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.
Citations
More filters
TL;DR: In this paper, the authors synthesize the published literature on subsurface airflow driven by natural forcings such as atmospheric pressure fluctuations, topographic effect, water table fluctuations, and water infiltration.
Abstract: [1] Subsurface airflow in unsaturated zones induced by natural forcings is of importance in many environmental and engineering fields, such as environmental remediation, water infiltration and groundwater recharge, coastal soil aeration, mine and tunnel ventilation, and gas exchange between soil and atmosphere. This review synthesizes the published literature on subsurface airflow driven by natural forcings such as atmospheric pressure fluctuations, topographic effect, water table fluctuations, and water infiltration. The present state of knowledge concerning the mechanisms, analytical and numerical models, and environmental and engineering applications related to the naturally occurring airflow is discussed. Airflow induced by atmospheric pressure fluctuations is studied the most because of the applications to environmental remediation and transport of trace gases from soil to atmosphere, which are very important in understanding biogeochemical cycling and global change. Airflow induced by infiltration is also an extensively investigated topic because of its implications in rainfall infiltration and groundwater recharge. Airflow induced by water table fluctuations is important in coastal areas because it plays an important role in coastal environmental remediation and ecological systems. Airflow induced by topographic effect is studied the least. However, it has important applications in unsaturated zone gas transport and natural ventilation of mines and tunnels. Finally, the similarities and differences in the characteristics of the air pressure and airflow are compared and future research efforts are recommended.
88 citations
Cites background from "One year of 222 Rn concentration in..."
...In addition, both positive [Galmarini, 2006] and negative [Klusman and Jaacks, 1987; Schery et al., 1989; Hutter, 1996; Iakovleva and Ryzhakova, 2003; Smetanov a et al., 2010] correlations between radon concentration and atmospheric pressure were found....
[...]
...Some researchers stated that only sudden drops or increases of atmospheric pressure (of the order of 1.0–1.5 kPa) can affect the radon exhalation [Kataoka et al., 2003; Galmarini, 2006]....
[...]
TL;DR: In this article, the authors argue that single-height radon observations should not be used quantitatively as an indicator of atmospheric stability without prior conditioning of the time series to remove contributions from larger-scale "non-local" processes.
Abstract: . Radon is increasingly being used as a tool for quantifying stability influences on urban pollutant concentrations. Bulk radon gradients are ideal for this purpose, since the vertical differencing substantially removes contributions from processes on timescales greater than diurnal and (assuming a constant radon source) gradients are directly related to the intensity of nocturnal mixing. More commonly, however, radon measurements are available only at a single height. In this study we argue that single-height radon observations should not be used quantitatively as an indicator of atmospheric stability without prior conditioning of the time series to remove contributions from larger-scale "non-local" processes. We outline a simple technique to obtain an approximation of the diurnal radon gradient signal from a single-height measurement time series, and use it to derive a four category classification scheme for atmospheric stability on a "whole night" basis. A selection of climatological and pollution observations in the Sydney region are then subdivided according to the radon-based scheme on an annual and seasonal basis. We compare the radon-based scheme against a commonly used Pasquill–Gifford (P–G) type stability classification and reveal that the most stable category in the P–G scheme is less selective of the strongly stable nights than the radon-based scheme; this lead to significant underestimation of pollutant concentrations on the most stable nights by the P–G scheme. Lastly, we applied the radon-based classification scheme to mixing height estimates calculated from the diurnal radon accumulation time series, which provided insight to the range of nocturnal mixing depths expected at the site for each of the stability classes.
77 citations
TL;DR: The seasonality of indoor Rn concentration measured in Austria is investigated as a function of other factors that influence indoors Rn, with higher Rn levels in winter.
63 citations
TL;DR: In this paper, a technique recently developed for stability classification using a research-quality dual-flow-loop two-filter radon detector is adapted for use with a commercially available radon-based stability monitor.
57 citations
TL;DR: One year of radon, benzene and carbon monoxide (CO) concentrations were analyzed to characterise the combined influences of variations in traffic density and meteorological conditions on urban air quality in Bern, Switzerland as mentioned in this paper.
