Predictability of Lead-210 in Surface Air Based on Multivariate Analysis

Dependence of the lead-210 activity concentration in surface air on meteorological variables and teleconnection indices is investigated using multivariate analysis, which gives the Boosted Decision Trees method as the most suitable for variable analysis. A mapped functional behaviour of the lead-210 activity concentration is further obtained, and used to test predictability of lead-210 in surface air. The results show an agreement between the predicted and measured values. The temporal evolution of the measured activities is satisfactorily matched by the prediction. The largest qualitative differences are obtained for winter months.3rd International Conference on Radiation and Applications in Various Fields of Research (RAD), Jun 08-12, 2015, Budva, Montenegr

Ground Level Air Beryllium-7 and Ozone in Belgrade

Three sets of data covering the 2004-2007 period are examined: two beryllium-7 series and ozone measured in ground level air. The measuring sites are at three different locations in Belgrade, Serbia. The temporal evolution of beryllium-7 and ozone is presented, as well as their mutual correlations. Beryllium-7 data for Belgrade agree well with the results for other locations in the region. The correlation between two beryllium-7 data sets is 0.57. The results for ozone indicate that Belgrade is not a common continental site, as the maximum in ozone distribution is reached in springtime. The overall correlation between beryllium-7 and ozone is good, but varies over different seasons. A large correlation (0.67) is noted between beryllium-7 measured at the site in Vinca, Serbia, and the monthly maximum ozone in autumn. An analysis which assumes the transport of air masses from the stratosphere, along which the only process changing the air mass composition is radioactive decay of beryllium-7, does not conclusively confirm the high correlation between beryllium-7 and ozone in autumn

Predictability of Lead-210 in Surface Air Based on Multivariate Analysis

Dependence of the lead-210 activity concentration in surface air on meteorological variables and teleconnection indices is investigated using multivariate analysis, which gives the Boosted Decision Trees method as the most suitable for variable analysis. A mapped functional behaviour of the lead-210 activity concentration is further obtained, and used to test predictability of lead-210 in surface air. The results show an agreement between the predicted and measured values. The temporal evolution of the measured activities is satisfactorily matched by the prediction. The largest qualitative differences are obtained for winter months.3rd International Conference on Radiation and Applications in Various Fields of Research (RAD), Jun 08-12, 2015, Budva, Montenegr

A Multi-Year Study of Radioactivity in Surface Air and Its Relation to Climate Variables in Belgrade, Serbia

Activities of Be-7 and Pb-210 were monitored in surface air in Belgrade, Serbia, from 2004 to 2012. The measurements were taken from two locations, in an open field of a city suburb and in the central city area. The activities were determined on HPGe detectors by standard gamma spectrometry. The Be-7 activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter, while the Pb-210 activity exhibits two maxima, in autumn and late winter. The mean monthly concentrations measured at both sites are below 9 mBq/m(3) and 1.3 mBq/m(3) for Be-7 and Pb-210, respectively. The obtained correlation of the Be-7 activity with the number of sun-spots is not statistically significant. Relations of the radionuclides activities with climate variables (precipitation, temperature, relative humidity, cloud cover, sunshine hours, and atmospheric pressure) are also investigated, but the only significant correlations are found for the Be-7 activity with temperature and sunshine hours, and the Pb-210 activity with atmospheric pressure. The maximum Be-7 and Pb-210 activities corresponding to binned total monthly precipitation data imply different modes of the radionuclide scavenging from the atmosphere. During dry periods, accumulation of the radionuclides in the atmosphere leads to their increased activities, but no correlation was found between the activities and the number of consecutive dry days

Dilution of the Antarctic ozone hole into Southern midlatitudes.

