Radon emanometric technique for 226Ra estimation

Studies on natural background radiation show that the major contribution of radiation dose received by population is through inhalation pathway vis-à-vis contribution from radon (²²²Rn) gas. The immediate parent of radon being radium (²²⁶Ra), it is imperative that radium content is measured in the various matrices that are present in the environment. Among the various methods available for the measurement of radium, gamma spectrometry and radiochemical method are the two extensively used measurement methods. In comparison with these two methods, the radon emanometric technique, described here, is a simple and convenient method. The paper gives details of sample processing, radon bubbler, Lucas cell and the methodology used in the emanometric method. Comparison of emanometric method with gamma spectrometry has also undertaken and the results for a few soil samples are given. The results show a fairly good agreement among the two methods.     

Evaluating the potential alpha energy of radon progeny

Potential alpha energy concentration of radon progeny can be measured using the alpha-spectroscopy with the silicon semiconductors detectors and the gross-counting attached with the ZnS detectors. The decay method was applied where the alpha particles emitted from the ²¹⁸Po to ²¹⁴Po were detected. In the case of the decay products, the amount and aerodynamic behavior of radioactivity are important, and also need to be measured. During the experiment, the radon gas was supplied and evaluated from the experimental room with constant concentration. Then the air sample was used as the known volume and the grab sampling technique was developed for estimating the concentration of radon decay products. However the proper calculation was applied for estimating the potential alpha energy of radon progeny through of ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi.     

An accurate method for the determination of <Superscript>226</Superscript>Ra activity concentrations in soil

A quantitative method to determine the activity concentration of ²²⁶Ra in soil samples was established using high performance environmental gamma-ray spectrometry. In this method, a semi-empirical calibration procedure was developed for full energy peak efficiency calculation utilizing the elemental composition of the soil sample. Aatami software was used to deconvolute the ²³⁵U and ²²⁶Ra doublet at 185.7 keV and 186.2 keV, respectively, and to fit the baseline of the soil gamma-spectrum for the determination of ²²⁶Ra activity. The results indicated that the Aatami doublet deconvolution procedure provides a rapid and accurate analysis of a complicated spectrum in comparison with other cumbersome spectral interference correction methods. The study also compared the results with those obtained by radon progeny (²¹⁴Pb, or ²¹⁴Bi) measurements and found that the deconvolution method provided a more accurate ²²⁶Ra activity as it is independent of the error caused by radon diffusion. This error can be quite large since the amount of escaped radon gas through the sample container walls and sealing cannot be accurately quantified.     

The measuring of radon volumetric activity and exhalation rate in ground-level air

The physical and chemical characteristics of radon gas make it a good tracer for use in the application of atmospheric transport models. Radon exhalation rate from soil is one of the most important factors for evaluation of the environmental radon level. For this purpose to find out the volumetric activity of radon in ground-level air the measuring has been made using radon monitor SARAD RTM 2200. Radon volumetric activity and radon exhalation rate in ground-level air and at different depths of soil depending on soil temperature and atmospheric parameters in different seasons of the year was calculated and evaluated in two areas of Vilnius city. It has been established that the volumetric activity of radon and radon exhalation intensity is vertically distributed and the corresponding increase in deeper soil layers, and depends on the specific activity of radium, soil temperature and moisture content, temperature difference between soil and atmospheric temperatures.     

Radon Mapping of Soils in St. Elizabeth, Jamaica

Soil gas measurements of radon were made in St. Elizabeth, Jamaica using nuclear track etch detectors. The results were compared to gamma-ray spectroscopy measurements made in the laboratory on soil samples collected at the radon measurement sites. An assessment of the degree of disequilibrium of uranium and thorium was also made by comparison with neutron activation analysis, delayed neutron counting and equivalent uranium and thorium measurements. The results to date for equivalent uranium and radon show a strong correlation and indicate the possibility of soil radon mapping in Jamaica using gamma-ray spectroscopy. Three anomalous sites have been identified.     

