The use of fallout 137Cs and 239,240Pu for dating of lake sediments

The distribution of ¹³⁷Cs and ^239,240Pu in sediment core samples of the Finnish lakes Laukunlampi, Lovojärvi and Pääjärvi were determined. The sediment samples were collected using dry ice and liquid nitrogen freezing methods. The sediments of these lakes are annually laminated. A clear maximum concentration of ¹³⁷Cs and ^239,240Pu was found in sediment layers formed during 1962–1964, the years of maximum fallout, and the middle of the 1950's can be estimated from the ¹³⁷Cs and ^239,240Pu profiles. The highest concentrations, 11 500 and 820 pCi kg^–1 dry wt for ¹³⁷Cs and ^239,240Pu, respectively, were found in the sediment of Laukunlampi. The vertical distribution was similar for ¹³⁷Cs and ^239,240Pu in the lakes investigated. A slight migration of ^239,240Pu and ¹³⁷Cs was found and the migration of ¹³⁷Cs seems to be higher than that of ^239,240Pu. The advantages of ¹³⁷Cs dating method are rapidity and simplicity. ^239,240Pu is preferable when the sample size is small. The agreement found between ¹³⁷Cs and ^239,240Pu dates and the annual laminae show that these fallout radio isotopes can be used for dating sediments formed during the past 25 years.     

Murine immunization by cesium-137 irradiation attenuated Schistosoma mansoni cercariae

Cesium-137, becoming a more readily available ionizing gamma radiation source for laboratory use, was shown to effectively attenuate Schistosoma mansoni cercariae for vaccine production. In parallel comparison studies with the murine model, cesium-137 attenuated cercariae consistently afforded better (P greater than 0.05) protection than did the cobalt-60 prepared vaccine. Dose-response data indicated that the optimal total irradiation with cesium-137 was between 45 and 50 Krad.     

Radionuclides in Foods

Levels of strontium-90 and cesium-137 in Canadian milk during the period 1960-64 were consistently higher than those in the United States or the United Kingdom, but levels in humans, while also higher, did not reflect the differences observed in milk. Annual dose rates of 27 millirads to bone and 4 millirads to the whole body correspond to the highest average concentrations of strontium-90 and cesium-137 so far observed. Levels of cesium-137 in the urine of residents of the Canadian North were found to increase with the increasing consumption of caribou or reindeer. Whole body counting of a few northern residents showed cesium-137 levels as high as 1000 nanocuries. It is concluded that protective actions are not needed but that studies in the North should be emphasized to provide a better basis for evaluating that particular situation.     

Characterization of PAH Sources in Sediments of the Thea Foss/Wheeler Osgood Waterways,Tacoma, Washington

The character of polycyclic aromatic hydrocarbons (PAH) in sediments of the Thea Foss and Wheeler-Osgood Waterways in Tacoma, Washington, were investigated with the objective of determining the general source(s) of these compounds to the waterways. In this study, 42 near-surface sediment samples from the Waterways were collected and analyzed for their (1) concentration of 43 individual or groups of PAH, (2) total extractable hydrocarbon “fingerprint” and concentration, (3) grain size and (4) total organic carbon content. Analysis of the sediment data, including comparisons to standard reference materials, indicates that all but two samples contained PAH derived from a pyrogenic source(s), i.e., a non-petroleum source(s). The high concentrations and characteristic distributions of PAH in some sediment samples were consistent with the occurrence of manufactured gas plant (MGP) derived tar(s) or tar distillate(s), particularly in some sediments proximal to a historic MGP and tar distillate storage operation near the head of the Thea Foss Waterway. Most other sediment samples throughout the Waterways contained PAH distributions and concentration indicating (at least) a greater proportion of PAH are derived from urban runoff/fallout.     

A Further Report on the Radioactive Contamination of Milk and Milk Products in Japan

In succession of the paper¹⁾ reported in 1960, the measurements of strontium-90 (Sr-90) and cesium-137 (Cs-137) concentrations in milk powder were carried out in order to investigate the extent of the later radioactive contamination of milk in Japan. Whole- and skim milk powders collected from several localities of the whole country every season from 1958 to 1962 were used for radioactivity assay. These experiments show that there is regional variation in Sr-90 and Cs-137 concentrations and Cs-137μμc/Sr-90μμc ratio in milk powder produced in Japan is higher than that of other countries.     

