Deployment of a carbon isotope ratiometer for the monitoring of CO2 sequestration leakage

In an effort to monitor leakage from underground CO(2) storage, a field-deployable analyzer capable of rapidly measuring the CO(2) mixing ratio and δ(13)C values (±0.05 ppm(v) ± 0.2‰, 60 s) was deployed to distinguish between biogenic and fossil CO(2) sources. The analyzer was interfaced with a multiport inlet unit to allow autonomous sampling from multiple locations. The instrument and inlet interface were deployed at the Zero Emissions Research and Technology (ZERT) site (Bozeman, Montana, July 14-22, 2009) during a controlled, subsurface release of CO(2) depleted in (13)C. A biogenic diurnal cycle was observed far from the release, and the associated Keeling plot suggested a CO(2) source (δ(13)C = -27.0 ± 0.5‰) consistent with local C(3) vegetation. Inlets near the leak showed large CO(2) mixing ratios (388/>40?000 ppm(v)) whose predominant source was the release CO(2) (inferred δ(13)C = -58.2 ± 0.7‰). Measurements 3 m from the source showed diurnal CO(2) cycles (382-2400 ppm(v)) influenced by leaked CO(2), possibly due to diel air mixing. Finally, the data from all of the sampling inlets was combined to spatially localize the leak position.     

Spectroscopic investigation of methylated amines by a cavity-ringdown-based spectrometer

High-resolution absorption spectra of gas-phase monomethylamine (MMA, CH(3)NH(2)) and dimethylamine [DMA, (CH(3))(2)NH] in the region of the first overtone of the NH stretch vibration are reported. Measurements were performed with a near-infrared laser spectrometer based on the cavity-ringdown (CRD) detection technique. The minimum detectable absorption coefficient for the CRD detection setup is alpha(min)=1.55 x 10(-8) cm(-1) (for SNR = 1). This corresponds to detection limits of 350 parts in 10(9) (ppb) for MMA and 1.6 parts in 10(6) (ppm) for DMA in synthetic gas mixtures under interference-free conditions, or 10 ppm and 60 ppm for MMA and DMA, respectively, in the case of gas mixtures such as exhaled human breath containing H(2)O, CO(2), and other absorbing gases in this range.     

Sulfur species in volcanic gases

A new analytical method for the determination of the sulfur species (SO2, H2S, S8(0)) in volcanic gases is proposed by revising, updating, and improving previous methods. The most significant advantages of the proposed procedure can briefly be summarized, as follows: (i) the reaction among sulfur species stops during the gas sampling by using preevacuated thorion-tapped vials with purified 0.15M Cd(OH)2 in 4 M NaOH to favor the precipitation of H2S as CdS; (ii) all the sulfur species (SO2, H2S, S8(0)) are analyzed by ion chromatography, after conversion to SO4, which allows the detection limit to be lowered significantly with respect to the previous studies; (iii) appropriate aliquots from intermediate steps may be used to determine other species commonly present in volcanic gases such as CO2, HCI, HF, HBr, HI, and so forth; (iv) determination of all the other gas species is not jeopardized by the proposed method, i.e., one single vial can be used for analyzing the full chemical composition of a volcanic gas with the exception of NH3. Statistical parameters calculated from gas sampling data at the F5 crater fumarole in Vulcano Island (Aeolian Islands, southern Italy), suggest that the standard error of mean (s/ root n) is higher for S (0.10), followed by SO2, H2S, and CO2 (0.04, 0.038, and 0.028, respectively). SO2 shows the higher variation coefficient (12.1%) followed by H2S, S, and CO2 (5.7, 1.5, and 0.8%, respectively). Furthermore, if the time dependence of sampling is taken into account, the measured values, instead of fluctuating in a random manner, tend to follow systematic patterns, out of statistical control, possibly suggesting a sort of natural fluctuation of the volcanic system. Other crater fumaroles from volcanic systems located in different geodynamical areas (Hawaii, USA, El Chichon, Mexico, Poas, Costa Rica) have been analyzed as well.     

