Abstract  Hydrosedimentological conditions of floodplain rivers can affect nutrient delivery processes. This study evaluated the effects of sedimentological and hydrological regimes on nitrogen (N) speciation and transport in the floodplain-river system of the Middle Parana. Relations of sedimentological and hydrological regimes, assessed through turbidity and hydrometric level, with N speciation and concentration were analyzed. Simple linear regressions were performed to assess whether N load changed within the main channel in response to hydrological and sedimentological regimes. From the main channel to the floodplain, dissolved inorganic N decreased; however, the most isolated lake had the highest N concentration, almost totally in organic form. Turbidity was negatively associated with concentrations of nitrate-N (NO3-N), nitrite-N (NO2-N), and dissolved organic N (DON), and relative contributions of these N forms to total N (TN) but was positively correlated to particulate N (PN) and ammonium-N (NH4-N). The hydrometric level was positively associated with DON concentration and its relative contribution at the main channel but negatively associated with DON, PN, and TN concentrations in the most isolated lake. Simple linear regressions showed that the sedimentological regime significantly explained all N forms but not TN load. Flooding increased TN and mainly DON load. The results show that the hydrosedimentological regime largely affects N transport and speciation. The sediment peak incorporates PN to the system and affects dissolved N speciation, probably through effects of suspended particles on redox reactions. The increase of N inputs to the fluvial system during the flood could be caused by DON exportation from the floodplain.

Abstract  Bioaugmentation was used to upgrade the nitrification process in a full-scale municipal WWTP with an A2/O system. A mixture of nitrifying bacteria was inoculated into the bioreactor for a final concentration of 1% (v/v). The upgrade process took 25 days, and the NH4+-N removals reached 94.6% (increased at least by 75%). The effluent concentrations of COD and NH4+-N stabilized at <30 mg/L and <4 mg/L even when the corresponding influent concentrations were over 300 mg/L and 60 mg/L, which met the first-class requirement of the National Municipal Wastewater Discharge Standards of China (COD ≤ 50 mg/L, NH4+-N ≤ 5 mg/L). The succession of the microbial community showed the enhanced NH4+-N removal efficiency mainly resulted from the persistence of introduced ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), which increased from 0% to 0.4% and from 0.01% to 2.1%, respectively. This bioaugmentation was shown as an effective technology for upgrading or retrofitting conventional systems to tertiary-level.

Abstract  Pasture-based livestock agriculture is a major source of greenhouse gas (GHG) nitrous oxide (N2O ). Although a body of research is available on the effect of urine patch N or fertiliser N on N2O emissions, limited data is available on the effect of fertiliser N applied to patches of urinary N, which can cover up to a fifth of the yearly grazed area. This study investigated whether the sum of N2O emissions from urine and a range of N fertilisers, calcium ammonium nitrate (CAN) or urea +/- urease inhibitor +/- nitrification inhibitor, applied alone (disaggregated and re-aggregated) approximated the N2O emission of urine and fertiliser N applied together (aggregated). Application of fertiliser to urine patches did not significantly increase either the cumulative yearly N2O emissions or the N2O emission factor in comparison to urine and fertiliser applied separately with the emissions re-aggregated. However, there was a consistent trend for approximately 20% underestimation of N2O loss generated from fertiliser and urine applied separately when compared to figures generated when urine and fertiliser were applied together. N2O emission factors from fertilisers were 0.02%, 0.06%, 0.17% and 0.25% from urea +/- dicyandiamide (DCD), urea + N-(n-butyl) thiophosphoric triamide (NBPT) + DCD, urea + NBPT and urea, respectively, while the emission factor for urine alone was 0.33%. Calcium ammonium nitrate and urea did not interact differently with urine even when the urea included DCD. N2O losses could be reduced by switching from CAN to urea-based fertilisers.

Abstract  The aim of this study was to evaluate the efficiency of the combined septic tank and constructed wetland systems as series when they are easily operated in a small community such as training camp. Using the septic tank for sanitary wastewater treatment in a small community can be an effective preliminary process. The nitrate and phosphate concentrations could be effectively decreased in the effluent by using the constructed wetland. By using the series treatment process, the removal efficiencies of ammonia, nitrate, nitrite, and phosphate were reported to be 40.11%, 37.91%, 19.49%, and 39%, respectively. Also, the removal efficiencies of total coliform and fecal coliform were found 5 log and 4 log units, respectively. Using disinfection unit will be necessary before discharging of the total and fecal coliforms in the effluent to the environment. In this study, the quality of the treated wastewater was found to be according to the acceptable Iranian effluent standards for wastewater reuse in irrigation.

