『Abstract
　The geochemistry of dissolved and suspended loads in river catchments of two low mountain ranges in Central Europe allows comparison of pertinent chemical weathering rates. Distinct differences in lithology, i.e. granites prevailing in the Black Forest compared to Palaeozoic sediments in the Rhenish Massif, provide the possibility to examine the influence of lithology on weathering. Here we determine the origin of river water using the stable isotope ratio δ¹⁸OH2O and we quantify the geogenic proportions of sulphate from stable isotope ratios δ³⁴SSO4 and δ¹⁸OSO4. Particularly in catchments with abundant pyrite, determination of the geogenic amount of sulphate is important, since oxidation of pyrite leads to acidity, which increases weathering. Our results show that spatially averaged silicate weathering rates are higher for the river catchments Acher and Gutach in the Black Forest (10-12 t/km²/yr) compared to the river catchments of the Mohne（oの頭に¨） dam and the Aabach dam in the Rheinish Massif (2-6 t/km²/yr). Correspondingly, the CO2 consumption by silicate weathering in the Black Forest (334-395×10³ mol/km²/yr) is more than twice as high as in the Rheinish Massif (28-151×10³ mol/km²/yr). These higher rates for watersheds for the Black Forest are likely due to steeper slopes leading to higher mechanical erosion with respective higher amounts of fresh unweathered rock particulates and due to the fact that the sediments in the Rheinish Massif have already passed through at least one erosion cycle. Carbonate weathering rates vary between 12 and 38 t/km²/yr in the catchments of the Rheinish Massif. The contribution of sulphuric acid to the silicate weathering is higher in the catchments of the Rheinish Massif (9-16％) than in the catchments of the Black Forest (5-7％) due to abundant pyrite in the sediments of the Rheinish Massif. Three times higher long-term erosion rates derived from cosmogenic nuclides compared to short-term erosion rates derived from river loads in Central Europe point to three times higher CO2 consumption during the past 10³ to 10⁴ years.

Keywords: Silicate weathering; Carbonate weathering; Sulphur isotopes; Oxygen isotopes; Suspended load; Erosion』

1. Introduction
2. Description of catchment areas
3. Methods
4. Results
　4.1. Sources of river waters
　4.2. Downriver evolution of ion concentrations
　4.3. Sulphur sources
5. Discussion
　5.1. Mobility of major cations during weathering
　5.2. Weathering rates and respective CO2 consumption
6. Conclusions
Acknowledgements
Appendix A. Supplementary data
References