Interpretation of caesium-137 profiles in lacustrine and other sediments: the role of catchment-derived inputs

The caesium-137 profiles obtained in many investigations which have attempted to use caesium-137 measurements as a means of assessing the rate of accumulation of recent lake sediments, have not conformed to the classic shape expected from the record of fallout input. Such deviations have been accounted for in terms of post-depositional mobility of the caesium-137 input (e.g. bioturbation) and delayed inputs from the drainage basin. There have, however, been few attempts to determine the likely character of the drainage basin input and to analyse the role of such inputs in influencing the precise form of the caesium-137 profile. This paper presents the results of an attempt to employ existing knowledge concerning the behaviour of caesium-137 in soils and the processes of sediment mobilization to predict the likely form of the record of caesium-137 input to a lake or river floodplain from its drainage basin. The influence of this input on the profile shape will depend on the relative importance of the atmospheric fallout to the lake or floodplain surface and the drainage basin input to the total caesium-137 inventory in the sediment core, and on the land use and sediment sources in the drainage basin. By incorporating the drainage basin input into a simple model of caesium-137 accumulation in lake and floodplain sediments, it was possible to account for the profile shapes measured in four cores investigated by the authors and therefore to verify their utility for assessing rates of sediment accumulation.     

Deposition and transport of radionuclides within an upland drainage basin in mid-Wales

The deposition of radiocaesium from nuclear weapons testing and the Chernobyl accident upon the Llyn Llygad Rheidol catchment in mid-Wales is described. Inventories of soil cores from the catchment support estimates of total atmospheric fallout. The mean inventory of weapons testing ¹³⁷Cs in lake sediment cores is broadly similar to that in soil cores. The inventory of Chernobyl fallout in sediment cores is significantly lower and raises questions concerning the residence time of ¹³⁷Cs in the catchment soils and lake waters. ¹³⁷Cs and ²⁴¹Am activities in a sediment core record the 1963 peak of fallout from nuclear weapons testing. The association of the peak activities of ¹³⁷Cs and ²⁴¹Am in the sediments with the falloot maximum is confirmed by ²¹⁰Pb dating. The ²¹⁰Pb dates also reveal a significant increase in sediment accumulation rates over the past 20 years.     

137Cs as a tracer of recent sedimentary processes in Lake Michigan

To determine recent sediment movement, we measured the levels of ¹³⁷Cs (an artificial radionuclide produced during nuclear weapons testing) of 118 southern Lake Michigan samples and 27 in Green Bay. These samples, taken from 286 grab samples of the upper 3 cm of sediment, were collected in 1975 as part of a systematic study of Lake Michigan sediment. ¹³⁷Cs levels correlated well with concentrations of organic carbon, lead, and other anthropogenic trace metals in the sediment. ¹³⁷Cs had a higher correlation with silt-sized than with clay-sized sediment (0.55 and 0.46, respectively). Atmospherically derived ¹³⁷Cs and trace metals are being redistributed by sedimentary processes in Lake Michigan after being incorporated in suspended sediment. We determined a distribution pattern of ¹³⁷Cs that represents areas of southern Lake Michigan where sediment deposition is occurring.     

Radiometric dating of sediment records from mountain lakes in the Tatra Mountains

Sediment cores from nine different lakes in the Tatra Mountains, collected as part of the EU funded AL:PE, MOLAR and EMERGE projects investigating natural environmental records stored in remote mountain lake sediment sequences, were dated radiometrically by ²¹⁰Pb and ¹³⁷Cs. At five sites, D?ugi Staw G?sienicowy and Zielony Staw G?sienicowy on the Polish side of the Tatra Mountains and Starolesnianske pleso, Ni?né Terianske pleso, and L’adové pleso on the Slovak side of the Tatra Mountains, the cores were sectioned at close intervals and analysed in detail to produce a high resolution chronology. For the remaining four sites, Zmarzly Staw G?sienicowy (Poland), and Vel’ké Hincovo pleso, Vy?né Temnosmre?inské pleso, Vy?né Wahlenbergovo pleso (Slovakia), it was sufficient to establish a low resolution sketch chronology and only a few samples were analysed from each core. At L’adové pleso, multiple cores were collected in order to establish spatial distribution of sediments over the bed of the lake. Cores from all sites had good records of the fallout radionuclides from which it was possible to construct reliable chronologies of the recent sediments.     

