Anthropogenic emissions of210Po,210Pb and226Ra in an estuarine environment

An extensive study on the distribution of natural radionuclides in an estuarine ecosystem located in Southwestern Spain is presented. This environment is highly affected by the wastes released by a phosphoric acid industry which uses phosphate rocks as raw material for fertilizer production. This rock has generally high concentrations of U and its daughters. The estuary is formed by two rivers, Odiel and Tinto, which have a common mouth into the Atlanic Ocean and a salt marsh (Odiel marsh) affected by the income of Odiel riverwaters. This river receives directly the liquid and part of the solid (gypsum) wastes released from the industries. Besides that, most of the phosphogypsum wastes are stored in uncovered piles at the right margin of the Tinto river. The study has concluded that the wastes from such industries are the cause of the enhanced concentrations found at the bed of both river channels as well as the enhancement found in surface soils in certain zones of the Odiel wet marshland. Indeed, the Northern marsh and the Mojarrera channel at the Odiel marsh seem to be the main sinks of the contaminant released by the phosphoric acid industry.     

A comparison of methods for the determination of the dating-nuclides210Pb and226Ra

Lead-210 is often used to date recent (100 y) environmental samples. Three different methods for its determination are compared:²¹⁰Pb -counting with a low level proportional counter,²¹⁰Pb -spectroscopy and²¹⁰Po -spectroscopy. Agreement within analytical errors was found for the three methods in two sediment cores from Lake Zurich, Switzerland and in IAEA SD-A-1 deep sea reference material. For²¹⁰Po -spectroscopy, the detection and determination limit is an order of magnitude lower than these for the other methods. Methods for the determination of²²⁶Ra are also discussed. Measurements on low level proportional counters are difficult to interpret and not suitable for routine work. A better way to measure²²⁶Ra is -spectroscopy of colloidal Ba(Ra)SO₄.     

226Ra, 228Ra and 210Pb Isotopes in Some Water Samples of Mines

A method for the determination of ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb in water samples of mining regions by measuring the and intensities with the help of a liquid scintillation counter is presented. The high-energy part of the -particle spectrum emitted by ²¹⁰Bi is used for the determination of ²¹⁰Pb content in the samples. An attempt is also given to explain the radioactive disequilibrium between ²²⁶Ra and ²¹⁰Pb in the samples investigated.     

226Ra, 210Pb, 210Bi and 210Po deposition and removal from surfaces and liquids

Deposition of ²²⁶Ra from water on nylon was investigated. Measurements performed for different pH and different radium concentrations in the water gave similar absolute activities deposited on the foil surface. Obtained results were used to estimate the amount of ²²⁶Ra plated-out on the nylon scintillator vessel in the solar neutrino experiment BOREXINO during filling of the detector. Another problem studied in the frame of BOREXINO was the removal of ²¹⁰Pb from its organic liquid scintillator by applying distillation and water extraction. After several tests had been performed for both methods it was found that after the water extraction the initial lead content in the scintillator sample was reduced only accordingly to the ratio of the volumes of the applied liquids (simple dilution). In contrast to this, distillation was very effective providing in the best case a ²¹⁰Pb reduction factor higher than 100. Removal efficiencies of the long-lived ²²²Rn daughters during etching from surfaces of standard and high purity germanium were investigated in the frame of the GERDA experiment, which aims to search for neutrino-less double beta decay of ⁷⁶Ge. The standard etching procedure of Canberra used during production of high purity n-type germanium diodes was applied to germanium discs, which had been exposed earlier to a strong ²²²Rn source for its progenies deposition. In contrast to copper and stainless steel, ²¹⁰Pb, ²¹⁰Bi and ²¹⁰Po was removed from germanium very efficiently. An evidence of a reverse process was also observed—the isotopes were transferred from the etchant to the clean germanium surface.     

The determination of134Cs,137Cs,210Pb,226Ra and228Ra concentrations in nearshore marine sediments and seawater

Multi-radionuclide analyses of coastal marine sediments and seawater can be of considerable value in defining rates and mechanisms of nearshore processes. A preliminary study of¹³⁴Cs,¹³⁷Cs,²¹⁰Pb,²²⁶Ra and²²⁸Ra in the Clyde Sea Area has been performed. A summary of the marine geochemistries of these species and a detailed account of methods involved in their routine analysis are described.     

