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1.
The Canadian Certified Reference Materials Project announces the availability of reference uranium tailings sample UTS-1, -2, -3 and -4. Eighteen laboratories participated in the interlaboratory program for total iron, titanium, aluminium, calcium, barium, uranium, thorium, total sulphur, sulphate and arsenic. Eight laboratories participated in the inter-laboratory program for thorium-230, radium-226, lead-210 and polonium-210 in all four samples and for thorium-232, radium-228 and thorium-228 in UTS-1 and UTS-2. 相似文献
2.
The Canadian Certified Reference Materials Project reports recommended values of lead-210 activity in four uranium reference materials previously certified for uranium and radium-226. Eleven laboratories participated in the interlaboratory program for DL-1a, BL-4a, DH-1a and BL-5; three measurement techniques were applied. Procedural and instrumental calibrations were performed with a certified lead solution from Amersham International Corp., thereby establishing traceability of the recommended values for lead-210. Activity ratios for uranium-238. radium-226 and lead-210 demonstrate these uranium reference materials to be in secular equilibrium, within experimental uncertainties. 相似文献
3.
厦门火烧屿裸露岩石的铀放射系不平衡 总被引：2，自引：1，他引：2
用HPGeγ谱方法测定了厦门火烧屿裸露岩石天然放射性核素^40K、^228Ra、^228Th、^238U、^226Ra和^210Pb含量，对其铀系不平衡关系进行了讨论，发现钍系核素^228Ra和^228Th基本上是平衡的，而大部分样品^226Ra相对于^228U、^210Pb相对于^226Ra亏损。由此推论，水体作用下岸边岩石中^226Ra直接进入水体，可以是海水中^226Ra的一个来源；岸边岩石中^222Rn逸出后，衰变^210Pb再进入水体，可以是海水中^210Pb的一个来源。 相似文献
4.
The Canadian Certified Reference Materials Project announces recommended values for radium-226 activity in four reference materials previously certified for uranium. Thirteen laboratories participated in the interlaboratory program for DL-la, DH-la, BL-4a and BL-5. Four measurement techniques were applied. Procedural and instrument calibrations were performed with certified radium solutions from the National Bureau of Standards, thereby establishing traceability of the recommended values for radium-226 in DL-la, DH-la, BL-4a and BL-5. These reference ores are also shown to be close to, if not in, radioactive equilibrium. 相似文献
5.
Analysis of radioactive (210Pb) and stable lead isotopes in near-surface samples has been tested as a method of uranium exploration in the Pine Creek Geosyncline, Northern Territory, Australia. The lead isotopes were extracted from the samples by a mild leaching agent and were measured by alpha spectrometry for 210Pb and by mass spectrometry for stable lead isotopes. The results are compared with those obtained by conventional methods utilizing measurements of radioactivity and radon (Track Etch) in situ and 226Ra, 228Ra and U contents of soils. The major problems addressed were whether the lead isotopic methods are more sensitive than the conventional methods and whether they can discriminate “real” anomalies from the common barren anomalies found in black soils and swamps which contain radium in excess of the uranium present.Four test areas, representing a range of exploration problems, were chosen in the vicinity of the Koongarra uranium deposits and 25 samples from each area were analyzed. Most samples have more 226Ra than uranium. Radium analyses of several water samples show the source of this radium to be non-uraniferous rocks within the Kombolgie sandstone. The results for soil 226Ra, radon, scintillometry and 219Pb were generally closely correlated, and as a result, the 210Pb method was not considered to have any advantages over the conventional methods.At the Koongarra X prospect, which has a weak surface expression, the
ratio gave the strongest indication of the underlying uranium mineralization with an anomaly to background ratio of 12.5. However, this ratio is correlated with uranium content and does not offer any particular advantages over uranium analyses alone. More subtle indications of uranium mineralization were found by relating the radiogenic lead (206Pb) and the thorium-derived lead (208Pb) to the common lead content (204Pb). A plot of
versus
(horizontal axis) is linear for country rock samples, irrespective of the amount of more recently introduced 226Ra. Samples above uranium mineralization lie off this trend, along a line of near-zero slope. By the use of this plot, indications were found of the Koongarra No. 2 orebody, which is concealed by about 40 m of barren overburden; none of the other techniques detected this mineralization. 相似文献
6.
