Radical Oxidation Research Articles

In situ biomass burning enhanced the contribution of biogenic sources to sulfate aerosol in subtropical cities

Sulfurous gases released by biogenic sources play a key role in the global sulfur cycle. However, the contribution of biogenic sources to sulfate aerosol in the urban atmosphere has received little attention. Emission sources and formation process of sulfate in Guangzhou, a subtropical mega-city in China, were clarified using multiple methods, including isotope tracers and chemical markers. The δ18O of sulfate suggested that secondary sulfate was the dominant component (84 %) of sulfate aerosol, which mainly formed by transition metal ion (TMI) catalyzed oxidation (31 %) and OH radical oxidation (30 %). The factors driving secondary sulfate formation were revealed using a tree boosting model, which suggested that NH3, temperature, and oxidants were the most important factors. The δ34S of sulfate indicated that biogenic sources accounted for annual average of 26.0 % of the sulfate, which increased to 30.4 % in winter monsoon period. Rice straw burning enhanced sulfate formation by promoting the release of reduced sulfur from soil, which is rapidly converted into sulfate under a subtropical urban atmosphere with high concentration of NH3 and oxidants. This study revealed the important influence of rice straw burning on biogenic sulfur emission during the rice harvest, thereby providing insight into the sulfur cycle and regional air pollution.

Peculiarities of the morpho-physiological reactions of mosses depending on the water-temperature regime of their local growth

The morphological structure of and the activity of the catalase of mosses Ptychostomum imbricatulum and Brachythecium rutabulum depending on microclimatic conditions of their local growth were studied. The morphological variability of moss turfs in different ecological conditions of forest ecosystems was established, in particular, the influence of the level of moisture in local growth on the morphometric parameters of mosses (the density of the turf, the height of the shoots and their foliage and the size of the leaves) was revealed. It is shown that the morphological structure of the turfs of the mosses Ptychostomum imbricatulum and Brachythecium rutabulum is important for moisture conservation and depends on the microclimatic conditions of local growth and the life form of the species. It is shown that the increase in the content of hydrogen peroxide as a signaling mediator is a component of the antioxidant protection system. It was established that the highest content of hydrogen peroxide was in shoots of P. imbricatulum from the territory of pine plantations, where the microclimatic conditions are the least favorable. The obtained results indicate the existence of interdependence between the formation of reactive oxygen species and the activity of catalase as one of the key enzymes of antioxidant protection, which indicates the signaling role of reactive oxygen species in moss cells under stress conditions. The dependence of catalase activity in moss cells on the level of hydration of their turfs was established. The activation of catalase in adverse water and temperature conditions in the shoots of the studied species indicates the participation of the enzyme in the adaptation of plants to stress and is due to the strengthening of free radical oxidation processes, in particular, an increase in the content of hydrogen peroxide.

The Role of Polyphenolic Antioxidants from Tea and Rosemary in the Hydroxyl Radical Oxidation of N-Acetyl Alanine.

In dead biological tissues such as human hair, the ability of antioxidants to minimise autoxidation is determined by their chemical reactions with reactive oxygen species. In order to improve our understanding of factors determining such antioxidant properties, the mechanistic chemistry of four phenolic antioxidants found in tea and rosemary extracts (epicatechin, epigallocatechin gallate, rosmarinic and carnosic acids) has been investigated. The degradation of N-acetyl alanine by photochemically generated hydroxyl radicals was used as a model system. A relatively high concentration of the antioxidants (0.1 equivalent with respect to the substrate) tested the ability of the antioxidants to intercept both initiating hydroxyl radicals (preventive action) and propagating peroxyl radicals (chain-breaking action). LC-MS data showed the formation of hydroxylated derivatives, quinones and hydroperoxides of the antioxidants. The structure of the assignment was aided by deuterium exchange experiments. Tea polyphenolics (epicatechin and epigallocatechin gallate) outperformed the rosemary compounds in preventing substrate degradation and were particularly effective in capturing the initiating radicals. Carnosic acid was suggested to act mostly as a chain-breaking antioxidant. All of the antioxidants except for rosmarinic acid generated hydroperoxides which was tentatively ascribed to the insufficient lability of the benzylic C-H bond of rosmarinic acid.

