Lead isotopes in Earth/planetary science isotopic compositions isotope-amount ratio stable isotopes radioactive decay

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$Stable isotope Relative atomic mass Mole fraction 204 Pb 203.973 044 0.014 206 Pb 205.974 466 0.241 207 Pb 206.975 897 0.221 208 Pb 207.976 653 0.$ For example, in one study of Lake Härsvatten in Sweden, the isotope-amount ratio n( 206 Pb)/n( 207 Pb) measured at different sediment depths in different areas throughout the lake showed patterns of

For example, in one study of Lake Härsvatten in Sweden, the isotope-amount ratio n( 206 Pb)/n( 207 Pb) measured at different sediment depths in different areas throughout the lake showed patterns of

1 Stable isotope Relative atomic mass Mole fraction 204 Pb Pb Pb Pb Lead isotopes in Earth/planetary science The study of lead isotopic compositions is used to model the distribution of pollution in water and on land (Figure 1). For example, in one study of Lake Härsvatten in Sweden, the isotope-amount ratio n( 206 Pb)/n( 207 Pb) measured at different sediment depths in different areas throughout the lake showed patterns of accumulation of lead pollution. In some cases, these patterns could be related to sediment distribution patterns. Another study used 210 Pb dating methods to study the vertical accretion of sediments in canals and wetland areas in Louisiana over the last years [549, 550]. Three of the stable isotopes of lead ( 206 Pb, 207 Pb, and 208 Pb) are produced by the radioactive decay of isotopes of uranium and thorium ( 238 U, 235 U, and 232 Th, respectively) and are largely

2 unaffected by environmental and metallurgical processes. Therefore, by examining various isotopeamount ratios of lead isotopes, it is possible to approximate the age of a material. It is also possible to use this information to trace the origins of an object or material [ ]. Lead isotopes in forensic science and anthropology Different geographic regions may have characteristic lead isotopic compositions because of variations in the ages and chemical composition of the rocks and minerals in the local environment. Therefore, lead produced at a particular location can have a unique lead isotopic composition and it is possible to trace the history and origins of pollutants by measuring the relative amounts of the four stable isotopes of lead ( 208 Pb, 207 Pb, 206 Pb, and 204 Pb) (Figure 2) [ ]. Using isotopic abundance data, the source of this toxic metal can be identified as it moves through air and water and eventually to living systems [555, 556]. Scientists have analyzed lead in air pollution in California and found that it originated from Asia. Airborne particles from China have relatively higher amounts of 208 Pb, which distinguishes the lead isotopic signature between airborne particles from Asia and North America. This knowledge could have implications in understanding the mixing of particles in the atmosphere and how pollutants are transported over vast distances [555, 556, 558, 559]. Mapping the distribution of lead pollution by studying 204 Pb, 206 Pb, 207 Pb and 208 Pb also allows the identification of those human activities that contribute the highest amounts of lead to the environment [555, 556, 560]. The measurement of the isotopic composition of lead in blood can help to determine the source of this toxic element in the body [561]. Lead is stored in bones and teeth. If a person moves to a different geographical region, the isotopic composition of the lead in the teeth is maintained, recording their place of origin. Bone can store lead for long periods of time (about 20 years), and some skeletal lead may be older and have a different isotopic composition than other skeletal lead. These differences reflect exposure to lead of different origins. By studying the isotope-amount ratio n( 206 Pb)/n( 204 Pb) and n( 207 Pb)/n( 206 Pb) in bone and teeth, it is possible to determine someone s place of origin. For example, isotopes of lead were analyzed in the teeth and bones of a human mummy, known as the Iceman, to help determine his place of origin [ ]. 210 Pb is a relatively short-lived radioactive isotope of lead that is constantly produced by the decay of 222 Rn in the atmosphere. While living, humans naturally incorporate 210 Pb from the environment into bones and tissues. The amount of 210 Pb in the body reaches equilibrium such that the 210 Pb ingested is in equilibrium with the 210 Pb that decays. When a person dies, this incorporation of 210 Pb ceases and the relative amount of this isotope in the body decreases. Therefore, measurement of the 210 Pb activity in a corpse can help determine time of death [564, 565]. Lead isotope-amount ratios (n( 206 Pb)/n( 204 Pb), n( 207 Pb)/n( 204 Pb), and n( 208 Pb)/n( 204 Pb)) along with isotope-amount ratios of silver (n( 107 Ag)/n( 109 Ag)) and isotope-amount ratios of copper (n( 65 Cu)/n( 63 Cu)) have been used to determine the origin of European coins (Figure 3) and to investigate the flow of goods in the world market over time. Metals from Peru and Mexico and those from European mining have distinct isotopic signatures that enable the origin of the metal to be determined by examining the isotopic compositions of silver, copper, and lead in the coins. Abundant silver sources mined in Mexico and Peru in the 16 th century were used to mint coins, but were not a major influence in the European coin market until the 18 th century [232].

