Long-term Application of Agricultural Amendments Regulate Hydroxyl Radicals Production during Oxygenation of Paddy Soils.

Hydroxyl radicals (•OH) play a significant role in contaminant transformation and element cycling during redox fluctuations in paddy soil. However, these important processes might be affected by widely used agricultural amendments, such as urea, pig manure, and biochar, which have rarely been explored, especially regarding their impact on soil aggregates and associated biogeochemical processes. Herein, based on five years of fertilization experiments in the field, we found that agricultural amendments, especially coapplication of fertilizers and biochar, significantly increased soil organic carbon contents and the abundances of iron (Fe)-reducing bacteria. They also substantially altered the fraction of soil aggregates, which consequently enhanced the electron-donating capacity and the formation of active Fe(II) species (i.e., 0.5 M HCl-Fe(II)) in soil aggregates (0-2 mm), especially in small aggregates (0-3 µm). The highest contents of active Fe(II) species in small aggregates were mainly responsible for the highest •OH production (increased by 1.7-2.4-fold) and naphthalene attenuation in paddy soil with coapplication of fertilizers and biochar. Overall, this study offers new insights into the effects of agricultural amendments on regulating •OH formation in paddy soil and proposes feasible strategies for soil remediation in agricultural fields, especially in soils with frequent occurrences of redox fluctuations.

Silicon carbide single crystals for high-temperature supercapacitors.

Designing advanced electrode materials that can be reliably cycled at high temperatures and used for assembling advanced energy storage devices remain a major challenge. As a representative of novel wide bandgap semiconductors, silicon carbide (SiC) single crystals have broad prospects in high-temperature energy storage due to their excellent characteristics such as low thermal expansion coefficient, high temperature radiation resistance and stable chemical properties. In this work, an N-type SiC single-crystal material with a high-density porous structure was successfully designed and prepared by using an improved electrochemical anodic oxidation strategy. Besides, the N-type SiC single crystals were used in electrochemical energy storage as an integrated electrode material, exhibiting superior electrochemical performance. In addition, the high-temperature supercapacitor device assembled with ionic liquids has a wide operating temperature range and maintains a capacity of 88.24% after 5000 cycles at 150 °C. The reasons for its high energy storage performance are discussed through electrochemical tests and first-principles calculation methods. This study proves that the application of SiC single crystals in supercapacitor devices has great potential in the field of high-temperature energy storage, providing a reference for the further development of novel semiconductors in the field of energy storage and optoelectronic devices.

The Expression of miR-377-3p in Patients with DKD and the Regulatory Mechanism of miR-377-3p on the Inflammatory Response of HK-2 Cells Through TGF-ß.

Objective: The purpose of the study was to investigate the expression levels and correlation of inflammatory factors such as miR-377-3p and TGF-ß in patients with diabetic kidney disease (DKD), and to investigate the regulatory mechanism of transfection of miR-377-3p on the inflammatory response of HK-2 cell induced by high glucose. Methods: According to UACR, patients were divided into normal albuminuria group (Con, n = 29), microalbuminuria group (Micro, n = 31) and macroalbuminuria group (Macro, n = 30), analyzed the correlation and influencing factors between DKD and inflammatory factor. HK-2 cells were randomly divided into four groups: normal control group (NC), high glucose group (HG), miR-377-3p overexpression group (MIN), and miR-377-3p inhibition group (IN). After transfection of miR-377-3p mimics and inhibitors, the contents of TGF-ß, IL-6 and IL-18 were detected by RT-PCR and Western blot. Results: The levels of miR-377-3p, TGF-ß, IL-6 and IL-18 in both Micro group and Macro group were significantly higher than those in Con group (P < 0.05); Pearson correlation analysis showed that miR-377-3p was positively correlated with UACR, TG, TGF-ß, IL-6 and IL-18, and negatively correlated with GFR (P < 0.05). Cell experiment: RT-PCR and Western blot results showed that miR-377-3p, TGF-ß, IL-6 and IL-18 in HG group were significantly higher than those in NC group (P < 0.05). After transfection with miR-377-3p inhibitor, the levels of miR-377-3p, TGF-ß, IL-6 and IL-18 in IN group were significantly decreased compared with HG group and MIN group. Conclusion: miR-377-3p expression was elevated both in serum of DKD patients and in HK-2 cells with high glucose induced injury, overexpression of miR-377-3p exacerbates the damage to HK-2 cells and promotes the progression of DKD. Silencing miR-377-3p can potentially regulate the levels of inflammatory factors in HK-2 cells by targeting downregulation of TGF-ß expression, thereby mitigating the damage to HK-2 cells and delaying the development of diabetic kidney disease.

