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Iron (hydr)oxides as a kind of natural mineral actively participate in the transformation of organic pollutants, but there is a large knowledge gap in their impacts on photochemical processes of microplastics (MPs). This study is the first to examine the degradation of two ordinary plastic materials, polyethylene (PE) and polypropylene (PP), mediated by iron (hydr)oxides (goethite and hematite) under simulated solar light irradiation. Both iron (hydr)oxides significantly promoted the degradation of MPs (particularly PP) with a greater effect by goethite than hematite, related to hydroxyl radical (

Reactive oxygen species (ROS) play key roles in soil biogeochemical processes, yet the occurrence and accumulation of ROS in the rhizosphere are poorly documented. Herein, we first developed a ROS-trapping membrane to

Understanding the effects of halogens on the production of macromolecular disinfection byproducts (DBPs) is critical for drinking water safety. The effects of Br

Environmental persistent free radicals (EPFRs) have been evaluated as a new kind of environmental risk substance, which are mainly detected in atmospheric particles and superfund sites. Clay minerals, which are composed of layered silicates and are abundant in soil environment, provide an appropriate site for organic pollutants to form EPFRs. Our previous studies showed that combination of clay minerals and transition metal species such as Fe and Cu ions/oxides can effectively degrade polycyclic aromatic hydrocarbons (PAHs), and significant EPFRs signal can be detected by electron paramagnetic resonance (EPR). Aluminum (Al) is the most abundant metal element in the earth’s crust, however, to the best of our knowledge, few studies have reported the formation of EPFRs by organic pollutants contaminated Al(III)-clay minerals, and an unambiguous of the relevant interface process and mechanism is still lacking. In this paper, benzo[a]pyrene (B[a]P), a strong carcinogenic PAHs compound, was used to contaminate Al(III)-montmorillonite, and Na(I)-montmorillonite served as the control group. The degradation rate of B[a]P was determined by high performance liquid chromatography (HPLC). Fourier transform Infrared spectrometer (FTIR) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the changes of functional groups and elements in the course of degradation of B[a]P. Since water content is an important factor in soil, three different relative humidity (RH) conditions (RH 97%) were selected to explore the stability of B[a]P-EPFRs. In order to confirm that the formation of EPFRs was accompanied by generation of hydroxyl radical (•OH) and superoxide radical (O2 · −), reactive oxygen species (ROS) capture experiment and radical quenching experiment were carried out. The results confirmed that Al(III)-montmorillonite was capable of accelerating the degradation of B[a]P, and the reaction rate was 37 times higher than that of Na(I)-montmorillonite. FTIR characterizations showed that the decay of old functional groups (C=C) was accompanied by forming new functional groups (C=O). XPS analysis revealed that upon sorption the ‒C=O band and C=O band occurred by analyzing the C 1s and O 1s, indicating the formation of oxygen-containing compounds. The RH experiment demonstrated that the conversion of B[a]P and the formation of EPFRs were not affected under relatively dry conditions (RH · − radical respectively, and the degradation rate of B[a]P was decreased significantly to 19.1% and 23.4% at 9 d respectively. In addition, the EPR intensity of EPFRs was obvious decreased, and this indicated that the formation of EPFRs was accompanied by the generation of ROS. The degradation of B[a]P and the formation of EPFRs were mainly attributed to electron transfer on the surface of Al(III)-montmorillonite. The formed •OH and O2 · − radical in the system can oxidize B[a]P radicals and eventually generate oxygen-containing compounds.

