Po In Water Research Articles

Natural radioactivity in tap waters from the private wells in the surroundings of the former Žirovski Vrh uranium mine and the age-dependent dose assessment.

Activity concentration of (238)U, (234)U, (226)Ra, (228)Ra, (210)Pb and (210)Po in tap water from selected springs and private wells in the area of the former uranium mine at Žirovski Vrh were determined. A total of 22 tap water samples were collected at consumer's houses. The results show that the activity concentrations of uranium in water samples are in range (0.17-372) and (0.22-362) mBq L(-1) for (238)U and (234)U, respectively. Radium activity concentrations are in range (0.14-16.7) and (0.9-11.7) mBq L(-1) for (226)Ra and (228)Ra, respectively. (210)Po activity concentration is in range (0.28-8.0) mBq L(-1) and can be regarded as the lowest amongst all analysed radionuclides. The range for (210)Pb is (0.5-24.6) mBq L(-1). Based on the results obtained for activity concentrations of six radionuclides, the committed effective dose for three different age groups of population were estimated. It was found that the committed effective dose was well below the recommended value of 100 μSv year(-1), ranging from 2.3 to 34.3 μSv year(-1) for adults, from 3.5 to 32.0 μSv year(-1) for children (7-12 years) and from 3.0 to 23.3 μSv year(-1) for infants.

Quantum-Mechanical Study on the Aquaions and Hydrolyzed Species of Po(IV), Te(IV), and Bi(III) in Water

A systematic study of [M(H(2)O)(n)(OH)(m)](q+) complexes of Te(IV) and Bi(III) in solution has been undertaken by means of quantum mechanical calculations. The results have been compared with previous information obtained for the same type of Po(IV) complexes ( J. Phys. Chem. B 2009 , 113 , 487 ) to get insight into the similarities and differences among them from a theoretical view. The evolution of the coordination number (n + m) with the degree of hydrolysis (m) for the stable species shows a systematic decrease regardless the ion. A general behavior on the M-O distances when passing from the gas phase to solution, represented by the polarizable continuum model (PCM), is also observed: R(M-O) values corresponding to water molecules decrease, while those of the hydroxyl groups slightly increase. The hydration numbers of aquaions are between 8 and 9 for the three cations, whereas hydrolyzed species behave differently for Te(IV) and Po(IV) than for Bi(III), which shows a stronger trend to dehydrate with the hydrolysis. On the basis of the semicontinuum solvation model, the hydration Gibbs energies are -800 (exptl -834 kcal/mol), -1580 and -1490 kcal/mol for Bi(III), Te(IV), and Po(IV), respectively. Wave function analysis of M-O and O-H bonds along the complexes has been carried out by means of quantum theory of atoms in molecule (QTAIM). Values of electron density and its Laplacian at bond critical points show different behaviors among the cations in aquaions. An interesting conclusion of the QTAIM analysis is that the prospection of the water O-H bond is more sensitive than the M-O bond to the ion interaction. A global comparison of cation properties in solution supplies a picture where the Po(IV) behavior is between those of Te(IV) and Bi(III), but closer to the first one.

An Ab Initio Molecular Dynamics Study on the Hydrolysis of the Po(IV) Aquaion in Water

Po(IV) in water has been studied by means of Car-Parrinello molecular dynamics (CPMD) simulations. A new Trouiller-Martins pseudopotential for Po(IV) has been developed. This pseudopotential was tested by comparing the structure and energetics of small [Po(H(2)O)(n)(OH)(m)](4-m) clusters optimized quantum-mechanically. CP-MD simulations of 1 Po + 60 H(2)O were carried out starting from three different degrees of hydrolysis of the aquaion (m = 0, 2, and 3), in order to check the stability of the hydrolyzed forms under the simulation conditions. The three simulations converge to a description of the solution where the same hydrolyzed species are present. Dynamics of the octahydrate aquaion in water indicates that dehydration couples to hydrolysis processes, and the total coordination number decreases with the hydrolysis degree. The time evolution of the initial [Po(H(2)O)(8)](4+) aquaion in aqueous solution indicates that hydrolysis precedes to dehydration in the process from aquaion to hydroxoaquaion. Structural and dynamical properties of the ligands in the first coordination shell are analyzed. The power spectra and its contribution from fragments of the first coordination shell are also examined.