Abstract: One year of radon, benzene and carbon monoxide (CO) concentrations were analysed to characterise the combined influences of variations in traffic density and meteorological conditions on urban air quality in Bern, Switzerland. A recently developed radon-based stability categorisation technique was adapted to account for seasonal changes in day length and reduction in the local radon flux due to snow/ice cover and high soil moisture. Diurnal pollutant cycles were shown to result from an interplay between variations in surface emissions (traffic density), the depth of the nocturnal atmospheric mixing layer (dilution) and local horizontal advection of cleaner air from outside the central urban/industrial area of this small compact inland city. Substantial seasonal differences in the timing and duration of peak pollutant concentrations in the diurnal cycle were attributable to changes in day length and the switching to/from daylight-savings time in relation to traffic patterns. In summer, average peak benzene concentrations (0.62 ppb) occurred in the morning and remained above 0.5 ppb for 2 hours, whereas in winter average peak concentrations (0.85 ppb) occurred in the evening and remained above 0.5 ppb for 9 hours. Under stable conditions in winter, average peak benzene concentrations (1.1 ppb) were 120% higher than for well-mixed conditions (0.5 ppb). By comparison, summertime peak benzene concentrations increased by 53% from well-mixed (0.45 ppb) to stable nocturnal conditions (0.7 ppb). An idealised box model incorporating a simple advection term was used to derive a nocturnal mixing length scale based on radon, and then inverted to simulate diurnal benzene and CO emission variations at the city centre. This method effectively removes the influences of local horizontal advection and stability-related vertical dilution from the emissions signal, enabling a direct comparison with hourly traffic density. With the advection term calibrated appropriately, excellent results were obtained, with high regression coefficients in spring and summer for both benzene (r 2 ~0.90–0.96) and CO (r 2 ~0.88–0.98) in the two highest stability categories. Weaker regressions in winter likely indicate additional contributions from combustion sources unrelated to vehicular emissions. Average vehicular emissions during daylight hours were estimated to be around 0.503 (542) kg km −2 h −1 for benzene (CO) in the Bern city centre. Keywords: radon, air quality, urban, atmospheric stability, traffic density, vehicle emissions (Published: 6 September 2016) Citation: Tellus B 2016, 68, 30967, http://dx.doi.org/10.3402/tellusb.v68.30967
42 citations
Cites background from "One year of 222 Rn concentration in..."
...…of the ubiquitous surface-emitted passive tracer radon (e.g. Allegrini et al., 1994; Duenas et al., 1996; Perrino, 2001, 2012; Avino et al., 2003; Galmarini, 2006; Sesana et al., 2006; Chambers et al., 2011, 2015a, 2015b, 2016; Wang et al., 2013; Williams et al., 2013; Kondo et al., 2014; Pitari…...
[...]
References
More filters
TL;DR: 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.
127 citations
"One year of 222 Rn concentration in..." refers background in this paper
...For a detailed review on the radon studies and sampling techniques in atmospheric science refer to Zahorowski et al. (2004).10 In the present study a one-year time series of radon-222 measured in the atmospheric surface layer (ASL) is analyzed....
[...]
TL;DR: In this paper, the authors used the global off-line tracer transport model TM3 at 3 different resolutions to evaluate and document model performance and associated uncertainties, and found that the main cause of model deviations is probably related to uncertainties in the meteorological input data set provided by the European Centre for Medium Range Weather Forecasts (ECMWF) model and uncertainties involving sub-grid scale parameterization of vertical transport, e.g., diffusion and convection.
