TY  - CONF
AU  - Bianchi, Stefano
AU  - Plastino, Wolfango
AU  - Rajačić, Milica
AU  - Krneta Nikolić, Jelena
AU  - Todorović, Dragana
AU  - Zorko, Benjamin
AU  - Nečemer, Marijan
AU  - Vodenik, Branko
AU  - Glavič Cindro, Denis
AU  - Kožar Logar, Jasmina
AU  - Sarvan, Darko
AU  - Đurđević, Vladimir
AU  - Ajtić, Jelena
PY  - 2022
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/2479
AB  - Beryllium-7 is a natural radionuclide used as a tracer of the stratospheric-tropospheric exchange. Its abundance in the surface air is expected to change as the temperatures in the atmosphere increase.
To investigate the temporal trends of the beryllium-7 activity concentrations and temperature, we apply spectral analysis to time series from three sampling sites: Belgrade in Serbia, and Ljubljana and Krško in Slovenia. The sites lie close to the 45 ºN parallel, with Krško approximately 400 km and Ljubljana around 500 km west of Belgrade. Between January 1991 and December 2019, the air filter samples were collected using air samplers; a monthly composite sample was formed and analysed by gamma spectrometry. We use monthly mean temperature records from the European Climate Assessment & Dataset, the Republic Hydrometeorological Service of Serbia for Belgrade, and the Slovenian Environment Agency for the sites in Slovenia.
In the spectral analysis decomposition, we look into a term called trend that represents the overall growth (increase or decrease) in the data records. The trend is calculated using a linear fit. All three sites show 1) positive temperature trends, however statistically insignificant (at the 95 % confidence level), and 2) statistically significant beryllium-7 activity concentration trends of 2.26 %/year, 1.13 %/year, and 0.50 %/year in Belgrade, Ljubljana, and Krško, respectively.
The results confirm our initial hypothesis–over the 28 investigated years, the beryllium-7 activity concentrations increase in the surface air. On the other hand, the non-significant temperature rise in our records suggests that within our method, the temporal resolution of one month is insufficient for obtaining a statistically significant temperature trend.
PB  - Niš : Sievert Association
C3  - International conference on radiation applications (RAP 2022)
T1  - Beryllium-7 activity concentration trends in Serbia and Slovenia
SP  - 45
UR  - https://hdl.handle.net/21.15107/rcub_veterinar_2479
ER  - 

@conference{
author = "Bianchi, Stefano and Plastino, Wolfango and Rajačić, Milica and Krneta Nikolić, Jelena and Todorović, Dragana and Zorko, Benjamin and Nečemer, Marijan and Vodenik, Branko and Glavič Cindro, Denis and Kožar Logar, Jasmina and Sarvan, Darko and Đurđević, Vladimir and Ajtić, Jelena",
year = "2022",
abstract = "Beryllium-7 is a natural radionuclide used as a tracer of the stratospheric-tropospheric exchange. Its abundance in the surface air is expected to change as the temperatures in the atmosphere increase.
To investigate the temporal trends of the beryllium-7 activity concentrations and temperature, we apply spectral analysis to time series from three sampling sites: Belgrade in Serbia, and Ljubljana and Krško in Slovenia. The sites lie close to the 45 ºN parallel, with Krško approximately 400 km and Ljubljana around 500 km west of Belgrade. Between January 1991 and December 2019, the air filter samples were collected using air samplers; a monthly composite sample was formed and analysed by gamma spectrometry. We use monthly mean temperature records from the European Climate Assessment & Dataset, the Republic Hydrometeorological Service of Serbia for Belgrade, and the Slovenian Environment Agency for the sites in Slovenia.
In the spectral analysis decomposition, we look into a term called trend that represents the overall growth (increase or decrease) in the data records. The trend is calculated using a linear fit. All three sites show 1) positive temperature trends, however statistically insignificant (at the 95 % confidence level), and 2) statistically significant beryllium-7 activity concentration trends of 2.26 %/year, 1.13 %/year, and 0.50 %/year in Belgrade, Ljubljana, and Krško, respectively.
The results confirm our initial hypothesis–over the 28 investigated years, the beryllium-7 activity concentrations increase in the surface air. On the other hand, the non-significant temperature rise in our records suggests that within our method, the temporal resolution of one month is insufficient for obtaining a statistically significant temperature trend.",
publisher = "Niš : Sievert Association",
journal = "International conference on radiation applications (RAP 2022)",
title = "Beryllium-7 activity concentration trends in Serbia and Slovenia",
pages = "45",
url = "https://hdl.handle.net/21.15107/rcub_veterinar_2479"
}

Bianchi, S., Plastino, W., Rajačić, M., Krneta Nikolić, J., Todorović, D., Zorko, B., Nečemer, M., Vodenik, B., Glavič Cindro, D., Kožar Logar, J., Sarvan, D., Đurđević, V.,& Ajtić, J.. (2022). Beryllium-7 activity concentration trends in Serbia and Slovenia. in International conference on radiation applications (RAP 2022)
Niš : Sievert Association., 45.
https://hdl.handle.net/21.15107/rcub_veterinar_2479

Bianchi S, Plastino W, Rajačić M, Krneta Nikolić J, Todorović D, Zorko B, Nečemer M, Vodenik B, Glavič Cindro D, Kožar Logar J, Sarvan D, Đurđević V, Ajtić J. Beryllium-7 activity concentration trends in Serbia and Slovenia. in International conference on radiation applications (RAP 2022). 2022;:45.
https://hdl.handle.net/21.15107/rcub_veterinar_2479 .