Abstract  In this work, Au neuronal-like nanostructures (Au NNs) were synthesized by a facile N-methylimidazole-assisted aqueous method, using ascorbic acid as the reducing agent. The as-prepared Au nanocrystals exhibited improved electrocatalytic performances for the reduction of azathioprine, which was further explored to construct an azathioprine sensor with low detection limit of 0.033 mu M (S/N =3), wide linear range from 0.5 to 2300 mu M, good reproducibility, and long-term stability. The as-synthesized Au architectures provide more potential applications in the fabrication of (bio) sensors. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  The availability of high-quality drinking water is currently the one out of the most acute problems in the Russian Federation. There was performed an analysis of the chemical composition of drinking water from sources of decentralized supply of inhabitants of the city of Yekaterinburg and the surrounding areas. Average values of indices of the water quality in the wells for individual use in the district of the city of Yekaterinburg not go beyond the standards, with the exception of manganese content. In some sources there were revealed elevated values of chromatic level, oxidability, hardness, content of iron, nitrates, barium, dry residue, ammonium nitrogen, silicon. Percentage of sources that do not meet hygienic requirements on a number of indices can reach 21-23%.

Abstract  The contamination level of oxbows depends on both natural and anthropogenic effects. The aim of our study was to identify those abiotic and biotic factors that determine the contamination level of oxbows. The effect of anthropogenic activities, seasonality, and vegetation types was studied on the contamination level of surface water of oxbows. The following chemical variables were measured: suspended solid, ammonium, nitrate, chlorophyll-a, Al, Ba, Fe, Mn, Pb, Sr and Zn from eight oxbows from 2013 summer to 2014 autumn in the Upper Tisza region in Eastern Hungary. Three of the studied oxbows were protected, four oxbows were used for fishing and one oxbow was contaminated with wastewater. Our findings revealed that anthropogenic activities had remarkable effect on the contamination level of oxbows. Seasonality also influenced the contamination level, except the concentration of suspended solid, chlorophyll-a and manganese. Significant differences were found among vegetation types for the concentration of suspended solids, aluminium, iron, manganese and lead. The high level of iron concentration was not explained by the anthropogenic activities, suggesting that the quality of oxbows depends on both natural and anthropogenic effects.

Abstract  Understanding the effects of sediment disturbances on nutrient loadings is important for the management of estuarine settings. This study investigated the initial influence of sediment disturbance on water column nutrient concentrations in a shallow estuarine setting within the Gold Coast Broadwater, using a laboratory-based approach. Undisturbed sediment cores (200 mm Ø × 330 mm length, plexiglass) were incubated before and after being subjected to a disturbance event, to investigate the effect on the immediate and subsequent short-term water column nutrient concentrations. Sediment NH4+bio and PO43−bio concentrations ranged from 150 to 478 and 1.50 to 8.56 nmol g−1 dry wt, respectively. Water column NH4+ concentrations underwent the greatest increase (>1000% or approx. 14 times greater) immediately following disturbance, with mean effluxes increasing by >300%. Thereafter, water column NH4+ concentrations and efflux rates declined to near initial pre-disturbance concentrations. Water column NH4+ concentrations accounted for 0.58%-5.50% of the depth-integrated sediment NH4+bio concentration, indicating mobilization of the sediment bound exchangeable NH4+. The observed changes in PO43− concentrations and fluxes were much lower in comparison to those observed for N-species. Following disturbance, increases in the water column PO43− concentration accounted for 7.16%-8.22% depth-integrated sediment bioavailable PO43− at +1 and +2 hours, and 5.65% at +7 hours, respectively. These results provide important insight into the potential implications of disturbance events, such as vessel activities and dredging operations, within the case study region, providing information for potential management options and relevant water quality concerns.

