Effect of alteration processes on the distribution of radionuclides in uraniferous sedimentary rocks and their environmental impact, southwestern Sinai, Egypt

The contents of natural radionuclides in various types of sedimentary rocks in Um Bogma Formation and base of El Hashash Formation were determined by gamma-ray spectrometry. Three types of lower Carboniferous sedimentary rocks were investigated; sandstone (El Hashash Formation), dolostone and argillaceous sediments (Um Bogma Formation). The alteration processes are dolomitization, dedolomitization, karstification and lateritization. The specific radioactivity of ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K determined in different samples, indicate that ²³⁸U and its decay products contribute primarily to the high natural radioactivity of rocks. The maximum concentration of ²³⁸U reached up to 2129.36 ppm in argillaceous sediments. The average concentrations of determined radionuclides (²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K) are 8.34 ppm, 7.88 ppm, 4.68 ppm and 0.3%, respectively in sandstone. In dolostones the average concentrations are 418.69 ppm, 808.75 ppm, 3.14 ppm and 0.29%, respectively. For argillaceous sediments are 276.88 ppm, 419.49 ppm, 11.47 ppm and 0.93%, respectively. The ²³⁸U/²²⁶Ra ratio in sandstone ranges between 0.89 and 1.25, while in dolostones and argillaceous sediments are 0.27–2.63 and 0.27–1.83, respectively. These variations in the concentrations of radioelements and their ratios are due to the action of the alteration processes affected these different sedimentary rocks in different times. Environmentally, the Ra_eq in dolostones and argillaceous sediments exceeds the permitted limits, while in the sandstone samples; it is within the permissible levels.     

Determination of lead in carbonate rocks by carbon-furnace atomic-absorption spectrometry after dissolution in nitric acid

A simple and rapid method for the determination of 1-100 ppm of lead in carbonate rocks is described. Dissolution of the rock samples in 10% v v nitric acid is shown to give precise and accurate results even though silicates in the samples remain undissolved. A more time-consuming but complete dissolution of the sample with hydrofluoric acid may be used if preferred. The increase in sensitivity and freedom from matrix interference obtained by the use of a carbon-furnace atomizer eliminate the necessity for preconcentration of the lead, saving time and preventing errors from contamination or losses derived from inefficient extraction procedures. The detection limit and precision of the method are 0.4 ppm and 6% (relative standard deviation at the 3-ppm lead level) respectively and accurate results were obtained for the analysis of standard rock samples.     

Extraction and neutron activation analysis of humic substances

Methods are described for the isolation of humaic substances from a soil samples. The produres and based on extractions with sodium hydroxide or sodium pyrophosphate. Four of the humic samples were dried and then analysed by thermal neutron activation analysis. The humic samples along with three standard rocks were irradiated for 15 hours in a flux of 10¹² n·cm^–2·s^–1. Counting was carried out using both a large volume Ge(Li) detector and a high resolution LEP detertor. Quantitative analysis was based on the known element concentrations in the standard rocks. The elements determined were Sc, Cr, Fe, Co, As, Se, Br, Mo, Sb, La, Ce, Eu, Hf, Ta, Th, and U. concentrations ranged from 0.02 ppm (La) to 7900 ppm (Fe).     

A direct method for the determination of carbonate and non-carbonate carbon in geological materials by infrared spectrometry

A simple and direct infrared method for determining carbonate and non-carbonate carbon in geological samples is described. To determine carbonate carbon, hydrochloric acid is added directly to the heated samples; non-carbonate carbon is determined by combustion after digesting the samples with hydrochloric acid. The limit of detection is 2 ppm for carbonate carbon and 10 ppm for non-carbonate carbon; the relative standard deviations are 4% or less for 100–1000 μg of carbonate and non-carbonate carbon. The method has been applied to standard rocks, NBS minerals and geological exploration reference samples.     

Spectrophotometric determination of trace amounts of beryllium in silicate materials

Although photometric determination of beryllium is generally quite satisfactory in trace analysis, application to geochemical samples is restricted because of the numerous interfering ions. Introduction of an extraction procedure eliminates the interference of Al and Fe, which occur in high concentrations in most silicate rocks, and enables beryllium to be determined with Eriochrome Cyanine R. Use of the method for analysis of six international geochemical reference samples containing between 1 and 30 ppm beryllium has given satisfactory results (relative standard deviation from 1.6 to 7.8%).     

