Journal of Environmental Radioactivity 138 (2014) 341e342
Contents lists available at ScienceDirect
Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad
Editorial
Special issue of Journal of Environmental Radioactivity on 2nd International Conference on Po and radioactive Pb isotopes
1. Introduction Daughter products of radon isotopes (222Rn, 220Rn and 219Rn) originating from the 238Ue235Ue232Th decay chains have been widely utilized as tracers and chronometers in our understanding of the earth and near-earth surface processes. Of the 33 Pb isotopes (182214Pb) that occur in nature and that are produced inside the laboratory, only 4 are stable (204Pb, 206Pb, 207Pb and 208Pb). Of these 29 radioactive Pb isotopes, four radioactive isotopes are produced from the 238U (214Pb, T1/2 ¼ 26.8 min; 210Pb, T1/2 ¼ 22.3 yr), 235U (211Pb, T1/2 ¼ 36.1 min) and 232Th series (212Pb, T1/2 ¼ 10.64 h) (Porcelli and Baskaran, 2011). Due to low abundance and relatively short half-life, 211Pb is of less importance as a tracer. There are 27 Po isotopes (192218Po) all of which are radioactive that occur in nature or produced inside the laboratory and the longest-lived radionuclide that occur in nature is 210Po (T1/2 ¼ 138.38 d). Six of these 27 radioactive isotopes are produced from the 238U (218Po, T1/ 214 Po, T1/2 ¼ 164 ms; 210Po, T1/2 ¼ 138.38 d), 235U 2 ¼ 3.10 min; 215 ( Po, T1/2 ¼ 1.78 ms) and 232Th series (216Po, T1/2 ¼ 0.145 s; 212 Po, T1/2 ¼ 0.299 ms) (Porcelli and Baskaran, 2011). When chemically inert isotopes of radon gas are produced in the upper earth's crust from the decay of UeTh series, a fraction of it diffuse out of the crust and is transported by turbulence and advection through the atmosphere. When these isotopes undergo radioactive decay, heavy metal atoms (including 212Pb, 214Pb and 210Pb) are produced which rapidly become attached to natural aerosols and eventually return to earth through atmospheric scavenging processes. The journey of radon and its daughter products including 210Po and 210Pb through the atmosphere, hydrosphere and biosphere has been a major area of research over the past 40e50 years and this 2nd International Conference on Po and radioactive Pb isotopes is another major step in moving this frontier of research forward. Polonium is an OeS Group VI element, and is readily assimilated into biological organisms and can be used in conjunction with 210Pb to trace the biogenic and terrigenous particulate matter. The 210 Po:210Pb pair is utilized to quantify vertical and horizontal scavenging at ocean margins and at key interfaces such as benthic nepheloid layer. Polonium-210 radiation dose is reported to contribute the maximum amount to humans via intake of food, especially that originating from marine environments (Aarkrog et al., 1997). Since 210Po emits 5.3 MeV alpha particle, it presents a considerably greater biological danger than that of 210Pb which is a beta emitter. It has been estimated that the equivalent dose resulting from a single disintegration of 210Po are about thousand http://dx.doi.org/10.1016/j.jenvrad.2014.08.004 0265-931X/© 2014 Published by Elsevier Ltd.
