Seasonal variations of aerosol residence time in the lower atmospheric boundary layer

During a one year period, from Jan. 2002 up to Dec. 2002, approximately 130 air samples were analyzed to determine the atmospheric air activity concentrations of short- and long-lived (222Rn) decay products 214Pb and 210Pb. The samples were taken by using a single-filter technique and gamma-spectrometry was applied to determine the activity concentrations. A seasonal fluctuation in the concentration of 214Pb and 210Pb in surface air was observed. The activity concentrations of both radionuclides were observed to be relatively higher during the winter/autumn season than in spring/summer season. The mean activity concentration of 214Pb and 210Pb within the whole year was found to be 1.4+/-0.27 Bq m(-3) and 1.2+/-0.15 mBq m(-3), respectively. Different 210Pb:214Pb activity ratios during the year varied between 1.78 x 10(-4) and 1.6 x 10(-3) with a mean value of 8.9 x 10(-4) +/- 7.6 x 10(-5). From the ratio between the activity concentrations of the radon decay products 214Pb and 210Pb a mean residence time (MRT) of aerosol particles in the atmosphere of about 10.5+/-0.91 d could be estimated. The seasonal variation pattern shows relatively higher values of MRT in spring/summer season than in winter/autumn season. The MRT data together with relative humidity (RH), air temperature (T) and wind speed (WS), were used for a comprehensive regression analysis of its seasonal variation in the atmospheric air.     

Natural radioactivity measurements in building materials in Southern Lebanon

Using gamma-spectroscopy and CR-39 detector, concentration C of naturally occurring radioactive nuclides (226)Ra, (222)Rn, (214)Bi, (228)Ac, (212)Pb, (212)Bi and (40)K, has been measured in sand, cement, gravel, gypsum, and paint, which are used as building materials in Lebanon. Sand samples were collected from 10 different sandbank locations in the southern part of the country. Gravel samples of different types and forms were collected from several quarries. White and gray cement fabricated by Shaka Co. were obtained. gamma-spectroscopy measurements in sand gave Ra concentration ranging from 4.2+/-0.4 to 60.8+/-2.2 Bq kg(-1) and Ra concentration equivalents from 8.8+/-1.0 to 74.3+/-9.2 Bq kg(-1). The highest Ra concentration was in gray and white cement having the values 73.2+/-3.0 and 76.3+/-3.0 Bq kg(-1), respectively. Gravel results showed Ra concentration between 20.2+/-1.0 and 31.7+/-1.4 Bq kg(-1) with an average of 27.5+/-1.3 Bq kg(-1). Radon concentration in paint was determined by CR-39 detector. In sand, the average (222)Rn concentration ranged between 291+/-69 and 1774+/-339 Bq m(-3) among the sandbanks with a total average value of 704+/-139 Bq m(-3). For gravel, the range was found to be from 52+/-9 to 3077+/-370 Bq m(-3) with an average value of 608+/-85 Bq m(-3). Aerial and mass exhalation rates of (222)Rn were also calculated and found to be between 44+/-7 and 2226+/-267 mBq m(-2)h(-1), and between 0.40+/-0.07 and 20.0+/-0.3 mBq kg(-1)h(-1), respectively.     

Indoor radon (222Rn) concentration measurements in Cyprus using high-sensitivity portable detectors

Using high-sensitivity radon ((222)Rn) portable detectors (passive electronic devices of the type RADIM3), the airborne (222)Rn concentration in the interior of various Cypriot buildings and dwellings was measured. For each preselected building and dwelling, a calibrated detector was put into a closed room, and the (222)Rn concentration was registered in sampling intervals of 2 to 4 h for a total counting time of typically 48 h. (222)Rn activity concentrations were found to be in the range of 6.2 to 102.8 Bq m(-3), with an overall arithmetic mean value of (19.3+/-14.7) Bq m(-3). This value is by a factor of two below the world average (population-weighted) value of 39 Bq m(-3). The total annual effective dose equivalent to the Cypriot population was calculated to be between 0.16 and 2.6 mSv with an overall arithmetic mean value of (0.49+/-0.37) mSv.     