Bianchi, Stefano, Plastino, Wolfango, Rajačić, Milica, Krneta Nikolić, Jelena, Todorović, Dragana, Zorko, Benjamin, Nečemer, Marijan, Vodenik, Branko, Glavič Cindro, Denis, Kožar Logar, Jasmina, Sarvan, Darko, Đurđević, Vladimir, Ajtić, Jelena, "Beryllium-7 activity concentration trends in Serbia and Slovenia" in International conference on radiation applications (RAP 2022) (2022):45,
https://hdl.handle.net/21.15107/rcub_veterinar_2479 .

TY  - JOUR
AU  - Bianchi, Stefano
AU  - Plastino, Wolfango
AU  - Brattich, Erika
AU  - Đurđević, Vladimir
AU  - Longo, Alessandro
AU  - Hernandez-Ceballos, Miguel A.
AU  - Sarvan, Darko
AU  - Ajtić, Jelena
PY  - 2019
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1745
AB  - The activity concentrations of beryllium-7, a natural radiotracer that is considered as a tracer of the strato-spheric-tropospheric exchange, shows a distinct behaviour in Northern Europe compared to the central and southern parts of the continent. In this study, we use the measurements collected at four sampling stations in Scandinavia (Ivalo, Umea, Kista, Risoe) between 2001 and 2010 and investigate their trends, periodicities and residuals with the aim to further understand the common features in the beryllium-7 data records in northern sampling sites. The beryllium-7 activity concentrations exhibit statistically significant positive trends that range from an average value of 1.50%/year to an average value of 2.96%/year. We detect a one-year periodicity in all the sites, and in the southernmost site, Risoe in Denmark, additional higher-frequency harmonics. In the residual time series, we find outliers that represent occurrences of extremely high beryllium-7 activity concentration. Cross-correlations of the beryllium-7 residuals across the four sites decrease with increasing distance; similarly, as indicated by local Hurst exponents the records exhibit long-range correlations that weaken towards the end of the investigated period. To investigate the causes of the detected trends, we also calculate correlations between beryllium-7 and factors related to its production, transport and removal from the atmosphere: in particular, cross-correlations of the beryllium-7 residuals with residuals in sunspot number, local temperature, atmospheric pressure and precipitation, as well as Arctic Oscillation index and North Atlantic Oscillation index. Most of the obtained correlations, however, are not statistically significant, highlighting the need to analyse a longer time period in order to evaluate the impact of different factors on the airborne beryllium-7 activity concentration.
PB  - Pergamon-Elsevier Science Ltd, Oxford
T2  - Applied Radiation and Isotopes
T1  - Analysis of trends, periodicities, and correlations in the beryllium-7 time series in Northern Europe
VL  - 148
SP  - 160
EP  - 167
DO  - 10.1016/j.apradiso.2019.03.038
ER  - 

@article{
author = "Bianchi, Stefano and Plastino, Wolfango and Brattich, Erika and Đurđević, Vladimir and Longo, Alessandro and Hernandez-Ceballos, Miguel A. and Sarvan, Darko and Ajtić, Jelena",
year = "2019",
abstract = "The activity concentrations of beryllium-7, a natural radiotracer that is considered as a tracer of the strato-spheric-tropospheric exchange, shows a distinct behaviour in Northern Europe compared to the central and southern parts of the continent. In this study, we use the measurements collected at four sampling stations in Scandinavia (Ivalo, Umea, Kista, Risoe) between 2001 and 2010 and investigate their trends, periodicities and residuals with the aim to further understand the common features in the beryllium-7 data records in northern sampling sites. The beryllium-7 activity concentrations exhibit statistically significant positive trends that range from an average value of 1.50%/year to an average value of 2.96%/year. We detect a one-year periodicity in all the sites, and in the southernmost site, Risoe in Denmark, additional higher-frequency harmonics. In the residual time series, we find outliers that represent occurrences of extremely high beryllium-7 activity concentration. Cross-correlations of the beryllium-7 residuals across the four sites decrease with increasing distance; similarly, as indicated by local Hurst exponents the records exhibit long-range correlations that weaken towards the end of the investigated period. To investigate the causes of the detected trends, we also calculate correlations between beryllium-7 and factors related to its production, transport and removal from the atmosphere: in particular, cross-correlations of the beryllium-7 residuals with residuals in sunspot number, local temperature, atmospheric pressure and precipitation, as well as Arctic Oscillation index and North Atlantic Oscillation index. Most of the obtained correlations, however, are not statistically significant, highlighting the need to analyse a longer time period in order to evaluate the impact of different factors on the airborne beryllium-7 activity concentration.",
publisher = "Pergamon-Elsevier Science Ltd, Oxford",
journal = "Applied Radiation and Isotopes",
title = "Analysis of trends, periodicities, and correlations in the beryllium-7 time series in Northern Europe",
volume = "148",
pages = "160-167",
doi = "10.1016/j.apradiso.2019.03.038"
}

