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Invention of Carbon 13 Dating and Molecular Chronology

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This conference presentation describes the invention of molecular carbon-13 dating, a relative dating method that allows to mesure the relative age of organic substances in complex. This invention is based on the discovery of temporal pools of molecular susbtances in soils. The findings open a new scientific field, named Molecular Chronology, to study the source, transformation, persistence, sequestration, transfer and toxicity of organic substances in complex media, such as living organisms, food, soil, waters and sediments. Similarly to sedimentary stratigraphy that uses layers to date sediments, molecular chronology uses temporal pools to date molecules. As a consequence, any biological or environmental samples becomes a 'fossil record' of substances of different age. Molecular chronology is thus expected to deliver new knowledge in all fields studying complex systems, such as biology, medicine, food science, agronomy, environmental science, soil science and geology. This is an invited conference at SIL2018, the Congress of the International Society of Limnology, in Nanjing, August 2018.

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Invention of Carbon 13 Dating and Molecular Chronology

  1. 1. Invention of Carbon 13 Dating and Molecular Chronology Eric LICHTFOUSE Aix-Marseille University Chief Editor, Environmental Chemistry Letters SIL2018 Nanjing Publications: https://cv.archives-ouvertes.fr/eric-lichtfouse
  2. 2. Old materials in modern media A glass of water contains 2,000 water molecules from the last glass of water drank by Julius Caesar, 100-44 BC
  3. 3. Pollutant societal issues 8.4 million people deaths caused by pollution each year All natural media and living organisms are contaminated Pesticides in suface waters 2017
  4. 4. Pollutant scientific issues Sources? Transfer? Persistence? Health risk? How much time a pollutant stays in a complex system?
  5. 5. Bound residues Unknown sequestration and release mechanisms Dating is actually limited to sedimentary studies
  6. 6. Compound specific isotope analysis Access to 13C composition of individual substances in complex media Invented by Prof. John Hayes Analusis 23, 364 (1995) Rapid Commun Mass Spectrom 14, 1337 (2000)
  7. 7. 13C Labelling Natural or artificial Soils, sediments, water, living organisms... Reveals sources and dynamics Few studies at the molecular level First 13C analysis of soil Individual compounds Org Geochem 22, 349 (1994) Tetrahedron Lett 36, 529 (1995)
  8. 8. Discovery of temporal pools Hypothesis: encapsulated substances are older We fractionated a soil sample into six pools 13C analysis of the soil C31 n-alkane
  9. 9. Carbon 13 dating Calculation using first order kinetic law C31 alkane trapped in humin is older C31 alkane in large particles is younger Can be applied to any media, any isotope C31 ALKANE IN: d13C (‰) Maize-C (%) Relative age (years) Bulk soil extraction -28.1 50.33 0 Humin extract -29.7 39.74 - 6.7 Humin pyrolysate -29.7 39.74 - 6.7 0-50 µm fraction -27.3 55.63 + 3.2 50-200 µm fraction -24.3 74.50 + 21.1 200-2000 µm fraction -24.0 77.48 + 25.1 Env Chem Lett 10, 97 (2012)
  10. 10. Mecanism of encapsulation Isotopic difference: humin-bound compounds are really bound Not a lack of exhaustive extraction, as pointed by reviewers… Humin-bound alkane are trapped by non- covalent bonds Naturwissenschaft 85, 449 (1998)
  11. 11. Sources of alkanes in cultivated soils C16 : not labelled – fossil C27 : labelled – plant derived Absence of labelling in a system is also significant Geochim Cosmochim Acta 61, 1891 (1997) Time (years) d13C (‰)
  12. 12. Sources of PAH in cultivated soils PAH: not labelled - fossil Organic C: labelled – plant derived Org Geochem 26, 353 (1997)
  13. 13. Sources of fatty acids in soils Labelling with 13C-glucose Short-chain: labelled - microbes Long-chain: not labelled – plant derived Org Geochem 23, 849 (1995)
  14. 14. Reconstruction of fossil fuel pollution - Plant n-alkane d13C -30‰ - Fossil fuel n-alkane d13C -35‰ Calculation of fossil fuel C% in each compound Env Chem Lett 10, 97 Org Geochem 23, 969 (1995)
  15. 15. Biogenic links of compounds in sediments Green River sediment, 60 million years old n-Alkanes and fatty acids have similar biological source Tetrahedron Lett 33, 8093 (1992) COOH
  16. 16. Conclusion 1: a new science: Molecular Chronology 10 years 20 years 30 years Stratigraphy Geochronology - Use layers Molecular chronology - Use temporal pools KNOWN NEW
  17. 17. Conclusion 2: invention of carbon 13 dating Can be applied to any organic substance in complex media Can be used in any complex media labelled naturally or articicially Other isotopes are possible Biology Medicine Food Science Environmental Science Soil Science Water Science Geology
  18. 18. Conclusion 3 Collaborations to develop 13C dating and molecular chronology are welcome Eric.Lichtfouse@inra.fr Biology Medicine Food Science Environmental Science Soil Science Water Science Geology

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