Abstract  Various products are observed in biological oxidation and reduction of molecules containing elements of variable valence. The variability is caused by the diversity of microorganisms and their metabolic enzymes, which may develop into novel processes in wastewater treatment. The study aimed to develop a novel denitrification process forming nitrite and ammonium in wastewaters containing thiocyanate. High-efficiency nitrite and ammonium production was observed due to autotrophic partial denitrification and ammonification as a result of nitrate and thiocyanate removal. Nitrite, ammonium and sulfate were observed as the ultimate products. The increased NO3--N/SCN--N ratio in the treated wastewater resulted in the decreased removal efficiency of nitrate, and the increased nitrate-to-nitrite transformation ratio and the ratio of NO2--N to NH4+-N. Thiocyanate sulfur was oxidized to sulfate via intermediate elementary sulfur providing electron to nitrate or nitrite. The Thiobacillus genus dominated in the sludge providing ammonium and nitrite as substrate for the potentially anammox process.

Abstract  The Haber-Bosch industrial process for synthesis of ammonia (NH3) from hydrogen and nitrogen produces the millions of tons of ammonia gas annually needed to produce nitrates for fertilizers required to feed the earth's growing populations. This process has been optimized extensively, but it still uses enormous amounts of energy (2% of the world's supply), making it essential to dramatically improve its efficiency. To provide guidelines to accelerate this improvement, we used quantum mechanics to predict reaction mechanisms and kinetics for NH3 synthesis on Fe(111)-the best Fe single crystal surface for NH3 synthesis. We predicted the free energies of all reaction barriers for all steps in the mechanism and built these results into a kinetic Monte Carlo model for predicting steady state catalytic rates to compare with single-crystal experiments at 673 K and 20 atm. We find excellent agreement with a predicted turnover frequency (TOF) of 17.7 s-1 per 2 × 2 site (5.3 × 10-9 mol/cm2/sec) compared to TOF = 10 s-1 per site from experiment.

Abstract  Elevated atmospheric input of nitrogen (N) is currently affecting plant biodiversity and ecosystem functioning. The growth and survival of numerous plant species is known to respond strongly to N fertilisation. Yet, few studies have assessed the effects of N deposition on seed quality and reproductive performance, which is an important life-history stage of plants. Here we address this knowledge gap by assessing the effects of atmospheric N deposition on seed quality of the ancient forest herb Anemone nemorosa using two complementary approaches. By taking advantage of the wide spatiotemporal variation in N deposition rates in pan-European temperate and boreal forests over 2 years, we detected positive effects of N deposition on the N concentration (percentage N per unit seed mass, increased from 2.8% to 4.1%) and N content (total N mass per seed more than doubled) of A. nemorosa seeds. In a complementary experiment, we applied ammonium nitrate to aboveground plant tissues and the soil surface to determine whether dissolved N sources in precipitation could be incorporated into seeds. Although the addition of N to leaves and the soil surface had no effect, a concentrated N solution applied to petals during anthesis resulted in increased seed mass, seed N concentration and N content. Our results demonstrate that N deposition on the petals enhances bioaccumulation of N in the seeds of A. nemorosa. Enhanced atmospheric inputs of N can thus not only affect growth and population dynamics via root or canopy uptake, but can also influence seed quality and reproduction via intake through the inflorescences.

Abstract  Leachate is a highly variable, heterogeneous and recalcitrant wastewater generated in landfills which may contain high concentrations of many organic and inorganic compounds, hampering the application of a single technique in its treatment. Therefore, this paper assessed leachate degradation through supercritical water oxidation (ScWO) as well as combined processes of ozonation and supercritical water oxidation (O3/ScWO and ScWO/O3), a yet innovative combination. Ozonation was carried out at different reaction times (30-120 min). ScWO was developed at 600 °C, 23 MPa, and spatial time (τ) from 29 to 52 s. A combination of ozonation (30 min) and supercritical water oxidation process (O3-30'/ScWO) was the most efficient technique for the degradation of the leachate assessed. These conditions enabled to remove high values of apparent and true color (92% and 97%, respectively), biochemical oxygen demand (BOD5,20) (95%), chemical oxygen demand (COD) (92%), total organic carbon (TOC) (79%), nitrite (78%), nitrate (84%), total (96%), dissolved (96%) and suspended (94%) solids. In addition, the combined process presented significant decrease in electric conductivity (EC) (68%) and less leachate turbidity removal (43%). Except for ammonia and nitrite, all parameters of the leachate treated by O3-30'/ScWO met the specifications of Brazilian legislation (CONAMA Resolutions No. 357/2005 and No. 430/2011) for the disposal of wastewater in water bodies. Besides, both processes are considered to be clean technologies. This shows the great possibility of applying the O3/ScWO combination to landfills leachates.

