Polycyclic aromatic hydrocarbon and ionic compositions of atmospheric bulk deposition samples at a national park under the influence of intense barbecue smoke

The main aim of this study was to present the effects of barbecue smoke on a small-scale environment, a national park under the influence of intense barbecue smoke, and to scientifically support the sustainable usage of the park. Twelve-weekly bulk deposition samples were collected directly at the barbecuing area, and the samples were analysed for 16 US EPA’s priority PAH compounds and major ions. The mean concentrations of the individual PAHs in the bulk deposition samples ranged from 11.8 ng L^?1 (Ane) to 1085 ± 581 ng L^?1 (IcdP). The most frequently observed PAH compounds in the bulk deposition samples were Np, Anp, Flr, Phe, An, Flu, BkF, BaP and IcdP. The mean total PAH deposition fluxes were determined as 3.6 ± 5.6 µg m^?2 day^?1. The chloride, potassium and the sulphate fluxes were determined as 145.2 ± 267.8 µg m^?2 day^?1, 182.9 ± 291.9 µg m^?2 day^?1, and 111.9 ± 65.9 µg m^?2 day^?1, respectively. Dominant ions in the bulk deposition samples were potassium ion, chloride and sulphate which addressed as the fingerprint of barbecue grilling.     

OH stretching frequencies of solid hydroxides and of free OH− ions

The vibrational frequency of free OH^? ions, which cannot be directly measured, has been claimed to be 3700 cm^?1. In solid hydroxides the OH stretching frequency has been found in the range from 3690 to 3100 cm^?1. The decrease of the vibrational frequency has been interpreted to be caused by hydrogen bridges or the increase of the metal oxygen bond strength. We suggest an alternative explanation. The vibrational frequency of unperturbed OH^? ions is 3570 ± 10 cm^?1. In ionic hydroxides this frequency is increased due to repulsion effects of the lattice or decreased if hydrogen bonds are present, to a large extent (up to 400 cm^?1) in the case of common OH^?….X bridges and only up to 70 cm^?1 in the case of XH….OH^? bonds.     

The negative ion mass spectra of methanol and deuterated methanol

The negative ion mass spectra of methanol, methanol-d and trideuteromethanol have been measured at 70 eV. Use of deuterated methanols has enabled the ion at m/e 31 to be identified as CH₃O^? and not CH₂OH^?. Isotope effects have been determined for H^? and D^? formation, and for OH^? and OD^? formation. It has been shown that OH^? formation occurs as a rearrangement reaction as well as by simple C? O bond fission.     

pH‐Dependent Degradation of Layered Black Phosphorus: Essential Role of Hydroxide Ions

The practical application of layered black phosphorus (LBP) is compromised by fast decomposition in the presence of H₂O and/or O₂. The role of H₂O is controversial. Herein, we propose a hydroxide ion (OH^?)‐initiated degradation mechanism for LBP to elucidate the role of H₂O. We found that LBP degraded faster in alkaline solutions than in neutral or acidic solutions with or without O₂. Degradation rates of LBP increased linearly from pH 4 to 10. Density functional theory (DFT) calculations showed that OH^? initiated the decomposition of LBP through breaking the P?P bond and forming a P?O bond. The detection of hypophosphite, generated from OH^? reacting with P atoms, confirmed the hypothesis. Protons acted in a way distinctive from OH^?, by inducing deposition/aggregation or forming a cation–π layer to protect LBP from degradation. This work reveals the degradation mechanism of LBP and thus facilitates the development of effective stabilization technologies.     

Simultaneous Determination of Atrazine and Chlorpyrifos in Pesticide Formulations,in Soils and Waters by Derivative Spectrophotometry and Ratio Spectra Derivative

Abstract

A new method is described to analyse a binary mixture of atrazine and chlorpyrifos, using first-derivative spectrophotometry for atrazine and first derivative of the ratio spectra for chlorpyrifos. The procedure does not require any separation step. Calibration graphs were linear up to 15 μg.mL^?1 of atrazine and to 10 μg.mL^?1 of chlorpyrifos. The method has been applied to determine both compounds in pesticide formulations, in soils and waters.     

Activity changes of glassy carbon electrodes caused by their exposure to OH• radicals

GC electrodes were exposed to Fenton solutions. The surface changes produced by the OH^? radicals of these solution were inspected using SEM, XPS, Raman spectroscopy and electrochemistry. The OH^? radicals caused erosion and roughening of the surface, selective oxidation and dissolution of sp² carbon, and reduction of the number of nucleation sites for silver deposition.     

