One year of 222 Rn concentration in the atmospheric surface layer
TL;DR: In this article, a one-year time series of radon measured in a rural area in the North of Italy in 1997 has been analyzed, where wavelet analysis is used as one of the investigation tools of the time series.
Abstract: A one-year time series of 222 Rn measured in a rural area in the North of Italy in 1997 is analyzed. The scope of the investigation is to better understand the behavior of this common atmospheric tracer in relation to the meteorological conditions at the release site. Wavelet analysis is used as one of the investigation tools of the time series. The measurements and scalograms of 222 Rn are compared to those of wind-speed, pressure, relative humidity, temperature and NO x . The use of wavelet analysis allows the identification of the various scales controlling the influence of the meteorological variables on 222 Rn dispersion in the surface layer that are not visible through classical Fourier analysis or direct time series inspection. The analysis of the time series has identified specific periods during which the usual diurnal variation of radon is superimposed to a linear growth thus indicating the build up of concentration at the measurement level. From these specific cases an estimate of the surface flux of 222 Rn is made. By means of a simple model these special cases are reproduced.
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TL;DR: In this paper, two years of radon-222 observations collected at L’Aquila (Italy) in the atmospheric surface layer during 2004-2006 were analyzed in correlation with meteorological data and other atmospheric tracers.
Abstract: Two years of radon-222 observations collected at L’Aquila (Italy) in the atmospheric surface layer during 2004–2006 were analyzed in correlation with meteorological data and other atmospheric tracers. A box model was developed to better understand the mechanisms of diurnal and seasonal variability of the tracer and to indirectly assess the magnitude of the monthly averaged radon soil flux in the L’Aquila measurement site. The model was successfully validated with measurements, with a 0.8 average correlation coefficient between hourly values for the whole period of radon observations. Measurements taken during March 2009 were analyzed to find possible signs of perturbation due to the ongoing seismic activity that would have reached its peak on the 6 April 2009 destructive earthquake. Contrary to the professed (and unpublished) dramatic increases of radon activity unofficially announced to the inhabitants at that time, the study presented here shows that no radon activity increase took place in L’Aquila with respect to a previous ‘seismically unperturbed’ year (same month with similar meteorological conditions), but that an average 30 % decrease was experienced. This conclusion is reached from a direct comparison of observed data and also as a result of the previously validated radon box model constrained by actual meteorological data, from which an indirect estimate of a 17 % reduction of the radon soil flux is obtained.
19 citations
Cites methods from "One year of 222 Rn concentration in..."
...Following Galmarini (2006), the soil emission flux is estimated from nighttime radon activity concentrations selecting only those nights when local wind speed was less than a fixed threshold (1.0 ms-1 in this case), as an indicator of the stability of the nocturnal atmospheric surface layer (Lmix ?...
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TL;DR: In this article, the diurnal atmospheric boundary layer evolution of the 222 Rn decaying family was studied using a state-of-the-art large-eddy simulation model, and the effect of diurnal varying turbulent characteristics on radioactive compounds initially in a secular equilibrium.
Abstract: The diurnal atmospheric boundary layer evolution of the 222 Rn decaying family is studied using a state-of-the-art large-eddy simulation model. In particular, a diurnal cycle observed during the Wangara experiment is successfully simulated together with the effect of diurnal varying turbulent characteristics on radioactive compounds initially in a secular equilibrium. This study allows us to clearly analyze and identify the boundary layer processes driving the behaviour of 222 Rn and its progeny concentrations. An activity disequilibrium is observed in the nocturnal boundary layer due to the proximity of the radon source and the trapping of fresh 222 Rn close to the surface induced by the weak vertical transport. During the morning transition, the secular equilibrium is fast restored by the vigorous turbulent mixing. The evolution of 222 Rn and its progeny concentrations in the unsteady growing convective boundary layer depends on the strength of entrainment events.
18 citations
TL;DR: In this paper, a radon-based method (RBM) and a pseudo-vertical temperature gradient method (TGM) were compared for air quality assessment in a topographically complex subalpine basin.