Abstract  Limited evidence exists concerning the impact of particulate pollution on acute respiratory distress syndrome (ARDS). We examined the effects of particulate pollution on emergency ambulance dispatches (EAD) for ARDS in Guangzhou, China. Daily air pollution concentrations for PM10, PM2.5, and PM1, as well as PM2.5 chemical compositions, were available from a central air monitoring station. The association between incident ARDS and air pollution on the concurrent and previous 5 days was estimated by an over-dispersed Poisson generalized additive model controlling for meteorological factors, temporal trends, public holidays and day of the week. We identified a total of 17,002 EADs for ARDS during the study period. There were significant associations between concentrations of PM10, PM2.5, PM1, and ARDS; corresponding excess risk (ER) for an interquartile range IQR increase in 1-day lagged concentration was 5.45% [95% confidence interval (CI): 1.70%, 9.33%] for PM10 (45.4 μg/m3), 4.71% (95% CI: 1.09%, 8.46%) for PM2.5 (31.5 μg/m3), and 4.45% (95% CI: 0.81%, 8.23%) for PM1 (28.8 μg/m3), respectively. For PM2.5 chemical compositions, we found that OC, EC, sulfate and ammonium were significantly associated with ARDS. The observed effects remained even after adjusting for potentially confounding factors. This study suggests that PM10, PM2.5, and PM1, as well as chemical constituents from combustion and secondary aerosols might be important triggers of ARDS in Guangzhou.

Abstract  Supercritical water oxidation (SCWO) of 41 N-containing compounds was examined under a stable temperature and pressure of 450 °C and 24 MPa, respectively, reaction time ranged from 0.5 to 6 min with 500% excess oxygen, resulted in the degradation rate constants of total organic carbon (kTOC) and total nitrogen (kTN) were 0.162-3.693 and 0.065-0.416 min-1, respectively. The N-containing products were primary N2, ammonium and nitrate. As for amino-group compounds, the main product was ammonia, while for nitro-group compounds, nitrate was the predominant. In terms of diazo and N-heterocyclic group compounds, the main products generally were nitrate and ammonium, respectively. Interestingly, 2-, 3- and 4-nitroaniline, containing both of nitro and amino group, would directly decompose into N2. The reaction pathways of acid orange 74 was proposed based on Fukui indices, which generally included denitrification, ring-open and mineralization. Density functional theory (DFT) method was applied to calculate the quantum properties of the 41 N-containing compounds in order to further examine the relationship between TN removal and molecular structural characteristics. The correlation result showed that among all the 17 molecular characteristics, F(+)n, F(-)n, F(0)n, and EHOMO achieved high correlation coefficients.

Abstract  Ocean acidification may alter the cycling of nitrogen in coastal sediment and so the sediment-seawater nitrogen flux, an important driver of pelagic productivity. To investigate how this perturbation affects the fluxes of NOX- (nitrite/nitrate), NH4+ and O2, we incubated estuarine sand and subtidal silt in recirculating seawater with a CO2-adjusted pH of 8.1 and 7.9. During a 41-day incubation, the seawater kept at pH 8.1 lost 97% of its NOX- content but the seawater kept at pH 7.9 lost only 18%. Excess CO2 increased benthic photosynthesis. In the silt, this was accompanied by a reversal of the initial NOX- efflux into influx. The estuarine sand sustained its initial NOX- influx but, by the end of the incubation, released more NH4+ at pH 7.9 than at pH 8.1. We hypothesise that these effects share a common cause; excess CO2 increased the growth of benthic microalgae and so nutrient competition with ammonia oxidising bacteria (AOB). In the silt, diatoms likely outcompeted AOB for NH4+ and photosynthesis increased the dark/light fluctuations in the pore water oxygenation inhibiting nitrification and coupled nitrification/denitrification. If this is correct, then excess CO2 may lead to retention of inorganic nitrogen adding to the pressures of increasing coastal eutrophication.