Abstract  Diffusion, rheology, and small angle neutron scattering (SANS) data for organic phase 30 v/v %tributyl phosphate (TBP) samples containing varying amounts of water, nitric acid, and uranium or zirconium nitrate were interpreted from a colloidal perspective to give information on the types of structures formed by TBP under different conditions. Taken as a whole, the results of the different analyses were contradictory, suggesting that these samples should be treated as molecular solutions rather than colloids. This conclusion is supported by molecular dynamics (MD) simulations showing the existence of small, molecular aggregates in TBP samples containing water and nitric acid. Interpretation of TBP and nitric acid diffusion measurements from a molecular perspective suggest that nitric acid and metal species formed are consistent with the stoichiometric solvates that have traditionally been considered to exist in solution. (C) 2017 Elsevier B.V. All rights reserved.

Abstract  Reactive oxygen and nitrogen species (RONS such as H2O2, nitric oxide) confer redox regulation of essential cellular functions (e.g. differentiation, proliferation, migration, apoptosis), initiate and catalyze adaptive stress responses. In contrast, excessive formation of RONS caused by impaired break-down by cellular antioxidant systems and/or insufficient repair of the resulting oxidative damage of biomolecules may lead to appreciable impairment of cellular function and in the worst case to cell death, organ dysfunction and severe disease phenotypes of the entire organism. Therefore, the knowledge of the severity of oxidative stress and tissue specific localization is of great biological and clinical importance. However, at this level of investigation quantitative information may be enough. For the development of specific drugs, the cellular and subcellular localization of the sources of RONS or even the nature of the reactive species may be of great importance, and accordingly, more qualitative information is required. These two different philosophies currently compete with each other and their different needs (also reflected by different detection assays) often lead to controversial discussions within the redox research community. With the present review we want to shed some light on these different philosophies and needs (based on our personal views), but also to defend some of the traditional assays for the detection of RONS that work very well in our hands and to provide some guidelines how to use and interpret the results of these assays. We will also provide an overview on the "new assays" with a brief discussion on their strengths but also weaknesses and limitations.

Abstract  Phosphorus (P) is a limiting factor for plant growth, especially in highly weathered tropical soils. Plants have several mechanisms to overcome low P availability in soil, such as humic substances, that reduce phosphate (P-i) adsorption on oxide surfaces and enhance soil P availability. However, the direct influence of humic substances on P-i transporters in root cells or the distribution of P species in leaves remains unclear. Tomato seedlings were grown in a sand-vermiculite mixture with low or high P concentrations (10 or 100 mg kg(-1) KH2PO4, respectively) and humic acids (0 or 48 mg C L-1) isolated from vermicompost. Plant responses were evaluated in the fifth week by measuring root and shoot weights and P concentration, and differential expression in the roots of the high-affinity P-i transporter genes LePT1 and LePT2. In addition, the distribution of P species in the leaves was assessed using P-31-NMR. Humic acids increased the root biomass and changed the distribution of P species in the leaves. Inorganic phosphate was the major compound in plants supplied with a high P concentration, whereas in plants supplied with a low P concentration, P-i was only identified in plants not treated with humic acids. Glycerophosphodiester and phosphorylcholine accumulated in plants treated with humic acid, indicating a modified metabolic pathway for economical P consumption at low P concentrations. High transcript accumulation of LePT2 was observed in roots treated with humic acids at both P concentrations. Our results show that humic substances are strategically involved in plant adaptation to P availability.

Abstract  Resistance to antimicrobial agents by pathogenic bacteria has emerged in recent years and is a major health problem. In this context silver and silver nanoparticles (AgNP) have been known to have inhibitory and bactericidal effects and was used throughout history for treatment of skin ulcer, bone fracture, and supporting wound healing. In all of these applications prevention and treatment of bacterial colonized/infected wounds are critical. In this context silver and its derivatives play an important role in health care. Silver is widely used in clinical practice in the form of silver nitrate and/or silver sulfadiazine. In the last few years silver nanoparticles entered into clinical practice as both antimicrobial and antifungal agents. In addition, nanosilver is used in coating medical devices (catheters) and as component of wound dressings. In this paper we present summarized information about silver and nanoparticles made of silver in the context of their useful properties, especially antibacterial ones, being of a great interest for researchers and clinicians.