Antimicrobial and Antioxidant Activity Screening of Mushrooms Growing in the Leningrad Region

Introduction. The emergence of new strains of microorganisms that are multidrug resistant (MDR) in relation to the antimicrobial drugs used is one of the pressing problems of modern medicine. To prevent an increase in MDR-related deaths, the search for new antibiotics and their introduction into medical practice must be continuously ongoing. Infectious diseases are also accompanied by cell damage and the development of free radical oxidation processes, therefore the search for new antioxidants is also an important task. Considering the powerful biosynthetic potential of basidiomycetes, this group of fungi has every prospect of becoming a new source of biologically active substances in general, as well as antibiotics and antioxidants in particular. Cap mushrooms, represented mainly by basidiomycetes, number about 14,000 species and are an accessible source of raw materials for the search for promising antimicrobial compounds and antioxidants.Aim. Study of the antioxidant and antimicrobial activity of total extracts obtained from cap mushrooms against Escherichia coli, Staphylococcus aureus and Candida albicans and assessment of the suitability of cap mushrooms as a natural source of substances with antimicrobial and antioxidant activity.Materials and methods. The antifungal and antibacterial activity of the extracts was determined by the micromethod of two-fold serial dilutions in a liquid nutrient medium in 96-well plates in duplicate. The study of this type of biological activity was carried out against reference (type) strains Staphylococcus aureus ATCC 6538-P, Escherichia coli ATCC 25922, Candida albicans NCTC 885-653. To study antioxidant activity using DPPH, we used alcoholic extracts from the fruiting bodies of mushrooms obtained by maceration with 96 % ethanol at a ratio of raw materials to extractant of 1 to 8 for 24 hours, an aqueous solution of ascorbic acid (vitamin C) and an ethanol solution of Trolox.Result and discussion. In relation to S. aureus, a representative of gram-positive flora, the studied extracts of cap mushrooms showed low activity, on average about 2500 or 5000 μg/ml. In relation to E. coli, a representative of gram-negative flora, 8 % of the studied cap mushroom extracts showed an average activity of about 1250 μg/ml. The largest number of cap mushroom extracts – 19% of all studied species – showed activity against the yeast micromycete C. albicans. The highest activity against C. albicans was observed in extracts of the mushrooms Cantharellula umbonata with an MIC of 625 μg/ml, Cortinarius olivaceofuscus with an MIC of 625 μg/ml, and Hypomyces chrysospermus with an MIC of 312 μg/ml. During screening of antioxidant activity, the studied extracts were divided into three groups: with high (more than 50 % PPR), medium (from 15 to 50 % PPR) and low (less than 15 %) antioxidant activity. It was shown that the sum of phenolic compounds significantly correlates with the level of antioxidant activity in all three groups, but in the groups with medium and low antioxidant activity there are also other non-phenolic groups of compounds that make a significant contribution to the total antioxidant activity.Conclusion. Cap mushrooms are a promising source of biologically active substances with antifungal and antioxidant activity.

Anodic abatement of glyphosate on Pt-doped SnO2–Sb electrodes promoted by pollutant-dopant electrocatalytic interactions

The development of non-expensive and efficient technologies for the elimination of Glyphosate (GLP) in water is of great interest for society today. Here we explore novel electrocatalytic effects to boost the anodic oxidation of GLP on Pt-doped (3-13met%) SnO2–Sb electrodes. The study reveals the formation of well disperse Pt nanophases in SnO2–Sb that electrocatalyze GLP elimination. Cyclic voltammetry and in-situ spectroelectrochemical FTIR analysis evidence carboxylate-mediated Pt-GLP electrocatalytic interactions to promote oxidation and mineralization of this herbicide. Interestingly, under electrolytic conditions Pt effects are proposed to synergistically cooperate with hydroxyl radicals in GLP oxidation. Furthermore, the formation of by-products has been followed by different techniques, and the studied electrodes are compared to commercial Si/BDD and Ti/Pt anodes and tested for a real GLP commercial product. Results show that, although BDD is the most effective anode, the SnO2–Sb electrode with a 13 met% Pt can mineralize GLP with lower energy consumption.