Rate of sedimentation in the Yamuna river around Delhi using the226Ra−210Pb method

For six sediment cores collected from Yamuna river (tributary of Ganges) around Delhi, rate of sedimentation was determined by the²²⁶Ra–²¹⁰Pb method. While an average rate of 42 mm/y is obtained, there are variations core to core. A clear-cut downstream increase in the rate, from 5 mm/y when the river enters Delhi, to 80 mm/y when it leaves Delhi, indicates solid waste contribution from the urban areas. The sediment flux of 4000 mg/cm²/y is not balanced by the calculated rate of erosion (40 tonnes/km²/y) in the river. Thus, much of the sediment flux is of local origin.     

224Ra correction for determination of 226Ra in environmental materials

The most commonly available 226Ra determination was too time-consuming to be suited to 226Ra monitoring for the accidental release. The formula for determination of 226Ra was derived by 224Ra correction for WHO's equation. A rapid determination of 226Ra in environmental materials was made possible by using this formula. The 226Ra values of the soil and natural water at Ningyoh-Tohge obtained by the present method were in good agreement with those by the conventional WHO method. It was demonstrated that 226Ra of more than about 37 mBq (1 pCi) in the sample could be determined within 4 days by this method.     

Studies on226Ra and210Pb activities and the concentration factors of226Ra in the surface organic layers of the estuarine sediments of Mindola and Purna rivers in India

The sediment samples have been collected from estuarine regions of Mindola and Purna of Gujarat State. These samples are found to contain less than 3% of organic matter which scavange and carry most of the activity of²²⁶Ra, etc., to the sediment floor. The activities of²²⁶Ra are found to vary from 0.1 to 0.5 pCi/g, while²¹⁰Pb activities lie in the range of 3 to 8 pCi/g. These activities find their way into the organisms present in sea water and then into fish which is finally consumed by humans. This paper gives in detail the sampling techniques, experimental procedures and the distribution of the isotopes of²²⁶Ra and²¹⁰Pb in the estuarine regions and the concentration factors of²²⁶Ra in the region.     

Rapid determination of 226Ra in environmental samples

A new rapid method for the determination of ²²⁶Ra in environmental samples has been developed at the Savannah River Site Environmental Lab (Aiken, SC, USA) that can be used for emergency response or routine sample analyses. The need for rapid analyses in the event of a Radiological Dispersive Device or Improvised Nuclear Device event is well-known. In addition, the recent accident at Fukushima Nuclear Power Plant in March, 2011 reinforces the need to have rapid analyses for radionuclides in environmental samples in the event of a nuclear accident. ²²⁶Ra (T1/2?=?1,620?years) is one of the most toxic of the long-lived alpha-emitters present in the environment due to its long life and its tendency to concentrate in bones, which increases the internal radiation dose of individuals. The new method to determine ²²⁶Ra in environmental samples utilizes a rapid sodium hydroxide fusion method for solid samples, calcium carbonate precipitation to preconcentrate Ra, and rapid column separation steps to remove interferences. The column separation process uses cation exchange resin to remove large amounts of calcium, Sr Resin to remove barium and Ln Resin as a final purification step to remove ²²⁵Ac and potential interferences. The purified ²²⁶Ra sample test sources are prepared using barium sulfate microprecipitation in the presence of isopropanol for counting by alpha spectrometry. The method showed good chemical recoveries and effective removal of interferences. The determination of ²²⁶Ra in environmental samples can be performed in less than 16?h for vegetation, concrete, brick, soil, and air filter samples with excellent quality for emergency or routine analyses. The sample preparation work takes less than 6?h. ²²⁵Ra (T1/2?=?14.9?day) tracer is used and the ²²⁵Ra progeny ²¹⁷At is used to determine chemical yield via alpha spectrometry. The rapid fusion technique is a rugged sample digestion method that ensures that any refractory radium particles are effectively digested. The preconcentration and column separation steps can also be applied to aqueous samples with good results.     

