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1.
采集康平、沈北、东梁、辽阳、阜新、浑江、舒兰、海拉尔、珲春、凉水、七台河共11处煤矿样品，设置了燃烧试验，使煤在近密闭燃烧炉中燃烧，杜绝飞灰造成的物质损失，然后测定煤及其对应灰分的 238U、 232Th、 226Ra、 40K活度.分析得出：在理论燃烧状态下，假设燃烧无飞灰产生，煤灰的 238U、 232Th、 226Ra、 40K天然放射性核素富集因子 f与煤灰分比 Ad的乘积为1.根据煤燃烧后核素的迁移富集规律和影响辐射水平的核素权重，提出了应用于煤的比活度、吸收剂量率、年吸收剂量、内辐射指数等放射性环境评价参考值.经11处煤矿验证，评价结果可以反映煤灰的辐射水平，辐射水平排序与实际测量结果基本一致. 相似文献
2.
采集康平、沈北、东梁、辽阳、阜新、浑江、舒兰、海拉尔、珲春、凉水、七台河共11处煤矿样品,设置了燃烧试验,使煤在近密闭燃烧炉中燃烧,杜绝飞灰造成的物质损失,然后测定煤及其对应灰分的 238U、 232Th、 226Ra、 40K活度.分析得出：在理论燃烧状态下,假设燃烧无飞灰产生,煤灰的 238U、 232Th、 226Ra、 40K天然放射性核素富集因子 f与煤灰分比 Ad的乘积为1.根据煤燃烧后核素的迁移富集规律和影响辐射水平的核素权重,提出了应用于煤的比活度、吸收剂量率、年吸收剂量、内辐射指数等放射性环境评价参考值.经11处煤矿验证,评价结果可以反映煤灰的辐射水平,辐射水平排序与实际测量结果基本一致. 相似文献
3.
通过对青岛市1500km^2范围内大密度土壤放射性核素（^238U、^232Th和^40K）和地表γ辐射测量,系统深入地研究了其放射性特征、分布规律及其影响因素。结果表明,青岛市土壤中核素^232Th和咏的放射性比活度偏高,而^238U偏低。地表γ辐射吸收剂量率（平均值91．87nGy·h^-1）略高于全国和世界平均值,研究发现地表93．14％的γ辐射来自地面放射性核素^238U、^232Th和^40K）的．γ辐射,其中^232Th和^40K的贡献占81．21％,是主要的贡献者。地质背景是影响地面γ辐射吸收剂量率的主要因素,燕山期各类花岗岩是导致青岛市区-王哥庄-带γ辐射吸收剂量率偏高的主要原因;同时环境因素（路面材料、地貌景观）对地表γ辐射吸收剂量率也存在一定影响。虽然研究区的γ辐射吸收剂量率较高,但其年有效剂量（0．56 mSv）远低于公众照射年剂量当量限值1.0 mSv,人居环境基本不受影响。 相似文献
4.
通过对煤田钻孔天然伽玛测井资料的二次解译,发现辽宁省内部分煤田含煤岩系存在放射性异常.筛查钻孔3437个,发现异常孔841个,其中与煤层相关的异常钻孔49个,异常值为50~123γ,个别钻孔异常峰值高达260 γ.采集康平、蒲河等5处煤矿原煤作为分析对象,对5处煤矿原煤样品和燃烧后的煤灰进行分析,确定 238U、 232Th、 226Ra、 40K、 210Pb、 210Po在燃烧后迁移的比例及其影响因素. 238U、 232Th、 226Ra、 40K、 210Pb元素在煤/灰活度比与煤燃烧后灰分比对比结果显示两者相近,表明元素在燃烧过程中未发生挥发及化学反应,元素含量几乎全部富集于灰分中;而 210Po元素煤/灰活度比与煤燃烧后灰分比相差较大,认为在煤的燃烧过程中Po易以气态形式迁移到空气中.因此应重视与煤炭开采利用直接相关含煤岩系的放射性异常,避免对环境产生放射性污染. 相似文献
5.
