title: Cadmium Isotope Fractionation in Soil-Wheat Systems.
abstract: Analyses of stable metal isotope ratios constitute a novel tool in order to improve our understanding of biogeochemical processes in soil-plant systems. In this study, we used such measurements to assess Cd uptake and transport in wheat grown on three agricultural soils under controlled conditions. Isotope ratios of Cd were determined in the bulk C and A horizons, in the Ca(NO3)2-extractable Cd soil pool, and in roots, straw, and grains. The Ca(NO3)2-extractable Cd was isotopically heavier than the Cd in the bulk A horizon (Δ(114/110)Cdextract-Ahorizon = 0.16 to 0.45‰). The wheat plants were slightly enriched in light isotopes relative to the Ca(NO3)2-extractable Cd or showed no significant difference (Δ(114/110)Cdwheat-extract = -0.21 to 0.03‰). Among the plant parts, Cd isotopes were markedly fractionated: straw was isotopically heavier than roots (Δ(114/110)Cdstraw-root = 0.21 to 0.41‰), and grains were heavier than straw (Δ(114/110)Cdgrain-straw = 0.10 to 0.51‰). We suggest that the enrichment of heavy isotopes in the wheat grains was caused by mechanisms avoiding the accumulation of Cd in grains, such as the chelation of light Cd isotopes by thiol-containing peptides in roots and straw. These results demonstrate that Cd isotopes are significantly and systematically fractionated in soil-wheat systems, and the fractionation patterns provide information on the biogeochemical processes in these systems.
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich , Eschikon 33, CH-8315 Lindau, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Wiggenhauser
authors.affiliation: Institute of Geography, University of Bern , Hallerstrasse 12, CH-3012 Bern, Switzerland.
authors.forename: Moritz
authors.initials: M
authors.lastname: Bigalke
authors.affiliation: Institute of Geography, University of Bern , Hallerstrasse 12, CH-3012 Bern, Switzerland.
authors.forename: Martin
authors.initials: M
authors.lastname: Imseng
authors.affiliation: Swiss Soil Monitoring Network (NABO), Agroscope , Reckenholzstrasse 191, CH-8046 Zürich, Switzerland.
authors.forename: Michael
authors.initials: M
authors.lastname: Müller
authors.affiliation: Swiss Soil Monitoring Network (NABO), Agroscope , Reckenholzstrasse 191, CH-8046 Zürich, Switzerland.
authors.forename: Armin
authors.initials: A
authors.lastname: Keller
authors.affiliation: Department of Earth Science & Engineering, Imperial College London , SW7 2AZ London, U.K.
authors.forename: Katy
authors.initials: K
authors.lastname: Murphy
authors.affiliation: Department of Earth Science & Engineering, Imperial College London , SW7 2AZ London, U.K.
authors.forename: Katharina
authors.initials: K
authors.lastname: Kreissig
authors.affiliation: Department of Earth Science & Engineering, Imperial College London , SW7 2AZ London, U.K.
authors.forename: Mark
authors.initials: M
authors.lastname: Rehkämper
authors.affiliation: Institute of Geography and Geoecology, Karlsruhe Institute of Technology (KIT) , P.O. Box 6980, D-76049 Karlsruhe, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wilcke
authors.affiliation: Institute of Agricultural Sciences, ETH Zurich , Eschikon 33, CH-8315 Lindau, Switzerland.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Frossard
mesh_terms: D002104:Cadmium; D005591:Chemical Fractionation; D007554:Isotopes; D012987:Soil; D014908:Triticum
chemical_list: D007554:Isotopes; D012987:Soil; D002104:Cadmium