Guangzhou Institute of Geochemistry
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Polyhalogenated carbazoles in the environment: Analysis, origins, occurrence, and toxicity
No full textPolyhalogenated carbazoles are a class of emerging organic compounds characterized by the substitution of one to eight hydrogen atoms in the carbazole structure with halogen atom(s). Polyhalogenated carbazoles originate from natural and anthropogenic sources and are widely distributed in the environment. They are persistent in the environment and present a range of toxic effects, notably dioxin-like activity. This review focused on recent progress in determining their distribution, analytical methodologies, toxicity, origins, and transformation in the environment, highlighting their potential ecological and health risks. It confirmed the critical need for ongoing research regarding their environmental behavior and fate, to ensure a comprehensive understanding of the resulting environmental risks. This review also identified future research needs regarding these compounds
Identification of Hydroxylated Chlorinated Paraffins in Human Serum and Their Potential Metabolic Pathways
No full textShort- and medium-chain chlorinated paraffins (SCCPs and MCCPs) are frequently detected in humans. However, information regarding their metabolites is still very limited. Herein, target analysis and halogenation-guided nontarget and suspect screening were conducted on serum samples using UHPLC-Orbitrap-HRMS. The median concentrations of SCCPs and MCCPs were 7.76 and 4.31 ng/mL, respectively. A series of hydroxylated chlorinated paraffins (OH-CPs) were tentatively identified with an estimated average concentration of 1.80 ng/mL, which was approximately 9.9% of the total SCCPs and MCCPs. A chlorine distribution shift was observed from chlorinated paraffins (CPs) dominated by Cl6 and Cl7 to OH-CPs dominated by Cl5, Cl6, and Cl4. In human liver cytochrome P450 (CYP) enzyme incubation assays, the CPs in commercial mixtures were mainly metabolized into OH-CPs with various carbon lengths and chlorine substituents. The results obtained from human serum and in vitro experiments suggested the oxidative metabolism of SCCPs and MCCPs in humans. The metabolic pathways were then comprehensively explored using a CP monomer (1,1,1,3,10,11-hexachloroundecane) incubated with the same CYP enzymes, demonstrating that CPs can be metabolized through successive oxidative dechlorination and direct hydroxylation, with subsequent oxidation to carboxylic acids. Further studies should focus on the long-term toxicity of OH-CPs
Molybdenum isotope evidence for subduction-modified mantle beneath mid-ocean ridges
No full text"Ghost" arc geochemical signatures persistently occur in mid-oceanic ridge basalts (MORBs), yet their origin remains elusive. Here, we identified arc-like heavy Mo isotopic compositions in basalts from the St. Helena plume-influenced southern Mid-Atlantic Ridge. Their heavy Mo isotopic signature (delta 98/95Mo = -0.21 %o to +0.11 %o), along with relatively low (La/Sm)N, Nb/Zr, Ce/Pb, and Sr-Nd isotope ratios, cannot be explained by interactions of the depleted mantle with recycled crustal or lithospheric mantle materials or the influence of the St. Helena plume on their mantle source. By integrating seismic tomographic images and plate reconstruction models, we interpret these unique geochemical and heavy Mo isotopic signatures to reflect the inputs of fluidmodified mantle produced during the Mesozoic subduction beneath the southwestern Gondwana convergent margin. Our discovery provides crucial evidence for the role of the paleo-subduction-modified mantle in shaping present-day MORB-mantle heterogeneity and sheds light on the formation of ghost-arc signatures in global MORBs
Martian Smectites Formation Regulated by Environmental CO<sub>2</sub> and Si
No full textDespite the anticipated abundant carbonates due to historical atmospheric CO2 levels, Mars presents a geological puzzle with MgFe-smectites dominating the Noachian and early Hesperian terrains, contrasted by sparse carbonate deposits. To address this point, we explored the impact of CO2 on MgFe-smectite formation, emphasizing the role of variable Si concentrations within the simulated Martian environment. Hydrothermal experiments, conducted under a constant CO2 concentration (C0.5) and varying Si concentrations (Si0.5 to Si4), reveal a transformation from pyroaurite to MgFe-smectite via lizardite as an intermediary phase. This transformation underscores the crucial role of Si in this mineral sequence. Notably, experiments demonstrate that the interlayer CO32- in pyroaurite is released into aqueous environments during the mineral conversion, potentially impacting the Martian CO2 budget. These findings could explain isolated carbonate outcrops and the possibility of hydrotalcite-group minerals on Mars today. Further Mars exploration should consider identifying hydrotalcite-group minerals for their implications on the planet's climate and habitability