The predictive value of miR-377 and phospholipase A2 in the early diagnosis of diabetic kidney disease and their relationship with inflammatory factors.

OBJECTIVE: The value of novel biomarkers for DKD has received increasing attention, and there is an urgent need for novel biomarkers with sensitivity, specificity and ability to detect kidney damage.miR-377 regulates many basic biological processes, plays a key role in tumor cell proliferation, migration and inflammation, and can also increase the expression of matrix proteins and fibronectin, leading to renal tubulointerstitial inflammation and renal fibrosis. Lipoprotein-associated phospholipase A2, as an inflammatory marker, is involved in the pathological process of microalbuminuria production and renal function decline, and is a predictive factor of microalbuminuria production and renal function decline, and can be used as an indicator to evaluate the progression of DKD.The aim of this study was to investigate the effects of miR-377 and phospholipase A2 on the development of diabetic kidney disease through regulation of inflammatory factors and the mechanism of action. METHODS: 80 diabetic patients were divided into two groups according to urinary albumin-to-creatinine ratio (UACR): diabetic normal proteinuria group (n = 42) and diabetic proteinuria group (n = 38). Forty-three healthy people were selected as the normal control group. The serum levels of TGF-ß, IL-6, and IL-18 were measured by ELISA, miR-377 was detected by qPCR, and the serum levels of phospholipase A2 were detected by electrochemiluminescence. Analyze the correlation of study group indicators, ROC curve was used to evaluate the diagnostic efficacy of miR-377 and phospholipase A2 in diabetic kidney disease. RESULTS: The average levels of serum TGF-ß, IL-6, IL-18, miR-377 and phospholipase A2 in diabetic proteinuria group were significantly higher than those in normal control group and diabetic proteinuria normal group(P < 0.05). miR-377, phospholipase A2 were significantly correlated with inflammatory factors such as glomerular filtration rate and TGF-ß. miR-377 and phospholipase A2 are independent predictors of diabetic kidney disease. The area under the curve of miR-377 and phospholipase A2 in the normal diabetic proteinuria group and the diabetic proteinuria group were 0.731 and 0.744, respectively. CONCLUSION: miR-377 and phospholipase A2 have good diagnostic efficiency for the early diagnosis of diabetic kidney disease. They can be used as early biomarkers.miR-377 and phospholipase A2 were positively correlated with inflammatory factors and involved in the occurrence and development of diabetic kidney disease.

Effects of varying amounts of different biochars on mercury methylation in paddy soils and methylmercury accumulation in rice (Oryza sativa L.).

There is growing evidence for the potential of biochars (BCs) in remediating mercury-contaminated paddy soils, but the high doses commonly used in laboratory studies discourage BC application in practice. To address these difficulties, we compared the effects of varying amounts of BCs from different sources on the formation of methylmercury (MeHg) in soil and its accumulation in rice through microcosm and pot experiments. The addition of a wide range of added doses (0.3, 0.6, 1, 2, 4 and 5 %, w/w) of BCs derived from different biomass feedstocks (i.e., corn stalk, wheat straw, bamboo, oak and poplar) significantly decreased the fraction of ammonium thiosulfate ((NH4)2S2O3)-extractable MeHg in the soil, although the MeHg contents varied with BC types and doses during soil incubation. However, the extractable MeHg in the soil did not continuously decrease with increasing BC doses, especially at doses of >1 %, resulting in limited further reductions. Moreover, a relatively low application rate (0.3-0.6 %, w/w) of BCs (i.e., corn stalk, wheat straw and bamboo-derived BC), especially of bamboo-derived BCs, significantly decreased the MeHg levels (42-76 %) in rice grains (brown rice). Meanwhile, the extractable soil MeHg decreased (57-85 %), although the MeHg in the soil varied under BC amendment during rice cultivation. These results provide further evidence that applying BC produced from different raw carbon materials (e.g., lignocellulosic biomass) could effectively reduce MeHg accumulation in rice grains, possibly due to MeHg bioavailability reduction in the soil. Our results suggest the possibility of mitigating MeHg accumulation in rice with a low dose of BCs, with great potential for use in remediating moderately contaminated paddy soils.