times greater than in the case of 210Pb decay (Parfenov, 1974). The studies on the volatility and speciation of Po have drawn considerable attention during the past 15 years. The volatile nature of Po also results in extraneous sources of Po to the atmosphere in addition to the production from the decay of atmospheric 210Pb. In many NORM industries, the volatile 210Po is an important radioactive source in terms occupational dose. Better understanding of the kinetics of Po and Pb are important in terms of their mobility in human body and the environment. The biological half-life of Po and Pb in human body needs further investigation and accordingly different groups in various institutions across the world are actively working on this field. Of the daughter-products of 238U-series, the most-extensively studied and utilized isotope as a chronometer is 210Pb. Lead-210 serves as a chronometer to investigate the environmental changes that have taken place in the Anthropocene. A variety of matrices have been dated using the disequilibrium between 210 Pb and its long-lived parent, 226Ra, that include: marine, lacustrine and riverine sediments, biogenic and abiogenic carbonates, ice cores, etc. It is also used to date some archaeological objects (e.g., paintings). An advanced search in Scopus (http://www. scopus.com) with the key words “sediment” and “210Pb” produced 2464 results with 85% peer-reviewed articles (checked on 30th June 2014). With a view to disseminating the information acquired and expanding the knowledge base, the first topical conference on Po and radioactive Pb isotopes was held in Seville, Spain during 26e28 October 2009 at the Centro Nacional de Aceleradores (CNA). Prof. Rafael Garcia-Tenorio and Prof. Elic Holm were mainly responsible for organising this conference. The conference was attended by 138 registered participants from 38 different countries reflecting the world wide interest in Po and radioactive Pb. Although the conference in Spain was organised as an one time event, considering the importance of the subject the scientific community was looking forward for the second conference in this series and there was an overwhelming feeling that this conference should be held periodically once in every 2e3 years. 2. The conference The 2nd International Conference on Po and radioactive Pb isotopes was organized by the Radioecology and Environmental Radioactivity Laboratory of Mangalore University, Mangalore, India during Feb. 10e13, 2013. The conference was attended by 108 registered participants from 21 different countries, which again
342
Editorial / Journal of Environmental Radioactivity 138 (2014) 341e342
underlined the worldwide interest in the subject. The Conference was organized in sessions covering the following topics: ❖ Radiochemistry, instrumentation and quality assurance ❖ Movement of 210Pb and 210Po in terrestrial environment and the kinetics of 210Pb and 210Po ❖ 210Pb and 210Po as tracers in the marine environment ❖ 210Pb and 210Po as chronometer in marine, lacustrine, and cyrosphere environment ❖ 210Pb as chronometer in carbonate studies ❖ The 210Pb and 210Po as tracers in the atmosphere ❖ 210Pb as a tracer in terrestrial environments ❖ 210Pb and 210Po in NORM Industries ❖ 210Pb and 210Po in dose assessments ❖ New techniques for the measurements of Po and Pb radioisotopes In addition to plenary and invited talks, there were oral and poster sessions of the contributed papers covering all the above topics. The discussions which followed the presentations and a special session for discussion on the last day were lively and showed this field of research continues to be of much interest. As in the case of first conference in this series, Journal of Environmental Radioactivity (JER), Elsevier came forward to publish selected papers presented in the 2nd international conference. Papers were selected from different sessions in order to cover the scope of the conference. The selection was very difficult due to the many good papers and the limited number that can be published in this issue. This special issue contains selected articles on diurnal variations of 218Po, 214Pb, and 214Po and their effect on atmospheric electrical conductivity in the lower atmosphere, 210 Po/210Pb ratios in the atmosphere, estimation of Kd of 210Po and 210Pb, enrichment and particle size dependence of 210Po in coal ash, lifetimes of 214Po and 212Po, 210Pb as a tracer of soil erosion studies, problems associated with 210Pb dating of sediments, 210Po and 210Pb as tracers in a riverine and coastal waters, mobility of 210 Po and 210Pb in acid mine discharge, etc. Most of these papers were handled by two guest editors, Profs. Karunakara Naregundi and Mark Baskaran. The 3rd conference in this series is being organized by Institute of Nuclear Sciences, Ege University during October 11e14, 2015 in Kusadasi, Turkey. We look forward for a larger participation of scientists in the conference.