Environmentally persistent free radicals (EPFR) are emerging contaminants of health concern. Their levels in the environment are not well known because few studies have optimized EPFR extraction. Therefore, here we studied the extraction and decay of EPFR that are formed on the surfaces of Cu(II)-montmorillonite clay contaminated by polycyclic aromatic hydrocarbons (PAH) including benzo[a]pyrene and anthracene. EPFR were analyzed by electron paramagnetic resonance. Results show that acetone or dichloromethane/acetone effectively extract benzo[a]pyrene-EPFR. By contrast, CCl4, acetonitrile or methanol do not extract benzo[a]pyrene-EPFR, but extract residual benzo[a]pyrene at 62.2% for CCl4, 77.8% for acetonitrile and 59.1% for methanol. EPFR concentration decreases with ultrasonic intensity and time, from 60 s at 16 kHz to 1200 s at 40 kHz. The decay of PAH–EPFR in acetone displays two steps, a fast decay from 0 to about 5 h, then a slower decay from 5 to 50 h. The 1/e lifetime during the slow decay period was about 168 h for benzo[a]pyrene-EPFR and 180 h for anthracene-EPFR.

The traditional cook stove is a major contributor to combustion-derived soot particles, which contain various chemical species that may cause a significant impact to human health and ecosystems. However, properties and toxicity associated with environmentally persistent free radicals (EPFRs) in such emissions are not well known. This paper investigated the characteristics and cytotoxicity of soot-associated EPFRs discharged from Chinese household stoves. Our results showed that the concentrations of EPFRs were related to fuel types, and they were higher in wood-burning soot (8.9-10.5 × 1016 spins/g) than in coal-burning soot (3.9-9.7 × 1016 spins/g). Meanwhile, EPFR concentrations in soot decreased with an increase of coal maturity. The soot EPFRs, especially reactive fractions, readily induced the generation of reactive oxygen species (ROS). Potential health effects of soot EPFRs were also examined using normal human bronchial epithelial cell line 16HBE as a model. Soot particles were internalized by 16HBE cells inducing cytotoxicity. The main toxicity inducers were identified to be reactive EPFR species, which generated ROS inside human cells. Our findings provided valuable insights into potential contributions of soot EPFRs associated with different types of fuel to health problems. This information will support regulations to end or limit current stove usage in numerous households.

Indometacin (IDM), as a kind of non-steroidal anti-inflammatory drugs, has ecological and health risks, which is the potential precursor of chlorination disinfection byproducts (DBPs). Non-thermal discharge plasma was attempted to eliminate IDM and control subsequent DBPs formation. Satisfactory removal performance for IDM was realized by the plasma oxidation; almost 100% of IDM was removed within 2 min. Relatively greater removal efficiency was gained at a higher plasma voltage and a lower pH level. Electron paramagnetic resonance spectrometer revealed that reactive species ·OH, O

Natural attenuation is a major ecosystem function allowing to abate soil organic contaminants such as polycyclic aromatic hydrocarbons (PAHs). Biodegradation of PAHs is classically considered as the major driver of natural attenuation, yet the role of abiotic transformation, including photodegradation, chemical oxidation, formation of non-extractable residues, and polymerization, has been overlooked due to the lack of investigations until recently. This paper reviews PAHs dissipation in soils by abiotic processes such as photodegradation and oxidation catalyzed by inorganic minerals and organic matters. The role of soil components on degradation rates, pathways, and mechanisms are discussed. The products of PAHs abiotic transformation and their potential risks are also described. Abiotic transformations are mainly controlled by interactions between PAHs and clay minerals, metal oxides/hydroxides, and soil organic matter. PAH photodegradation proceeds by both direct and indirect photolysis processes, which are enhanced in the presence of natural photosensitizers, for example, organic matter, and photocatalysts, for example, metal oxides/hydroxides. PAHs can also be chemically/catalytically oxidized by metal oxides/hydroxides, for example, MnO2, FexOy, and clay minerals without light irradiation. Overall, PAHs transformation depends on their electron-donating properties, mineral electron-accepting properties, pH, temperature, moisture, and oxygen content. Following the elucidation of the transformative mechanism, knowledge to understand the impact of abiotic transformation on biodegradation are delineated. Future investigations are needed to advance the correlation of laboratory generated rates to the field applications, and the potential applications of natural attenuation based on abiotic processes are proposed.

