the surface membrane, a thick organic structure that covers the mineralization chamber and the forming nacre. The surface membrane is a dynamic structure that grows by the addition of vesicles on the outer side and recedes by the formation of interlamellar membranes on the inner side. By using a combination of electron microscopy imaging and spectroscopy, we have monitored the journey of the vesicles from the mantle epithelium to the mineralization chamber, focusing on the elemental composition of the organic structures at each stage. Our data reveal that transport occurs in lipid bilayer vesicles through exocytosis from the outer mantle epithelium. After release into the surface membrane, chitin undergoes a process of self-assembly and interaction with proteins, resulting in progressive changes of the internal structure of the surface membrane until the final structure of the interlamellar membranes is acquired. Finally, these detach from the inner side of the surface membrane. Elemental analysis revealed the transport of a considerable amount of calcium bound to proteins, likely forming calcium-protein complexes. Statement of significanceThe formation of nacre tablets occurs through the incorporation of organic and mineral precursors extruded from the mantle epithelium. Although much attention has been paid to the presence of amorphous phases in recent decades, the calcium transport system has not yet been elucidated. We have monitored the packaging of organic and mineral precursors in the form of vesicles from the mantle epithelium to the mineralization chamber. We have shown that the surface membrane represents the zone where chitin and protein polymerization takes place, acquiring the final structure for the formation of interlamellar membranes. Interestingly, these organic structures transport a considerable amount of organic calcium into the mineralization chamber, which support a transport system based on acidic calcium-binding proteins.

Carbon nanoarchitecture encapsulated highly dispersed ultrafine Ag particles composite anode for high-capacity desalination

The high capacity of silver (Ag) anodes positions them as a promising avenue for addressing pressing water purification challenges through capacitive deionization (CDI). However, it faces significant challenges such as severe volume expansion and particle crushing, leading to rapid electrochemical failure. Herein, hierarchical hybrid structures comprising highly dispersed ultrafine Ag anchored in carbon nanolayers were prepared using a temperature-mediated strategy. The coordination effect of organic precursors reduces the surface energy of Ag nanoparticles, effectively preventing aggregation during heat treatment. Carbon layer encapsulation synergized with particle size control effectively suppresses the absolute volumetric strain of the electrode in the electrochemical reaction, enhancing electrochemical stability. When used as a CDI anode, AgNC-500 demonstrated an excellent Cl- capturing capacity of 159.96 mg g-1 and a rate of 27.53 mg g−1 min−1. Furthermore, the capacity exhibited excellent stability with negligible degradation over 50 cycles. This study offers crucial insights for advancing the development of highly stable conversion electrodes.

Hydrothermal synthesis and morphological evolution of hexagonal ceria microrod structures

CeriaBTC (CeO2-1,3,5-Benzenetricarboxylic acid) microstructures have been synthesized through hydrothermal methods. Field Emission Scanning Electron Microscopy (FE-SEM) micrographs and X-ray diffraction (XRD) data reveal that the ceria microstructure exhibit hexagonal rod-like structures with average diameters 1.9 ± 0.17 µm and length 5.7 ± 0.19 µm, synthesized at 130 °C for 72 h. Elevating the reaction temperature or duration leads to gradual morphological evolution in micromaterial shape and size (aspect ratio), stabilizing at 3.51. This signifies an ongoing chemical transformation driving morphological alteration. Fourier transform infrared spectroscopy (FT-IR) reveals the presence of an organic linker in the CeriaBTC microrods. Results from XRD, FE-SEM, FT-IR, and thermogravimetric analysis (TGA) suggest a chemical transformation from hexagonal type CeriaBTC to Ceria microrods at higher calcination temperatures of 400 °C for 4 h. The development of hierarchical morphologies, transitioning from hexagonal CeriaBTC rods to ceria microstructure powder, has been observed to rely on both the orientation of the organic precursor (1,3,5-Benzenetricarboxylic acid) and the specific calcination temperature applied.