Abstract  The study was performed to test the possibility of applying nitrate monoionic form of anion exchanger for enhanced nitrogen fertilization of degraded soils. To achieve the study aim, a pot experiment with Dactylis glomerate L. as a test species was conducted. Thirteen soil series were prepared with increasing doses of nitrogen, applied as Ca(NO3)(2)center dot 4H(2)O and nitrate form for the test purpose. It was shown that all nitrogen doses introduced into soil in nitrate form influenced plant growth advantageously, significantly increasing the values of vegetative parameters. Nitrogen doses applied in nitrate form showed the same effectiveness, because the values of vegetative parameters obtained in media series with nitrate form additions did not differ significantly. Regarding total dry biomass of plants, it could be stated that the efficiencies of application of nitrate monoionic form (in the presence of an additional Ca source) and calcium nitrate are similar for enhanced nitrogen fertilization of degraded soils.

Abstract  Three copper(II) complexes of the polydentate N-donor ligand [4-(4,6-bis(1H-pyrazol-1-yl)-1,3,5-triazin-2-yl)morpholine] (L) with chlorides, nitrates, and perchlorates as anions, namely, [CuCl2(L)]0.5(MeCN) (1), [Cu(NO3)(2)(H2O)(L)](MeCN) (2), and [Cu(L)(2)](ClO4)(2)(MeCN) (3) were synthesized and structurally characterized by IR, elemental analysis and X-ray crystallographic analysis. In these complexes, the L ligand binds the copper(II) cation in the tridentate N-3 form. The coordination arrangement around the central copper(II) atom is distorted square-pyramidal in 1 but it is distorted octahedral in 2 and 3. The interesting noncovalent interactions such as hydrogen bonds, - stacking, and anion- interactions present in the solid-state structures are discussed. The crystal results reveal that the counteranions play important roles in determining the diverse structures of these complexes. Moreover, the PXRD, TG, DRS, and fluorescence properties of compounds 1-3 were investigated.

Abstract  Spider dragline silk was coated with pure as well as Eu-doped ceria nanopowders at the room temperature. The treatment was done by immersion of the spider silkmesh into aqueous solutions of cerium nitrate (Ce(NO3)(3)) and ammonium hydroxide (NH4OH). Depending on the relationship between Ce3+ ion and ammonium hydroxide concentration, coated fibers exhibited a different thickness. Obtained materials were studied by means of FESEM. It was found that ceria nanoparticles of average size of 3 nm were coated along spider thread. X-ray diffraction (XRD) and selected-area electron diffraction (SAED) confirmed crystal nature of nanoparticle coating of spider silk. By using Williamson-Hall plots, crystallite size and strain were estimated. EDS measurement confirmed the presence of Eu in spider-Eu-doped ceria composite, and according to FTIR analysis, the interaction between CeO2 and spider silk was proposed. The morphology of obtained composite was observed by TEM. The photoluminescence emission spectra of spider silk coated with Eu-doped ceria were measured with two different excitations of 385 and 466 nm. The two-photon excited auto-fluorescence of spider silk coated with Eu-doped ceria was detected using a nonlinear laser scanning microscope. Obtained composite has a potential as a fluorescent labeling material in diverse applications.

Abstract  Background. The Baetidae family (Ephemeroptera: Insecta) is abundant and diverse in freshwater ecosystems, especially in lotic systems: Although, information on these groups in Colombia is still scarce. Goals. The present study was directed to increase the taxonomical and ecological knowledge of Baetidae family in Alvarado river basin (Tolima, Colombia), evaluating the substrates; sand, gravel/cobble, rock and leaf litter, and determining the possible relationships with some physicochemical parameters. Methods. The collection was made with a Surber net in rapids and backwaters, in four substrates (sand, gravel/cobble, rock and leaf litter) additionally physicochemical parameters were evaluated. Results. A total 2386 individuals were collected, distributed in nine genera and 14 species. Baetodes sp. (23.93%), Camelobaetidius edmunsi (19.70%), Guajirolus queremba (12.70%) and Paracloeodes binodulus (11.32%) were the most abundant species in the basin. The highest density of organisms was found in sampling sites QLCA, QCHU, RACV and RACH. Rock was the preferred substrate for colonization and establishment of most species in all sites. Conclusions. The family Baetidae was related with type of substrate, as well as variables such as; pH, alkalinity, hardness, total solids, electrical conductivity, BOD5, dissolved oxygen, water flow and nitrates, which suggest a potential influence of anthropogenic effects on species establishment.

