A liquid-scintillation-based primary standardization of Pb

A new radioactivity solution standard of ²¹⁰Pb has been developed and will be disseminated by the National Institute of Standards and Technology (NIST) as standard reference material (SRM) 4337. This new ²¹⁰Pb solution standard is contained in a 5 mL flame-sealed borosilicate glass ampoule, consists of (5.133±0.002) g of a nominal 1 mol L⁻¹ nitric acid solution, has a density of (1.028±0.002) g mL⁻¹ at 20 °C, has carrier ion concentrations of about 11 μg Pb²⁺ and 21 μg Bi³⁺ per gram of solution, and is certified to contain a massic activity (9.037±0.22) kBq g⁻¹ as of the reference time 1200 EST, 15 June 2006. All of the uncertainties cited above correspond to standard uncertainties multiplied by a coverage factor k=2. The standardization for the ²¹⁰Pb content of the solution was based on 4πβ liquid scintillation (LS) measurements using CIEMAT/NIST ³H-standard efficiency tracing (CNET). Confirmatory determinations were also performed by high-resolution HPGe γ-ray spectrometry, by 2π spectrometry with a Si surface barrier detector of separated ²¹⁰Po, and by 4πβ(LS)–γ(NaI) anticoincidence counting.     

The effect of contrast temperature water therapy on repeated sprint performance

The aim of this study was to compare the effectiveness of two recovery techniques on blood lactate and repeated sprint performance. In a randomised cross-over design 20 junior representative rugby players (aged 19 ± 1 years) were given either contrast temperature water therapy or active recovery after performing a repeated sprint test. The test was then repeated 1 h later to gauge the effects of the two recovery methods on subsequent repetitive sprinting performance. One week later, the two groups were reversed and the testing repeated. The test consisted of ten 40-m sprints with a 30-s turn-around between sprints. Recovery consisted of 6 min slow jogging (6.8 km h⁻¹) for the active recovery group or 6 min of contrast temperature water therapy consisting of three 1-min hip-height immersions in cold water (8–10 °C) alternated with three 1-min hot water (38 °C) showers. Blood lactate concentration and heart rates were measured throughout the testing. Relative to the active recovery group the contrast temperature water therapy group showed a substantial decrease in blood lactate concentration 3 min after the procedure (−2.1 mmol L⁻¹, 95% confidence limits, ±1.8 mmol L⁻¹), and substantially lower heart rates both during the procedure (−9.1 ± 8.7 min⁻¹) as well as 1 h later during the second set of sprints (−11.7 ± 8.6 min⁻¹). Effects of recovery group on repeated sprint performance were small to trivial and unclear. Compared to active recovery, contrast temperature water therapy decreases blood lactate concentration and heart rate but has little effect on subsequent repetitive sprinting performance.     

Indoor gamma dose measurements in Gudalore (India) using TLD

Indoor gamma radiation dose rates were measured inside residential buildings in Gudalore using a CaSO₄ : Dy thermoluminescent dosimeter for 1 year . Significant seasonal variations are observed. The highest dose rate is observed during summer and the lowest in winter. The dose rates observed are between 77.9 and 229.3 nGy h⁻¹ and may be attributed to the type of building materials used in the dwellings monitored. The calculated mean annual effective dose equivalent rates range between 477.6 μSv y⁻¹, for the inhabitants of mud houses to 1406.3 μSv y⁻¹, for those living in terrace houses made of cement and brick.     

An audit of clinically relevant abnormal laboratory parameters investigating athletes with persistent symptoms of fatigue

The aim of this audit was to assess the yield of a selection of laboratory tests as part of the clinical assessment of the fatigued athlete. Clinical charts and blood test results of fifty consecutive athletes who presented with the primary complaint of fatigue were retrospectively reviewed. Blood tests results reviewed were: haematology (haemoglobin, red cell count, mean cell volume, mean cell haemoglobin content, platelets, white cell count, differential white cell count); erythrocyte sedimentation rate; serum biochemistry (urea, creatinine, electrolytes, urate, glucose, liver function tests, albumin, globulin); blood iron status (serum iron, total iron binding capacity, percent transferring saturation, and ferritin concentration); thyroid stimulating hormone; and immune measures (Epstein–Barr virus serology, cytomegalovirus serology). We identified only 3 abnormal results that contributed to the diagnosis of medical disease as a cause for fatigue. Laboratory testing identified 2 fatigued female athletes with serum ferritin concentration between 15 μg L⁻¹ and 20 μg L⁻¹ plus two of the other criteria of iron concentration (serum iron <10 μmol L⁻¹, iron binding capacity >68 μmol L⁻¹, or transferrin saturation <15%). We concluded that the yield from a selection of blood tests investigating fatigued athletes was low. Future study is needed to further define the role of laboratory testing and to study whether low iron stores in the absence of anaemia is related to symptoms in fatigued athletes.     

