Naturally occurring radioactive material (NORM) from a former phosphoric acid processing plant

In recent years there has been an increasing awareness of the radiological impact of non-nuclear industries that extract and/or process ores and minerals containing naturally occurring radioactive material (NORM). These industrial activities may result in significant radioactive contamination of (by-) products, wastes and plant installations. In this study, scale samples were collected from a decommissioned phosphoric acid processing plant. To determine the nature and concentration of NORM retained in pipe-work and associated process plant, four main areas of the site were investigated: (1) the 'Green Acid Plant', where crude acid was concentrated; (2) the green acid storage tanks; (3) the Purified White Acid (PWA) plant, where inorganic impurities were removed; and (4) the solid waste, disposed of on-site as landfill. The scale samples predominantly comprise the following: fluorides (e.g. ralstonite); calcium sulphate (e.g. gypsum); and an assemblage of mixed fluorides and phosphates (e.g. iron fluoride hydrate, calcium phosphate), respectively. The radioactive inventory is dominated by U-238 and its decay chain products, and significant fractionation along the series occurs. Compared to the feedstock ore, elevated concentrations (<= 8.8 Bq/g) of U-238 Were found to be retained in installations where the process stream was rich in fluorides and phosphates. In addition, enriched levels (<= 11 Bq/g) of Ra-226 were found in association with precipitates of calcium sulphate. Water extraction tests indicate that many of the scales and waste contain significantly soluble materials and readily release radioactivity into solution. (c) 2005 Elsevier Ltd. All rights reserved.

Assessment of the effect of time and temperature on the availability of residual phosphate in a glasshouse study of four soils using the Olsen method

The Olsen method is an indicator of plant-available phosphorus (P). The effect of time and temperature on residual phosphate in soils was measured using the Olsen method in a pot experiment. Four soils were investigated: two from Pakistan and one each from England (calcareous) and Colombia (acidic). Two levels of residual phosphate were developed in each soil after addition of phosphate by incubation at either 10degreesC or 45degreesC. The amount of phosphate added was based on the P maximum of each soil, calculated using the Langmuir equation. Rvegrass was used as the test crop. The pooled data for the four soils incubated at 10degreesC showed good correlation between Olsen P and dry matter yield or P uptake (r(2) = 0.85 and 0.77, respectively), whereas at 45 degreesC, each soil had its own relationship and pooled data did not show correlation of Olsen P with dry matter yield or P uptake. When the data at both temperatures were pooled, Olsen P was a good indicator of yield and uptake for the English soil. For the Pakistani soils, Olsen P after 45 degreesC treatment was an underestimate relative to the 10 degreesC data and for the Colombian soil it was an overestimate. The reasons for these differences need to be explored further before high temperature incubation can be used to simulate long-term changes in the field.

The role of gypsum in the reactions of phosphate with soils

The aim of this study was to examine the mechanisms by which gypsum increases the sorption of fertilizer-P in soils of and and semi-arid regions. Either gypsum or soil (Usher from the UK; pH 7.8, 7% organic matter, 21% CaCO3: Yasouj from Iran; pH 8.2, 1.4% OM, 18% CaCO3: Ghanimeh from Saudi Arabia; pH 7.8, 1% OM, 26% CaCO3, 13% gypsum) was shaken for 24 It with KH2PO4 solutions in 10 mM CaCl2. With gypsum, grinding increased sorption by a factor of about 3, and increase in pH from 5.6 to 7.5 greatly increased sorption. Scanning electron micrographs (SEM) and EDX quantitative analysis showed that small crystals of gypsum disappeared and roughly spherical particles of dicalcium phosphate (DCPD) were formed. Analysis of equilibrium Solutions showed, using GEOCHEM, that octa-calcium phosphate (OCP) coated the DCPD. For the soils, sorption was in the order Ghanimeh > Yasouj > Usher. Removal of gypsum from Ghanimeh reduced sorption, with precipitated gypsum having a greater effect than gypsum mixed physically with the soil. Addition to Usher had no effect. SEM and EDX could not be used in the soil matrix, but solubility analysis again showed that solutions were close to equilibrium with OCP. Usher was unresponsive to added gypsum, presumably because of its small sorption capacity and high organic matter content. In Ghanimeh and Yasouj soils, gypsum increased sorption by being a source of readily available Ca2+ (c) 2005 Elsevier B.V. All rights reserved.