210Po accumulation by components of the Black Sea ecosystem

The naturally occurring radionuclide 210 Po was determined in different components of the Black Sea ecosystem. The specific activity of 210 Po in water in the open part of the sea was about 1Bq ⋅ m-3 . The range of 210 Po specific activity in bottom sediments was 4.5–500 Bq ⋅ kg-1 dry weight depending on their type, area and depth of collection. The highest values were found in the NW part of the Black Sea. Sediment distribution coefficients (Kd) of 210 Po for bottom sediments, calculated on a dry weight basis, varied from 0.5 × 104 to 5 × 105 . The levels of 210 Po specific activity in molluscs and pelagic fishes anchovy and sprat were the highest among the investigated species of the Black Sea biota. Concentration factors (CF) of 210 Po, estimated on a wet weight basis, reached 1.5 × 103 for macrophytes, 4 × 103 for total zooplankton, 103 –104 for the entire fishes depending on their ecological groups affiliation and (0.7–6.0) × 104 for molluscs. So, the ability of the Black Sea biota to accumulate the natural radionuclide 210 Po is comparable with that of similar species from others marine and oceanic areas.

General Quantum-Mechanical Study on the Hydrolysis Equilibria for a Tetravalent Aquaion: The Extreme Case of the Po(IV) in Water

A systematic study of the different hydrolyzed species derived from the hydrated Po(IV) in water, [Po(H(2)O)(n)(OH)(m)]((4-m)) for 1 m 4, and 4 m + n 9, has been carried out by means of quantum mechanical computations. The effects of outer solvation shells have been included using a polarizable continuum dielectric model. For a fixed number of hydroxyl groups, the preferred hydration number for the Po(IV) can be determined in terms of Gibbs energy. It is shown that the hydration number (n) systematically decreases with the increase in the number of hydroxyl groups (m) in such a way the total coordination number (n + m) becomes smaller, being 9 in the aquocomplex and 4 in the neutral hydroxo-complex. Free energies for the hydrolysis processes involving Po(IV) complexes and a different number of hydroxyl groups have been computed, revealing the strong tendency toward hydrolysis exhibited by these complexes. The predominant species of Po(IV) in aqueous solutions are ruled by a dynamical equilibrium involving aggregates containing in the first coordination shell OH(-) groups and water molecules. Although there is not experimental information to check the theoretical predictions, theoretical computations in solution seem to suggest that the most likely clusters are [Po(H(2)O)(5)(OH)(2)](2+) and [Po(H(2)O)(4)(OH)(2)](2+). The geometry of the different clusters is ruled by the trend of hydroxyl groups to be mutually orthogonal and to promote a strong perturbation of the water molecule in trans-position by lengthening the Po-H(2)O distances and tilting the corresponding bond angle. A general thermodynamic cycle is defined to compute the Gibbs free energy associated to the formation of the different hydrolyzed forms in solution. From it, the estimates of pK(a) values associated to the different protolytic equilibria are provided and discussed. Comparison of the relative values of pK(a) along a hydrolysis series with the experimental values for other tetravalent cations supports its consistency.

Determination of gentamicin in pharmaceutical formulations using peroxyoxalate chemiluminescent detection in flow-injection analysis

A simple and sensitive procedure for the determination of gentamicin is presented, based on the use of the peroxyoxalate chemiluminescent (PO-CL) system in presence of imidazole as a catalyst. The gentamicin has to be previously derivatized with o-phthaladehyde (OPA) in order to obtain a fluorophore, which participates in the PO reaction, producing a CL emission proportional to the gentamicin concentration. The method is developed by using a particular flow-injection analysis (FIA) manifold, employing sodium dodecyl sulfate (SDS) micellar medium as a carrier in order to avoid the degradation of PO in water. The optimization of the instrumental and chemical variables affecting the CL reaction was rigorously carried out by using experimental design methodology. The method has been successfully applied to pharmaceutical formulations.