Contrast water immersion hastens plasma lactate decrease after intense anaerobic exercise

The benefits of rapid recovery after intense exercise are widely recognised, and lactate elimination is one indicator of recovery rate. This study examined the effect of contrast (alternating hot and cold) water immersion (CWI) on the rate of plasma lactate decrease during recovery after intense anaerobic exercise. Eleven subjects on each of two occasions undertook four successive 30-s Wingate tests separated by 30-s rest periods. On each occasion, plasma lactate concentration during recovery was measured 5 min post-exercise and thereafter at 5 min intervals for 30 min. On one occasion (determined randomly), the subjects recovered passively (PR) on a recovery bed and, on the other, they alternated partial body immersion in hot (36 °C) and cold (12 °C) water baths. Plasma lactate concentrations were analysed by repeated measures analysis of variance and by fitting a linear regression model, allowing for both gender and recovery mode differences. The rate of decrease in plasma lactate concentration over the 30-min recovery period was significantly higher (p < 0.001) in CWI; 0.28(±0.02) mmol L⁻¹ min⁻¹ (CWI) compared to 0.22(±0.02) mmol L⁻¹ min⁻¹ (PR). These values do not differ significantly between males and females. Contrast water immersion is a valid method of hastening plasma lactate decrease during recovery after intense anaerobic exercise for both males and females. An approximately 1.8 mmol L⁻¹ difference between the two conditions may be expected after 30 min. With differences among elite competitors as little as 1–2%, this reduction may be of practical significance.     

Radiochemical purification of no-carrier-added scandium-47 for radioimmunotherapy

A procedure, adaptable to large-scale remote operation, was developed to purify no-carrier-added (NCA) ⁴⁷Sc from irradiated Ti targets. Methods based on extraction chromatography and cation-exchange chromatography were compared. Results of this comparison led to the development of an optimized procedure based on cation-exchange with Dowex AG 50W-X4 and ⁴⁷Sc elution with HCl/HF. This method gave 90–97% overall ⁴⁷Sc recovery, with a Ti separation factor greater than 2.4×10⁻⁵, and specific activities ≥0.9 GBq μg⁻¹. Use of the ⁴⁷Sc product, for labeling monoclonal antibodies, resulted in consistent labeling yields of ≥90%.     

Measurement of Pu γ-ray intensities between 148 and 161 keV

Utilizing Pu isotopic standards characterized by the Institute for Nuclear Materials and Measurement (IRMM), New Brunswick Laboratory (NBL) measured the γ-ray branching ratios of the 148.567-keV ²⁴¹Pu, the 152.72-keV ²³⁸Pu, the 159.995-keV ²⁴¹Pu and the 160.28-keV ²⁴⁰Pu γ-rays. The study reported here includes the measurement of four IRMM standards, utilizing three different detectors for a total of 16 spectra, finding branching ratios of (1.863 ± 0.008) × 10⁻⁶, (9.230 ± 0.068) × 10⁻⁶, (6.321 ± 0.040) × 10⁻⁸ and (4.065 ± 0.017) × 10⁻⁶, γ/disintegration, respectively.     

Development and application of Marinelli beaker standards for monitoring radioactivity in Dairy-Products by gamma-ray spectrometry

Marinelli (reentrant) beakers are recommended for measurement of low-activity radioactive environmental samples, in both liquid and solid phase.

The preparation of Marinelli beaker standards of milk powder containing ²³²ThO₂ at secular equilibrium with its daughter radionuclides was studied. Standards were prepared by mixing of known amounts of solid ThO₂ and milk powder. The densities of the standards were 0.5–0.7 kg dm⁻³.

Measurements of calibrated Marinelli beaker standards with HPGe detector showed that the energy dependence of the efficiency is similar to that of a point source, i.e. an almost linear dependence of log-efficiency vs. log-energy in the 200–2000 keV range, however the parabolic correlation fits better.

The validity of these standards was checked by comparison with certified standard reference material IAEA-152-Milk powder containing radiocesium and radiopotassium. The results obtained were found to be in a good agreement with the published certified data.