226Ra, 228Ra and 228Ra/226Ra in surface marine sediment of Malaysia

Surface sediment samples were collected at the West (east coast and west coast of Peninsular Malaysia) and East (Sabah and Sarawak) Malaysia in several expeditions within August 2003 until June 2008 for determining the level of natural radium isotopes. Activity concentrations of ²²⁶Ra and ²²⁸Ra in surface marine sediment at 176 sampling stations were measured. The activity concentrations of both radionuclides in Malaysia (East and West Malaysia) display varied with the range from 9 to 158 Bq/kg dry wt. and 13 to 104 Bq/kg dry wt., respectively. Meanwhile, the ratio distributions of ²²⁸Ra/²²⁶Ra were ranged from 0.62 to 3.75. This indicated that the ratios were slightly high at west coast of Peninsular Malaysia compared to other regions (east coast of Peninsular Malaysia, Sabah and Sarawak). The variation of activity concentrations of ²²⁶Ra and ²²⁸Ra and its ratios were also supported by the statistical analyses of one-way ANOVA and t test at 95 % confidence level, whereby there were proved that the measured values were different between the regions. These different were strictly related to their half-life, potential input sources (included their parents, ²³⁸U and ²³²Th), parent’s characteristic, the geological setting/formation of the study area, environment origin and behavior.     

Rapid determination of 226Ra in emergency urine samples

A new method has been developed at the Savannah River National Laboratory (SRNL) that can be used for the rapid determination of ²²⁶Ra in emergency urine samples following a radiological incident. If a radiological dispersive device event or a nuclear accident occurs, there will be an urgent need for rapid analyses of radionuclides in urine samples to ensure the safety of the public. Large numbers of urine samples will have to be analyzed very quickly. This new SRNL method was applied to 100 mL urine aliquots, however this method can be applied to smaller or larger sample aliquots as needed. The method was optimized for rapid turnaround times; urine samples may be prepared for counting in <3 h. A rapid calcium phosphate precipitation method was used to pre-concentrate ²²⁶Ra from the urine sample matrix, followed by removal of calcium by cation exchange separation. A stacked elution method using DGA Resin was used to purify the ²²⁶Ra during the cation exchange elution step. This approach combines the cation resin elution step with the simultaneous purification of ²²⁶Ra with DGA Resin, saving time. ¹³³Ba was used instead of ²²⁵Ra as tracer to allow immediate counting; however, ²²⁵Ra can still be used as an option. The rapid purification of ²²⁶Ra to remove interferences using DGA Resin was compared with a slightly longer Ln Resin approach. A final barium sulfate micro-precipitation step was used with isopropanol present to reduce solubility; producing alpha spectrometry sources with peaks typically <40 keV FWHM (full width half max). This new rapid method is fast, has very high tracer yield (>90 %), and removes interferences effectively. The sample preparation method can also be adapted to ICP-MS measurement of ²²⁶Ra, with rapid removal of isobaric interferences.     

Radiochemical determination of210Po and210Pb in water

A method for²¹⁰Po and²¹⁰Pb determination in water samples is described. The nuclides are concentrated, in presence of added²⁰⁸Po and lead carrier, by evaporation. Then the polonium is plated electroless from the acidic solution on a copper planchet and measured by alpha spectrometry.²¹⁰Pb separation from the other isotopes is based on the solutility of PbSO₄ in citrate.²¹⁰Pb content is determined by measuring the activity of its daughter²¹⁰Bi. The critical steps in the isolation of lead have been examined and discussed.     

Considerations about the226Ra gross alpha counting determination

Chemical elemental compositions of some silicate, magnetic and glass spherules were investigated with INAA. The elements determined include Os, Ir, Ni, Co, Fe, Cr, Au, La, Ce, Sm, Eu, Yb, Lu and Sc etc. The elemental correlation, as well as their enrichment (or depletion) factors relative to Cl chondrite were examined. The high concentrations of the refractory siderophile elements contained in these spherules support the proposal that they originate from extraterrestrial substances. Some useful chemical criteria for identifying the sources of silicate, magnetic and glass spherules are put forward.     