M. S. Al-Hwaiti R. A. Zielinski J. R. Bundham J. F. Ranville P. E. Ross 《中国地球化学学报》2010,29(3):261-269
Phosphogypsum (PG) is a by-product of the chemical reaction called the "wet process" whereby sul-phuric acid reacts with phosphate rock (PR) to produce phosphoric acid, needed for fertilizer production. Through the wet process, some impurities naturally present in the PR become incorporated in PG, including U decay-series radionuclides, are the main important concern which could have an effect on the surrounding environment and pre-vent its safe utilization. In order to determine the distribution and bioavailability of radionuclides to the surrounding environment, we used a sequential leaching of PG samples from Aqaba and Eshidiya fertilizer industry. The results showed that the percentages of 226Ra and 210Pb in PG are over those in the corresponding phosphate rocks (PG/PR), where 85% of the 226Ra and 85% of the 210Pb fractionate to PG. The sequential extraction results exhibited that most of 226Ra and 210Pb are bound in the residual phase (non-CaSO4) fraction ranging from 45%–65% and 55%–75%, respectively, whereas only 10%–15% and 10%–20% respectively of these radionuclides are distributed in the most labile fraction. The results obtained from this study showed that radionuclides are not incorporated with gypsum itself and may not form a threat to the surrounding environment. 相似文献
7.
210Po and 210Pb measurements of soils delineated uranium anomalies at three out of four test sites in Ontario, Canada. Measurements were made of 210Po in solutions produced by both complete digestion and partial leaching of soil samples. Direct plating of 210Po onto metal plates was followed by measuring the alpha activity. Subsequent plating of 210Po in-grown from 210Pb in solution several months later confirmed the anomalies.The 210Po and 210Pb anomalies at three of the test sites coincided with 226Ra and 222Rn anomalies. Samples from the fourth uranium occurrence associated with a known 222Rn anomaly failed to show either a 226Ra anomaly on the one hand, or 210Po or 210Pb anomalies on the other. This suggests that the 210Po and 210Pb anomalies were probably produced by the decay of 226Ra contained within secondary dispersion haloes.Although anomalies due to the 210Po and 210Pb products of 222Rn have now been documented, prospecting methods based on their use as direct tracers of the migration paths of 222Rn require much further development. 相似文献
8.
210Po and 210Pb measurements of soils delineated uranium anomalies at three out of four test sites in Ontario, Canada. Measurements were made of 210Po in solutions produced by both complete digestion and partial leaching of soil samples. Direct plating of 210Po onto metal plates was followed by measuring the alpha activity. Subsequent plating of 210Po in-grown from 210Pb in solution several months later confirmed the anomalies.The 210Po and 210Pb anomalies at three of the test sites coincided with 226Ra and 222Rn anomalies. Samples from the fourth uranium occurrence associated with a known 222Rn anomaly failed to show either a 226Ra anomaly on the one hand, or 210Po or 210Pb anomalies on the other. This suggests that the 210Po and 210Pb anomalies were probably produced by the decay of 226Ra contained within secondary dispersion haloes.Although anomalies due to the 210Po and 210Pb products of 222Rn have now been documented, prospecting methods based on their use as direct tracers of the migration paths of 222Rn require much further development. 相似文献
9.
