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
(Â65Cu). 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 Â65Cu
values in bulk soil. Cu concentrations in the studied soils were
low (1.4-27.6Ęg g-1) and Cu was mainly associated with
strongly bound Fe oxide- and silicate-associated forms. Bulk Â65Cu
values varied between -0.57ń and 0.44ń in all studied horizons.
The O horizons had on average significantly lighter Cu isotope
compositions (-0.21ń) than the A horizons (0.13ń) 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 Â65Cu values with depth was visible in all
four profiles. This is the opposite depth distribution of Â65Cu
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), Â65Cu 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
(2.8Ęg g-1) and a higher Â65Cu value (-0.18ń)
than oxide-rich sections (1.9Ęg g-1, -0.35ń) 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 Â65Cu
values in Haplic Podzol 1 indicate a promising potential of Â65Cu
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