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Radiometric dating,radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon,in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products,which form at a known constant rate of decay. The use of radiometric dating was first published in 1907 by Bertram Boltwood and is now the principal source of information about the absolute age of rocks and other geological features,including the age of fossilized life forms or the age of Earth itself,and can also be used to date a wide range of natural and man-made materials.
Tritium or hydrogen-3 is a rare and radioactive isotope of hydrogen with half-life ~12.3 years. The tritium nucleus contains one proton and two neutrons,whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and no neutrons,and that of non-radioactive hydrogen-2 (deuterium) contains one proton and one neutron. Tritium is the heaviest particle-bound isotope of hydrogen. It is one of the few nuclides with a distinct name. The use of the name hydrogen-3,though more systematic,is much less common.
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons,of which 6 are valence electrons. Uranium radioactively decays,usually by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes,making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 and uranium-235. Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil,rock and water,and is commercially extracted from uranium-bearing minerals such as uraninite.
A radionuclide (radioactive nuclide,radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons,giving it excess nuclear energy,and making it unstable. This excess energy can be used in one of three ways:emitted from the nucleus as gamma radiation;transferred to one of its electrons to release it as a conversion electron;or used to create and emit a new particle (alpha particle or beta particle) from the nucleus. During those processes,the radionuclide is said to undergo radioactive decay. These emissions are considered ionizing radiation because they are energetic enough to liberate an electron from another atom. The radioactive decay can produce a stable nuclide or will sometimes produce a new unstable radionuclide which may undergo further decay. Radioactive decay is a random process at the level of single atoms:it is impossible to predict when one particular atom will decay. However,for a collection of atoms of a single nuclide the decay rate,and thus the half-life (t1/2) for that collection,can be calculated from their measured decay constants. The range of the half-lives of radioactive atoms has no known limits and spans a time range of over 55 orders of magnitude.
Nuclear chemistry is the sub-field of chemistry dealing with radioactivity,nuclear processes,and transformations in the nuclei of atoms,such as nuclear transmutation and nuclear properties.
Organic geochemistry is the study of the impacts and processes that organisms have had on the Earth. It is mainly concerned with the composition and mode of origin of organic matter in rocks and in bodies of water. The study of organic geochemistry is traced to the work of Alfred E. Treibs,"the father of organic geochemistry." Treibs first isolated metalloporphyrins from petroleum. This discovery established the biological origin of petroleum,which was previously poorly understood. Metalloporphyrins in general are highly stable organic compounds,and the detailed structures of the extracted derivatives made clear that they originated from chlorophyll.
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope-ratio mass spectrometry,and can reveal information about the ages and origins of rock,air or water bodies,or processes of mixing between them.
Osmium (76Os) has seven naturally occurring isotopes,five of which are stable:187Os,188Os,189Os,190Os,and (most abundant) 192Os. The other natural isotopes,184Os,and 186Os,have extremely long half-life (1.12×1013 years and 2×1015 years,respectively) and for practical purposes can be considered to be stable as well. 187Os is the daughter of 187Re (half-life 4.12×1010 years) and is most often measured in an 187Os/188Os ratio. This ratio,as well as the 187Re/188Os ratio,have been used extensively in dating terrestrial as well as meteoric rocks. It has also been used to measure the intensity of continental weathering over geologic time and to fix minimum ages for stabilization of the mantle roots of continental cratons. However,the most notable application of Os in dating has been in conjunction with iridium,to analyze the layer of shocked quartz along the Cretaceous–Paleogene boundary that marks the extinction of the dinosaurs 66 million years ago.
The environmental isotopes are a subset of isotopes,both stable and radioactive,which are the object of isotope geochemistry. They are primarily used as tracers to see how things move around within the ocean-atmosphere system,within terrestrial biomes,within the Earth's surface,and between these broad domains.
Environmental radioactivity is part of the overall background radiation and is produced by radioactive materials in the human environment. While some radioisotopes,such as strontium-90 (90Sr) and technetium-99 (99Tc),are only found on Earth as a result of human activity,and some,like potassium-40 (40K),are only present due to natural processes,a few isotopes,such as tritium (3H),result from both natural processes and human activities. The concentration and location of some natural isotopes,particularly uranium-238 (238U),can be affected by human activity,such as nuclear weapons testing,which caused a global fallout,with up to 2.4 million deaths by 2020.
Since the mid-20th century,plutonium in the environment has been primarily produced by human activity. The first plants to produce plutonium for use in Cold War atomic bombs were the Hanford nuclear site in Washington,and the Mayak nuclear plant,in Chelyabinsk Oblast,Russia. Over a period of four decades,"both released more than 200 million curies of radioactive isotopes into the surrounding environment –twice the amount expelled in the Chernobyl disaster in each instance."
The National Geophysical Research Institute (NGRI) is a geoscientific research organization established in 1961 under the Council of Scientific and Industrial Research (CSIR),India's largest Research and Development organization. It is supported by more than 200 scientists and other technical staff whose research activities are published in several journals of national and international interest.
Iodine-129 (129I) is a long-lived radioisotope of iodine that occurs naturally but is also of special interest in the monitoring and effects of man-made nuclear fission products,where it serves as both a tracer and a potential radiological contaminant.
Radioecology is the branch of ecology concerning the presence of radioactivity in Earth’s ecosystems. Investigations in radioecology include field sampling,experimental field and laboratory procedures,and the development of environmentally predictive simulation models in an attempt to understand the migration methods of radioactive material throughout the environment.
Radioanalytical chemistry focuses on the analysis of sample for their radionuclide content. Various methods are employed to purify and identify the radioelement of interest through chemical methods and sample measurement techniques.