Arsenate-induced phosphate release from soils and its effect on plant phosphorus

Adsorption of arsenic onto soil was investigated as a means of understanding arsenic-induced release of phosphate. In batch adsorption experiments As adsorption was accompanied by P desorption. At low As additions, the ratio As adsorbed: P desorbed remained constant. At higher As additions, P desorption reached a maximum while As adsorption continued to increase. The P desorption maximum coincided with an increase in pH. Barley plants were grown on soils spiked with arsenate (0-360 mg As kg(-1)) to investigate the effect on plant growth and P uptake. As arsenic concentration increased, above ground plant yield decreased and the plants showed symptoms typical of As toxicity and P deficiency. At low As additions to the soil, uptake of As and P by barley increased. At higher As additions P uptake decreased. It is argued that this was due to the change in As:P ratio in the soil solution. It is concluded that input of arsenic to the soil could mobilise phosphate. Crop yield is likely to be affected, either due to reduced phosphate availability at low arsenic additions or arsenic toxicity at higher additions.

Factors influencing the dissolution of phosphate rock in a range of high P-fixing soils from Cameroon

A laboratory incubation experiment was conducted to evaluate the soil factors that influence the dissolution of two phosphate rocks (PRs) of different reactivity (Gafsa, GPR, reactive PR; and Togo-Hahotoe, HPR, low reactivity PR) in seven agricultural soils from Cameroon having variable phosphorus (P)- sorption capacities, organic carbon (C) contents, and exchangeable acidities. Ground PR was mixed with the soils at a rate of 500 mg P kg 21 soil and incubated at 30 degrees C for 85 days. Dissolution of the PRs was determined at various intervals using the Delta NaOH-P method ( the difference of the amount of P extracted by 0.5 M NaOH between the PR-treated soils and the control). Between 4 and 27% of HPR and 33 and 50% of GPR were dissolved in the soils. Calcium (Ca) saturation of cation exchange sites and proton supply strongly affected PR dissolution in these soils. Acid soils with pH-(H2O), < 5 (NKL, ODJ, NSM, MTF) dissolved more phosphate rock than those with pH-(H2O) > 5 (DSC, FGT, BAF). However, the lack of a sufficient Ca sink in the former constrained the dissolution of both PRs. The dissolution of GPR in the slightly acidic soils was limited by increase in Ca saturation and that of HPR was constrained by limited supply in protons. Generally, the dissolution of GPR was higher than that of HPR for each soil. The kinetics of dissolution of PR in the soils was best described by the power function equation P At B. More efficient use of PR in these soils can be achieved by raising the soil cation exchange capacity, thereby increasing the Ca sink size. This could be done by amending such soils with organic materials.

The calculation of force constants and normal co-ordinates II: methyl fluoride

The mathematical difficulties which can arise in the force constant refinement procedure for calculating force constants and normal co-ordinates are described and discussed. The method has been applied to the methyl fluoride molecule, using an electronic computer. The best values of the twelve force constants in the most general harmonic potential field were obtained to fit twenty-two independently observed experimental data, these being the six vibration frequencies, three Coriolis zeta constants and two centrifugal stretching constants DJ and DJK, for both CH3F and CD3F. The calculations have been repeated both with and without anharmonicity corrections to the vibration frequencies. All the experimental data were weighted according to the reliability of the observations, and the corresponding standard errors and correlation coefficients of the force constants have been deduced. The final force constants are discussed briefly, and compared with previous treatments, particularly with a recent Urey-Bradley treatment for this molecule.

The infra-red spectra of silyl fluoride and silyl fluoride-d3

Infra-red spectra have been recorded for silyl fluoride and silyl fluoride-d3 at a resolution of circa 0·3 cm-1. Rotational structure has been observed for parallel fundamentals in both molecules, and for all perpendicular fundamentals. In both SiH3F and SiD3F the A1 and E species deformation modes interact strongly via a Coriolis perturbation; this has been analysed, and the band origin of v5 for SiH3F is reassigned. A hybrid-orbital force field based on the experimental data is also reported.