Characterization of adsorption removal of hydrogen sulfide by waste biocover soil, an alternative landfill cover

Landfill is an important anthropogenic source of odorous gases. In this work, the adsorption characteristics of H(2)S on waste biocover soil, an alternative landfill cover, were investigated. The results showed that the adsorption capacity of H(2)S increased with the reduction of particle size, the increase of pH value and water content of waste biocover soil. The optimal composition of waste biocover soil, in regard to operation cost and H(2)S removal performance, was original pH value, water content of 40% (w/w) and particle size of ≤4 mm. A net increase was observed in the adsorption capacity of H(2)S with temperatures in the range of 4-35°C. The adsorption capacity of H(2)S on waste biocover soil with optimal composition reached the maximum value of 60±1 mg/kg at oxygen concentration of 10% (v/v). When H(2)S concentration was about 5% (v/v), the adsorption capacity was near saturation, maintaining at 383±40 mg/kg. Among the four experimental soils, the highest adsorption capacity of H(2)S was observed on waste biocover soil, followed by landfill cover soil, mulberry soil, and sand soil, which was only 9.8% of that of waste biocover soil.     

Photoacoustic spectroscopy on trace gases with continuously tunable CO(2) laser

A novel photoacoustic (PA) system that uses a continuously tunable high-pressure CO(2) laser as radiation source is presented. A minimum detectable absorption coefficient of 10(-6) cm(-1) that is limited mainly by the desorption of absorbing species from the cell walls and by residual electromagnetic perturbation of the microphone electronics has currently been achieved. Although a linear dependence of the PA signal on the gas concentration has been observed over 4 orders of magnitude, the dependence on energy exhibits a nonlinear behavior owing to saturation effects in excellent agreement with a theoretical model. The calibration of the laser wavelength is performed by PA measurements on low-pressure CO(2) gas, resulting in an absolute accuracy of ± 10(-2) cm(-1). PA spectra are presented for carbon dioxide (CO(2)), ammonia (NH(3)), ozone (O(3)), ethylene (C(2)H(4)), methanol (CH(3)OH), ethanol (C(2)H(5)OH), and toluene (C(7)H(8)) in large parts of the laser emission range. The expected improvement in detection selectivity compared with that of studies with line-tunable CO(2) lasers is demonstrated with the aid of multicomponent trace-gas mixtures prepared with a gas-mixing unit. Good agreement is obtained between the known concentrations and the concentrations calculated on the basis of a fit with calibration spectra. Finally, the perspectives of the system concerning air analyses are discussed.     

Scope and Mechanistic Study of the Coupling Reaction of α, β-Unsaturated Carbonyl Compounds with Alkenes: Uncovering Electronic Effects on Alkene Insertion vs Oxidative Coupling Pathways

The cationic ruthenium-hydride complex [(C(6)H(6))(PCy(3))(CO)RuH](+)BF(4) (-) (1) was found to be a highly effective catalyst for the intermolecular conjugate addition of simple alkenes to α,β-unsaturated carbonyl compounds to give (Z)-selective tetrasubstituted olefin products. The analogous coupling reaction of cinnamides with electron-deficient olefins led to the oxidative coupling of two olefinic C-H bonds in forming (E)-selective diene products. The intramolecular version of the coupling reaction efficiently produced indene and bicyclic fulvene derivatives. The empirical rate law for the coupling reaction of ethyl cinnamate with propene was determined as: rate = k[1](1)[propene](0)[cinnamate](-1). A negligible deuterium kinetic isotope effect (k(H)/k(D) = 1.1±0.1) was measured from both (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) and (E)-C(6)H(5)CD=C(CH(3))CONHCH(3) with styrene. In contrast, a significant normal isotope effect (k(H)/k(D) = 1.7±0.1) was observed from the reaction of (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) with styrene and styrene-d(10). A pronounced carbon isotope effect was measured from the coupling reaction of (E)-C(6)H(5)CH=CHCO(2)Et with propene ((13)C(recovered)/(13)C(virgin) at C(β) = 1.019(6)), while a negligible carbon isotope effect ((13)C(recovered)/(13)C(virgin) at C(β) = 0.999(4)) was obtained from the reaction of (E)-C(6)H(5)CH=C(CH(3))CONHCH(3) with styrene. Hammett plots from the correlation of para-substituted p-X-C(6)H(4)CH=CHCO(2)Et (X = OCH(3), CH(3), H, F, Cl, CO(2)Me, CF(3)) with propene and from the treatment of (E)-C(6)H(5)CH=CHCO(2)Et with a series of para-substituted styrenes p-Y-C(6)H(4)CH=CH(2) (Y = OCH(3), CH(3), H, F, Cl, CF(3)) gave the positive slopes for both cases (ρ = +1.1±0.1 and +1.5±0.1, respectively). Eyring analysis of the coupling reaction led to the thermodynamic parameters, Δ H(?) = 20±2 kcal mol(-1) and S(?) = -42±5 e.u. Two separate mechanistic pathways for the coupling reaction have been proposed on the basis of these kinetic and spectroscopic studies.     

