Seasonal variation of 210Pb activity concentration in outdoor air of Milan (Italy)

Weekly measurements of 210Pb activity concentration on aerosol particles were performed at ground level in outdoor air in Milan (Italy) during the years 2000-2001. The experimental method was based on the delayed alpha spectrometry of in-grown 210Po activity detected on airborne particles collected on a filter support. On the same filter the 214Pb activity concentration was also measured during the sampling. 210Pb weekly concentration values showed a great variability and the average monthly values exhibited a seasonal pattern characterised by maxima in winter and minima in spring-summer. The same seasonal trend was also observed in 214Pb concentration values. 210Pb average yearly values were 0.70 and 0.82 mBq/m3 in 2000 and 2001, respectively, in good agreement with literature data registered at continental sites of similar latitude and longitude. The activity ratio 210Pb/214Pb was used to evaluate the residence time of fine aerosols in the urban air of Milan, which was 1-2 days.     

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.     

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.     

A study on natural radiation exposure in different realistic living rooms

In the first part of the paper, the factors affecting 222Rn properties in 25 different realistic living rooms (with low ventilation rates) of different houses in El-Minia City (Upper Egypt) have been studied; they included the activity concentration of 222Rn gas (C(o)), the unattached fraction (f(p)) of 218Po and 214Pb, the unattached potential alpha energy concentration (PAEC) and the equilibrium factor (F). The activity distributions of unattached 218Po and 214Pb as well as for the PAEC were determined. With a dosimetric model calculation [ICRP, 1994b. Human Respiratory Tract Model For Radiological Protection. Pergamon Press, Oxford. ICRP Publication 66] the total deposition fraction of unattached 218Po and 214Pb in human respiratory tract was evaluated to determine the total equivalent dose. An electrostatic precipitation method and a wire screen diffusion battery technique were both employed for the determination of 222Rn gas concentration and its unattached decay products, respectively. The mean activity concentration of 222Rn gas (C(o)) was found to be 110+/-20 Bq m(-3). The mean unattached activity concentrations of 218Po and 214Pb were found to be 0.6 and 0.35 Bq m(-3), respectively. A mean unattached fraction (f(p)) of 0.09+/-0.01 was obtained at a mean aerosol particle concentration (Z) of (2.9+/-0.23) x 10(3)cm(-3). The mean equilibrium factor (F) was determined to be 0.31+/-0.02. The mean PAEC of unattached 218Po and 214Pb was found to be 8.74+/-2.1 Bq m(-3). The activity distributions of 218Po and 214Pb show mean activity median diameters (AMD) of 1.5 and 1.85 nm with mean geometric standard deviations (SD) of 1.33 and 1.45, respectively. The mean activity distribution of the PAEC shows an AMD of 1.65 nm with a geometric standard deviation of 1.25. At a total deposition fraction of about 97% the total equivalent dose to the lung was determined to be about 133 microSv. The second part of this paper deals with a study of natural radionuclide contents of samples collected from the building materials of the rooms under investigations in part one. Analyses were performed in Marinelli beakers with a gamma multichannel analyzer equipped with a NaI(Tl) detector. The samples revealed the presence of the uranium-radium and thorium radioisotopes as well as 40K. Nine gamma-lines of the natural radioisotopes corresponding to 212Pb, 214Pb, 214Bi, 228Ac, 40K and 208Tl were detected and measured. The activity concentrations of 226Ra, 232Th and 40K were determined with mean activity concentrations of 58+/-19, 31+/-11 and 143+/-62 Bq kg(-1), respectively. These activities amount to a radium equivalent (Ra(eq)) of 113 Bq kg(-1) and to a mean value of external hazard index of 0.31.     