Screening nitrate in forages with a test strip: collaborative study

A collaborative study was conducted for screening nitrate in forages with a commercially available test strip. The method involves extracting a finely ground sample with deionized water. The test strip is dipped in the sample extract. The color of the reaction zone on the test strip changes from white to pink or purple depending on the nitrate concentration in sample extract. The nitrate present in the extract is determined by comparing the color of the test strip to the color scale on the test strip container. Six blind quintuplicates of forage samples were analyzed by 20 collaborators. Nitrate concentrations in forage samples tested ranged from < 1000 ppm nitrate to > 10,000 ppm nitrate on dry matter basis. Each collaborator was asked to assign each sample to one of the 4 following nitrate concentration ranges: (1) < 1000 ppm, (2) 1000 to 5000 ppm, (3) > 5000 ppm to 10,000 ppm, and (4) > 10,000 ppm. Nineteen of 20 collaborators reported results. Results from 2 laboratories were rejected as outliers by inspection and chi 2 test. Sensitivity rates (p+) ranged from 0.965 to 0.998, with standard errors of 0.006 to 0.16. Specificity rates (p-) ranged from 0.991 to 0.997 for the 4 ranges, with standard errors of 0.003 to 0.006. False-positive rates (pf+) ranged from 0.006 to 0.046, with standard errors of 0.006 to 0.025. False-negative rates (pf-) ranged from 0.003 to 0.007, with standard errors of 0.003 to 0.006. Screening nitrate in forages with a test strip has been adopted first action by AOAC INTERNATIONAL.     

Atomic Absorption Spectrometry Analysis of Silicates by the Absorption Tube Technique

Abstract

By the combined use of the absorption tube technique and solvent extraction, determination of cadmium, cobalt, copper, iron, lead and nickel in silicate rocks was investigated.

Applicable concentration range was from 0.1 to 1.Oppm for all the elements except cadmium, for which the range was from 0.005 to 0.025ppm. The accuracy and recovery determined by the use of standard samples from the United States National Bureau of Standards and Geological Survey were satisfactory for practical purposes.     

Petrochemical study of Al-Mizil plutonic rocks of Saudi Arabia

A petrochemical study of some rock samples has been carried out using different experimental techniques. The rock samples were collected from the Al-Mizil area, Saudi Arabia. Al-Mizil area consists of Precambrian metasediments which belong to the Halaban Formation. The plutonic rocks later intruded into the Halaban Formation. Major oxides and trace elements in these rocks are presented. The study indicates that the rocks are mainly of granitic composition. The petrochemical data suggest a magmatic origin for Al-Mizil granitic rocks.     

Determination of rare earth elements by neutron activation analysis in altered ultramafic rocks from the Akwatia District of the Birim diamondiferous field,Ghana

Summary Rare earth element (REE) analysis using instrumental neutron activation (INAA) was carried out on ultramafic rocks from the Akwatia District of the Birim diamondiferous field, Ghana, with the primary objective of investigating their kimberlitic characteristics. The total REE concentrations range from 113 to 1610 ppm and fall within the interval of those reported in the literature for kimberlites. Despite the marked difference in the REE contents, all the analyzed samples show similar REE patterns that resemble those of kimberlites. However, compared to most of the kimberlites, the ultramafic rocks have small negative Eu anomalies and low light-REE/heavy-REE ratios, suggesting that the rocks have been significantly assimilated by crustal rocks.     

Spectrophotometric procedure using rhodamine B for determination of submicrogram quantities of antimony in rocks

A spectrophotometric procedure using Rhodamine B is given for the determination of antimony in mineralized rocks after its separation as stibine. A study of the Rhodamine B reaction points to the importance of the order of addition of reagents in enhancing sensitivity and increasing the stability of the system. The tolerance of some 26 elements is established for the overall procedure. Although the limit of determination is approximately 0.5 ppm Sb in a 0.2-g sample, the procedure is intended primarily for screening samples containing more than 1 ppm Sb. In pure solutions 0.1 mug of antimony can be determined with a relative standard deviation of 25%. For >0.2 mug of antimony a relative standard deviation of 15% or less can be expected.     

Accurate and efficient determination of boron content in volcanic rocks by neutron induced prompt gamma-ray analysis

An accurate and efficient analytical method using neutron-induced prompt γ-ray was developed for the determination of boron contents in volcanic rocks. We corrected the effect of sample geometry and flux fluctuation by using silicon as an internal standard. However, we found that the slopes of the calibration line vary among volcanic samples with different matrix. Because the increase of boron activity correlates positively with γ-ray count rate of hydrogen (water), we call this as the hydrogen effect. The hydrogen effect was confirmed by our experiment in which the boron activities showed systematic increase with the amount of added hydrogen (water). Most volcanic rocks, however, contain little water (<2 wt.%) to show this effect. We determined boron contents in various volcanic rocks in order to confirm the validity of the procedure that we established. The analyzed boron contents agreed well with the previous reported values. For efficient PGA of boron in volcanic rocks, we recommend JB-2 (GSJ standard rock) as a single geochemical standard, because of its high boron content (31.2 ppm).     

Gamma-ray spectroscopic and PIXE analysis of selected samples from the phosphorite deposits of Northwestern Saudi Arabia

Phosphorite deposits from northwestern Saudi Arabia were analyzed by natural radioactivity measurements to detect the presence of radioactive elements. PIXE was used to obtain an average elemental composition of these deposits. From the analysis of radiations from ²³⁸U, ²³²Th and ⁴⁰K isotopes, the samples were found to contain U, Th and K in concentrations up to 130 ppm, 30 ppm and 2.5 wt%, respectively. PIXE showed the presence of a number of trace elements such as Ca, V, Cr, Fe, Ni, Cu, Zn, As, Sr, Y and U in concentrations ranging from a few ppm to several hundred ppm. The occurrence of these radioactive and non-radioactive elements are discussed for their geological significance in the phosphorite deposits.     