The general harmonic force field of methyl fluoride

The complete general harmonic force field of methyl flouride was recalculated using the most recent literature frequency, Coriolis ζ, and centrifugal distortion data for 12CH3F, 13CH3F, 12CD3F, 12CHD2F and 12CH2DF. The anharmonic corrections applied to the observed frequency data and the adopted molecular geometry are considered to be more realistic than those used hitherto. There is excellent overall agreement between the fitted force constants and the highest quality ab initio force field currently available.

Isolation and partial characterisation of acid phosphatase isozymes from dormant oilseed of Corylus avellana L.

The acid phosphatase (orthophosphoric-monoester phosphohydrolase, EC 3.1.3.2) complement from dormant hazel (Corylus avellana L.) seeds was found to exhibit significant electrophoretic heterogeneity partially attributable to the presence of distinct molecular forms. In axiferous tissue, total acid phosphatase activity increased in a biphasic fashion during chilling, a treatment necessary to alleviate seed dormancy. Three acid phosphatase isozymes were isolated from cotyledons of dormant hazel seeds by successive ammonium sulphate precipitation, size-exclusion, Concanavalin A affinity, cation- and anion-exchange chromatographies resulting in 75-, 389- and 191-fold purification (APase1, APase2, APase3, respectively). The three glycosylated isoforms were isolated to catalytic homogeneity as determined by electrophoretic, kinetic and heat-inactivation studies. The native acid phosphatase complement of hazel seeds had an apparent Mr of 81.5±3.5 kDa as estimated by size-exclusion chromatography, while the determined pI values were 5.1 (APase1), 6.9 (APase2) and 7.3 (APase3). The optimum pH for p-nitrophenyl phosphate hydrolysis was pH 3 (APase1), pH 5.6 (APase2) and pH 6 (APase3). The hazel isozymes hydrolysed a variety of phosphorylated substrates in a non-specific manner, exhibiting low Km and the highest specificity constant (Vmax/Km) for pyrophosphate. They were not primary phytases since they could not initiate phytic acid hydrolysis, while APase2 and APase3 had significant phospho-tyrosine phosphatase activity. Inorganic phosphate was a competitive inhibitor, while activity was significantly impaired in the presence of vanadate and fluoride.

Isolation and characterisation of phytase from dormant Corylus avellana seeds

Phytase (myo-inositol-1,2,3,4,5,6-hexakisphosphate phosphohydrolase, EC 3.1.3.26), which catalyses the step-wise hydrolysis of phytic acid, was purified from cotyledons of dormant Corylus avellana L. seeds. The enzyme was separated from the major soluble acid phosphatase by successive (NH4)2SO4 precipitation, gel filtration and cation exchange chromatography resulting in a 300-fold purification and yield of 7.5%. The native enzyme positively interacted with Concanavalin A suggesting that it is putatively glycosylated. After size exclusion chromatography and SDS–PAGE it was found to be a monomeric protein with molecular mass 72±2.5 kDa. The hazel enzyme exhibited optimum activity for phytic acid hydrolysis at pH 5 and, like other phytases, had broad substrate specificity. It exhibited the lowest Km (162 μM) and highest specificity constant (Vmax/Km) for phytic acid, indicating that this is the preferred in vivo substrate. It required no metal ion as a co-factor, while inorganic phosphate and fluoride competitively inhibited enzymic activity (Ki=407 μM and Ki=205 μM, respectively).

Potassium nickel(II) gallium phosphate hydrate, K[NiGa2(PO4)(3)(H2O)(2)]

The title compound, potassium nickel(II) digallium tris-( phosphate) dihydrate, K[NiGa2(PO4)(3)(H2O)(2)], was synthesized hydrothermally. The structure is constructed from distorted trans-NiO4(H2O)2 octahedra linked through vertices and edges to GaO5 trigonal bipyramids and PO4 tetrahedra, forming a three-dimensional framework of formula [NiGa2(PO4)(3)(H2O)(2)](-). The K, Ni and one P atom lie on special positions (Wyckoff position 4e, site symmetry 2). There are two sets of channels within the framework, one running parallel to the [10 (1) over bar] direction and the other parallel to [001]. These intersect, forming a three-dimensional pore network in which the water molecules coordinated to the Ni atoms and the K+ ions required to charge balance the framework reside. The K+ ions lie in a highly distorted environment surrounded by ten O atoms, six of which are closer than 3.1 angstrom. The coordinated water molecules are within hydrogen-bonding distance to O atoms of bridging Ga-O-P groups.