7Be to 210Pb concentration ratio in ground level air in Belgrade area

7Be to 210Pb concentration ratios in ground level air on two monitoring stations (MS1 and MS2) in Belgrade area were determined from 1996 to 2001. The average monthly concentrations of 7Be in ground level air were in the range of 0.6-18.3 mBq/m3 and exhibited one or two summer/early fall maxims and one minimum in winter. The maximum concentrations for 210Pb were generally observed in the fall, with the average concentrations in the range of 1.09 x 10(-4) to 30.9 x 10(-4) Bq/m3. The 7Be/210Pb ratios were in the range of 1.7-12.7 (MS1) and 1.8-11.3 (MS2), with summer maxims and late fall/winter minimums. The mean Radionuclides Loading Indices values approach zero except for 1996/1997 (MS1) and 2001 (MS2) due to higher concentrations of 7Be and 210Pb. The mean monthly concentrations of both radionuclides exhibited lognormal distributions. There is significant correlation between the 7Be/210Pb activities ratio and the air stability classes A + B + C for both monitoring stations (correlation coefficients 0.61-0.65), and no correlation with D class and E + F classes. Correlation was found between the activity of 7Be and air stability classes A + B + C (0.46-0.68), and E + F (0.38 for MS1), while for 210Pb, a moderate correlation (0.38-0.40) was found with the E + F air stability classes.     

Reinvestigation of airborne 210Pb, 137Cs and 207Bi in Vienna (Austria) after atmospheric nuclear weapons tests

Reconstruction of atmospheric 210Pb and 137Cs activity concentrations occurring in Vienna immediately after the atmospheric nuclear weapons tests shall answer the question, whether artificial 210Pb has been produced by fusion devices using lead materials. If so, 207Bi also can be expected. In 1962, weekly average values for 210Pb were between 0.08 +/- 0.02 and 1.31 +/- 0.30 mBq/m2, 137Cs amounts up to 5.1 +/- 0.6 mBq/m3. 207Bi remains below the detection limit, viz. < 0.5 mBq/m3. Bimonthly averages for the periods 1962-1964 and 1974-1975 show 137Cs activity concentrations with typical springtime maxima occurring together with low 210Pb values and 207Bi < 0.02 mBq/m3. Annual averages of 210Pb are varying between 0.27 and 0.53 mBq/m3, independent of whether atmospheric tests have been performed or not. Comparison of the activity ratios 207Bi/210Pb, 207Bi/137Cs and 210Pb/137Cs with published data, leads to the conclusion that no evidence exists for a significant production of 210Pb by nuclear explosions, neither after the Soviet tests in 1961-1962 nor after the Chinese tests in 1973-1976.     

Natural and anthropogenic radionuclides in airborne particulate samples collected in Barcelona (Spain)

Results for naturally occurring ⁷Be, ²¹⁰Pb, ⁴⁰K, ²¹⁴Bi, ²¹⁴Pb, ²¹²Pb, ²²⁸Ac and ²⁰⁸Tl and anthropogenic ¹³⁷Cs in airborne particulate matter in the Barcelona area during the period from January 2001 to December 2005 are presented and discussed. The ²¹²Pb and ²⁰⁸Tl, ²¹⁴Bi and ²¹⁴Pb, ⁷Be and ²¹⁰Pb radionuclide levels showed a significant correlation with each other, with correlation coefficients of 0.99, 0.78 and 0.69, respectively, suggesting similar origin/behaviour of these radionuclides in the air. Caessium-137 and Potassium-40 were transported to the air as resuspended particle from the soil. The ⁷Be and ²¹⁰Pb concentrations showed similar seasonal variations, with a tendency for maximum concentrations during the summer months. An inverse relationship was observed between the ⁷Be, ²¹⁰Pb, ⁴⁰K and ¹³⁷Cs concentrations and weekly rainfall, indicating washout of atmospheric aerosols carrying these radionuclides.     