Air-Processed Efficient Perovskite Solar Cells With Full Lifecycle Management.

Despite the outstanding power conversion efficiency of perovskite solar cells (PSCs) realized over the years, the entire lifecycle from preparation and operation to discarding of PSCs still needs to be carefully considered when it faces the upcoming large-scale production and deployment. In this study, bio-derived chitin-based polymers are employed to realize the full lifecycle regulation of air-processed PSCs by forming multiple coordinated and hydrogen bonds to stabilize the lead iodide and organic salt precursor inks, accelerating the solid-liquid reaction and crystallization of two-step deposition process, then achieving the high crystalline and oriented perovskites with less notorious charge defects in the open air. The air-prepared PSCs exhibit a decent efficiency of 25.18% with high preparation reproducibility and improved operational stability toward the harsh environment and mechanical stress stimuli. The modified PSCs display negligible fatigue behavior with keeping 92% of its initial efficiency after operating for 32 diurnal cycles (ISOS-LC-1 protocol). Meanwhile, closed-loop lead management of end-of-life PSCs including suppression of lead leakage, toxicity evaluation of broken devices, and recycling of lead iodide components are comprehensively investigated. This work sheds light on a promising avenue to realize the entire lifecycle regulation of air-processed efficient and stable PSCs.

Solvent mediated synthesis of multicolor narrow bandwidth emissive carbon quantum dots and their potential in white light emitting diodes

The development of efficient and environmentally sustainable materials for white light-emitting diodes (WLEDs) is of paramount importance in the field of lighting technology. In this study, we present a solvent-modulated synthesis approach for the fabrication of multicolor narrow-bandwidth emissive carbon quantum dots (CQDs) as a promising solution for constructing WLEDs. The synthesis method involves the controlled reaction of organic precursors in different solvent environments, leading to the formation of CQDs with distinct emission wavelengths with a relatively small full width at half maximum, ranging from 28 to 42 nm. Moreover, these synthesized multicolor CQDs demonstrate a remarkably high fluorescence quantum yield of up to 65%, indicating their potential for constructing efficient WLED when incorporated in polymer matrix and coated on the surface of blue light-emitting diode (LED).

Effect of 4,4′-dialkyl-2,2′-bipyridine ligands on the hydrolysis of dichlorodioxomolybdenum(VI) catalyst precursors and the switch from homogeneous epoxidation to heterogeneous systems

Molybdenum catalysts have been industrially recognized for decades for liquid phase epoxidation, which is an important chemical reaction process, since epoxides are used for many industrial applications. In this work, molybdenum oxide hybrid catalysts, prepared by a reflux hydrolysis methodology, performed effectively as heterogeneous catalysts or reaction-induced self-separating catalysts under mild reaction conditions; in the two cases, the catalyst separation and reuse are facilitated. Specifically, catalysts with the general formula [MoO3(L)], possessing polymeric chain-like (L = 4,4′-dimethyl-2,2′-bipyridine (1)) or oligomeric (L = 4,4′-dinonyl-2,2′-bipyridine (2)) structures comprising corner-sharing {MoO4N2} units, were synthesized and characterized by various complementary techniques (ATR FT-IR, Raman, 13C{1H} CP MAS NMR spectroscopy, PXRD, SEM, TGA, elemental analysis, ICP-OES and N2 sorption isotherms). Small chemical differences in the organic synthesis precursor had important structure directing effects on the type of hybrid material formed. The hybrids promoted olefin epoxidation with H2O2 or tert-butylhydroperoxide (TBHP) as oxidant. For example, 1 catalyzed the conversion of biobased olefins (70 °C) and lignin-based isoeugenol (50 °C) with TBHP to useful bioproducts, in heterogeneous phase, leading to an epoxide yield of 100 % for DL-limonene (3:1 M molar ratio of 1,2-epoxy-p-menth-8-ene to 1,2:8,9-diepoxy-p-menthane), 81 % epoxide yield for fatty acid methyl esters, and 80 % Licarin A selectivity at 40 % isoeugenol conversion. For dienes (DL-limonene, methyl linoleate), kinetic modelling studies suggested that the formation of the monoepoxides was faster than that of diepoxides, accounting for enhanced monoepoxide selectivity.