Carbon-derived dissolved organic matter (CDOM) are inevitably released to surface water during returning agricultural biomass carbon to farmland, which are potential precursors of disinfection byproducts (DBPs). In this study, CDOM was extracted from aerobic incineration ("OX") and anoxic pyrolysis ("PY") of three kinds of straw (wheat, corn, and rice), and the emerging DBPs from them were deciphered. The CDOM with molecular weight1 kDa in the OX and PY groups accounted for 53-87%, and it was higher in the PY group. A total 1343-2107 of CHO and 641-1761 of CHNO formulas were detected in the CDOM derived from the OX group, among which 74%-83% contained aromatic structures rich in oxygen containing groups. 1919-3289 of CHO and 785-1954 of CHNO formulas were observed in the PY group, and 77%-86% of them were lignins/CRAM-like compounds. Surprisingly, 765-2158 and 895-1648 of emerging DBPs were identified in the OX and PY groups, and the proportions of N-DBPs were 20.3-54.8% and 2.8-4.8%, respectively. Based on HOCl addition and Cl substitution mechanisms, the H/C ratios of the DBP precursors in the OX and PY groups were in the range of 0.2-1.5 and 0.6-2.0, respectively. The DBPs derived from the OX group exhibited higher cytotoxicity and genotoxicity due to the higher aromaticity and more N-DBPs. Thus, returning agricultural biomass carbon, particularly that produced by direct combustion, to farmland brought potential threat to drinking water safety.

The application of parathion (PTH) in agriculture can result in its entry into the soil and threaten the soil environment. Monitoring the PTH residues and assessing toxicity on soil health are of paramount importance to the public. Herein, the dissipation of PTH and concomitant influence on microbial activities [FDA hydrolase (FDA‒H), microbial biomass carbon (MBC) and basal respiration (BR)] in coastal solonchaks were investigated. Results showed that the dissipation of PTH in tested soil declined linearly, and the half-lives varied from 5.6 to 56.8 days, depending on pollutant concentrations. The FDA‒H activity and MBC were negatively affected by PTH pollution and exhibited a significantly positive correlation. Two‒way ANOVA analysis demonstrated that microbial activities were affected not only by PTH dose and incubation time but also by their interactions. The integrated biomarker response (IBR/n) index values on day 120 were between 1.02 and 2.89, larger than those on day 1 during PTH dissipation. This implied that the soil quality did not recover though there was no PTH residue in the soil at the end of the experiment. These findings suggested that microbial activities integrated with IBR/n index could elucidate the hazardous impacts of PTH dissipation on biochemical cycling and microorganisms in soil.

Nitrogen-containing microplastics (N-MPs) are widely present in the atmosphere, but their potential health risks have been overlooked. In this study, the formation of persistent aminoxyl radicals (PAORs) and reactive nitrogen species (RNSs) on the N-MPs under light irradiation was investigated. After photoaging, an anisotropic triplet with the g-factor of ∼2.0044, corresponding to PAORs, was detected on the nonaromatic polyamide (PA) rather than amino resin (AmR) by electron paramagnetic resonance and confirmed by density functional theory calculations. The generated amine oxide portions on the photoaged PA were identified using X-ray photoelectron spectroscopy and Raman spectroscopy, which were considered to be the main structural basis/precursors of a PAOR. Surprisingly, RNSs were also observed on the irradiated PA. The generated ·NO due to the aphotolysis of nitrone groups simultaneously reacted with peroxide radicals and O

The photo-transformation of microplastic (MP) in natural water may involve interactions with various ingredients, but the photoaging kinetics and underlying mechanism are not well understood. This work systematically explored the photoaging process of polystyrene microplastic (PS-MP) in the presence of commonly-found inorganic anions, including NO