Abstract  In the present work, nanofibrous chitin microsphere (NCM) was prepared via sol-gel transition from a chitin solution dissolved in a NaOH/urea aqueous system at low temperatures. Ag nanoparticles (AgNPs) were synthesized via an in situ reduction of silver nitrate using trisodium citrate dehydrate and were immobilized on chitin nanofibers to obtain composite microspheres that consist of nanofibers and AgNPs (NCM-Ag). The size of AgNPs could be controlled in the range of 10 to 70 nm, depending on the concentration of AgNO3. X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FT-IR) analyses showed that the chitin nanofibers have a strong affinity toward AgNPs, resulting from the interaction between the acetamino group of chitin and the AgNPs. The NCM-Ag exhibited a perfect nanoporous structure and high surface area, as well as high stability in organic solvents. Moreover, in the catalytic epoxidation of olefin (particularly, the conversion of styrene to styrene epoxide), NCM-Ag exhibited an excellent selectivity of up to 90%. Converting chitin powder into chitin microspheres using an environmentally friendly technique is a green process, which is beneficial for the large-scale synthesis of industrial products. More importantly, this work provides a green synthetic pathway for the construction of size-controlled noble metal nanoparticles immobilized on nanofiber support, which have a wide range of potential applications.

Abstract  A family of six triple-decker complexes, {(MX)2[(pz)4]3} (Hpz = 4-nitropyrazole, MX = NaCl, 1; NaBr, 2; NaI, 3; KCl, 4; KBr, 5, and KI, 6), exhibiting inclusion of halides into inverse 12-metallacrown-4 [inv-(12-MCCu(I),pz-4)] array has been realized. Single-crystal X-ray crystallography of each compound reveals a common structural feature consisting of four Cu(I) ions bonded by four pz to form a square metallomacrocycle comprising four metal centers and eight N atoms, thus giving an inv-[12-MCCu(I),pz-4] motif. Two halides are sandwiched by three inv-[12-MCCu(I),pz-4] to form triple-deckers that are further extended in an offset stacking mode by ligand-unsupported cuprophilicity interactions to form a one-dimensional chain structure. Halides are attached to six Cu(I) centers with weak Cu(I)···halogen interaction, resembling anion templates. High-resolution electrospray ionization mass spectrometry reveals that the predominant fragments corresponding to a half of the triple-decker structures of 1-3 exist in solution. Compounds 4, 5, and 6 showed excellent electrocatalytic activities toward the reduction of nitrite and can also be used as selective "turn-off" sensors for Ag(I) in water. The present results will be helpful for the future design and synthesis of functional inverse metallacrowns and their multiple-decker complexes.

Abstract  4-(methylnitrosamino)-L-(3-pyridyl)-1-butanone is an important and abundant strongly carcinogenic agent in tobacco leaves and its smoke, hence 15 kinds of tobacco samples were collected to study the formation of 4(methylnitrosamino)-L-(3-pyridyl)-1-butanone in the tobacco smoke generated by pyrolysis under inert and oxidative conditions respectively. Contents of 4-(methylnitrosamino)-L-(3-pyridyl)-1-butanone in tobacco leaves and in the smoke were compared. The effects of nicotine, reducing sugar, 02, nitrate and nitrite salts on the release of 4-(methylnitrosamino)-L-(3-pyridyl)-1-butanone were also investigated. The results show that: 1) the contents of 4-(methylnitrosamino)-L-(3-pyridy1)-1-butanone in smoke under oxidative condition were much higher than that in tobacco leaves and in smoke under inert condition; 2) nicotine and active nitrogen oxides are principal precursors and reducing sugars could prohibit the formation of 4-(methylnitrosamino)-L-(3-pyridyl)-1-butanone in smoke; 3) nitrate and nitrite salts can give rise to the release of 4-(methylnitrosamino)-L-(3-pyridyl)1-butanone in smoke (Air) dramatically, but nitrite showed less effective than nitrate; 4) 02 not only can react with nitrate and nitrite salts to decompose active nitrogen oxides, but also can react with the nitrogen-containing compounds in tobacco leaves at high temperatures, which provided more active nitrogen oxides combined with nicotine to produce 4-(methylnitrosamino)-L-(3-pyridy1)-1-butanone.