Bronchial Rn dose survey for residences

The bronchial dosimeter for Rn progeny proposed by Yu and Guan in 1998 was employed to survey the bronchial dose from Rn progeny in 30 residences in Hong Kong. An average bronchial deposition fraction of Rn progeny was obtained as 0.0334, which gave an average dose conversion factor (DCF) of 8.5 mSv WLM-1. The mean values of potential alpha energy concentration (PAEC) deposited in the tracheobronchial region (PAECT-B), total PAEC in air (PAECT), annual effective dose (E), concentration of Rn gas (RC) and annual dose conversion factor (ADCF) for all the residential sites combined were 0.11 +/- 0.05, 3.1 +/- 1.4 mWL, 1.2 +/- 0.5 mSv yr-1, 23 +/- 10 Bq m-3 and 0.055 +/- 0.020 (mSv yr-1 per Bqm-3), respectively, with air-conditioned sites (AC sites) and non-AC sites having significantly different mean ADCF values. The indoor relative humidity affected PAECT and RC with high confidence levels (> 95%).     

A nationwide survey of outdoor radon concentration in Japan

Nationwide outdoor radon (222Rn) concentrations in Japan were measured to survey the environmental outdoor 222Rn level and to estimate the effective dose to the general public from 222Rn and its progeny. The 222Rn concentration was measured with a passive-type radon monitor. The 222Rn monitors were installed at about 700 points throughout Japan from 1997 to 1999. The annual mean 222Rn concentration in Japan was estimated from four quarters measurements of 47 prefectures in Japan. Nationwide outdoor mean 222Rn concentration was 6.1 Bq m(-3). This was about 40% of the indoor 222Rn concentration in Japan. The 222Rn concentration in Japan ranged from 3.3 Bq m(-3) in the Okinawa region to 9.8 Bq m(-3) in the Chugoku region, reflecting geological characteristics. Seasonal variation of outdoor 222Rn concentration was also found to be lowest in July to September, and highest in October to December. From the results of this 222Rn survey and previous indoor 222Rn survey program, the effective dose to the general public from 222Rn and its progeny was estimated to be 0.45 mSv y(-1).     

Contribution of (222)Rn-bearing water to the occupational exposure in thermal baths

The present study investigates the short- and long-term effects of radon ((222)Rn) released from water on the progeny exposure in a thermal spa. For the purposes of this work, the Polichnitos spa was used as a case study. The bathroom was supplied with water containing 110-210 kBq m(-3) of (222)Rn. The (222)Rn concentration in air and the short-lived (222)Rn progenies in attached and unattached form were monitored into the bathroom and the surrounding premises. The equilibrium factor (F-factor) and the unattached fraction were estimated. The results of this study show that water flow during bath filling is by far the dominant mechanism by which (222)Rn is released in the air of the bathroom. The progeny exposure was correlated linearly with the (222)Rn concentration in the entering water. The annual effective dose received by a worker was found to be below the lower limit value of 3 mSv recommended by ICRP 65. The dose limit was exceeded only for water containing more than 300 kBq m(-3).     

A combined method for evaluating radon and progeny in waters and its use at Guarani aquifer, São Paulo State, Brazil

A combined method for evaluating radon (222Rn) and progeny (214Pb and 214Bi) in water was developed by using inexpensive alpha scintillation counting and gamma ray spectrometry through NaI(Tl) scintillation detectors. A groundwater sample collected at the Po?os de Caldas alkaline massif in Brazil was submitted to the technique in order to assure its applicability by comparing the volumetric activities by different methods. Similar volumetric activity was determined for 214Pb and 214Bi in the sample analyzed that is compatible with the expected condition of radioactive equilibrium between these nuclides. The combined method was successfully used to analyze groundwater samples from Guarani aquifer in S?o Paulo State, Brazil, and the results of the measurements indicated that 214Pb and 214Bi provide useful information concerning the evaluation of the drinking water quality in terms of radiological aspects. This is because they are directly identified in the water samples, without the need of requiring the assumption of the establishment of the transient equilibrium condition with its parent 222Rn.     

A survey of indoor workplace radon concentration in Japan

Radon ((222)Rn) concentration was measured at indoor workplaces in Japan to estimate effective dose to the public from (222)Rn and its progeny. Measurements were made from 2000 to 2003 at 705 sites in four categories of office, factory, school and hospital. Passive type Rn monitors equipped with two sheets of polycarbonate thin films for measuring radon concentrations were installed at observation sites and replaced every 3 months to observe seasonal variations in (222)Rn concentrations. The range of annual mean (222)Rn concentrations for all sites was 1.4-182 Bq m(-3), with the arithmetic mean and standard deviation were 20.8 and 19.5 Bq m(-3). Annual mean (222)Rn concentration observed at office, factory, school and hospital were 22.6, 10.1, 28.4 and 19.8 Bq m(-3), respectively. Seasonal variations in (222)Rn concentrations at offices, schools and hospitals were similar to those found in dwellings, and variations in factories were similar to those found in outdoor environments. (222)Rn concentration observed in every quarter period was found to decrease as follows: school>office>hospital>factory. The average effective dose to the public due to (222)Rn was estimated to be 0.41 mSv y(-1) weighted by the working population. Considering the (222)Rn exposure in indoor workplaces, effective dose to the general public is estimated to be in the range from approximately 0.42 to 0.52 mSv y(-1).     