An automatic uranium analyser based on delayed neutron counting

An automated device for the analysis of uranium is described. The analyser comprises a sample transfer system, a neutron counter, a microprocessor and a teletype. A set of 100 samples, 14 ml of maximum volume, is analysed without manual intervention. The capacity is 45 samples per hour. Using a 10 g sample the detection limit is 0.06 ppm and uranium concentrations of 1 ppm can be determined with a precision of better than ±5%. The only source of systematic error is thorium the sensitivity of thorium being 2.3% of that of uranium. Results for USGS standard rocks are reported and the cost of the analysis is discussed.     

A rapid,simple method for the determination of total mercury in fish and hair by cold-vapour atomic absorption spectrometry

Fuming nitric acid and acidified potassium permanganate are used to pre-digest fish or hair samples in Pyrex culture tubes. Cold-vapour atomic absorption spectrometry is used to detect the elemental mercury which is generated by reduction in a syringe. The absolute detection limit of the method is 0.66 ng Hg, and at levels of 0.14 and 0.60 parts per million (ppm) the standard deviations are ± 0.009 and ±0.008 ppm, respectively. One person can handle batches of 50–100 samples per day including standards and blanks.     

Neutron activation determination of noble metals using a selective group separation scheme

A rapid and comprehensive method has been developed for the determination of ppm to sub-ppb amounts of Ru, Pd, Ag, Os, Ir, Pt and Au, based on thermal neutron irradiation, dissolution of samples, selective absorption on Srafion NMRR ion exchange resin and high resolution γ-ray spectrometry. Two noble metals “specific” resins were tested for their absorption behaviour. The method has been used for analysis of standard rocks, ores, minerals, lunar samples, coal, coal fly ash, and several biological materials.     

The determination of vanadium in geological materials by activation analysis with pre-irradiation separation

Vanadium is determined in silicate rocks by neutron activation after dissolution of the samples with HF/HNO₃ and separation by solvent extraction. The chemical yield of the pre-irradiation separation is determined by means of ⁴⁸V tracer. Results for 15 U.S. Geological Survey standard rocks are presented and discussed in relation to literature data. The method is especially useful at vanadium concentrations below 10 ppm, where purely instrumental neutron activation as well as other techniques commonly used for vanadium determinations in rocks, have inadequate sensitivity.     

Determination of Trace Copper in Cord Blood Serum from New Born Infants by Flameless AAS with Aerosol Deposition Technique

Abstract

This paper discusses the appropriate conditions for determining trace cooper by flameless atomic absorption spectrophotometry with the aerosol deposition technique. Seventeen samples of cord blood serum from the new born infants in the Hefei district of China were analyzed by this method. The range of trace copper in the samples is between 0.40-0.77 ppm, mean value 0.55 ppm. The recovery is over 90%. The relative standard deviation is 2.8%, determined by measurement of six times on a certain serum sample.     

Chlorid-spurenanalyse in silikatgesteinen durch massenspektrometrische isotopenverdünnungsanalyse

An analytical procedure for determining traces of chloride in silicate rocks, using mass spectrometric isotope dilution analysis with a ³⁷Cl-enriched spike, is described. The chlorine isotope ratios are measured with a double-filament thermal ion-source using the production of negative ions from a hot rhenium filament as the ionization method. The samples are decomposed with hydrofluoric acid in a Teflon bomb and chloride is separated from the acidic solution by selective precipitation as AgCl. The relative standard deviation for the chloride determination is 1–4% for chloride contents of 100–200 ppm. This precision is better than any described in the literature for chloride trace analysis. The problem of the blank in chloride trace determination in rock samples is discussed.     

Simultaneous determination of Rb and Cs by RNAA method

A RNAA method has been developed for the simultaneous determination of Rb and Cs in geological samples. The method is based on precipitation with sodium tetraphenylborate followed by NaI(Tl) gamma spectrometry. Three mica dust particulate samples and two USGS standard rocks, BCR-1 and W-1 were analyzed. Dipicrylamine (DPA) and 2-thenoyl-trifluoroacetone (TTA) in nitrobenzene were also used for solvent extraction. The precipitation method is better than solvent extraction.     

Determination of traces of organic fluorine in hydrocarbons

Organic samples containing down to 0.2 ppm of fluorine may be analysed by first converting the organic fluorine into inorganic fluoride by treatment with sodium biphenyl, followed by removal of diverse cations with a cation-exchanger before conductometric titration with lanthanum acetate. Effect of variables, sources of error, and control of reagent blanks are evaluated. For the 0.2-1 ppm organic fluorine level in synthetic blends made from 1-fluoronaphthalene, the relative estimated standard deviation was 7.8%; the mean relative error was 6.2 %. Based on the mean range from duplicate analyses of catalytically processed samples in the C(12) boiling range, at the 1 ppm fluorine level the estimated standard deviation was 0.087 ppm of fluorine. One analyst can determine the fluorine content of about 12 samples in 8 hr.