The limit of detection for the determination of radiocesium by gamma ray spectrometry under the prevailing experimental conditions is 0.03 Bq (i.e. 0.8 pCi), for samples of dairy products having lower densities of 0.7 kg dm⁻¹.     

Effect of pH and concentration on the diffusion of radiostrontium in compacted bentonite—a capillary experimental study

The effects of pH and Sr²⁺ solution concentration on diffusion and sorption of Sr²⁺ in compacted bentonite (ρ_b=1000±30 kg/m³) were studied using an “in-diffusion” method at an ionic strength of 0.1 M NaClO₄. The results (distribution coefficients, K_d, apparent and effective diffusion coefficients, D_a and D_e) derived from the capillary method are in good agreement with the literature data obtained for similar bentonite dry densities and fit Fick's second law very well. The results suggest that the diffusion of Sr²⁺ in compacted bentonite decreases slightly with increasing pH values and also increases slightly with increasing Sr²⁺ solution concentration. The distribution coefficients are weakly dependent on the solution concentrations and show a slight increase with increasing pH values. The average effective diffusion coefficient of Sr²⁺ in compacted bentonite is (1.2±0.2)×10⁻⁹ m²/s, surface diffusion effects are found for the diffusion of Sr²⁺ in compacted bentonite.     

Decomposition of aqueous solutions of phenol using high energy electron beam irradiation—A large scale study

High-energy electron-beam irradiation was used to remove phenol from aqueous solution. The variables that affected phenol decomposition were solute concentration, absorbed dose and total alkalinity. Experiments were conducted at large scale (480 L min⁻¹), at solute concentrations of 10.6, 106 and 531 μmol L⁻¹ (1, 10 and 50 mg L⁻¹) over the pH range 5–9, and in the presence and absence of solids (3% w/w kaolin clay). Absorbed doses ranged from 0–7 kGy (0–700 krad). At low absorbed doses, catechol, hydroquinone and resorcinol were identified as the major reaction byproducts. These compounds are consistent with hydroxyl radical (OH·) addition to phenol. Subsequent ring cleavage of hydroxylated phenolic radicals and continued oxidative processes resulted in the formation of formaldehyde, acetaldehyde, glyoxal and formic acid. At high doses only trace amounts of the carbonyl derivatives were observed. Two recirculation experiments were conducted at higher phenol concentrations (≈950 μmol L⁻¹) and it was shown that phenol was removed while the total organic carbon of the solution decreased only slightly. These results suggest that phenol was not mineralized but, rather, that irradiation resulted in the possible formation of higher molecular weight polymers.     

A Monte Carlo brachytherapy study for dose distribution prediction in an inhomogeneous medium

The purpose of this study was to present a theoretical analysis of how the presence of bone in interstitial brachytherapy affects dose rate distributions. This study was carried out using a Monte Carlo simulation of the dose distribution in homogeneous medium for 3 commonly used brachytherapy seeds. The 3 seeds investigated in this study are iridium-192 (¹⁹²Ir) iodine-125 (¹²⁵I), and palladium-103 (¹⁰³Pd). The computer code was validated by comparing the specific dose rate (Λ), the radial dose function g(r), and anisotropy function F(r,θ) for all 3 seeds with the AAPM TG-43 dosimetry formalism and current literature. The ¹⁹²Ir seed resulted in a dose rate of 1.115 ± 0.001 cGy-hr⁻¹-U⁻¹, the ¹²⁵I seed resulted in a dose rate of 0.965 ± 0.006 cGy/h⁻¹/U⁻¹, and the ¹⁰³Pd seed resulted in a dose rate of 0.671 ± 0.002 cGy/h⁻¹/U⁻¹. The results for all 3 seeds are in good agreement with the AAPM TG-43 and current literature. The validated computer code was then applied to a simple inhomogeneous model to determine the effect bone has on dose distribution from an interstitial implant. The inhomogeneous model showed a decrease in dose rate of 2% for the ¹⁹²Ir, an increase in dose rate of 84% for ¹²⁵I, and an increase in dose rate of 83% for the ¹⁰³Pd at the surface of the bone nearest to the source.     