Natural radionuclides in bottled water in Austria

Concentration levels of 226Ra, 222Rn and 210Pb were analyzed in domestic bottled waters commercially available in Austria. Concentrations up to 0.23 Bq/l, with a geometric mean of 0.041 Bq/l were found for 226Ra. Concentrations for 222Rn ranged from <0.12-18 Bq/l, the geometric mean being 0.54 Bq/l. Lead-210 was analyzed in selected samples, the concentrations ranging from <2 to 34 mBq/l, with a geometric mean of 4.7 mBq/l. Ingestion doses resulting from consumption of these waters were calculated for the geometric mean and the maximum concentrations of the three radionuclides. The effective dose equivalents for different age groups of the population due to the intake of 226Ra range from 0.001 to 0.22 mSv/y and of 210Pb from 0.0003 to 0.05 mSv/y. Ingestion doses from 222Rn are low compared to those from 226Ra and 210Pb, ranging from 0.0001 to 0.011 mSv/y for adults and children, respectively. The doses are compared to the total ingestion dose from dietary intake of natural radionuclides on an annual basis.     

222Rn and 220Rn concentrations in soil gas of Karkonosze-Izera Block (Sudetes, Poland)

Soil gas 222Rn and 220Rn concentrations were measured at 18 locations in the Karkonosze-Izera Block area in southwestern Poland. Measurements were carried out in surface air and at sampling depths of 10, 40 and 80 cm. Surface air 222Rn concentrations ranged from 4 to 2160 Bq m(-3) and 220Rn ranged from 4 to 228 Bq m(-3). The concentrations for 10 and 40 cm varied from 142 Bq m(-3) to 801 kBq m(-3) and 102 Bq m(-3) to 64 kBq m(-3) for 222Rn and 220Rn, respectively. At 80 cm 222Rn concentrations ranged from 94 Bq m(-3) to >1 MBq m(-3). The 220Rn concentrations at 80 cm varied from 45 Bq m(-3) to 48 kBq m(-3). The concentration versus depth profiles for 222Rn differed for soils developed on fault zones, uranium deposits or both. Atmospheric air temperature and soil gas 222Rn and 220Rn were negatively correlated. At sampling sites with steep slopes, 220Rn concentrations decreased with depth.     

Distribution of (226)Ra-(210)Pb-(210)Po in marine biota and surface sediments of the Red Sea, Sudan

Activity concentration levels and ratios of (226)Ra, (210)Pb and (210)Po are presented in multicellular marine algae, molluscs, coral as well as in surface marine sediments collected from the shallower waters of the fringing reefs area extending towards north and south (Flamingo bay) of PortSudan harbour, Sudan. The analyses were performed adopting alpha-spectrometry, liquid scintillation and Cerenkov counting techniques. Surface sediments from this coastal region are poor in their radioactivity content in contrast to similar data reported from different coastal areas around the globe. There is surface enrichment of (210)Pb and (210)Po with respect to their progenitor (226)Ra as it is evident from the activity ratios of (210)Pb/(226)Ra (3.03+/-1.79) and (210)Po/(226)Ra (2.23+/-1.56). Among marine plants and animals investigated, the green algae species, Halimeda, and coral species, Favites, show substantial concentration of radium at 8.2Bq/kg and 21.9Bq/kg dry weight, respectively. Similarly, the highest concentration of (210)Po was met in Favites at 38.7Bq/kg followed by brown algae, Cystoseria sp., at 32.6Bq/kg. There is no variation seen among algal species for (210)Pb uptake, however, converse to radium and polonium, Favites (coral) was found to contain the minimum concentration of lead (3.88Bq/kg). In most species there is preferential accumulation of polonium over its parent radium as indicated by (210)Po:(226)Ra activity ratio with Cystoseria (brown algae) showing the highest value at 8.81. On the other hand, (210)Po:(210)Pb activity concentration ratio revealed that coral species Favites (9.97) and the brown algae Sargassum (1.85) have a greater tendency to accumulate (210)Po over (210)Pb, while in the rest of species; this ratio is less than unity.     

