Exploring atmospheric radon with airborne gamma-ray spectroscopy (original) (raw)
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Evaluation of the Terrestrial 222Rn Flux from 210Pb Deposition Measurements
Environments
The study of the 222Rn terrestrial flux (Bq/(m2·s) or Bq/(m2·h)) is a complex issue involving both radiation-protection and environmental aspects. While the radiation-protection aspects are quite obvious—it has been well known for several decades that soil is the major source of indoor radon—environmental issues such as the correlation with conventional pollutants (PM2.5, PM10, NOX, etc.) and the use of radon for the esmation of the natural component of GHG (CO2) emissions are relatively less discussed in spite of their growing relevance. In this work we present a method for the estimation of the average value of 222Rn flux from HPGe γ-spectrometry 210Pb measurements performed on wet and dry deposition samples gathered monthly in the period 2006–2020. The results obtained with this technique give an average radon flux in the period Φ = 57 ± 27 Bq/(m2·h), the value of which is comparable with those coming from other methods and direct radon flux measurements as well. The method can t...
Ground based radon-222 observations and their application to atmospheric studies
Journal of Environmental Radioactivity, 2004
The aim of this paper is to review recent trends in the appli cation of ground based radon observations to atmospheric research. In spite of over four decades of atmospheric radon monitoring, only in the past decade has the potential of this passive tracer been realised through a series of atmospheric model evaluation studies. Firstly, the key operational requirements for baseline radon detectors are briefly discussed, including lower limit of detection and response time. Then, current radon-related benchmarks for the evaluation of regional and global models are reviewed, with particular consideration given to the implications of data availability, resolution, site location and model spatial/temporal resolution. An 8-year subset of radon observations from the Cape Grim Baseline Air Pollution Station is used to suggest new benchmarks that exploit long-term data sets. Lastly an overview is presented of a technique that uses radon to estimate regional fluxes of climatically sensitive gases, with specific examples for CO 2 , CH 4 and N 2 O. Crown
Tellus Series B-chemical and Physical Meteorology, 2005
Model-predicted atmospheric concentrations of 222Rn based on two different 222Rn source terms have been compared with observations in the lower troposphere. One simulation used a globally uniform 222Rn source term from ice-free land surfaces of 1 atom cm−2 s−1; the other assumed a northwards-decreasing source term (linear decrease from 1 atom cm−2 s−1 at 30◦N to 0.2 atom cm−2 s−1 at 70◦N). Zero emissions were assigned to oceans. The northwards-decreasing source term improved predictions at four out of six stations north of 50◦N, reducing the mean prediction/observation ratio from 2.8 to 0.87. In the latitudinal band between 30◦N and 50◦N, the northwards-decreasing source term resulted in systematic under-prediction of atmospheric 222Rn, whereas the uniform source term provided predictions close to observations. Predictions based on the northwards-decreasing source term were significantly (p < 0.01) better than those based on the uniform source term for an averaged vertical 222Rn profile around 44◦N, but were not for one around 38◦N. The results indicate that a northwards-decreasing source term could be a more realistic representation of actual 222Rn emissions than a uniform 1 atom cm−2 s−1 source term. However, the decrease in 222Rn source strength with increasing latitude might not begin at 30◦N but somewhat further north. This hypothesis should be investigated through model-independent means.
Latitudinal distribution of radon-222 flux from continents
Tellus Series B-chemical and Physical Meteorology, 2002
Global atmospheric transport models are frequently tested by using 222Rn as a tracer. Generally this tracer is assumed to be emitted at a uniform rate (1 atom cm−2 s−1) from all ice-free land surfaces. The analysis of published data suggests a strong decrease from 30°N northwards to 0.2 atom cm−2 s−1 at 70°N. This could be a result of increasing water tables and proportions of organic soils as indicated by larger proportions of wetlands in northern latitudes.
