Plutonium isotopes in the Hungarian environment

More than 50 soil samples were analysed from different parts of the country, the activity concentration of 239+240Pu was in the range of 0.01-0.84 Bq/kg dry soil with the average of 0.10 Bq/kg. 238Pu could be detected only in few moss samples and 238Pu/239+240Pu ratio determines the origin of plutonium. 241Pu was determined by liquid scintillation spectrometry. The activity concentration of this isotope in the soil is between 0.04 and 3.74 Bq/kg with the average of 0.82 Bq/kg, while in the moss is also similar 0.01-2.07 Bq/kg fresh mass with the average of 0.43 Bq/kg. Significant difference could not be observed between the different types of soils occurring in the country, but the results could be sorted according to the sampling carried out on undisturbed or cultivated area. The isotope ratios 241Pu/239+240Pu prove that the origin of the plutonium in Hungary is the global fallout determined by the atmospheric nuclear weapon tests.     

Radium removal from mine waters in underground treatment installations

The underground mining of hard coal is widespread in the Upper Silesian Coal Basin (southern Poland). In deep mines, inflows of highly mineralised waters containing radium isotopes are numerous. These waters cause severe damage to the natural environment due to the salinity, but additionally radioactive pollution occurs. The region is densely populated, therefore mitigation methods are very important. The method of radium removal has been applied in full technical scale in two coal mines with very good results - in one of the mines radium-bearing waters are treated at the rate of approximately 0.1m(3)s(-1), while in another mine salty waters are purified at the rate of 0.1m(3)s(-1). The purification takes place in special underground galleries without any contact of the mining crew with the radioactive deposits produced during the process. As a result, release of radium is significantly lower, more than 200MBq of (226)Ra and (228)Ra remains underground each day.     

Radium geochemistry in Na-Cl type groundwater in Niigata Prefecture, Japan

Radium isotopes in 23 Na-Cl type groundwater sampled mainly from deep wells in Niigata Prefecture, which is the site of the largest oil- and gas-fields in Japan, were measured along with U isotopes, chemical components and hydrogen and oxygen isotope ratios to elucidate the distribution and behavior of Ra in a brackish environment underground. Also analyzed were U and Th isotopes in 38 rock samples collected from outcrops at 17 locations. Ra-226 concentrations (8.86-1637 mBq kg⁻¹) of groundwater samples roughly correlated with total dissolved solid (TDS) concentrations and other alkaline earth contents. Their ²²⁸Ra/²²⁶Ra activity ratios (0.32-5.2) were similar to or higher than the ²³²Th/²³⁸U activity ratios (0.6-1.7) in the rocks. The most likely transport mechanism of Ra isotopes into groundwater was due to their α-recoil from the solid phase, probably from the water-rock interface where Th isotopes had accumulated, and adsorption/desorption reaction based on the increase in ²²⁶Ra contents with TDS.     

Radium and uranium levels in vegetables grown using different farming management systems

Vegetables grown with phosphate fertilizer (conventional management), with bovine manure fertilization (organic management) and in a mineral nutrient solution (hydroponic) were analyzed and the concentrations of ²³⁸U, ²²⁶Ra and ²²⁸Ra in lettuce, carrots, and beans were compared. Lettuce from hydroponic farming system showed the lowest concentration of radionuclides 0.51 for ²²⁶Ra, 0.55 for ²²⁸Ra and 0.24 for ²³⁸U (Bq kg⁻¹ dry). Vegetables from organically and conventionally grown farming systems showed no differences in the concentration of radium and uranium. Relationships between uranium content in plants and exchangeable Ca and Mg in soil were found, whereas Ra in vegetables was inversely correlated to the cation exchange capacity of soil, leading to the assumption that by supplying carbonate and cations to soil, liming may cause an increase of U and a decrease of radium uptake by plants. The soil to plant transfer varied from 10⁻⁴ to 10⁻² for ²³⁸U and from 10⁻² to 10⁻¹ for ²²⁸Ra.     

Radium contamination of the banks of the river Laak as a consequence of the phosphate industry in Belgium

For over half a century, phosphate ores of marine origin, containing 226Ra, have been processed in Belgium to produce calcium phosphate for use in cattle food. As a result, the waste water containing 226Ra were discharged into two little rivers, one of which is the Laak. The purpose of this study was to chart the radium contamination of the river banks and some areas that are regularly flooded by the river. It was seen that enhanced concentrations of 226Ra do occur along the river banks, but that the contaminated area is mostly confined to a 10 m strip on both sides of the river, even in the flooding zones. At present, no dwellings are present on top of the contamination and no crops for direct human consumption are grown there, so there is no immediate threat to the population.     