Environmentally persistent free radicals (EPFRs) as intermediate products exist widely in the PAHs-contaminated soils, but toxicity assessment associated with EPFRs for terrestrial invertebrates remains unclear. Using the model organism Eisenia fetida, we compared the adverse effects among anthracene (ANT), anthraquinone (ANQ), and EPFRs induced by ANT transformation on clay surfaces. Our results showed that EPFRs-exposed earthworms experienced histopathological damage, which was more severe than ANT and ANQ-exposed earthworms. The source of EPFRs damage was associated with the obvious dysbiosis of reactive oxygen species in earthworms. Specifically, EPFRs trigged more severe antioxidant responses and oxidative damages (e.g., membrane lipid and DNA injury) in comparison with ANT and ANQ exposure, as evidenced by the values of integrated biomarker response (IBR) following the order of EPFRs (14.5)ANT (12.8)ANQ (10.9). Moreover, high-throughput sequencing found that EPFRs induced dramatic changes in the composition and structure of earthworm gut microbiota, which may involve immune and metabolism dysfunction, in turn aggravated EPFRs toxicity. Overall, the obtained information highlights the more severe injury of EPFRs to terrestrial organisms, deserving more attentions for the assessment of potential risks associated with radical intermediates in PAHs-contaminated soils.

Microplastic (MP) exposure in the environment has been commonly demonstrated to have adverse effects on human health. The majority of studies on MP were related to the aquatic and terrestrial systems, its potential risk for ecosystem and human health when exposed to the atmosphere is not well-understood. The presented study, taking Xi'an, a megacity in Northwest China, as an example, first estimated the possibility of local residents bearing MPs pollution. The results figured out an average abundance of MPs in TSP, PM

It is well known that microplastics (MPs) may experience weathering and aging under ultraviolet light (UV) irradiation, but it remains unclear if these processes are impacted by natural components, such as clay minerals. In this study, we systematically investigated the photodegradation behaviors of polyvinyl chloride (PVC) and poly (ethylene terephthalate) (PET), two utmost used plastics, in the presence of clay minerals (kaolinite and montmorillonite). The results demonstrated that the clay minerals, particularly kaolinite, significantly promoted the MPs photodegradation, and the aging of PET was more prominent. The photodegradation was the most distinct at pH 7.0, regardless of the presence or absence of the clay minerals. The results of electron paramagnetic resonance and inhibition experiments of reactive oxygen species indicated that the minerals, particularly kaolinite, remarkably facilitated production of •OH, which was the key species contributing to the photodegradation of MPs. Specifically, UV irradiation facilitated the photo-ionization of MPs, producing hydrated electrons and MP radical cations (MP+). The Lewis base sites prevalent on the clay siloxane surfaces could stabilize the MP radical cations and prevent their recombination with hydrated electrons, which promoted the generation of •OH under aerobic conditions, and facilitated the degradation of MP. Two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (COS) analysis and ultra-high-performance liquid chromatography coupled to a Q Exactive Orbitrap HF mass spectrometer were used to identify the sequential changes of functional groups, and the degradation products of the MPs. This study improves our understanding on the aging of MPs in the complex natural environment.

Biochar has been widely used in advanced oxidation processes (AOPs) for the decomposition of organic contaminants. However, the role of intrinsic metals in hyperaccumulator biomass in the physico-chemical properties and performance of peroxodisulfate (PDS) activation by biochar is still unclear. This work employed hyperaccumulator biomass containing Fe, Mn and Zn, respectively. Result showed that as the pyrolysis temperature of the biochar increased, Fe was gradually reduced to iron oxide and Fe0, and Zn was reduced and volatilized; however, Mn remained in biochar in the form of MnS and CaMnO3 with high valence states. These thermochemical behaviors of intrinsic metals also facilitated graphitized structure growth and pore development (for Zn) and persistent free radicals (PFRs) generation (for Mn and Zn) in biochar, and these processes were crucial for imidacloprid degradation in biochar/PDS systems. Moreover, Fe/Zn@PB9/PDS showed better imidacloprid degradation performance, while Mn species in Mn@PB were catalytically inert. In addition, the radical pathway depending on·SO4- and·OH was the dominant pathway for imidacloprid degradation in the Fe@PB9/PDS systems, while the·O2--mediated 1O2 pathway and 1O2-based nonradical pathway contributed more in the Zn@PB9/PDS systems. These results reveal the role of intrinsic metals in biochar-based catalysts and provide a reference for the preparation of green and efficient hyperaccumulator-derived biochar catalysts for AOPs.