A method is described for bringing a sediment sample into solution and subsequently carrying out analysis for 210Pb, 226Ra and 137Cs. Silica is removed from the sample by cyclic HNO3HF treatments. 137Cs is separated from 210Ra in a carbonate fusion, extracted by absorption on ammonium molybdophosphate, precipitated directly with BiI3 in presence of citric acid, and β-counted. 210Pb and 226Ra are separated out by 70–75% HNO3 precipitation. Further purification and mutual separation of the two radionuclides is achieved by solvent extraction and anion-exchange techniques. 210Pb and 226Ra are determined by β- and α- counting of their chromate precipitates, respectively, after allowing suitable ingrowth periods for their daughters. The procedural steps effectively eliminate possible interference from other natural or fall-out radioactivities. 相似文献
10.
《Chemical Geology》1992,94(3):173-181
Measurements of cosmogenic 32Si and the U-decay series' nuclides 210Pb and 226Ra in waters and sediments of lake Pavin are reported. Both 210Pb and 226Ra are enriched in the anoxic deep waters compared to the oxic surface waters, respectively by a factor of 4 and 10, whereas 32Si is depleted by a factor of2. Redox conditions in the lake appear to have no marked effect on the 32Si. Using a steady-state box model it is shown that the deep-water 32Si concentration is controlled by the underground lacustrine springs. The residence times of 210Pb, 32Si and 226Ra are1,10 and80 a, respectively. In the case of 32Si, where more data are available, the assessed inventory data from the overhead atmospheric fallout and that measured in the sediments agree very well as expected. The 210Pb- and 32Si-based deposition rates during the past100 a ranged from 0.8 to 1.9 mm a−1, earlier these were a factor of3–5 faster. The geochemistry of 32Si and 210Pb in lake Pavin in many ways resembles that in the ocean, only the time scales of the processes involved are faster. 相似文献
11.
The radon-222 (222Rn) activity in groundwater of the Apulian karstic aquifer in southern Italy is as great as 500 Becquerel per liter (Bq/L)
locally. Normal radium-226 (226Ra) activity in the limestone and calcareous dolomites of the aquifer is not enough to explain such a high level. Laboratory
investigations identified high 226Ra activity in the "terra rossa," the residuum occupying fissures and cavities in the bedrock, and also the relation between
(1) 226Ra-bearing bedrock and "terra rossa" and (2) 222Rn in water. The "terra rossa" is the primary source of the radon in the groundwater. The experimental results show the need
to characterize the "terra rossa" of Apulia on the basis of 226Ra activity and also to study the distribution and variations in 222Rn activity over time in the aquifer.
Received, January 1996 · Revised, March 1997, September 1997, June 1998 · Accepted, July 1998 相似文献
12.
13.
This study investigated the leaching of radium-226 from phosphogypsum (PG) waste produced from the fertilizer industry by synthetic solutions that replicate water that may contact the waste in natural conditions. The results indicated that the activity concentration of Ra-226 in the PG was 461 ± 12 Bq kg?1 and compared with other studies carried out worldwide. The leached percentage of Ra-226 represents the exchangeable fraction loosely bounded in the matrix of the PG waste. The leached fraction of Ra-226 was 6.5 ± 0.6 and 9.0 ± 0.5% when the waste was exposed to rainwater and saline solution, respectively. It is also found that the leaching fraction increased 10–12 ± 0.4% when the waste was exposed to the admixture of saline solution containing Sr2+ or Ba2+ cations, whereas it was lowered to 4–5 ± 0.5% in the presence of carbonate or sulfate anions. When the PG is used as an economic fertilizer, the irrigation water can leach 7.8 ± 0.6% of Ra-226 that could contribute to plant uptake, thereby to animal and/or human consumption. The primary tests of the drinking water (well and tap resources) consumed by the populations surround the PG facility showed that the activity concentration of Ra-226 was below the minimum detectable activity. 相似文献
14.
