Generation Of Reactive Oxidative Species Research Articles

Metabolic Profiling of Cochlear Organoids Identifies α-Ketoglutarate and NAD+ as Limiting Factors for Hair Cell Reprogramming.

Cochlear hair cells are the sensory cells responsible for transduction of acoustic signals. In mammals, damaged hair cells do not regenerate, resulting in permanent hearing loss. Reprogramming of the surrounding supporting cells to functional hair cells represent a novel strategy to hearing restoration. However, cellular processes governing the efficient and functional hair cell reprogramming are not completely understood. Employing the mouse cochlear organoid system, detailed metabolomic characterizations of the expanding and differentiating organoids are performed. It is found that hair cell differentiation is associated with increased mitochondrial electron transport chain (ETC) activity and reactive oxidative species generation. Transcriptome and metabolome analyses indicate reduced expression of oxidoreductases and tricyclic acid (TCA) cycle metabolites. The metabolic decoupling between ETC and TCA cycle limits the availability of the key metabolic cofactors, α-ketoglutarate (α-KG) and nicotinamide adenine dinucleotide (NAD+). Reduced expression of NAD+ in cochlear supporting cells by PGC1α deficiency further impairs hair cell reprogramming, while supplementation of α-KG and NAD+ promotes hair cell reprogramming both in vitro and in vivo. These findings reveal metabolic rewiring as a central cellular process during hair cell differentiation, and highlight the insufficiency of key metabolites as a metabolic barrier for efficient hair cell reprogramming.

UVB-Aged Microplastics and Cellular Damage: An in Vitro Study.

Plastics are synthetic organic compounds whose widespread use generates enormous waste. Different processes, such as mechanical abrasion, microbiological activity, and UVB irradiation, can fragment the plastic material and generate microplastics (MPs). MPs are ubiquitous, and various organisms, including humans, can ingest or inhale them, with potential adverse health effects. The differences between UV-aged and virgin particles were studied to evaluate the genotoxic damage and oxidative stress induced by polystyrene MPs with 1 and 5µm sizes on the monocyte-like cell line (THP-1). Fourier transform infrared spectroscopy and Ζ-potential measurements were used to characterise MP particles after UVB exposure. Cells exposed to MPs show a widespread change in the cellular environment with the generation of reactive oxidative species (ROS), as indicated by the increased malondialdehyde level. The occurrence of genotoxic damage is correlated to the smaller size and ageing state of the MPs. The biochemical and genomic alterations observed in this in vitro study suggest that MPs, ubiquitous pollutants, following natural degradation and oxidation processes can cause various adverse effects on the health of the exposed population, making it necessary to carry out further studies to better define the real risk.

Effects of dissolved organic matter from sludge pyrolysis biochar on the triclosan removal from contaminated soil

When sludge biochar (SC) prepared from sewage sludge was used to remove triclosan (TCS) from both aqueous solution and soil, the adsorption capacity increased with increasing pyrolysis temperature, while the degradation rate showed a different pattern, namely, SC-500 > SC-800 > SC-600 > SC-700. TCS degradation rate achieved nearly 100 % at 2 h with SC-500 used as a Fenton catalyst. Aromaticity of dissolved organic matter (DOM) was positively correlated with the degradation of TCS and adding homologous DOM solution shortened the equilibrium time of TCS degradation, while removing DOM from SC prolonged, compared to the original SC. The results of X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance spectrometer (EPR) characterization indicated that SC-500 performed a stronger catalytic degradation ability due to the relatively high Fe2+ content to produce more ∙OH and SC-derived DOM act as an electron shuttle to promote other reactive oxidative species generation through two free radical pathways in the activation of H2O2 by Fe2+, which in turn promoted the degradation of TCS.

Potential use of antioxidants for the treatment of chronic inflammatory diseases.