Prognosis of pregnancy and perinatal outcomes in the presence of polycystic ovary syndrome

Aim. To determine prognostic criteria for pregnancy complications and perinatal pathology in women with polycystic ovary syndrome.Materials and methods. A prospective study of 100 pregnant women with polycystic ovary syndrome at the St. Joasaph Belgorod Regional Clinical Hospital. Depending on the type of ART method, 2 groups were formed. The first group (n=50) of women – pregnancy occurred by induction of ovulation with chlorthyanisene clomiphene citrate (CC). The second group (n=50) – with the help of In vitro fertilisation (IVF). Research methods – clinical, laboratory, instrumental.Result. It was revealed that the main conditions for the probability of the formation of polycystic ovary syndrome and infertility are: the presence of childhood infections in the anamnesis, low birth weight of mothers. Disorders of the reproductive system in polycystic ovary syndrome (PCOS) are detected by menstrual cycle disorders, late menarche, inflammatory diseases of the genitals, primary and secondary infertility. Extragenital pathology is diagnosed in 100 % of women with PCOS and appears in the form of obesity, infectious and inflammatory diseases, infectious and inflammatory pathologies. With PCOS, miscarriage, preeclampsia, isthmic-cervical insufficiency, gestational diabetes mellitus, fetal growth retardation, chronic placental insufficiency are noted. The onset of pregnancy by stimulating ovulation of CC has an unfavorable course relative to IVF: the risk of miscarriage and isthmic-cervical insufficiency is higher. The average weight of full-term babies, the method of their birth turned out to be IVF, is greater than ovulation stimulation. The probability of perinatal damage against the background of ovulation stimulation exceeds IVF by about 1.5 times. In the early period of gestation and in conditions of PCOS, there is a hormonal imbalance: a fascination with TBG and a decrease in the secretion of PAMG in peripheral blood at 7–8 and 10–12 weeks. In women with polycystic ovary syndrome, the probability of termination of pregnancy in the first trimester is characterized by the presence of chorionitis, a decrease in the volume of the amniotic cavity, tachycardia of the embryo. Signs of placental insufficiency were detected in the II and III trimesters. In pregnant women with PCOS, hemostatic disorders are observed – a shortening of the activated recalcification time and blood clotting time and an increase in fibrinogen and prothrombin index. Pregnancy on the background of PCOS is accompanied by activation of free radical oxidation and the development of oxidative stress.Conclusion. To predict placental insufficiency, the risk of miscarriage, perinatal pathology of the nervous system in pregnant women with PCOS, it is necessary to assess the level of glycodelin, TBG, PAMG‑1, β-HCG.

Revolutionizing Bone Regeneration: A Comprehensive Review On Bone Grafts

Herbal medicines are plant-based medicines and have been documented 4000 years back. Great results have beenextracted from several studies with a minimum amount of side effects. These medicines help osteogenesis as the bone graftsobtained from such are utilized as a filler and scaffold. Such grafts are bioresorbable and do not possess any reaction like antigenantibodies. The aim is to have a comprehensive review study on bone grafts. This review article covers a combination of allaspects regarding bone grafts and their different forms of availability. The Objectives of this review are to explore various bonegrafts and to summarize them so that the reader can have enough information just by reading this article. The article givesthorough information about bone grafts and mainly focuses on several ethnopharmacological studies collected using databasessuch as Pubmed, Medline, Scopus, and Google Scholar. Regarding their osteogenic, angiogenic, anti-inflammatory, and remodelingeffects, acting on bone receptors, promoting bone metabolism, increasing mineral uptake, and supporting free radical oxidation,Chenopodium ambrosioides, Piper sarmentosum, Quadrangularis Cissus, Ricinus communis, and Radix salviae miltiorrhizaeplants were the most extensively studied in several works of literature. This article concludes that using herbal bone grafts onthe site of a defect holds promise for bone regeneration and offers an alternative to conventional therapies when they areimpractical. Very few studies have been conducted to date and this has raised interest in using herbal bone grafts.