Airborne Gamma-ray Spectrometry: Radon Correction and Mapping
In Airborne Gamma-Ray Spectrometry, the main geological goal of data processing is to get the abundances of natural potassium, uranium, and thorium in near-surface rocks. The estimation of uranium is a difficult and important problem due to the presence of radon in the air that has no geological value. This problem arises because the main emitters of the U-238 radioactive family are the same both in air and in the ground, and they cannot be distinguished by energy. Without corrections for radon in the air, data on uranium geological emitters can be distorted beyond recognition (overestimated many times). Several methods for radon correction are known. They are based on various approaches to compare the different parts of spectra. The presence of radon changes the spectra in two ways - in the areas of photopeaks and Compton scattering. Both these features are used here to construct two new radon corrections. The first correction uses the standard geophysical model of two half-spaces near every data point. The second correction uses empirical local features of the spectra near the photopeaks.
2012
Es los ultimos anos se han llevado a cabo importantes trabajos de investigacion, tomando el gas radon como elemento de evaluacion en modelos de transporte atmosferico y asi estimar el flujo de particulas. Ademas la utilizacion del radon ha encontrado otras aplicaciones en el estudio de las emisiones de gases de efecto invernadero a escala regional; en la actualidad en algunos proyectos europeos como el Ttorch y el InGOS se realizan medidas en continuo de radon atmosferico junto con otros gases de efecto invernadero. En este marco de actuacion, la presente tesis quiere caracterizar una nueva estacion de radon atmosferico en El Arenosillo, en la cuenca sur de Espana, llevando a cabo medidas de radon a diferentes alturas gracias a una torre de 100 metros. Ademas otro objetivo de la tesis ha sido la caracterizacion del flujo de radon en esta area geografica. Este trabajo incluye, ademas de un analisis de las concentraciones de radon mediante un sistema de esfera por electrodeposicion, l...
Radon fluxes from soils to the atmosphere measured by 210Pb226Ra disequilibrium in soils
Geophys Res Lett, 1990
Measurements of the activities of the parent (226Ra) and progeny (210Pb) of 222Rn in 119 core samples of N•h American soils reveal that the mean fraction of the 222Rn •uced in the upper 50 cm that escapes to the atmosphere eq •uals or exceeds 25%. The flux derived from the upper 50 cm is 0.48 atoms cm '2 s-1. Measurement of 210pb-226Ra disequililxium at greater depths in 12 cores indicates a mean depth of 222Rn escape of-218 cm, slightly greater than commonly re-• values of ~175 cm. Using these mean depths to extrapolate the flux measurements from the upper 50 cm yields a total .radon flux of from 1.9 to 2.3 atoms cm-2 s-1. Introduction he emanation of 222Rn (half-life = 3.8 d) from soils is the pri• source of radon in the atmosphere. As air moves and 222Rn decays, its non-gaseous progeny, including 2ioPb (halflife = 22.3 y), attach to aerosols and return to the surface of both continent and ocean. 210Pb is far less mobile in soils than 222Rn. As a result, in the upper decimeter of soil the 210Pb activity is generally greater than that of 226Ra (half-life = 1620 y), '•e parent of 222Rn. At greater depths the 210pb activity is le• than than that of 226Ra due to the escape of 222Rn from the ß • to the atmosphere. I37Cs (half-life = 30.2 y), was injected into the atmosphere by nuclear weapons, attached to aerosols • delivered to soil surfaces in a similar fashion to 210pb. Its distribution in soils is an index of the atmospherically-derived component of 210pb (Graustein and Turekian, 1986). The measurement of 2!0pb, 226Ra and 137Cs in an old (-!00 years) undisturbed soil profile thus provides an estimate of the fluxes of 222Rn from the soil to the atmosphere and of 210Pb and 137Cs from the atmosphere to the soil at the site. Our purpose in measuring 222Rn loss rates is to relate 222Rn fluxes to such factors as 226Ra concentration of the soil, soil type, climate and vegetation. These data and relations apply to •e understan•g of gas transport mechanisms in soils (e.g. Schery and Gaeddert, 1982) and of vertical mixing and horizomal transport in the atmosphere (e.g. Turekian, et al., 1977; Liu, et al., 1984). In addition, this information can provide a general predictive tool for estimating potential radon supply to ,structures. Technique We collected 119 soil cores of 40 cm or greater depth from 5,6 sites in 31 states of the United States and 3 Canadian provinces. With a •ingle exception, we chose sites with soils Copyright 1990 by the American Geophysical Union. ?aper number 90GL00397 0094-8276/90/90GL_00397503. O0 that over the last 100 years had not undergone significant erosion or sedimentation, or been disturbed by man's activities so that the distributions of 210Pb, 226Ra and 137Cs would reflect only natural diffusive and advective transport processes. 100 years is about 5 times the half-life of 210pb. The 210pb activity therefore equals the long-term mean 222Rn activity, but does not show annual or shorter-term fluctuation (Graustein and Turekian, 1986). Samples were collected between 1982 and 1988. 137Cs activities are decay-corrected to January 1, 1984; excesses or deficiencies of 210Pb with respect to 226Ra are decay corrected to the date of collection.