Promotion of IL­17/NF­κB signaling in autoimmune thyroid diseases.

IL-17 and other cytokines have a number of immunomodulatory effects on thyroid cells. The present study investigated the changes and correlations amongst IL-17, NF-κB, IL-6, IL-10, interferon-γ (IFN-γ), TNF-α, IL-2 and IL-4 in patients with different autoimmune thyroid diseases in order to further clarify the pathogenesis of autoimmune thyroid disease. A total of 82 patients with autoimmune thyroid diseases (41 with Graves' disease and 41 with Hashimoto's thyroiditis) and 53 healthy controls were enrolled. All relevant thyroid hormones were detected by electrochemiluminescence analyzer. The serum levels of IL-17 and other cytokines were detected using flow cytometry, NF-κB was detected by ELISA, reverse transcription-quantitative PCR was used to detect the protein expression of various mRNAs, and the correlations between IL-17 and these factors were analyzed. Significant differences occurred amongst all groups. NF-κB, TNF-α, IL-6, IL-17 and their mRNA levels were significantly higher in the healthy controls compared with those in the patients; whereas IFN-γ and IL-10 levels were significantly lower in the healthy controls compared with those in the patients . Correlation analysis showed that the expression levels of IL-17 and its mRNA were significantly positively correlated with the expression levels of NF-κB, IL-6, thyroid peroxidase antibody, thyroid gland globulin, thyroglobulin antibody, TNF-α and IFN-γ, and were also significantly negatively correlated with IL-10 . These findings suggested that IL-17 was elevated in patients with autoimmune thyroid disease and that IL-17 could activate the NF-κB signaling pathway, stimulate the production and release of inflammatory factors such as TNF-α, IL-6 and IFN-γ and participate in the pathogenesis of autoimmune thyroid injury.

Changes of ACE2 in different glucose metabolites and its relationship with COVID-19.

BACKGROUND: To study the changes and effects of angiotensin-converting enzyme 2 (ACE2)/angiotensin 1-7 (Ang1-7) and ACE/AngII in people with different glucose metabolisms and to explore the possible mechanisms underlying the severity of COVID-19 infection in diabetic patients. METHODS: A total of 88 patients with type 2 diabetes, 72 patients with prediabetes (impaired fasting glucose, 30 patients; impaired glucose regulation, 42 patients), and 50 controls were selected. Changes and correlations of ACE2, Ang1-7 and other indicators were detected among the three groups. Patients were divided into four groups according to the course of diabetes: <1 year, 1-5 years, 5-10 years, and >10 years. ACE2 and Ang1-7 levels were compared and analyzed. RESULTS: ACE2 and Ang1-7 increased with the severity of diabetes (P0 < .05 or P < .01). The levels of ACE2 and Ang1-7 in the longer course group were lower than those in the shorter course group, whereas the levels of ACE, Ang II, and interleukin-6 (IL-6) gradually increased (P < .05). Pearson correlation analysis showed that ACE2 was positively correlated with IL-6, FBG, and 2hPBG levels in the prediabetes group. In the diabetic group, ACE2 was positively correlated with Ang1-7 and negatively correlated with ACE, AngII, IL-6, and C-reactive protein levels. Multiple linear regression analysis showed that IL-6 and ACE were the main factors influencing ACE2 in the diabetic group. CONCLUSION SUBSECTIONS: ACE2/Ang1-7 and ACE/AngII systems are activated, and inflammatory cytokine release increases in prediabetes. With the prolongation of the disease course, the effect of ACE2/Ang1-7 decreased gradually, while the effect of ACE/AngII increased significantly. Dysfunctions of ACE2/Ang1-7 may be one of the important mechanisms underlying the severity of COVID-19 infection in patients with diabetes.