Dissolution of 226Radium from pipe-scale deposits in a public water supply

This study was undertaken to determine if dissolution of 226Radium from pipe-scale deposits contributes to enhanced waterborne 226Radium concentrations at the point of use. Water samples were collected from residential water customers of a small rural Iowa town. Sites were evenly divided between new and old water main connections. Daily samples were collected from the point-of-entry water. Point-of-use 226Radium concentrations ranged from 0.4 to 12.9 pCi L-1 (0.01 to 0.5 Bq L-1). The mean 226 Radium concentration for homes connected to old water mains was significantly higher than the mean 226Radium concentration of homes connected to new water mains, mean(standard deviation) equal 8.3(1.1) and 5.3(0.8) pCi L-1 [0.3(1.1) and 0.2(0.8) Bq L-1], respectively. 226Radium concentrations of the point-of-entry water ranged from 5.0 pCi L-1 to 10.3 pCi L-1 (0.2 Bq L-1 to 0.4 Bq L-1). This study indicates considerable variability of 226Radium exposure from drinking water among residents of the same water supply and has implications for regulatory compliance and exposure assessment in epidemiologic studies.     

Radium equivalent activity concentrations in concrete building blocks in eight cities in Southwestern Nigeria

The radioactivity concentrations of (226)Ra, (232)Th and (40)K were measured by using gamma ray spectroscopy in 130 concrete building blocks collected from block making sites in eight cities in Southwestern Nigeria. The results were used to compute the radium equivalent activity concentration for each city. The values of the concentrations of the primordial radionuclides varied widely within each city and among the cities. The weighted means for the cities range between 13.3 and 18.4, 28.2 and 71.6, and 176.2 and 336.8 Bq/kg for (226)Ra, (232)Th and (40)K, respectively. The city weighted means of radium equivalent activity concentrations for the eight cities range from 81 to 145 with a mean of 101 Bq/kg. The maximum for external hazard index was determined as 0.39. All the values are within the safety limits recommended by UNSCEAR [United Nations Scientific Committee on the Effects of Atomic Radiation 1982. Report to the General Assembly, with annexes. New York, United Nations.].     

Studies on the Leaching of Radium and the emanation of radon from fertilizer process sludge

Radium-226 present in rock phosphate is carried to CaCO₃, the main process waste sludge of the fertilizer industry. Disposal of the sludge in the environment enhances the radiation background in the area. Two states of adherence of radium in the sludge have been identified, one loosely bound and the other chemically exchanged. The loosely bound fraction accounts for nearly 40% of the total activity, as demonstrated by leaching studies. Laboratory experiments show that activity leach-out by infiltration of water through the sludge is low. Lateral seepage is found to cause extensive areal contamination due to dispersal of suspended solids in the vicinity of the disposal area. The rate of emanation of radon from the sludge is found to be high, a factor of 10 over the normal background emanation rate. The radiation field in the waste disposal area also shows enhancement, with levels 4–6 times higher than natural background.     

Uranium series isotopes in the Avon Valley, Nova Scotia

An U-series isotopic study was carried out in the waters of the Avon Valley, Nova Scotia. The fresh and acidic recharge waters flow rapidly through the watershed composed of a granitic highland and a sedimentary, largely carbonate, lowland plain, before draining to the sea. There is no significant anthropogenic pollution; but, naturally elevated U levels can be encountered within the bedrock. Nonetheless, the U concentrations of the surface and groundwater are low (generally within the range of several hundredths to several tenths of a microg l(-1)), except in the proximity to weathering of U mineralization. The dissolved U in the surface waters appears to be stabilized by organic rather than inorganic complexes. Both the groundwaters and surface waters have similar (234)U/(238)U activity ratios that rarely deviate from secular equilibrium by more than 20% throughout the watershed. The magnitude of the (234)U/(238)U activity ratio is not determined by lithology but rather by the weathering mechanism, the high rate of flushing, and the leaching of local U mineralization. Dissolved Ra is consistently absent. The dissolved Rn concentrations, though variable, are measurable even in surface waters. This may be due to a continual degassing from the U-enriched bedrock or release from local sites of U mineralization underlying the surface water sources.     

