New Barrier Role of Iron Plaque: Producing Interfacial Hydroxyl Radicals to Degrade Rhizosphere Pollutants.

Iron plaque, as a natural barrier between rice and soil, can reduce the accumulation of pollutants in rice by adsorption, contributing to the safe production of rice in contaminated soil. In this study, we unveiled a new role of iron plaque, i.e., producing hydroxyl radicals (·OH) by activating root-secreted oxygen to degrade pollutants. The ·OH was produced on the iron plaque surface and then diffused to the interfacial layer between the surface and the rhizosphere environment. The iron plaque activated oxygen via a successive three-electron transfer to produce ·OH, involving superoxide and hydrogen peroxide as the intermediates. The structural Fe(II) in iron plaque played a dominant role in activating oxygen rather than the adsorbed Fe(II), since the structural Fe(II) was thermodynamically more favorable for oxygen activation. The oxygen vacancies accompanied by the structural Fe(II) played an important role in oxygen activation to produce ·OH. The interfacial ·OH selectively degraded rhizosphere pollutants that could be adsorbed onto the iron plaque and was less affected by the rhizosphere environments than the free ·OH. This study uncovered the oxidative role of iron plaque mediated by its produced ·OH, reshaping our understanding of the role of iron plaque as a barrier for rice.

Plutonium mobilization from contaminated estuarine sediments, Esk Estuary (UK).

Since 1952, liquid radioactive effluent containing238-242Pu, 241Am, 237Np, 137Cs, and 99Tc has been released with authorization from the Sellafield nuclear complex (UK) into the Irish Sea. This represents the largest source of plutonium (Pu) discharged in all western Europe, with 276 kg having been released. In the Eastern Irish Sea, the majority of the transuranic activity has settled into an area of sediments (Mudpatch) located off the Cumbrian coast. Radionuclides from the Mudpatch have been re-dispersed via particulate transport in fine-grained estuarine and intertidal sediments to the North-East Irish Sea, including the intertidal saltmarsh located at the mouth of the Esk Estuary. Saltmarshes are highly dynamic systems which are vulnerable to external agents (sea level change, erosion, sediment supply, and freshwater inputs), and their stability remains uncertain under current sea level rise projections and possible increases in storm activity. In this work, we examined factors affecting Pu mobility in contaminated sediments collected from the Esk Estuary by conducting leaching experiments under both anoxic and oxic conditions. Leaching experiments were conducted over a 9-month period and were periodically sampled to determine solution phase Pu via multicollector-inductively coupled plasma-mass spectrometry (MC-ICP-MS), and to measure redox indicators (Eh, pH and extractable Fe(II)). Microbial community composition was also characterized in the sediments, and at the beginning and end of the anoxic/oxic experiments. Results show that: 1) Pu leaching is about three times greater in solutions leached under anoxic conditions compared to oxic conditions, 2) the sediment slurry microbial communities shift as conditions change from anoxic to oxic, 3) Pu leaching is enhanced in the shallow sediments (0-10 cm depth), and 4) the magnitude of Pu leached from sediments is not correlated with total Pu, indicating that the biogeochemistry of sediment-associated Pu is spatially heterogeneous. These findings provide constraints on the stability of redox sensitive Pu in biogeochemically dynamic/transient environments on a timescale of months and suggests that anoxic conditions can enhance Pu mobility in estuarine systems.

Effect of Ferrous Ion on Heat-Induced Aroma Deterioration of Green Tea Infusion.

Aroma deterioration is one of the biggest problems in processing tea beverages. The aroma of tea infusion deteriorates fast during heat sterilization and the presence of ferrous ion (Fe2+) aggravates it. The underlying mechanism remains unveiled. In this study, Fe2+ was verified to deteriorate the aroma quality of green tea infusion with heat treatment. Catechins were necessary for Fe2+-mediated aroma deterioration. By enhancing the degradation of catechins, Fe2+ dramatically increased the production of hydrogen peroxide (H2O2). Fe2+ and H2O2 together exacerbated the aroma of green tea infusion with heat treatment. GC-MS analysis revealed that the presence of Fe2+ enhanced the loss of green/grassy volatiles and promoted the formation of new volatiles with diversified aroma characteristics, resulting in a dull scent of green tea infusion. Our results revealed how Fe2+ induced aroma deterioration of green tea infusion with heat treatment and could help guide tea producers in attenuating the aroma deterioration of tea infusion during processing.