Application of polyimide membranes for biogas purification and enrichment

Biogas is a clean environment friendly fuel that is produced by bacterial conversion of organic matter under anaerobic (oxygen-free) conditions. Raw biogas contains about 55-65% methane (CH(4)), 30-45% carbon dioxide (CO(2)), traces of hydrogen sulphide (H(2)S) and fractions of water vapour. Pure methane has a calorific value of 9100 kcal/m(3) at 15.5 degrees C and 1 atm; the calorific value of biogas varies from 4800 to 6900 kcal/m(3). To achieve the standard composition of the biogas and calorific value of 5500 kcal/m(3) the treatment techniques like absorption or membrane separation should be applied. In the paper the results of the tests of the CH(4) enrichment in simulated biogas mixture consisted of methane, carbon dioxide and hydrogen sulphide were presented. It was showed that using the capillary module with polyimide membranes it was possible to achieve the enrichment of CH(4) from the concentrations of 55-85% up to 91-94.4%. The membrane material was resistant to the small concentrations of sour gases and assured the reduction of H(2)S and water vapour concentrations, as well. The required enrichment was achieved in the single module, however to prevent CH(4) losses the multistage or hybrid systems should be used to improve process efficiency.     

A gas chromatographic separation for the h and C stable isotope ratio determination of coal compounds

A new, completely automated gas chromatography technique has been developed to separate the different gaseous compounds produced during underground coal gasification for their (13)C/(12)C and D/H isotope ratio measurements. The technique was designed for separation and collection of H(2), CO, CO(2), H(2)O, H(2)S, CH(4), and heavier hydrocarbons. These gaseous compounds are perfectly separated by the gas-phase chromatograph and quantitatively sent to seven combustion and collection lines. H(2), CO, CH(4), and heavier hydrocarbons are quantitatively oxidized to CO(2) and/or H(2)O. The isotopic analyses are performed by the sealed-tube method. The zinc method is used for reduction of both water and H(2)S to hydrogen for D/H analysis. Including all preparation steps, the reproducibility of isotope abundance values, for a quantity higher than or equal to 0.1 mL of individual components in a mixture (5 mL of gases being initially injected in the gas chromatograph), is ±0.1‰ for δ(13)C(PDB) and ±6‰ for δD(SMOW).     

Nationwide shift in CO concentration levels in urban areas of Korea after 2000

Concentrations of carbon monoxide (CO) in urban and rural air were analyzed from 16 urban roadside locations in the 7 major cities along with 5 background areas in Korea during an 11-year period (1998-2008). Because of noticeable changes in CO levels after 2000, temporal evaluation of its roadside data was carried out by grouping them into period I (1998-2000) and II (2001-2008). The mean CO values for all 16 roadside stations between the two study periods I and II were significantly different from each other (1.67 ± 0.31 ppm (I) vs. 0.95 ± 0.17 ppm (II)). This interperiod reduction in CO levels fell, if compared between different stations, in the range of 8.62-59.94% (mean = 39.8 ± 14.7%). The statistical analysis confirms that CO concentrations decreased very rapidly with the annual reduction rate of 0.093 ppm year(-1) (9.8% year(-1)). In contrast, in background areas such distinctions are no longer valid between the two periods. A line of evidence collected in this study thus suggests that the implementation of legal and technical support (e.g., upgrading of fuel quality and the natural gas vehicle supply program) should have been the effective driving forces leading to the gradual reduction in CO levels in roadside locations (10 out of 16 stations) on the peninsula.     