A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay. It may itself be radioactive or stable.
Kliti Grice is an Australian chemist and geochemist known for her work in identifying geological and environmental causes for mass extinction events. Her research integrates geological information with data on molecular fossils and their stable carbon,hydrogen and sulfur isotopic compositions to reconstruct details of microbial,fungal and floral inhabitants of modern and ancient aquatic environments and biodiversity hot spots. This information expands our understanding of both the Earth's history and its current physical state,with implications ranging from energy and mineral resource exploration strategies to environmental sustainability encompassing climate dynamics and expected rates,durations and scale of our future planet's health. As one of the youngest women professors in Earth Sciences,she is the founding director of the Western Australian Organic and Isotope Geochemistry Centre (WA-OIGC) and is a Professor of Organic and Isotope Geochemistry at Curtin University in Perth,Western Australia.
Bioremediation of radioactive waste or bioremediation of radionuclides is an application of bioremediation based on the use of biological agents bacteria,plants and fungi to catalyze chemical reactions that allow the decontamination of sites affected by radionuclides. These radioactive particles are by-products generated as a result of activities related to nuclear energy and constitute a pollution and a radiotoxicity problem due to its unstable nature of ionizing radiation emissions.
The Philippine Nuclear Research Institute (PNRI) is a government agency under the Department of Science and Technology mandated to undertake research and development activities in the peaceful uses of nuclear energy,institute regulations on the said uses,and carry out the enforcement of said regulations to protect the health and safety of radiation workers and the general public.
Parthasarathi Chakraborty is an Indian environmental geochemist,a former senior scientist at the CSIR-National Institute of Oceanography and an associate professor at the Indian Institute of Technology Kharagpur,India. Chakraborty is known for his studies in the field of Environmental Chemistry. He made contributions to the field of Environmental Geochemistry which has facilitated our understanding of the metals-natural ligands interactions in natural and marine environments. He is a recipient of the National Geoscience Award-2015 and an elected fellow of the Indian Geophysical Union.The Council of Scientific and Industrial Research,the apex agency of the Government of India for scientific research,awarded him the Shanti Swarup Bhatnagar Prize for Science and Technology,one of the highest Indian science awards,for his contributions to Earth,Atmosphere,Ocean and Planetary Sciences in 2018.
References
- ↑ "Ian Croudace".
- 1 2 "Raddec International".
- ↑ "Ian Croudace - Google Scholar".
- ↑ "CEA Saclay International Office".[ permanent dead link ]
- ↑ "GAU-Radioanalytical Laboratories (GAU)".
- ↑ "University of Southampton join the South West Nuclear Hub".
- ↑ Micro-XRF Studies of Sediment Cores. Developments in Paleoenvironmental Research. Vol. 17. 2015. doi:10.1007/978-94-017-9849-5. ISBN 978-94-017-9848-8. S2CID 129624204.
- ↑ Marsh, Richard I.; Croudace, Ian W.; Warwick, Phillip E.; Cooper, Natasha; St-Amant, Nadereh (2017). "A new bomb-combustion system for tritium extraction". Journal of Radioanalytical and Nuclear Chemistry. 314 (2): 651–658. doi:10.1007/s10967-017-5446-0. PMC 5658464 . PMID 29104338. S2CID 35959787.
- ↑ "ITRAX: description and evaluation of a new multi-function X-ray core scanner".
- ↑ Miller, Helen; Croudace, Ian W.; Bull, Jonathan M.; Cotterill, Carol J.; Dix, Justin K.; Taylor, Rex N. (2014). "A 500 Year Sediment Lake Record of Anthropogenic and Natural Inputs to Windermere (English Lake District) Using Double-Spike Lead Isotopes, Radiochronology, and Sediment Microanalysis" (PDF). Environmental Science & Technology. 48 (13): 7254–7263. Bibcode:2014EnST...48.7254M. doi: 10.1021/es5008998 . PMID 24902065.
- ↑ Fielding, J. J.; Croudace, I. W.; Kemp AES; Pearce, R. B.; Cotterill, C. J.; Langdon, P.; Avery, R. (2020). "Tracing lake pollution, eutrophication and partial recovery from the sediments of Windermere, UK, using geochemistry and sediment microfabrics" (PDF). The Science of the Total Environment. 722: 137745. Bibcode:2020ScTEn.72237745F. doi:10.1016/j.scitotenv.2020.137745. PMID 32199357. S2CID 214607361.
- ↑ "High resolution scanning of South Pacific lake sediment: relative benefits offered by state-of-the-art micro-XRF and SEM systems". July 2019.
- ↑ Huang, Jyh-Jaan; Lin, Sheng-Chi; Löwemark, Ludvig; Liou, Ya-Hsuan; Chang, Queenie; Chang, Tsun-Kuo; Wei, Kuo-Yen; Croudace, Ian W. (2016). "A novel approach to measure elemental concentrations in cation exchange resins using XRF-scanning technique, and its potential in water pollution studies". EGU General Assembly Conference Abstracts: EPSC2016-5443. Bibcode:2016EGUGA..18.5443H.
- ↑ "Book Reviews".
- 1 2 Croudace, Ian W.; Warwick, Phillip E.; Reading, David G.; Russell, Benjamin C. (2016). "Recent contributions to the rapid screening of radionuclides in emergency responses and nuclear forensics". Trends in Analytical Chemistry. 85: 120–129. doi:10.1016/j.trac.2016.05.007.
- ↑ "USAF Aircraft Accident, Greenham Common".
- ↑ "Lithium Borate fusion: Sample Preparation & Analysis Techniques" (PDF).
- ↑ "Effective desorption of tritium from diverse solid matrices and its application to routine analysis of decommissioning materials".