In situ synthesis of fluorescent polydopamine polymer dots based on Fenton reaction for a multi-sensing platform.

The development of fluorescent nanosensors has attracted extensive research interest owing to their superior optoelectronic properties. However, current fluorescent nanoprobes generally involve complicated synthesis processes, background signal disturbance, and limited analyte detection. In this work, a facile and time-saving synthetic strategy for the preparation of green emitting polydopamine polymer dots (PDA-PDs) from dopamine via Fenton reaction at room temperature was proposed for the first time. The obtained PDA-PDs possessed excellent luminescence properties, with a long-wavelength emission of 522 nm, a large Stokes shift of 142 nm, and good photostability against ionic strength and UV irradiation. The formation mechanism of fluorescent PDA-PDs is as follows: in the presence of Fe2+ and H2O2, dopamine could rapidly undergo oxidation to its quinone derivatives and further polymerize to synthesize the fluorescent PDA-PDs with the acceleration of hydroxyl radicals produced from the Fenton reaction. Thus, a versatile turn-on fluorescence sensing method was developed for the detection of multi-analytes (including Fe2+, dopamine, H2O2, and glucose) based on monitoring the intrinsic fluorescence signal of the in situ formation of PDA-PDs. This sensing method could be efficiently applied for the detection of Fe2+, dopamine, and glucose in real human serum samples. Moreover, a three-input AND molecular logic gate based on this sensing platform was designed with the fluorescence signal of PDA-PDs as the gate. Finally, the proposed PDA-PDs could have immense broad prospects in nanomaterials and biosensors.

Recognition, mechanistic investigation and applications for the detection of biorelevant Cu2+/Fe2+/Fe3+ ions by ruthenium(II)-polypyridyl based fluorescent sensors.

The present article focuses on fluorescent probes based on Ru(ii)-polypyridyl fragments connected to different chelates, their significant roles in coordination chemistry and their applications in the selective recognition of biorelevant Cu2+ and Fe2+/Fe3+ ions. A critical analysis of the detection of metal ions by both "turn-on" and "turn-off" emission, properties, mechanism and applications of these sensors is presented. Emphasis has also been laid on the efficiency, selectivity and specificity of these sensors towards biologically important Cu2+ and Fe2+/Fe3+ ions.

Microcystis aeruginosa inactivation and microcystin-LR degradation by the photo-Fenton process at the initial near-neutral pH.

Of all cyanobacteria, Microcystis aeruginosa is the most commonly found species in bloom episodes all over the world. This species is known to produce cyanopeptides with hepatotoxic effects, namely microcystins (MCs). In this regard, Advanced Oxidation Processes (AOPs) have been widely studied for cyanotoxin degradation, but very few studies focused on cyanobacteria inactivation combined with toxin removal. To our knowledge, this is the first report of the photo-Fenton process application focusing on M. aeruginosa inactivation and microcystin-LR (MC-LR) degradation. This research work aimed to evaluate the photo-Fenton process under three different conditions with regard to Fe2+/H2O2 ratios (0.6/10, 5/50, and 20/100 mg L-1) at the initial near-neutral pH. Process efficiency was measured by immediate cell density reduction, growth inhibition, effect on MC-LR concentrations, and scanning electron microscopy (SEM) to analyze any alterations in cell morphology. Growth inhibition test (GIT) results pointed to cell inactivation under all conditions tested, and MC-LR concentrations were reduced below WHO's maximum limit at medium and higher concentrations of reagents. The possible mechanisms of cell inactivation by oxidative species are discussed.

Identification of Cell Status via Simultaneous Multitarget Imaging Using Programmable Scanning Electrochemical Microscopy.

