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     

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.     

Depleted uranium mobility and fractionation in contaminated soil (Southern Serbia)

GOAL, SCOPE AND BACKGROUND: During the Balkan conflict in 1999, soil in contaminated areas was enriched in depleted uranium (DU) isotopic signature, relative to the in-situ natural uranium present. After the military activities, most of kinetic DU penetrators or their fragments remained buried in the ground in certain geomorphological and geochemical environments exposed to local weathering conditions. The contamination distribution, mobility and/or fixation of DU in the contaminated soil profile at one hot spot were the subject of our study. The results should disclose what happened with released DU corrosion products in three years elapsed, given the scope of their geochemical fractionation, and mark out the most probable host substrates in investigated soil type. METHODS: Gamma-spectrometric analysis of soil samples taken in the DU penetrator impact-zone was done to obtain present contamination levels. Set of samples is subjected to five-step and three-step sequential extraction procedures, specifically selective to different physical/chemical associations in soil. The stable elements are determined in extracts by the atomic absorption spectroscopy. After the ion-exchange based uranium separation procedure, alpha-spectrometric analysis of obtained fractions was done and DU distribution in five extraction phases found from 235U/238U and 234U/238U isotopic ratios. RESULTS: Depleted uranium concentration falls down to the 1% of the initial value, at approximately 150 mm distance to the source. Carbonates and iron/manganese hydrous oxides are indicated as the most probable substrates for depleted uranium in the characterized soil type. Therefore, in the highly contaminated soil samples, depleted uranium is still weakly bonded and easy exchangeable. The significant levels of organic-bonded depleted uranium are found in surface soil only. DISCUSSION: Dependence of the fractionation on the contamination levels is evident. Samples with higher DU contents have shown a longer maintenance in the exchangeable phases, probably because adsorption/desorption mass transfer through the medium was not very fast. Organic-bonded, depleted uranium is present in surface soil samples due to its higher humus content. Considering geochemical composition of investigated soil, the indicating chemical associations as substrates are in agreement with some considerations based on the results for low-level waste unsaturated zones. CONCLUSIONS: The soil contamination with depleted uranium in investigated area is still 'spot' type and not widespread. Dependence of the fractionation on the contamination levels and presence of weakly bonded, depleted uranium in the hot spots areas is evident. RECOMMENDATIONS AND PERSPECTIVES: A detailed study may be undertaken with suitable extractive reagents to define a bio-available fraction of depleted uranium in soil. The comparison of results for different soil types investigated by the same methodology may be useful. An applied combination of physical/chemical procedures and analysis may help in the decision making on the remediation strategy for sites contaminated with depleted uranium used in military operations.     

岩矿样品X射线荧光分析中多元素体系理论α系数的计算和应用

本文提出了岩矿样品X射线荧光分析中多元素体系的理论α系数的一种计算方法。假设试样由n个组分组成,其各组分平均含量为Cl(Cl=1,2,3,…k,……n),然后,假设某一组分的含量Cl相对于平均含量Cl有一微小变化量ΔC,并使每个组分相应变化一次,用基本参数法方程计算理论X射线相对强度;再按一定的数学模式计算相应的基本α系数,混合α系数和修正α系数。以实例计算了用于地质样品分析的各种理论α系数,应用于实际分析中结果令人满意。     

Amniotic fluid gel acetylcholinesterase determination in prenatal diagnosis: Dark field illumination as a method for improving the detection of precipitation bands

This paper describes a sensitive method for the detection of precipitation bands in the qualitative acetylcholinesterase (AChe) gel test. This method–dark field illumination–is compared with two existing methods of detection: epi-illumination of unstained gels and transillumination of dithio-oxamide stained gels. The comparison has been carried out on a selected series of 271 amniotic fluid samples, taken before the 22nd week of gestation. All 96 samples from normal pregnancies were scored as negative with all three visualization methods. For the detection of neural tube defects (NTD) and omphaloceles, dark field illumination proved to be more efficient than epi-illumination or dithio-oxamide staining. In one case of another congenital defect, we obtained a positive result with dark field illumination, and a negative one with the other detection methods. It is concluded that dark field illumination was shown to be the most sensitive method for the detection of precipitation bands.     

The impact of maternal serum alpha fetoprotein screening on open neural tube defect births in North-East Scotland

Over the three years period 1980–1982, 18 256 pregnancies in the Grampian Region of N-E Scotland including the islands of Orkney and Shetland were screened for raised levels of maternal serum alpha fetoprotein (MSAFP) in the second trimester. Thirty six cases of fetal open neural tube defect in singletons were detected (18 anencephaly and 18 spina bifida). Four additional cases of open spina bifida were associated with normal MSAFP levels although two of these were detected by amniotic fluid AFP measurement when amniocentesis was carried out because of previous NTD history. A further three cases of open spina bifida and two of anencephaly occurred in unscreened pregnancies. The MSAFP screening programme alone was thus instrumental in reducing the birth incidence of open neural tube defects by 36 out of 45 cases (80 per cent) in singletons.     

材料声学特性的典型参数测试技术研究进展

吸声系数和隔声量是描述材料声学特性的典型参数,首先分析了材料吸声系数和隔声量测试技术的研究意义,指出提高材料吸声系数和隔声量测试技术符合我国先进武器装备的发展需求。梳理了国内外吸声系数和隔声量的主要实验室测试方法及标准,具体介绍了阻抗管法、混响室法、Alpha舱法测量材料吸声系数,阻抗管法、混响室-混响室法、混响室-消声室法、Alpha舱法测量材料隔声量的研究进展,分析了各种测试方法的优缺点,最后展望了该领域的发展趋势。     

Releases of phosphate fertilizer industry in the surrounding environment: Investigation on heavy metals and polomum-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 carders and their distribution.Heavy elements were mainly concentrated inside the particle size fraction ＜ 50μm.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 diffused shape.Polonium-210 with an enrichment factor of about 56,showed the same behavior of the spatial distribution of the trace elements.