Bianchi, S., Plastino, W., Brattich, E., Đurđević, V., Longo, A., Hernandez-Ceballos, M. A., Sarvan, D.,& Ajtić, J.. (2019). Analysis of trends, periodicities, and correlations in the beryllium-7 time series in Northern Europe. in Applied Radiation and Isotopes
Pergamon-Elsevier Science Ltd, Oxford., 148, 160-167.
https://doi.org/10.1016/j.apradiso.2019.03.038

Bianchi S, Plastino W, Brattich E, Đurđević V, Longo A, Hernandez-Ceballos MA, Sarvan D, Ajtić J. Analysis of trends, periodicities, and correlations in the beryllium-7 time series in Northern Europe. in Applied Radiation and Isotopes. 2019;148:160-167.
doi:10.1016/j.apradiso.2019.03.038 .

Bianchi, Stefano, Plastino, Wolfango, Brattich, Erika, Đurđević, Vladimir, Longo, Alessandro, Hernandez-Ceballos, Miguel A., Sarvan, Darko, Ajtić, Jelena, "Analysis of trends, periodicities, and correlations in the beryllium-7 time series in Northern Europe" in Applied Radiation and Isotopes, 148 (2019):160-167,
https://doi.org/10.1016/j.apradiso.2019.03.038 . .

TY  - CONF
AU  - Ajtić, Jelena
AU  - Sarvan, Darko
AU  - Todorović, Dragana
AU  - Rajačić, Milica
AU  - Krneta-Nikolić, Jelena D.
AU  - Đurđević, Vladimir
AU  - Zorko, Benjamin
AU  - Vodenik, Branko
AU  - Glavič-Cindro, Denis
AU  - Kožar Logar, Jasmina
PY  - 2017
AB  - Međusobna povezanost specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnomsloju atmosfere sa meteorološkim parametrima razmotrena je u faktorskoj analizi.Merenja su sprovedena u Beogradu, Republika Srbija, i u Ljubljani i Krškom, uRepublici Sloveniji, tokom 1991–2015 godine. Na sve tri lokacije, faktorska opterećenjadva faktora pokazuju da je: 1) specifična aktivnost berilijuma-7 obuhvaćena faktorom 1sa temperaturom, oblačnošću i relativnom vlažnošću; dok je 2) specifična aktivnostolova-210 obuhvaćena faktorom 2 sa količinom padavina i atmosferskim pritiskom.Iako je komunalitet već dva faktora veći od 0,5 za većinu posmatranih varijabli, tekuvođenjem trećeg faktora komunalitet za specifičnu aktivnost olova-210 i atmosferskogpritiska na sve tri merne lokacije raste na preko 0,5. Rezultati faktorske analizepokazuju da se specifične aktivnosti berilijuma-7 i olova-210 u prizmenom slojuatmosfere nalaze pod različitim dominantnim uticajima. Koncentracija berilijuma-7 jepod uticajem faktora regionalnog karaktera, koji je takođe dominantan za srednjutemperaturu. Ova veza specifične aktivnosti berilijuma-7 i temperature preko dominantnog zajedničkog faktora važi i kada se broj faktora u analizi poveća na tri i četiri.Sa druge strane, na koncentraciju olova-210, kao i na količinu padavina i atmosferskipritisak, više uticaja ima lokalni faktor. Ova povezanost olova-210 sa druga dvameteorološka parametra, međutim, prestaje da važi sa povećanjem broja faktora uanalizi na tri, kada se izdvaja specifičan faktor koji objašnjava preko 80% varijansespecifične aktivnosti olova-210.
AB  - An association between the beryllium-7 and lead-210 specific activities in surface airand meteorological parameters is investigated using factor analysis. The measurementswere conducted in Belgrade, Republic of Serbia, and Ljubljana and Krško, Republic ofSlovenia, over 1991–2015. In all the locations, the factor loadings of two factors showthat: 1) the beryllium-7 specific activity is encompassed by factor 1 together withtemperature, cloud cover and relative humidity; while 2) the lead-210 specific activity,precipitation and atmospheric pressure are described by factor 2. Although thecommunalities of only two factors are already larger than 0.5 for most of the variables,an introduction of a third factor raises the communalities of all the variables above 0.5.The results imply that the beryllium-7 and lead-210 are under different dominantunderlying mechanisms. The concentration of beryllium-7 seems to be primarilyinfluenced by a mechanism of a regional character which is also a predominant factorfor temperature. This association between the beryllium-7 specific activity andtemperature prevails even when the number of factors in the analysis is raised to threeand four. The lead-210 specific activity, on the other hand, together with precipitationand atmospheric pressure, is under an influence of a local mechanism, but thatrelationship between the variables ceases to hold when the number of factors is raisedto three, and more than 80% of the variance in the Pb-210 specific activity is explainedby one specific factor.
PB  - Beograd : Institut za nuklearne nauke "Vinča"
PB  - Društvo za zaštitu od zračenja Srbije i Crne Gore
C3  - Zbornik radova sa XXIX Simpozijuma Društva za zaštitu od zračenja Srbije i Crne Gore, 27–29. septembar, 2017, str. Srebrno jezero, Srbija
T1  - Faktorska analiza specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnom sloju vazduha, i meteoroloških parametara
T1  - Factor analysis of the beryllium-7 and lead-210 specific activities in surface air, and meteorological parameters
SP  - 19
EP  - 27
UR  - https://hdl.handle.net/21.15107/rcub_veterinar_2375
ER  - 