Differences in Structural Changes and Pathophysiological Effects of Low-Density Lipoprotein Particles upon Accumulation of Acylhydroperoxy Derivatives in Their Outer Phospholipid Monolayer or upon Modification of Apoprotein B-100 by Natural Dicarbonyls.

Nanoparticles of the lipid-transporting system of the organism, low-density lipoproteins (LDL) of blood plasma, are prone to free radical peroxidation with formation of their main modified forms - oxidized LDL itself (containing hydroperoxy-acyls in phospholipids of the outer layer of particles) and dicarbonyl-modified LDL (apoprotein B-100 in which chemically modified via the Maillard reaction). Based on the study of free radical oxidation kinetics of LDLs, it was found that the existing in the literature designation of "oxidized lipoproteins" is incorrect because it does not reveal the nature of oxidative modification of LDLs. It was shown in this study that the "atherogenic" LDLs (particles of which are actively captured by the cultured macrophages) are not the oxidized LDL (in which LOOH-derivatives of phospholipids are formed by enzymatic oxidation by C-15 lipoxygenase of rabbit reticulocytes), but dicarbonyl-modified LDLs. Important role of the dicarbonyl-modified LDLs in the molecular mechanisms of atherogenesis and endothelial dysfunction is discussed.

The State of the LPO-AOD System and the Relative Length of Telomeric Repeats in the Chromosomes of Blood Leukocytes in Obstructive Sleep Apnea Syndrome.

We analyzed the relative length of telomeric repeats in peripheral blood leukocytes and indicators of oxidative stress in 32 men (mean age 51.2±3.1 years) with obstructive sleep apnea syndrome (OSAS). The control group consisted of volunteers without OSAS. The relative length of telomeres was determined in a DNA sample isolated from venous whole blood samples. The length of telomeric repeats of chromosomes was determined using quantitative real-time PCR (3 times for each DNA sample); albumin served as an internal control. The intensity of LPO processes and antioxidant protection was assessed by conventional spectrophotometric methods. It was found that in patients with OSAS, the relative length of telomeric repeats was lower by 48%, the levels of substrates and products of LPO were higher (double bonds and diene conjugates by 34 and 19%, respectively), and antioxidant protection indicators were lower (concentrations of fat-soluble vitamins α-tocopherol and retinol by 18 and 19.3%, respectively, total antioxidant activity by 32.9%) than in volunteers of the control group. Thus, we can conclude that the nucleotide sequences are reduced in patients with OSAS under conditions of intensified free radical oxidation.

Regulating the peroxymonosulfate activation on N doped δ-MnO2 nanosheets for tetracycline degradation: N species as the degradation pathways switcher to convert radical to nonradical

Although the free radical pathway can obtain high organic degradation efficiency during advanced oxidation processes, it is difficult to cater the diverse degradation environment due to the coexistence of various interference. Here, the δ-MnO2 nanosheets are prepared to regulate the reactive oxidation species converting from radical-dominated to nonradical-dominated through the nitrogen doped operation in a gentle mechanical stirring method. The optimal 0.5 N-MnO2 materials present 91.2 % TC degradation efficiency in the presence of peroxymonosulfate (PMS) with the apparent rate constant is 0.63 min−1, which is 1.66 and 4.2 times higher than that of in δ-MnO2/PMS (0.38 min−1) and alone PMS (0.15 min−1) systems,respectively. Radicals quenching experiments, electron paramagnetic resonance spectra and competing kinetics experiments indicate that the δ-MnO2 nanosheets promote PMS decomposition with attaining a high radical (SO4·-, ·OH and ·O2–) oxidation path contribution (74.5 %) for TC degradation. Meanwhile, the doping of N species and electrons contribute to the generation of 1O2, allowing the whole reactive system dominated by a nonradical species (e- and 1O2) pathway (80.3 %). Importantly, electrochemical tests verify the participation of electrons and the electrons transfer from TC to the 0.5 N-MnO2 surface for PMS activation via 0.5 N-MnO2-PMS* surface complex. Overall, it is practical to cater the specific application of advanced oxidation processes through N as the degradation pathways switcher.

