J.M. Abril Department of Applied Physics (I); University of Seville (Spain) IAEA Regional Training Course on Sediment Core Dating Techniques. RAF7/008 Project Lecture 1: Radionuclides of the environment and general aspects Concentration and distribution factors. k d variability Granulometric speciation k d in saturated porous media : “intrinsic” values Experiments on depth penetration patterns J.M. Abril, University of Seville

Some radionuclides and other hazardous materials, such as heavy metals, are highly particle-reactive. Their uptake by suspended particulate matter (SPM) and bottom sediments plays an important role in the fate of these pollutants. Remember: Depending on the pollutant, 1 gram of SPM can uptake more activity (or units of pollutants) than 1 m 3 of water. J.M. Abril, University of Seville

The uptake is a surface-mediated phenomenon. SPM has very high specific surface area (SSA) Naturally occurring particulate matter in aquatic systems usually exhibits areas with uncompensated negative charges. J.M. Abril, University of Seville

K d provides a convenient means to describe the relationship between radionuclide concentrations in SPM or bottom sediments and water Notes: Field observation Laboratory experiments Dynamic equilibrium Notes: Field observation Laboratory experiments Dynamic equilibrium J.M. Abril, University of Seville 4

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Concentration facfors J.M. Abril, University of Seville 6

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Concentration facfors J.M. Abril, University of Seville 8

K d variability For many radionuclides, field k d values from different environments, can vary within a range of more than two orders of magnitude ( IAEA, 1985) J.M. Abril, University of Seville 9

K d vs. particle-size Basic model handling spherical particles Pores and free edges 10 J.M. Abril, University of Seville

Definitions: a s, a c, ξ J.M. Abril, University of Seville 11

Man-made radionuclides interacting with “natural” particles J.M. Abril, University of Seville 12

Naturally occurring radionuclides a c > 0 The full equation has to be used Two extreme behaviors depending on radionuclide solubility Depleted outer layer for relatively soluble radionuclides Enriched outer layer for highly particle-reactive radionuclides J.M. Abril, University of Seville 13

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Caesium J.M. Abril, University of Seville 15

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SPM in natural waters is mainly present in the form of flocs (or aggregates) mixed with single mineral particles. “Many particles” effects in k d variability J.M. Abril, University of Seville 17

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Global effects of particle size spectra and mineralogical composition J.M. Abril, University of Seville 19

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Bathymetric map for lake HÁRSVATTEN (Sweden). Understanding spatial speciation… J.M. Abril, University of Seville 21

Hydrodynamic transport Z Path length Settling velocity Stokes’ Law J.M. Abril, University of Seville 22

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210 Pb J.M. Abril, University of Seville 25

Competition with cations related to SALINITY [ S ] J.M. Abril, University of Seville 26

More details in: Parts I and II J.M. Abril, University of Seville 27

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A phosphate fertilizer factory pumped into the Odiel river (SW Spain) a suspension of PG particles (NORM material). We wanted to know how these radionuclide-enriched material was spread onto bottom sediments Direct gamma measurements of radionuclide concentrations would provide concentrations under MDL J.M. Abril, University of Seville 29

kdkd r r kdkd C(r) r r PG susp Natural p. F1F1 F2F2 J.M. Abril, University of Seville 30

kdkd r J.M. Abril, University of Seville 31

Materials and methods 3-5 kilograms of sediments were collected at each sampling point The samples were dried (24 h at 110°C), mechanically disaggregated and sieved in a sieving-pile. J.M. Abril, University of Seville 32

234 Th J.M. Abril, University of Seville 33

226 Ra J.M. Abril, University of Seville 34

Bickford Reservoir (USA) Benoit and Hemond, Geochimica et Cosmochimica Acta 55, Evidence for diffusive redistribution of 210 Pb in lake sediments % in solids J.M. Abril, University of Seville 35

Bickford Reservoir (USA) J.M. Abril, University of Seville 36

Bickford Reservoir (USA) J.M. Abril, University of Seville 37

Radionuclide uptake by sediment columns H. Barros and J.M. Abril Radionuclide uptake by sediment columns H. Barros and J.M. Abril J.M. Abril, University of Seville 38

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