对长约70 km引水工程洞线上进行的地面伽马能谱测量、陆地伽马剂量率测量、土壤氡浓度测量、岩石表面氡析出率测量以及钻孔岩芯样品的放射性元素U、Ra、Th、K含量分析的综合放射性地质调查,并对获得的测量数据进行分析研究。结果表明,测区引水沿线地质体放射性核素当量含量平均值为：U 1.56×10-6,Th 14.12×10-6,K 2.16×10-2;钻孔岩芯放射性元素分析含量平均值为：U 32.34 Bq/kg,Ra 35.68 Bq/kg,Th 35.29 Bq/kg,K 865.65 Bq/kg。陆地伽马剂量率为90.42 nGy/h;土壤氡浓度平均值为4 272.1 Bq/m3;岩石表面析出率平均值为4.01×10-2 Bq/m2·s。根据测量结果,利用内照射和外照射辐射剂量计算了对施工人员造成的辐照剂量为0.759 mSv,低于国家对公众的剂量限值1 mSv/a,表明引水工程输水隧洞的施工在安全辐射范围内。 相似文献
6.
对青岛市1 500 km 2范围内大密度土壤放射性核素和地表γ 辐射测量,系统深入研究了其放射性特征、分布规律及其影响因素。结果表明,青岛市土壤中核素232 Th 和40 K 的放射性比活度偏高,而238U 偏低。地表γ 辐射剂量率( 平均值91. 87 nGy /h) 略高于全国和世界平均值。研究发现,地表 93. 14%的γ 辐射来自地面放射性核素238U、232 Th 和40K 的γ 辐射,其中232 Th 和40K 的贡献占81. 21%,是主要的贡献者。地质背景决定地面γ 辐射剂量率值,燕山期各类花岗岩是导致青岛市区-王哥庄一带γ 辐射剂量率偏高的主要原因; 同时环境因素( 路面材料、地貌景观) 对其剂量率也存在一定影响。虽然研究区的γ 辐射剂量率较高,但其年有效剂量( 0. 56 mSv) 低于公众照射年剂量当量限值 ( 1. 0 mSv) ,人居环境基本不受影响。 相似文献
7.
利用γ能谱仪对阿坝州壤塘地区的天然放射性核素进行了现场测量,计算了内、外照射指数、γ照射量率和γ外照射有效剂量,并对该地区进行了天然放射性水平评价。研究结果显示,该地区γ照射量率平均值(100.07Gy/h),高于全国(81.5nGy/h)和世界(80nGy/h)的平均值,但内、外照射指数、γ照射量率和γ外照射有效剂量都在国家限量标准控制的范围内。由于地表水对放射性元素具有富集和运移作用,所以在断裂带附近的放射性水平相对偏高。目前,壤塘地区的天然放射性水平在安全的范围内,适合人类的居住和生活。 相似文献
8.
以1∶25万化探数据为切入点,在分析全国各城市天然放射性水平特征的基础上,运用放射性填图评价技术研究了成都平原天然放射性水平分布特征。结果表明:研究区环境天然放射性核素238 U、232 Th、40 K含量频数均呈正态分布,数值均在正常本底范围内;238 U比活度总体上低于全国平均水平,232 Th和40 K比活度总体上高于全国平均水平;研究区天然放射性辐射水平、γ射线照射量率、吸收剂量率、年有效剂量当量均低于世界和全国的平均水平;研究区γ射线内、外照射指数均在国家限量标准控制范围之内。 相似文献
9.
近几年国际陨石市场发展迅速,陨石类饰品以不可替代的独特优势备受公众瞩目,多数消费者普遍存在陨石辐射危害人体健康的误解和疑虑。本文通过针对性测试可作为饰品原材料的铁陨石、橄榄陨铁、普通球粒陨石和玻璃陨石的块体样品,以及普通球粒陨石粉末样品的放射性元素( 226Ra、 232Th和 40K)比活度,获得这些样品的放射性比活度数据。结果表明,所检测陨石样品的放射性比活度和内外照辐射指数(I Ra和I γ)均低于人体皮肤放射性安全标准,同时低于和田玉和祖母绿等传统宝玉石;而玻璃陨石的放射性比活度略高于作为对比的宝玉石,但低于人体安全标准。通过对所检测样品的矿物组合和化学组成等指标对比分析,认为陨石中具有高浓度放射性元素的矿物含量极低,宇宙射线不能导致陨石放射性增加,玻璃陨石相对较高的放射性比活度主要由源区岩石中残留含高放射性元素矿物引起。 相似文献
10.