Occurrence, toxicity, and control of halogenated aliphatic and phenolic disinfection byproducts in the chlorinated and chloraminated desalinated water

Seawater desalination is widely used to overcome the freshwater shortage worldwide. However, even after three-stage reverse osmosis treatment, the desalinated water still contained 14.6 μg/L of aliphatic disinfection byproducts (DBPs), 384.2 ng/L of bromophenolic DBPs, 3.5 ng/L of iodophenolic DBPs, 1024.7 μg/L of Br-, 2.8 μg/L of I-, and 2.4 mg C/L of dissolved organic carbon (DOC). After the desalinated water was disinfected with chlor(am)ine, the concentrations of halogenated aliphatic and phenolic DBPs further increased, and bromophenolic DBPs were the toxicity forcing agents. When surface water was mixed with desalinated water and then chlorinated, the yield of aliphatic and phenolic DBPs significantly elevated. Separately chlorinating desalinated water and surface water before mixing could mitigate this adverse situation. Chloramine disinfection was more conducive to reducing the total calculated toxicity of disinfected desalinated waters and mixed waters compared to chlorine disinfection. The treatment of desalinated water with granular activated carbon could effectively remove DOC and UV254, leading to a reduction in the content of total organic halogen after chlor(am)ination. Although anion exchange resin could adsorb Br-, it also released the organic precursors of DBPs, ultimately increasing the yield of DBPs. The results of this study can provide a reference for the seawater desalination industry to improve seawater pre-treatment and desalination processes and thus minimize the DBPs.

C60–bicyclo[2.2.1]heptanes: new hybrid mono- and hexakis-adducts of the C60 fullerene

New fullerene derivatives keep attracting attention of chemists due to their possible applications. Fullerene adducts with saturated polycyclic hydrocarbons represent one of the promising classes of fullerene compounds but still have rare examples. To enhance molecular diversity of fullerene derivatives in this direction, we have synthesized the representatives of C60–bicyclo[2.2.1]heptanes. For this purpose, we first produced the unsubstituted organic hydrazones from various bicyclo[2.2.1]heptane derivatives and then used the organic precursors in the reactions with C60. New homofullerenes and methanofullerenes with one bicyclo[2.2.1]heptane fragment have been obtained under metal-complex catalysis conditions at the fullerene C60:hydrazone molar ratio equal to 1:1.5. If fullerene C60:hydrazone ratio was 1:10, homofullerenes with six bicyclo[2.2.1]heptane fragments were synthesized, which can be isomerized into methanofullerenes when boiling in o-dichlorobenzene.

Fast and scalable preparation of metal–organic coordination polymeric precursor for bifunctional electrocatalysts for high performance lithium–oxygen batteries

The Metal-organic coordination polymers (MOCPs) with structural and functional diversity are considered effective cathode materials for Lithium-oxygen batteries (LOBs). Conventional synthesis methods make it difficult to obtain large quantities of materials. Here, A highly active low-cost Co-decorated N-doped carbon oxygen cathode catalyst (Co–N–C) was synthesized using a fast and scalable method based on positive and negative charge coordination. Rapid synthesis of MOCPs depends on the addition of base sites. A theory of “Lewis’s base-assisted rapid synthesis” was proposed. Co-N-C as LOBs air cathode showed 150 cycles with 1000 mAh g-1 at 500 mA g-1. The fast and scalable synthesis method can provide a feasible strategy for large-scale production of oxygen electrocatalysts for LOBs.