Relations between resuspension and the content of 137Cs in freshwater fish in some Swedish lakes

In many Swedish lakes, the fallout of ¹³⁷Cs from the Chernobyl accident in April 1986 has largely accumulated in the sediments. The availability and transfer of deposited ¹³⁷Cs to biota is influenced by factors such as resuspension. The frequency of resuspension and the ¹³⁷Cs-content of different fish species was studied in three shallow lakes in Uppland, central Sweden, and in one deeper lake in northern Sweden. Resuspension was measured by the use of sediment traps. Sedimentation rates measured from the traps in the shallower lakes were 5–10 times higher than normal for this type of lake, indicating that resuspension was an important factor. The decrease of the ¹³⁷Cs-content in muscle tissue of pike, perch and roach was slow in each of the shallow lakes. ¹³⁷Cs decreased by about 30% over a period of 2 years in the shallowest lake (maximum depth 4 m), whereas ¹³⁷Cs decreased by 50% in the deeper lakes (maximum depth 10 m). The slower rates of decline of ¹³⁷Cs in biota from the shallow lakes, are probably a function of sediment dynamics (mainly influenced by lake morphometry, wind direction and strength). They may be influenced, also, by bioavailability of resuspended sediment material. In the deepest northern lake, much of the ¹³⁷Cs-containing material collected in the sediment traps originated from the catchment area. Resuspension was minimal, and the high activity of ¹³⁷Cs in the sediment had no effect on content or decline of ¹³⁷Cs in lake fish.     

Measurements of radioactivity in environmental samples from the Southern Urals

A region between Chelyabinsk and Ekaterinburg in the Southern Urals has been heavily contaminated due to operational and accidental releases from the first Soviet plutonium production facility Mayak. In 1992 and 1993, the German Federal Office for Radiation Protection organized a measuring campaign involving two Russian institutes to assist with the validation of former Soviet measurement data. The results of this measuring campaign are reported here. Environmental samples were collected from areas affected by significant radioactive releases into the Techa river, which started in 1948, and by fallout from the explosion of a fission product storage tank in 1957. Soil, sediment, water, milk and food samples were independently analysed for ⁹⁰Sr, ¹³⁷Cs and plutonium by the three institutes involved. This paper presents data on the present levels of environmental radioactivity. The highest contamination of areas accessible to the local population was found in the vicinity of the Techa river around Muslumovo. Activity concentration of floodplain samples reached up to 37 000 Bq ⋅ kg^{–1 137}Cs, 5 600 Bq ⋅ kg^{–1 90}Sr and 9.9 Bq ⋅ kg^–1 Pu. Milk and potatoes from private farms in Muslumovo showed low activity in the range from 0.7 Bq ⋅ kg^–1 to 25 Bq ⋅ kg^{–1 90}Sr. The results of the three independent measurement teams showed sufficient agreement. One Russian laboratory obtained plutonium activities that exceeded the results of the other laboratories by about 20%. Contrary to the International Chernobyl Project, there was no overestimation of ⁹⁰Sr activities in the Russian analyses. Therefore, the validity of earlier data sets acquired with same methodology and quality control can be considered a valuable basis for further assessments and for dose reconstruction in epidemiological projects. Received: 18 July 1997 / Accepted in revised form: 19 December 1997     

Effect of Chlorothiazide on Cesium-137 Excretion in Human Subjects

The therapeutic value of the diuretic, chlorothiazide (Diuril), in reducing the body burden of cesium-137 in human subjects was investigated. Two subjects were given chlorothiazide, 2 g./day, following a single oral intake of cesium-137. The urinary excretion and the per cent retention of cesium-137 were compared with similar data obtained from two control subjects. Although chlorothiazide produced a marked potassium diuresis, it had no significant effect in reducing the body burden of cesium.Analysis was made of the rate of turnover of cesium and potassium in the two control subjects, who were followed up for 320 days. The biological half-lives, T_b, of K were 42 and 41 days. In both subjects a small fraction of the cesium-137 was rapidly excreted. The remainder (88% and 83% in the two cases) was excreted at a slower constant rate. The concentrations further decreased to 44% and 41.5% in 90 and 155 days, respectively.     