An optical-fibre laser photometer for on-line measurements

An optical-fibre laser photometer is described for measuring on-line the concentration of the different oxidation states of uranium and plutonium. It is based on a dye laser with five exchangeable curvettes containing five different dyes. The dye laser is pumped by a nitrogen laser. To compensate for the influence of the concentration of nitrate on the absorbance of the different species, the conductivity of the solution is measured to give a correction factor. Fibre optics are used to connect the dye laser, the optical flow-through cell and the photometer. The deviation for the plutonium concentration for single-sample analysis is <1 g l^?1 for concentrations up to 50 g l^?1, and in the on-line mode is <0.14 g l^?1 for the same concentration range. For uranium, the deviation is <3.07 g l^?1 for a concentration range up to 77 g l^?1 in the on-line mode.     

Metal Complexes with Macrocyclic Ligands. Part XXVII. Cu2+-promoted hydrolysis of carboxylic- and phosphonic-acid esters in the side chain of tetraazamacrocycles

The X-ray structures of the Cu²⁺ complexes of 1,4,8,11-tetraazacyclotetradecane derivatives with an ethylpro-pionate and diethylphosphonate group, 5 and 6 , respectively, indicate that the metal ion is pentacoordinated by the four N-atoms of the macrocycle and one O-atom. In the case of 5 , it is the carbonyl O-atom of the carboxylate group, whereas for 6 it is the phosphonyl O-atom of the phosphonate group. The hydrolysis kinetics of the functional group in the Cu²⁺ complexes with the 1,4,8,11-tetraazacyclotetradecanes 3 – 6 have been measured by pH-stat and stopped-flow techniques. The rate law for the hydrolysis of the carboxylates 3 – 5 is proportional to the complex concentration and to [OH^?] up to pH 13, whereas that of the phosphonate 6 is proportional to [OH^?] up to pH 11.5, becoming independent of [OH^?] at pH > 11.5. The mechanisms of these two reactions are discussed, considering the possibility of an intra- or an intermolecular OH^? attack and the results of the X-ray structure analyses.     

Temporal variation of 7Be fallout and its inventory in purple soil in the Three Gorges Reservoir region, China

The deposition flux of ⁷Be was measured in the range from 0.4 to 5.2 Bq m^?2 d^?1, with a mean value of 2.6 Bq m^?2 d^?1, during the period of May 31, 2009?CMay 31, 2010 in the Three Gorges Reservoir region, China. The low annual deposition flux of ⁷Be was probably due to the adsorption of ⁷Be within high altitude clouds and the Qinling-Daba Mountain??s barrier and blocking effects on the cold air during winter months. There was a seasonal trend for ⁷Be deposition, showing a spring maximum and winter minimum, which may be attributed to the seasonal folding of tropopause in spring and little rainfall amount in winter. A strong positive correlation (R ² = 0.67) between ⁷Be deposition flux and rainfall was observed. The depth distribution of ⁷Be in undisturbed purple soil profiles suggested that the nuclide was mainly distributed within the top 20.0 kg m^?2 (~1.5 cm) of soil in depth and the maximum concentration occurred at a depth of 3.0 kg m^?2 (~0.2 cm), then the concentration declined quickly and exponentially with depth. The seasonal inventories of ⁷Be in soils were consistent with the values calculated from the atmospheric fluxes, which shows a great potential for using ⁷Be as a tracer to assess soil redistribution in purple soil areas of China.     

Fluorine Determination in a Hollow Cathode Discharge by Monofluoride Emission Spectra

Abstract

The applicability of the SiF and InF bands to determination of fluorine in a hollow cathode discharge has been studied. The InF bands have been used for the F determination in solid samples containing from 1% to 1x10^?4% F, and in solutions for the F^? concentration between 10 and 1000 mg 1^?1. The lowest detected amount of fluorine in solid sample was 10 ng (1x10^?5%).     

Nicotinamide complex of silver(III) with expanded coordination number

Abstract

In strongly alkaline media ([OH^?]?≥?0.12 M), nicotinamide (nica) forms a complex with square-planar Ag(OH)₄^? [nica]?≥?0.05 M. The complex decomposes in seconds to nicotinamide N-oxide. The correlation of maximum absorbance of the complex with concentrations of nicotinamide and hydroxide requires that the complex is either the five-coordinate Ag(OH)₄(H_-1nica)^2? or the six-coordinate Ag(OH)₅(nica)^2?. Comparison with the reactions of Ag(OH)₄^? with nicotinate ion (nic^?) and acetamide under similar conditions indicates that nicotinamide coordinates with Ag(OH)₄^? by the amido group rather than the nitrogen on the pyridine ring or the amido oxygen. Kinetics of the Ag(III)-nica redox reaction are consistent with direct reaction between nicotinamide and uncoordinated Ag(OH₄)^?. Oxidation takes place at the pyridine ring, yielding nicotinamide N-oxide. Silver(III) is reduced to monovalent silver.     