A programmable multitarget-response electrochemical imaging technique was presented using scanning electrochemical microscopy (SECM) combined with a self-designed waveform. The potential waveform applied to the tip decreased the charging current caused by the potential switch, enhancing the signal-to-noise ratio. This programmable SECM (P-SECM) method was used to scan a metal strip for verifying its feasibility in feedback mode. Since it could achieve simultaneous multitarget imaging during one single imaging process, PC12 cells status was imaged and identified through three different molecules (FcMeOH, Ru(NH3)63+, and oxygen). The FcMeOH image eliminated the error from cell height, and the Ru(NH3)63+ image verified the change of membrane permeability. Moreover, the oxygen image demonstrated the bioactivity of the cell via its intensity of respiration. Combining information from these three molecules, the cell status could be determined accurately and also the error caused by time consumption with multiple scans in traditional SECM was eliminated.

Application of capillary electrophoresis technique for the enantioseparation of bioactive ferrocene-based compounds versus DFT calculated data.

Herein, a series of bioactive ferrocene-modified N-heterocycles with alkyl linkers was prepared in good to quantitative yields starting from easy accessible ferrocene alcohols and heterocycles under acidic or neutral (for imidazole) conditions in racemic forms. The analytical resolution of a number of bioactive racemic ferrocene azoles 1-6 (where azole = imidazole, pyrazole, and benzotriazole derivatives) into enantiomers was first carried out by CE using sulfobuthylether-ß-CD (captisol) as a chiral selector. The analytical approaches to highly enantiomeric-enriched ferrocene derivatives are based on the formation of their inclusion complexes. The best chiral separation was achieved using zone CE in a quartz capillary. The ACE was used to evaluate the stability constants of captisol complexes with enantiomeric forms of two ferrocene derivatives 1, FcCHMe-imidazole, and 6, FcCHMe-benzotriazole. The optimal conditions for the resolution of the studied (R, S)-ferrocene compounds 1, 2, and 6 were predicted on the basis of the performed quantum chemical calculations and then implemented by the electrophoretic method. A high correlation between density functional theory calculation results and experimental electrophoresis data were obtained. Successful enantioseparation of racemic mixtures is of great importance for the characterization and further applications of drug candidates in enantiopure forms and in the development of clinical treatment. The advantages of the CE procedure make it possible to have important practical value and significance for determining the purity and enantiomeric excess of other ferrocene-containing compounds.

Candidatus Anthektikosiphon siderophilum OHK22, a New Member of the Chloroflexi Family Herpetosiphonaceae from Oku-okuhachikurou Onsen.

We report the draft metagenome-assembled genome of a member of the Chloroflexi family Herpetosiphonaceae from microbial biofilms developed in a circumneutral, iron-rich hot spring in Japan. This taxon represents a novel genus and species-here proposed as Candidatus Anthektikosiphon siderophilum-that expands the known taxonomic and genetic diversity of the Herpetosiphonaceae and helps orient the evolutionary history of key traits like photosynthesis and aerobic respiration in the Chloroflexi.

Highly chemoselective turn-on fluorescent probe for ferrous (Fe2+) ion detection in cosmetics and live cells.

In modern society, the use of cosmetics has increased extensively; unfortunately, so-called several toxic metal salts are present as the colorant or filler in cosmetics. The ferrous ion (Fe2+) is one of the metal ions used in cosmetics as a colorant. Ferrous ion (Fe2+) is a vital component in live cells. Considering the adverse effect of high doses of ferrous ions in cosmetics and live cells, we developed a turn-on fluorescent probe PFe(II) for quantitative estimation of ferrous ion (Fe2+) in cosmetics and monitoring of labile ferrous (Fe2+) ion in live cells. The fluorescent probe PFe(II) showed a visual color change from colorless to orange in the presence of ferrous ion (Fe2+) in the cosmetics. We observed that UV-absorption increased at 390 nm upon incubation with ferrous ion (Fe2+). The probe PFe(II) has provided quantitative information on ferrous ion (Fe2+) in various cosmetics, kajol, lip balm, face foundation, mascara, eyeliner, lipliner, face makeup, sindoor, lipstick, nail polish in ppm level through the fluorescence signaling at 460 nm.The probe PFe(II) provided information on labile Fe2+ ion pool via a fluorescence imaging. It is a new addition to the diagnostic inventory for detecting ferrous ion in live cells and cosmetics.

A sensitive "Switch-on" phosphorescent probe for ferrous iron quantification in drug and In vitro imaging of living cells.