There is increasing concern about the severe endocrine-related health problems because of the discharge of estrogenic disrupting chemicals (EDCs) into the natural environment. In this study, we investigated the activation of monochloramine (NH

Classical chemical precipitation technology is inefficient for the removal of heavy metal-organic complexes from wastewater. In this study, a novel and green strategy of coupling bicarbonate-activated hydrogen peroxide (BHP) oxidation and alkaline precipitation was proposed for simultaneous decomplexation of Cu-ethylenediaminetetraacetic acid (Cu-EDTA) and Cu precipitation. The Cu-EDTA decomplexation efficiency reached 92.0% within 60 min of the BHP treatment, and the decomplexation process was spontaneous and endothermic. Reactive substances such as O2−, OH, and 1O2 were identified, and O2− was predominant in the Cu-EDTA decomplexation. The weak alkaline environment provided by bicarbonate favored the generation of the reactive substances and subsequent Cu-EDTA decomplexation. Relatively higher H2O2 dosage favored Cu-EDTA decomplexation, while excessive bicarbonate dosage inhibited the reaction. TOC removal efficiency and Cu removal efficiency reached 78.4% and 68.3% after 60 min treatment, respectively. The Cu O and Cu N bonds in Cu-EDTA were destroyed by the reactive substances, and a series of Cu-containing intermediates, small organic molecules such as ethanamine, ethylene glycol and butanediol, and NO3− were produced. The released Cu ions were precipitated as Cu2(OH)2CO3, CuCO3, Cu(OH)2, and CuO. Possible pathways of Cu-EDTA decomplexation in this system were proposed.

The functional stability of soil enzymes is fundamental to the sustainability of soil biochemical processes and is affected by many environmental stressors. This study focused on the influences of long-term arsenic (As) contamination on soil enzyme functional stability: the resistance (ratio of the disturbed to control) and resilience (integrated recovery rate) of soil enzyme activities (β-glucosidase, urease, acid phosphatase, fluorescein diacetate (FDA) hydrolase) over 30 days incubation after an experimental heat disturbance (50 oC for 18 h). Results showed that the resistance of soil enzymes to heat disturbance differed among the enzyme types and followed the order: urease > β-glucosidase > acid phosphatase > FDA hydrolase. Urease activity was generally not affected and showed high stability against heat disturbance. The β-glucosidase activity recovered to the control level by 30 days, while 80% and 90% recovery on average occurred for acid phosphatase and FDA hydrolase, respectively. Long-term As contamination altered soil enzyme functional resistance and resilience to heat disturbance and resulted in three kinds of responses: (i) no apparent alteration (urease); (ii) moderate As contamination increased enzyme heat resistance (β-glucosidase); (iii) the resistance and resilience decreased with increasing As concentration (acid phosphatase and FDA hydrolase). The results demonstrated that different enzyme-catalytic biochemical processes have different functional stabilities under combined As and heat disturbance, and the negative changes in the soil enzyme activity led to losses in soil functions. Our study provides further evidence on the impacts of heavy metal/metalloid on soil enzyme functional stability in response to additional disturbance.