Does Insulin Resistance Contribute to Neuroinflammation, Cognitive Decline and Brain Senescence in Obesity?

The burgeoning prevalence of obesity and overweight conditions from the age of adolescence and throughout the lifespan has reached epidemic proportions in industrialized nations throughout the globe. The development of insulin resistance is one of the most common observations in obesity and is associated with a systemic hypoxia in adipose tissue and a chronic inflammatory state. The insulin resistance affects multiple elements of substrate oxidation and oxidative free radical generation in both somatic and neural tissues and with cytokine-linked chronic inflammation likely originating in adipose tissue depots. In studies with aging congenic lean and obese rats chronic hyperinsulinemia and brain shrinkage has now been reported, albeit it in the absence of Type 2 diabetes (NIDDM), hypertension (HTN) or other comorbidities, thereby suggesting that aspects of disordered substrate metabolism including insulin resistance as commonly observed in obesity may be a key contributory factor in the development of a neuroinflammatory linked brain shrinkage with accompanying decreases in brain mass, protein and DNA content, and which were further compromised when fed an isocaloric high vs. a low glycemic insulinogenic diet containing sucrose vs. cornstarch respectively. These results suggest that chronic insulin resistance of obesity secondary at least in part to dietary factors represents a likely independent risk factor in the progression of neuroinflammation, DNA damage, brain shrinkage and neural senescence in this strain of obese rats.

Morphological changes in liver tissues of rats under the exposure of ecotoxicants and perinatal prophylaxis

BACKGROUND: The high sensitivity of the liver to chemicals is due to its leading role in their metabolism. During the biotransformation of ecotoxicants, highly reactive intermediate products may be formed and free radical oxidation may be initiated, which may result in liver damage.
 MATERIALS AND METHODS: The experiment was carried out on outbred white rats weighing 180250 g. A total of 50 animals were involved in the experiment. All animals were divided into 5 groups: control and 4 experimental ones. All rats in the experimental groups were subjected to inhalation exposure to gasoline and formaldehyde vapors. In the 1st (control) group only poisoning with ecotoxicants was used, in the 2nd group peptinsorbent (apple pectin) was used against the background of poisoning with ecotoxicants, in the 3rd group a membrane protector lemongrass, in the 4th group a beets, in the 5th experimental group peptinsorbent, membrane protector and beets. We examined pieces of liver and rats that were subjected to histological processing. Using a LEICA RM 2145 rotary microtome (Leica Microsystems, Germany), histological sections with a thickness of 58 m were prepared. Stained sections were examined and photographed using an Axio Imager Z1 light microscope (Carl Zeiss, Germany).
 RESULTS: The liver structure of rat pups born from female rats exposed to subchronic gasoline and formaldehyde poisoning throughout pregnancy has pronounced pathomorphological signs characteristic of hepatosis, turning into toxic hepatitis. The use of lemongrass, peptinsorbent and beets separately, along with intoxication of pregnant rats, somewhat reduced the degree of pathomorphological changes in the liver of born rat pups, but not dramatically. When using a combined mixture (apple pectin + membrane protector lemongrass + beets), the liver structure of the rat pups subsequently born was preserved relatively better than in the control group, with the exception of certain areas of the liver in which hemostasis and moderately pronounced dystrophic changes in hepatocytes were detected.
 CONCLUSIONS: The combined mixture (apple pectin + membrane protector lemongrass + beets) has a more pronounced hepatoprotective effect compared to the separate use of each of its constituent substances and is effective as a hepatoprotective agent for liver damage from ecotoxicants.

