『Abstract
The biogeochemical cycling and isotopic fractionation of calcium
during the initial stages of weathering were investigated in an
alpine soil chronosequence (Damma glacier, Switzerland). This
site has a homogeneous silicate lithology and minimal biological
impacts due to sparse vegetation cover. Calcium isotopic compositions,
obtained by TIMS using a 43Ca-46Ca double
spike, were measured in the main Ca pools. During this very early
stage of weathering, the young soils which have formed (δ44/42Ca
= +0.44‰) were indistinguishable to the rocks from which they
were derived (δ44/42Ca = +0.44‰) and stream water
(δ44/42Ca = +0.48‰) was also within error of the average
rock. This lack of variation indicates that the dissolution of
the bulk silicate rock does not strongly fractionate Ca isotopes.
The only Ca pool which was strongly fractionated from bulk rock
was vegetation, which exhibited an enrichment of light Ca isotopes.
Significant Ca isotope fractionation between bulk rock and the
dissolved flux of Ca is likely to only occur where the Ca biogeochemical
cycle is dominated by secondary processes such as biological cycling,
adsorption and secondary mineral precipitation.』
1. Introduction
2. Study area
3. sampling and analytical methods
3.1. Sample collection
3.2. Sample preparation
3.3. Mass spectrometry
3.4. Soil sequential extractions
4. Results
4.1. Rock, soil and mineral separates
4.2. Sequential extractions
4.3. Water samples
4.4. Plants
5. Discussion
5.1. Weathering in soils
5.2. Porewaters and the exchangeable pool
5.3. Stream water
6. Conclusions
Acknowledgement
Appendix A. Supplementary data
References