Molecular–level insights into the synergistic activation of peracetic acid by ultraviolet and ferrous ions for the degradation of sedimentation sludge water in drinking water treatment plants based on Fourier transform-ion cyclotron resonance mass spectrometry

Sedimentation sludge water (SSW) from sedimentation tanks in drinking water treatment plants contains significant amounts of dissolved organic matter (DOM) and precursors of disinfection byproducts, raising increasing concerns about the safety of finished water following SSW recycling. This study explores the alterations in bulk properties and molecular characteristics of DOM in SSW treated with ultraviolet (UV)/ferrous ions (Fe2+) and peracetic acid (PAA) using fluorescence spectroscopy and Fourier transform ion cyclotron resonance mass spectrometry (FT–ICR MS). The primary reactive species, hydroxyl radicals (·OH) and acylperoxy radicals (CH3C(O)OO·) achieved degradation rates of up to 82.0%, eliminating 84.5% of total fluorescent components and reducing molecular intensity and apparent molecular count by 90.9% and 69.8%, respectively. This treatment significantly reduced the aromaticity of DOM, leading to the formation of more oxidized and stable compounds. Reaction mechanisms indicate that ·OH and CH3C(O)OO· primarily facilitate oxygen addition and dehydrogenation, while CH3C(O)OO· promotes decarboxylation through weak electron transfer processes. The treatment preferentially removes complex DOM containing nitrogen and sulfur heteroatoms, which are key precursors of disinfection byproducts. These findings enhance our understanding of DOM transformations during UV/Fe2+/PAA treatment and provide valuable insights into the safe recycling of SSW.

Insights Into the Influence of Anthropogenic Emissions on the Formation of Secondary Organic Aerosols Based on Online Measurements

AbstractTo investigate the combined impacts of anthropogenic and biogenic emissions on the formation of secondary organic aerosols (SOA), SOA molecular tracers, their corresponding volatile organic compound precursors, and other air pollutants were measured online during the winter and summer seasons of 2022 in an industrial city, Zibo, China. The results indicate that the average concentrations of SOA tracers were 16.1 ± 9.8 ng m−3 in winter and 99.4 ± 57.2 ng m−3 in summer. During winter, anthropogenic SOA (ASOA, the sum of SOA derived from naphthalene and mono‐aromatic volatile organic compounds) dominated, whereas isoprene SOA (SOAI) prevailed in summer. Correlation analysis between SO42− and both SOAI and high‐order monoterpene SOA tracers (SOAM‐H) (R = 0.46–0.72, p &lt; 0.001) revealed that higher aerosol acidity facilitated the formation of SOAI and SOAM‐H, with SO2 emissions playing a significant role in leading to higher acidity. Most biogenic SOA (BSOA) tracers exhibited a significant positive correlation with NO3−, particularly in winter, implying the remarkable influence of NOx emissions on BSOA formation. The levels of BSOA tracers increased with NH3, indicating that NH3 can enhance the formation of BSOA. In summer, SOA formation correlated with Ox (Ox = O3 + NO2), indicating the substantial impact of atmospheric oxidizing capacity on SOA formation. During winter, aerosol liquid water content (ALWC) correlated well with SOAI tracers (i.e., 3‐hydroxyglutaric acid (3‐HGA) and 3‐hydroxy‐4,4‐dimethylglutaric acid (3‐HDMGA)), and 2,3‐dihydroxy‐4‐oxopentanoic acid (DHOPA) (R &gt; 0.5, p &lt; 0.001), indicating the important contribution of aqueous‐phase formation of SOA. These findings underscore the significant role of anthropogenic pollutant emissions in the formation of ASOA and BSOA in urban environments.

