Abstract  Polyamines (PAs) are recognized as plant growth regulators that are involved in the stress management in various crops. In the current study, mitigative roles of spermidine (Spd) and putrescine (Put) were assessed in manganese (Mn) stressed Brassica juncea plants. Spd or Put (1.0 mM) were applied to the foliage of Brassica juncea at 35 days after sowing (DAS) grown in the presence of Mn (30 or 150 mg kg-1 soil). The higher level of Mn (150 mg kg-1) diminished photosynthetic attributes and growth, enhanced the production of reactive oxygen species (ROS) like hydrogen peroxide (H2O2) and superoxide anion ( [Formula: see text] ) content, affected stomatal movement and increased the Mn concentration in roots and shoots of the plant at 45 DAS, whereas it enhanced the activities of various antioxidant enzymes and proline content in the foliage of Brassica juncea plants. On the other hand, treatment of PAs (Spd or Put) to Mn stressed as well as non-stressed plants resulted in a remarkable improvement in the stomatal behaviour, photosynthetic attributes, growth and biochemical traits, decreased the production of ROS (H2O2 and [Formula: see text] ) and concentration of Mn in different parts of plant. It is concluded that out of the two polyamines (Spd or Put), Spd proved more efficient and enhanced growth, photosynthesis, and metabolic state of the plants which bestowed tolerance and helped the plants to cope efficiently under Mn stress.

Abstract  A granular Fe-Mn binary oxide (GFMO) was prepared for Cr(VI) removal and characterized by its Brunauer-Emmett-Teller surface area, scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy. Scanning electron microscopy images of the GFMO showed it had a rough surface and heterogeneous porous structure. The Brunauer-Emmett-Teller surface area was 57.64 m(2)/g. X-ray photoelectron spectra showed that manganese and iron existed mainly in the +IV and + III oxidation states, respectively. Adsorption of Cr(VI) by the GFMO was investigated. Kinetic data showed that the Cr(VI) adsorption onto the GFMO followed a pseudo-second-order model, indicating that the adsorption process was chemisorption. Equilibrium data were analyzed by both the Freundlich and Langmuir models, and the Langmuir isotherm model fitted better with the maximum adsorption capacity of 16.79 mg/g at 318 K. The Cr(VI) adsorption on GFMO was endothermic and nonspontaneous in nature. It was also strongly pH dependent, with higher Cr(VI) removal efficiency occurring under acidic conditions and a sharp decrease in adsorption as the pH increased. Coexisting anions competed with Cr(VI) for adsorption on the GFMO in the order silicate > sulfate > nitrate. Cr(VI) adsorption on the GFMO mainly occurred via anion exchange, surface complexation, and electrostatic attraction.

Abstract  The studies about the quality of groundwater resources are scarce in Mexico, and often they do not consider indicators of geogenic background and anthropogenic pollution. So, we examined the quality of groundwater from five wells of the Apan aquifer (Hidalgo, Mexico). Four of these wells were taken as reference samples, while the Santa Cruz well was considered as the study site because it is locally recognized as a problem due to the geogenic presence of manganese. In all the sites, variables related to mineralization processes were analyzed, and a quality index (MWQI, from mineralization-based water quality index) was calculated. In the study site samples, we also determined several indicators of geogenic background (arsenic, manganese, and other heavy metals) and anthropogenic pollution (as organic matter, nutrients, and several microbial indicators), from which another quality index (GAWQI, from geogenic background and anthropogenic pollution-based water quality index) was calculated. The MWQI values classified the groundwater from all the sites, even that from the Santa Cruz well, as excellent for drinking. When the GAWQI was computed for the Santa Cruz site, this groundwater was found unsuitable for drinking due to its extremely high manganese content. We conclude that the GAWQI could represent a valuable communication tool to inform the population and the authorities about the quality of the groundwater resources.