Influence of exercise mode and maximal lactate-steady-state concentration on the validity of OBLA to predict maximal lactate-steady-state in active individuals

The aim of this study was to analyze the effects of exercise mode on the validity of onset of blood lactate accumulation (OBLA—3.5-mM fixed blood lactate concentration) to predict the work-rate at maximal lactate steady state (MLSS_work-rate). Eleven recreationally active males (21.3 ± 2.9 years, 72.8 ± 6.7 kg, 1.78 ± 0.1 m) performed randomly incremental tests to determine OBLA (stage duration of 3 min), and 2 to 4 constants work-rate exercise tests to directly determine maximal lactate steady state parameters on a cycle-ergometer and treadmill. For both exercise modes, the OBLA was significantly correlated to MLSS_work-rate, (cycling: r = 0.81 p = 0.002; running: r = 0.94, p < 0.001). OBLA (156.2 ± 41.3 W) was lower than MLSS_work-rate (179.6 ± 26.4 W) during cycling exercise (p = 0.007). However, for running exercise, there was no difference between OBLA (3.2 ± 0.6 m s⁻¹) and MLSS_work-rate (3.1 ± 0.4 m s⁻¹). The difference between OBLA and MLSS_work-rate on the cycle-ergometer (r = 0.86; p < 0.001) and treadmill (r = 0.64; p = 0.048) was significantly related to the specific MLSS. We can conclude that the validity of OBLA on predicting MLSS_work-rate is dependent on exercise mode and that its disagreement is related to individual variations in MLSS.     

Light weight concrete: Ra, Th, K contents and dose reduction assessment

Four types of light weight concrete (LWC) commonly used in Hong Kong, namely, autoclave aerated concrete (plus lime), autoclave aerated concrete (plus Pulverized Fuel Ash or PFA), concrete with synthetic aggregate ‘Leca’ and concrete with polystyrene bean as aggregate were measured for their ²²⁶Ra, ²³²Th and ⁴⁰K contents using high-resolution gamma spectrometry. All the radionuclide contents except those for the PFA autoclave aerated concrete were below the world averages of building materials. The Ra-equivalents for these four LWC were 49.6, 249, 122 and 44.2 Bq kg⁻¹, respectively, and were much smaller than a recommended limit of 370 Bq kg⁻¹ for construction materials for dwellings. The gamma-dose rate for an indoor environment with partition walls built with LWC was estimated to be about 20 × 10⁻⁸ Gy h⁻¹, which corresponded to a reduction in the effective dose of about 0.25 mSv y⁻¹ when compared to that obtained for an indoor environment built with normal concrete (NC) only. The Rn exhalation rates from the three lowest Ra-equivalent LWC were calculated as 0.509, 1.28, and 0.335 mBq m⁻² s⁻¹, respectively, which corresponded to a reduction in the indoor Rn concentration of around 14 Bq m⁻³ and reduction in the tracheobronchial dose reaching 1 mSv y⁻¹ by using the James lung-dosimetry model, when compared to the case of NC.     

Averaged EMG profiles in jogging and running at different speeds

EMGs were collected from 14 muscles with surface electrodes in 10 subjects walking 1.25–2.25 m s⁻¹ and running 1.25–4.5 m s⁻¹. The EMGs were rectified, interpolated in 100% of the stride, and averaged over all subjects to give an average profile. In running, these profiles could be decomposed into 10 basic patterns, 8 of which represented only a single burst. Muscles could be divided into a quadriceps, hamstrings, calf and gluteal group, the profiles of which were composed of the same basic patterns. The amplitude of some bursts was constant, but other ones varied with running speed. This speed dependency was generally different between muscles of the same group.

Many muscles show a similar profile in running as in walking. The most notable exception is the calf group, which shows activation in early stance (86–125%), together with quadriceps, instead of in late stance (26–55%) as in walking. This is also visible in low-speed running, ‘jogging’, where stance extends to 46% or 57%, instead of 30–37% as in normal running. Jogging shows some additional differences with normal running, related to this prolonged stance phase.     

Dependency of the [18F]fluoromisonidazole uptake on oxygen delivery and tissue oxygenation in the porcine liver