Reduction in ozone levels in southern midlatitudes, caused by the transport of ozone-depleted air from the Antarctic polar vortex, is examined. The problem is approached from two different, but complementary, directions. First, a case study examining an atypical vertical profile of ozone in December 1998, caused by the presence of vortex air is presented. Second, the overall dilution effect in spring- and summer time in the years 1998, 1999, and 2000 is quantified. In the first approach, an ozonesonde profile over the Network for Detection of Stratospheric Change (NDSC) site at Lauder (45.0° S, 169.7° E), New Zealand, for 24 December 1998 showing atypically low ozone centred around 24 km altitude (600 K potential temperature), is analyzed. The origin of the anomaly is explained using reverse domain filling (RDF) calculations combined with a PV/O3 fitting technique applied to ozone measurements from the Polar Ozone and Aerosol Measurement (POAM) III instrument. The RDF calculations for two isentropic surfaces, 550 K and 600 K, show that ozone-poor air from the Antarctic polar vortex reached New Zealand on 24-26 December 1998. The vortex air on the 550 K isentrope originated in the ozone hole region, unlike the air on 600 K, where low ozone values were the result of dynamical effects. High-resolution ozone maps are generated, and their examination shows that the vortex remnant situated above New Zealand was the cause of the altered ozone profile on 24 December. The maps also illustrate mixing of the vortex filaments into southern midlatitudes, whereby the overall midlatitude ozone levels are decreased. In the second approach, to quantify the full impact of the dilution of the Antarctic ozone hole into southern midlatitudes in spring and summer of the years 1998, 1999 and 2000, diabatic RDF calculations are performed for parcels between 30° S and 60° S, initialized on a 1° longitude by 1° latitude grid, on seven potential temperature surfaces, between 400 K and 700 K. In each year, the trajectories are run back to 10 October, at which time the ozone depletion processes in the Antarctic vortex have largely ceased. Two distinct regions in the vortex, the core and the edge region, are taken into account. The reduction in ozone due to the presence of vortex parcels in southern midlatitudes is calculated in the layer between 375 K and 725 K, thus encompassing the stratospheric region where most of ozone depletion occurs and where ozone is most abundant. The calculations are performed under the assumption that the volume mixing ratio of depleted ozone (the difference between undepleted ozone and observed ozone) does not change along the trajectories. To mitigate non-conservation of mass arising from the employment of Lagrangian model, a scaling method is introduced. The results for the years 1998-2000 show that on average, between 15 October and 15 January of the following year, 17-19% of the midlatitude air parcels originate inside the Antarctic vortex. The corresponding reduction in ozone is 15-18 DU. The reduction caused by the presence of the air parcels originating in the vortex edge region is significant, especially in the early part of the period under examination. The results for four subregions in midlatitudes (spanning longitude regions of 90º, starting from 0º) are also presented, and they indicate that, on average, in the region encompassing New Zealand and Australia ozone reduction is less than in other subregions in the months of October and November, but from mid-December to mid-January the reduction is effectively the same in all subregions. Furthermore, tests to examine the sensitivity of the results to uncertainties in the wind fields, and to the choice of the initial day, are performed for the year 1998. The results indicate that the method is more sensitive to the initial conditions, including the size of the vortex and the amount of filamentation, than to introduced perturbations in the winds. The corresponding uncertainties in the midlatitude ozone reduction are 38% and 5%, respectively. The uncertainties are generally larger for subregions, and range from 37-65%, and 4-14%, respectively. The calculated ozone reduction is compared to the Total Ozone Mapping Spectrometer (TOMS) measurements of ozone column to derive relative changes in the total ozone. The results show that without the dilution effect, ozone levels in southern midlatitudes would be 4-6% higher during spring- and summertime. Moreover, a comparison of the calculated ozone reduction with ozone levels in 1979 demonstrates that on average, approximately 50-60% of the change can be attributed to the dilution effect. These results present a lower limit of the impact, as dilution in the lowermost stratosphere and troposphere is not captured in the calculations presented here

Active biomonitoring of air radioactivity in urban areas

To assess the validity of the moss bag monitoring technique in the radioactivity control of ground level urban air, a study on radionuclide contents in moss was performed in the city of Belgrade, Serbia. From May 2006 to May 2007, moss (Sphagnum girgensohni, Dubna, Russia) was exposed to the aero pollution in a location in the central area of the city. The activity of K-40, Pb-210, and Cs-137 was measured on an HPGe detector (Canberra, relative efficiency 23%) by standard gamma spectrometry. The activities 245 +/- 25 Bq/kg for K-40, 315 +/- 34 Bq/kg for Pb-210, and 28 +/- 4 Bq/kg for Cs-137 are in the range of values reported for the region; the differences are due to the moss species, local climate and measuring technique. Taking into consideration the time of the exposure and appropriate calibration procedure, moss bag biomonitoring could be used as a complementary method for determination of radionuclides in urban air

Radioactivity Monitoring in Ground Level Air in Belgrade Urban Area

Concentrations of beryllium-7 (Be-7), lead-210 (Pb-210) and caesium-137 (Cs-137) were measured at two sites in the city of Belgrade (Serbia). One monitoring site was located in the central city area with heavy traffic and the other within the Institute of Nuclear Sciences Vinca, in the suburbs. Presented data cover the period 2004-9. Activity of the radionuclides was determined on an HPGe detector (Canberra, relative efficiency 23%) by standard gamma spectrometry. Activities of Be-7 and Pb-210 exhibit a similar seasonal pattern. The mean monthly concentrations of Be-7 did not exceed 7 mBq m(-3). The maxima are correlated with the seasonal increase in temperature, whereas the minima are linearly correlated with the amount of precipitation. The activity of Pb-210 was below 0.9 mBq m(-3). The activities of both radionuclides were very low in winters and were largely affected by precipitation and snow coverage. Concentrations of Cs-137 were mainly below the limit of detection