Abstract  Rivers are amongst the most threatened ecosystems on the planet. They are particularly susceptible to common forms of anthropogenic influences including sewage effluent runoff and flow modification. We hypothesized that the diversity of aquatic macroinvertebrate communities from three rivers (Nyl, Mogalakwena and Limpopo) within a semi-arid region (Limpopo, South Africa) will decline in response to shifts in water quality resulting from sewage effluent runoff. We assessed the diversity of aquatic macroinvertebrate communities from ten sites using univariate and multivariate analyses, and community responses were determined based upon anthropogenic disturbances. Our results show distinct spatial and temporal variation between the sampling sites and their associated macroinvertebrate communities. Spatial separation is attributable to increased concentrations of nitrogenous-based pollutants (total nitrogen and nitrites) and manganese, both of which are associated with sewage effluent runoff released by the Modimolle Waste Water Treatment Facility. Temperature is the principle driver of temporal variation amongst the macroinvertebrate communities, with winter (June 2016) communities being more diverse than summer (February 2017) communities. Macroinvertebrates remain important bioindicator organisms for riverine ecosystems, specifically within semi-arid regions. Our study highlights the need for more comprehensive diversity assessments of riverine macroinvertebrates, specifically from southern Africa, a region of the world that remains significantly underrepresented in the scientific literature of aquatic ecology. These results further increase our understanding of aquatic biodiversity within semi-arid regions and provides a baseline for future monitoring efforts and management in South Africa.

Abstract  Sustainable energies are usually intermittent and if solar energy is to become an energy source in future, energy-storage systems are necessary. A reasonable solution to store solar energy is artificial photosynthesis with energy stored in chemical bonds such as molecular hydrogen. Among different strategies, water splitting toward hydrogen and oxygen is very promising. This article provides a short review of the current status of manganese compounds as water-oxidizing catalysts in artificial photosynthesis. Generalization and inductive reasoning have been criticized, but at least many manganese complexes and salts convert to Mn oxide during water oxidation. Thus, we focused on Mn oxides and discuss the sophisticated design strategies for manganese oxides as water-oxidizing catalysts. Since an Mn oxide-cluster acts as the biological site for water oxidation, Mn oxides are counted as structural and functional models for the water-oxidizing cluster in photosystem II.

Abstract  Hydrothermal reactions of (benzylazanediyl)bis(methylene)-diphosphonic acid (H4L1) or (benzene-1,3,5-triyltris(methylene))triphosphonic acid (H6L2) with Fe(III)/Cu(II) nitrate and 4, 4'-bipy or 2, 2'-bipy result in five new phosphonates, namely, [FeHL1(H2O)](n) (1), {[Cu(2)(L)1(4, 4'-bipy)(0.5) (H2O)].0.25H(2)O}(n) (2), [Cu2H2L2(4, 4'-bipy)(H2O)2](n), (3), [CuH4L2(2, 2'-bipy)](n) (4) and [Cu-2(H4L2)2(2, 2'-bipy)(2)(H2O)(4)] (5), respectively. X-ray structural analysis indicates that 2 and 3 feature 3D framework structures with 3, 3, 3, 4 connected and 4, 5-connected topology; 1 and 4 display 1D chain structures, while 5 has a dimer structure. The di-or trisphosphonate ligands (H4L1 and H6L2) in the five complexes adopt different coordination modes and auxiliary ligands (4, 4'-bipy and 2, 2'-bipy) control the dimensionality of the final complexes. The superoxide dismutase (SOD) activities of 2-5 were assessed by modified nitrobluetetrazolium (NBT) assay. The IC50 values required to yield 50% inhibition of the reduction of NBT are 1.84, 2.02, 6.95 and 1.70 M for 2-5, respectively, demonstrating better SOD-like activity than most of the Cu-SOD mimic enzymes reported in literatures. Among them, 2 and 3 have good stability and reusability under the simulative physiological conditions. The dismutation of 4 and 5 toward superoxide anion radicals can be attributed to the synergistic effect of the decomposition products of 4 and 5 containing Cu(II) and [H4L2](2-)with or without 2, 2'-bipy or Cu(II) and 2, 2'bipy, which were identified by liquid mass spectrometry (LC/MS). The magnetic properties of complexes 1-4 were also investigated, indicating the presence of magnetic exchange between metal ions. The results show that 1 and 3 exhibit antiferromagnetic interactions, while 2 and 4 show ferromagnetic interactions between metal centres.