The excessive production of various reactive oxidant species over endogenous antioxidant defense mechanisms leads to the development of a state of oxidative stress, with serious biological consequences. The consequences of oxidative stress depend on the balance between the generation of reactive oxidant species and the antioxidant defense and include oxidative damage of biomolecules, disruption of signal transduction, mutation, and cell apoptosis. Accumulating evidence suggests that oxidative stress is involved in the physiopathology of various debilitating illnesses associated with chronic inflammation, including cardiovascular diseases, diabetes, cancer, or neurodegenerative processes, that need continuous pharmacological treatment. Oxidative stress and chronic inflammation are tightly linked pathophysiological processes, one of which can be simply promoted by another. Although, many antioxidant trials have been unsuccessful (some of the trials showed either no effect or even harmful effects) in human patients as a preventive or curative measure, targeting oxidative stress remains an interesting therapeutic approach for the development of new agents to design novel anti-inflammatory drugs with a reliable safety profile. In this regard, several natural antioxidant compounds were explored as potential therapeutic options for the treatment of chronic inflammatory diseases. Several metalloenzymes, such as superoxide dismutase, catalase, and glutathione peroxidase, are among the essential enzymes that maintain the low nanomolar physiological concentrations of superoxide (O2•-) and hydrogen peroxide (H2O2), the major redox signaling molecules, and thus play important roles in the alteration of the redox homeostasis. These enzymes have become a striking source of motivation to design catalytic drugs to enhance the action of these enzymes under pathological conditions related to chronic inflammation. This review is focused on several major representatives of natural and synthetic antioxidants as potential drug candidates for the treatment of chronic inflammatory diseases.

Novel enhanced defluorination of perfluorooctanoic acids by biochar-assisted ultrasound coupling ferrate: Performance and mechanism

An ultrasound (US)/biochar (BC)/ferrate (Fe (VI)) system was firstly proposed to enhance perfluorooctanoic acid (PFOA) defluorination. It achieved 93 % defluorination optimally, higher than the sum of 77 % (28 % and 49 % for US/BC and US/Fe (VI) respectively), implying synergistic effect. Besides, the mechanism study confirmed that, this system can not only increase the specific surface area of BC and the generation of reactive oxidant species (ROS), enriching the active sites and forming new oxygen-containing functional groups, but also promote the formation of intermediate iron species. The PFOA degradation in the US/BC/Fe (VI) was probably an adsorption-degradation process, both ROS and electron transfer promoted the defluorination. Additionally, its sustainability was also demonstrated with 14 % reduced defluorination percentage after five cycles of BC. Overall, the synergistic effect of the US/BC/Fe (VI) and its enhancing mechanism for PFOA defluorination were clarified firstly, which contributes to the development of biochar for assisting polyfluoroalkyl substances degradation.

Shear Stress‐Triggered Theranostic Nanoparticles for Piezoelectric‐Fenton‐Photodynamic Thrombolysis and Endogenous Thrombus Imaging

AbstractThrombus therapy is challenged by potential bleeding risk of thrombolytic agents, and external irradiation is usually needed in thrombus imaging. Herein, highly efficient theranostic platforms are designed for piezoelectric‐Fenton‐photodynamic thrombolysis and endogenous thrombus imaging in response to the elevated shear stress at the thrombus site. Piezoelectric tetragonal barium titanate (tBT) nanoparticles (NPs) are coated with Fe3+‐coordinated metal‐organic frameworks (MOFs), followed by inoculation of chlorin e6‐luminol conjugates and heparin absorption to obtain theranostic tBT@MOFCL/Hep NPs. Shear stress‐induced piezopotential on NPs accelerates Fe3+/Fe2+ transformation to deplete MOF layers, activates Fenton reaction and produces reactive oxidative species (ROS) for non‐pharmacological thrombolysis. In the meantime, the site‐specific ROS generation oxidizes luminol and the chemiluminescent resonance energy transfer with chlorin e6 generates red fluorescence for thrombus imaging without using external light irradiation. After intravenous injection into a carotid artery thrombosis model, the heparin‐mediated thrombus targeting yields 6.5‐fold higher luminescent intensity at the thrombus site. Thrombi in the carotid arteries are almost completely dissolved with integration of piezoelectric dynamic therapy, piezopotential‐enhanced Fenton reaction, and chemiluminescence‐excited photodynamic therapy, while causing no haematologic and histopathologic abnormality. This study demonstrates a concise strategy to generate shear stress‐responsive built‐in piezoelectric potentials, site‐specific non‐pharmacological thrombolysis, self‐illuminating, and stenosis degree‐adaptable thrombus imaging.