Mechanistic insights into highly efficient oxygenation of 5-hydroxyme-thylfurfural to 2,5-furandicarboxylic acid over natural sepiolite-supported bimetallic PdAu catalysts
No full textThe oxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is an important reaction for the production of value-added chemicals from biomass. However, developing highly efficient and stable catalysts for this process remains challenging. Sepiolite (Sep)-supported bimetallic PdAu catalysts were prepared for the selective oxygenation of HMF to FDCA. 1Pd1Au4/Sep catalyst exhibited the highest catalytic activity, reaching 100 % HMF conversion and 97 % FDCA yield after 10 min, with outstanding formation rate of FDCA of 2560.72 mmol center dot g- 1 center dot h- 1. This excellent catalytic performance is attributable to rich surface active sites on PdAu/Sep. High specific surface area and special porous structure of Sep can enable its unique adsorption capacities for reactants. Importantly, there are oxygen vacancies (Ov) on surface of Sep, which promotes the activation of O2. What's more, the metal catalytically active sites of PdAu alloy nanoparticles efficiently facilitated the oxygenation of HMF to FDCA. In particular, the kinetic results further reveal that the synergistic effects between Pd and Au accelerated the oxidation of 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). Additionally, the 1Pd1Au4/Sep catalyst had high stability and reusability, without loss of activity after five runs. This study reveals the catalytic mechanisms of the Sep-supported PdAu catalysts for the efficient oxygenation of HMF to FDCA
Microwave Digestion for Re-Os Isotope Measurements in Geological Samples
No full textIn this study, we present the novel use of a microwave digestion system (CEM BLADE) to digest geological materials for Re-Os isotopic analysis. This technique employs quartz digestion vessels that are easy to clean and reusable, avoid the complicated steps of opening and sealing, and enable complete digestion of the samples within 30 min at high temperature (max. 310 degrees C) and pressure (max. 700 psi). The microwave digestion system was used to digest samples of four ultramafic rock reference materials (GBW07101, GBW07102, GBW07291, and WPR-1a), one basalt reference material (BIR-1a), and one black shale reference material (SGR-1b). The Re-Os isotope measurement results for GBW07291, BIR-1a, and SGR-1b were in agreement with previously published values, and we are the first to report Re-Os isotopes for GBW07101, GBW07102, and WPR-1a. Therefore, this new microwave digestion system is a simple, efficient, reliable, and safe sample digestion method for prospective applications in Re-Os isotopic analysis
Biogenic emission as a potential source of atmospheric aromatic hydrocarbons: Insights from a cyanobacterial bloom-occurring eutrophic lake
No full textAs important precursors of ozone (O3 ) and secondary organic aerosol (SOA), reactive aromatic hydrocarbons (AHs) have typically been classified as anthropogenic air pollutants. However, biogenic emission can also be a potential source of atmospheric AHs. Herein, field observations in a eutrophic lake were combined with laboratory incubation experiments to investigate the biogenic AH emission. Field work showed that the water-air fluxes of AHs measured at sites with high cyanobacteria abundance could reach an order of magnitude greater than those at sites with low cyanobacteria abundance, suggesting that cyanobacteria could be the important contributor to measured AHs. Laboratory incubation experiments further confirmed the AH emission of cyanobacteria and revealed that the emission could change significantly over the lifespan of cyanobacteria and varied to their growing conditions. By combining field observations and laboratory incubation experiments, it has been suggested that the emission of different AH species from cyanobacteria could be modulated by variable biogeochemical mechanisms and that the biochemical process of toluene could be different from that of other AHs. This study investigates AH emissions from inland aquatic ecosystem and suggests that biogenic emission could be a potential source of atmospheric AHs. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