Abstract  Pure monoclinic lead chromate nanoparticles ware prepared via a new simple way with lead nitrate and chrome chloride as Pb and Cr sources. For the first time, nanostructured lead chromate was synthesized with utilizing triethylenepantamine as a new alkaline agent. The citric acid, succinic acid, maleic acid and benzene tri carboxylic acid as stabilization agent and capping agent in presence of ethylene glycol and propylene glycol as connecting agent were employed to prepare of the lead chromate. The as-prepared nanostructured PbCrO4 and PbCrO4/Ag was analyzed by UV-Vis diffuse reflectance spectroscopy (DRS), energy dispersive X-ray micro analysis (EDX), Fourier transform infrared (FT-IR) spectroscopy, transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). To examining the influence of various stabilization agents, connecting agent and alkaline agents on the morphology, grain size and photo catalytic performance of PbCrO4, different experiments were performed. The effects of various factors including kind of contamination, grain size ofPbCrO(4) nanostructures and pH on photocatalytic behavior of products was evaluated. Rhodamine B, methylene blue, methyl orange and murexide were used as pollutant model. It was observed that by using of PbCrO4/Ag nanostructure instead PbCrO4 nanoparticles the photocatalytic activity from 53 to 67 increased. Also by decreasing of pH from 7 to 5 destruction percentage of rhodamine B from 67 to 55 decreased.

Abstract  The isothermal imidation process of polymethacrylimide (PMI) prepared from acrylonitrile (AN), methacrylic acid (MAA) and alpha-methylstyrene (AMS) was investigated by "in-situ" Fourier transform infrared spectroscopy (FTIR) at different temperatures, ranged between 180 degrees C and 200 degrees C. The bending vibration absorption peak of hydrogen on the benzene ring in AMS at 700 cm(-1) was selected as the internal standard. The extent of the imidation was defined by the area ratio of the characteristic absorption peak of the nitrite osoups at 2243 cm(-1) to the internal standard. The plots of imidation extent versus time were analyzed by the Friedman method and the Avrami equation. The activation energy at the imidation extent between 0 and 0.2 was 60.4 kJ/mol to 65.1 kJ/mol, which was ascribed to the reaction of the forming imide ring structures. The increase of the activation energy from 65.1 kJ/mol to 92.3 kJ/mol at the imidation extent between 0.2 and 0.4 can be ascribed to the reaction of forming polyimine cyclic structures. At the imidation extent higher than 0.4, the activation energy decreased from 92.3 kJ/mol to 52.1 kJ/mol and the frequency factor (1nA) fell from 20.5 s(-1) to 12.6 s(-1). At this stage, the reaction was controlled by diffusion. Moreover. the Avrami curves were in good agreement with the experimental data of the imidation, except for the late stage. The decrease of the kinetic constant from 2.14x10 4 s(-1) to 0.92 s(-1) and activation energy from 54.05 kJ/mol to 20.39 kJ/mol further indicated that the imidation mechanism of the AN/MAA/AMS co-polymer system changed from kinetically controlled at the prophase to diffusion controlled at the anaphase.

Abstract  Perchlorate is frequently found as contaminant in a variety of food. Based on analytical data of perchlorate occurrence in food products from the Austrian market, this study calculated dietary perchlorate exposure of the Austrian population for the three age classes of adults, children and infants. Furthermore, a detailed risk assessment was conducted based on the tolerable daily intake (TDI) of 0.3 µg/kg body weight/day, established by the European Food Safety Authority in 2014. Calculations of a scenario of average food consumption did not indicate elevated health risks by dietary perchlorate uptake. Exposure estimates reached only 12%, 26% and 24% of the TDI for adults, children and infants, respectively. However, in a scenario of high consumption, the TDI was exceeded by all age classes with 132%, 161% and 156%. The major cause for this exceedance is the comparatively high perchlorate contamination of spinach, but also other leaf vegetables, legumes and pineapples, leading to elevated exposure of high consumers. Our calculations reveal that the current provisional intra-Union trade reference level for perchlorate in spinach of 0.2 mg/kg, advocated by the European Commission, is not sufficient to protect high consumers against possible health risks. In order to reduce health risks to a tolerable level for all consumers, lowering of the regulatory maximum perchlorate concentrations is indicated. Moreover, a generally diversified diet can also counteract excessive exposure to perchlorate as well as to other harmful food contaminants.