N-doped microcrystalline graphite for boosting peroxymonosulfate activation with highly efficient degradation of bisphenol A

With the excellent electrical conductivity and unique structure, carbonaceous materials are expected to prepare green catalysts used in sulfate radical based advanced oxidation processes. Nevertheless, most of researches are focusing on artificial synthetic material to date, thus the studies on natural carbon materials call for attention and development. Herein, impregnation-pyrolysis method was employed by adopting the urea as an extrinsic N-dopant under 850 °C to favor C–N configuration for natural microcrystalline graphite (MG). And N element presented as pyridinic N (27.42 %), pyrrolic N (40.08 %), graphitic N (25.86 %) and nitric oxide (6.65 %) in N-doped microcrystalline graphite (NMG). In addition, the catalysis performance of MG, NMG and calcined microcrystalline graphite (CMG) was examined by the degradation of bisphenol A (BPA). The NMG system exhibited high activity in a broad pH range, and acidic conditions promote the reaction rate greatly. Based on quenching tests and electron paramagnetic resonance, the degradation mechanisms comprised radical and nonradical pathway, in which 1O2 was the dominant reactive oxidative species (ROS). This study suggested that pyridinic N, pyrrolic N, graphitic N, sp (2)-hybridized carbon structure as well as defects in NMG promoted the generation of ROS, and provides a new insight in natural carbon materials for the fabrication of new eco-friendly and highly efficient PMS activation catalysts.

Lysosomal dysfunction in carbon black-induced lung disorders

Carbon black (CB), a component of environmental particulate pollution derived from carbon sources, poses a significant threat to human health, particularly in the context of lung-related disease. This study aimed to investigate the detrimental effects of aggregated CB in the average micron scale on lung tissues and cells in vitro and in vivo. We observed that CB particles induced lung disorders characterized by enhanced expression of inflammation, necrosis, and fibrosis-related factors in vivo. In alveolar epithelial cells, CB exposure resulted in decreased cell viability, induction of cell death, and generation of reactive oxidative species, along with altered expression of proteins associated with lung disorders. Our findings suggested that the damaging effects of CB on the lung involved the targeting of lysosomes. Specifically, CB promoted lysosomal membrane permeabilization, while lysosomal alkalization mitigated the harmfulness of CB on lung cells. Additionally, we explored the protective effects of alkaloids derived from Nelumbinis plumula, with a focus on neferine, against CB-induced lung disorders. In conclusion, these findings contribute to a deeper understanding of the pathophysiological effects of CB particles on the lungs and propose a potential therapeutic approach for pollution-related diseases.

Heme Oxygenase-1 Inhibition Modulates Autophagy and Augments Arsenic Trioxide Cytotoxicity in Pancreatic Cancer Cells.

Pancreatic ductal adenocarcinoma (PDAC) is the most prevalent form, accounting for more than 90% of all pancreatic malignancies. In a previous study, we found that hypoxia and chemotherapy induced expression of Heme Oxygenase-1 (HO-1) in PDAC cells and tissues. Arsenic trioxide (ATO) is the first-line chemotherapeutic drug for acute promyelocytic leukemia (APL). ATO increases the generation of reactive oxidative species (ROS) and induces apoptosis in treated cells. The clinical use of ATO for solid tumors is limited due to severe systemic toxicity. In order to reduce cytotoxic side effects and resistance and improve efficacy, it has become increasingly common to use combination therapies to treat cancers. In this study, we used ATO-sensitive and less sensitive PDAC cell lines to test the effect of combining HO-1 inhibitors (SnPP and ZnPP) with ATO on HO-1 expression, cell survival, and other parameters. Our results show that ATO significantly induced the expression of HO-1 in different PDAC cells through the p38 MAPK signaling pathway. ROS production was confirmed using the oxygen-sensitive probes DCFH and DHE, N-acetyl cysteine (NAC), an ROS scavenger, and oxidized glutathione levels (GSSG). Both ATO and HO-1 inhibitors reduced PDAC cell survival. In combined treatment, inhibiting HO-1 significantly increased ATO cytotoxicity, disrupted the GSH cycle, and induced apoptosis as measured using flow cytometry. ATO and HO-1 inhibition modulated autophagy as shown by increased expression of autophagy markers ATG5, p62, and LC3B in PDAC cells. This increase was attenuated by NAC treatment, indicating that autophagy modulation was through an ROS-dependent mechanism. In conclusion, our work explored new strategies that could lead to the development of less toxic and more effective therapies against PDAC by combining increased cellular stress and targeting autophagy.

Peroxiredoxins in erythrocytes: far beyond the antioxidant role.