Asymmetric Jetting during the Impact of Liquid Drops on Superhydrophobic Concave Surfaces.

The impact of liquid drops on superhydrophobic solid surfaces is ubiquitous and of practical importance in many industrial processes. Here, we study the impingement of droplets on superhydrophobic surfaces with a macroscopic dimple structure, during which the droplet exhibits asymmetric jetting. Systematic experimental investigations and numerical simulations provide insight into the dynamics and underlying mechanisms of the observed phenomenon. The observation is a result of the interaction between the spreading droplet and the dimple. An upward internal flow is induced by the dimple, which is then superimposed on the horizontal flow inside the spreading droplet. As such, an inclined jet is issued asymmetrically into the air. This work would be conducive to the development of an open-space microfluidic platform for droplet manipulation and generation.

Hydroxyl radical formation during oxygen-mediated oxidation of ferrous iron on mineral surface: Dependence on mineral identity.

Many studies have examined the redox behavior of ferrous ions (Fe(II)) sorbed to mineral surfaces. However, the associated hydroxyl radical (•OH) formation during Fe(II) oxidation by O2 was rarely investigated at circumneutral pH. Therefore, we examined •OH formation during oxygenation of adsorbed Fe(II) (Fe(II)sorbed) on common minerals. Results showed that 16.7 ± 0.4-25.6 ± 0.3 µM of •OH was produced in Fe(II) and α/γ-Al2O3 systems after oxidation of 24 h, much more than in systems with dissolved Fe(II) (Fe2+aq) alone (10.3 ± 0.1 µM). However, •OH production in Fe(II) and α-FeOOH/α-Fe2O3 systems (6.9 ± 0.1-8.3 ± 0.1 µM) slightly decreased compared to Fe2+aq only. Further analyses showed that enhanced oxidation of Fe(II)sorbed was responsible for the increased •OH production in the Fe(II)/Al2O3 systems. In comparison, less Fe(II) was oxidized in the α-FeOOH/α-Fe2O3 systems, which was probably ascribed to the quick electron-transfer between Fe(II)sorbed and Fe(III) lattice due to their semiconductor properties and induced formation of high-crystalline Fe(II) phases that hindered Fe(II) oxidation and •OH formation. The types of minerals and solution pH strongly affected Fe(II) oxidation and •OH production, which consequently impacted phenol degradation. This study highlights that the properties of minerals exert great impacts on surface-Fe(II) oxidation and •OH production during water/soil redox fluctuations.

Microfluidic Applications in Drug Development: Fabrication of Drug Carriers and Drug Toxicity Screening.

Microfluidic technology has been highly useful in nanovolume sample preparation, separation, synthesis, purification, detection and assay, which are advantageous in drug development. This review highlights the recent developments and trends in microfluidic applications in two areas of drug development. First, we focus on how microfluidics has been developed as a facile tool for the fabrication of drug carriers including microparticles and nanoparticles. Second, we discuss how microfluidic chips could be used as an independent platform or integrated with other technologies in drug toxicity screening. Challenges and future perspectives of microfluidic applications in drug development have also been provided considering the present technological limitations.

Psychosocial and behavioral correlates with HIV testing among men who have sex with men during the COVID-19 pandemic in China.