Systematics of radon at the Wairakei geothermal region, New Zealand

222Rn and 220Rn in geothermal steam at Wairakei, NZ, range from 11 to 19, 500 Bq kg-1, and 25 to 16, 700 Bq kg-1, respectively, but do not cause toxic concentrations in air. The wide ranges are mainly due to differences in different physical conditions underground (e.g. thin silica diffusion barriers), not geochemical differences. Groundwater Rn from outside the area probably plays only a minor role. 210Po was found present in non-toxic levels in the steam. Historical records showed little change in Rn concentration over several decades, therefore potentially hazardous concentrations might be predicted from early exploration. 220Rn concentrations at Wairakei should decrease as the field becomes steam-dominated. Rock surfaces were variably leached or enriched with U, Th, Ra and 210Pb, providing a possible model for deposition in cooler regions near the field. Estimates of 222Rn permeability ranged from 2 to 77% of the maximum possible, with a median of 13%.     

Variation of the activity concentrations and fluxes of natural (210Po, 210Pb) and anthropogenic (239,240Pu, 137Cs) radionuclides in the Strait of Gibraltar (Spain)

The activity concentrations and fluxes of natural (210Pb, 210Po) and anthropogenic (239,240Pu, 137Cs) radionuclides have been determined in the different water masses crossing the Strait of Gibraltar. New data have been gathered during four multidisciplinary and multinational sampling campaigns, performed between 1997 and 1999 within the framework of the CANIGO-FLUGIST Project. Mean activity concentrations of 210Po (1.53+/-0.34 Bq m(-3), n = 30) and 210Pb (1.16+/-0.50 Bq m(-3), n = 31) in the Atlantic water entering the Mediterranean basin are about double those measured in the Mediterranean outflow, namely 0.84+/-0.34 Bq m(-3) (n = 22) for 210Po and 0.66+/-0.34 Bq m(-3) (n = 22) for 210Pb. The opposite trend is observed for 231,240Pu, with average concentrations of 9.9+/-3.0 mBq m(-3) (n = 29) in the incoming Atlantic flow and 22.0+/-3.0 mBq m(-3) (n = 22) in the outpouring Mediterranean water. In the case of 137Cs, the same concentrations were quantified in the waters moving inwards (2.52+/-0.28 Bq m(-3), n = 27) and outwards (2.14+/-0.52 Bq m(-3), n = 21) from the Mediterranean Sea. On this basis, the Mediterranean basin experiences a net annual input flux of 14 TBq of 210Pb and 19 TBq of 210Po, and a net annual loss of 0.34 TBq of 239,240Pu, while--at present--137Cs input and output fluxes appear to be balanced.     

Radon flux at King George Island, Antarctic Peninsula

Fluxes of 222Rn from the ice-free terrain to the atmosphere were measured directly, for the first time, at the Brazilian Antarctic Station Ferraz during the summer field campaign of 1998/99. Average value for the flux was 7.7 +/- 4.8 x 10(-2) atoms cm(-2) s(-1) and it ranged between 0.21 x 10(-2) atoms cm(-2) s(-1) and 28 x l0(-2) atoms cm(-2) s(-1). The average flux of 220Rn was estimated to be 23 atoms cm(-2) s(-1), using a combination of two techniques: nuclear track detection and alpha spectrometry of radon daughters. It was found that the production of radon by uranium (41.54 + /-7.17 Bq kg(-1)) and thorium (57.97 +/- 12.14 Bq kg(-1)) equivalent soil contents, and a diffusion coefficient derived from experimental data for the local terrain could account for this average flux. Nevertheless, the large surges of 222Rn in the atmosphere frequently observed for that area could not be explained by this flux only.     

Temporal variation of 212Pb concentration in outdoor air of Milan and a comparison with 214Bi

Continuous measurement of hourly concentrations of 212Pb attached to aerosol particles was carried out during the whole year 2000 in the outdoor air of Milan (Italy). An improved experimental method based on on-line alpha spectroscopy during atmospheric particulate matter sampling allowed the contemporary determination of 212Pb and 214Bi through the deconvolution of the alpha energy spectral distribution analysis. The 212Pb hourly concentrations were about 100 times lower than 214Bi but showed a similar characteristic diurnal time trend. However, the influence of meteorological parameters such as rain and wind was more evident in 212Pb than in 214Bi concentrations. The 212Pb average annual concentration was 0.090 +/- 0.060 Bq/m3 with daily mean concentration varying from 0.013 to 0.333 Bq/m3.     