Acknowledgement The guest editors wish to thank Dr. Steve Sheppard, Editor-inChief, Journal of Environmental Radioactivity, and Elsevier Science Ltd. for making this Special Issue possible. Thanks are also extended to all of the external reviewers who contributed their valuable time and expertise in providing constructive criticism. Thanks are due to funding agencies of Govt. of India: The Board of Research in Nuclear Sciences (BRNS) (No. 2012/17/34/323/214/ BRNS/3092 dated 28 March 2013), Department of Science and Technology, Ministry of Science and Technology (SERB/F/4914/2012-13 dated 04/12/2012), Ministry of Earth Sciences (SERB/F/4914/2012-13 dated 04/12/ 2012), University Grants Commission, Atomic Energy Regulatory Board (AERB) (AERB/ITSD/CSRP-2/2013/593 dated Feb. 12, 2013) for funding the conference. We are grateful to the Mangalore University for the financial support, extending conference hall and all logistical support for the conference. We again thank all the speakers, participants and the members of the various committees for the success of this conference. References Aarkrog, A., Baxter, M., Bologa, S., Bettencourt, A.O., Bojanowski, R., Charmasson, A.S., Cunha, P.I., 1997. A comparison of doses from 137Cs and 210 Po in marine food: a major international study. J. Environ. Radioact. 34, 69e90. Parfenov, Y.D., 1974. Po-210 in the environment and in the human organism. Atom. Energy Rev. 12, 75e143. Porcelli, D., Baskaran, M., 2011. An overview of isotope geochemistry in environmental studies. In: Baskaran, M. (Ed.), Handbook of Environmental Isotope Geochemistry. Springer, Heidelberg, Dordrecht, London, New York, ISBN 9783-642-10636-1, pp. 11e32 (Printed in 2 volumes) e-ISBN 978-3-642-10637-8.
N. Karunakara, Guest Editor* Radioecology and Environmental Radioactivity Research Laboratory, Mangalore University, Mangalagangothri 574199, India Mark Baskaran, Guest Editor Wayne State University, Detroit, MI, USA E-mail address: [email protected]. * Corresponding author. E-mail address: [email protected] (N. Karunakara).
Available online 3 September 2014
Contents lists available at ScienceDirect
Journal of Environmental Radioactivity journal homepage: www.elsevier.com/locate/jenvrad
Editorial
Special issue of Journal of Environmental Radioactivity on 2nd International Conference on Po and radioactive Pb isotopes
1. Introduction Daughter products of radon isotopes (222Rn, 220Rn and 219Rn) originating from the 238Ue235Ue232Th decay chains have been widely utilized as tracers and chronometers in our understanding of the earth and near-earth surface processes. Of the 33 Pb isotopes (182214Pb) that occur in nature and that are produced inside the laboratory, only 4 are stable (204Pb, 206Pb, 207Pb and 208Pb). Of these 29 radioactive Pb isotopes, four radioactive isotopes are produced from the 238U (214Pb, T1/2 ¼ 26.8 min; 210Pb, T1/2 ¼ 22.3 yr), 235U (211Pb, T1/2 ¼ 36.1 min) and 232Th series (212Pb, T1/2 ¼ 10.64 h) (Porcelli and Baskaran, 2011). Due to low abundance and relatively short half-life, 211Pb is of less importance as a tracer. There are 27 Po isotopes (192218Po) all of which are radioactive that occur in nature or produced inside the laboratory and the longest-lived radionuclide that occur in nature is 210Po (T1/2 ¼ 138.38 d). Six of these 27 radioactive isotopes are produced from the 238U (218Po, T1/ 214 Po, T1/2 ¼ 164 ms; 210Po, T1/2 ¼ 138.38 d), 235U 2 ¼ 3.10 min; 215 ( Po, T1/2 ¼ 1.78 ms) and 232Th series (216Po, T1/2 ¼ 0.145 s; 212 Po, T1/2 ¼ 0.299 ms) (Porcelli and Baskaran, 2011). When chemically inert isotopes of radon gas are produced in the upper earth's crust from the decay of UeTh series, a fraction of it diffuse out of the crust and is transported by turbulence and advection through the atmosphere. When these isotopes undergo radioactive decay, heavy metal atoms (including 212Pb, 214Pb and 210Pb) are produced which rapidly become attached to natural aerosols and eventually return to earth through atmospheric scavenging processes. The journey of radon and its daughter products including 210Po and 