Abstract  The molybdopterin enzyme family catalyzes a variety of substrates and plays a critical role in the cycling of carbon, nitrogen, arsenic, and selenium. The dimethyl sulfoxide reductase (DMSOR) subfamily is the most diverse family of molybdopterin enzymes and the members of this family catalyze a myriad of reactions that are important in microbial life processes. Enzymes in the DMSOR family can transform multiple substrates; however, quantitative information about the substrate preference is sparse, and, more importantly, the reasons for the substrate selectivity are not clear. Molybdenum coordination has long been proposed to impact the catalytic activity of the enzyme. Specifically, the molybdenum-coordinating residue may tune substrate preference. As such, molybdopterin enzyme periplasmic nitrate reductase (Nap) is utilized as a vehicle to understand the substrate preference and delineate the kinetic underpinning of the differences imposed by exchanging the molybdenum ligands. To this end, NapA from Campylobacter jejuni has been heterologously overexpressed, and a series of variants, where the molybdenum coordinating cysteine has been replaced with another amino acid, has been produced. The kinetic properties of these variants are discussed and compared with those of the native enzyme, providing quantitative information to understand the function of the molybdenum-coordinating residue.

Abstract  Microbial arsenite (As(III)) oxidation associated with nitrate (NO3-) reduction might be an important process in diminishing arsenic bioavailability and toxicity to rice when paddy soils are contaminated by arsenic. In a noncontaminated soil, however, the responses of bacterial communities and functional genes to As(III) under nitrate-reducing conditions are poorly understood. In this study, anaerobic paddy soil microcosms were established with As(III) and/or NO3- to investigate how the bacterial communities and their functional genes were stimulated during As(III) oxidation and nitrate reduction. Microbial oxidation of As(III) to As(V) was substantially accelerated by nitrate addition, while nitrate reduction was not affected by As(III) addition. Metagenomic analysis revealed that nitrate-reducing bacteria were principally affiliated with Pseudogulbenkiania, with narG, nirS, and norBC genes. Putative As(III)-oxidizing bacteria were dominated by an Azoarcus sp. with As(III) oxidase genes aioA and aioB detected in its draft genome, which also had complete sets of denitrification genes (mainly, napA, nirK, and nosZ). Quantitive PCR analysis confirmed that the abundance of Azoarcus spp., aioA, and nosZ genes was enhanced by As(III) addition. These findings suggest the importance of Azoarcus- and Pseudogulbenkiania-related spp., both of which showed various physio-ecological characteristics for arsenic and nitrogen biogeochemistry, in coupling As(III) oxidation and nitrate reduction in flooded paddy soil.

Abstract  Fabrication of composites by developing simple techniques can be an effective way to modify some properties of individual materials. The present study relates to facile synthesis of sodium nitrate (NaNO3) and potassium nitrate (KNO3) contaminated polyaniline (PANI) and poly (ethylene oxide) (PEO) composites without using any additives, plasticizers, or fibers. The physic-chemical and rheological properties of synthesized composites were analyzed. The composites showed enhancement in both storage and loss modules in comparison with the polymer matrices. The dynamic viscosity of the synthesized materials has inverse relation with that of temperature and shear stress. Rheological analysis reveals a continuous drop off in viscosity by increasing shear stress. The flow behavior was affected little by temperature. However, the overall results showed a shear thinning effect suggesting that polymer composites show non-Newtonian behavior. The addition of NaNO3 and KNO3 had a profound effect on shear viscosity of the materials, although the overall shear thinning behavior prevails. The PANI-PEO composite follows, as the first approximation models, both Bingham and modified Bingham models, while the salt contaminated system follows only the Bingham model. Both show shear stress values. The greater values of storage (G') and loss (G″) modulus of composites than PANI-PEO blend suggests excellent elasticity, better stiffness, and good mechanical strength of the composites. Furthermore, the composites were more thermally stable than pure polymers.