Abstract: . One year of meteorological and atmospheric radon
observations in a topographically complex subalpine basin are used to
identify persistent temperature inversion (PTI) events. PTI events play a
key role in public health due to the accumulation of urban pollutants that
they cause. Two techniques are compared: a new radon-based method (RBM),
based on single-height 222Rn measurements from a single
centrally located station, and an existing pseudo-vertical temperature
gradient method (TGM) based on observations from eight weather stations
around the subalpine basin. The RBM identified six PTI events (four in winter, two
in autumn), a subset of the 17 events identified by the TGM. The RBM was
more consistent in its identification of PTI events for all seasons and
more selective of persistent strongly stable conditions. The comparatively
poor performance of the TGM was attributed to seasonal inconsistencies in
the validity of the method's key assumptions (influenced by mesoscale
processes, such as local drainage flows, nocturnal jets, and intermittent
turbulence influence) and a lack of snow cover in the basin for the
2016–2017 winter period. Corresponding meteorological quantities for RBM
PTI events (constituting 27 % of the autumn–winter cold season) were
well characterized. PTI wind speeds in the basin were consistently low over
the whole diurnal cycle (typically 0.2–0.6 m s −1 ). Suitability of the
two techniques for air quality assessment was compared using hourly
PM 10 observations. Peak PM 10 concentrations for winter (autumn)
PTI events were underestimated by 13 µ g m −3 (11 µ g m −3 ) by the TGM compared with the RBM. Only the RBM indicated that
nocturnal hourly mean PM 10 values in winter PTI events can exceed 100 µ g m −3 , the upper threshold of low-level short-term PM 10
exposure according to World Health Organization guidelines. The efficacy,
simplicity, and cost effectiveness of the RBM for identifying PTI events has
the potential to make it a powerful tool for urban air quality management in
complex terrain regions, for which it adds an additional dimension to
contemporary atmospheric stability classification tools. Furthermore, the
long-term consistency of the radon source function will enable the RBM to be
used in the same way in future studies, enabling the relative magnitude of
PTI events to be gauged, which is expected to assist with the assessment of
public health risks.
17 citations
Journal Article•
TL;DR: In this article, the long term measurements of radon, thoron and their progeny concentrations in about 100 dwellings using solid state nuclear track detectors were presented. But the results revealed that radon and thoron are relatively higher in granite than in concrete, cement and bricks and the concentration observed in bathrooms is more compared to kitchen, bedroom and living rooms.
Abstract: Background: Radon, thoron and their progenies are the most important contributions to human exposure from natural sources. Radon exists in soil gas, building materials, Indoor atmosphere etc. Among all the natural sources of radiation dose to human beings, inhalation of radon contributes a lot. The work presented here emphasizes the long term measurements of radon, thoron and their progeny concentrations in about 100 dwellings using solid state nuclear track detectors. Materials and Methods: Measurements were made using dosimeters and the concentrations were estimated by knowing the track density of films through spark counter, and sensitivity factor for bare, filter and membrane films. Results: Presence of radon and thoron in houses is the effect of several aspects such as the activity concentrations of uranium, radium and thorium in the local soil, building materials, ventilation of houses and also entry of radon into houses through the cracks in floor/wall. Conclusion: The observations reveal that the concentrations of radon and/or thoron are relatively higher in granite than in concrete, cement and bricks. In continuation to this the concentration observed in bathrooms is more compared to kitchen, bedroom and living rooms. This study discloses that the residential rooms of good ventilation will avoid the health hazards due to radon and its rich materials. Iran. J. Radiat. Res., 2009; 7 (1): 19
16 citations
TL;DR: The results suggested that the presence of the phosphogypsum piles was necessary in order to justify the high (222)Rn activity concentrations observed at Huelva compared with the background station in the afternoons on pure sea breeze days.
14 citations
References
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TL;DR: In this article, a step-by-step guide to wavelet analysis is given, with examples taken from time series of the El Nino-Southern Oscillation (ENSO).
Abstract: A practical step-by-step guide to wavelet analysis is given, with examples taken from time series of the El Nino–Southern Oscillation (ENSO). The guide includes a comparison to the windowed Fourier transform, the choice of an appropriate wavelet basis function, edge effects due to finite-length time series, and the relationship between wavelet scale and Fourier frequency. New statistical significance tests for wavelet power spectra are developed by deriving theoretical wavelet spectra for white and red noise processes and using these to establish significance levels and confidence intervals. It is shown that smoothing in time or scale can be used to increase the confidence of the wavelet spectrum. Empirical formulas are given for the effect of smoothing on significance levels and confidence intervals. Extensions to wavelet analysis such as filtering, the power Hovmoller, cross-wavelet spectra, and coherence are described. The statistical significance tests are used to give a quantitative measure of change...
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"One year of 222 Rn concentration in..." refers background or methods in this paper
...The latter10 is obtained by means of a χ2 test as described in Torrence and Compo (1998)....
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...The latter 10 is obtained by means of a χ(2) test as described in Torrence and Compo (1998). The white contour superimposed to the colored ones is the 95% confidence contour....
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...As pointed out by Torrence and Compo (1998) a power spectrum analysis of geophysical data requires the definition of a null-hypothesis to be used as term10 of comparison of the actual signal spectrum and for the identification of significant features within it....
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...Herewith we refer the reader to the comprehensive description of the problem described by Torrence and Compo (1998)....
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TL;DR: Wavelet transforms are recent mathematical techniques, based on group theory and square integrable representations, which allows one to unfold a signal, or a field, into both space and scale, and possibly directions.
