Cadmium Reactivity in Metal-Contaminated Soils Using a Coupled Stable Isotope Dilution-Sequential Extraction Procedure

摘要: To better understand the intrinsic reactivity of Cd, four soils having diverse sources Cd contamination (total Cd: 22-34 mg kg(-1)) were investigated using a stable isotope dilution-sequential extraction procedure (SID-SEP) during 59-week incubation. Samples spiked with carrier-free 111Cd and periodically extracted into five operationally defined fractions; 111Cd:10Cd ratios measured by inductively coupled plasma-mass spectrometry. The total labile pool (E value) was calculated as well within each fraction. Results for three (Cd sources: natural, sewage sludge, smelter emissions) quite similar. overall %E after 2-week equilibration 35-49% soil Cd. Within fraction 2 (sorbed/carbonate), 70-75% isotopically labile, while 3 (oxidizable) only 35-41% weeks. fourth (reducible) fifth (residual) fractions dominated nonlabile Although all E values increased somewhat from to 59 weeks, none reached isotopic equilibrium soluble/exchangeable step 1. Because native in soils, contributed primarily (85-98%) these two fractions. A (mine spoil-contaminated) demonstrably different: just 13 and, although 82% present oxidizable fraction, 2% that labile. nonlability this could be ascribed predominance inorganic forms, most likely occluded sphalerite. No single SEP nor any combination showed good correspondence size pool. Our results suggest conventional SEPs may limited utility predicting bioavailability, example, ecological risk assessment.