Iron plays an important role in various physiological processes. However, the detailed biological functions of iron have not been sufficiently explored because of a lack of effective methods to monitoring iron, especially the labile ferrous ion (Fe2+). In the current study, a novel turn-on phosphorescent probe for Fe2+ quantification and visualization has been proposed based on the hybrid nanocomposite of manganese dioxide and gemini iridium complex (MnO2-GM-Ir). The surfactant-like GM-Ir with positive charges was beneficial to combine with the negatively charged manganese dioxide (MnO2) nanosheets, and thus endowing the MnO2-GM-Ir nanocomposite excellent dispersion ability in the water as well as efficiently avoiding the interference to the detection caused by the agglomeration of nanocomposite. Phosphorescence of GM-Ir was effectively quenched by MnO2 nanosheets through fluorescence resonance energy transfer (FRET) and the inner filter effect (IFE), while the phosphorescence could be significantly recovered in the presence of Fe2+via a selective Fe2+-mediated reduction of MnO2 nanosheets, indicating a highly-specific selectivity towards Fe2+ with a low detection limit (80 nM). The drug test assay and in vitro imaging studies further proved that the MnO2-GM-Ir nanocomposite could be employed as a promising probe for the quantitative detection of exogenous Fe2+ in drug and in vitro imaging of living cells.

Almond skin extract mediated optimally biosynthesized antibacterial silver nanoparticles enable selective and sensitive colorimetric detection of Fe+2 ions.

The safety of drinking water is one of the most important public health issues as very high concentrations of metal like iron acts as a useful surrogate for other heavy metals. The present study demonstrates the use of almond skin extract (ASE) for simple and rapid synthesis of antibacterial silver nanoparticles (AgNPs) for the development of a highly selective and sensitive colorimetric method for the detection of Fe+2 in water samples. The optimization of various biogenic synthesis parameters showed ASE:AgNO3 ratio of 4:1,1 mM of AgNO3, pH 6 and incubation for 10 min at 70 °C were the optimum conditions. The test of antibacterial activity against widely used, representative Gram-negative and positive bacteria showed that AgNPs exhibit good activity against all five tested bacterial strains and comparatively were more effective against Gram-negative bacteria. Further, the test of AgNPs as a colorimetric probe for the detection of 20 different metal ions demonstrated that AgNPs were highly selective and sensitive towards the detection of Fe+2. The study of sensitivity of Fe+2 detection showed 245 ppm as the Limit of detection whereas, the intra-day recovery of Fe+2 in the range of 87.2-100.1 % with %RSD in the range of 4.2-6.5 % and inter-day recovery of Fe+2 in the range of 92.02-96.59 % with %RSD in the range of 2.9-3.8 % demonstrated the excellent precision and accuracy of the assay method. Thus, our AgNPs based selective and sensitive assay can be applied to the analysis of iron in drinking water samples.

A simple and effective dansyl acid based "turn-on" fluorescent probe for detecting labile ferrous iron in physiological saline and live cells.

Labile ferrous iron (Fe2+) plays important biochemical functions in many physiologically essential processes. It is very important to find an effective method to detect Fe2+. Herein, a simple and effective Fe2+ fluorescent probe (FeP1) has been constructed via a unique strategy of Fe2+-induced reducing reaction. As expected, FeP1 exhibited a 'turn-on' fluorescence response toward Fe2+ over various small analytes, with high selectivity and excellent sensitivity (DL = 18 nM) for the detection of Fe2+ in Tris-DMSO (4:1, pH = 7.4, v/v) solution. Moreover, the probe can act in different real samples, such as physiological saline and living cells.

Arsenic(III) biotransformation to tooeleite associated with the oxidation of Fe(II) via Acidithiobacillus ferrooxidans.

Tooeleite (Fe6(AsO3)4(SO4)(OH)4·4H2O), the only known ferric arsenite sulfate bearing mineral, has great potential for arsenic remediation due to its structure favoring incorporation of As(III). Based on the natural attenuation of removing As(III) directly by the formation of tooeleite via microorganisms, an iron-oxidizing bacterial strain Acidithiobacillus ferrooxidans ATCC 23270 (At.ferrooxidans) was selected to facilitate the formation of tooeleite. The optimized condition for the biogenic tooeleite was obtained at pH of 2.0, 30 °C and an initial arsenic of 500 mg/L. The process of biological mineralization is accompanied by the removal of 95.4% arsenic. What's more, biosynthetic tooeleite crystallization via a three-stage process was revealed using a combination of liquid and solid analyses (ICP-OES, XRD, XPS, FT-IR, SEM, STEM, particle distribution). The three stages included Fe2+ oxidation by At.ferrooxidans, Fe3+ hydrolysis and an initial Fe-As amorphous precursors formation, and finally transforming to tooeleite crystal. Moreover, RT-qPCR was used to reveal the relationship between functional gene expression of At.ferrooxidans and the mineral formation. The results showed the biogenic tooeleite exerts significant control on the geochemistry of arsenic contaminated systems.