Abstract  The synthesis, characterization, and electrocatalytic properties of mesoporous carbon materials doped with nitrogen atoms and iron are reported and compared for the catalyzed reduction of oxygen gas at fuel cell cathodes. Mixtures of common and inexpensive organic precursors, melamine, and formaldehyde were pyrolyzed in the presence of transition-metal salts (e.g., nitrates) within a mesoporous silica template to yield mesoporous carbon materials with greater extents of graphitization than those of others prepared from small-molecule precursors. In particular, Fe,N-doped carbon materials possessed high surface areas (∼800 m2/g) and high electrical conductivities (∼19 S/cm), which make them attractive for electrocatalyst applications. The surface compositions of the mesoporous Fe,N-doped carbon materials were postsynthetically modified by acid washing and followed by high-temperature thermal treatments, which were shown by X-ray photoelectron spectroscopy to favor the formation of graphitic and pyridinic nitrogen moieties. Such surface-modified materials exhibited high electrocatalytic oxygen reduction activities under alkaline conditions, as established by their high onset and half-wave potentials (1.04 and 0.87 V, respectively vs reversible hydrogen electrode) and low Tafel slope (53 mV/decade). These values are superior to many similar transition-metal- and N-doped carbon materials and compare favorably with commercially available precious-metal catalysts, e.g., 20 wt % Pt supported on activated carbon. The analyses indicate that inexpensive mesoporous Fe,N-doped carbon materials are promising alternatives to precious metal-containing catalysts for electrochemical reduction of oxygen in polymer electrolyte fuel cells.

Abstract  Abstract: Three endosulfan-degrading bacterial strains, Pseudomonas sp. KT1, Pseudomonas sp. KT2 and Staphylococcus sp. DKT, were isolated and investigated for their degradation under anaerobic conditions. These bacteria effectively degraded endosulfans and some related compounds. All of the isolates utilized nitrate as an electron acceptor and nitrogen source. Endosulfans degradation performances by a mixed culture of Pseudomonas sp. KT2 and Staphylococcus sp. DKT changed from 25.9 ± 4.5 to 34.0 ± 5.5% and were higher than the degradation by the each individual strain. Moreover, Pseudomonas sp. KT2 was the first pure culture capable of degrading a persistent compound, endosulfan sulfate, under anaerobic conditions. The determination of degradation metabolites showed that endosulfan diol, endosulfan ether and endosulfan lactone were formed during endosulfan degradation by Pseudomonas sp. KT1 and KT2. Dehalogenase extracted from mixed culture cells also revealed effective degradation and dechlorination. The results in this study show that a mixed culture was valuable for biodegradation of endosulfans and some of their relatives under anaerobic conditions. © 2021, Pleiades Publishing, Inc.

Abstract  Two mononuclear complexes [Co(HL)L]NO3 (1) and [Cu(HL)(2)](NO3)(2) (2)were synthesized from the reaction of 2-acetylpyridine-4-hydroxy phenylacetyl acylhydrazone (HL) with copper/cobalt nitrate hydrate. The single-crystal XRD results revealed the central Co and Cu ions in two complexes are both six-coordinated showing a distorted octahedral geometry. Thermal stabilities of 1, 2 and HL were explored by thermogravimetry (TG) and the apparent activation energy (E-a) followed the order 2 > 1 > HL. The interactions of 1, 2, HL with calf thymus DNA (CT-DNA) and bovine serum albumin (BSA) were investigated through UV-Vis absorption spectroscopy, fluorescence spectroscopy, microcalorimetry and molecular docking approach. From UV-Vis absorption spectroscopy and fluorescence spectroscopy results, it is shown that 1, 2 and HL can bind with CT-DNA by intercalation mode and quench the fluorescence of BSA through static process. The binding constants Kth of three compounds toward CT-DNA/BSA followed the order: 1 > 2 > HL. Thermogenic curves of three compounds interacting with CT-DNA and BSA were measured by microcalorimetry. The calculated enthalpies, entropies and Gibbs' free energy change (Delta H > 0, Delta S > 0, Delta G < 0) indicated that all the interaction processes were endothermic and spontaneous. Molecular docking results further validated the intercalation binding mode of 1, 2 and HL with CT-DNA and the fluorescence quenching of tryptophan in BSA in presence of three compounds. It also demonstrated that hydroxyl, benzene ring, pyridine ring, and carbonyl group of 1, 2, HL are the most favorable binding site in DNA/BSA interaction. The antimicrobial activities of HL, 1 and 2 against Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtilis) were determined presenting that 1 and HL can inhibit the growth of S. aureus and B. subtilis, separately. Cellular uptakes of 1 and 2 into S. aureus and B. subtilis showed the amount of Co accumulation in S. aureus is bigger than that of Cu. (C) 2020 Elsevier Ltd. All rights reserved.