Abstract  In this work the role of phase transition of PEO from crystalline to amorphous phases on DC conductivity enhancement in chitosan-based polymer electrolyte was discussed. Silver ion-conducting polymer electrolytes based on chitosan (CS) incorporated with silver nitrate (AgNt) is prepared via solution cast technique. Various amounts of polyethylene oxide (PEO) are added to the CS:AgNt system to prepare blend polymer electrolytes. Ultraviolet-visible (UV-vis) spectrophotometry is used to confirm that the blended samples containing AgNt salt exhibit a broad absorption peak. From optical micrograph images it is apparent that small white specs appear on the surface of the samples. The SEM results clearly show the aggregated silver nanoparticles. The enlargement of the crystalline area was observed from the morphological emergence and impedance plots. The phase separation in SEM images was observed at high PEO concentration. The XRD consequences support the morphological manifestation. In this study a new approach is offered to explore the microstructures existing in the blend electrolytes. The width of the semicircle linked to crystalline phase in impedance spectra was found to be increased with the increase of PEO concentration. A slow increase of DC conductivity was observed at low temperatures while above 333 K an immediate change in DC conductivity was obtained. The rapid rise of DC conductivity at high temperatures is correlated with the DSC results and impedance studies at high temperatures.

Abstract  Living mulch gives many benefits to agro-ecosystems such as erosion control, nitrogen fixation and nutrient recycling, increasing of organic matter, weed and pest control, and increasing of soil organism. The experiment, carried out in Puglia, Southern Italy on transplanted broccoli raab (cv. Grossa fasanese), evaluated four soil management systems (SMSs): Trifolium subterraneum and T. repens used as living mulch, undisturbed weedy, and conventional tillage. For each SMS, four rates of nitrogen and phosphorous (NP0, NP1, NP2, and NP3) were supplied, using an organic fertilizer. The following data were collected: weed infestation, leaf chlorophyll in the plants (as SPAD units), weight, diameter, and colour of the inflorescences, anion and Mg, Fe, Na, K, Ca content. Fertilization showed prominent effects on most of parameters evaluated. The Sufficient Index of broccoli raab plants was higher in fertilized plots. With the increasing of fertilization rates, weight of primary inflorescences and the marketable yield linearly increased, confirming the great influence of nitrogen fertilization on the yield of Brassicaceae vegetables and highlighting the importance of combining living mulch and fertilization. By increasing fertilization rates, some elements, such as Mg and Fe, increased, whereas a decrease of Na, K, and Ca was observed. The nitrate content in the inflorescences was different only between the fertilized and unfertilized plots, although it was very low. In NP2 and NP3 a greener colour was found. Living mulch did not clearly affect quality and yield of broccoli raab but was effective in weed control. Results show the positive effects of living mulch and organic fertilization in the sustainable production of broccoli raab.

Abstract  Oxidative stress plays a key role for the development of cardiovascular, metabolic, and neurodegenerative disease. This concept has been proven by using the approach of genetic deletion of reactive oxygen and nitrogen species (RONS) producing, pro-oxidant enzymes as well as by the overexpression of RONS detoxifying, antioxidant enzymes leading to an amelioration of the severity of diseases. Vice versa, the development and progression of cardiovascular diseases is aggravated by overexpression of RONS producing enzymes as well as deletion of RONS detoxifying enzymes. We have previously identified cross talk mechanisms between different sources of RONS, which can amplify the oxidative stress-mediated damage. Here, the pathways and potential mechanisms leading to this cross talk are analyzed in detail and highlighted by selected examples from the current literature and own data including hypoxia, angiotensin II (AT-II)-induced hypertension, nitrate tolerance, aging, and others. The general concept of redox-based activation of RONS sources via "kindling radicals" and enzyme-specific "redox switches" as well as the interaction with redox-sensitive inflammatory pathways are discussed. Here, we present evidence for the existence of such cross talk mechanisms in the setting of diabetes and critically assess their contribution to the severity of diabetic complications.