Block Copolymers‐Enabled Organic–Organic Assembly for Unique Carbonaceous Micro‐/Nano‐Structures

AbstractOver the past decade, there has been growing research interest in deriving advanced carbonaceous materials with unique architectures, including diverse morphologies and compositions, from polymer‐based precursors with tailored nano/micro‐structures. The organic–organic assembly between organic molecules and block copolymers (BCPs) has emerged as a promising strategy for advancing the preformed polymers with multiple levels of complexity. This review provides a comprehensive overview of the synthesis and potential applications of unique carbonaceous nano/micro‐structures derived from commonly used organic precursors, including phenol/formaldehyde, dopamine, and biomass. It begins with a brief summary of the polymerization mechanism for each type of precursors. Following this, it details the delicate design and preparation strategies for unique polymer architectures, including the formation mechanisms of the first‐level assembly involving BCPs and organic precursors, which form composite micelles as building units, and the principles for manipulation the higher‐level assembly process of the composite micelles, illustrated with some representative examples. The review then highlights the advanced applications of these materials in heterogeneous catalysts, secondary batteries, separation, and intelligent drug delivery systems. Finally, the synthetic challenges and potential development directions of unique carbonaceous nano/micro‐structures are outlined, underscoring a pathway for developing advanced materials.

Role of Organic Vapor Precursors in Secondary Organic Aerosol Formation: Concurrent Observations of IVOCs and VOCs in Guangzhou

AbstractSecondary organic aerosol (SOA) formed through the atmospheric transformation of organic vapors constitutes a significant portion of fine particulate matter or PM2.5. While recent laboratory studies underscore the importance of intermediate‐volatility organic compounds (IVOCs) as key precursors to SOA, field observations that recognize the role of both volatile organic compounds (VOCs) and IVOCs in SOA formation remain scarce. In this study, we conducted concurrent measurements of VOCs and IVOCs in ambient air at urban and suburban sites in Guangzhou during a PM2.5 pollution event in winter 2021. The results reveal that between 12:00–15:00 local time, the photochemically adjusted initial concentrations of VOCs at both sites were approximately 7 times higher than that of IVOCs. However, the SOA formation potential (SOAFP) of primary hydrocarbon IVOCs exceeded that of VOCs by over 3–4 times. Receptor modeling results further indicated that while ship emissions contributed to less than 10% of the C2–C22 primary hydrocarbons concentration (VOCs + primary carbonaceous IVOCs), they accounted for the most significant source (approximately 40%) of SOA formation. This study highlights the substantial role of IVOCs in SOA formation and emphasizes the importance of future PM2.5 pollution control measures targeting major IVOCs contributors, such as ship emissions in harbor cities.

Periodic membrane fractionation of freshwater organic matter reveals various reactivity patterns during chlorine/chloramine disinfection

Although drinking water disinfection has significantly reduced mortality from waterborne diseases, the formation of potentially harmful disinfection by-products (DBPs) remains a concern today. These DBPs emerge from the reaction of dissolved organic matter (DOM) with chlor(am)ine during disinfection. Identifying these DBP precursors from heterogeneous and complex DOM mixtures is challenging and to address this, a novel membrane fractionation protocol was developed to isolate and identify the organic DBP precursors from fresh water sources. A tight ultrafiltration and nanofiltration membrane were carefully selected to partition DOM into three molecular weight (MW) fractions: high (>20 kDa), medium (0.3–20 kDa) and low (<0.3 kDa) as defined by high performance-size exclusion chromatography- total organic carbon analysis. A mathematical tool was developed to optimize the fractionation protocol. Therefore, ultrafiltration was executed before nanofiltration and the concentration factor was maximized without inducing fouling to obtain the purest fractions. The mathematical tool was also set in place to predict the necessary diafiltration factor for each individual fractionation experiment based on the initial organic matter composition of the surface water allowing the fractionation protocol to be effective at all times. The protocol was applied to surface water samples collected six times across three seasons yielding a fraction enriched in high MW compounds (up to 50 %), a fraction having more than 80 % of medium MW compounds and a fraction only containing low MW compounds. Although the medium MW fraction showed the highest reactivity for the majority of the investigated DBPs, the low MW fraction showed high reactivity for iodinated trihalomethanes during chlorination and for haloacetonitriles during chloramination. The high MW fraction had the lowest reactivity towards DBPs, which can have important implications for a drinking water treatment since this fraction is generally the most effectively removed by e.g. coagulation, while the more important fractions for DBP formation such as the medium and low MW compounds remain in the water until the disinfection step.