Separation and preconcentration of strontium from biological, environmental, and nuclear waste samples by extraction chromatography using a crown ether.

The potential of Lemna gibba L. to clean uranium and arsenic contamination from mine surface waters was investigated in wetlands of two former uranium mines in eastern Germany and in laboratory hydroponic culture. Water and plants were sampled and L gibba growth and yield were monitored in tailing ponds from the field study sites. Contaminant accumulation, growth and yield experiments were conducted in the laboratory using synthetic tailing water. Mean background concentrations of the surface waters were 186.0+/-81.2 microg l(-1) uranium and 47.0+/-21.3 microg l(-1) arsenic in Site one and 293.7+/-121.3 microg l(-1) uranium and 41.37+/-24.7 microg l(-1) arsenic in Site two. The initial concentration of both uranium and arsenic in the culture solutions was 100 microg l(-1). The plant samples were either not leached, leached with deionized H2O or ethylenediaminetetracetic (EDTA). The results revealed high bioaccumulation coefficients for both uranium and arsenic. Uranium and arsenic content of L gibba dry biomass of the field samples were as follows: nonleached samples > deionized H2O leached (insignificant ANOVA p = 0.05) > EDTA leached. The difference in both arsenic and uranium enrichment were significantly high between the nonleached and the other two lead samples tested at ANOVA p > 0.001. Estimated mean L gibba density in surface water was 85,344.8+/-1843.4 fronds m(-2) (approximately 1319.7 g m(-2)). The maximum specific growth rate was 0.47+/-0.2 d(-1), which exceeded reported specific growth rates for L gibba in the literature. Average yield was estimated at 20.2+/-6.7 g m(-2) d(-1), giving approximately 73.6+/-21.4 t ha(-1) y(-1) as the annual yield. The highest accumulations observed were 896.9+/-203.8 mg kg(-1) uranium and 1021.7+/-250.8 mg kg(-1) arsenic dry biomass for a 21-d test period in the laboratory steady-state experiments. The potential extractions from surface waters with L gibba L. were estimated to be 662.7 kg uranium ha(-1) yr(-1) and 751.9 kg arsenic ha(-1) yr(-1) under the above conditions.

Capacity of Lemna gibba L. (duckweed) for uranium and arsenic phytoremediation in mine tailing waters.

The discharges of uranium and associated radionuclides as well as heavy metals and metalloids from waste and tailing dumps in abandoned uranium mining and processing sites pose contamination risks to surface and groundwater. Although many more are being planned for nuclear energy purposes, most of the abandoned uranium mines are a legacy of uranium production that fuelled arms race during the cold war of the last century. Since the end of cold war, there have been efforts to rehabilitate the mining sites, initially, using classical remediation techniques based on high chemical and civil engineering. Recently, bioremediation technology has been sought as alternatives to the classical approach due to reasons, which include: (a) high demand of sites requiring remediation; (b) the economic implication of running and maintaining the facilities due to high energy and work force demand; and (c) the pattern and characteristics of contaminant discharges in most of the former uranium mining and processing sites prevents the use of classical methods. This review discusses risks of uranium contamination from abandoned uranium mines from the biogeochemical point of view and the potential and limitation of uranium bioremediation technique as alternative to classical approach in abandoned uranium mining and processing sites.

Biogeochemical behaviour and bioremediation of uranium in waters of abandoned mines.

Partition of radionuclides in aqueous liquid-liquid systems allows speciation of bioinorganic forms under nondenaturing conditions. From the fresh pasteurized skim bovine milk spiked with respective radionuclides and agitated with 4% w/w water solution of apple pectin, about 80% of cesium, 22% of strontium and less than 1.5% of europium is recovered with the pectin, phase at an initial milk — pectin volume ratio of 7∶3. This recovery fraction is proportional to the abundance of radionuclides in milk serum. No protein bound fraction of strontium extractable by Aerosol OT in isooctane was obtained. More than 3-fold preconcentration of strontium and europium radionuclides in milk is achieved after 10–15 min membraneless osmosis with pectin phase.

Distribution and speciation of cesium, strontium, and europium in the aqueous two-phase system milk-pectin

Polonium was precipitated from dilute solutions with metaarsenites, dichromates, iodides, molybdates, sulphites, sulphates and metavanadates. The solubility products of polonium iodide, molybdate, sulphite and sulphate were determined to be 1.92, 3.7, 3.3 and 0.9 respectively.

Precipitation and solubility of some polonium compounds

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.

Radiochemical determination of210Po and210Pb in water

Transfer of210Pb and210Po from an uranium mine and mill to the environment was studied by measuring their concentrations in different stages of uranium extraction technology, in waste products from the mill and in environmental waters. A slightly modified radiochemical method was used for210Po and210Pb determination.

Transfer of210Pb and210Po to the environment during mining and processing of uranium ores

The radioactivities of90Sr,137Cs and134Cs have been measured in soil, fodder and milk from the south-western region of Slovenia, Yugoslavia after the Chernobyl accident. Maximal concentrations of Sr-isotopes in samples and the rate of their decrease in a period up to two years after the accident are given. The transfer of radionuclides from soil to grass and from fodder to milk is discussed.

Radioactivity of cattle fodder and milk after the chernobyl accident

The extraction of plutonium(VI) and plutonium(III) from sulphuric acid by TOA in toluene has been studied as a function of the acid and tri-octyl amine concentration A comparison of the extraction properties of plutonium with those of uranium(VI) and uranium(IV) has been made It was found that the extraction properties of plutonium(VI) are very similar to those of uranium(VI) and that TOA is a relatively poor extractant for plutonium(III) Uranium(IV) shows better extraction properties than plutonium(III) The results obtained are considered in the light of the stabilities of the complexes formed by these elements in the organic and aqueous phase A method of separation of both elements by solvent extraction based on changing their oxidation states is suggested

Extraction of plutonium from sulphuric acid by TOA in toluene

Some properties of natural zeolite from Zaloska gorica, Slovenia, Yugoslavia were investigated to establish its applicability in solidification and for storage purposes of radioactive waste. It was found that this material is a rather good sorber for cesium, with a capacity of about 0.6 meq g−1. The migration rate of Cs+ in a system ion exchanger-aqueous solution was investigated and correlated with the sorption behaviour of cesium in a system. The leaching rate of cesium from concrete containing zeolite was measured.

K. Južnič

Papers

Radiochemical determination of210Po and210Pb in water

Transfer of210Pb and210Po to the environment during mining and processing of uranium ores

Radioactivity of cattle fodder and milk after the chernobyl accident

Extraction of plutonium from sulphuric acid by TOA in toluene

Migration of radiocesium in a zeolite-solution system