The sources and fate of 210Po in the urban air: A review

The origin of ²¹⁰Po activity and its fluctuations in the air are discussed in this paper. In the case of atmospheric aerosol samples, a comparison of the ²¹⁰Po/²¹⁰Pb and ²¹⁰Bi/²¹⁰Pb activity ratios makes it possible not only to determine aerosol residence times but also to appraise the contribution of the unsupported ²¹⁰Po coming from other sources than ²²²Rn decay, such as human industrial activities, especially coal combustion. A simple mathematical method makes it possible to observe the seasonal fluctuations of the anthropogenic excess of ²¹⁰Po in the urban air. The average doses of ²¹⁰Po intake with food (including drinking water) and inhalation of urban aerosols are usually lower than those from ²¹⁰Po intake by cigarette smokers and negligible in comparison to total natural radiation exposure.     

Concentration levels of 210Pb and 210Po in dry tobacco leaves in Greece

Tobacco leaves are large and have sticky exudates that retain the radon decay products once they deposit on the leaves. The study of 210Po in tobacco is required, because of the cumulative alpha-radiation dose delivered to humans from inhaled 210Po in cigarette smoke. 210Pb is the other element of interest since it is the 210Po precursor in the radioactive decay chain. In the present study, the concentrations of these two radionuclides were determined in tobacco samples from seven regions in Greece. 210Po was determined by alpha spectrometry using a surface barrier detector after radiochemical separation and spontaneous deposition of polonium on a nickel disk. The 210Pb activity in the samples was determined via the 210Po resulting from the decay of 210Pb. The results of the present study indicate that 210Po concentrations ranged from 3.6 to 17.0 mBqg(-1) (average 13.1 mBqg(-1)) of dry tobacco, while 210Pb concentrations ranged from 7.3 to 18.0 mBqg(-1) (average 13.4 mBqg(-1)). The mean value of the annual committed effective dose for smokers (20 cigarettes per day) of Greek tobacco was estimated to be 287 microSv (124 microSv from 210Po and 163 microSv from 210Pb). The inhalation dose for smokers is on average about 12 times higher than for non-smokers living in the mid-latitudes of the northern hemisphere.     

Factors influencing ambient concentrations of (210)Pb and (7)Be over the city of Edinburgh (55.9 degrees N, 03.2 degrees W)

Concentrations of (210)Pb and (7)Be in air were continuously monitored, using a high-volume air sampler and a high-resolution gamma-ray spectrometer, during the period of July 2002 to June 2003 at the University of Edinburgh 55.9 degrees N, 03.2 degrees W. The time series of both radio-isotopes show seasonality, dependence on air-mass origin, residence time and precipitation. Surface air concentrations of (210)Pb and (7)Be ranged from 0.01 to 0.74 mBq m(-3) and 0.63-6.54 mBq m(-3), respectively. The measurements indicate that the average concentrations of both (210)Pb and (7)Be in surface air were 0.21+/-0.01 and 2.50+/-0.04 mBq m(-3), respectively; which agrees closely with the corresponding values reported for coastal air measurements in Europe.     

Variation of short-lived beta radionuclide (radon progeny) concentrations and the mixing processes in the atmospheric boundary layer

Radon is emitted to the atmosphere with quasi constant emission rates depending on the radium concentration in the earth's crust and soil physical properties. In this way, the ²²²Rn and ²²⁰Rn concentration in air reflects significantly the thickness of the atmospheric boundary layer (ABL). The aerosol-associated, beta-emitting progeny nuclides of ²²²Rn were measured daily in the framework of the atmospheric radioactivity monitoring program of NIMH at Sofia. The ²¹⁴Pb concentration was estimated from the measured short-lived beta activity of 24-h filter samples, changed daily at 6:00 GMT. The impact of some meteorological factors such as wind direction, wind velocity, humidity, and temperature on short-lived beta radionuclides is estimated, and the results show no simple statistical relationship. A seasonal pattern was observed with winter minima and late summer-early autumn maxima. High variability in daily morning concentrations and mean monthly values was observed. There were well pronounced differences between years. The height of the convective ABL was estimated from daily radio-soundings at 12:00 GMT for the period 2001-2006 and from seven soundings per day during the experimental campaign in Sofia in October 2003. In general, concentrations of short-lived ²²²Rn progeny nuclides decreased with increased convective ABL height.     