本次研究基于地表 γ辐射剂量率、氡放射性测量及 238U、 232Th、 226Ra、 40K放射性核素测试,识别华东地区含煤岩系的放射性异常地层,评价区域典型煤矿区空气、固体、水体、植物介质的天然放射性水平。结果显示：赋存于石炭系、二叠系的普通煤田与赋存于寒武系的石煤矿区呈现显著差异的天然放射性水平。普通煤田矿区地表 γ辐射剂量率、氡放射性测量值总体上处于本底水平范围,矿区固体介质、水体、植物样品核素含量处于正常水平,不存在放射性污染。华东地区石煤分布带,属于放射性 γ辐射高背景区,石煤矿区的原煤、煤矸石、土壤、岩石等固体介质的 238U、 226Ra核素富集明显,并显示更为显著的空间变异性。区域石煤条带监测矿区居民源于 γ外照射引起的吸收剂量均超过国际标准限值1 mSv/a,总有效剂量均超过了2 mSv/a,地下水总 α、总 β浓度为限值的10~30倍,放射性污染不容忽视。华东地区石煤矿区公众所受辐射剂量较高,矿区的地下水、建材、植物等介质已经出现零星的放射性污染,应加强石煤矿区放射性环境监测,及时采取适当的控制措施。 相似文献
11.
We have investigated the banded coral Montastrea annularis as a recorder of the history of fallout Pu in surface seawater. Thirty annual growth bands, representing growth during ‘coral years’ 1951–1980, were subsampled from M. annularis collected at St. Croix, U.S. Virgin Islands. ‘Coral years’ begin and end in late summer-early autumn and are designated for the calendar year in which they end. 239,240Pu was finite in coral years 1954–1980, and the coral Pu record is very simply related to the fallout history of 90Sr. Peaks in coral Pu in coral years 1959 and 1964 correspond to fallout peaks in 1959 and 1963, respectively. Peak broadening and time lags in the coral Pu record, as compared to the 90Sr fallout record are consistent with retention of fallout Pu in surface seawater for about two years (characteristic removal time) during the period of major fallout, and possibly longer thereafter. The simplicity of the coral Pu record and its close correspondence with fallout history suggest that 239,240Pu was incorporated into the coral skeleton with constant discrimination relative to Ca; the effects of speciation and oxidation state upon Pu incorporation are presently unknown. To aid the Pu interpretation Ca, Mg, Sr, Na and natural radionuclides (238U, 228Ra, 232Th and 210Pb) were also determined in the annual bands. In small samples (0.5 g) Ca, Mg and Na show correlated variations which could be due to seasonal variability in uptake. The 238U and 228Ra records were generally consistent with uptake, at constant discrimination, from surface-water reservoirs of nearly constant concentration, although one sample showed probable diagenetic addition of U. 232Th was not detected with certainty; this implies that terrigenous particles were not consistently entrapped within the coral skeleton. Interpretation of 210Pb was difficult because 226Ra was not measured. Montastrea annularis preserves a record of fallout Pu. To make this record useful it must be considered in the broadest possible geochemical context. 相似文献
12.
Relatively high activity concentrations of some radionuclides ( 226Ra, 238U, 232Th, and 40K) have been measured in surface and subsurface soils in areas (southern Iraq) where many warfare actions have taken place during the Iran–Iraq and Gulf wars. Such high activity concentrations might be related to the increase in cancerous injuries and birth defects recently reported. The study was aimed to estimate the activity concentrations of some nuclides and a comparison of results with international health hazard indices. In addition, the excess lifetime cancer risk (ELCR) was assessed. Soil samples were collected at three depths (0, 30, and 60 cm) in three locations in Abu Al Khasib and Ad Dayr in Basrah governorates. The average activity concentrations were estimated employing hyper-pure germanium HPGe gamma-ray detection technology. The values obtained in Abu Al Khasib were: 58.44 Bq/kg ( 226Ra), 43.56 Bq/kg ( 238U), 19.38 Bq/kg ( 232Th), and 321.76 Bq/kg ( 40K) whereas in Ad Dayr 45.71 Bq/kg ( 226Ra), 35.53 Bq/kg ( 238U), 20.33 Bq/kg ( 232Th), and 337.02 Bq/kg ( 40K). According to UNSCEAR (Sources and effects of ionizing radiations: a report on the effects of atomic radiation to the general assembly with scientific annexes, Annex B, United Nations, New York, 2000) report, higher levels of 226Ra, 238U concentrations than the world’s average values (35 Bq/kg) were observed in both locations. In addition, some radiation hazard indices were determined for both locations: average outdoor external dose ( D out), average indoor external dose ( D in), total average value of the external dose ( D tot), average annual outdoor effective dose ( E out), average annual indoor effective dose ( E in), and averaged total annual effective dose ( E tot). Values for D tot and E tot were higher than the worldwide median (143 nGy/h and 0.48 mSv/y, respectively) in both regions. The measured values of activity concentrations were also used to estimate the outdoor, indoor, and total ELCR. The ELCR values were higher than the worldwide averages. Further analyses and studies need to assess the real risks for human health and possible soil remediation. 相似文献
13.