I. Vukašinović D. Todorović Lj. Životić L. Kaluđerović A. Đorđević 《International Journal of Environmental Science and Technology》2018,15(5):1049-1060
This study of environmental radioactivity was carried out in the soils of an urban area. Naturally occurring gamma-emitting radionuclides and man-made 137Cs were found in the soil profiles collected from four parks in the central Belgrade city area and the soil layer was examined every 10 cm and to a depth of 50 cm. Radioisotope activity concentrations (Bq kg?1) in the samples of urban soil using the gamma-ray spectrometry method were in the range of 14–46 for 238U, 33–50 for 226Ra, 29–63 for 210Pb, 1.2–3.4 for 235U, 28–50 for 232Th, 424–576 for 40K and 0.7–35.8 for 137Cs. Some of the basic physicochemical soil properties (pH, organic matter content, calcium-carbonate content, particle size distribution) were determined to investigate the impact on the vertical distribution of radionuclides. The results of this investigation showed that variations of activity concentration ratios of radionuclides that belong to the same (238U/226Ra) or different radioactive series (232Th/226Ra; 235U/238U), including 210Pb/137Cs ratios could well be explained by the properties of the soil. Alkaline pH reaction, the accumulation of organic matter in the uppermost and of carbonates in the deepest layers of urban soil had an effect on 238U/226Ra, and 210Pb/137Cs activity concentration ratio values, while 232Th/226Ra and partially 235U/238U ratios were associated with the particle sizes vertical distribution. A study of radionuclides in the samples of leaves of two deciduous tree species common for these parks was also conducted and 210Pb and 40K were found concentrated in leaves rather than other investigated radionuclides. 相似文献
15.
Studies by the US Geological Survey (USGS) of uranium mill tailings (UMT) have focused on characterizing the forms in which radionuclides are retained and identifying factors influencing the release of radionuclides to air and water. Selective extraction studies and studies of radionuclide sorption by and leaching from components of UMT showed alkaline earth sulfate and hydrous ferric oxides to be important hosts of radium-226 (226Ra) in UMT. Extrapolating from studies of barite dissolution in anerobic lake sediments, the leaching of226Ra from UMT by sulfate-reducing bacteria was investigated; a marked increase in226Ra release to aqueous solution as compared to sterile controls was demonstrated. A similar action of iron(III)-reducing bacteria was later shown. Ion exchangers such as clay minerals can also promote the dissolution of host-phase minerals and thereby influence the fate of radionuclides such as226Ra. Radon release studies examined particle size and ore composition as variables. Aggregation of UMT particles was shown to mask the higher emanating fraction of finer particles. Studies of various ores and ore components showed that UMT cannot be assumed to have the same radon-release characteristics as their precursor ores, nor can226Ra retained by various substrates be assumed to emanate the same fraction of radon. Over the last decade, USGS research directed at offsite mobility of radionuclides from uranium mining and milling processes has focused on six areas: the Midnite Mine in Washington; Ralston Creek and Reservoir, Colorado; sites near Canon City, Colorado; the Monument Valley District of Arizona and Utah; the Cameron District of Arizona; and the Puerco River basin of Arizona and New Mexico. 相似文献
16.
《Applied Geochemistry》2005,20(10):1965-1973
The shells of marine and fresh water mollusks can serve as effective archives in retrieving information on natural and anthropogenic environmental changes. The advantage of using bivalves is that they integrate water chemistry changes into their shells during their life span. Retrospective study of environmental changes and pollutants using bivalve shells requires precise determination of the time of incorporation into the abiotic environmental matrix (here after age) of the specimen. For the first time, a set of archived bivalve samples (for which date of the death/collection is known) has been analyzed to establish the ages of mollusk shells using the 210Pb–226Ra disequilibrium method. In addition, Sr and 90Sr were analysed. The ages obtained using the 210Pb/226Ra disequilibrium dating method agrees well with the calendar years calculated from the date of death/collection. The ages obtained can be utilized to reconstruct the 90Sr levels in the water column at sites where the mollusk shells were collected. 相似文献
17.