The Nonreversibility of Adsorption-Desorption of Dieldrin and Lindane on Chitin in Seawater

Abstract

Adsorption and desorption of dieldrin and lindane on chitin were investigated in seawater batch tests as a function of chitin concentration, temperature, pH and salinity. For chitin concentrations ranging from 0.5 g l^?1 to 12.5 g l^?1, the pesticide concentrations were varied from 4 μgl^?1 to 65 μg^?1 for dieldrin and from 40 μl^?1 to 680 μg l^?1 for lindane. Both dieldrin and lindane show adsorption-desorption hysteresis at low chitin concentration. At high chitin concentrations (m > 6.25 g l^?1 for dieldrin and m > 10 gl^?1 for lindane) both pesticides exhibit reversible behaviour. However, only lindane adsorption is affected by chitin concentration. These types of behaviour remain fixed in prewashed chitin. However, an increase in the temperature and a decrease in the salinity made the process become reversible. A resistant-reversible two component model has been applied to account for these types of behaviour and provides a way to explain most of the observed effects by defining mass independent distribution coefficients.     

Spatial distribution of 7Be in soils of Lower Austria after heavy rains

The ⁷Be approach in estimating the erosion rates is based on the assumption that the deposition of ⁷Be fallout associated with the erosive event is spatially uniform. The objective of the present work was to verify this assumption by assessing the influence of heavy rainfalls on the ⁷Be spatial distribution in Seibersdorf soils, Austria. Incremental and bulk soil depth profiles were collected from a flat site, undisturbed for the last 9 months prior sampling and with no evidence of erosion or deposition after the occurrence of heavy rains (>30 mm day^?1). The mean value of the ⁷Be areal activities (Bq m^?2) measured at 10 different points from the selected area was 312 Bq m^?2. This value corresponded to a total rainfall of 295 mm within the last 5 months prior sampling, considering that the highest mass activity of ⁷Be at soil surface will decay below the minimum detectable activity after 5 months’ time. The resulted coefficient of variation had a value of 19 % showing acceptable spatial variability of ⁷Be fallout connected with individual storm events on a local scale.     

Investigations of Polyoxometalates in Aqueous Solutions. I. The Formation of Al13(OH)7+ 31 Cation

Abstract

The formation of polyhydroxo aluminum(III) complexes has been investigated at 30°C and in a 3 M (K)Cl ionic medium by p[H] measurements. The uncommon “integral titration” technique employed has enabled measurements of oversaturated solutions up to OH^? to Al(III) ratios as large as 2.65. This has allowed the detection of the undescribed species Al₁₃(OH)⁴⁺ ₃₅. The data can very satisfactorily be explained by assuming the species Al₂(OH)⁴⁺ ₂, Al₃(OH)³⁺ ₆, Al₁₃(OH)⁷⁺ ₃₂, and Al₁₃(OH)⁴⁺ ₃₅. The Al(III) concentration has been changed from ≈0.0025 to ≈ 0.040 M and the spacings of the titration curves at different aluminum levels are a clear and direct evidence for the formation of Al₁₃(OH)⁷⁺ ₃₂, which dominates the hydrolysis products. The data presented in this paper are best accounted for if the trimer Al₃(OH)³⁺ ₆ is substituted for Al₃(OH)⁵⁺ ₄ which is frequently reported. The formation of the “13” cations may result from the reaction of four Al₃(OH)³⁺ ₆ with a transient Al(OH)^? ₄ species which is formed, upon addition of a rather concentrated basic solution, owing to a local excess of OH^?.     

The mechanism of the reaction between hydroxyl ions and some internally hydrogen-bonded acids

The kinetics of the proton transfer between hydroxyl ions and phenylazoresorcinol, 4-(p-nitrophenylazo), and 4-(m-nitrophenylazo) resorcinol have been investigated at 25°C and an ionic strength of 0.1M, in a wider pH range than had been done by previous authors. The rate at first decreased with decreasing [OH^?], reached a minimum, and then started to increase with decreasing [OH^?]. This unusual effect is explained by a mechanism suggested earlier for tropaeolin O. Rate constants and equilibrium constants have been evaluated and discussed. The experimental data were obtained by the T-jump method.     