Assessment of the glutathione system and the biomolecules oxidation products contribution to the state of free radical homeostasis in women of two ethnic groups with insomnia

Own and literature data showed a change in the free radical oxidation products and indicators of the glutathione system concentration in menopausal women with insomnia. The change in the studied parameters depended on the ethnicity of the patients. The aim of the study was to assess the informative value of these indicators and their contribution to the state of free radical homeostasis in menopausal women of Russian and Buryat ethnic groups with insomnia. Material and methods. The study involved women of the menopausal period of the Russian (n = 136) and Buryat ethnos (n = 94). The women underwent a general clinical examination and a questionnaire. Then they were divided into climacteric phases, control groups and groups with insomnia. Enzyme immunoassay, spectrophotometric and fluorometric methods of analysis were used to determine values of glutathione system and biomolecule oxidation products. The informative value of the studied indicators and their contribution to the state of free-radical homeostasis was assessed with the help of discriminant analysis. Results and discussion. The most informative indicators in the group of Russian women with insomnia in perimenopause were content of advanced glycation end products (AGEs), advanced oxidation protein products (AOPP), products of DNA oxidative modification, oxidized glutathione, glutathione reductase activity; in postmenopause – concentration of AOPP, products of DNA oxidative modification, and glutathione reductase activity. In Buryat perimenopausal women the most informative values were content of AGEs, of reduced and oxidized glutathione and their ratio, and in postmenopause – content of AGEs, of oxidized glutathione and glutathione reductase activity. Mathematical models have been developed that demonstrate the prevalence of the redox balance prooxidant component contribution in Russian ethnic group and the antioxidant component in Buryat ethnic group and allow characterizing patients with insomnia with high accuracy depending on the phase of menopause and ethnicity. Conclusions. In women of the Russian ethnic group with insomnia in the menopausal period, the greatest contribution to the state of free radical homeostasis is made by the products of oxidation of biomolecules, which characterizes the predominance of the processes of disadaptation. In women of the Buryat ethnic group, in response to insomnia in the climacteric period, the components of the glutathione system make the greatest contribution to the state of free radical homeostasis, which characterizes the activation of adaptive capabilities throughout the climacteric period.

Cobalt in ZIF-8-ZIF-67 as dual catalyst for ZnO–Co3O4/C formation and Bisphenol A degradation with persulfate

Composited zeolitic imidazolate framework-8-67 (ZIF-8-ZIF-67 and ZIF-8/ZIF-67) solids were synthesized via two processes, which resulted in different cobalt content in the solids. The experimental results suggested that the cobalt content in the solids had a significant influence on the transformation from ZIF to the corresponded composited oxides and catalytic performances. It was revealed from the composition and structure analysis that the cage-like cobalt oxide-zinc oxide/carbon composite (Co3O4–ZnO/C) derived from the ZIF-8/ZIF-67 with 9 wt% of cobalt via a two-step synthesis displayed an efficient activation of persulfate to decompose the Bisphenol A (BPA) as well as a robust reusability compared with the solid obtained by one-step synthesized ZIF-8-ZIF-67 with a cobalt content of 0.8 wt%, which displayed no catalytic activity. It was proposed that the Co3O4–ZnO/C facilitated the electrons transfer in the reaction system and a possible radical oxidation process occurred. Thus, the present could provide new insight for the design of composited organic framework and their functional materials for catalytic applications.