Comparative analysis of (239)Pu, (137)Cs, (210)Pb and (40)K spatial distributions in the top soil layer at the Baltic coast

This paper presents the results of an investigation into the spatial distribution of radionuclides of artificial ((239,240)Pu, (137)Cs) and natural ((210)Pb, (40)K) origins in the upper (0-5 cm) soil layers on the Baltic coastline of Lithuania ( approximately 5 km(2) area). The samples were analysed by gamma ray spectrometry and combined radiochemical procedures. The highest (210)Pb, (239,240)Pu and (137)Cs activity concentrations were determined in the forest samples, whereas (40)K activity was rather homogeneous across the study area. Relatively high (239,240)Pu and (40)K activity concentrations were determined along the surf zone. The (210)Pb and (137)Cs activity concentrations showed a gradual increase from the surf zone to the forest. The average activity concentrations of (239,240)Pu, (137)Cs, (210)Pb and (40)K in the beach and forest samples, respectively, were as follows: 0.32+/-0.08 and 0.74+/-0.14; 50+/-4 and 1190+/-50; 4.7+/-2.0 and 48+/-6; 186+/-15 and 216+/-17 Bq/kg.     

Inventories of fallout 210Pb and 137Cs radionuclides in moorland and woodland soils around Edinburgh urban area (UK)

Inventories of fallout (210)Pb and (137)Cs have been measured in moorland and woodland soils around the Edinburgh urban area, using a high purity germanium detector. The (210)Pb inventories in moorland soils were relatively uniform, with a mean value of 2520+/-270Bqm(-2). The mean (137)Cs inventory in moorland soils varied greatly from 1310 to 2100Bqm(-2), with a mean value of 1580+/-310Bqm(-2). The variability was ascribed mainly to the non-uniform distribution of fallout Chernobyl (137)Cs. The mean (210)Pb and (137)Cs inventories in woodland canopy soils were found to be 3630+/-380Bqm(-2) and 2510+/-510Bqm(-2), respectively. At sites for which both moorland and woodland data were available, the mean inventories provided fairly similar average enhancements of (47+/-7)% and (46+/-18)% of (210)Pb and (137)Cs under woodland canopy soils relative to open grassland soils, respectively. The enhancement factors are broadly in line with other independent findings in literature. Enhancement of both (210)Pb and (137)Cs in woodland soils relative to moorland soils is, in part, due to deposition by impaction during air turbulence, wash-off, gravitational settling and deposition during leaf senescence. Results of this study suggest that these processes affect both (210)Pb and (137)Cs carrier aerosols in a similar way.     

Surface air concentration and deposition of lead-210 in French Guiana: two years of continuous monitoring

To make up for the lack of data on (210)Pb aerosol deposition in tropical regions and to use this radionuclide as an aerosol tracer, a monitoring station was run for two years at Petit-Saut, French Guiana. Lead-210 concentration in air at ground level was monitored continuously together with atmospheric total deposition. The air concentration has a mean value of 0.23+/-0.02 mBq m(-3) during both wet and dry seasons, and it is only weakly affected by the precipitation mechanism. This result was unexpected in a wet tropical region, with a high precipitation rate. In contrast, deposition clearly correlates with precipitation for low/moderate rainfall (<15 cm per 15-day), while this correlation is masked by strong fluctuations at high rainfall. The estimated mean annual deposition over the last ten years is 163+/-75 Bq m(-2) y(-1). This provides a procedure for estimating this mean flux at other sites in French Guiana.     