210Pb through the atmosphere, hydrosphere and biosphere has been a major area of research over the past 40e50 years and this 2nd International Conference on Po and radioactive Pb isotopes is another major step in moving this frontier of research forward. Polonium is an OeS Group VI element, and is readily assimilated into biological organisms and can be used in conjunction with 210Pb to trace the biogenic and terrigenous particulate matter. The 210 Po:210Pb pair is utilized to quantify vertical and horizontal scavenging at ocean margins and at key interfaces such as benthic nepheloid layer. Polonium-210 radiation dose is reported to contribute the maximum amount to humans via intake of food, especially that originating from marine environments (Aarkrog et al., 1997). Since 210Po emits 5.3 MeV alpha particle, it presents a considerably greater biological danger than that of 210Pb which is a beta emitter. It has been estimated that the equivalent dose resulting from a single disintegration of 210Po are about thousand http://dx.doi.org/10.1016/j.jenvrad.2014.08.004 0265-931X/© 2014 Published by Elsevier Ltd.
times greater than in the case of 210Pb decay (Parfenov, 1974). The studies on the volatility and speciation of Po have drawn considerable attention during the past 15 years. The volatile nature of Po also results in extraneous sources of Po to the atmosphere in addition to the production from the decay of atmospheric 210Pb. In many NORM industries, the volatile 210Po is an important radioactive source in terms occupational dose. Better understanding of the kinetics of Po and Pb are important in terms of their mobility in human body and the environment. The biological half-life of Po and Pb in human body needs further investigation and accordingly different groups in various institutions across the world are actively working on this field. Of the daughter-products of 238U-series, the most-extensively studied and utilized isotope as a chronometer is 210Pb. Lead-210 serves as a chronometer to investigate the environmental changes that have taken place in the Anthropocene. A variety of matrices have been dated using the disequilibrium between 210 Pb and its long-lived parent, 226Ra, that include: marine, lacustrine and riverine sediments, biogenic and abiogenic carbonates, ice cores, etc. It is also used to date some archaeological objects (e.g., paintings). An advanced search in Scopus (http://www. scopus.com) with the key words “sediment” and “210Pb” produced 2464 results with 85% peer-reviewed articles (checked on 30th June 2014). With a view to disseminating the information acquired and expanding the knowledge base, the first topical conference on Po and radioactive Pb isotopes was held in Seville, Spain during 26e28 October 2009 at the Centro Nacional de Aceleradores (CNA). Prof. Rafael Garcia-Tenorio and Prof. Elic Holm were mainly responsible for organising this conference. The conference was attended by 138 registered participants from 38 different countries reflecting the world wide interest in Po and radioactive Pb. Although the conference in Spain was organised as an one time event, considering the importance of the subject the scientific community was looking forward for the second conference in this series and there was an overwhelming feeling that this conference should be held periodically once in every 2e3 years. 2. The conference The 2nd International Conference on Po and radioactive Pb isotopes was organized by the Radioecology and Environmental Radioactivity Laboratory of Mangalore University, Mangalore, India during Feb. 10e13, 2013. The conference was attended by 108 registered participants from 21 different countries, which again
342
Editorial / Journal of Environmental Radioactivity 138 (2014) 341e342