Tellus Series B-chemical and Physical Meteorology, 2002
A monitor for continuous observations of the atmospheric 222 Rn daughter activity has been improved and successfully implemented in a field study in the European Taiga (Fyodorovskoye Forest Reserve). The α-activity of the short-lived 222 Rn and 220 Rn ( 212 Pb) decay products, which are attached to aerosols, is accumulated on a quartz aerosol filter and assayed on line by α-spectroscopy. The α-activity from the 212 Pb daughters is determined by spectroscopy and corrected for. This monitor is suitable to measure 222 Rn activities at hourly resolution down to 0.5 Bq m −3 with an uncertainty well below ±20%. The prototype of this monitor is run in Heidelberg on the roof of the Institute's building about 20 m above ground. For this site, the atmospheric radioactive disequilibrium was determined between the 222 Rn daughter 214 Po and 222 Rn, which has to be known in order to derive the atmospheric 222 Rn activity with the static filter method. We derived a mean disequilibrium 214 Po/ 222 Rn = 0.704 ± 0.081 for various meteorological conditions through parallel 222 Rn gas measurements with a slow pulse ionisation chamber. At the Russian field site, continuous activity observations were performed from July 1998 until July 2000 with half a year's interruption in summer/fall 1999. During intensive campaigns, a second monitor was installed at Fyodorovskoye at 15.6 m (July/August 1998), and at 1.8 m (July/August 1999 and October 1999) above ground. As expected, pronounced diurnal cycles of the 222 Rn daughter activity were observed at all sites, particularly during summer when the vertical mixing conditions in the atmospheric surface layer vary strongly between day and night. The lower envelope of the continuous measurements at Fyodorovskoye and at Heidelberg changes on synoptic timescales by a factor of 4-10 due to long-range transport changes between continental to more maritime situations. Generally, the 222 Rn activity at 26.3 m height at Fyodorovskoye is lower by a factor of 2-3 compared to Heidelberg at 20 m above ground. This unexpected result is due to considerably lower 222 Rn exhalation rates from the soils measured in the footprint of the Fyodorovskoye Forest tower compared to Heidelberg. With the inverted chamber technique 222 Rn exhalation rates in the range 3.3-7.9 Bq m −2 h −1 were determined at Fyodorovskoye for summer 1998 and autumn 1999 (wet conditions with water table depths between 5 and 70 cm). Only during the very dry summer of 1999 the mean 222 Rn exhalation rate increased by about a factor of five. All measured exhalation rates at the Fyodorovskoye Forest are considerably smaller by a factor of 2-10 compared to observations in the vicinity of Heidelberg (ca. 50-60 Bq m −2 h −1 ) and generally in Western Europe.
Environments, 2020
Sodium-22 (22Na, half-life 2.603 years) is a cosmogenic radionuclide mainly produced in the stratosphere by nuclear spallation reactions of cosmic rays on 40Ar. Due to the very low concentration levels normally reached in the environment, 22Na poses no significant radioprotection threats: actually, the effective doses delivered to humans can hardly exceed a few nSv per year, a very negligible value. However, the measurements of this radionuclides can be very interesting for atmospheric circulation and climatic studies. Unfortunately, the difficulty of 22Na detection, due to its very low concentration levels, has prevented the gathering of large and widespread time series of this radionuclide. In this paper, a method for the retrospective measurements of 22Na in the atmosphere, starting from the gamma spectra (hyperpure germanium detectors (HPGe) detectors) of wet and dry deposition samples stored in our databases is proposed and validated. The method was applied to spectra samples g...