Abstract  the effects flow rates of gas, liquid, or gas composition, in non-thermal plasma (NTP) electrical discharge reactors, on nitrates and hydrogen peroxide generation in water, have been studied. The reactor set up consists of two stainless steel tubes placed in a glass tube. The effects of successive passing the same sample water through one, two or three identical columns of NTP electrical discharge, were determined by serial connection of several similar reactors (up to three). In all cases, the efficiency of the nitrates and hydrogen peroxide production in treated water in the NTP reactor(s) have been also calculated.

Abstract  In this paper, the deposition of Ca3Co4O9 + 6 layers on CGO substrates using electrostatic spray deposition (ESD) technique, starting from calcium and cobalt nitrates as precursor salts, is reported. The microstructure was investigated as a function of process parameters such as nozzle -to -substrate distance, solvent composition, substrate temperature, flow rate and deposition time, based on an upper and a lower value. Films with controlled microstructures were obtained after annealing at 880 degrees C for 2 h in air. The formation of Ca3Co4O9 + 6 was confirmed by X-ray diffraction, which also showed evidence of Co304 traces. As shown by in-situ X-ray diffraction, Ca3Co4O9 + s starts to form at 625 T and decomposes at 950 degrees C, but the transformation is reversible. Interestingly, the initial morphology of the films was maintained after annealing at either 700 or 880 degrees C, with the appearance of faceted crystals forming a gypsum flower-like microstructure. AC impedance spectroscopy was carried out at intermediate temperatures (600-800 degrees C) under air on 2 batches of symmetrical cells based on ESD and screen printed electrodes, respectively. This work confirmed the beneficial impact of the ESD technique. The area specific resistance was improved by at least 23% at 600 degrees C and 40% at 800 degrees C for the sample prepared by ESD compared to the reference one prepared by screen printing. This improvement was explained by a better interface between the electrode and the electrolyte. Published by Elsevier B.V.

Abstract  Norfloxacin (NOR) is a widely used fluoroquinolone antibacterial that has drawn much concern due to its adverse effect on aquatic ecology and human health. In this study, a novel magnetically recoverable BiOBr/iron oxides (BiOBr/Fe3O4) heterojunction photocatalyst with high photocatalytic activity on NOR was successfully synthesized using a facile in-situ coprecipitation method. The samples were characterized by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, UV-vis diffuse reflectance spectra, N-2 adsorption-desorption analysis, and vibrating sample magnetometer. Several factors affecting the catalytic performance of BiOBr/Fe3O4 were investigated. Results showed that the catalytic degradation efficiency of NOR increased with the increasing bicarbonate doses, but decreased with the increasing natural organic matter concentrations. The presence of nitrate stimulated NOR degradation by BiOBr/Fe3O4 at low concentrations but inhibited the degradation at high concentrations. The photogenerated reactive species were determined based on free radicals trapping experiments, revealing that the photodegradation of NOR over BiOBr/Fe3O4 under visible light was dominated by superoxide radicals and hydroxyl radicals rather than oxidation by direct holes. On the basis of the degradation products identified by HPLC-MS, the NOR degradation pathway was proposed. NOR possibly underwent the piperazine ring transformation, decarboxylation and defluorination to generate eleven intermediates. Toxicity assays by Vibrio fischeri proved that the NOR photocatalytic transformation products retained negligible antibacterial activity relative to the parent compound. The catalytic degradation of NOR by BiOBr/Fe3O4 was also effective in the actual natural waters. (C) 2016 Elsevier B.V. All rights reserved.