Factors controlling 7Be and 210Pb atmospheric deposition as revealed by sampling individual rain events in the region of Geneva, Switzerland

Bulk atmospheric deposition of 7Be and 210Pb has been measured at Versoix, close to Geneva, Switzerland. Collectors were continuously deployed from November 1997 through November 1998 for periods from 1 to 22 days depending on the frequency of rain. The activities of 7Be and 210Pb integrated over the sampling interval were moderately well correlated with rainfall (r2 of 0.66 and 0.55, respectively; p < 0.001) and well correlated one with the other (r2 of 0.91; p < 0.001). The 7Be/210Pb activity ratio is close to 13.5, except for samples collected in the periods of very low precipitation which have a distinctly lower ratio. A simple model accounting for rainfall, seasonal variations and reload of the local atmosphere after a rain event explains 90% of the variance of 7Be and 210Pb deposition. Concentrations of 210Pb and Ca++ in rain were correlated with transport time of air masses over the continent as indicated by reconstruction of air mass trajectories over three days.     

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.     

Beryllium-7 in near-surface air and deposition at Brisbane, Australia

Measurements of 7Be concentrations in near-surface air and 7Be deposition were carried out at Brisbane, Australia. Concentrations of 7Be in near-surface air measured over 4 years show seasonal variations with values above the annual mean occurring mainly in the spring and summer months of each year. These higher concentrations coincide with the expected influx of stratospheric air to the planetary boundary layer in early spring and higher rates of convective circulation within the troposphere during summer. 7Be deposition measurements over 3 years show seasonal variations similar to the seasonal rainfall pattern. There is a statistically significant (p<0.001) linear relationship between monthly (7)Be deposition and rainfall amount. This relationship is used to calculate the net cumulative (7)Be areal activity density.     

Radon in the spas of Croatia

Radon concentrations in air and geothermal water of the spa pools in Croatia were measured and the average values of 40.3 and 4.5 kBq/m3 were obtained, respectively. Great difference between radon concentrations in pool and spring water was considered as a result of mixing normal and geothermal water in the pool as well as the radon decay. Estimation of an effective dose, received by the personnel in the Bizovac spa, gave the value of 0.27 mSv/y. At the location Stubica, the transfer factor of the radon for air and thermal water in the pool was calculated, and the value of 4.9+/-0.7 x 10(-3) was obtained.     

Evaluation of 210Pb and 210Po in cigarette tobacco produced in Brazil

Cigarette smoking is one of the pathways that might contribute significantly to the increase in the radiation dose reaching man, due to the relatively large concentrations of 210Pb and 210Po found in tobacco leaves. In the present study, the concentrations of these two radionuclides were determined in eight of the most frequently sold cigarette brands produced in Brazil. 210Pb was determined by counting the beta activity of 210Bi with a gas flow proportional detector after radiochemical separation and precipitation of PbCrO4. 210Po was determined by alpha spectrometry using a surface barrier detector after radiochemical separation and spontaneous deposition of Po on a copper disk. The results showed concentrations ranging from 11.9 to 30.2 mBq per gram of dry tobacco for 210Pb and from 10.9 to 27.4 mBq per gram of dry tobacco for 210Po. The collective committed effective dose resulting from the use of cigarettes produced in Brazil per year is estimated to be 1.5 x 10(4) man-Sv.     

(90)Sr, (210)Po and (210)Pb in lichen and reindeer in Norway

Concentrations of (90)Sr, (210)Po and (210)Pb in lichen and reindeer were studied in central (?stre Namdal) and southern Norway (V?g?) during 2000-2003. The study focussed on potential differences in concentrations of these nuclides in reindeer of different ages. Concentrations of (90)Sr in bones of approximately 10 year old adult females were about 40% higher than those in calves' antlers ((90)Sr concentrations in antlers and bones of calves are similar), while the available data from V?g? suggest that (90)Sr concentrations in reindeer calves decreased with an effective ecological half-time of 9.03+/-0.06 years during 1988-2002. Furthermore, (90)Sr concentrations were 50-80% higher in bone of reindeer of a similar age from V?g? compared to those from ?stre Namdal. Concentrations of (210)Po and (210)Pb in muscle and liver tissues were comparable to those reported for reindeer in other Nordic areas, with no significant difference in (210)Po and (210)Pb concentrations between adults and calves or between reindeer from the two different study areas.