Treatment of an aqueous radioactive waste solution with elevated levels of226Ra and228Ra

Treatment of an aqueous radioactive waste solution to remove radium prior to discharge was conducted at a laboratory scale. The actual solution is mainly composed of combined radium (²²⁶Ra and²²⁸Ra) with high concentrations of manganese, iron and calcium, which are present as chlorides in dilute hydrochloric acid. Direct precipitation by sulfate anions was selected to be the more viable treatment technique. Sulfate anion concentration, free acidity, temperature and aging of the sulfate precipitate in the supernate prior to filtration are factors that were investigated for their effect on the separation efficiency. The data obtained are discussed in detail.     

Development of a sequential method for the determination of238U,234U,232Th,230Th,228Th,228Ra,226Ra,and210Pb. in environmental samples

A sequential analytical method for the determination of²³⁸U,²³⁴U,²³²Th,²³⁰Th,²²⁸Th,²²⁸Ra,²²⁶Ra and²¹⁰Pb in environmental samples was developed. Uranium and thorium isotopes are first chromatographically sepaaated using tri-n-octyl phosphine oxide (TOPO) supported on silica gel. The uranium isotopes are determined by alpha-spectrometry following extraction with TOPO onto a polymeric membrane. Thorium isotopes are co-precipitated with lanthanum fluoride before counting in an alpha spectrometer. Radium isotopes and²¹⁰Pb are separated by co-precipitation/precipitation with mixed barium/lead sulphate. Radium-226 is determined by gross alpha counting of the final BaSO₄ precipitate and²²⁸Ra by gross beta counting of the same source. Lead-210 is determined through beta counting of its daughter product²¹⁰Bi.     

Separation and electrodeposition of226Ra

The chemical behavior of calcium, barium and radium in the ion exchange resins Dowex 50W-X8, AG 50W-X8 and Merk I in the presence of ammonium tartrate, EDTA, and citrate has been studied. No differences were observed in results while using any one of the three resins. Calcium, barium and radium were fixed to the exchange column at pH 4.8 EDTA solution. Calcium was eluted in an EDTA solution at pH 5.3, barium and radium between pH 8–11. Elution in citrate media for calcium was achieved at pH 6.1 and for radium at pH 10. In ammonium tartrate, calcium was eluted at pH 6, barium and radium at pH 11.5. Radium was also eluted from the ion exchange resins with a 2M nitric acid solution. The radium free of calcium was electrodeposited onto a stainless steel disc cathode using a 0.1 M potassium fluoride solution, pH 12–14, with a yield of >50%. The energies of²²⁶Ra were analyzed through high resolution -spectra. The²²⁶Ra utilized for these experiments was separated from Mexican carnotite.     

Marine radioactivity concentration in the Exclusive Economic Zone of Peninsular Malaysia: 226Ra, 228Ra and 228Ra/226Ra

The present occurrence of ²²⁶Ra and ²²⁸Ra in marine sediment core and fish from the Exclusive Economic Zone in the east coast of Peninsular Malaysia were studied. Sediment core and biota in respectively was collected using multicorer device and purchased from local fishermen at identified stations during the cruise expedition conducted in 2008. The purpose of this study was to determine and to make available an inventory of activity concentration levels and activity ratio for these radionuclides in this region. The activity concentrations of ²²⁶Ra and ²²⁸Ra in sediment core and edible part of fish were ranged between 15.9–46.5 and 27.7–87.1 Bq/kg dry wt and; 0.80–2.13 and <0.95–3.57 Bq/kg fresh wt, respectively. Meanwhile, the activity ratios of ²²⁸Ra/²²⁶Ra in sediment core and fish were varied with the range between 1.63–2.09 and 0.45–2.38, respectively. Refer to those ranges the activity concentrations of radium isotopes were comparable with other region. Thus, it can be concluded that the occurrence of radium isotopes mainly supplied from terrestrial sources and the factors of assimilation efficiency and transfer coefficient of radium may probably effect to the variation activity concentration of ²²⁶Ra and ²²⁸Ra and its activity ratio in edible part of pelagic and demersal fish obtained in this study.