Abstract  The OH-initiated atmospheric degradation of tert-butylamine (tBA), (CH3)3CNH2, was investigated in a detailed quantum chemistry study and in laboratory experiments at the European Photoreactor (EUPHORE) in Spain. The reaction was found to mainly proceed via hydrogen abstraction from the amino group, which in the presence of nitrogen oxides (NO x), generates tert-butylnitramine, (CH3)3CNHNO2, and acetone as the main reaction products. Acetone is formed via the reaction of tert-butylnitrosamine, (CH3)3CNHNO, and/or its isomer tert-butylhydroxydiazene, (CH3)3CN═NOH, with OH radicals, which yield nitrous oxide (N2O) and the (CH3)3Ċ radical. The latter is converted to acetone and formaldehyde. Minor predicted and observed reaction products include formaldehyde, 2-methylpropene, acetamide and propan-2-imine. The reaction in the EUPHORE chamber was accompanied by strong particle formation which was induced by an acid-base reaction between photochemically formed nitric acid and the reagent amine. The tert-butylaminium nitrate salt was found to be of low volatility, with a vapor pressure of 5.1 × 10-6 Pa at 298 K. The rate of reaction between tert-butylamine and OH radicals was measured to be 8.4 (±1.7) × 10-12 cm3 molecule-1 s-1 at 305 ± 2 K and 1015 ± 1 hPa.

Abstract  In this work, a visible light-driven ternary heterojunction photocatalyst, CdS/Bi2WO6/ZnO, was synthesized using hydrothermal, ultrasonic dispersion, and deposition precipitation methods. The results show that photocatalysts with flower-like heterostructures were obtained, which could efficiently separate electron-hole pairs, and the photocatalytic activity was thereby significantly enhanced. Furthermore, CdS/Bi2WO6/ZnO and polyvinylidene fluoride (PVDF) were used to fabricate hybrid membranes via a phase-conversion method. The samples were characterized using SEM, TEM, EDX, XRD, DRS, XPS, PL, and N2 adsorption-desorption isotherms, and the transient photocurrent response. The photocatalytic activity of the hybrid membrane was evaluated, and 92.58% of the nitrite was converted into non-toxic substances within 4 h under simulated sunlight irradiation. This result indicated that the photocatalyst exhibited a good photocatalytic activity after immobilization. The possible mechanism was elucidated by studying the product during the photocatalytic degradation, and the effects of different pH values, electron scavengers, and hole scavengers on the photocatalytic performance were further investigated.

Abstract  Black carbon (BC) exerts a large impact on climate radiative forcing and public health, and such impacts depend strongly on chemical composition and mixing state. Here a single particle aerosol mass spectrometry (SPA-MS) along with an aerosol chemical speciation monitor was employed to characterize the composition and mixing state of BC-containing particles in summer and winter in Beijing. Approximately 2 million BC-containing particles were chemically analyzed, and the particles were classified into nine and eight different types in summer and winter, respectively, according to mass spectral signatures and composition. The BC-containing particles in summer were dominated by the type of nitrate-related BC (BC-N, 56.7%), while in winter the BC mixed with organic carbon (OC) and sulfate (BCOC-S), and OC and nitrate (BCOC-N) were two dominant types accounting for 44.9% and 16.6%, respectively. The number fractions of BC-N in summer, and BCOC-N and BC-SN in winter increased largely during periods with severe air pollution, suggesting the enhanced secondary formation on BC-containing particles. We also found that the primary emissions of the biomass burning and coal combustion can affect BC mixing state substaintially as indicated by the considerable fraction of BC mixed with levoglucosan and polycyclic aromatic hydrocarbons in winter. Bivariate polar plots and back trajectory analysis indicated that the sulfate-associated BC-containing particles were mostly from regional transport while the nitrate-related type was more from local production. The optical parameter of absorbing Ångström exponents (AAE) of BC was 1.2 and 1.5 in summer and winter, respectively, and the AAE dependence of BC mixing state was also different in the two seasons. While higher fractions of BC-N were observed during lower AAE periods in summer, the variations of dominant OC-related BC-containing particles in winter were fairly stable as a function of AAE.