Abstract  All studies on oxygen-evolution reaction by Mn oxides in the presence of cerium(IV) ammonium nitrate (CAN) have been so far carried out by synthesizing Mn oxides in the first step. And then, followed by the investigation of the Mn oxides in the presence of oxidants for oxygen-evolution reaction (OER). This paper presents a case study of a new and promising strategy for in situ catalyst synthesis by the adding MnII to either CAN or KMnO4 /CAN solution, resulting in the formation of Mn-based catalysts for OER. The catalysts were characterized by scanning electron microscopy, energy-dispersive spectroscopy, transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray absorption spectroscopy, and X-ray photoelectron spectroscopy. Both compounds contained nano-sized particles that catalyzed OER in the presence of CAN. The turnover frequencies for both catalysts were 0.02 (mmol O2 /molMn ⋅s).

Abstract  Nitrogen is an important nutrient for plant growth and tuber quality of potato. Since potato crop requires high dose of N, improving nitrogen use efficiency (NUE) of plant is an inevitable approach to minimize N fertilization. The aim of this study was to identify and characterize microRNAs (miRNAs) by small RNA sequencing in potato plants grown in aeroponic under two contrasting N (high and low) regimes. A total of 119 conserved miRNAs belonging to 41 miRNAs families, and 1002 putative novel miRNAs were identified. From total, 52 and 54 conserved miRNAs, and 404 and 628 putative novel miRNAs were differentially expressed in roots and shoots, respectively under low N stress. Of total 34,135 predicted targets, the gene ontology (GO) analysis indicated that maximum targets belong to biological process followed by molecular function and cellular component. Eexpression levels of the selected miRNAs and targets were validated by real time-quantitative polymerase chain reaction (RT-qPCR) analysis. Two predicted targets of potential miRNAs (miR397 and miR398) were validated by 5' RLM-RACE (RNA ligase mediated rapid amplification of cDNA ends). In general, predicted targets are associated with stress-related, kinase, transporters and transcription factors such as universal stress protein, heat shock protein, salttolerance protein, calmodulin binding protein, serine-threonine protein kinsae, Cdk10/11cyclin dependent kinase, amino acid transporter, nitrate transporter, sugar transporter, transcription factor, F-box family protein, and zinc finger protein etc. Our study highlights that miR397 and miR398 play crucial role in potato during low N stress management. Moreover, study provides insights to modulate miRNAs and their predicted targets to develop N-use efficient potato using transgenic/genome-editing tools in future.

Abstract  Microfluidic paper-based devices (μPADs) and wearable devices have been highly studied to be used as diagnostic tools due to their advantages such as simplicity and ability to provide instrument-free fast results. Diseases such as periodontitis and diabetes mellitus can potentially be detected through these devices by the detection of important biomarkers. This study describes the development of μPADs through craft cutter printing for glucose and nitrite salivary diagnostics. In addition, the use of μPADs integrated into a mouthguard as a wearable sensor for glucose monitoring is also presented. μPADs were designed to contain two detection zones for glucose and nitrite assays and a sampling zone interconnected by microfluidic channels. Initially, the analytical performance of the proposed μPADs was investigated and it provided linear behavior (r2 ≥ 0.994) in the concentration ranges between 0 to 2.0 mmol L-1 and 0 to 400 μmol L-1 for glucose and nitrite, respectively. Under the optimized conditions, the limits of detection achieved for glucose and nitrite were 27 μmol L-1 and 7 μmol L-1, respectively. Human saliva samples were collected from healthy individuals and patients previously diagnosed with periodontitis or diabetes and then analyzed on the proposed μPADs. The results found using μPADs revealed higher glucose concentration values in saliva collected from patients diagnosed with diabetes mellitus and greater nitrite concentrations in saliva collected from patients diagnosed with periodontitis, as expected. The results obtained on μPADs did not differ statistically from those measured by spectrophotometry. With the aim of developing paper-based wearable sensors, μPADs were integrated, for the first time, into a silicone mouthguard using a 3D-printed holder. The proof of concept was successfully demonstrated through the monitoring of the glucose concentration in saliva after the ingestion of chocolate. According to the results reported herein, paper-based microfluidic devices offer great potential for salivary diagnostics, making their integration into a silicone mouthguard possible, generating simple, low-cost, instrument-free, and powerful wearable sensors.