Effects of pollutant concentration ratio on the simultaneous removal of NH3, H2S and toluene gases using rock wool-compost biofilter

The biological treatment of a tri-component mixed waste gas system in BRC1 and BRC2 biofilters packed with rock wool-compost media was studied. The model gases were NH(3), H(2)S and toluene. The gases were fed initially at about 50-55 ppm each. H(2)S was found to have the shortest start-up while toluene had the longest. Under two different NH(3):H(2)S:toluene concentration ratios of 250:120:55 and 120:220:55 (in ppm) for BRC1 and BRC2, the removal efficiencies of NH(3), H(2)S and toluene were found to be affected by their respective loading rate. On the other hand, toluene removal was observed to be inhibited at H(2)S concentration of 220 ppm as well. Almost complete removal of NH(3) and H(2)S was achieved when loading rate was applied up to 16.14 g-NH(3)/(m(3) bed h) and 36.09 g-H(2)S/(m(3) bed h), respectively. The maximum elimination capacity for NH(3) was determined to be 23.67 g-NH(3)/(m(3) bed h) at 78.6% removal efficiency and for H(2)S, 38.50 g-H(2)S/(m(3) bed h) at 68.1% removal efficiency. The maximum toluene elimination capacity was 30.75 g-toluene/(m(3) bed h) at 87.9% removal efficiency when the concentration of NH(3):H(2)S:toluene was 250:120:55 in BRC1, and was 16.60 g-toluene/(m(3) bed h) at 45.5% removal efficiency when the concentration of NH(3):H(2)S:toluene was 120:220:55 in BRC2. The pressure drops along both columns were low and the ratio of bed compactions over biofilter height was observed to be less than 0.02.     

Photocatalytic decomposition of acephate in irradiated TiO2 suspensions

In the present study, the photocatalytic degradation of acephate (O,S-dimethyl acetyl phosphoramidothioate ((CH(3)O)(CH(3)S)P(O)NHCOCH(3))) in aqueous TiO2 suspensions is extensively investigated, pertaining to the concentration of photocatalyst and substrate on degradation rate of acephate. It is found that the acephate can be degradated and mineralized. The high-degradation rate is obtained with 4 g/L concentration of TiO2. Moreover, Langmuir-Hinshelowood rate expression is employed for the degradation of acephate with adsorption constant and rate constant, i.e., 2.0 L/mmol and 0.6 mmol/(min L), respectively. The main target is to identify the products by a number of analytical techniques, such as HPLC, IC, ESR and GC-MS. Under acidic condition, the primary products are phosphorothioic acid, O,O',S-trimethyl ester (CH(3)O(CH(3)S)P(O)OCH(3)) and phosphoramidothioic acid, O,S-dimethyl ester (CH(3)O(CH(3)S)P(O)NH(2)), etc. It indicates that the decomposition of acephate begin from the destruction of C-N and P-N bonds. Subsequently, the P-S, P-O, P-C bonds may be oxidized gradually or simultaneously, and the final products such as CO(2), H(3)PO(4), were formed. About 100% sulfur atoms are transformed into SO(4)(2-) in 180 min, however; only 3% nitrogen atoms and 2% phosphorus atoms were transformed into NO(3)(-) and PO(4)(3-).     

The clathrate hydrate process for post and pre-combustion capture of carbon dioxide

One of the new approaches for capturing carbon dioxide from treated flue gases (post-combustion capture) is based on gas hydrate crystallization. The basis for the separation or capture of the CO(2) is the fact that the carbon dioxide content of gas hydrate crystals is different than that of the flue gas. When a gas mixture of CO(2) and H(2) forms gas hydrates the CO(2) prefers to partition in the hydrate phase. This provides the basis for the separation of CO(2) (pre-combustion capture) from a fuel gas (CO(2)/H(2)) mixture. The present study illustrates the concept and provides basic thermodynamic and kinetic data for conceptual process design. In addition, hybrid conceptual processes for pre and post-combustion capture based on hydrate formation coupled with membrane separation are presented.     

