Isotopic variation of dissolved and colloidal iron and copper in a carbonatic floodplain soil after experimental flooding

摘要: Many floodplain soils worldwide are contaminated by present and past industrial mining activities. During flooding redox potential decreases, triggering the release of dissolved colloidal metals. We used an anaerobic microcosm incubation to simulate a carbonate-rich soil for 40 days. Soil solution samples were extracted determine (< 0.02 μm) fractions (0.02–10 μm). analyzed stable isotope ratios Fe Cu representing two groups metals with different behavior; was steadily increasing, while that peaked sharply after decreased afterwards. The temporal trend δ56Fe values total in indicated dissimilatory iron reduction. apparent isotopic fractionation between (Δ56Fedissolved-colloidal = δ56Fedissolved − δ56Fecolloidal) varied from 0.31 ± 0.04‰ 1.86 0.26‰. Low δ56Fecolloidal (− 1.16 0.04‰) on day 4 experiment suggested colloid formation precipitation Fe, strong variation Δ56Fedissolved-colloidal subsequent changes mineralogy, sorption components and/or electron transfer-atom exchange. variations δ65Cu (Δ65Cudissolved-colloidal 0.81 0.03‰ 1.58 0.09‰) probably linked changing oxidation state Cu. While at beginning solid exchange, these systems decouple onset sulfate reduction second half experiment. experimental results fit well findings redoximorphic described literature highlight importance colloids metal pattern carbonatic soils.