3 Fig. 1: Suspended atmospheric dust over California; it is likely that this dust originated in Asia based on lead-isotope studies. (Photo Source: SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE, NASA Earth Observatory, 2001) [559, 566].

4 Fig : Cross plot of n( 206 Pb)/n( 204 Pb) isotope ratio and n( 206 Pb)/n( 207 Pb) isotope ratio of lead in selected materials (modified from [557]).

5 Fig. 3: Cross plot of lead model age and mole fraction 109 Ag of selected coins (modified from [232]). The isotopic signatures of the lead, silver, and copper lead in the metals used to make Spanish coins can be used to trace the origin of the metals to help determine the flow of metal in the global market during the 16 th century.

6 Lead isotopes in geochronology The three natural radioactive-decay chains beginning with 238 U, 235 U, and 232 Th each have comparable half-lives that are much longer than the radioactive isotopes that follow until the production of stable isotopes of 206 Pb, 207 Pb, and 208 Pb, respectively. Therefore, one can measure the relative amounts of the radiogenic isotopes of lead to determine the length of time that elapsed since uranium and thorium atoms were incorporated into rocks and minerals. Typically, this method is used to date minerals that are tens of millions to billions of years old. The uranium-lead dating method was used to determine some of the first accurate ages of the Earth (~4.55 billion years) [562, 563, 565].

7 Glossary atomic number (Z) The number of protons in the nucleus of an atom. electron elementary particle of matter with a negative electric charge and a rest mass of about kg. element (chemical element) a species of atoms; all atoms with the same number of protons in the atomic nucleus. A pure chemical substance composed of atoms with the same number of protons in the atomic nucleus [703]. [return] gamma rays (gamma radiation) a stream of high-energy electromagnetic radiation given off by an atomic nucleus undergoing radioactive decay. The energies of gamma rays are higher than those of X-rays; thus, gamma rays have greater penetrating power. half-life (radioactive) the time interval that it takes for the total number of atoms of any radioactive isotope to decay and leave only one-half of the original number of atoms. isotope one of two or more species of atoms of a given element (having the same number of protons in the nucleus) with different atomic masses (different number of neutrons in the nucleus). The atom can either be a stable isotope or a radioactive isotope. isotopic abundance (mole fraction or amount fraction) the amount (symbol n) of a given isotope (atom) in a sample divided by the total amount of all stable and long-lived radioactive isotopes of the chemical element in the sample. [return] isotope-amount ratio (r) amount (symbol n) of an isotope divided by the amount of another isotope of the chemical element in the same system [706]. [return] isotopic composition number and abundance of the isotopes of a chemical element that are naturally occurring [706]. [return] isotope ratio (R) number (symbol N) of atoms of one isotope divided by the number of atoms of another isotope of the same chemical element in the same system [706]. [return] mole fraction (amount fraction or isotopic abundance) the amount (symbol n) of a given isotope (atom) in a sample divided by the total amount of all stable and long-lived radioactive isotopes of the chemical element in the sample. [return] neutron an elementary particle with no net charge and a rest mass of about kg, slightly more than that of the proton. All atoms contain neutrons in their nucleus except for protium ( 1 H). proton an elementary particle having a rest mass of about kg, slightly less than that of a neutron, and a positive electric charge equal and opposite to that of the electron. The number of protons in the nucleus of an atom is the atomic number.