为了探讨近百年来,人类活动背景下近海沉积物中放射性核素的沉积记录及其对物质输入与埋藏等沉积环境变化的响应,利用γ能谱法对渤海表层和柱状沉积物中的放射性核素238U、226Ra、232Th、210Pb、40K和137Cs进行分析.结果显示,渤海沉积物中放射性核素水平和垂直分布特征明显,铀衰变系核素238U、226Ra和210Pb不平衡,232Th和210Pb受沉积物粒度和有机碳影响显著,238U与226Ra、232Th、40K存在显著相关性.226Ra/238U、232Th/238U和40K/238U比值时空差异显著,渤海沉积物陆源输入影响由西南向东北方向延伸,受河流影响,渤海北部和南部的沉积物输入不稳定,近几十年波动显著.利用210Pbex和137Cs法的测年结果计算获得的渤海近百年来沉积速率在中国近海沉积速率研究背景值范围内;空间上,渤海北部、中部和南部沉积速率处于同一水平,其中北部偏高;时间上,近百年来渤海沉积速率随时间波动,整体上呈现增加趋势,尤其是1980年之后,人类活动影响下渤海沉积速率增加幅度显著,与沉积物输入的波动变化相对应. 相似文献
18.
W. Dyck 《Journal of Geochemical Exploration》1984,20(1):85-92
Vertical profiles of 210Po in soils near the Midwest uranium deposit and an associated surficial radioactive sandstone boulder train in northern Saskatchewan show a high 210Po background in air-dried forest litter (24 pCi/g) and Ah horizon soil (11 pCi/g) relative to lower soil horizons (<1 pCi/g). These high levels mask the 210Po signal from the radioactive boulders in the near-surface soil horizons. Only in the Bf and C horizons can the existence of the radioactive boulders be inferred from 210Po determinations. For comparative purposes profiles for 226Ra, U, Ni, and other trace elements are also presented.Escape of most of the Rn from near surface soils into the atmosphere, homogenization and decay of Rn, and precipitation of decay products back onto surface soils satisfactorily explain the field observations discussed here.Compared to the highly anomalous 222Rn signal in soil gases over this boulder train the 210Po contrast is very weak and is of little use for prospecting for this type of boulder train. The relatively high 210Po background in surficial materials relative to lower soil horizons dictates that great care be taken with the 210Po method; the deepest possible horizons should be sampled. 相似文献
19.
Characterizing the dynamics of fluvial sediment sources over space and time is often critical in identifying human impacts on fluvial systems. Upland interfluve and subsoil sources of suspended sediment at Loco Bayou, Texas, were distinguished using 226Ra/232Th, 226Ra/230Th and, 228Ra/232Th. Source contributions were apportioned at three stations during within-bank and flood flows. 137Cs and 210Pbxs (excess 210Pb) were used to determine floodplain sedimentation; suspended sediment 210Pbxs/137Cs data mirrored results of Ra/Th, showing dominance of subsoil sources during within-bank flows, changing to interfluve sources during flood. This trend corresponds spatially to influx of sediment from ephemeral tributaries, reflecting mobilization of stored interfluvial sediments during flood stage. Upper basin sedimentation was similar but markedly less at the lowermost station. These results indicate (1) modified ephemeral tributaries store sediment derived from sheet wash, discharging them during flood, and (2) southernmost Loco Bayou is episodically re-worked, resulting in significantly reduced local rates of sedimentation. 相似文献
20.
Several water and surface microlayer samples from Lake St. Clair, the Niagara River, and the North Shore of Lake Ontario collected during 1983–1986 have been assayed for a variety of radionuclides. In addition, the foam accumulating in the pool just below Niagara Falls was also analyzed and found to be the most efficient aqueous phase collector of137Cs,210Pb, and226Ra.The order of radioisotope specific activities from highest to lowest is: Lake Ontario sediment, Niagara River suspended solids, Niagara River foam, surface microlayer water, and subsurface water. Radiological dose rates to the sediments from137Cs,226Ra, and228Th total about 5 mGy/y. 相似文献