Abstract  The synthesis of rare earth oxide based Dy2O3-AuNPs nanocomposites via solvothermal and in-situ reduction method for the electrochemcial oxidation of nitrite on a glassy carbon electrode (GCE) with high catalytic activity has been reported. The obtained nanocomposites were characterized by transmission electron microscopy (TEM), UV-vis absorption and powder X-ray diffraction (XRD). The electrochemical behavior of the Dy2O3-AuNPs modified GCE was investigated. The effect of pH value on the response current of the sensor was examined. The fabricated enzyme-free sensor achieved a wide linear range of 0.01 similar to 1.0 mmol . L-1 with the detection limit of 3.3 mu mol . L-1. The linear regression equation is Ipa (mu A) = 6.70 + 51.1 C (mmol . L-1) with the square of correlation coefficient R-2 = 0.965. Furthermore, the sensor exhibited the excellent selectivity and reproducibility. When employed for the real sample analytical application, it owned appropriate recovery of nitrite in water samples, indicating the potential application in real sample analysis. (C) 2017 The Electrochemical Society. All rights reserved.

Abstract  The effectiveness of 15 chemical admixtures (including alkanolamines, alcohols, chloride/non-corrosive accelerators and retarders) on the early strength development of a P.II 52-5R cement was determined using statistical methods. The results showed that, under low dose conditions (<= 0.05 wt%), sodium thiocyanate, calcium chloride, sodium hydroxide, triethanolamine and glucose contributed to the 1-d strength enhancement of the cement and that only sodium thiocyanate, triethanolamine, triisopropanolamine and calcium chloride were effective up to 3 d. In addition to the strength test proposed by the statistical model, a calorimeter was used for a supplementary measurement to identify interactions among the chemicals. The calorimetric test results revealed that the interaction between triethanolamine and sodium thiocyanate was more pronounced for the amount of heat released before 72 h due to the accelerating effects on both the C3S and C(3)A phases. Furthermore, a statistical test showed that even at a higher dose (0.1 wt%), the effect of calcium nitrate was far less efficient than the effect of calcium chloride, which did not significantly improve the overall early strength of cement.

Abstract  An intermittent aerobic process has been developed to effectively remove nitrogen from polluted rivers. In addition, a chemometric model was developed to achieve simultaneous rapid analysis of total nitrogen, ammonia nitrogen, and nitrite nitrogen based on near-infrared spectroscopy data combined with a support vector machine. An intermittent aeration process showed that total nitrogen decreased from 54.25 mg.L-1 to 0.64 mg.L-1. Ammonia nitrogen decreased significantly in the aeration stage, but increased in the non-aeration stage. Eventually, ammonia nitrogen decreased from 45.04 mg.L-1 to 0.57 mg.L-1. Nitrite nitrogen and nitrate nitrogen increased in the aeration stage, but decreased in the non-aeration stage. The concentration ranges of nitrite nitrogen and nitrate nitrogen were, respectively, 0.05 similar to 31.40 mg.L-1 and 0 similar to 0.38 mg.L-1. The 138 water samples were collected during the intermittent aeration process, of which 116 samples were used as the calibration set and the remaining 22 samples were used as a test set in modeling. The actual concentration values and the near-infrared spectroscopy data were used as input of the models. Then the corresponding calibration values and predication values were output by the models. All the samples were scanned with near-infrared spectroscopy from 4,000 similar to 12,500 cm(-1) and measured by chemical methods. Principal component analysis of raw near-infrared spectral data showed that the matrix dimension of spectral data was significantly reduced, which decreased from 2,203x106 to 6x106. Support vector machine models of total nitrogen, ammonia nitrogen, and nitrite nitrogen showed that the calibration correlation coefficient (R-2) of calibration values and actual values were, respectively, 0.9561, 0.9661, and 0.9702, with the root mean square error of cross validation (RMSECV) being 0.09372, 0.04749, and 0.03187. The test results of support vector machine models of total nitrogen, ammonia nitrogen, and nitrite nitrogen showed that the predication correlation coefficient (R-2) of prediction values and actual values were, respectively, 0.9616, 0.9410, and 0.9284, with the root mean square error of prediction (RMSEP) being 0.09420, 0.08227, and 0.06770. This study indicated that nitrogen in a polluted river can be removed through the intermittent aerobic process. Moreover, simultaneous rapid determination of total nitrogen, ammonia nitrogen, and nitrite nitrogen may be achieved with near-infrared spectroscopy and a support vector machine. The results showed that the proposed methods provided effective treatment and detection technology for a polluted river.