Radiometrically determined dates and sedimentation rates for recent sediments in nine North African wetland lakes (the CASSARINA Project)

Sediment cores were collected from nine wetland lakes in Morocco, Tunisia and Egypt for the CASSARINA project investigating environmental change in Northern African wetlands. The cores were dated radiometrically by using natural (²¹⁰Pb) and artificial (¹³⁷Cs and ²⁴¹Am) radionuclides. At sites in Morocco and Tunisia with mean annual rainfall totals ranging from 500–1000 mm yr^–1, fallout records were generally satisfactory and it was possible to develop independent sediment chronologies based on the radiometric data alone. At the Egyptian sites, rainfall was less than 200 mm yr^–1 and fallout records were much less distinct. At these sites the radiometric data could only be used to give an indication of mean sedimentation rates during the past 30–40 years. By using a combination of fallout radionuclide, pollen, and macrofossil stratigraphic records it was however possible to determine a credible sediment chronology spanning the major part of the 20th century. Applying this chronology to records of spheroidal carbonaceous particles (SCP) from the same sediment cores, the onset of significant levels of atmospheric pollution in the Nile Delta is dated in all three cores to the mid 1950s. Results from a number of lakes (Sidi Bou Rhaba, Ichkeul and Korba) revealed high and accelerating siltation rates, threatening their continued existence beyond the next few decades. In contrast, sedimentation rates at all three Nile Delta sites appear to have declined in recent decades, most probably due to the impact of the Nile barrages.     

Joint Russian—Finnish study of radioactive contamination in the NW part of Lake Ladoga

In August 1992 a joint Russian-Finnish expedition was arranged to the NW part of Lake Ladoga to study radioactive contamination in the region. Special attention was paid to the area surrounding the Heinämaa Islands, where the wreck of the former mine carrier ship Kit had been lying about 30 years before it was moved to Novaya Zemlya in 1991. During this period the wreck had been used as a store for radioactive waste containing principally ⁹⁰Sr, ¹³⁷Cs and ^239,24OPu. Lake water, bottom sediment and some biological samples were collected for strontium, plutonium and gammaspectrometric analyses. In all the samples the radioactivity concentrations were very low, indicating radioactive contamination of about the same level as caused by global fallout in the 1960's and the Chernobyl fallout in the area. Only in two water samples taken close to the former site of the wreck slightly elevated ^239,240Pu concentrations were detected. The great water volume of Lake Ladoga and effective water exchange at the wreck site may explain the very low levels of radioactive wastes detected in the aquatic environment.     

Comparison of the post-Chernobyl 137Cs contamination of mushrooms from eastern Europe, Sweden, and North America.

A comparison was made of 134Cs and 137Cs contamination in fungi from eastern Europe and eastern North America. Mean activities of 25 Ukrainian, 6 Swedish, and 10 North American collections were 4,660, 9,750, and 205 Bq/kg (dry weight), respectively. Additional measurements were made on samples from the Moscow, southern Belarus, and Yugoslavia/Bulgaria regions. Activity values were found to vary by several orders of magnitude within all geographic areas, even for the same mushroom species. Significantly higher specific activities were observed in mycorrhizal species than in saprophytic and parasitic fungi. Unfortunately, many of the European mycorrhizal species considered as prized edibles contained unacceptably high levels of 137Cs (> 1,000 Bq/kg [dry weight]) and should be used sparingly as food. By contrast, no mushrooms collected in Ontario or northern Michigan exceeded 1,000 Bq of 137Cs per kg (dry weight). The excessive 137Cs contamination was evident in mushrooms from areas that had substantial fallout from the 1986 accident in reactor 4 at the Chernobyl nuclear power station. However, observations suggest that about 20% of the 137Cs in eastern Europe (Moscow area, Belarus, and Ukraine) is of non-Chernobyl origin.     

Ionizing Radiation and the Physician

The increasing awareness of the medical profession and the general public of the dangers associated with ionizing radiation necessitates a thorough understanding by the physician of the uses and dangers of this hazard. In addition to their application in the fields of diagnosis and therapeutic radiology, x-rays and radioisotopes are increasingly used in research laboratories and in various industries. The effects of low levels of ionizing radiation are still uncertain and it is possible that there is a “threshold” dose at which cellular damage is evident. With the increased number of atmospheric nuclear tests the concentrations of strontium-90, cesium-137, and the shorter lived isotopes such as iodine-131 in food will increase. The present levels of these isotopes do not merit concern and their early efficient removal will assure continued low fallout levels in our major food supplies.     