Kinetics and mechanism of dissolved organic phosphorus (DOP) digestion by the UV/O3 process

AbstractIn this study, the kinetics and mechanism of UV/O3 synergistic oxidative digestion of dissolved organic phosphorus (DOP) were investigated, focusing on the ozone direct oxidation and hydroxyl radical oxidation parts of glufosinate and triphenyl phosphate (TPhP). The p‐chlorobenzoic acid (p‐CBA) was selected as the probe compound, and two kinds of reaction kinetic models were proposed by competitive kinetic method with Rct according to the different scale of rate constants of hydroxyl radical oxidation. Under the condition of weakly alkaline (pH = 9.0) and weakly acidic environment (pH = 5.0), the second‐order rate constants of glufosinate and TPhP was determined indirectly to be ko3/glufosinate = (2.903 ± 0.247)M−1s−1 and ko3/TPhP = (3.307 ± 0.204) M−1s−1 by ozone direct oxidation, and k·OH/glufosinate = (1.257 ± 1.031) × 109 M−1s−1 and k·OH/TPhP = (7.120 × 108 ± 0.963) M−1s−1 by hydroxyl radical oxidation, respectively. The comparison of the contribution levels of the two parts to the digestion process showed that the contribution levels in the digestion of glufosinate and TPhP processes both the contribution of ·OH were higher than those of ozone, 86.3% and 72.6%, respectively.

Unveiling the spatially confined oxidation processes in reactive electrochemical membranes

Electrocatalytic oxidation offers opportunities for sustainable environmental remediation, but it is often hampered by the slow mass transfer and short lives of electro-generated radicals. Here, we achieve a four times higher kinetic constant (18.9 min−1) for the oxidation of 4-chlorophenol on the reactive electrochemical membrane by reducing the pore size from 105 to 7 μm, with the predominate mechanism shifting from hydroxyl radical oxidation to direct electron transfer. More interestingly, such an enhancement effect is largely dependent on the molecular structure and its sensitivity to the direct electron transfer process. The spatial distributions of reactant and hydroxyl radicals are visualized via multiphysics simulation, revealing the compressed diffusion layer and restricted hydroxyl radical generation in the microchannels. This study demonstrates that both the reaction kinetics and the electron transfer pathway can be effectively regulated by the spatial confinement effect, which sheds light on the design of cost-effective electrochemical platforms for water purification and chemical synthesis.

Molecular Composition of Anthropogenic Oxygenated Organic Molecules and Their Contribution to Organic Aerosol in a Coastal City.

Organic aerosols (OA) have gained attention as a substantial component of atmospheric aerosols owing to their impact on atmospheric visibility, climate, and human health. Although oxygenated organic molecules (OOMs) are essential contributors to OA formation, the sources, transformations, and fates of the OOMs are not fully understood. Herein, anthropogenic OOMs (AOOMs), anthropogenic volatile organic compounds (AVOCs), and OA were concurrently measured in Xiamen, a coastal city in southeastern China. Our results show that the AOOMs exhibited a high nitrogen content (76%) and a low oxidation degree. Strong photochemical processes of aromatic VOCs were the predominant sources of AOOMs. Also, NOx concentrations and the occurrence of multigeneration OH radical oxidations were the critical factors that might influence the formation of AOOMs. Finally, the newly developed aerosol dynamic model's results show that more than 35% of the OA mass growth rate is attributed to the gas-particle partitioning of AOOMs. Further sensitivity testing demonstrates that the contribution of AOOMs to OA growth is significantly enhanced during high-particulate-concentration periods, especially under low-temperature conditions. This study emphasizes the vital role of photochemically produced AOOMs derived from AVOCs in OA growth in a coastal urban atmosphere.

Key role of La in La@nZVI/rGO for the efficient and steady PMS activation towards ofloxacin degradation via a non-radical process