@conference{
author = "Ajtić, Jelena and Sarvan, Darko and Todorović, Dragana and Rajačić, Milica and Krneta-Nikolić, Jelena D. and Đurđević, Vladimir and Zorko, Benjamin and Vodenik, Branko and Glavič-Cindro, Denis and Kožar Logar, Jasmina",
year = "2017",
abstract = "Međusobna povezanost specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnomsloju atmosfere sa meteorološkim parametrima razmotrena je u faktorskoj analizi.Merenja su sprovedena u Beogradu, Republika Srbija, i u Ljubljani i Krškom, uRepublici Sloveniji, tokom 1991–2015 godine. Na sve tri lokacije, faktorska opterećenjadva faktora pokazuju da je: 1) specifična aktivnost berilijuma-7 obuhvaćena faktorom 1sa temperaturom, oblačnošću i relativnom vlažnošću; dok je 2) specifična aktivnostolova-210 obuhvaćena faktorom 2 sa količinom padavina i atmosferskim pritiskom.Iako je komunalitet već dva faktora veći od 0,5 za većinu posmatranih varijabli, tekuvođenjem trećeg faktora komunalitet za specifičnu aktivnost olova-210 i atmosferskogpritiska na sve tri merne lokacije raste na preko 0,5. Rezultati faktorske analizepokazuju da se specifične aktivnosti berilijuma-7 i olova-210 u prizmenom slojuatmosfere nalaze pod različitim dominantnim uticajima. Koncentracija berilijuma-7 jepod uticajem faktora regionalnog karaktera, koji je takođe dominantan za srednjutemperaturu. Ova veza specifične aktivnosti berilijuma-7 i temperature preko dominantnog zajedničkog faktora važi i kada se broj faktora u analizi poveća na tri i četiri.Sa druge strane, na koncentraciju olova-210, kao i na količinu padavina i atmosferskipritisak, više uticaja ima lokalni faktor. Ova povezanost olova-210 sa druga dvameteorološka parametra, međutim, prestaje da važi sa povećanjem broja faktora uanalizi na tri, kada se izdvaja specifičan faktor koji objašnjava preko 80% varijansespecifične aktivnosti olova-210., An association between the beryllium-7 and lead-210 specific activities in surface airand meteorological parameters is investigated using factor analysis. The measurementswere conducted in Belgrade, Republic of Serbia, and Ljubljana and Krško, Republic ofSlovenia, over 1991–2015. In all the locations, the factor loadings of two factors showthat: 1) the beryllium-7 specific activity is encompassed by factor 1 together withtemperature, cloud cover and relative humidity; while 2) the lead-210 specific activity,precipitation and atmospheric pressure are described by factor 2. Although thecommunalities of only two factors are already larger than 0.5 for most of the variables,an introduction of a third factor raises the communalities of all the variables above 0.5.The results imply that the beryllium-7 and lead-210 are under different dominantunderlying mechanisms. The concentration of beryllium-7 seems to be primarilyinfluenced by a mechanism of a regional character which is also a predominant factorfor temperature. This association between the beryllium-7 specific activity andtemperature prevails even when the number of factors in the analysis is raised to threeand four. The lead-210 specific activity, on the other hand, together with precipitationand atmospheric pressure, is under an influence of a local mechanism, but thatrelationship between the variables ceases to hold when the number of factors is raisedto three, and more than 80% of the variance in the Pb-210 specific activity is explainedby one specific factor.",
publisher = "Beograd : Institut za nuklearne nauke "Vinča", Društvo za zaštitu od zračenja Srbije i Crne Gore",
journal = "Zbornik radova sa XXIX Simpozijuma Društva za zaštitu od zračenja Srbije i Crne Gore, 27–29. septembar, 2017, str. Srebrno jezero, Srbija",
title = "Faktorska analiza specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnom sloju vazduha, i meteoroloških parametara, Factor analysis of the beryllium-7 and lead-210 specific activities in surface air, and meteorological parameters",
pages = "19-27",
url = "https://hdl.handle.net/21.15107/rcub_veterinar_2375"
}

Ajtić, J., Sarvan, D., Todorović, D., Rajačić, M., Krneta-Nikolić, J. D., Đurđević, V., Zorko, B., Vodenik, B., Glavič-Cindro, D.,& Kožar Logar, J.. (2017). Faktorska analiza specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnom sloju vazduha, i meteoroloških parametara. in Zbornik radova sa XXIX Simpozijuma Društva za zaštitu od zračenja Srbije i Crne Gore, 27–29. septembar, 2017, str. Srebrno jezero, Srbija
Beograd : Institut za nuklearne nauke "Vinča"., 19-27.
https://hdl.handle.net/21.15107/rcub_veterinar_2375

Ajtić J, Sarvan D, Todorović D, Rajačić M, Krneta-Nikolić JD, Đurđević V, Zorko B, Vodenik B, Glavič-Cindro D, Kožar Logar J. Faktorska analiza specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnom sloju vazduha, i meteoroloških parametara. in Zbornik radova sa XXIX Simpozijuma Društva za zaštitu od zračenja Srbije i Crne Gore, 27–29. septembar, 2017, str. Srebrno jezero, Srbija. 2017;:19-27.
https://hdl.handle.net/21.15107/rcub_veterinar_2375 .