We have previously shown that the accumulation of fluorine-18-labeled fluoromisonidazole ([¹⁸F]FMISO) is inversely correlated to tissue oxygenation, allowing the quantification of porcine liver tissue hypoxia in vivo. We determined the activity from administered [¹⁸F]FMISO in relation to the hepatic oxygen availability and the partial pressure of oxygen in tissue (tPO₂) to define a critical oxygen delivery on a regional basis. [¹⁸F]FMISO was injected 2 h after onset of regional liver hypoxia due to arterial occlusion of branches of the hepatic artery in 10 domestic pigs. During the experimental procedure the fractional concentration of inspired oxygen (FiO₂) was set to 0.67 in group A ( N=5) and to 0.21 in group B ( N=5) animals. Immediately before sacrifice, the tPO₂ was determined in normal flow and flow-impaired liver segments. The standardized uptake values (SUV) for [¹⁸F]FMISO was calculated from 659 single tissue samples obtained 3 h after injection of approximately 10 MBq/kg body weight [¹⁸F]FMISO and was compared with the regional total hepatic oxygen delivery (DO₂) calculated from the regional arterial and portal venous flow (based on ¹⁴¹Ce- and ^99mTc-microspheres measurements) and the oxygen content of the arterial and portal venous blood. In 121 tPO₂-measured liver tissue samples, the mean DO₂ was significantly decreased in occluded liver tissue samples [group A: 0.063 (0.044–0.089); group B: 0.046 (0.032–0.066)] compared to normal flow segments [group A: 0.177 (0.124–0.252); group B: 0.179 (0.128–0.25) mL·min⁻¹·g⁻¹; geometric mean (95% confidence limits); p < 0.01 in group A and p < 0.001 in group B]. The tPO₂ of occluded segments [group A: 5.1 (3.2–8.1); group B: 3.9 (2.4–6.2) mm Hg] was significantly decreased compared to normal flow segments [group A: 20.2 (12.6–32.5); group B: 22.4 (14.3–35.2) mm Hg; p < 0.01 in group A and p < 0.001 in group B]. Three hours after [¹⁸F]FMISO administration, the mean [¹⁸F]FMISO SUV determined in tPO₂-measured occluded segments was significantly higher [group A: 4.08 (3.12–5.34), group B: 5.43 (4.14–7.13)] compared to normal liver tissue [group A: 1.57 (1.2–2.06), group B: 1.5 (1.16–1.93); p < 0.001 for both groups]. The [¹⁸F]FMISO SUV allowed prediction of the tPO₂ with satisfying accuracy in hypoxic regions using the exponential regression curve { [¹⁸F]FMISO=1.05+6.7^{(−0.117 tPO₂}); r²=0.75;p < 0.001}. In addition, regardless of ventilation conditions, a significant exponential relationship between the DO₂ and the [¹⁸F]FMISO SUV was found ( r²=0.39,p < 0.001). Our results suggest that the reduction of the oxygen delivery below the critical range of 0.1–0.11 mL·min⁻¹·g⁻¹ regularly causes liver tissue hypoxia. The severity of hypoxia is reflected by the [¹⁸F]FMISO accumulation and allows the in vivo estimation of the tPO₂ in hypoxic regions.     

Theoretical basis for long-term measurements of equilibrium factors using LR 115 detectors

In this paper, we propose a method to determine the equilibrium factor using a bare LR 115 detector. The partial sensitivities ρ_i of the LR 115 detector to ²²²Rn and its alpha-emitting short-lived progeny, ²¹⁸Po and ²¹⁴Po, were investigated. We first determined the distributions of lengths of major and minor axes of the perforated alpha tracks in the LR 115 detector produced by ²²²Rn, ²¹⁸Po and ²¹⁴Po through Monte Carlo simulations. The track parameters were calculated using a track development model with a published V function, by assuming a removed active layer of 6.54 μm. The distributions determined for different alpha emitters were found to completely overlap with one another. This implied equality of partial sensitivities for radon and its progeny, which was also confirmed through analytical considerations. Equality of partial sensitivities makes possible convenient measurements of the proxy equilibrium factor F_p, which is defined in the present work as (F₁+F₃) and is equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny (²¹⁸Po+²¹⁴Po) to the concentration of radon gas (²²²Rn). In particular, we have found F_p=(ρ/ρ_itC₀)−1, where ρ (track/m²) is the total track density on the detector, ρ_i=0.288×10⁻² m, t is the exposure time and C₀ (Bq/m³) is the concentration of ²²²Rn. If C₀ is known (e.g. from a separate measurement), we can obtain F_p. The proxy equilibrium factor F_p is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor.     