Soil gases (222Rn, 220Rn and total radon) and 214Bi measurements across El Avila fault near Caracas, Venezuela

Summary Radon measurements were performed across two sections of the Avila fault near Caracas, Venezuela. The radon concentrations clearly showed the different tectonic features and lithology at the Tacamahaca and Spanish Trail sites. ²¹⁴Bi (U-cps) measurements also were related to the lithology. The passive radon method employed laboratory-made dosimeters with LR 115, type 2 celulose nitrate films as detectors. They were buried in the ground at 30 cm depth. While, the active radon method was performed with a Pylon radon measurement system with Lucas cells. The soil gas was also sampled at 30 cm depths, but for only one minute, which was sufficient to fill the 150 cm³ Lucas cells completely. The total radon counts were then separated into those corresponding to ²²²Rn (radon) and ²²⁰Rn (thoron) by a simple computer routine. A comparison of the active and passive methods for the Tacamahaca section over a three-month period showed that both methods could locate precisely the active fault trace.     

A simple passive collector for direct measurement of radon flux from soil

A simple technique for measurement of the soil-atmosphere radon flux has been developed by fastening a charcoal canister inside a PVC cylindrical container. This device, which is deployed at the ground surface for approximately 16 hours, captures radon emanating from the soil by adsorption onto the charcoal surface. After recovery of the canister and measurement of the radon daughter activity on a NaI detector, the radon flux may be calculated if the adsorption efficiency of radon onto the charcoal is known. This parameter was determined by exposure of charcoal canisters to²²⁶Ra-spiked barium palmitate filter sources for timed intervals. Since this compound is known to emanate 100% of the²²²Rn generated during radium decay, it forms a useful flux standard. The accuracy of our flux measurements was assessed by comparison to a more established technique, the enclosed-chamber or accumulator method. Concentration measurements were made for the chamber over a less than 2-hour period while the canister flux measurements were based on single overnight deployments. The experiment was repeated 5 times at two different sites and the two techniques generally agreed within a 95% confidence interval.     

A new approach for radon monitoring in soil as an earthquake precursor using optical fiber

Temporal variations of radon concentration in soil before the earthquake are known as an earthquake precursor. For using of radon as an earthquake precursor, it is necessary to constantly monitor radon concentration variations in a relatively wide range in the vicinity of a fault which is virtually impossible for radon detectors that already exist. This paper proposes a new method for continuous measurement of radon concentration variations in a wide range, using optical fiber as radon detector. For this purpose, an experimental system consisting of radon source, optical-fiber holding chamber, radon gas detector, optical laser source, and optical power meter have been arranged to with the aim to create different concentrations of radon gas in the vicinity of the optical fiber; the attenuation which creates on optical fiber is subsequently measured. As a result, the average of the attenuation is 0.004 μw per each meter per Bq/l since the fault’s length is more than ten kilometers; sensitivity of the measurement can be improved many times over.     

Determination of air-loop volume and radon partition coefficient for measuring radon in water sample

A simple method for the direct determination of the air-loop volume in a RAD7 system as well as the radon partition coefficient was developed allowing for an accurate measurement of the radon activity in any type of water. The air-loop volume may be measured directly using an external radon source and an empty bottle with a precisely measured volume. The partition coefficient and activity of radon in the water sample may then be determined via the RAD7 using the determined air-loop volume. Activity ratios instead of absolute activities were used to measure the air-loop volume and the radon partition coefficient. In order to verify this approach, we measured the radon partition coefficient in deionized water in the temperature range of 10–30 °C and compared the values to those calculated from the well-known Weigel equation. The results were within 5 % variance throughout the temperature range. We also applied the approach for measurement of the radon partition coefficient in synthetic saline water (0–75 ppt salinity) as well as tap water. The radon activity of the tap water sample was determined by this method as well as the standard RAD-H₂O and BigBottle RAD-H₂O. The results have shown good agreement between this method and the standard methods.     

Field alpha-spectroscopy of radon (<Superscript>222</Superscript>Rn) and actinon (<Superscript>219</Superscript>Rn) progeny in soil gas: Locating a radon source

Summary The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were determined in samples obtained of soil/gas. Sampling work was taken in Jáchymov (Czech Republic) at the outcrop of the Geister-vein,by electrostatic precipitation from filtered soil gas on stainless steel disks.The samples were measured in a field laboratory using a semi-conductor alpha-spectrometer.The activities of²¹⁸Po,²¹⁴Po and²¹¹Bi were calculated.Samples taken from active dump material (near-by radon source) exhibited a high²¹¹Bi/²¹⁴Po ratio, while those of the vein outcrop (a relatively deeper source) had a low ratio.A mathematical model was employed to determine the radon age calculated from the actinon/radon input ratio.This varied in a range of 5.6 to -7.7 seconds.Negative age values are probably caused by the preference for actinon, which rapidly comes into equilibrium with the source of this gas.     