Fluorometric assay of iron(II) lactate hydrate and ammonium ferric citrate in food and medicine based on poly(sodium-p-styrenesulfonate)-enhanced Ag nanoclusters.

Poly(sodium-p-styrenesulfonate)-enhanced and D-penicillamine stabilized Ag nanoclusters (PSS-DPA-AgNCs) were prepared using one-step ultraviolet irradiation combined with microwave heating method, and the effects of the AgNCs photo-luminescence performance based on different types of polyelectrolytes and energy suppliers were studied detailedly. The as-prepared AgNCs can be used as a viable fluorescent probe for monitoring indirectly iron(II) lactate hydrate (ILH) and ammonium ferric citrate (AFC), respectively. The fluorescence (FL) quenching of PSS-DPA-AgNCs by Fe3+ (it is obtained from oxidized ILH/ionized AFC) mainly derives from a dynamic quenching process. Excellent linear relationships exist between the FL quenching degree of the AgNCs and the concentrations of ILH/AFC in the range of 0.17-6.00/0.067-3.33 µmol·L-1, and corresponding limit of detection (at 3σ/slope) is 12.4/6.04 nmol·L-1. Moreover, the AgNCs probe was extended to the assays of ILH in tablets, solid beverage or ILH additive and AFC in two kinds of edible salts or syrup with satisfactory results compared with the standard 1, 10-phenanthroline method. In addition, the AgNCs probe reveals a good temperature sensing capability.

Supplementation with an Inorganic Iron Source Modulates the Metalloproteomic Profile of the Royal Jelly Produced by Apis mellifera L.

This study aimed to evaluate the quality of the royal jelly produced by Apis mellifera bees in the presence of different iron concentrations (ferrous sulfate heptahydrate-0, 25, 50, and 100 mg L-1). Two-dimensional electrophoresis was used for the fractionation of royal jelly proteins, and iron level was quantified using flame atomic absorption spectrometry technique. The proteins were identified using electrospray ionisation mass spectrometry. Analysis of variance followed by the Tukey test (P < 0.05) was utilised. Dietary supplementation with mineral Fe affected the protein content and number of proteins in the experimental period. Further, the diet containing the highest iron concentration showed a greater number of spots containing iron, as well as in the abdomen of the bees. The most protein containing Fe were classified as major royal jelly proteins. These results showed that Fe influenced the quality of royal jelly and can improve its nutritional value.

Common and rare iron, sulfur, and zinc minerals in technogenically contaminated hydromorphic soil from Southern Russia.

Soils formed after the desiccation of Lake Atamanskoe, which has served as a reservoir for liquid industrial waste from the city of Kamensk-Shakhtinsky during a long time, were studied. These soils differ from zonal soils by a strong contamination with zinc and sulfur. Preliminary studies showed that Fe compounds fix a significant part of zinc. This requires to study S, Zn, and Fe minerals. In this work, Mössbauer spectroscopy was used for the identification of iron compounds and scanning electron microscopy was used for the microanalysis of these and other minerals. To facilitate the identification of Fe minerals, brown iron ocher was removed from a contaminated soil sample and analyzed. From electron microscopy and Mössbauer spectroscopy data, ocher contained hydrogoethite with a high content of sorption water and schwertmannite (a rare mineral, probably found in Russia for the first time). The chemical composition of this schwertmannite better corresponds to the Cashion-Murad model than to the Bigham model. Particles of partially oxidized magnetite and wustite enriched with zinc were revealed under electron microscope. Siderite with partial substitution of Fe2+ by Zn2+ was detected. Thus, contaminated hydromorphic soil contains both common minerals (illite, goethite, hematite, gypsum) and rare minerals (schwertmannite, Zn siderite, partially oxidized magnetite and wustite enriched with zinc).