Leaves of higher plants as biomonitors of radionuclides (Cs-137, K-40, Pb-210 and Be-7) in urban air

Leaves of linden (Tilia tomentosa L. and Tilia cordata Mill.) and horse chestnut (Aesculus hippocastanum L.) were analysed as biomonitors of radionuclides in urban air. Samples of soils, leaves and aerosols were collected in Belgrade, Serbia. Activities of Cs-137, K-40, Pb-210 and Be-7 in the samples were measured on an HPGe detector by standard gamma spectrometry. Soil-to-leaves transfer factors were calculated. Students t test and linear Pearson correlation coefficients were used for statistical analysis. Differences in local conditions at the sampling sites were not significant, and the mechanisms of the radionuclides accumulation in both plant species are similar. Ceasium-137 was detected in some of the leaf samples only. Transfer factors for Cs-137 and K-40 were (0.03-0.08) and 1.3, respectively. The concentrations of Pb-210 and Be-7 in leaves were higher in autumn than in spring, and there were some similarities in their seasonal patterns in leaves and in air. Weak to medium correlation was obtained for the Pb-210 and Be-7 activities in leaves and aerosols. Large positive correlation was obtained for the Pb-210 activities in linden leaves and the mean activity in aerosols for the preceding months. Different primary modes of radionuclides accumulation in leaves were observed. Since large positive correlation was obtained for the Pb-210 activity in linden leaves and the mean in aerosols for the preceding months, mature linden leaves could be used as biomonitors of recent Pb-210 activity in air

Factors affecting the 7Be surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter

Relationships between the beryllium-7 concentrations in surface air and meteorological parameters (temperature, atmospheric pressure, and precipitation), teleconnection indices (Arctic Oscillation, North Atlantic Oscillation, and Scandinavian pattern) and number of sunspots are investigated using two multivariate statistical techniques: hierarchical cluster and factor analysis. The beryllium-7 surface measurements over 1995-2011, at four sampling sites located in the Scandinavian Peninsula, are obtained from the Radioactivity Environmental Monitoring Database. In all sites, the statistical analyses show that the beryllium-7 concentrations are strongly linked to temperature. Although the beryllium-7 surface concentration exhibits the well-characterised spring/summer maximum, our study shows that extremely high beryllium-7 concentrations, defined as the values exceeding the 90th percentile in the data records for each site, also occur over the October-March period. Two types of autumn/winter extremes are distinguished: type-1 when the number of extremes in a given month is less than three, and type-2 when at least three extremes occur in a month. Factor analysis performed for these autumn/winter events shows a weaker effect of temperature and a stronger impact of the transport and production signal on the beryllium-7 concentrations. Further, the majority of the type-2 extremes are associated with a very high monthly Scandinavian teleconnection index. The type-2 extremes that occurred in January, February and March are also linked to sudden stratospheric warmings of the Arctic vortex. Our results indicate that the Scandinavian teleconnection index might be a good indicator of the meteorological conditions facilitating extremely high beryllium-7 surface concentrations over Scandinavia during autumn and winter.JRC.G.10-Knowledge for Nuclear Security and Safet

Factors affecting the 7Be surface concentration and its extremely high occurrences over the Scandinavian Peninsula during autumn and winter

Relationships between the beryllium-7 concentrations in surface air and meteorological parameters (temperature, atmospheric pressure, and precipitation), teleconnection indices (Arctic Oscillation, North Atlantic Oscillation, and Scandinavian pattern) and number of sunspots are investigated using two multivariate statistical techniques: hierarchical cluster and factor analysis. The beryllium-7 surface measurements over 1995-2011, at four sampling sites located in the Scandinavian Peninsula, are obtained from the Radioactivity Environmental Monitoring Database. In all sites, the statistical analyses show that the beryllium-7 concentrations are strongly linked to temperature. Although the beryllium-7 surface concentration exhibits the well-characterised spring/summer maximum, our study shows that extremely high beryllium-7 concentrations, defined as the values exceeding the 90th percentile in the data records for each site, also occur over the October-March period. Two types of autumn/winter extremes are distinguished: type-1 when the number of extremes in a given month is less than three, and type-2 when at least three extremes occur in a month. Factor analysis performed for these autumn/winter events shows a weaker effect of temperature and a stronger impact of the transport and production signal on the beryllium-7 concentrations. Further, the majority of the type-2 extremes are associated with a very high monthly Scandinavian teleconnection index. The type-2 extremes that occurred in January, February and March are also linked to sudden stratospheric warmings of the Arctic vortex. Our results indicate that the Scandinavian teleconnection index might be a good indicator of the meteorological conditions facilitating extremely high beryllium-7 surface concentrations over Scandinavia during autumn and winter.JRC.G.10-Knowledge for Nuclear Security and Safet