Measurement of radon emanation of drainage layer media by liquid scintillation counting

Slab-on-ground is a typical base floor construction type in Finland. The drainage layer between the slab and soil is a layer of sand, gravel or crushed stone. This layer has a minimum thickness of 200 mm and is sometimes even 600 mm thick, and thus may be a significant contributor to indoor air radon. In order to investigate radon emanation from the drainage layer material, a simple laboratory test was developed. Many organic solvents have high Ostwald coefficients for radon, i.e., the ratio of the volume of gas absorbed to the volume of the absorbing liquid, which enables direct absorption of radon into a liquid scintillation cocktail. Here, we first present equations relating to the processes of gas transfer in emanation measurement by direct absorption into liquid scintillation cocktails. In order to optimize the method for emanation measurement, four liquid scintillation cocktails were assessed for their ability to absorb radon from air. A simple apparatus consisting of a closed glass container holding an open liquid scintillation vial was designed and the diffusion/absorption rate and Ostwald coefficient were determined for a selected cocktail. Finally, a simple test was developed based on this work.     

Trace analysis of pesticides by gas chromatography.

The analysis of pesticides is relevant to both food quality and the environment. Many laboratories are occupied with the analysis of pesticides in food, water or soil. Capillary gas chromatography is the technique most widely used in pesticide analysis. In present laboratory practice it serves as a screening method for over 300 pesticides. In this review we describe the role of gas chromatography as an analytical tool in combination with currently used or recently developed sample preparation techniques.     

Simple and rapid methods for on-site determination of radon and thoron in soil-gases for seismic studies

The determination of soil-gas anomalies especially ²²²Rn anomalies, are important to precisely locate fault traces, as well as to investigate earthquake precursors. In this paper, we have studied and compared new rapid methods for on site determinations of radon (²²²Rn), thoron (²²⁰Rn) and total radon (²²²Rn+²²⁰Rn) in soil-gas. These new techniques pump the soil-gas continuously from the soil through a simple sampling tube to the counting cell for one-minute with discarding the excess. Then, either four one-minute counting periods (5-minute technique) or nine one-minute counting intervals (10-minute technique) are followed immediately. In all the methods, conversely to Morse"s method, the first counting period (C1) was not employed for calculations. Three calculation methods for the five-minute technique, two for the ten-minute technique and a modified Morse"s method are compared with theoretical values and different real soil-gases with different radon/thoron ratios. The affect of different flow rates of soil-gases into the counting cell was also investigated. Finally, the ten-minute technique seems to be a little more accurate, but the 5-minute technique is much more suitable for seismic field studies when a much larger number of determinations are required in a short time.     

Measurements of indoor radon concentration levels in Kilis,Osmaniye and Antakya,Turkey during spring season

The fact that 50% of the natural radiation dose to which humans are exposed is caused by radon gas makes indoor radon measurements important. In this study, levels of indoor radon gas were measured in 204 houses in Kilis, Osmaniye and Antakya using passive nuclear track detectors. Cr-39 radon detectors were left in the living rooms of participants’ houses, then analyzed at the Radon Laboratory of Health Physics Department in Çekmece Nuclear Research and Training Center (ÇANEM) of Atomic Energy Agency of Turkey (TAEK). Average indoor radon activity concentrations for Kilis, Osmaniye and Antakya were 50 Bq/m³ (1.26 mSv/y), 51 Bq/m³ (1.29 mSv/y) and 40 Bq/m³ (1.01 mSv/y), respectively.     

Short- and long-term monitoring of radon, thoron and carbon dioxide in soil-gas at Altos de pipe, Venezuela