Abstract  Under the background of Cd (50 μmol·L-1) stress, we added ethylene precursor ACC (100 μmol·L-1), ACC + nitric oxide synthase (NOS) inhibitor L-NNA (200 μmol·L-1), ACC + nitrate reductase (NR) inhibitor Tu (1 mmol·L-1), ACC + nitric oxide (NO) scavenger PTIO (200 μmol·L-1), NO donor SNP (500 μmol·L-1), SNP + ethylene signal inhibitor STS (100 μmol·L-1) to examine their effects on the damage degree of leaves and response mechanisms of AsA-GSH cycle in lotus 'Weishanhuhonglian'. Results showed toxic symptom of lotus leaves under Cd stress. The relative conductivity, malondialdehyde (MDA), as well as ascorbic acid (AsA) and glutathione (GSH) contents were significantly increased, but the activities of ascorbate peroxidase (APX), glutathione reductase (GR), monodehydroascorbate reductase (MDHAR) and dehydroascorbate reductase (DHAR) were obviously decreased. Compared with Cd stress, adding ACC significantly increased the damage area of lotus leaves, decreased activities of the above-mentioned four antioxidant enzymes and increased AsA and GSH contents. SNP aggravated the toxic symptom of lotus leaves and decreased GR and MDHAR activities. PTIO significantly relieved the toxic symptom of leaves, increased activities of APX, GR, MDHAR and DHAR, but decreased AsA and GSH contents compared with Cd and ACC treatment. However, the effects of L-NNA and Tu were not as obvious as PTIO's. In comparison with Cd and SNP treatment, STS relieved the toxic symptom of leaves, increased APX, GR, MDHAR and DHAR activities, and decreased AsA and GSH contents. Taken together, these results showed the synergistic effects of ethylene and NO in regulating lotus responses to Cd stress through AsA-GSH cycle.

Abstract  Cadmium selenide quantum dots were capped with reduced graphene oxide that was modified with thioglycolic acid. The nanocomposite was prepared by 5-min sonication of a solution of graphene oxide, thioglycolic acid, and cadmium(II) nitrate and selenium powder in the presence of NaBH4. X-ray diffraction and transmission electron microscopy were used to characterize the nanocomposite. A glassy carbon electrode (GCE) was modified with this nanocomposite and used for simultaneous determination of dopamine (DA), ascorbic acid (A) and uric acid (UA). The modified GCE was characterized by using cyclic voltammetry and differential pulse voltammetry. Simultaneous determination of AA, DA and UA was accomplished at working voltages of -50, +148 and + 280 mV (all vs. Ag/AgCl), respectively. The voltammetric response to DA is linear in the 4.9 to 74.0 μM concentration range, and the detection limit (defined as 3σ of the blank) is 0.11 μM. The respective data are 0.39-1.0 mM and 66 μM for AA, and 9.0 to 120.0 μM and 0.12 μM for UA. The electrode was successfully applied to the determination of the 3 species in spiked urine samples. Graphical abstract Graphical abstract contains poor quality of text in image. Otherwise, please provide replacement figure file.Thank you for your comment. New garaphical abstract was attached. A sonochemical method was applied for synthesizing reduced graphene oxide decorated thioglycolic acid capped cadmium selenide quantum dots. A modified glassy carbon electrode was prepared for simultaneous determination of ascorbic acid, dopamine and uric acid.

Abstract  A new nonlinear optical material, the first fluoride selenite nitrate PbCdF(SeO3)(NO3), was successfully synthesized by traditional solid state reactions. This compound crystallizes in the polar space group of Pca21, and its structure features a novel 2D layered structure consisting of 1D lead nitrate chains and 2D cadmium selenite layers. PbCdF(SeO3)(NO3) exhibits a phase-matchable SHG efficiency of about 2.6 times that of KDP and a wide band gap of 4.42 eV. Its laser damage threshold was measured to be 135.6 MW/cm2, which is comparative to that of the reported Li7(TeO3)3F with a short ultraviolet cutoff edge. Theoretical calculation confirmed that the synergistic effects of all the four functional units make PbCdF(SeO3)(NO3) a remarkable SHG material.