Oxygen electrodes in fused salts: Investigation and mechanistic remarks on the system (Ni)O2, H2O/OH− in the (Na,K)NO3 eutectic melt

A potentiometric investigation on the system (Ni)O₂, H₂O/OH^? was carried out within the temperature range 513?T?636 K in the (Na, K)NO₃ equimolar mixture containing OH^? ions in the concentration range 5×10^?6<[OH^?]<10^?1m and flushed with a mixture of O₂ and H₂O at variable partial pressures. The system has been found to behave reversibly in all hydroxide concentration and temperature intervals studied with respect to all the species involved in the over-all electrode reaction ½ O₂+H₂O+2e^?=2OH^? so that the following nernstian relationship could be written E=E_O2,H₂O/OH^?+RT/Fln{[O₂]^1/4[H₂O]^1/2/[OH^?]} This potentiometric behaviour was tentatively interpreted on the basis of mechanistic models involving, in some steps, solid nickel oxides formed on the electrode surface by contact with the melt. The actual formation and existence of these compounds on the electrode surface under the given experimental conditions was proved by a proper XPS investigation.     

Electroanalytical Determination of Arsenic(III) and Total Arsenic in 1 mol L−1 HCl Using a Carbonaceous Electrode Without a Reducing Agent

Abstract

Arsenic(V) [As(V)] was reduced to As(0) at pH 0.0 and As(III) at pH 4.5 on a carbon-paste electrode modified with hematite, which allowed their selective determination. Arsenic(V) suffered interference from copper (Cu) and bismuth (Bi). Arsenic(III) was almost free of them. Humic acid did not affect the signal of As(V) but increased the signal of As(III). Arsenic was preconcentrated at ?0.8 V for 100 s. The response was linear up to 70 µg L^?1 for As(V) and 50 µg L^?1 for As(III). The limits of detection were 2 µg L^?1 and 5 µg L^?1 respectively. This method was applied to drinking water and compost lixiviate.     

First‐principles calculation of OH−/OH adsorption on gold nanoparticles

The OH^? and OH adsorption structures on Au₅₅ and Au₁₃ nanoparticles surfaces are analyzed using density functional theory. The most stable OH^? adsorption site of Au₅₅ and Au₁₃ nanoparticles is found to be the vertex top site followed by the (111)‐(100) edge bridge site. On the contrary, the stability order of OH adsorption is opposite to that of OH^?. The adsorption of OH^? is calculated to be weaker than that of OH, which shows different charge transfer and interactions with gold surface. Coadsorption on nanoparticles is studied to find that multiple OH^? species prefer the most stable sites of single OH^? adsorption. The hydrogen bonding between adsorbed OH^? on gold surface is a key factor in stabilizing the adsorbates on the Au surface. © 2015 Wiley Periodicals, Inc.     

Sensitivity Enhancement of the Fluorometric Determination of Aluminum by the Use of Surfactant

Abstract

The effects of surfactants on fluorescence analysis were studied. The addition of surfactants to a metal complex solution causes a remarkable enhancement of fluorescence. By means of such phenomenon the sensitivity of the fluorometric determination of aluminum was increased about six-fold over conventional methods. From the stability of the chelate complex in the presence of surfactant and the degree of enhancement of fluorescence, the nonionic surfactant was judged to be the most useful of the types of surfactants: cationic, anionic and nonionic. An ultramicro amount of aluminum, 5 × 10^?10 g Al/ml, could be determined by the proposed method.     

The Role of Substitutional Defects in Order/Disorder Phenomena of OH− Ions in Hydroxyapatite

We report on density functional quantum mechanical calculations of hydroxyapatite. The central focus is dedicated to the local arrangement of hydroxide ions in proximity of defects originating from substituting OH^? by F^? or O^2? ions. At ambient conditions the preferred structure of bulk hydroxyapatite exhibits an ordering of OH^? ions oriented in rows along the [001] direction. From zero Kelvin geometry optimizations the orientation inversion of a hydroxide ion was found to be disfavored by 0.165 eV. This picture changes dramatically when replacing one of the OH^? ions by a fluoride ion. The preferred hydroxide ion arrangement next to the F^? defect was identified as an OH^?··F^?··HO^? constellation, which implies the orientation inversion of one of the neighboring hydroxide ions. An analogous phenomenon was observed for O^2? defects.