We have measured radon and thoron activities in soil-gases since July 9, 1997 Cariaco earthquake (Mw=6.9) until the end of 2000. Carbon dioxide concentrations were also monitored between 1998–2000. The soil-gas was collected between 50–55 cm depths at two sampling points at Altos de pipe (Instituto Venezolano de Investigaciones Cientificas-IVIC) near Caracas, Venezuela. The radon and thoron measurements were performed daily employing radiation monitors with scintillation cells and the carbon dioxide was monitored with portable gas analyzers. Average weekly and monthly values were calculated and plotted for this three-four year period. In general, both the radon and carbon dioxide values showed sinusoidal trends due to seasonal changes. During the dry season the radon and carbon dioxide values decreased, while the radon activity was relative constant (flat) during the rainy season at one of the sampling points. Only two monthly radon values were seen to be anomalous in the graphs in respect to seven anomalous periods for the average weekly values. No anomalous periods were clearly seen for carbon dioxide. Finally, it was difficult to try to relate these radon anomalous periods with specific earthquakes due to the large number of minor earthquakes during these years, but it seem that the minor earthquake (Mb=5.9) of October 4, 2000 could be associated with the radon anomalous period in September, when there were no other minor earthquakes (Mb≥4.0). This revised version was published online in July 2006 with corrections to the Cover Date.     

Rapid <Superscript>224</Superscript>Ra measurements in water via multiple radon detectors

We introduce an improved on-site rapid analysis system for measuring ²²⁴Ra in natural waters. Radium isotopes are pre-concentrated on “Mn-fibers” before measurement of ²²⁰Rn. A Nafion drying system is used to lower the humidity in the detectors while maintaining a relatively constant moisture level in the Mn fiber in order to maintain a high and reproducible radon emanation. River water samples measured by this method agreed well with an analysis via RaDeCC, a very sensitive technique for measuring ²²⁴Ra. This method is recommended for fieldwork in remote areas when electricity and helium gas, required by traditional techniques, are not available.     

Absolute Determination of Radon in me Marine Troposphere

Abstract

A method for the direct determination of radon in the atmosphere was developed to measure radon mixing ratio with high precision at the low levels found in the marine troposphere away from continental air mass contamination. Developed for the DYCOMS atmospheric dynamic and chemical measurement experiment over the eastern Pacific Ocean during July and August, l985 it combines scintillation cell counting with the collection of large volume air samples using low flying aircraft. An equation that combines the growth and decay of radon and radon progeny was written for a microcomputer and is used to compare alpha activity in the cell with the number of radon atoms in a sample. Radon mixing ratios as low as 12 atoms per liter of air have been measured using this method.     

Determination of chlorobenzenes in environmental samples using solid phase microextraction, thermal desorption and analysis by gas chromatography coupled to FID, ECD, MSD, IRD detectors

Summary A complex method was developed for the determination of chlorobenzenes in soil and groundwater samples. Samples were taken at two sites in Baranya county, where a mixture of chlorobenzene waste was deposited, causing severe contamination in the environment. Clean-up of these sites demands modern and reliable analytical methods. Several sample preparation techniques were used, such as solid phase microextraction (SPME), supercritical fluid extraction (SFE), and a recently developed thermal desorption method. The applicability of various sample preparation methods was compared by measuring recovery percentages, relative standard deviations and by investigating the matrix dependency of these values. Gas chromatography was used for quantitative determination of chlorobenzenes, using MS, IR, FID and ECD detection techniques. Detection levels were as low as 1 ppt in water, and 10 ppt in soil samples. Chlorobenzene concentration was in the range 1 ppt-1 ppm in water and 100 ppb-100 ppm in soil samples. Identification and calibration of these compounds were performed by quantitative standards. This complex analytical method can be used for rapid and precise quantitative and qualitative determination of chlorobenzenes. Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997     

Measurements of222Rn migration in soil

The concentration of radon (²²²Rn) was measured in the soil near the ground surface, using CR/39 solid state nuclear track detectors. The measurements were carried out in PVC tubes at 0.25 m intervals up to 1.25 m. The detectors were etched in 7N NaOH solutions at 80°C. The -tracks from radon's decay were counted using a microscope. A microscope-camera-computer system developed for automatic counting was also used. The results provide evidence for the non-diffusive transport of radon in soils. A transport length of (46.9±3.2) cm was estimated for radon transport near ground surface. Also the variation of soil's radon concentration was correlate to humidity and atmospheric pressure.     

Study on alpha cup technique for monitoring of soil radon levels

Determination of radon concentrations in soil usually requires the accumulation of many measurements over a large area. In this study, an alpha cup technique that provides a cumulative result for adsorption of radon progeny over time was investigated. In addition, the performance of measurements were evaluated. To avoid the impacts of temperature and humidity, a new arithmetic correction was explored. Finally, we also investigated the effect of burial time of the alpha cup on soil radon measurements. Experiments showed that the alpha cup technique can satisfy the demands of soil radon measurements in efficiency, accuracy, reliability, and stability.