underlined the worldwide interest in the subject. The Conference was organized in sessions covering the following topics: ❖ Radiochemistry, instrumentation and quality assurance ❖ Movement of 210Pb and 210Po in terrestrial environment and the kinetics of 210Pb and 210Po ❖ 210Pb and 210Po as tracers in the marine environment ❖ 210Pb and 210Po as chronometer in marine, lacustrine, and cyrosphere environment ❖ 210Pb as chronometer in carbonate studies ❖ The 210Pb and 210Po as tracers in the atmosphere ❖ 210Pb as a tracer in terrestrial environments ❖ 210Pb and 210Po in NORM Industries ❖ 210Pb and 210Po in dose assessments ❖ New techniques for the measurements of Po and Pb radioisotopes In addition to plenary and invited talks, there were oral and poster sessions of the contributed papers covering all the above topics. The discussions which followed the presentations and a special session for discussion on the last day were lively and showed this field of research continues to be of much interest. As in the case of first conference in this series, Journal of Environmental Radioactivity (JER), Elsevier came forward to publish selected papers presented in the 2nd international conference. Papers were selected from different sessions in order to cover the scope of the conference. The selection was very difficult due to the many good papers and the limited number that can be published in this issue. This special issue contains selected articles on diurnal variations of 218Po, 214Pb, and 214Po and their effect on atmospheric electrical conductivity in the lower atmosphere, 210 Po/210Pb ratios in the atmosphere, estimation of Kd of 210Po and 210Pb, enrichment and particle size dependence of 210Po in coal ash, lifetimes of 214Po and 212Po, 210Pb as a tracer of soil erosion studies, problems associated with 210Pb dating of sediments, 210Po and 210Pb as tracers in a riverine and coastal waters, mobility of 210 Po and 210Pb in acid mine discharge, etc. Most of these papers were handled by two guest editors, Profs. Karunakara Naregundi and Mark Baskaran. The 3rd conference in this series is being organized by Institute of Nuclear Sciences, Ege University during October 11e14, 2015 in Kusadasi, Turkey. We look forward for a larger participation of scientists in the conference.
Acknowledgement The guest editors wish to thank Dr. Steve Sheppard, Editor-inChief, Journal of Environmental Radioactivity, and Elsevier Science Ltd. for making this Special Issue possible. Thanks are also extended to all of the external reviewers who contributed their valuable time and expertise in providing constructive criticism. Thanks are due to funding agencies of Govt. of India: The Board of Research in Nuclear Sciences (BRNS) (No. 2012/17/34/323/214/ BRNS/3092 dated 28 March 2013), Department of Science and Technology, Ministry of Science and Technology (SERB/F/4914/2012-13 dated 04/12/2012), Ministry of Earth Sciences (SERB/F/4914/2012-13 dated 04/12/ 2012), University Grants Commission, Atomic Energy Regulatory Board (AERB) (AERB/ITSD/CSRP-2/2013/593 dated Feb. 12, 2013) for funding the conference. We are grateful to the Mangalore University for the financial support, extending conference hall and all logistical support for the conference. We again thank all the speakers, participants and the members of the various committees for the success of this conference. References Aarkrog, A., Baxter, M., Bologa, S., Bettencourt, A.O., Bojanowski, R., Charmasson, A.S., Cunha, P.I., 1997. A comparison of doses from 137Cs and 210 Po in marine food: a major international study. J. Environ. Radioact. 34, 69e90. Parfenov, Y.D., 1974. Po-210 in the environment and in the human organism. Atom. Energy Rev. 12, 75e143. Porcelli, D., Baskaran, M., 2011. An overview of isotope geochemistry in environmental studies. In: Baskaran, M. (Ed.), Handbook of Environmental Isotope Geochemistry. Springer, Heidelberg, Dordrecht, London, New York, ISBN 9783-642-10636-1, pp. 11e32 (Printed in 2 volumes) e-ISBN 978-3-642-10637-8.
N. Karunakara, Guest Editor* Radioecology and Environmental Radioactivity Research Laboratory, Mangalore University, Mangalagangothri 574199, India Mark Baskaran, Guest Editor Wayne State University, Detroit, MI, USA E-mail address: [email protected]. * Corresponding author. E-mail address: [email protected] (N. Karunakara).
Available online 3 September 2014