Ajtić, Jelena, Sarvan, Darko, Todorović, Dragana, Rajačić, Milica, Krneta-Nikolić, Jelena D., Đurđević, Vladimir, Zorko, Benjamin, Vodenik, Branko, Glavič-Cindro, Denis, Kožar Logar, Jasmina, "Faktorska analiza specifičnih aktivnosti berilijuma-7 i olova-210 u prizemnom sloju vazduha, i meteoroloških parametara" in Zbornik radova sa XXIX Simpozijuma Društva za zaštitu od zračenja Srbije i Crne Gore, 27–29. septembar, 2017, str. Srebrno jezero, Srbija (2017):19-27,
https://hdl.handle.net/21.15107/rcub_veterinar_2375 .

TY  - CONF
AU  - Ajtić, Jelena
AU  - Đurđević, Vladimir
AU  - Sarvan, Darko
AU  - Brattich, Erika
AU  - Hernandez-Ceballos, Miguel A.
PY  - 2016
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1335
AB  - This analysis presents linear correlations of beryllium-7 specific activity in surface air with several variables measured in Helsinki, Finland, over 1987-2011. Measurements of beryllium-7 are linearly correlated with the following 10 variables: tropopause height; mean, minimum and maximum temperature; precipitation; atmospheric pressure; potential vorticity at 300 hPa and 200 hPa; solar zenith angle; and the number of sunspots. A time lag is also introduced into the calculations of Pearsons linear correlation coefficients, i.e. the beryllium-7 specific activity measured on a day is correlated with a value of a given variable measured on some preceding day. In particular, the time lag is allowed to vary between 0 and 7 days for tropopause height, meteorological parameters and potential vorticity, and between 0 and 31 days for solar zenith angle and number of sunspots. In this way, we obtain sets of correlation coefficients for each pair of the analysed variables, in which we look for the maximum correlation coefficient as well as for the time lag on which this value is reached. In addition to investigating all of the available measurements, the time series are further split into seasonal subsets. Weak to moderate maximum correlation coefficients, ranging between 0.29 and 0.44, are found for the beryllium-7 specific activity with the tropopause height, temperatures and atmospheric pressure. These correlations are reached with a time lag of 0-2 days. Seasonal correlation coefficients show that the strongest linear relationships are obtained in summer. Similarly, a moderate correlation (0.48) with the solar zenith angle is reached with a time lag of 0 days, but the seasonal correlation coefficients in this case show a weaker relationship during different seasons. On the other hand, our analysis suggests that the correlations of beryllium-7 with precipitation, potential vorticity and the number of sunspots are not statistically significant.
PB  - RAD Association
C3  - Fourth International Conference on Radiation and Applications in Various Fields of Research
T1  - Beryllium-7 specific activity in surface air and its correlation with meteorological variables, solar zenith angle, and number of sunspots
SP  - 79
EP  - 83
DO  - 10.21175/RadProc.2016.19
ER  - 

@conference{
author = "Ajtić, Jelena and Đurđević, Vladimir and Sarvan, Darko and Brattich, Erika and Hernandez-Ceballos, Miguel A.",
year = "2016",
abstract = "This analysis presents linear correlations of beryllium-7 specific activity in surface air with several variables measured in Helsinki, Finland, over 1987-2011. Measurements of beryllium-7 are linearly correlated with the following 10 variables: tropopause height; mean, minimum and maximum temperature; precipitation; atmospheric pressure; potential vorticity at 300 hPa and 200 hPa; solar zenith angle; and the number of sunspots. A time lag is also introduced into the calculations of Pearsons linear correlation coefficients, i.e. the beryllium-7 specific activity measured on a day is correlated with a value of a given variable measured on some preceding day. In particular, the time lag is allowed to vary between 0 and 7 days for tropopause height, meteorological parameters and potential vorticity, and between 0 and 31 days for solar zenith angle and number of sunspots. In this way, we obtain sets of correlation coefficients for each pair of the analysed variables, in which we look for the maximum correlation coefficient as well as for the time lag on which this value is reached. In addition to investigating all of the available measurements, the time series are further split into seasonal subsets. Weak to moderate maximum correlation coefficients, ranging between 0.29 and 0.44, are found for the beryllium-7 specific activity with the tropopause height, temperatures and atmospheric pressure. These correlations are reached with a time lag of 0-2 days. Seasonal correlation coefficients show that the strongest linear relationships are obtained in summer. Similarly, a moderate correlation (0.48) with the solar zenith angle is reached with a time lag of 0 days, but the seasonal correlation coefficients in this case show a weaker relationship during different seasons. On the other hand, our analysis suggests that the correlations of beryllium-7 with precipitation, potential vorticity and the number of sunspots are not statistically significant.",
publisher = "RAD Association",
journal = "Fourth International Conference on Radiation and Applications in Various Fields of Research",
title = "Beryllium-7 specific activity in surface air and its correlation with meteorological variables, solar zenith angle, and number of sunspots",
pages = "79-83",
doi = "10.21175/RadProc.2016.19"
}