Radiometric dating for recent lake sediments on the Tibetan Plateau

We present radiometric data from nine lakes across the Tibetan Plateau, and compare their reliability in relation to recent research. Unsupported ²¹⁰Pb profiles show, except for one particular lake, non-exponential decline of ²¹⁰Pb activity with sediment depth. Stratigraphic dates based on global atmospheric nuclear weapons maximum fallout of ¹³⁷Cs (1963) support the use of the constant rate of ²¹⁰Pb supply (CRS) model in four of the dated cores. The discrepancy in the others is likely due to recent increased input of catchment-derived ²¹⁰Pb. ²¹⁰Pb dates in this study suggest that post depositional diffusion of ¹³⁷Cs activity has been significant. The practice of assigning early 1950s dates (start of global atmospheric thermonuclear testing) to lake sediment sequences on the Tibetan Plateau should be used with caution. ¹³⁷Cs profiles from Tibetan lake sediment cores and their geographical distribution suggest that ¹³⁷Cs derived from the 1986 Chernobyl accident or atmospheric testing in China was not sufficient to form a significant peak effective for dating.     

Radionuclide dating of the recent sediments of Blelham Tarn

Lake sediments of the last 1000 years provide a unique record of environmental changes. Methods of dating this record are reviewed and discussed. Sediments of the last 20 years, which are of particular biological significance because of their record of man-made changes in lakes (including enrichment and pollution) have been dated successfully by the distribution within them of the fallout product ¹³⁷Cs, present in the atmosphere since 1954 and reaching a peak of supply in 1963. The structured pattern shown by the curve for ¹³⁷Cs concentration in most sediments investigated indicates that faunal mixing of the surface muds does not destroy the vertical stratification of the sediment profile. Sediments up to 120 years old have been dated by a lead isotope technique, and the results of this proved consistent with both ¹³⁷Cs dating and with palaeomagnetic dating where this was possible. Theoretical considerations of the application of radiocarbon dating to organic material of 18th and 19th century date are reviewed. Results of application of these radionuclide techniques to the sediments of a small lake, Blelham Tarn, near Windermere, are presented. Evidence from ¹³⁷Cs and ²¹⁰Pb dating of profiles from several different positions within the lake shows that the depth of the annual increment to the sediments varies by a factor of × 2 from place to place. The concentration within the sediment of chemical and biological variables shows no significant variation from one position to another; therefore calculated values for amounts of each variable included within unit area of the annual increment depend primarily on the thickness of this at the site chosen, and so cannot be directly related to the rates of supply of, for example, pollen grains or total organic matter, and so to rates of productivity. Results from nine ¹⁴C dates on material 400–1000 years old, when correlated with analyses for pollen and sediment composition, demonstrate the profound effects of agricultural practices in the catchment (assumed to be deforestation and ploughing) in disturbing the orderly transfer to lake sediments of material eroded from the catchment.     

241Am dating of lake sediments

²⁴¹Am derived from decay of fallout ²⁴¹Pu is now frequently detected in analyses of lake sediments by low-background gamma assay, and offers an alternative to weapons test ¹³⁷Cs in dating recent sediments at those sites where the ¹³⁷Cs record has been degraded by post-depositional mobility or obliterated by Chernobyl fallout. Calculations of the in-growth of ²⁴¹Am from ²⁴¹Pu indicate a nominal distribution broadly similar to that of ¹³⁷Cs, with the maximum ²⁴¹Am activity occuring in fallout dating from 1963. Results from a number of sites suggest that ²⁴¹Am is significantly less mobile in lake sediments than ¹³⁷Cs, and that its distribution in cores reflects more closely the fallout record. Since further decay of existing weapons debris will increase ²⁴¹Am concentrations by about 24% over the next 40 years, ²⁴¹Am is likely to play an increasingly important role in assessing the validity of ²¹⁰Pb dates at sites with varying sediment accumulation rates.     

Biosorption of cesium-137 and strontium-90 by mucilaginous seeds of Ocimum basilicum

Mucilaginous seeds of Ocimum basilicum were used in uptake studies with cesium-137 and strontium-90. Results showed that uptake was dependent on the structural integrity of the mucilage fibrils. Water imbibed seeds showed higher adsorption of both 137Cs and 90Sr in comparison to seeds pretreated with NaOH, HCl and Na-periodate solution. The uptake was pH dependent and while some divalent metal ions had no or little detrimental effect, the alkali metal ions Li+, Na+ and K+ decreased the uptake. The maximum adsorption capacity was 160 mg cesium g(-1) and 247 mg strontium g(-1) seed dry weight.