Abstract: Wavelet transforms are recent mathematical techniques, based on group theory and square integrable representations, which allows one to unfold a signal, or a field, into both space and scale, and possibly directions. They use analyzing functions, called wavelets, which are localized in space. The scale decomposition is obtained by dilating or contracting the chosen analyzing wavelet before convolving it with the signal. The limited spatial support of wavelets is important because then the behavior of the signal at infinity does not play any role. Therefore the wavelet analysis or syn thesis can be performed locally on the signal, as opposed to the Fourier transform which is inherently nonlocal due to the space-filling nature of the trigonometric functions. Wavelet transforms have been applied mostly to signal processing, image coding, and numerical analysis, and they are still evolving. So far there are only two complete presentations of this topic, both written in French, one for engineers (Gasquet & Witomski 1 990) and the other for mathematicians (Meyer 1 990a), and two conference proceedings, the first in English (Combes et al 1 989), the second in French (Lemarie 1 990a). In preparation are a textbook (Holschneider 199 1 ), a course (Dau bee hies 1 99 1), three conference procecdings (Mcyer & Paul 199 1 , Beylkin et al 199 1b, Farge et al 1 99 1), and a special issue of IEEE Transactions
2,770 citations
432 citations
"One year of 222 Rn concentration in..." refers background in this paper
...The figures also display the red noise spectrum obtained from the parameterization by Gilman et al. (1963) and the 95% confidence spectrum....
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...For the sake of completeness it should be mentioned that the detailed studies of Guedalia et al. (1970), 10 Clements and Wilkening (1974), Guedalia et al....
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Harvard University1, University of California, Irvine2, National Center for Atmospheric Research3, York University4, Lawrence Livermore National Laboratory5, Langley Research Center6, University of Washington7, University of Cambridge8, Max Planck Society9, Centre national de la recherche scientifique10, Georgia Institute of Technology11, German Aerospace Center12, University at Albany, SUNY13, University of East Anglia14, Royal Netherlands Meteorological Institute15
TL;DR: In this article, simulations of 222Rn and other short-lived tracers are used to evaluate and intercompare the representations of convective and synoptic processes in 20 global atmospheric transport models.
Abstract: Simulations of 222Rn and other short-lived tracers are used to evaluate and intercompare the representations of convective and synoptic processes in 20 global atmospheric transport models. Results show that most established three-dimensional models simulate vertical mixing in the troposphere to within the constraints offered by the observed mean 222Rn concentrations and that subgrid parameterization of convection is essential for this purpose. However, none of the models captures the observed variability of 222Rn concentrations in the upper troposphere, and none reproduces the high 222Rn concentrations measured at 200 hPa over Hawaii. The established three-dimensional models reproduce the frequency and magnitude of high-222Rn episodes observed at Crozet Island in the Indian Ocean, demonstrating that they can resolve the synoptic-scale transport of continental plumes with no significant numerical diffusion. Large differences between models are found in the rates of meridional transport in the upper troposphere (interhemispheric exchange, exchange between tropics and high latitudes). The four two-dimensional models which participated in the intercomparison tend to underestimate the rate of vertical transport from the lower to the upper troposphere but show concentrations of 222Rn in the lower troposphere that are comparable to the zonal mean values in the three-dimensional models.
279 citations
"One year of 222 Rn concentration in..." refers methods in this paper
...…Figures J I J I Back Close Full Screen / Esc Print Version Interactive Discussion EGU tion, also evident in the present dataset, points clearly towards the need of a parameterization of the process within global models (e.g. Jacob et al., 1997; Dentener et al., 1999; Josse et al., 2004)....
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TL;DR: The effect of large-scale atmospheric pressure changes on the 222Rn flux across the soil-air interface is investigated in this paper, where a simple model of molecular diffusion combined with pressure-induced transport in the soil has been confirmed by laboratory experiments using a vertical column of 226Ra-bearing sand.
Abstract: The effect of large-scale atmospheric pressure changes on the 222Rn flux across the soil-air interface is investigated. Field data collected during 1972 and 1973 show that pressure changes of 1–2% associated with the passage of frontal systems produce changes in the 222Rn flux from 20 to 60%, depending upon the rate of change of pressure and its duration. A simple model of molecular diffusion combined with pressure-induced transport in the soil has been confirmed by laboratory experiments using a vertical column of 226Ra-bearing sand. On the basis of this model, pressure changes of 10–20 mbar occurring over a period of 1–2 days produce Darcy velocities of the order of 10−4 cm s−1 near the surface of a soil having a permeability of 10−8 cm2. The corresponding variations in the 222Rn flux predicted by the model are in agreement with those observed from valley alluvium in central New Mexico.
278 citations
"One year of 222 Rn concentration in..." refers background in this paper
...(1970), 10 Clements and Wilkening (1974), Guedalia et al. (1980), Ishimori et al. (1998) and Katoaka et al. (2003), indicate that only sudden drops or increases of pressure (of the order of 10 to 15 hPa) can cause a modification of the radon emission....
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...For the sake of completeness it should be mentioned that the detailed studies of Guedalia et al. (1970),10 Clements and Wilkening (1974), Guedalia et al. (1980), Ishimori et al. (1998) and Katoaka et al. (2003), indicate that only sudden drops or increases of pressure (of the order of 10 to 15 hPa)…...
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