Abstract  In the present work, polyethylenimine-capped CdS quantum dots (PEI-CdS QDs) with bright green fluorescence were synthesized and applied for sensitively and selectively detecting the nitrite in vegetable and water samples. Highly fluorescent and environment-friendly PEI-CdS QDs (quantum yield about 8%) with diameters of ca. 5 nm were easily synthesized by using hyperbranched PEI as functional polymer. Formation of the PEI-CdS QDs was verified by transmission electron microscopy and UV-vis spectroscopy. The fluorescence intensity of the as-synthesized PEI-CdS QDs was enhanced pronouncedly by the increasing amount of PEI and was stable when the pH ranged from 5.0 to 9.0. Our results demonstrated that the fluorescence of the PEI-CdS QDs was effectively quenched by the nitrite in a rather wide linear range of 1.0 × 10-7-1.0 × 10-4 M while efficiently avoiding the interferences from nitrate ions and other commonly coexisting anions of nitrite in the vegetable samples. The detection limit of the present method was lower than the maximum limit of nitrite in drinking water (6.5 × 10-5 M) ruled by the World Health Organization, which is significant to the application of the method.

Abstract  A novel hydrophobic ionic liquid including an N,N,N',N'-tetrakis(2-methylpyridyl)-1,2-phenylenediamine-4-amido structure ((IL-1,2-tpbd)+NTf2-) was successfully synthesized. (IL-1,2-tpbd)+NTf2- combined one amido (O-hard donor) and four pyridine (N-soft donor) groups. Its Cd2+ and Zn2+ separation behavior in nitric acid solution was investigated as a function of the extraction time, effect of pH etc. by dissolving (IL-1,2-tpbd)+NTf2- in a room temperature ionic liquid, 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ((C6mim)+NTf2-). The extraction kinetics were fairly fast and could reach equilibrium within 4 h. When pHeq ≥ 1.8, the extraction percentage of Cd2+ and Zn2+ remained constant and the maximum separation factor was calculated as 12.78 at pHeq = 3.1; when pHeq < 1.8, the extraction percentage of Cd2+ and Zn2+ decreased drastically due to the protonation of the pyridine groups. Complete stripping of the extracted Cd2+ and Zn2+ from the ionic liquid phase into an aqueous phase was successfully achieved under highly acidic conditions ([HNO3] = 2 M) without adding any other metal complex forming agents. The extraction mechanism was summarized as a cation exchange due to the independence of nitrate ions in the extraction process. Additionally, the results of the slope analysis and UV-vis titration revealed the formation of a 1 : 2 complex. Furthermore, (IL-1,2-tpbd)+NTf2- showed a higher preference for Cd2+ even under the interference of various co-existing metal ions.

Abstract  Nitroalkane oxidase (NAO) and nitronate monooxygenase (NMO) are two different types of nitroalkane oxidizing flavoenzymes identified in nature. A previous study suggested that the hypothetical protein PA4202 from Pseudomonas aeruginosa PAO1 is NMO and utilizes only anionic nitronates. However, the structural similarity between the PA4202 protein and Streptomyces ansochromogenes NAO has motivated investigation for what features of the two enzymes differentiate between the NAO and NMO activities. Herein, we report the crystal structure of PA4202 in a ternary complex with a neutral nitroethane (NE) and flavin mononucleotide (FMN) cofactor to elucidate the substrate recognition mechanism using a site-directed mutagenesis. The ternary complex structure indicates that the NE is bound with an orientation, which is poised for the proton transfer to H183 (which is the essential first catalytic step with nitroalkanes), and subsequent reactions with FMN. Moreover, a kinetic study reveals that the catalytic reactions of the wild type and H183 mutants PA4202s with nitroalkane substrates may yield the products of hydrogen peroxide and nitrite that are specified to NAO, although they show a low catalytic efficiency. Our results provide the first structure-based molecular insight into the substrate binding property of the hypothetical protein PA4202, including the interactions with neutral nitroalkanes as the substrate.