Determination of a N-methylcarbamate pesticide in environmental samples based on the application of photodecomposition and peroxyoxalate chemiluminescent detection

A new sensitive analytical procedure for the determination of a N-methylcarbamate pesticide (carbaryl) is presented, based on the participation of a fluorescent derivative of the pesticide in the peroxyoxalate chemiluminescent (PO–CL) system using imidazole as a catalyst. The chemiluminescent emission is detected in a flow injection (FI) manifold, employing sodium dodecyl sulfate micellar medium as carrier, which avoids the rapid degradation of a PO in water. The formation of the fluorescent derivative implies the previous decomposition of carbaryl to methylamine (MA) by UV irradiation and subsequent derivatisation with o-phthalaldehyde (OPA), carried out off-line. Photodecomposition allows a rapid degradation of carbaryl in MA, which implies some advantages in relation to the traditional hydrolysis in alkaline medium, such shorter analysis time and easier application. The optimisation of the operational and chemical variables affecting the CL response was carried out by using experimental design strategies. The method has been successfully applied to different natural waters and vegetal sample, obtaining satisfactory recoveries in both cases, with detection limits in compliance with the maximum limit of residues (MLR) permitted.

Uranium and its decay products in samples contaminated with uranium mine and mill waste

The routine determination of the activity concentrations of uranium isotopes ( 238 U, 235 U and 234 U), thorium isotopes ( 232 Th, 230 Th and 228 Th), 231 Pa, 226 Ra, 210 Pb and 210 Po in the environment is one of the most important tasks in uranium mining areas. Natural radionuclides contribute negligibly to the external radiation dose, but in the case of ingestion or inhalation can represent a very serious hazard. The objective of this study was to determine the activities of uranium and its decay products 230 Th, 231 Pa, 226 Ra, 210 Pb and 210 Po in sediments and water below sources of contamination (uranium mine, disposal sites and individual inflows) using gamma and alpha spectrometry, beta counting, the liquid scintillation technique and radiochemical neutron activation analysis.

Components of organic phosphorus in soil extracts that are hydrolysed by phytase and acid phosphatase

Extracts were prepared from soil using water, 50 mM citric acid (pH ∼2.3) or 0.5 M NaHCO3 (pH 8.5), and were incubated with excess phytase from Aspergillus niger to determine the amounts of labile P. Two A. niger phytase preparations were used: (1) a purified form which exhibited a narrow substrate specificity and high specific activity against phytate; and (2) a commercial preparation (Sigma) with activity against a broad range of P compounds. A comparatively large proportion (up to 79%, or 5.7 μg g–1 soil) of the organic P (Po) extracted with citric acid was hydrolysed by the commercial phytase, while between 28% and 40% (up to 3.1 μg g–1 soil) was hydrolysed using purified phytase. By comparison, only small quantities of the Po in water and NaHCO3 soil extracts were enzyme labile. While extractable Po was increased both with increasing concentrations of citric acid (up to 50 mM) and increasing pH (pH 2.3–6.0), enzyme-labile P increased only with citric acid concentration. The labile component of Po in citric acid extracts from soils with contrasting fertiliser histories indicated that enzyme-labile Po is a relatively large soil P pool and is potentially an important source of P for plants.

Evaluation of the Developmental Toxicity of Methacrylamide and N,N′-Methylenebisacrylamide in Swiss Mice

Timed-pregnant CD-1 outbred albino Swiss mice received either methacrylamlde (MAC; 0, 60, 120, or 180 mg/kg/day) or N,N′-methylenebisacrylamide (BAC; 0, 3, 10, or 30 mg/kg/day) po in distilled water on gestational days (GD) 6 through 17. Maternal clinical status was monitored daily. At termination (GD 17), confirmed-pregnant females (27–30 per group, MAC; 24–25 per group, BAC) were evaluated for clinical status and gestational outcome; live fetuses were examined for external, visceral, and skeletal malformations. For MAC, no treatment-related maternal mortality was observed. Maternal body weight on GD 17, maternal weight gain during treatment and gestation, and corrected maternal weight gain were reduced at the high dose. Relative maternal food and water intake was not adversely affected; neurotoxicity was not observed. Relative maternal liver weight was increased at a 120 mg/kg/day; gravid uterine weight was decreased at 180 mg/kg/day. The maternal no-observed adverse effect level (NOAEL) was 60 mg/kg/day. The NOAEL for developmental toxicity was also 60 mg/kg/day. At ≥ 120 mg/kg/day, mean fetal body weight was reduced. At 180 mg/kg/day, increased postimplantation death per litter was observed. Morphological development was not affected. The maternal NOAEL for BAC was 10 mg/kg/day. At 30 mg/kg/day, decreased maternal body weight on GD 17, maternal body weight change during treatment and gestation, corrected maternal body weight, and gravid uterine weight were observed. Relative maternal liver weight increased at 30 mg/kg/day. The developmental NOAEL was 3 mg/kg/day BAC. Mean fetal body weight was reduced at 30 mg/kg/day. At ≥ 10 mg/kg/day, an increased incidence of fetal variations (extra rib) was observed, although fetal malformation rate was unaffected. MAC and BAC were not teratogenic to Swiss mice at the doses tested. BAC was more potent than MAC in causing adverse maternal and developmental effects.