The red blood cells (RBCs) are essential to transport oxygen (O2) and nutrients throughout the human body. Changes in the structure or functioning of the erythrocytes can lead to several deficiencies, such as hemolytic anemias, in which an increase in reactive oxidative species generation is involved in the pathophysiological process, playing a significant role in the severity of several clinical manifestations. There are important lines of defense against the damage caused by oxidizing molecules. Among the antioxidant molecules, the enzyme peroxiredoxin (Prx) has the higher decomposition power of hydrogen peroxide, especially in RBCs, standing out because of its abundance. This review aimed to present the recent findings that broke some paradigms regarding the three isoforms of Prxs found in RBC (Prx1, Prx2, and Prx6), showing that in addition to their antioxidant activity, these enzymes may have supplementary roles in transducing peroxide signals, as molecular chaperones, protecting from membrane damage, and maintenance of iron homeostasis, thus contributing to the overall survival of human RBCs, roles that seen to be disrupted in hemolytic anemia conditions.

Endogenous Fe2+-activated nanomedicine to amplify ROS generation and in-situ response NIR-II photothermal therapy of tumor

Endogenous activated nanomedicines have great potential in improving therapeutic efficacy and minimizing side effects in cancer therapy. Herein, a novel nanomedicine (CuHCF) was developed based on a mixed-metal (Cu2+/Fe3+) Prussian blue analogue via a facile co-precipitation method, which could respond to the endogenous labile iron pool (LIP) achieving enhanced chemodynamic therapy (CDT) and in situ NIR-II photothermal therapy (PTT) of tumor. Notably, the prepared CuHCF itself shows low Fenton catalytic activity, which however, is found to significantly amplify the generation of reactive oxidative species (ROS) when exposed to the over-expressed Fe2+ in tumor region, since the intracellular Fe2+ triggers the redox cycles between Fe3+/Fe2+ and Cu2+/Cu+ of CuHCF. More interestingly, it is found that the CuHCF presents an obviously enhanced near-infrared absorption after reacting with Fe2+, enabling in situ hyperthermia under NIR-II (1064 nm) irradiation. Both in vitro and in vivo results demonstrated that a highly efficient synergistic therapy of CDT/PTT was achieved via a ferroptosis pathway when CuHCF was combined with the ferroptosis inducer erastin (ERA). Such an endogenous activated nanomedicine provides a promising paradigm to enhance specific CDT in synergy with in situ NIR-II PTT for precise cancer therapy.

Endothelial glycocalyx injury is involved in heatstroke-associated coagulopathy and protected by N-acetylcysteine.

Damage to endothelial glycocalyx (EGCX) can lead to coagulation disorders in sepsis. Heat stroke (HS) resembles sepsis in many aspects; however, it is unclear whether EGCX injury is involved in its pathophysiology. The purpose of this study was to examine the relationship between the damage of EGCX and the development of coagulation disorders during HS. We retrospectively collected 159 HS patients and analyzed coagulation characteristics and prognosis of HS patients with or without disseminated intravascular coagulation (DIC). We also replicated a rat HS model and measured coagulation indexes, pulmonary capillary EGCX injury in HS rats. Finally, we evaluated the effect of the antioxidant N-acetylcysteine (NAC) on HS-initiated EGCX injury and coagulation disorders. Clinical data showed that HS patients complicated with DIC had a higher risk of death than HS patients without DIC. In a rat HS model, we found that rats subjected to heat stress developed hypercoagulability and platelet activation at the core body temperature of 43°C, just before the onset of HS. At 24h of HS, the rats showed a consumptive hypo-coagulation state. The pulmonary capillary EGCX started to shed at 0h of HS and became more severe at 24h of HS. Importantly, pretreatment with NAC substantially alleviated EGCX damage and reversed the hypo-coagulation state in HS rats. Mechanically, HS initiated reactive oxidative species (ROS) generation, while ROS could directly cause EGCX damage. Critically, NAC protected against EGCX injury by attenuating ROS production in heat-stressed or hydrogen peroxide (H2O2)-stimulated endothelial cells. Our results indicate that the poor prognosis of HS patients correlates with severe coagulation disorders, coagulation abnormalities in HS rats are associated with the damage of EGCX, and NAC improves HS-induced coagulopathy, probably through its protection against EGCX injury by preventing ROS generation.

Mitochondrial Dysfunction in Cardiac Arrhythmias.