Abstract: The short-lived radionuclide Rn 222 is emitted at a fairly constant rate from the continents and is a good surrogate for studying the transport of “air pollution” from polluted continental areas to clean, remote regions. The large concentration gradients of 2–3 orders of magnitude which exist between the continents and the remote atmosphere present a major challenge to the modelling of horizontal and vertical atmospheric transport. We use the global off-line tracer transport model TM3 at 3 different resolutions. Input to the model consists of meteorological data for the year 1993 obtained from the European Centre for Medium Range Weather Forecasts (ECMWF). The same meteorological data is used to constrain the climate model ECHAM4-T42-L19. Using these meteorological data, Rn 222 simulations are used to evaluate and document model performance and associated uncertainties. High time-resolution measurements made at 2 continental stations, 2 stations under continental influence and 4 remote sites, and aircraft measurements obtained during the NARE aircraft campaign are used for a detailed comparison. Although in specific regions there are inter-model differences of up to a factor of 2 in the calculated boundary layer concentrations, these differences are not translated into a better performance of either model for the stations used for comparison. We generally obtain high correlations of model results and measurements; these range from r = 0.6–0.8 for the continental and coastal stations and 0.5–0.6 for the remote sites. Calculated mean concentrations and corresponding standard deviations generally agree favourably with observations, lending credibility to the usefulness of our models for evaluating transport of air pollutants from continental sources to remote regions. The main cause of model deviations is probably related to uncertainties in the meteorological input data set provided by the ECMWF model and to a lesser extent by our knowledge of the spatial distribution of Rn 222 emissions and uncertainties involving sub-grid scale parameterization of vertical transport, e.g., diffusion and convection. DOI: 10.1034/j.1600-0889.1999.t01-2-00001.x
126 citations
"One year of 222 Rn concentration in..." refers background or methods in this paper
...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)....
[...]
...Similarly intensive research has been conducted at global scale where radon is used for global atmospheric chemistry models evaluation (e.g. Dentener et al., 1999), as well as for the estimate of the fluxes of the atmospheric constituents or pollutants....
[...]
...…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)....
[...]
TL;DR: In this paper, a rate equation is derived which describes the development of the boundary-layer height under stable conditions as a function of time, taking the form of a linear relaxation equation; its solution is forced toward an equilibrium value.
Abstract: A rate equation is derived which describes the development of the boundary-layer height under stable conditions as a function of time. It takes the form of a linear relaxation equation; its solution is forced toward an equilibrium value. The equilibrium height is connected to the work done by the ageostrophic wind in the boundary layer. The time scale of the relaxation process increases monotonically from a few hours shortly after sunset to a value of the order of 10 h later on. This means that the boundary-layer height evolves very slowly, which may lead to the unwarranted impression that stationary conditions have been reached. The main features of the rate equation are confirmed by comparison with the results of computer simulations and with field observations of the boundary-layer height during clear nights.
72 citations
TL;DR: In this article, 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).
Abstract: 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 212Pb 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 222Rn 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.
64 citations
TL;DR: In this paper, a wavelet analysis was used to quantify the duration and strength of turbulent activity in the very stable nocturnal boundary layer of the Lower Fraser Valley in British Columbia, Canada.
Abstract: Turbulence in the very stable nocturnal boundary layer is weak, patchy and intermittent. Near the surface isolated bursts of turbulent activity, characterised by abrupt changes in vertical velocity variance, have been shown to play an important role in determining the vertical transport of pollutants. However, there is little consensus as to the most appropriate methods for identifying or analysing the characteristics of intermittent turbulence that are of direct relevance to air quality studies. This paper presents an original technique, based on wavelet analysis, to objectively isolate intermittent turbulent ‘bursts’ within vertical velocity time series. The technique permits the quantitative description of global intermittency and can be used to assess the duration and strength of turbulence within a time series. The technique is applied to a dataset from a summer field experiment in the Lower Fraser Valley, British Columbia, 1998. A very stable nocturnal boundary layer was observed in this region of complex terrain during anticyclonic synoptic conditions. During the 11 nights studied turbulent activity was characterised (within each 30-min time series) by three to four individual bursts persisting for less than 10 min in total. The implications of these results for air quality studies are discussed within the context of the vertical mixing of ozone (stored within the residual layer) to the surface. Results show that, despite the complexity of the processes determining nocturnal surface ozone concentration, the strength and duration of turbulent bursts can play an important role in determining local surface concentrations.
63 citations
Additional excerpts
...…and Attié, 1999; Attié and Durand, 2003; ACPD 5, 12895–12937, 2005 222Rn concentration in the atmospheric surface layer S. Galmarini Title Page Abstract Introduction Conclusions References Tables Figures J I J I Back Close Full Screen / Esc Print Version Interactive Discussion EGU Salmond, 2005)....
[...]