Verification of greenhouse gas emission reductions: the prospect of atmospheric monitoring in polluted areas

Independent verification of greenhouse gas emissions reporting is a legal requirement of the Kyoto Protocol, which has not yet been fully accomplished. Here, we show that dedicated long-term atmospheric measurements of greenhouse gases, such as carbon dioxide (CO(2)) and methane (CH(4)), continuously conducted at polluted sites can provide the necessary tool for this undertaking. From our measurements at the semi-polluted Heidelberg site in the upper Rhine Valley, we find that in the catchment area CH(4) emissions decreased on average by 32±6% from the second half of the 1990s until the first half of the 2000s, but the observed long-term trend of emissions is considerably smaller than that previously reported for southwest Germany. In contrast, regional fossil fuel CO(2) levels, estimated from high-precision (14)CO(2) observations, do not show any significant decreasing trend since 1986, in agreement with the reported emissions for this region. In order to provide accurate verification, these regional measurements would best be accompanied by adequate atmospheric transport modelling as required to precisely determine the relevant catchment area of the measurements. Furthermore, reliable reconciliation of reported emissions will only be possible if these are known at high spatial resolution in the catchment area of the observations. This information should principally be available in all countries that regularly report their greenhouse gas emissions to the United Nations Framework Convention on Climate Change.     

Assessment of radiological hazards of naturally occurring radioactive materials in cement industry

A study on the radiological hazard in Portland cement due to the presence of naturally occurring radioactive materials is being carried out. The Portland cement manufactured in the Islamabad/Rawalpindi region of Pakistan, intermediate products (clinker) and the various raw materials which compose the product have been analysed for (226)Ra, (232)Th and (40)K using a gamma spectrometry system with a N-type high-purity germanium detector of 80 % relative efficiency. From the measured gamma ray spectra, specific activities were determined. The mean values of the total specific activity of (226)Ra, (232)Th and (40)K are 34.2±11.9, 29.1±3.6 and 295.1±66.9 Bq kg(-1), respectively in Portland cement, 28.4±8.7, 11.3±1.7 and 63.1±17.3 Bq kg(-1), respectively in lime stone, 8.2±1.9, 16.2±3.9 and 187.7±53.2 Bq kg(-1), respectively in gypsum, 34.7±13.1, 41.2±6.7 and 187.6±17.2 Bq kg(-1), respectively in clay, 41.1±11.8, 39.3±6.9 and 195.1±29.2 Bq kg(-1), respectively in latrite and 51.1±18.2, 23.2±1.2 and 258.4±15.3 Bq kg(-1), respectively in clinker. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)), absorbed dose rate in air (D) and annual effective dose rate (E(eff)) were also determined. The measured activity concentrations for these radio nuclides and radiological indices were compared with the reported national and international data. All these measured values are comparable with the worldwide data reported in UNSCEAR publications.     

Measurements of NH(3) and CO(2) with Distributed-Feedback Diode Lasers Near 2.0 mum in Bioreactor Vent Gases

Measurements of NH(3) and CO(2) were made in bioreactor vent gases with distributed-feedback diode-laser sensors operating near 2 mum. Calculated spectra of NH(3) and CO(2) were used to determine the optimum transitions for interrogating with an absorption sensor. For ammonia, a strong and isolated absorption transition at 5016.977 cm(-1) was selected for trace gas monitoring. For CO(2), an isolated transition at 5007.787 cm(-1) was selected to measure widely varying concentrations [500 parts per million (ppm) to 10%], with sufficient signal for low mole fractions and without being optically thick for high mole fractions. Using direct absorption and a 36-m total path-length multipass flow-through cell, we achieved a minimum detectivity of 0.25 ppm for NH(3) and 40 ppm for CO(2). We report on the quasi-continuous field measurements of NH(3) and CO(2) concentration in bioreactor vent gases that were recorded at NASA Johnson Space Center with a portable and automated sensor system over a 45-h data collection window.     