Abstract  Objective: To assess the quality of freshwater aquifers (springs) associated diseases, and indigenous perception in Ghizer, Gilgit-Baltistan.Methods: This was a cross-sectional study conducted at the department of environmental science, Karakoram International University Gilgit after approval from departmental research committee. In order to get the most accurate results, 18 water samples in triplicates were collected according to our lab own set of sampling standard operating procedures (SOPs) using pre-sterilized bottles of 100 ml from June 2016 to August 2016 along with associated diseases record and structured interviews from indigenous population. For physicochemical and microbial assessment, samples were tested before five hours after collection and associated diseases and indigenous perception was analyzed using descriptive statistical techniques.Results: Findings revealed that levels of pH, EC, phosphates, TDS, and nitrite, fall within WHO standards except nitrate, temperature and turbidity. The highest concentration (mgL(-1) +/- SE) of Hg in Barkolti and Barsat springs were (0.01 +/- 0.005) and (0.02 +/- 0.001) while Zn was (0.04 +/- 0.02) respectively. The concentration of Cu in Barkolti spring was (0.2 +/- 0.03) while in Barsat spring below the detection level. The concentration of Cd, Pb, Cr, and Fe in both springs fall within WHO permissible limits. The mean value of E. coli recorded in both Barkolti and Barsat aquifers were (1.08cfu +/- 0.45) and (2.11cfu +/- 0.56) respectively. The prevalence of water-associated diseases recorded in the order diarrhea, dysentery, typhoid, cholera, hepatitis and their incidence increases at high peak in summer. Irrespective of physicochemical and microbial components, indigenous population believed that the spring water has curative properties.Conclusions: Physiochemical and microbial parameters of spring's water fall within WHO standards except nitrate, turbidity, temperature, and E. coli, and incidence of certain associated diseases. However, indigenous population is unaware about the fact and believed that spring water very safe.

Abstract  Despite numerous studies having been conducted on the stabilization of heavy metal contaminated soil, our understanding of the mechanisms involved remains limited. Here green synthesized iron oxide nanoparticles (GION) were applied to stabilize cadmium (Cd) in a contaminated soil. GION not only stabilized soil Cd, but also improved soil properties within one year of incubation. After GION application both the exchangeable and carbonate bound Cd fractions decreased by 14.2-83.5% and 18.3-85.8% respectively, and most of the Cd was translocated to the residual Cd fraction. The application of GION also strongly altered soil bacterial communities. In GION treatments, the abundance of Gemmatimonadetes, Proteobacteria, and Saccharibacteria increased which led to a shift in the dominant bacterial genera from Bacillus to Candidatus koribacter. The variation in bacteria confirmed the restoration of the contaminated soil. The most abundant bacterial genus and species found in GION treatments were related to (i) plant derived biomass decomposition; (ii) ammoxidation and denitrification; and (iii) Fe oxidation. GION application may enhance the formation of larger soil aggregates with anaerobic centers and coprecipitation coupled Fe (II) oxidization, ammoxidation and nitrite reduction followed by Fe mineral ripening may be involved in Cd stabilization. The predominant stabilization mechanism was thus coprecipitation-ripening-stabilization.

Abstract  Nitrogen (N) emissions associated with urbanization exacerbate the atmospheric N influx to remote ecosystems - like mountains -, leading to well-documented detrimental effects on ecosystems (e.g., soil acidification, pollution of freshwaters). Here, the importance and fate of N deposition in a watershed was evaluated along a montane to urban gradient, using a multi-isotopic tracers approach (Δ17O, δ15N, δ18O of nitrate, δ2H and δ18O of water). In this setting, the montane streams had higher proportions of atmospheric nitrate compared to urban streams, and exported more atmospheric nitrate on a yearly basis (0.35 vs 0.10 kg-Nha-1yr-1). In urban areas, nitrate exports were driven by groundwater, whereas in the catchment head nitrate exports were dominated by surface runoff. The main sources of nitrate to the montane streams were microbial nitrification and atmospheric deposition, whereas microbial nitrification and sewage leakage contributed most to urban streams. Based on the measurement of δ15N and δ18O-NO3-, biological processes such as denitrification or N assimilation were not predominant in any streams in this study. The observed low δ15N and δ18O range of terrestrial nitrate (i.e., nitrate not coming from atmospheric deposition) in surface water compared to literature suggests that atmospheric deposition may be underestimated as a direct source of N.