Bigalke,M., Weyer,S. and Wilcke,W.(2011): Stable Cu isotope fractionation in soils during oxic weathering and podzolization. Geochimica et Cosmochimica Acta, 75, 3119-3134.

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wAbstract
@Copper stable isotope ratios are fractionated during various biogeochemical processes and may trace the fate of Cu during long-term pedogenetic processes. We assessed the effects of oxic weathering (formation of Cambisols) and podzolization on Cu isotope ratios (ƒÂ65Cu). Two Cambisols (oxic weathered soils without strong vertical translocations of soil constituents) and two Podzols (soils showing vertical translocation of organic matter, Fe and Al) were analyzed for Cu concentrations, partitioning of Cu in seven fractions of a sequential extraction and ƒÂ65Cu values in bulk soil. Cu concentrations in the studied soils were low (1.4-27.6ƒĘg g-1) and Cu was mainly associated with strongly bound Fe oxide- and silicate-associated forms. Bulk ƒÂ65Cu values varied between -0.57ń and 0.44ń in all studied horizons. The O horizons had on average significantly lighter Cu isotope compositions (-0.21ń) than the A horizons (0.13ń) which can either be explained by Cu isotope fractionation during cycling through the plants or deposition of isotopically light Cu from the atmosphere. Oxic weathering without pronounced podzolization in both Cambisols and a weakly developed Podzol (Haplic Podzol 2) caused no significant isotope fractionation in the single profiles, while a slight tendency to lower ƒÂ65Cu values with depth was visible in all four profiles. This is the opposite depth distribution of ƒÂ65Cu values to that we observed in hydromorphic soils (soils which show indication of redox changes because of the influence of water saturation) in a previous study. In a more pronounced Podzol (Haplic Podzol 1), ƒÂ65Cu values and Cu concentrations decreased from Ah to E horizons and increased again deeper in the soil. Humus-rich sections of the Bhs horizon had higher Cu concentrations (2.8ƒĘg g-1) and a higher ƒÂ65Cu value (-0.18ń) than oxide-rich sections (1.9ƒĘg g-1, -0.35ń) suggesting Cu translocation between E and B horizons as organo-Cu complexes. The different depth distributions in oxic weathered and hydromorphic soils and the pronounced vertical differences of ƒÂ65Cu values in Haplic Podzol 1 indicate a promising potential of ƒÂ65Cu values to improve our knowledge of the fate of Cu during long-term pedogenetic processes.x

1 Introduction
2. Materials and methods
@2.1. Study soils
@2.2. Sampling and sample preparation
@2.3. Copper isotope measurements
@2.4. Calculations and statistical evaluation
3 Results
4. Discussion
@4.1. Copper isotope ratios in the organic layers
@4.2. Copper concentrations and isotope ratios in the Cambisols and Haplic Podzol 2
@4.3. Copper concentrations and isotope ratios in the Haplic Podzol 1
@4.4. Comparison of Cu isotope pattern in Cambisols, Podzols, and hydromorphic soils
5. Conclusion
Acknowledgments
References


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