1
|
D'Souza RS, Nayak SR, Mohan MP, Bharath S, Arya Krishnan K, Kamath S, Diéguez A, Agulló L, Gómez-Martínez I, Santos-Arévalo FJ, García-Tenorio R, Ravi PM, Karunakara N. Optimisation of a batch thermal combustion method using a tube furnace oxidation system (pyrolyser) and LSC for carbon-14 determination in environmental matrices. J Environ Radioact 2021; 226:106345. [PMID: 33032834 DOI: 10.1016/j.jenvrad.2020.106345] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2020] [Revised: 06/17/2020] [Accepted: 06/23/2020] [Indexed: 06/11/2023]
Abstract
Accelerator mass spectrometry and benzene synthesis coupled with liquid scintillation spectrometry are often used for accurate measurements of 14C activity in the environmental matrices. Thermal oxidation is one of the methods employed for 14C determination in environmental matrices. In this method, the sample is oxidised at high temperature (600-900 °C) to convert carbon species to CO2 and trapped in an amine-based absorber for determining the activity in a liquid scintillation counting (LSC) system. In this study, the performance of a commercially available tube furnace system (pyrolyser), for batch combustion of samples, was evaluated for the determination of 14C specific activity in terrestrial biota samples. Significant improvements over the manufacturer specified method, which is primarily designed for analysis of samples with activity well above the environmental background level, was implemented to achieve accurate determination of 14C specific activity at ambient background level. In the improved method, the CO2 produced from the combustion of the sample was isolated from the combustion products through cryogenic trapping and then absorbed in the absorber (Carbo-Sorb E) through a simple off-line transfer process. This allowed (i) optimisation of CO2 absorption by the absorber (2.2477 g of CO2/10 mL), (ii) achieving good accuracy and precision in the measurements, and a minimum detectable activity value of 13 Bq kg-1C for a counting time of 300 min (7 Bq kg-1C for 1000 min), (iii) avoiding uncertainty associated with the determination of recovery of 14C in the combustion and trapping process, and (iv) elimination of the need for an independent determination of carbon content (%) for expressing the results in terms of 14C specific activity. The method is capable of yielding accurate results with a deviation of <2.4% from the target value for IAEA C3 quality assurance reference material (with a relative standard deviation of 1.40%, and relative error of 0.34%). The combined uncertainty (1σ) associated with the measurements was computed to be 3.4%. Upon optimisation, the suitability of the method for the determination of 14C specific activity in typical terrestrial biota samples of clean air region (region not affected by local anthropogenic sources) and for the quantification of a small increase in the 14C activity above ambient levels in the vicinity of a nuclear power plant is demonstrated.
Collapse
Affiliation(s)
- Renita Shiny D'Souza
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - S Rashmi Nayak
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - M P Mohan
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - S Bharath
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - K Arya Krishnan
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - Srinivas Kamath
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - A Diéguez
- Centro Nacional de Aceleradores, Universidad de Sevilla, CSIC, Junta de Andalucía, Av. Thomas Alva Edison 7, 41092, Seville, Spain
| | - L Agulló
- Centro Nacional de Aceleradores, Universidad de Sevilla, CSIC, Junta de Andalucía, Av. Thomas Alva Edison 7, 41092, Seville, Spain
| | - I Gómez-Martínez
- Centro Nacional de Aceleradores, Universidad de Sevilla, CSIC, Junta de Andalucía, Av. Thomas Alva Edison 7, 41092, Seville, Spain
| | - F J Santos-Arévalo
- Centro Nacional de Aceleradores, Universidad de Sevilla, CSIC, Junta de Andalucía, Av. Thomas Alva Edison 7, 41092, Seville, Spain
| | - R García-Tenorio
- Centro Nacional de Aceleradores, Universidad de Sevilla, CSIC, Junta de Andalucía, Av. Thomas Alva Edison 7, 41092, Seville, Spain
| | - P M Ravi
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India
| | - N Karunakara
- Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, 574199, India.
| |
Collapse
|
2
|
Villa-Alfageme M, Chamizo E, Santos-Arévalo FJ, López-Gutierrez JM, Gómez-Martínez I, Hurtado-Bermúdez S. Natural and artificial radionuclides in a marine core. First results of 236U in North Atlantic Ocean sediments. J Environ Radioact 2018; 186:152-160. [PMID: 29061309 DOI: 10.1016/j.jenvrad.2017.10.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 10/03/2017] [Accepted: 10/03/2017] [Indexed: 06/07/2023]
Abstract
There are very few data available of 236U in marine sediment cores. In this study we present the results from the first oceanic depth profile of 236U in a sediment core sampled in the North Atlantic Ocean, at the PAP site (4500 m depth, Porcupine Abyssal Plain (PAP) site, 49°0' N, 16°30' W). Additionally, the sediment core was radiologically characterized through the measurement of anthropogenic 137Cs, 239Pu, 240Pu, 129I and 14C and natural 210Pb, 40K and 226Ra. The measured 236U concentrations decrease from about 90·106 at g-1 at the seafloor down to 0.5·106 at g-1 at 6 cm depth. They are several orders of magnitude lower than the reported values for soils from the Northern Hemisphere solely influenced by global fallout (i.e. from 2700·106 to 7500·106 at g-1). 236U/238U atom ratios measured are at least three orders of magnitude above the estimated level for the naturally occurring dissolved uranium. The obtained inventories are 1·1012 at m-2 for 236U, 80 Bq m-2 for 137Cs, 45 Bq m-2 for 239+240Pu and 2.6·1012 at m-2 for 129I. Atomic ratios for 236U/239Pu, 137Cs/236U and 129I/236U, obtained from the inventories are 0.036, 0.11 and 2.5 respectively. Concentration profiles show mobilization probably due to bioturbation from the abundant detritivore holothurian species living at the PAP site sea-floor. The range of 236U, 137Cs, 239+240Pu and 129I values, inventories and ratios of these anthropogenic radionuclides are more similar to the values due to fall-out than values from a contribution from the Nuclear Fuel Reprocessing Plants dispersed to the south-west of the North Atlantic Ocean. However, signs of an additional source are detected and might be associated to the nuclear wastes dumped on the Eastern North Atlantic Ocean.
Collapse
Affiliation(s)
- M Villa-Alfageme
- Dpto. Física Aplicada II, Universidad de Sevilla, Av. Reina Mercedes 4A, 41012, Sevilla, Spain.
| | - E Chamizo
- Centro Nacional de Aceleradores, Universidad de Sevilla, C Thomas Alva Edison, 7, 41092, Sevilla, Spain
| | - F J Santos-Arévalo
- Centro Nacional de Aceleradores, Universidad de Sevilla, C Thomas Alva Edison, 7, 41092, Sevilla, Spain
| | - J M López-Gutierrez
- Centro Nacional de Aceleradores, Universidad de Sevilla, C Thomas Alva Edison, 7, 41092, Sevilla, Spain; Dpto. Física Aplicada III, Universidad de Sevilla, Virgen de África, 41011, Sevilla, Spain
| | - I Gómez-Martínez
- Centro Nacional de Aceleradores, Universidad de Sevilla, C Thomas Alva Edison, 7, 41092, Sevilla, Spain
| | - S Hurtado-Bermúdez
- Centro de Investigación, Tecnología e Innovación CITIUS, Universidad de Sevilla, Av. Reina Mercedes 4B, 41012, Sevilla, Spain
| |
Collapse
|