EDTA-chelated metals, which widely occur during heavy metal contaminated-soil remediation by EDTA washing, are difficult to remove by traditional chemical precipitation because of the strong complexation between EDTA and heavy metal ions. A strategy, i.e., non-thermal plasma (NTP) oxidation/alkaline precipitation, was developed to remove the EDTA-chelated metals; EDTA-chelated copper (EDTA-Cu) was used as the model pollutant and the influences of some concomitant ions on EDTA-Cu decomplexation and Cu release were evaluated. The concomitant anions Cl− and NO3− favored EDTA-Cu decomplexation, whereas CO32− disfavored this process; the concomitant positive ions Ni2+ and Fe3+ both promoted EDTA-Cu decomplexation via replacement or Fenton-like effects. These effects were also characterized by total organic carbon and Cu2+ release analysis. The contributions of O3, O, 1O2, OH, and O2− to EDTA-Cu decomplexation were quantitatively analyzed. Ethanamine, acetamide, glycolic acid, acetic acid, formamide, ethylene glycol, and butanedioic acid were monitored using gas chromatography-mass spectrometry, and a possible decomposition pathway of EDTA-Cu was proposed. Furthermore, the chemical compositions of the precipitates were diagnosed by energy dispersive X-ray spectroscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, scanning electron microscopy, and thermal gravimetric analysis.

The application of Ag3PO4 as a commonly used photocatalyst is limited by its high recombination potency and electron–hole pairs with weak redox potential. It is significant to enhance the photocata...

Transformation of PAHs, i.e., anthracene, and production of environmentally persistent free radicals (EPFRs) on seven types of representative soils were investigated, focusing on the influences of soil characteristics and ambient conditions on these reactions. The transformation rate of anthracene exhibits the order of red earth > yellow earth > latosol ∼ fluvo-aquic soil > brown earth > chernozem > calcic brown soil, which is positively correlated with Fe content in soils. Afterwards, batch reactions on pure representatives of soil minerals, including Fe2O3, Fe3O4, FeOOH, and MnO2, demonstrate that anthracene is prone to mineral-promoted transformation. The presence of higher amount of organic carbon lower the transformation rate of anthracene, whereas the formed EPFRs can be stabilized for a longer time. Subsequent experiments associated with the influences of environmental conditions on mineral-promoted reactions suggest that both anthracene transformation and EPFRs generation readily occur under dry condition. Light irradiation not only promotes the formation of EPFRs, but also greatly accelerates the decay of EPFRs and the 1/e lifetime decreases from 5 to 20 d in dark to approximately 1 d. Meanwhile, the anoxic condition is favorable for the persistence of EPFRs. The obtained results suggested the potential environmental risks association with EPFRs in PAHs-contaminated soils.

There are a large number of microplastic (MPs) in the sea or on land, most of which undergo physical, chemical or biological processes leading to the release of dissolved organic matter (DOM). In this study, we analyzed the change of Polyurethane microplastic (PU-MPs) valence bond under different aging conditions thanks to Fourier transform infrared spectroscopy (FTIR) and its surface characteristics using scanning electron microscopy (SEM) and also described the characteristics of DOM dissolved from PU (PU-DOM) under UV aging process in two different medium (water and air), based on Dissolved organic carbon (DOC) measurements, UV-visible spectrometer and Three-dimensional excitation emission matrices (3D-EEMs). The DOC data both showed that Under UV aging of different systems, PU-DOM concentration increases with the extension of aging time, and correspondingly, its toxicity to human colon adenocarcinoma cells also increases, but the release amount of PU-DOM under air aging is higher than that of PU-DOM in water. We speculate that it may be the refraction and scattering of water, which leads to the reduction of the intensity of UV radiation. 3D-EEMs identified tryptophan-like fluorescent component and tyrosine-like component, meanwhile, the liquid chromatography-mass spectrometer (LC-MS) data further confirmed the formation of acid substances. The results further confirmed that the composition of PU-DOM in different systems is the same, but the release amount is different. The contents of the produced conjugated carbonyls and Reactive oxygen species (ROS) because of light irradiation increased likewise. The cytotoxicity of PU-DOM was consistent with the changing trend of ROS level in PU-MPs, suggesting that the produced ROS induced the in vitro toxicities. The results not only highlight the adverse health effects of photoaged PU-MPs, but also provide new perspectives for the environmental risks of MPs.