Gas nanosensor design packages based on tungsten oxide: mesocages, hollow spheres, and nanowires

Achieving proper designs of nanosensors for highly sensitive and selective detection of toxic environmental gases is one of the crucial issues in the field of gas sensor technology, because such designs can lead to the enhancement of gas sensor performance and expansion of their applications. Different geometrical designs of porous tungsten oxide nanostructures, including the mesocages, hollow spheres and nanowires, are synthesized for toxic gas sensor applications. Nanosensor designs with small crystalline size, large specific surface area, and superior physical characteristics enable the highly sensitive and selective detection of low concentration (ppm levels), highly toxic NO(2) among CO, as well as volatile organic compound gases, such as acetone, benzene, and ethanol. The experimental results showed that the sensor response was not only dependent on the specific surface area, but also on the geometries and crystal size of materials. Among the designed nanosensors, the nanowires showed the highest sensitivity, followed by the mesocages and hollow spheres-despite the fact that mesocages had the largest specific surface area of 80.9?m(2)?g( - 1), followed by nanowires (69.4?m(2)?g( - 1)), and hollow spheres (6.5?m(2)?g( - 1)). The nanowire sensors had a moderate specific surface area (69.4?m(2)?g( - 1)) but they exhibited the highest sensitivity because of their small diameter (～5?nm), which approximates the Debye length of WO(3). This led to the depletion of the entire volume of the nanowires upon exposure to NO(2), resulting in an enormous increase in sensor resistance.     

Natural radioactivity levels of granites used in Turkey

Thirty granite samples commonly used in Turkey were surveyed for natural radioactivity. Concentrations of natural radionuclides in all samples were determined by gamma-ray spectroscopy with hyper-pure germanium detector. The activity concentrations measured for (226)Ra and (232)Th ranged from 0.7±0.1 to 186±1 Bq kg(-1), and from 0.5±0.1 to 249±2 Bq kg(-1), respectively. The activity concentrations obtained for (40)K varied from minimum detectable activity (0.4 Bq kg(-1)) to 1935±11 Bq kg(-1). The radium equivalent activity (Ra(eq)), the absorbed dose rate (D), the external hazard index (H(ex)) and the annual effective dose equivalent were also calculated and compared with the international recommended values. Granite samples were also analysed mineralogically. It was observed that the presence of large amount orthoclase and radiogenic accessory minerals are the sources of high activity concentration levels.     

Classification of jet fuel properties by near-infrared spectroscopy using fuzzy rule-building expert systems and support vector machines

Monitoring the changes of jet fuel physical properties is important because fuel used in high-performance aircraft must meet rigorous specifications. Near-infrared (NIR) spectroscopy is a fast method to characterize fuels. Because of the complexity of NIR spectral data, chemometric techniques are used to extract relevant information from spectral data to accurately classify physical properties of complex fuel samples. In this work, discrimination of fuel types and classification of flash point, freezing point, boiling point (10%, v/v), boiling point (50%, v/v), and boiling point (90%, v/v) of jet fuels (JP-5, JP-8, Jet A, and Jet A1) were investigated. Each physical property was divided into three classes, low, medium, and high ranges, using two evaluations with different class boundary definitions. The class boundaries function as the threshold to alarm when the fuel properties change. Optimal partial least squares discriminant analysis (oPLS-DA), fuzzy rule-building expert system (FuRES), and support vector machines (SVM) were used to build the calibration models between the NIR spectra and classes of physical property of jet fuels. OPLS-DA, FuRES, and SVM were compared with respect to prediction accuracy. The validation of the calibration model was conducted by applying bootstrap Latin partition (BLP), which gives a measure of precision. Prediction accuracy of 97 ± 2% of the flash point, 94 ± 2% of freezing point, 99 ± 1% of the boiling point (10%, v/v), 98 ± 2% of the boiling point (50%, v/v), and 96 ± 1% of the boiling point (90%, v/v) were obtained by FuRES in one boundaries definition. Both FuRES and SVM obtained statistically better prediction accuracy over those obtained by oPLS-DA. The results indicate that combined with chemometric classifiers NIR spectroscopy could be a fast method to monitor the changes of jet fuel physical properties.     