8 radioactive decay the process by which unstable (or radioactive) isotopes lose energy by emitting alpha particles (helium nuclei), beta particles (positive or negative electrons), gamma radiation, neutrons or protons to reach a final stable energy state. [return] radioactive isotope (radioisotope) an atom for which radioactive decay has been experimentally measured (also see half-life). [return] radiogenic produced by the decay of a radioactive isotope, but which itself may or may not be radioactive. [return] stable isotope an atom for which no radioactive decay has ever been experimentally measured. [return] X-rays electromagnetic radiation with a wavelength ranging from 0.01 to 10 nanometers shorter than those of UV rays and typically longer than those of gamma rays. References 232. A. M. Desaulty, Telouk, P., Albalat, E., and Albarede, F. Proceedings of the National Academy of Sciences. 108 (22), 9002 (2011) /pnas R. Bindler, Renberg, I., Brannvall, M. L., Emteryd, O., and El Daoushy, F. Limnology and Oceanography. 46 (1), 178 (2001) R. D. DeLaune, Whitcomb, J. H., Patrick, W. H., Jr., Pardue, J. H., and Pezeshki, S. R. Estuaries. 12 (4), 247 (1989) R. W. Hurst. Environmental Geosciences. 9 (1), 1 (2002) U. o. Arizona. Clues To African Archaeology Found In Lead Isotopes. ScienceDaily Feb M. Tatsumoto, and Rosholt, J. N. Science. 167 (3918), 461 (1970) R. H. Brill. Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences. 269 (1193), 143 (1970) I. Renberg, Brännvall, M.L., Bindler, R., and Emteryd, O. Ambio. 29 (3), 150 (2000) M. K. Reuer, and Weiss, D. J. Mathematical, Physical and Engineering Sciences. 360 (1801), 2889 (2002) a. J. L. E. T. J. Chow. Science. 169 (1970) S. A. Ewing, Christensen, J.N., Brown, S.T., Vancuren, R.A., Cliff, S.S., and Depaolo, D.J. Environmental Science & Technology. 44 (23), 8911 (2010) D. Krotz. Lead Isotopes Yield Clues to How Asian Air Pollution Reaches California. Lawrence Berkeley National Laboratory News Center Feb D. Cicchella, Vivo, B. De, Lima, A., Albanese, S., McGill, R.A.R., and Parrish, R.R. Geochemistry: Exploration, Environment, Analysis. 8 (1), 103 (2008) R. H. Gwiazda, and Smith, D.R. Environmental Health Perspectives. 108 (11), 1091 (2000) B. L. Gulson, and Gillings, B.R. Environmental Health Perspectives. 105 (8), 820 (1997).

9 563. W. Müller, Fricke, H., Halliday, A. N., McCulloch, M. T., and Wartho, J.A. Science. 302 (5646), 862 (2003) P. Rincon. Isotopes could improve forensics. BBC News Online D. R. Smith, Osterloh, J.D., and Flegal, A.R. Environmental Health Perspectives. 104 (1), 60 (1996) I. U. o. P. a. A. Chemistry. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Blackwell Scientific Publications, Oxford (1997) Coplen. Rapid Communications in Mass Spectrometry. 25 (2011).

Stable isotope. Relative atomic mass. Mole fraction 203 Tl Tl Thallium isotopes in Earth/planetary science

$Stable isotope. Relative atomic mass. Mole fraction 203 Tl Tl Thallium isotopes in Earth/planetary science$ Stable isotope Relative atomic mass Mole fraction 203 Tl 202.972 345 0.2952 205 Tl 204.974 428 0.7048 Thallium isotopes in Earth/planetary science Because molecules, atoms, and ions of the stable isotopes