Metal speciation in Dutch soils: Field-based partition coefficients for heavy metals at background levels
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Type
Report
Language
en
Date
1995-12-31
Research Projects
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Journal Issue
Title
Metal speciation in Dutch soils: Field-based
partition coefficients for heavy metals at background
levels
Translated Title
Metaal speciatie in Nederlandse bodems:
veldgebaseerde partitiecoefficienten voor zware metalen op
achtergrondniveau
Published in
Abstract
Van 13 Nederlandse bodemmonsters zijn de totaalgehalten
bepaald van de zware metalen Cd, Cu, Ni, Pb en Zn, zowel in de vaste fase
als in het poriewater. De bodems zijn gekarakteriseerd in termen van
organisch koolstofgehalte, pH, kleigehalte en kationuitwisselcapaciteit.
Partitie coefficienten (Kp) zijn gedefinieerd als de verhouding van de
metaalconcentratie in de vaste fase en in het poriewater. Gemiddelde
Kp-waarden waren 706, 241, 1337,10785 en 1175 l per kg voor respectievelijk
Cd, Cu, Ni, Pb en Zn. Deze waarden zijn ongeveer twee orden van grootte
kleiner dan de partitiecoefficienten die voorgesteld zijn bij de
harmonisatie van milieukwaliteitsdoelstellingen voor de compartimenten
bodem, sediment en water. De variatie in Kp bleek in dezelfde orde van
grootte te zijn als de gemiddelde waarde van Kp. Dit is het gevolg van
variatie in bodem en poriewatersamenstelling. Voor alle metalen kon de Kp
waarde goed gecorreleerd worden aan een gemodificeerde Freundlich isotherm
voor de kationuitwisselcapaciteit, hetgeen een maat is voor het aantal
beschikbare bindingsplaatsen in de bodem.
For 13 Dutch soil samples, total concentrations in the solid phase and in the soil solution were determined for the heavy metals Cd, Cu, Ni, Pb and Zn. The soils were characterized in terms of organic carbon content, pH, clay content and cation exchange capacity. Average field-based partition coefficients (Kp) were calculated as the ratio of the metal concentration in the solid phase and the soil solution and were 706, 241, 1337, 10785 and 1175 l kg-1 for Cd, Cu, Ni, Pb and Zn, respectively. These values are approximately two orders of magnitude smaller than partition coefficients proposed for the harmonization of integrated quality objectives for the compartments soil, sediment and water. For the present set of samples, the variability of Kp was in the same order of magnitude as its average value, due to variations in soil and pore water composition. For all metals, Kp-values could be well correlated to a Freundlich modified isotherm with respect to the cation exchange capacity of the soil, which is a measure for the amount of available binding sites.
For 13 Dutch soil samples, total concentrations in the solid phase and in the soil solution were determined for the heavy metals Cd, Cu, Ni, Pb and Zn. The soils were characterized in terms of organic carbon content, pH, clay content and cation exchange capacity. Average field-based partition coefficients (Kp) were calculated as the ratio of the metal concentration in the solid phase and the soil solution and were 706, 241, 1337, 10785 and 1175 l kg-1 for Cd, Cu, Ni, Pb and Zn, respectively. These values are approximately two orders of magnitude smaller than partition coefficients proposed for the harmonization of integrated quality objectives for the compartments soil, sediment and water. For the present set of samples, the variability of Kp was in the same order of magnitude as its average value, due to variations in soil and pore water composition. For all metals, Kp-values could be well correlated to a Freundlich modified isotherm with respect to the cation exchange capacity of the soil, which is a measure for the amount of available binding sites.
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