The nano zero-valent iron (nZVI)/peroxymonosulfate (PMS)-based advanced oxidation processes (AOPs) are promising for removal of antibiotic contaminants in groundwater. However, the inherent defects of rapid passivation and inactivation limit the efficient and steady application of nZVI. Herein, the lanthanum@nZVI/rGO (La@nZVI/rGO) was synthesized in which nZVI was coated with La and distributed evenly on reduced graphene oxide (rGO) matrix. The introduction of La coating protected the nZVI from direct contact with PMS molecules thus the La@nZVI/rGO appeared efficient and steady activization of PMS to degrade ofloxacin (OFX) without rapid inactivation. The removal rate was promoted to 96.5 % compared with the uncoated nZVI/rGO (only 85.2 %). The degradation reaction represented steady and continuous activation of PMS with pseudo-first-order kinetics (0.0451 min−1). While the two-stage kinetics of nZVI/rGO/PMS with initial 0.2581 min−1 and instant 0.0024 min−1 resulted from the rapid inactivation of nZVI. The reaction of La@nZVI/rGO/PMS exhibited minimal leaching of Fe ions (less than 1.8 µg/L) while it reached 6.4 mg/L in nZVI/rGO/PMS. XRD and XPS analyses further demonstrated the excellent durability of La@nZVI/rGO and the obvious passivation of nZVI/rGO. ESR and quenching tests confirmed that La coating regulated the PMS activation and ROS generation mechanism. The degradation was dominated by 1O2-induced non-free radical process in La@nZVI/rGO/PMS system and different from radical oxidation in nZVI/rGO/PMS. Moreover, the dissolved oxygen and XPS analysis revealed the important role of La coating and oxygen vacancy in the catalytic degradation. This work could provide a novel understanding of the nZVI with protective coating in AOPs environmental remediation.

Enhanced nitenpyram degradation by metallic carbon nitrogen composites catalyzed peroxymonosulfate: Synergistic effect of radical and nonradical pathways

Identifying the key active site for peroxymonosulfate (PMS) activation in metallic carbon nitrogen mixtures (MCN) is essential for the optimization of catalyst preparation strategy. Herein, we utilized a pyrolysis method to fabricate MCN for peroxymonosulfate (PMS) activation. The optimal MCN − 700/PMS system showed outstanding catalytic activity for multiple pollutants, and strong resistance to pH (3–11) and complex water environment. Combined with density functional theory calculations, we confirmed the structure − function relationships between different active sites in MCN and PMS. PMS would be preferentially adsorbed on Mn5C2 and Fe2N of MCN − 700, followed by the stretch and fracture of peroxides O − O of the adsorbed PMS. The superior stability could be attributed to that MCN has a continuous N − doped carbon shell structure that promoted electron transfer and encapsulated metal components like an armor. The MCN − 700/PMS system possessed extraordinary degradation activity in complex aqueous environment and various refractory organic pollutants can be efficiently removed, exhibiting the great merits of the radical and nonradical synergistic oxidation. The findings provided new insights into the reaction mechanisms of MCN/PMS system and the rational design heterogeneous PMS systems involving the synergistic action of radical and nonradical oxidation.

Hydroxyl Radical vs. One-Electron Oxidation Reactivities in an Alternating GC Double-Stranded Oligonucleotide: A New Type Electron Hole Stabilization.

We examined the reaction of hydroxyl radicals (HO•) and sulfate radical anions (SO4•-), which is generated by ionizing radiation in aqueous solutions under anoxic conditions, with an alternating GC doubled-stranded oligodeoxynucleotide (ds-ODN), i.e., the palindromic 5'-d(GCGCGC)-3'. In particular, the optical spectra of the intermediate species and associated kinetic data in the range of ns to ms were obtained via pulse radiolysis. Computational studies by means of density functional theory (DFT) for structural and time-dependent DFT for spectroscopic features were performed on 5'-d(GCGC)-3'. Comprehensively, our results suggest the addition of HO• to the G:C pair moiety, affording the [8-HO-G:C]• detectable adduct. The previous reported spectra of one-electron oxidation of a variety of ds-ODN were assigned to [G(-H+):C]• after deprotonation. Regarding 5'-d(GCGCGC)-3' ds-ODN, the spectrum at 800 ns has a completely different spectral shape and kinetic behavior. By means of calculations, we assigned the species to [G:C/C:G]•+, in which the electron hole is predicted to be delocalized on the two stacked base pairs. This transient species was further hydrated to afford the [8-HO-G:C]• detectable adduct. These remarkable findings suggest that the double-stranded alternating GC sequences allow for a new type of electron hole stabilization via delocalization over the whole sequence or part of it.