Monazite [(LREE)PO 4], a common accessory mineral in magmatic and metamorphic rocks, is complementary to zircon in U–Th–Pb geochronology. Because the mineral can record successive growth phases it is useful for unravelling complex geological histories. A high spatial resolution is required to identify contrasted age domains that may occur at the crystal-scale. Bulk mineral techniques such as ID-TIMS, applied to single monazite grains recording multiple overgrowths or isotope resetting can result in partly scattered discordant analytical points that produce inaccurate intercept ages. Laser ablation (LA)-ICPMS has been demonstrated to be a useful technique for U–Th–Pb dating of zircons, and this study tests its analytical capabilities for dating monazite. A sector field high resolution ICPMS coupled with a 193 nm ArF excimer laser ablation microprobe is capable of achieving a high spatial resolution and producing stable and reliable isotope measurements. The U–Th–Pb systematic was applied to monazite grains from several samples: a lower Palaeozoic lens from high-grade terrains in Southern Madagascar, Neogene hydrothermal crystals from the Western Alps, a Palaeoproterozoic very high temperature granulite from central Madagascar and a Variscan leucogranite from Spain, directly on a polished thin section. The major aim was to compare and/or reproduce TIMS and EMP ages of monazite from a variety of settings and ages. The three independent 206Pb/238U, 207Pb/235U and 208Pb/232Th ratios and ages were calculated. Isotope fractionation effects (mass bias, laser induced fractionation) were corrected using a chemically homogeneous and U–Pb concordant monazite as external standard. This study demonstrates that excimer laser ablation (ELA)-ICPMS allows U–Th–Pb dating of monazite with a high level of repeatability, accuracy and precision as well as rapidity of analysis. A spatial resolution almost comparable to that of EMP in terms of crater width (5 μm) produced precise 208Pb/232Th, 206Pb/238U and 207Pb/235U ratios for dating Palaeozoic to Precambrian monazites. The advantages of (ELA)-ICPMS isotope dating are precision, accuracy and the ability to detect discordance. In the case of late Miocene hydrothermal monazites from the Alps, a larger spot size of 25 μm diameter is required, and precise and accurate ages were obtained only for 208Pb/232Th systematics. Results from the Variscan granite show that in situ U–Th–Pb dating of monazites with (ELA)-ICPMS is possible using a 5 μm spot directly on thin sections, so that age data can be placed in a textural context. 相似文献
14.
对矿石中放射性核素的含量组合与岩石含矿量进行相关性分析,进而指导锂铍稀土矿资源勘查工作.采用ENVI Pro型质子磁力仪和ARD型多道伽玛能谱仪,对茶卡北山地区花岗伟晶岩脉进行磁性特征测量和放射性特征测定,确定238U、232Th、40K含量分布规律和异常位置,划分含矿岩体,提取信息并进行磁异常和放射性元素含量的相关性... 相似文献
15.
A large number of calcrete samples from topsoils of the Doukkâli area, western Morocco, were studied by U-disequilibrium series methods. The 230Th/ 234U ages are rather uniformly distributed between>350 and 2 ka BP. Homologous samples for occurrence and structure display quite different ages, the 230Th/ 234U ages are considered apparent. This is explained by repeated deposition of secondary calcite in the calcrete pores, which caused lowering of the original ages. However, the apparent ages may be considered minimum ages of the calcrete formation, indicating that calcium carbonate mobilization and deposition has been taking place repeatedly since >350 ka. The age range obtained is quite comparable with that of calcretes from southern Spain, suggesting similar conditions for the calcrete formation in the two areas. 相似文献
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