OBJECTIVES: Some of community mitigation efforts on COVID-19 created challenges to ongoing public health programs, including HIV care and prevention services among men who have sex with men (MSM). The goal of the current study was to explore sociodemographic factors and the impact of COVID-19 on HIV testing among Chinese MSM during state-enforced quarantine. METHODS: We conducted a community based survey between May 1st to June 30th, 2020 on COVID-19 related impacts on HIV testing among 436 China MSM during the COVID-19 state-enforced quarantine. RESULTS: One-third (33.7%) of MSM received HIV testing during the quarantine period. Few participants reported difficulty accessing facility-based testing (n = 13, 3.0%) or obtaining HIV self-test kit online (n = 22, 5.0%). However, 12.1% of participants reported being afraid of getting facility-based HIV test due to concerns about the risk of COVID-19. In the multivariate logistic regression model, participants who were married (aOR: 1.89, 95%CI: 1.19-3.01), reported increased quality of sleep (aOR: 2.07, 95%CI: 1.11-3.86), and increased difficulty in accessing health care (aOR: 2.34, 95%CI: 1.37-3.99) were more likely to get an HIV test during the state-enforced quarantine. CONCLUSION: The mitigation measures of COVID-19 have created various barriers to access HIV related prevention services in China, including HIV testing. To mitigate these impacts on HIV prevention and care services, future programs need to address barriers to HIV-related services, such as providing high-quality HIV self-testing. Meanwhile, psychological services or other social services are needed to those experiencing mental distress.

Influence of Different Heater Structures on the Temperature Field of AlN Crystal Growth by Resistance Heating.

Based on the actual hot zone structure of an AlN crystal growth resistance furnace, the global numerical simulation on the heat transfer process in the AlN crystal growth was performed. The influence of different heater structures on the growth of AlN crystals was investigated. It was found that the top heater can effectively reduce the axial temperature gradient, and the side heater 2 has a similar effect on the axial gradient, but the effect feedback is slightly weaker. The axial temperature gradient tends to increase when the bottom heater is added to the furnace, and the adjustable range of the axial temperature gradient of the side 1 heater + bottom heater mode is the largest. Our work will provide important reference values for AlN crystal growth by the resistance method.

Active Iron Phases Regulate the Abiotic Transformation of Organic Carbon during Redox Fluctuation Cycles of Paddy Soil.

Iron (Fe) phases are tightly linked to the preservation rather than the loss of organic carbon (OC) in soil; however, during redox fluctuations, OC may be lost due to Fe phase-mediated abiotic processes. This study examined the role of Fe phases in driving hydroxyl radical (•OH) formation and OC transformation during redox cycles in paddy soils. Chemical probes, sequential extraction, and Mössbauer analyses showed that the active Fe species, such as exchangeable and surface-bound Fe and Fe in low-crystalline minerals (e.g., green rust-like Fe phases), predominantly regulated •OH formation during redox cycles. The •OH oxidation strongly induced the oxidative transformation of OC, which accounted for 15.1-30.8% of CO2 production during oxygenation. Microbial processes contributed 7.3-12.1% of CO2 production, as estimated by chemical quenching and γ-irradiation experiments. After five redox cycles, 30.1-71.9% of the OC associated with active Fe species was released, whereas 5.2-7.1% was stabilized by high-crystalline Fe phases due to the irreversible transformation of these active Fe species during redox cycles. Collectively, our findings might unveil the under-appreciated role of active Fe phases in driving more loss than conservation of OC in soil redox fluctuation events.

Active iron species driven hydroxyl radicals formation in oxygenation of different paddy soils: Implications to polycyclic aromatic hydrocarbons degradation.

The frequently occurring redox fluctuations in paddy soil are critical to the cycling of redox-sensitive elements (e.g., iron (Fe) and carbon) due to the driving of microbial processes. However, the associated abiotic process, such as hydroxyl radical (•OH) formation, was rarely investigated. Hence, we examined the under-appreciated role of •OH formation in driving polycyclic aromatic hydrocarbons (PAHs) degradation upon oxygenation of anoxic paddy slurries. Results showed that •OH production largely differed in different paddy slurries, in the range of 271.5-581.2 µmol kg-1 soil after 12 h reaction. The •OH production was highly hinged on the contents of active Fe species, i.e., exchangeable, surface-bound Fe and Fe in low-crystalline phases rather than Fe in high-crystalline minerals or silicates. Besides, •OH production significantly decreased with increasing soil depth due to the declined active Fe species and abundance of functional microbes. Oxygenation also induced the transformation of these active Fe species into the low- and high-crystalline phases, which might affect the following redox process. The produced •OH can efficiently degrade PAHs with degradation extents depending on their physiochemical properties. Our findings highlight the key roles of active Fe species in driving •OH formation and organic contaminants degradation during redox fluctuations of paddy soils.