A comparative study on the formation of nitrogen-containing organic compounds in cloudd roplets and aerosolp articles
No full textNitrogen-containing organic compounds (NOCs)maypotentiallycontributetoaqueoussec-ondaryorganicaerosols,yet the different formationofNOCsinaerosolparticlesand clouddropletsremainsunclear. With the in-situmeasurementsperformedatamountainsite(1690ma.s.l.)in southernChina,weinvestigatedtheformationofNOCsintheclouddropletsandthecloud-freeparticles,basedontheirmixingstateinformationofNOCs-containingparticlesbysingleparticlemassspectrometry.TherelativeabundanceofNOCsinthecloud-freeparticleswassignificantlyhigherthanthoseincloudresidual(cloudRES)particles.NOCswerehighlycorrelatedwithcarbonylcompounds(includingglyoxalateandmethylglyoxal)inthecloud-freeparticles,however,limitedcorrelationwasobservedforcloudRESparticles.AnalysisoftheirmixingstateandtemporalvariationshighlightsthatNOCswasmainlyformedfromthecarbonylcompoundsandammoniuminthecloud-freeparticles,ratherthaninthecloud RES particles.Theresultssupportthattheformation of NOCsfromcarbonylcompoundsisfacilitatedinconcentratedsolutionsinwetaerosols,ratherthanclouddroplets.In addition,we have identified the transport of biomass burnin
A water probe for direct pH measurement of individual particles via micro-Raman spectroscopy
No full textThe acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health. We recently developed a novel and facile water-probebased method for directly measuring of the pH for micrometer-size droplets, providing a promising technique to better understand aerosol acidity in the atmosphere. The complex chemical composition of fine particles in the ambient air, however, poses certain challenges to using a water-probe for pH measurement, including interference from interactions between compositions and the influence of similar compositions on water structure. To explore the universality of our method, it was employed to measure the pH of ammonium, nitrate, carbonate, sulfate, and chloride particles. The pH of particles covering a broad range (0-14) were accurately determined, thereby demonstrating that our method can be generally applied, even to alkaline particles. Furthermore, a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe. The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects. Using the spectral library, all ions were identified and their concentrations were determined, in tum allowing successful pH measurement of multicomponent (ammonium-sulfate-nitrate-chloride) particles. Insights into the synergistic effect of Cl-, NO3 -, and NH4 + depletion obtained with our approach revealed the interplay between pH and volatile partitioning. Given the ubiquity of component partitioning and pH variation in particles, the water probe may provide a new perspective on the underlying mechanisms of aerosol aging and aerosol-cloud interaction. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V
Organosulfur Compounds: A Non-Negligible Component Affecting the Light Absorption of Brown Carbon During North China Haze Events
No full textThe roles of organosulfur compounds (OSCs), an important component in organic matter, in brown carbon (BrC) aerosol absorption is often overlooked. Here, the molecular composition of OSCs and its associations with methanol-soluble BrC (MS-BrC) absorption during a haze event in North China were revealed using a Fourier transform ion cyclotron resonance mass spectrometry analysis. By combining aggregated boosted tree model and partial least squares regression estimation, our results suggested that OSCs were mainly composed of potential aromatic structures, and the MS-BrC absorption was closely related to OSCs. Specifically, OSCs contribute a notable 26% of the total potential BrC molecular number and an upper limit of 10.4% of total MS-BrC absorption. Furthermore, we found that OSCs were mainly influenced by coal combustion, and the potential desulfurization reactions showed associations with the variations of MS-BrC absorption. Since the residential coal combustion (an important primary source of OSs) was the major energy in North China, our research underscores the potential of aromatic OSCs as tracers for assessing the impact of fossil fuel combustion on BrC and highlights the important atmospheric influences of OSCs (e.g., light absorption and health), which need more works to uncover the origins, fates, and environmental effects of OSCs