Ajtić, J., Đurđević, V., Sarvan, D., Brattich, E.,& Hernandez-Ceballos, M. A.. (2016). Beryllium-7 specific activity in surface air and its correlation with meteorological variables, solar zenith angle, and number of sunspots. in Fourth International Conference on Radiation and Applications in Various Fields of Research
RAD Association., 79-83.
https://doi.org/10.21175/RadProc.2016.19

Ajtić J, Đurđević V, Sarvan D, Brattich E, Hernandez-Ceballos MA. Beryllium-7 specific activity in surface air and its correlation with meteorological variables, solar zenith angle, and number of sunspots. in Fourth International Conference on Radiation and Applications in Various Fields of Research. 2016;:79-83.
doi:10.21175/RadProc.2016.19 .

Ajtić, Jelena, Đurđević, Vladimir, Sarvan, Darko, Brattich, Erika, Hernandez-Ceballos, Miguel A., "Beryllium-7 specific activity in surface air and its correlation with meteorological variables, solar zenith angle, and number of sunspots" in Fourth International Conference on Radiation and Applications in Various Fields of Research (2016):79-83,
https://doi.org/10.21175/RadProc.2016.19 . .

TY  - JOUR
AU  - Hernández-Ceballos, Miguel A.
AU  - Brattich, Erika
AU  - Cinelli, Giorgia
AU  - Ajtić, Jelena
AU  - Đurđević, Vladimir
PY  - 2016
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1406
AB  - This study aims at analysing the latitudinal variability of both the yearly and seasonal pattern of Be-7 surface activity concentrations, at addressing the impact of tropopause height (TPH) on Be-7 distribution and at evaluating the time lag between TPH and Be-7 at European level. With this aim, weekly Be-7 and daily TPH data at 17 sampling stations during 10 yr (2001-2010) are analysed. Be-7 shows a clear increasing tendency in the period and generally tends to increase with decreasing latitude. The seasonal pattern generally shows maxima during the warm period and minima during the cold one. The seasonal variogram analysis points out a good spatial correlation for TPH data while a weaker one is observed for Be-7, having TPH a larger influence on Be-7 during summer. The influence of TPH on Be-7 exhibits a large spatial variability, with a clear gap between south and north in the area of the polar front jet. The results identify the presence of two main groups, in particular separating between stations located in northern Europe (50 degrees N and higher) and stations in southern Europe (south of 50 degrees N). A similar behaviour for stations located in the same geographical area is also observed when looking at the day of maximum impact of TPH on Be-7 concentrations. The results suggest that Be-7 concentrations respond in different time ranges to changes in the TPH, observing seasonal differences in each group. These results represent the first European approach to the understanding of the TPH impact on Be-7 concentrations at surface levels.
PB  - Taylor & Francis Ltd, Abingdon
T2  - Tellus Series B-Chemical and Physical Meteorology
T1  - Seasonality of 7 Be concentrations in Europe and influence of tropopause height
VL  - 68
SP  - 29534
DO  - 10.3402/tellusb.v68.29534
ER  - 

@article{
author = "Hernández-Ceballos, Miguel A. and Brattich, Erika and Cinelli, Giorgia and Ajtić, Jelena and Đurđević, Vladimir",
year = "2016",
abstract = "This study aims at analysing the latitudinal variability of both the yearly and seasonal pattern of Be-7 surface activity concentrations, at addressing the impact of tropopause height (TPH) on Be-7 distribution and at evaluating the time lag between TPH and Be-7 at European level. With this aim, weekly Be-7 and daily TPH data at 17 sampling stations during 10 yr (2001-2010) are analysed. Be-7 shows a clear increasing tendency in the period and generally tends to increase with decreasing latitude. The seasonal pattern generally shows maxima during the warm period and minima during the cold one. The seasonal variogram analysis points out a good spatial correlation for TPH data while a weaker one is observed for Be-7, having TPH a larger influence on Be-7 during summer. The influence of TPH on Be-7 exhibits a large spatial variability, with a clear gap between south and north in the area of the polar front jet. The results identify the presence of two main groups, in particular separating between stations located in northern Europe (50 degrees N and higher) and stations in southern Europe (south of 50 degrees N). A similar behaviour for stations located in the same geographical area is also observed when looking at the day of maximum impact of TPH on Be-7 concentrations. The results suggest that Be-7 concentrations respond in different time ranges to changes in the TPH, observing seasonal differences in each group. These results represent the first European approach to the understanding of the TPH impact on Be-7 concentrations at surface levels.",
publisher = "Taylor & Francis Ltd, Abingdon",
journal = "Tellus Series B-Chemical and Physical Meteorology",
title = "Seasonality of 7 Be concentrations in Europe and influence of tropopause height",
volume = "68",
pages = "29534",
doi = "10.3402/tellusb.v68.29534"
}