Algal organic matter (AOM) is a potential precursor of disinfection byproducts (DBPs) in water treatment. It is a major challenge to identify macromolecular DBPs due to the diversity of AOM. In this study, Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR/MS) was applied to diagnose the AOM diversity after algae removal by plasma oxidation and to recognize the macromolecular DBPs in subsequent chlorination. Significant removal of AOM released by M. aeruginosa, C. raciborskii, and A. spiroies was achieved by plasma oxidation, accompanied by decrease in the proportion of CHNO formulas and increase in CHO formulas. Without plasma treatment, chlorination generated approximately 2486 macromolecular carbonaceous DBPs (C-DBPs) and 1984 nitrogenous DBPs (N-DBPs), with C

International audience; The uses of biochar as soil fertilizer can offset global warming and reduce dependence on limited mineral resources in the future circular economy, yet biochar may contain contaminants that can ultimately enter the food chain. In particular, persistent free radicals are emerging contaminants previously detected in biochar but underlying mechanisms of radical formation are not yet established. Here we studied radical generation during hydrothermal carbonization of waste sludge at 160-220 ºC for 0.5-2 h with solid weight ratios of 10%w-40%w using electron paramagnetic resonance and Fourier transform infrared spectrometry. Results reveal that radical concentration increases with temperature, reaction time, and weight ratio in sludge biochars, reaching a content of 47.2 × 10 15 spins/g for 220 ºC, 2 h heating, and 40%w solid ratio. Moreover, low temperature of about 160 ºC favors the production of oxygen-centered radicals, whereas higher temperature of 220 ºC produces carbon-centered radicals. Our findings imply that biochar ecotoxicity should be assessed prior applications to prevent adverse health effects.

Reactive oxygen species, especially hydroxyl radicals (OH), exert a distinguished role in the transformation of contaminants, and their in-situ generation attracts wide attentions in environmental and geochemical areas. The present work explored the potential formation of OH during the interactions between iron-containing clay minerals and environmentally prevalent organic acids in dark environments. The results demonstrated that the accumulative OH concentrations were related to the solution pH, the types of clay minerals, and the nature of organic acid species. At pH 5.5, 1.2- 15.2 times of OH were generated from the reduction of Na-nontronite-2 (Na-NAu-2) compared with other clay minerals in the presence of ascorbic acid (AA) at 144 h. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) analyses indicated that Fe(III) was reduced to Fe(II) by AA during OH formation. Meanwhile, chemical probe tests coupled with quenching experiments confirmed the generation of H2O2 and superoxide radical (O2-), which participated in the formation of OH. The produced OH/O2- can transform 68.4%, 86.4%, and 50.1% of phenol, p-nitrophenol, and 2,4-dichlorophenol within 168 h in AA-Na-NAu-2 suspension, respectively. This work provides valuable insights into OH production in the mutual interaction between organic acids and iron-bearing clays, which is helpful for the development of a new method for removing organic pollutants from contaminated water and soil environments.

Dissolved organic matter (DOM) in rivers is a critical regulator of the cycling and toxicity of pollutants and the behavior of DOM is a key indicator for the health of the environment. We investigated the sources and characteristics of DOM in surface water and sediment samples of the Wei River, China. Dissolved organic carbon (DOC) concentration and ultraviolet absorbance at 254 nm (UV254) increased in the surface water and were decreased in the sediment downstream, indicating that the source of DOM in the water differed from the sediment. Parallel factor (PARAFAC) analysis of the excitation-emission matrices (EEM) revealed the presence of terrestrial humus-like, microbial humus-like and tryptophan-like proteins in the surface water, whereas the sediment contained UVA humic-like, UVC humic-like and fulvic-like in the sediment. The DOM in the surface water and sediment were mainly derived from microbial metabolic activity and the surrounding soil. Surface water DOM displayed greater photodegradation potential than sediment DOM. PARAFAC analysis indicated that the terrestrial humic-like substance in the water and the fulvic-like component in the sediment decomposed more rapidly. These data describe the characteristics of DOM in the Wei River and are crucial to understanding the fluctuations in environmental patterns.