226Ra, 210Pb, 210Po Distributions at the Sea off Southern Taiwan: Radioactive Disequilibria and Temporal Variations

(superscript 210)Pb and (superscript 210)Po in both particulate and dissolved phases were measured at the sea off southern Taiwan, where the Kuroshio intrudes as a branch in winter and mixes with the South China Sea water and coastal waters. Although the effects of mixing and circulation, based on hydrographic data, were significant, the removal rates of these two nuclides due to scavenging by sinking particles were evaluated. Dissolved and total (superscript 210)Pb and (superscript 210)Po in surface water increased but particulate (superscript 210)Pb decreased away from the coast in September, 1994, as well as in January, 1995. On the other hand, both particulate and dissolved (superscript 210)Po in surface water varied temporally and were higher in January, 1995. The mean residence time calculated for the surface water (superscript 210)Pb with respect to particulate scavenging was generally longer in January, 1995 (0.57-0.71 yr) than in September, 1994 (0.25-0.41 yr) if a constant atmospheric flux of 2 dpinlcm^2/y in the area was assumed. Similarly, for (superscript 210) Po it was also longer in January, 1995 (0.56-7.7 yr) than in September, 1994 (0.23-2.0 yr). The (superscript 210)Pb and (superscript 210)Po profiles measured from three stations in different periods showed that their concentrations varied temporally and spatially, therefore probably reflecting changes in hydrography and particulate scavenging. In the upper layer where (superscript 210)Pb was in excess of (superscript 226) Ra, the mean residence time for (superscript 210) Pb with respect to the removal by sinking particulates was about 1.3-3 yrs. In the lower layer where (superscript 210)Pb was deficient relative to (superscript 226)Ra, the mean residence time ranged from 26 to 44 yrs resulting from variations in (superscript 210)Pb and (superscript 226)Ra inventories or varying (superscript 210)Pb deficits. The mean residence time calculated for (superscript 210)Po in the upper, intermediate and lower layers as defined by (superscript 210)Po deficit or excess relative to (superscript 210)Pb also varied in the three sampling periods. These variations were due to the fact that both (superscript 210)Po and (superscript 210)Pb profiles varied in response to particulate scavenging and the mixing of several water masses in variable proportions at different times. (superscript 210)Pb was not recycled, but at two stations in January, 1995, (superscript210)Po was recycled over 100%, requiring a lateral input. This feature was also observed at the sea off northeastern Taiwan.

Anion Coordination Chemistry: Polyguanidinium Salts as Anion Complexones

AbstractThe synthesis of a series of polyguanidinium salts of potential interest as anion complexones is described. Among the various synthetic methods investigated, the polyguanidinium salts were found to be most conveniently prepared from polyamines via polynitroguanidine intermediates. The complexation of phosphate and carboxylate anions by these complexones and by related polyammonium salts were studied by analysis of pH‐metric titration data. The ligands studied from relatively stable complexes (log Ks = 2.0–4.0 for PO in water) which also present good selectivities in some cases. Both the stability and the selectivity of complexation are primarily governed by electrostatic forces and thus depend on charge accumulation in the interacting species; structural effects are also observed. Since the binding is primarily electrostatic, polyammonium salts from more stable complexes (at a given charge) than do polyguanidinium salts. However, whereas the complexation properties of the latter are independent of pH, the complexes of the former are observed only in the limited ranges of pH where both the protonated polyamine and the anion of interest can coexist. The polycationic ligands may, in principle, form chelate type anion complexes. Comparison with the corresponding single binding sites reveals an increase in complexation constant of about two or three orders of magnitude; this may be considered as a thermodynamic indication of a chelate effect for the polydentate ligands (by analogy with the well known effects displayed by cation complexones); however, structural data on the formation of chelate ‘rings’ are not yet available. The nature of the complexes and the prospects of anion complexones in various fields are discussed.