Hernández-Ceballos, M. A., Brattich, E., Cinelli, G., Ajtić, J.,& Đurđević, V.. (2016). Seasonality of 7 Be concentrations in Europe and influence of tropopause height. in Tellus Series B-Chemical and Physical Meteorology
Taylor & Francis Ltd, Abingdon., 68, 29534.
https://doi.org/10.3402/tellusb.v68.29534

Hernández-Ceballos MA, Brattich E, Cinelli G, Ajtić J, Đurđević V. Seasonality of 7 Be concentrations in Europe and influence of tropopause height. in Tellus Series B-Chemical and Physical Meteorology. 2016;68:29534.
doi:10.3402/tellusb.v68.29534 .

Hernández-Ceballos, Miguel A., Brattich, Erika, Cinelli, Giorgia, Ajtić, Jelena, Đurđević, Vladimir, "Seasonality of 7 Be concentrations in Europe and influence of tropopause height" in Tellus Series B-Chemical and Physical Meteorology, 68 (2016):29534,
https://doi.org/10.3402/tellusb.v68.29534 . .

TY  - CONF
AU  - Ajtić, Jelena
AU  - Maletić, Dimitrije
AU  - Stratimirović, Đorđe
AU  - Blesić, Suzana
AU  - Nikolić, Jelena
AU  - Đurđević, Vladimir S.
AU  - Todorović, Dragana
PY  - 2015
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1286
AB  - 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.
PB  - RAD Association
C3  - Rad 2015: The Third International Conference on Radiation and Applications in Various Fields of Rese
T1  - Predictability of lead-210 in surface air based on multivariate analysis
SP  - 317
EP  - 322
UR  - https://hdl.handle.net/21.15107/rcub_veterinar_1286
ER  - 

@conference{
author = "Ajtić, Jelena and Maletić, Dimitrije and Stratimirović, Đorđe and Blesić, Suzana and Nikolić, Jelena and Đurđević, Vladimir S. and Todorović, Dragana",
year = "2015",
abstract = "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.",
publisher = "RAD Association",
journal = "Rad 2015: The Third International Conference on Radiation and Applications in Various Fields of Rese",
title = "Predictability of lead-210 in surface air based on multivariate analysis",
pages = "317-322",
url = "https://hdl.handle.net/21.15107/rcub_veterinar_1286"
}

Ajtić, J., Maletić, D., Stratimirović, Đ., Blesić, S., Nikolić, J., Đurđević, V. S.,& Todorović, D.. (2015). Predictability of lead-210 in surface air based on multivariate analysis. in Rad 2015: The Third International Conference on Radiation and Applications in Various Fields of Rese
RAD Association., 317-322.
https://hdl.handle.net/21.15107/rcub_veterinar_1286

Ajtić J, Maletić D, Stratimirović Đ, Blesić S, Nikolić J, Đurđević VS, Todorović D. Predictability of lead-210 in surface air based on multivariate analysis. in Rad 2015: The Third International Conference on Radiation and Applications in Various Fields of Rese. 2015;:317-322.
https://hdl.handle.net/21.15107/rcub_veterinar_1286 .

Ajtić, Jelena, Maletić, Dimitrije, Stratimirović, Đorđe, Blesić, Suzana, Nikolić, Jelena, Đurđević, Vladimir S., Todorović, Dragana, "Predictability of lead-210 in surface air based on multivariate analysis" in Rad 2015: The Third International Conference on Radiation and Applications in Various Fields of Rese (2015):317-322,
https://hdl.handle.net/21.15107/rcub_veterinar_1286 .