Electrophysiological and structural disruptions in cardiac arrhythmias are closely related to mitochondrial dysfunction. Mitochondria are an organelle generating ATP, thereby satisfying the energy demand of the incessant electrical activity in the heart. In arrhythmias, the homeostatic supply-demand relationship is impaired, which is often accompanied by progressive mitochondrial dysfunction leading to reduced ATP production and elevated reactive oxidative species generation. Furthermore, ion homeostasis, membrane excitability, and cardiac structure can be disrupted through pathological changes in gap junctions and inflammatory signaling, which results in impaired cardiac electrical homeostasis. Herein, we review the electrical and molecular mechanisms of cardiac arrhythmias, with a particular focus on mitochondrial dysfunction in ionic regulation and gap junction action. We provide an update on inherited and acquired mitochondrial dysfunction to explore the pathophysiology of different types of arrhythmias. In addition, we highlight the role of mitochondria in bradyarrhythmia, including sinus node dysfunction and atrioventricular node dysfunction. Finally, we discuss how confounding factors, such as aging, gut microbiome, cardiac reperfusion injury, and electrical stimulation, modulate mitochondrial function and cause tachyarrhythmia.

Tetracycline degradation by nonthermal plasma: removal efficiency, degradation pathway, and toxicity evaluation.

Tetracyclines (TCs) are often discussed as one of the emerging contaminants detected in water matrices and studied for their persistence towards conventional water treatment technologies. In this work, the treatment of TC in aqueous solutions with nonthermal plasma gliding arc process was investigated. The degradation efficiency of TC was studied along with the effect of initial concentration, working gas, pH, and the presence of a radical scavenger. The generation of reactive oxidative species was characterized by the quantification of radical hydroxyl, hydrogen peroxide, ozone, nitrite, and nitrate. Mineralization efficiency was examined by assessment of Total organic carbon evolution. Experimental results have shown that the gliding arc plasma is effective for the treatment of TC. At an initial concentration of 5 mg/L: degradation rates of 94.95% and 60.45% were achieved, while mineralization rates were 81.3% and 57.34% under O2 and air plasma, respectively. O2 plasma exhibited an immense potential for the generation of reactive oxygen species. Meanwhile, air plasma showed better degradation performance in the presence of a radical scavenger. Moreover, degradation products were identified by mass spectroscopy analysis and degradation pathway was proposed. The gliding arc process proposed in this work is promising for the removal of TC antibiotics.

Evaluating anticancer properties of Withaferin A-a potent phytochemical.

Withaferin A is a C28 steroidal lactone derived from the plant Withania somnifera, commonly known as Ashwagandha. Withaferin A has received great attention for its anticancer properties noted in cancer cells of various origins. Extracts of Withania somnifera have been used in traditional Ayurvedic and Unani Indian medicine for their various pharmacological benefits. In recent years, Withania somnifera or Ashwagandha extract has become popularized as a health supplement marketed for its stress and anxiety reducing effects. Withaferin A is one of the most studied withanolides extracted from Withania somnifera that has gained great attention for its anticancer, anti-inflammatory, metabolic, and pro-apoptotic effects. Extensive in vivo and in vitro studies have depicted Withaferin A's interactions with key role players in cancerous activity of the cell to exert its pro-apoptotic effects. Withaferin A interactions with NF-κB, STAT, Hsp90, ER-α, p53, and TGF-β have noted inhibition in cancer cell proliferation and cell cycle arrest in G2/M stage, ultimately leading to apoptosis or cell death. This review highlights pro-apoptotic properties of Withaferin A including generation of reactive oxidative species, Par-4 activation, endoplasmic reticulum stress (ER) induction, and p53 activation. Analysis of Withaferin A's involvement in various oncogenic pathways leading to malignant neoplasm and its pharmacologic activity in conjunction with various cancer drugs provides promising evidence in therapeutic potential of Withaferin A as a cancer treatment.

Cover Feature: Piezodeposition of Metal Cocatalysts for Promoted Piezocatalytic Generation of Reactive Oxygen Species and Hydrogen in Water (ChemCatChem 16/2022)

The Cover Feature highlights the key role of noble metal as cocatalysts for piezoelectricity-driven oxygen reduction and hydrogen evolution reactions. In their Research Article, W. Wang, J. Li and co-workers synthesized BaTiO3@Metal (BTO@M, M=Pt, Pd and Au) hetero-nanostructures by using a piezodeposition method. The deposited metal cocatalysts significantly promote the separation and migration of piezogenerated charge, consequently enhancing the piezocatalytic reactions on different metal cocatalyst interfaces. Specifically, BTO@Au under ultrasonic vibrations exhibited most efficient generation of reactive oxidative species via a two-electron reduction pathway in the presence of dissolved oxygen, while BTO@Pt showed promoted hydrogen evolution in the absence of oxygen. This work could further advance piezocatalysis in the field of clean energy, water disinfection and biomedicine. More information can be found in the Research Article by W. Wang, J. Li and co-workers.

