地质样品中27项元素的粉末压片法x射线荧光光谱测定

本文报导了用x射线荧光光谱法—次粉末压片制样同时测定Na. Mg. Al. Si.P. S. K. Ca. Ti. V. Cr. Mn. Fe. Co. Ni. Cu. Zn. Rb. Sr. Y. Zr. Nb. Ba. Hf. Pb. Th. U等27项元素的快速分析方法。从理论上提出了新的基体效应学校正模式,首次引入了非荧光分析的物质(筒称NFAM)的新概念;并计算了理论α系数,使理论α系数在粉末压片法x射线荧光分析中获得了应用。本方法测定的对象可以是岩石,土壤和水系沉积物等地质样品。     

A Monte Carlo study of radon detection in cylindrical diffusion chambers

The functioning of radon diffusion chambers was studied using the Monte Carlo code RAMMX developed here. The alpha particles from radon are assumed randomly produced in the volume of the cylinder, and those from the progeny are assumed to originate randomly at the cylindrical surface. The energy spectrum, the distribution of incident angles, and the distribution of path lengths of the alpha particles on the detector were obtained. These quantities vary depending on input parameters such as initial alpha particle energy, radius and depth of the diffusion chamber, detector size and atmospheric pressure. The calculated energy spectrum for both ²²²Rn and ²²⁰Rn was compared with experiment, permitting the identification of each peak and its origin, and a better understanding of radon monitoring. Three aspects not considered in previous calculations are progeny alphas coming from surfaces of the monitor, taking into account the atmospheric pressure, and including the isotope ²²⁰Rn.     

Releases of phosphate fertilizer industry in the surrounding environment: Investigation on heavy metals and polonium-210 in soil

Distribution of Cu,Zn,Pb,Cr,Ni,Mn concentrations and the activity of polonium-210 in the surrounding area of a phosphate fertilizer industry located on the eastern coast of the Mediterranean Sea has been determined.Nineteen sampling sites were distributed around the industrial zone on a surface area of about 100,000 m2.Atomic absorption spectroscopy and Alpha spectroscopy were used to quantify the heavy elements and polonium-210,respectively.Investigation on a particle scale was conducted by TEM and SEM coupled to EDX and X-ray cartography to determine the nature of heavy elements carriers and their distribution.Heavy elements were mainly concentrated inside the particle size fraction 50 μm.Their levels decreased with distance increasing from the industry.According to the reference soil,enrichment factors were about 10,15,32 and 100 times for Zn,Pb,Cu,and Cr,respectively inside the particle size fraction 50 μm on the closest sites to the industry.The main contaminant sources were transport and storage of row materials and the free release of phosphogypsum waste.Heavy elements were entrapped inside agglomerates of sulfates,phosphates and iron oxihydroxides in a di used shape.Polonium-210 with an enrichment factor of about 56,showed the same behavior of the spatial distribution of the trace elements.     

Amniotic fluid-AFP in Down syndrome and other chromosome abnormalities

80·2 Per cent of 111 Down syndrome pregnancies had amniotic fluid (AF) alpha fetoprotein (AFP) levels on or below the median and 10·8 per cent at or below 0·5 MoM compared with 41·9 and 1·4 per cent of controls. These differences were even more striking when the gestational age was < 18 weeks compared with ⩾ 18 weeks. No such association was seen for other chromosome abnormalities including trisomy 18,45,X and mosaics, 47,XXY, 47,XXX, and other structural abnormalities and triploidy, even when high levels due to defects such as omphalocele and cystic hygroma were excluded. All cases of trisomy 13 and 80 per cent with 47,XYY had AF-AFP levels above the median. Selection of cases for karyotyping by a low level of AF-AFP would clearly fail to detect aneuploidies other than Down syndrome and is not recommended. A possible weak association between low maternal serum (MS) and AF-AFPs in Down syndrome was most evident at < 18 weeks, suggesting that MS screening between 16 and 18 weeks may be the most informative time.     