TY  - JOUR
AU  - Ajtić, Jelena
AU  - Todorović, Dragana
AU  - Nikolić, Jelena D.
AU  - Đurđević, Vladimir S.
PY  - 2013
UR  - https://vet-erinar.vet.bg.ac.rs/handle/123456789/1079
AB  - Activities of 7Be and 210Pb 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 7Be activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter, while the 210Pb activity exhibits two maxima, in autumn and late winter. The mean monthly concentrations measured at both sites are below 9 mBq/m3 and 1.3 mBq/m3 for 7Be and 210Pb, respectively. The obtained correlation of the 7Be 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 7Be activity with temperature and sunshine hours, and the 210Pb activity with atmospheric pressure. The maximum 7Be and 210Pb 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.
AB  - Aktivnosti 7Be i 210Pb merene su tokom 2004-2012, u prizemnom sloju atmosfere na dve lokacije u Beogradu. Mesečne specifične aktivnosti određene su standardnom metodom spektrometrije gama zračenja na HPGe detektorima. Aktivnosti radionuklida pokazuju sezonski karakter: 7Be ima maksimum tokom proleća i leta, a minimum zimi, dok 210Pb ima dva maksimuma, tokom jeseni i kasne zime. Na obe lokacije, srednje mesečne aktivnosti 7Be su manje od 9 mBq/m3, dok su za 210Pb manje od 1.3 mBq/m3. Između aktivnosti 7Be i broja sunčevih pega nije nađena statistički značajna korelacija. Relacije između aktivnosti ovih radionuklida i klimatskih parametara (količina padavina, temperatura, relativna vlažnost, oblačnost, broj sunčanih sati i atmosferski pritisak) takođe su ispitane, ali su značajne korelacije dobijene samo za aktivnost 7Be sa temperaturom i brojem sunčanih sati, odnosno za aktivnost 210Pb sa atmosferskim pritiskom. Na osnovu veze između maksimalne aktivnosti po intervalima količine padavina, mogu se razlikovati tri režima spiranja radionuklida iz atmosfere. Tokom sušnih perioda, akumulacija radionuklida u atmosferi uzrokuje njihovu povišenu aktivnost, ali korelacija između aktivnosti i broja uzastopnih suvih dana nije dobijena.
PB  - Univerzitet u Beogradu - Institut za nuklearne nauke Vinča, Beograd
T2  - Nuclear Technology and Radiation Protection
T1  - A multi-year study of radioactivity in surface air and its relation to climate variables in Belgrade, Serbia
T1  - Višegodišnja studija radioaktivnosti u prizemnom sloju atmosfere u relaciji sa klimatskim parametrima u Beogradu, Srbija
VL  - 28
IS  - 4
SP  - 381
EP  - 388
DO  - 10.2298/NTRP1304381A
ER  - 

@article{
author = "Ajtić, Jelena and Todorović, Dragana and Nikolić, Jelena D. and Đurđević, Vladimir S.",
year = "2013",
abstract = "Activities of 7Be and 210Pb 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 7Be activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter, while the 210Pb activity exhibits two maxima, in autumn and late winter. The mean monthly concentrations measured at both sites are below 9 mBq/m3 and 1.3 mBq/m3 for 7Be and 210Pb, respectively. The obtained correlation of the 7Be 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 7Be activity with temperature and sunshine hours, and the 210Pb activity with atmospheric pressure. The maximum 7Be and 210Pb 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., Aktivnosti 7Be i 210Pb merene su tokom 2004-2012, u prizemnom sloju atmosfere na dve lokacije u Beogradu. Mesečne specifične aktivnosti određene su standardnom metodom spektrometrije gama zračenja na HPGe detektorima. Aktivnosti radionuklida pokazuju sezonski karakter: 7Be ima maksimum tokom proleća i leta, a minimum zimi, dok 210Pb ima dva maksimuma, tokom jeseni i kasne zime. Na obe lokacije, srednje mesečne aktivnosti 7Be su manje od 9 mBq/m3, dok su za 210Pb manje od 1.3 mBq/m3. Između aktivnosti 7Be i broja sunčevih pega nije nađena statistički značajna korelacija. Relacije između aktivnosti ovih radionuklida i klimatskih parametara (količina padavina, temperatura, relativna vlažnost, oblačnost, broj sunčanih sati i atmosferski pritisak) takođe su ispitane, ali su značajne korelacije dobijene samo za aktivnost 7Be sa temperaturom i brojem sunčanih sati, odnosno za aktivnost 210Pb sa atmosferskim pritiskom. Na osnovu veze između maksimalne aktivnosti po intervalima količine padavina, mogu se razlikovati tri režima spiranja radionuklida iz atmosfere. Tokom sušnih perioda, akumulacija radionuklida u atmosferi uzrokuje njihovu povišenu aktivnost, ali korelacija između aktivnosti i broja uzastopnih suvih dana nije dobijena.",
publisher = "Univerzitet u Beogradu - Institut za nuklearne nauke Vinča, Beograd",
journal = "Nuclear Technology and Radiation Protection",
title = "A multi-year study of radioactivity in surface air and its relation to climate variables in Belgrade, Serbia, Višegodišnja studija radioaktivnosti u prizemnom sloju atmosfere u relaciji sa klimatskim parametrima u Beogradu, Srbija",
volume = "28",
number = "4",
pages = "381-388",
doi = "10.2298/NTRP1304381A"
}

Ajtić, J., Todorović, D., Nikolić, J. D.,& Đurđević, V. S.. (2013). A multi-year study of radioactivity in surface air and its relation to climate variables in Belgrade, Serbia. in Nuclear Technology and Radiation Protection
Univerzitet u Beogradu - Institut za nuklearne nauke Vinča, Beograd., 28(4), 381-388.
https://doi.org/10.2298/NTRP1304381A

Ajtić J, Todorović D, Nikolić JD, Đurđević VS. A multi-year study of radioactivity in surface air and its relation to climate variables in Belgrade, Serbia. in Nuclear Technology and Radiation Protection. 2013;28(4):381-388.
doi:10.2298/NTRP1304381A .

Ajtić, Jelena, Todorović, Dragana, Nikolić, Jelena D., Đurđević, Vladimir S., "A multi-year study of radioactivity in surface air and its relation to climate variables in Belgrade, Serbia" in Nuclear Technology and Radiation Protection, 28, no. 4 (2013):381-388,
https://doi.org/10.2298/NTRP1304381A . .