Abstract  We investigated how foraging habits vary among three ecologically distinct wide-ranging seabirds. Using amino acid δ15N proxies for nutrient regime (δ15NPhe) and trophic position (Δδ15NGlu-Phe), we compared Newell's shearwater (Puffinus newelli) and Laysan albatross (Phoebastria immutabilis) foraging habits over the past 50-100 years, respectively, to published records for the Hawaiian petrel (Pterodroma sandwichensis). Standard ellipses constructed from the isotope proxies show that inter-population and interspecific foraging segregation have persisted for several decades. We found no evidence of a shift in nutrient regime at the base of the food web for the three species. However, our data identify a trophic decline during the past century for Newell's shearwater and Laysan albatross (probability ≥ 0.97), echoing a similar decline observed in the Hawaiian petrel. During this time, Newell's shearwaters and Hawaiian petrels have experienced population declines and Laysan albatross has experienced range extension and apparent population stability. Counting other recent studies, a pattern of trophic decline over the past century has now been identified in eight species of pelagic seabirds that breed in the Hawaiian Islands. Because our study species forage broadly across the North Pacific Ocean and differ in morphological and behavioral traits and feeding methods, the identified trophic declines suggest a pervasive shift in food web architecture within the past century.

Abstract  High levels of HONO have frequently been observed in Chinese haze periods and underestimated by current models due to some unknown sources and formation mechanisms. Combining lab-chamber simulations and field measurements in Xi'an and Beijing, China, we found that NH3 can significantly promote HONO formation via the reduction-oxidation of SO2 with NO2 in the aqueous phase of hygroscopic particles (e.g., NaCl). Concentrations of HONO formed in the aerosol phase showed an exponential increase (R2 = 0.91) with NH3 levels under the chamber conditions and a linear growth with NH3 levels in the two Chinese cities. The uptake coefficient of NO2 on NaCl particles ranged from 2.0 × 10-5 to 1.7 × 10-4, 3-4 orders of magnitude larger than that on water droplets. Our results further showed that HONO formed from the aerosol phase accounted for 4-33% of the total in the chamber, indicating that aerosol-phase formation is an important source of HONO in China, especially in haze periods. Since NH3, SO2, and NO2 abundantly coexist in China, the positive effect of NH3 on HONO formation could enhance the atmospheric oxidizing capacity in the country, causing severe secondary aerosol pollution. Our work suggests that NH3 emission control is imperative for mitigating air pollution in China.

Abstract  Secondary particles account for a considerable proportion of fine particles (PM2.5) and reasonable reapportioning them to primary sources is critical for designing effective strategies for air quality improvement. This study developed a method which can reapportion secondary sources of PM2.5 solved by positive matrix factorization (PMF) to primary sources based on the isotopic signals of nitrate, ammonium and sulfate. Actual PM2.5 data in Beijing were used as a case study to assess the feasibility and capacity of this method. In the case, 20 chemical components were used to apportion PM2.5 sources and source contributions of nitrate were applied to reapportion secondary source to primary sources. The model performance was also estimated by radiocarbon measurement (14C) of organic (OC) and elemental (EC) carbons of eight samples. The PMF apportioned seven sources: the secondary source (36.1%), vehicle exhausts (18.7%), industrial sources (13.6%), biomass burning (11.4%), coal combustion (8.10%), construction dust (7.93%) and fuel oil combustion (4.24%). After the reapportionment of the secondary source, vehicle exhausts (28.7%) contributed the most to PM2.5, followed by biomass burning (25.1%) and industrial sources (18.9%). Fossil oil combustion and coal combustion increased to 8.00% and 11.4%, respectively, and construction dust contributed the least. The average gap between contributions of identified sources to OC and EC and the 14C measurements decreased 2.5 ± 1.2% after the reapportionment than 13.2 ± 10.8%, indicating the good performance of the developed method.