A new colorimetric DET technique for determining mm-resolution sulfide porewater distributions and allowing improved interpretation of iron(II) co-distributions.

Measurement of sulfide in pore waters is critical for understanding biogeochemical processes, especially within coastal sediments. Here we report the development of a new colorimetric DET (diffusive equilibration in thin films) technique for determining mm-resolution, two-dimensional sulfide distributions in sediment pore waters. This colorimetric sulfide DET method was based on the standard spectrophotometric methylene blue assay, but modified to allow quantitation of sulfide by computer imaging densitometry. The method detection and effective upper measurement limits of the optimised technique were 3.7 and 1000 µmol L-1, respectively. The optimised sulfide DET method was combined with the colorimetric iron(II) DET method to obtain co-distributions in coastal seagrass (Zostera muelleri) colonised sediment under light and dark conditions. In the dark, seagrass sediments were more reduced than in the light, with large areas being dominated by high porewater sulfide concentrations. These co-distributions were compared with those obtained using the previously described DET-DGT (diffusive gradients in thin films) method for measuring iron(II) and sulfide co-distributions. There was less overlap of iron(II) and sulfide distributions using the sulfide DET as the two DET methods are influenced most by the later hours of deployment, whereas the sulfide-DGT measurement integrates concentrations over the whole deployment period. Overlap was most apparent in very dynamic sediment zones, such as burrow wall sediments.

Disentangling the effects of habitat biogeochemistry, food web structure, and diet composition on mercury bioaccumulation in a wetland bird.

Methylmercury (MeHg) is a globally pervasive contaminant with known toxicity to humans and wildlife. Several sources of variation can lead to spatial differences in MeHg bioaccumulation within a species including: biogeochemical processes that influence MeHg production and availability within an organism's home range; trophic positions of consumers and MeHg biomagnification efficiency in food webs; and individual prey preferences that influence diet composition. To better understand spatial variation in MeHg bioaccumulation within a species, we evaluated the effects of habitat biogeochemistry, food web structure, and diet composition in the wetland-obligate California black rail (Laterallus jamaicensis coturniculus) at three wetlands along the Petaluma River in northern San Francisco Bay, California, USA. The concentration of MeHg in sediments differed significantly among wetlands. We identified three sediment and porewater measurements that contributed significantly to a discriminant function explaining differences in habitat biogeochemistry among wetlands: the porewater concentration of ferrous iron, the percent organic matter, and the sediment MeHg concentration. Food web structure and biomagnification efficiency were similar among wetlands, with trophic magnification factors for MeHg ranging from 1.84 to 2.59. In addition, regurgitation samples indicated that black rails were dietary generalists with similar diets among wetlands (percent similarity indices > 70%). Given the similarities in diet composition, food web structure, and MeHg biomagnification efficiency among wetlands, we concluded that variation in habitat biogeochemistry and associated sediment MeHg production was the primary driver of differences in MeHg concentrations among black rails from different wetlands.

Simultaneous removal of SO2 and NO by FeII(EDTA) solution: promotion of Mn powder and mechanism of reduction.

The effect of Mn powder addition on the simultaneous removal of SO2 and NO coupled with FeII(EDTA) absorption was investigated in this work. In the NO absorption system with FeII(EDTA), SO2 reduced FeII(EDTA)-NO to FeII(EDTA) with a reduction efficiency reaching 88.5% under the conditions of 4000 mg/m3 SO2, pH 8.0, 44 °C, and the flow rate of 1.2 L/min within 60 min. Introducing 0.1 M Mn powder with SO2 increased the FeII(EDTA)-NO reduction efficiency to 96.8% within 5 min. SO2 was also removed by reducing FeII(EDTA)-NO and converted into SO42- at a removal efficiency of 100%. After adding Mn powder, NO was removed through the following reaction: [Formula: see text]. Mn powder functioned as a reductant to regenerate the absorption of solution, and the coordinated NO in FeII(EDTA)-NO was reduced to NH4+. The resource utilization rate of N reached approximately 77.2%. The integrated technology is a potential solution for flue gas treatment in industrial sectors with coal-fired power plants and industrial boiler. Graphical abstract.