Piezodeposition of Metal Cocatalysts for Promoted Piezocatalytic Generation of Reactive Oxygen Species and Hydrogen in Water

AbstractPiezocatalysis in aqueous medium has shown great potential for various applications, however the efficiency of piezocatalytic nanoparticles is harmed by the limited utilization of piezoelectric charge and the lack of active catalytic interface. In this study, BaTiO3@Metal (BTO@M, M=Pt, Pd and Au) hetero‐nanostructures were synthesized by using a piezodeposition method. The deposited metal cocatalysts significantly promote the separation and migration of piezogenerated charge, consequently enhancing the piezocatalytic reactions on different metal cocatalyst interfaces. Specifically, BTO@Au under ultrasonic vibrations exhibited most efficient generation of reactive oxidative species via a two‐electron reduction pathway in the presence of dissolved oxygen, while BTO@Pt showed promoted hydrogen evolution in the absence of oxygen. The metal‐piezoelectric hetero‐nanostructures proposed in this work highlight the key role of noble metal as cocatalysts for piezoelectricity‐driven oxygen reduction and hydrogen evolution reactions, which could further advance piezocatalysis in the field of clean energy, water disinfection and biomedicine.

Revisiting the contribution of FeIVO2+ in Fe(II)/peroxydisulfate system

Recent studies have proposed that the high-valent iron species (such as FeIVO2+) rather than sulfate radical (SO4•−) and hydroxyl radical (•OH) are the main reactive oxidant species (ROS) in Fe(II)/peroxydisulfate (PDS) system with the methyl phenyl sulfoxide (PMSO) as the FeIVO2+ probe. However, many operational factors may interfere with the accuracy of this method, so the contribution of FeIVO2+ calculated by this method is controversial. In this study, the possible effect of Fe(II) concentration, pollutant type, reducing agent, or coexisted anions on FeIVO2+ production and its corresponding contribution to the removal of target pollutants in the Fe(II)/PDS system were investigated in detail, and the intrinsic mechanisms involved were also explored. This study shows that ROS generation is a complex process in the Fe(II)/PDS system, and multiple combinatorial approaches are urgently required to deeply explore the contribution of ROS to the elimination of target contaminants.

Self-disinfecting carbon filter: In situ spontaneous generation of reactive oxidative species via oxygen reduction reaction for efficient water treatment

Portable water filters are crucial to water purification for household or community-scale usage, and are particularly prominent in developing countries or remote areas without water treatment plants. However, a growing concern is that activated carbon can be a good support medium for microbial growth, eventually forming active biofilms. Herein, we report the preparation and functional validation of a new self-disinfecting carbon filter. The addition of an Ag/AgCl-Ru/RuO2 mesh developed in this study does not require modification of current activated carbon products by any additional industrial process and maintains the adsorption capability of activated carbon for environmental pollutants. The in situ generation of reactive oxygen species (ROS), including H2O2, O2•– or their combination which are responsible for the disinfection effect, offers an alternative functional module for activated carbon systems. Our system provides an alternative solution for overcoming a crucial limitation of current carbon filter systems: requirement of an external stimulus, such as light or electrical energy, for the formation of ROS. Thus, the above observations may prove to be the basis of a technology that allows self-disinfection of water within contact times for which conventional carbon filters are ineffective.

Light-induced coupling process of Fe redox cycling and natural dissolved organic matters oxidative decomposition at goethite surface: Key role of reactive oxidative species

The interactions between widespread iron (oxyhydr)oxides (Fe oxides) and natural soil dissolved organic matters (DOM) are the dominant drivers in the geochemical behavior of Fe and the cycle of carbon in soil. Under visible light irradiation, their interactions become more complex due to the unique semiconducting structure of Fe oxides and complex components in DOM, which have not been deeply studied. In this study, the complex reactions occurred at the DOM-goethite interface under irradiation were investigated in detail. Fe2+(aq) from goethite reductive dissolution was accumulated at the DOM-goethite interface, along with the generation of reactive oxidative species (ROS). The reasons could be ascribed to the enhanced generation of photoelectron from the conduct band of goethite, ligand-to-metal charge transfer and photolysis of Fe(III)-carboxylate complexes. Moreover, the generated ROS were the main driving forces in the coupling process of Fe redox cycle and oxidative decomposition of DOM at goethite surface, inducing the formation of secondary Fe minerals and chemical composition change of DOM. This work provided new insights into the light-induced coupling process of Fe semiconducting minerals reductive dissolution and dissolved organic matters oxidation in top soil.