Occurrence of 222Rn, 226Ra, 228Ra and U in groundwater in Fujian Province, China

222Rn, 226Ra, 228Ra and U were determined in a total of 552 groundwater samples collected throughout Fujian Province of China. The geometric mean concentrations of 222Rn, 226Ra, 228Ra and total U in the groundwater were 147.8 kBq m-3, 12.7 Bq m-3, 30.2 Bq m-3 and 0.54 microgram kg-1, respectively. High groundwater 222Rn was explained by the predominantly granitic rock aquifers in Fujian. A lifetime risk of 1.7 x 10(-3) was estimated for the ingestion of groundwater 222Rn. High ratios of 228Ra to 226Ra contents (geometric mean of 2.4) and their disproportion suggest that 228Ra should also be measured in the assessment of population doses from drinking water in the regions of high rock or soil 232Th. No significant correlation between the 222Rn concentrations in groundwater and air was found.     

Development and calibration of a portable radon sampling system for groundwater Rn activity concentration measurements

The assembling of a system for field sampling and activity concentration measurement of radon dissolved in groundwater is described. Special attention is given in presenting the calibration procedure to obtain the radon activity concentration in groundwater from the raw counting rate registered in a portable scintillation detector and in establishing the precision of the activity concentration measurements. A field procedure was established and the system tested during one year of monthly observations of ²²²Rn activity concentration in groundwater drawn from two wells drilled on metamorphic rocks exposed at Eastern São Paulo State, Brazil. The observed mean ²²²Rn activity concentrations are 374 Bq/dm³ in one well and about 1275 Bq/dm³ in the other one. In both wells the ²²²Rn activity concentrations showed a seasonal variation similar to variations previously reported in the literature for the same region.     

Natural radioactivity measurements in the city of Ptolemais (Northern Greece)

Specific activities of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured by means of gamma-ray spectrometry in surface soil samples collected from the city of Ptolemais, which is located near lignite-fired power plants. The mean activity values for (238)U, (226)Ra, (232)Th and (40)K were found to be 42+/-11, 27+/-6, 36+/-5 and 496+/-56 Bq kg(-1), respectively. These values fall within the range of typical world and Greek values for soil. The indoor radon concentration levels, which were also measured in 66 dwellings by means of SSNTD, ranged from 12 to 129 Bq m(-3), with an average value of 36+/-2 Bq m(-3). This value is close to world and Greek average values for indoor radon concentrations. The total effective dose due to outdoor external irradiation of terrestrial origin and to indoor internal irradiation from the short-lived decay products of (222)Rn was estimated to be 1.2 mSv y(-1) for adults, which is lower than the global effective dose due to natural sources of 2.4 mSv y(-1).     

Present status of 222Rn in groundwater in Extremadura

Radon-222 was measured in groundwater sources of Extremadura (Spain), analyzing 350 samples from private and public springs, wells, and spas by liquid scintillation counting (LSC) and gamma spectrometry. The (222)Rn activity concentrations ranged from 0.24 to 1168BqL(-1). The statistical analysis showed a log-normal distribution with a mean of (111+/-7)BqL(-1) and a median of (36+/-3)BqL(-1). A hydrogeological study revealed correlations between the activity concentration and the aquifer material's characteristics. A map of (222)Rn in groundwater was elaborated and compared with the natural gamma radiation map for this region. About 35% of the samples showed (222)Rn activity concentrations above the Euratom recommended limit of 100BqL(-1). Three uranium series radionuclides ((238)U, (234)U, and (226)Ra) were also assayed by alpha-particle spectrometry, estimating the annual effective dose due to the presence of these natural radionuclides in drinking water.     

The temporal variations of (7)Be, (210)Pb and (210)Po in air in England

We have conducted measurements of naturally occurring radionuclides (7)Be, (210)Pb and (210)Po in air at ground level at Chilton, Oxfordshire, England. The sampling and analysis regime for the latter two isotopes has been optimised to minimise uncertainties in measurement due to decay of (210)Po and in-growth of (210)Pb during the sampling and analysis period. Analysis times were reduced by using Cerenkov counting to assay the (210)Bi daughter of (210)Pb. Monthly data collected over a four-year period are presented and discussed. (7)Be activity concentrations appear to peak in spring. (210)Pb activity concentrations also follow a seasonal trend reflecting different (222)Rn emanation rates from soil during winter and summer. Data for (210)Po show no such trend.