Time to Safeguard the Future Generations from the Omnipresent Microplastics.

Microplastics (MPs) as a ubiquitous environmental pollutant have drawn growing attention, and it is concerning that children are more sensitive to MPs than adults. Unfortunately, information about the link between children and MPs is insufficient. Therefore, we review the sources and exposure routes of children to MPs and collect evidence for the potential risks. Children can ingest and/or inhale MPs derived from various foodstuffs and plastic products. Despite the limited knowledge on the toxicity to humans, current studies have proved the accumulation and translocation of MPs in different tissues and organs. Main damages including cytotoxicity, neurotoxicity, and immunotoxicity can be caused by pristine polymers and/or co-contaminants. There is much more to be understood about MPs, especially their health effects, and this study has made it clear that it is time to protect our future generations from the threat of MPs.

Influence of Microplastics on the Mobility, Bioavailability, and Toxicity of Heavy Metals: A Review.

Microplastics (MPs) can pose ecological risk to the environment and have the potential to negatively affect human health, raising serious public concerns. It is recognized that MPs could act as a vector for various environmental pollutants including heavy metals and potentially influencing their mobility, fate, and bioavailabilty in the environment. However, knowledge on the mechanisms underpinning the interaction processes between MPs and heavy metals is far from clear. This review discusses the effects of MPs on the adsorption/desorption, speciation and bioavailability, and toxicity of various heavy metals. The present review also systematically identifies the environmental factors (e.g., pH, ionic strength, and organic matters) that could affect their interaction processes. This work aims to establish a meaningful perspective for a comprehensive understanding of the indirect ecological risks of MPs as vectors for contaminants. The work also provides a reference for the development of better regulatory strategies in mitigating the negative effects caused by the co-existence of MPs and heavy metals.

Dietary carbohydrates influence muscle texture of olive flounder Paralichthys olivaceus through impacting mitochondria function and metabolism of glycogen and protein.

The present study was conducted to estimate the effects of dietary carbohydrates on muscle quality and the underlying mechanisms. Six isonitrogenous and isolipidic diets were formulated to contain graded levels of carbohydrates (0%, 8%, 12%, 16%, 20% and 24%, respectively). These diets were named as C0, C8, C12, C16, C20 and C24, respectively. After a 10-week feeding trial, results showed that the muscle pH, liquid holding capacity (LHC) and hardness were significantly decreased by the increasing dietary carbohydrate levels. Dietary carbohydrates significantly decreased the muscle fibre diameter, and the highest value was found in the C0 group. Accumulated glycogen and degenerated mitochondrial cristae were observed in the C24 group. Significantly higher contents of protein carbonyls were observed in the C20 group and C24 group (P < 0.05). There was a significant decrease of mtDNA copy number in the C24 group compared with that in the C0 and C8 groups. The AMP/ATP ratio in muscle decreased first and then increased with the increasing dietary carbohydrate levels. The dietary incorporation of carbohydrate significantly reduced the expression of opa1, pygm and genes involved in myogenesis (myf5 and myog). Meanwhile, proteolysis-related genes (murf-1, mafbx, capn2 and ctsl), pro-inflammatory cytokines (il-6 and tnf-α) and mstn were significantly up-regulated. In the C24 group, significant increase of phosphorylation of AMPK (Thr172), up-regulation of PGC-1α and GLUT4 were observed, while the phosphorylation level of S6 (Ser235/236) was significantly decreased. It was concluded that excessive dietary carbohydrate level (24%) had negative impacts on mitochondria function and promoted glycogen accumulation, and thereafter influenced the muscle quality of olive flounder. The activation of AMPK as well as the upregulation of PGC-1α and GLUT4 was the key mechanism.

Microfluidic Technology for the Production of Well-Ordered Porous Polymer Scaffolds.