Use of the ion exchange method for the determination of stability constants of trivalent metal complexes with humic and fulvic acids II. Tb, Yb and Gd complexes in weakly alkaline conditions

The conditional stability constants for tracer concentrations of Tb(III), Yb(III), and Gd(III) with three soil humic acids, three soil fulvic acids and a fulvic acid from weathered coal were determined at pH 9.0–9.1 (these values are similar to those in calcareous soils) in the presence of NaHCO₃ by using the anion exchange method. It was found that 1 : 1 and 1 : 2 complexes were simultaneously formed in the weakly alkaline conditions. The conditional stability constants of these 1 : 1 and 1 : 2 complexes were calculated from the distribution coefficients of rare earth elements at various concentrations of humate or fulvate. The stability constants indicate the very high stability of trivalent Tb³⁺, Yb³⁺ and Gd³⁺ complexes with humic substances in weakly alkaline conditions. The key parameters necessary for the experimental determination of the conditional stability constants of metal ions with humic substances in the presence of NaHCO₃ by using an anion exchange method were discussed. The conditional stability constants of these 1 : 1 and 1 : 2 complexes were compared in this paper. It was found that stabilities of Tb³⁺ 1 : 1 and 1 : 2 complexes with humic acid are greater than the corresponding ones with fulvic acid from the same soil. In addition, the effect of the presence of Ca²⁺ as a competitor on the stabilities of 1 : 1 and 1 : 2 complexes of Yb was examined and no pronounced change of stabilities of 1 : 1 complex was found, even though Ca²⁺ is in a 10³ excess to Yb³⁺.     

Standardization of I by the coincidence method and practical applications

A new coincidence system, based on two thin NaI(Tl) crystals, 50×2 mm², with beryllium windows, 1.5 mg cm⁻², positioned approximately symmetrically from the source holder (at various distances) was constructed. The electronic chains of a classical 4πPC–γ system were utilized. A multichannel analyzer was employed for energy calibration, and an oscilloscope for visualization of the pulses. After calibration, the system was used for the standardization of an ¹²⁵I solution. An energy window of 12–95 keV containing the entire spectrum (single and sum peak) was employed, and a simple demonstration of Taylor's equation [1967. X-ray–X-ray coincidence counting methods for the standardization of ¹²⁵I and ¹⁹⁷Hg. In: Standardization of Radionuclides: Proceedings of a International Atomic Energy Agency Symposium, Vienna, 1966, pp. 341–353, SM-79/65] for whole spectrum counting, was developed. The method and system were tested during the calibration of a LKB 2104 multi-gamma counter, by comparing the detection efficiency values obtained for this prepared standard solution and that utilized in the CIPM-CCRI(II) key comparison. The efficiency of the equipment was calculated as the mean of the two individual values. The result validates the method and demonstrates the accomplishment of the national traceability assurance in nuclear medicine for ¹²⁵I.     

Use of the ion exchange method for the determination of stability constants of trivalent metal complexes with humic and fulvic acids—Part I: Eu and Am complexes in weakly acidic conditions

The conditional stability constants for tracer concentrations of Eu(III) and Am(III) with a red earth humic acid (REHA), a red earth fulvic acid (REFA) and a fulvic acid from weathered coal (WFA) were determined at pH 5.2–6.4 (such values are similar to those in non-calcareous soils) in the presence of HAc/NaAc or NaNO₃ by using the cation exchange method. It was found that 1 : 1 complexes were predominately formed in weakly acidic conditions. The total exchangeable proton capacities and the degrees of dissociation of these humic substances were determined by using a potentiometric titration method.

The key parameters necessary for the experimental determination of the conditional stability constants of metal ions with humic substances in weakly acidic conditions by using the cation exchange method were discussed.

The conditional stability constants of 1 : 1 complexes obtained in this paper were compared with the literature data of Am(III) determined by using the ion exchange method and the solvent extraction method and with the stability constants of 1 : 1 complexes of UO₂²⁺ and Th⁴⁺ with the same soil humic substances. These results indicate the great stability of bivalent UO₂²⁺, trivalent Eu³⁺, Am³⁺ and tetravalent Th⁴⁺ complexes with humic and fulvic acids in weakly acidic conditions.     

Radiotracer technique in adsorption study: Part XVII. Removal Behaviour of Alkali Metal (K- and Li-) Titanates for Cd(II)

Alkali metal (potassium and lithium) titanates were synthesized and employed for the efficient removal of Cd(II) ions from aqueous solutions using the radiotracer technique. The possible mechanism involved at the solid/solution interface was deduced with the help of various physico–chemical data, i.e. effect of adsorptive concentration temperature and pH. The effect of added cations and H⁺ (HCl/H₂SO₄) in the uptake process was also seen. The radiation stability of these materials in the adsorption process was assessed by employing a 11.1 GBq (Ra–Be) neutron source having an integral neutron flux of 3.85×10⁶ n·cm⁻² s⁻¹ and associated with a nominal γ-dose of ca. 1.72 Gy/h.