Fractionation of natural radionuclides in soils from the vicinity of a former uranium mine ?irovski vrh, Slovenia

As a result of former uranium mining and milling activities at ?irovski vrh, Slovenia, 0.6 million tons of uranium mill tailings (UMT) were deposited onto a nearby waste pile Boršt. Resulting enhanced levels of natural radionuclides in UMT could pose threat for the surrounding environment. Therefore, sequential extraction protocol was performed to assess mobility and bioavailability of ²³⁸U, ²³⁴U, ²³⁰Th and ²²⁶Ra in soils from the waste pile and its surrounding. The radionuclides associated with exchangeable, organic, carbonate, Fe/Mn oxides and residual fraction, respectively, were determined. Results showed that the highest activity concentrations for the studied radionuclides were on the bottom of the waste pile. In non-contaminated locations, about 80% of all radionuclides were in the residual fraction. Considering activity concentrations in the UMT, ²³⁸U and ²³⁴U are the most mobile. Mobility of ²²⁶Ra is suppressed by high sulphate concentrations and is similar to mobility of ²³⁰Th.     

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.     

Amniotic fluid enzymes in pregnancies with trisomy 21

The activities of a range of microvillous enzymes in amniotic fluid from normal pregnancies (n = 213) and those complicated by trisomy 21 (n = 26) were compared in a prospective study. Using a centrifugal analyser, the activities of leucine aminopeptidase (LAP), gamma glutamyl transferase (GGT), aspartate transferase (AST), and isoenzymes of alkaline phosphate (ALP) were measured in amniotic fluid alongside alpha fetoprotein (AFP) levels. Of the markers studied, LAP was found to be the most reliable indicator of trisomy 21. Using levels below the 5th percentile, LAP showed sensitivity 73 per cent, specificity 94 per cent, and predictive value positive 63 percent. Although these tests would not replace karyotyping in all cases, the measurement of LAP could be useful as a rapid initial screening test, particularly when amniocentesis is performed for indications other than chromosomal abnormalities.     

Po determination in urines of people living in Central Italy

This paper presents the results of the monitoring programme on the urines of people living in an area of Central Italy (near the Republic of S. Marino) to evaluate the background level of the ²¹⁰Po excretion rate (mBq day⁻¹) in this region. The volunteers were subdivided in five age classes and in every age class groups of males and females, cigarette smokers and non-smokers were taken into account. The results indicated that the ²¹⁰Po excretion rate was widely distributed within each group of volunteers. The ²¹⁰Po excretion rate was <30 mBq day⁻¹ for 93.2% of people. The obtained results are discussed and some conclusion, based upon the average values, was drawn.     

Spatial distribution of U isotopes in sea-water sediments, Red Sea, Egypt

Isotopes of uranium in the sea-water sediments collected from two different areas (El Hamraween harbour and Ras El Behar) on the Egyptian coast of the red sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of ²³⁸U, ²³⁵U, ²³⁴U were calculated. The activities observed indicated enhanced radioactivity levels in sea-water sediments of El Hamraween harbour area due to the activities of phosphate shipment operation. Secular equilibrium between ²³⁴U and ²³⁸U was found in the analyzed samples. The average activity ratio of ²³⁵U/²³⁸U was close to the value 0.046 for uranium in nature.     

Exerpts from the history of alpha recoils

Any confined air volume holding radon (²²²Rn) gas bears a memory of past radon concentrations due to ²¹⁰Pb (T_1/2 = 22 y) and its progenies entrapped in all solid objects in the volume. The efforts of quantifying past radon exposures by means of the left-behind long-lived radon progenies started in 1987 with this author’s unsuccessful trials of removing ²¹⁴Po from radon exposed glass objects. In this contribution the history and different techniques of assessing radon exposure to man in retrospect will be overviewed. The main focus will be on the implantation of alpha recoils into glass surfaces, but also potential traps in radon dwellings will be discussed. It is concluded that for a successful retrospective application, three crucial imperatives must be met, i.e. firstly, the object must persistently store a certain fraction of the created ²¹⁰Pb atoms, secondly, be resistant over decades towards disturbances from the outside and thirdly, all ²¹⁰Pb atoms analysed must originate from airborne radon only.For large-scale radon epidemiological studies, non-destructive and inexpensive measurement techniques are essential. Large-scale studies cannot be based on objects rarely found in dwellings or not available for measurements