Size-fractionated plutonium isotopes in a coastal environment

We have examined the distribution of individual Pu isotopes (239Pu, 240Pu, and 241Pu) in seawater from the Gulf of Maine (GOM). Samples were size-fractionated with a 1 kD cross-flow ultrafiltration (CFF) membrane. Subfractioned samples were radiochemically purified and Pu isotopes were analyzed using a three-stage thermal ionization mass spectrometer (TIMS). To our knowledge, this is the first time that both size class and Pu isotopic data have been obtained for seawater samples. Within measurement uncertainties a single 240Pu/239Pu atom ratio of 0.18 was found for all sample collection depths and sample size fractions. This signifies a current, single Pu source in GOM waters, namely global fallout, and suggests that no measurable isotopic fractionation occurred during CFF processing. The majority of Pu was found in the low molecular weight fraction (< 1 kD). Colloidal Pu varied from 8% of the total in surface waters to < 1% in the deepest (250 m) seawater sample. Evidence suggests that the vertical distribution of Pu in GOM is primarily controlled by conservative mixing processes. The high Pu fraction found in the low molecular size fraction implies that most of the Pu is in the non-particle-reactive oxidized fraction, and is consistent with the conservative Pu behavior. The activity levels are in agreement with other studies which show a slow decrease in Pu with time due to continued mixing and relatively slow particle removal.     

Uranium isotopes in Tunisian bottled mineral waters

²³⁴U and ²³⁸U activity concentrations and their relative effective doses have been determined in 10 bottled mineral waters in Tunisia. Alpha spectrometry was used as technique to measure uranium isotopes. The obtained isotopic ratio ²³⁴U/²³⁸U varies between 1.1 and 3 which means that the two isotopes are not in radioactive equilibrium. Measured activity concentration varies between 3.2 and 40 mBq/l for ²³⁴U and between 1.5 and 26.3 mBq/l for ²³⁸U. Effective doses (assuming 2 litres per day of water consumption) coming from this two isotopes are found to vary between 0.16 and 2.02 μSv/a which is lower than the maximum recommended dose level by the WHO.     

Thorium isotopes in the surface air of the Western North Pacific Ocean

The concentrations and activity ratios of thorium isotopes in maritime airborne particles, collected over the western North Pacific along 137° E during cruises in January 1982 and 1983 and in March 1983, are reported here. The ²³²Th concentration in air is high at mid-latitude, near the Japanese islands and decreases southwards further from land. The ²³²Th concentration ranges from 0·036 to 0·22 μBq m⁻³. The ²³⁰Th/²³²Th activity ratio in the maritime air is almost unity, reflecting the U/Th activity ratio coupled with the crustal abundance. The ²²⁸Th/²³²Th activity ratio ranges from 3 to 69·5 and is, in general, higher than that in air over land. The results indicate the importance of the aeolian flux of the thorium isotopes, especially for ²³²Th and ²²⁸Th, in the geochemical cycle of thorium in the marine environment.     

Radium and radium-daughter nuclides in carbonates: a brief overview of strategies for determining chronologies

Radium isotopes have been used extensively to trace the movement of groundwater as well as oceanic water masses, but these radionuclides (and their daughters) are also useful chronometers for the determination of the time scales of other Earth and environmental processes. The purpose of this overview is to present the application of Ra and Ra daughters in the dating of carbonates. We show that the choice of dating method (decay of excess radionuclide or ingrowth of daughter) depends strongly on the parent/daughter activity ratios in the water in which the carbonate was precipitated. Thus freshly precipitated carbonates uniformly show excesses of ²²⁶Ra relative to its parent ²³⁰Th, and ²²⁶Ra decay can provide ages of carbonates over Holocene time scales. In contrast, carbonates are precipitated in waters of greatly varying ²¹⁰Pb/²²⁶Ra. Corals, deep-sea hydrothermal vent clams and the shelled cephalopod Nautilus live in waters with significant dissolved ²¹⁰Pb and all show excesses of ²¹⁰Pb in their carbonate. Bivalve molluscs from nearshore and coastal waters, and carbonates deposited from groundwater environments (e.g. travertines) in which ²¹⁰Pb is efficiently scavenged from solution, show deficiencies of ²¹⁰Pb relative to ²²⁶Ra. In contrast, fish otoliths strongly discriminate against ²¹⁰Pb regardless of the environment in which the fish lives. Deficiencies of ²²⁸Th relative to ²²⁸Ra are common in all carbonates. Useful time ranges for the ²¹⁰Pb/²²⁶Ra and ²²⁸Th/²²⁸Ra chronometers are ∼100 y and ∼10 y, respectively.     

Lead isotopes in environmental sciences: a review

Lead (Pb) isotopic analyses proved to be a very efficient tool for tracing the sources of local and global Pb pollution. This review presents an overview of literature published on the use of Pb isotopic analyses of different environmental matrices (atmospheric aerosols, lichens, tree rings, peat deposits, lake, stream, marine sediments, soils, etc.). In order to gain more insight, the isotopic compositions of major sources of Pb in the environment as determined by several authors are described in detail. These include, above all, the former use of leaded gasoline, coal combustion, industrial activities (e.g., metallurgy) and waste incineration. Furthermore, this review summarises analytical techniques (especially ICP-MS) used for the determination of Pb isotopes in environmental samples.     