Raman and infrared spectroscopic investigations on aqueous alkali metal phosphate solutions and density functional theory calculations of phosphate-water clusters

Phosphate (PO(4)(3-)) solutions in water and heavy water have been studied by Raman and infrared spectroscopy over a broad concentration range (0.0091-5.280 mol/L) including a hydrate melt at 23 degrees C. In the low wavenumber range, spectra in R-format have been constructed and the R normalization procedure has been briefly discussed. The vibrational modes of the tetrahedral PO(4)(3-)(aq) (T(d) symmetry) have been assigned and compared to the calculated values derived from the density functional theory (DFT) method for the unhydrated PO(4)(3-)(T(d)) and phosphate-water clusters: PO(4)(3-).H(2)O (C(2v)), PO(4)(3-).2H(2)O (D(2d)), PO(4)(3-).4H(2)O (D(2d)), PO(4)(3-).6H(2)O (T(d)), and PO(4)(3-).12H(2)O (T), a cluster with a complete first hydration sphere of water molecules. A cluster with a second hydration sphere of 12 water molecules and 6 in the first sphere, PO(4)(3-).18H(2)O (T), has also been calculated. Agreement between measured and calculated vibrational modes is best in the case of the PO(4)(3-).12H(2)O cluster and the PO(4)(3-).18H(2)O cluster but far less so in the case of the unhydrated PO(4)(3-) or phosphate-water cluster with a lower number of water molecules than 12. The asymmetric, broad band shape of v(1)(a(1)) PO(4)(3-) in aqueous solutions has been measured as a function of concentration and the asymmetric and broad band shape was explained. However, the same mode in heavy water has only half the full width at half-height compared to the mode in normal water. The PO(4)(3-) is strongly hydrated in aqueous solutions. This has been verified by Raman spectroscopy comparing v(2)(H(2)O), the deformation mode of water, and the stretching modes, the v(1)OH and v(3)OH of water, in K(3)PO(4) solutions as a function of concentration and comparison with the same modes in pure water. A mode at approximately 240 cm(-1) (isotropic R spectrum) has been detected and assigned to the restricted translational mode of the strong hydrogen bonds formed between phosphate and water, P-O...HOH. In very concentrated K(3)PO(4) solutions (C(0) > or = 3.70 mol/L) and in the hydrate melt, formation of contact ion pairs (CIPs) could be detected. The phosphate in the CIPs shows a symmetry lowering of the T(d) symmetry to C(3v). In the less concentrated solutions, PO(4)(3-)(aq) solvent separated ion pairs and doubly solvent separated ion pairs exist, while in very dilute solutions fully hydrated ions are present (C(0) < or = 0.005 mol/L). Quantitative Raman measurements have been carried out to follow the hydrolysis of PO(4)(3-)(aq) over a very broad concentration range. From the hydrolysis data, the pK(3) value for H(3)PO(4) has been determined to be 12.45 at 23 degrees C.     

Measurement of natural radioactivity and assessment of associated radiation hazards in soil around Baoji second coal-fired thermal power plant, China

Activity concentrations of natural radionuclides (226)Ra, (232)Th and (40)K in soil around Baoji Second coal-fired thermal power plant of China were determined using gamma ray spectrometry. The mean activity concentrations of (226)Ra, (232)Th and (40)K in soil were found to be 40.3 ± 3.5, 59.6 ± 3.1 and 751.2 ± 12.4 Bq kg(-1), respectively, which are all higher than the corresponding average values in Shaanxi, Chinese and world soil. The radium equivalent activity (Ra(eq)), the air absorbed dose rate (D), the annual effective dose (E), the external hazard index (H(ex)) and internal hazard index (H(in)) were evaluated and compared with the internationally reported or reference values. All the soil samples have Ra(eq) lower than the limit of 370 Bq kg(-1) and H(ex) and H(in) less than unity. The overall mean outdoor terrestrial gamma air absorbed dose rate is ～86.6 ± 3.4 nGy h(-1) and the corresponding outdoor annual effective dose is 0.106 ± 0.004 mSv, which is higher than the worldwide average (0.07 mSv y(-1)) for outdoor's annual effective dose.