In a field experiment we investigated the efficiency of two hyperaccumulating species, four agricultural crop plants, and one woody crop, at phytoextraction of Zn, Cd, and Cu from a polluted calcareous soil. In addition, we examined the possibility to enhance the phytoextraction of these metals by application of nitrilotriacetate (NTA) and elemental sulfur (S 8 ) to the soil. Metal uptake by hyperaccumulating species was higher than that by crop species but was generally low in all treatments compared to results reported in the literature, maybe as a result of lower total and available soil metal concentrations. Soil amended with either S 8 or NTA increased the solubility (NaNO 3 -extraction) of Zn, Cd, and Cu ions by factors of 21, 58, and 9, respectively, but plant accumulation of these metals was only increased by a factor of 2-3. As a result, even the highest metal removal rates achieved in this study were still far from what would be required to make this technique practicable for the remediation of the Dornach field site. To extract for example 50% of the total Cu, Zn, or Cd present in this soil within 10 years, plant metal concentrations of 10.000 mg kg -1 Cu or 10.000 mg kg -1 Zn or 45 mg kg -1 Cd would be required at a biomass production of 7.8 t ha -1 , or 10t ha -1 , or 10t ha -1 , respectively, assuming a linear decrease in soil metals.

18Analyses of stable metal isotope ratios constitute a novel tool to improve understanding of 19 biogeochemical processes in soil-plant systems. In this study, we used such measurements 20 to assess Cd uptake and transport in wheat grown on three agricultural soils under 21 controlled conditions. Isotope ratios of Cd were determined in the bulk C and A horizons, in 22 the Ca(NO 3 ) 2 extractable Cd soil pool and in roots, straw and grains. The Ca(NO 3 ) 2 23 extractable Cd was isotopically heavier than the Cd in the bulk A horizon (Δ

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The application of mineral phosphate (P) fertilizers leads to an unintended Cd input into agricultural systems, which might affect soil fertility and quality of crops. The Cd fluxes at three arable sites in Switzerland were determined by a detailed analysis of all inputs (atmospheric deposition, mineral P fertilizers, manure, and weathering) and outputs (seepage water, wheat and barley harvest) during one hydrological year. The most important inputs were mineral P fertilizers (0.49 to 0.57 g Cd ha yr) and manure (0.20 to 0.91 g Cd ha yr). Mass balances revealed net Cd losses for cultivation of wheat (-0.01 to -0.49 g Cd ha yr) but net accumulations for that of barley (+0.18 to +0.71 g Cd ha yr). To trace Cd sources and redistribution processes in the soils, we used natural variations in the Cd stable isotope compositions. Cadmium in seepage water (δCd = 0.39 to 0.79‰) and plant harvest (0.27 to 0.94‰) was isotopically heavier than in soil (-0.21 to 0.14‰). Consequently, parent material weathering shifted bulk soil isotope compositions to lighter signals following a Rayleigh fractionation process (ε ≈ 0.16). Furthermore, soil-plant cycling extracted isotopically heavy Cd from the subsoil and moved it to the topsoil. These long-term processes and not anthropogenic inputs determined the Cd distribution in our soils.