Application of the Weibull extrapolation to 137Cs geochronology in Tokyo Bay and Ise Bay, Japan

Considerable doubt surrounds the nature of processes by which 137Cs is deposited in marine sediments, leading to a situation where 137Cs geochronology cannot be always applied suitably. Based on extrapolation with Weibull distribution, the maximum concentration of 137Cs derived from asymptotic values for cumulative specific inventory was used to re-establish 137Cs geochronology, instead of original 137Cs profiles. Corresponding dating results for cores in Tokyo Bay and Ise Bay, Japan, by means of this new method, are in much closer agreement with those calculated from 210Pb method than the previous method.     

Visualizing the Chesapeake Bay Watershed Debate

Environmental organizations often use visual material to inform society about environmental concerns and their associated policy issues. This case study examines the process by which the International League of Conservation Photographers (iLCP) and the Chesapeake Bay Foundation (CBF) use a Rapid Assessment Visual Expedition (RAVE) to draw attention to the environmental issues surrounding the Chesapeake Bay watershed. In addition, the study analyzes the resulting photographs captured during the event. The CBF and the iLCP strategically use the RAVE to create scientific and local knowledge that they use to present their understanding of the Chesapeake Bay. An analysis of the slideshows generated from the RAVE shows how the strategies the photographers employ help to depict power relations among the stakeholders in the watershed area. The strategies may encourage audiences to develop a regional collective identity of concerned citizens who will work together to help to protect and clean the watershed.     

Plutonium isotopes in surface air of Prague in 1986-2006

Monitoring of (239,240)Pu in surface air of Prague started in 1986 in connection with the Chernobyl accident. Measurable activities of 10-28muBqm(-3) were found from 29 April 1986 to 5 May 1986. In the most of the monitoring periods of 1987-1996, activities of (239,240)Pu in air were not measurable. Positive values for (239,240)Pu and (238)Pu in air could be obtained after installation of an aerosol sampler with higher flow-rate in 1997. Activity concentrations of (239,240)Pu and (238)Pu in Prague air in the most of quarters of 1997-2006 were in the range 0.53-5.06 and <0.16-1.10nBqm(-3), respectively. Seasonal fluctuations can be found in content of (239,240)Pu in air. Activity ratios of (238)Pu/(239,240)Pu in air are higher than those in top soil, so it can be supposed that (238)Pu is coming to air of Prague also from other sources than resuspension of fallout from atmospheric nuclear tests.     

234U and 238U isotopes in water and sediments of the southern Baltic

The aim of this work was to determine the concentration of 234U and 238U and calculate the values of the 234U/238U activity ratio in waters and sediments from the various regions of the southern Baltic Sea: Gdańsk Deep, S?upsk Narrow and Bornholm Deep. The concentration of uranium in analysed sediments from southern Baltic increase with core depth to what probably is connected with diffusion from sediments to water through interstitial water, where uranium concentration is much higher than in bottom water. The highest concentrations of uranium were observed in sediments of S?upsk Narrow (0.66-7.11 mg kg(-1) d.w.) and S?upsk Bank (0.61-6.93 mg kg(-1) d.w.), the lowest in sediments from Bornholm Deep (0.54-3.77 mg kg(-1) d.w.). The 234U/238U activity ratio results indicated that the sedimentation of terrigenic material and Vistula River transport are the general sources of uranium in the southern Baltic sediments. The value of 234U/238U activity ratio in sediments from reduction areas from southern Baltic (Gdańsk Deep and Bornholm Deep) indicated that reduction process of U(VI) to U(IV) and removing of anthropogenic uranium from seawater to sediments constitutes a small part only in Gdańsk Deep.     

Concentrations and activity ratios of uranium isotopes in the groundwater of the Okchun Belt in Korea.

Groundwater samples obtained from the Okchun Belt in Korea were separated into particulate and filtered fraction using a 0.45 microm membrane filter and concentrations and activity ratios of uranium isotopes in the fractions were determined by chemical separation and alpha-spectrometric measurements. Most of the uranium isotopes in the groundwater were found in the filtered water. Only less than 1% of the total uranium was detected in the particulate fraction. The concentrations and activity ratios of uranium isotopes in the groundwater measured in this study were variable, depending upon sampling site. Owing to a rapid material exchange between the subterranean hot waters and the rock strata, the concentrations of 238U in the groundwater in the hot spring area were found to be about four times higher than those elsewhere. Because of the alpha-particle recoil effect, the activity ratios of 234U/238U in the groundwater taken at "cold" spring sites were variable within the range 1.20 to 3.58, depending on the residence time of the groundwater. In the hot spring area, the activity ratios of 234U/238U were close to the equilibrium value (1.10 +/- 0.07) due to rapid erosion of the rock strata by the hot spring water.