『Abstract
　Geochemistry of soil, soil water, and soil gas was characterized in representative soil profiles of three Michigan watersheds. Because of differences in source regions, parent materials in the Upper Peninsula of Michigan (the Tahquamenon watershed) contain only silicates, while those in the Lower Peninsula (the Cheboygan and the Huron watersheds) have significant mixtures of silicate and carbonate minerals. These differences in soil mineralogy and climate conditions permit us to examine controls on carbonate and silicate mineral weathering rates and to better define the importance of silicate versus carbonate dissolution in the early stage of soil-water cation acquisition.
　Soil waters of the Tahquamenon watershed are the most dilute; solutes reflect amphibole and plagioclase dissolution along with significant contributions from atmospheric precipitation sources. Soil waters in the Cheboygan and the Huron watersheds begin their evolution as relatively dilute solutions dominated by silicate weathering in shallow carbonate-free soil horizons. Here, silicate dissolution is rapid and reaction rates dominantly are controlled by mineral abundances. In the deeper soil horizons, silicate dissolution slows down and soil-water chemistry is dominated by calcite and dolomite weathering, where solutions reach equilibrium with carbonate minerals within the soil profile. Thus, carbonate weathering intensities predominantly controlled by annual precipitation, temperature and soil pCO2. Results of a conceptual model support these field observations, implying that dolomite and calcite are dissolving at a similar rate, and further dissolution of more soluble dolomite after calcite equilibrium produces higher dissolved inorganic carbon concentrations and a Mg²⁺/Ca²⁺ ratio of 0.4.
　Mass balance calculations show that overall, silicate minerals and atmospheric inputs generally contribute ＜10％ of Ca²⁺ and Mg²⁺ in natural waters. Dolomite dissolution appears to be a major process, rivaling calcite dissolution as a control on divalent cation and inorganic carbon contents of soil waters. Furthermore, the fraction of Mg²⁺ derived from silicate mineral weathering is much smaller than most of the values previously estimated from riverine chemistry.』

1. Introduction
2. Field site description and methodology
　2.1. Study site characterization
　2.2. Soil sampling and characterization
　2.3. Soil water sampling and characterization
　2.4. Soil CO2 sampling and analyses
　2.5. Aqueous speciation calculations
3. Results
　3.1. Soil geochemistry
　　3.1.1. Soil acid leachates and total LiBO2 digests
　　3.1.2. Cation exchange capacity (CEC)
　　3.1.3. Soil mineralogy and carbon contents
　3.2. Soil water and soil gas geochemistry
4. Discussion
　4.1. Chemical weathering of silicate minerals
　4.2. Equilibrium controls on carbonate mineral dissolution
　4.3. Modeling dolomite versus calcite weathering
　4.4. Mass balance assessment of silicate versus carbonate weathering contributions
　4.5. Significance of dolomite weathering contributions
5. Conclusions
Acknowledgment
Appendix A. Supplementary data
References