Advances in tissue engineering (TE) have revealed that porosity architectures, such as pore shape, pore size and pore interconnectivity are the key morphological properties of scaffolds. Well-ordered porous polymer scaffolds, which have uniform pore size, regular geometric shape, high porosity and good pore interconnectivity, facilitate the loading and distribution of active biomolecules, as well as cell adhesion, proliferation and migration. However, these are difficult to prepare by traditional methods and the existing well-ordered porous scaffold preparation methods require expensive experimental equipment or cumbersome preparation steps. Generally, droplet-based microfluidics, which generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels, has emerged as a versatile tool for generation of well-ordered porous materials. This short review details this novel method and the latest developments in well-ordered porous scaffold preparation via microfluidic technology. The pore structure and properties of microfluidic scaffolds are discussed in depth, laying the foundation for further research and application in TE. Furthermore, we outline the bottlenecks and future developments in this particular field, and a brief outlook on the future development of microfluidic technique for scaffold fabrication is presented.

Surface-bound radical control rapid organic contaminant degradation through peroxymonosulfate activation by reduced Fe-bearing smectite clays.

Heterogeneously activated peroxymonosulfate (PMS)-based advanced oxidation technologies (AOTs) have received increasing attention in contaminated water remediation. However, PMS activation by reduced clay minerals (e.g., reduced Fe-bearing smectite clays) has rarely been explored. Herein, PMS decomposition by reduced Fe-bearing smectite clays was investigated, and the hydroxyl radical (OH) and sulfate radical (SO4-) formation mechanisms were elucidated. Reduced nontronite NAu-2 (R-NAu-2) activated PMS efficiently to induce rapid degradation of diethyl phthalate (DEP) within 30 s. Mössbauer spectroscopy, FTIR and XPS analyses substantiated that distorted trans-coordinated Fe(II)Fe(II)Fe(II)OH entities were mainly responsible for rapid electron transfer to regenerate clay surface Fe(II) for PMS activation. Chemical probe, radical quenching, and electron paramagnetic resonance (EPR) results confirmed that OH and SO4- were mainly bound to the clay surface rather than in bulk solution, which resulted in the rapid degradation of organic compounds such as DEP, sulfamethoxazole, phenol, chlortetracycline and benzoic acid. Anions such as Cl- and NO3- had a limited effect on DEP degradation, while HCO3- inhibited the DEP degradation due to the increase of reaction pH. This study provides a new PMS activation strategy using reduced Fe-bearing smectite clays that will contribute to rapid degradation of organic contaminants using PMS-based AOTs.

Transformation of tetracyclines induced by Fe(III)-bearing smectite clays under anoxic dark conditions.

Smectite clays are widely found in subsurface soils and waters. Although they strongly sequester tetracyclines (TCs), little is known about their reactions with these antibiotics under dark anoxic conditions. This study investigated the interactions between TCs and Fe-bearing smectite clays and the influences of environmental factors. Fe-bearing smectite clays were shown to significantly induce the transformation of TCs, including tautomerization, dechlorination, and dehydration. Moreover, the adsorbed TCs reduced the structural Fe(III) in clay particles to structural Fe(II) through electron transfer. The transformation of TCs was more readily induced by smectite clays with a higher rather than a lower Fe content. Tetrahedral Fe(III), and distorted cis- or trans-octahedral Fe(III), were more reactive as an electron acceptor than cis-octahedral Fe(III), as observed on the Mössbauer and FTIR spectra. A lower pH facilitated the adsorption of TCs through dimethyl-amino, amide, and conjugated -OH functional groups and induced a higher rate of TCs transformation. The transformation of chlortetracycline (CTC) was faster than that of oxytetracycline or tetracycline (TTC) due to -Cl substitution. The major transformation CTC products included keto-CTC, epi-CTC, iso-CTC, anhydro-CTC and TTC. Mixtures of these transformed products were found to have a higher acute toxicity than their parent compounds to Photobacterium phosphoreum T3. Our study revealed several previously overlooked interactions between TCs and clay particles that could cause these antibiotics to become unstable in the subsurface environment, with negative effects on the soil-borne microbial community.