『Abstract
　This study investigates U-series, Sr isotopes, major and trace elements in a chalk aquifer system located in eastern France. Soil and rock samples were collected along depth profiles down to 45 m in four localities as an attempt to investigate the weathering processes in the soil, the unsaturated zone and the saturated zone of the aquifer. Interstitial water was extracted from soils and rocks by a centrifugation technique. U-series offer a powerful tool to calculate weathering rates because the relative mobility of the U- and Th-isotopes can be precisely measured and it does not require the determination of a reference state as in other approaches. As expected, the data show very large mobile element depletion in the soil with large ²³⁰Th excess relative to ²³⁸U, while the rocks show more limited but not insignificant mobile element depletion. The U-series data have been used to constrain weathering rates based on a 1-D reactive transport model. Weathering rates in the near surface are about 10-100 times faster than at depth. However, when integrated over the depth of the cores, including the unsaturated and the saturated zones, this underground weathering represents more than 30％ of the total weathering flux, assuming congruent dissolution of carbonates. The (²³⁴U²³⁸U) ratios in interstitial water are consistent with solid samples showing ²³⁴U depletion near the surface and an excess ²³⁴U at depth. A leaching experiment performed on chalk shows that the excess ²³⁴U in natural waters percolating through carbonate rocks results both from preferential ²³⁴U leaching and direct recoil in the interstitial water. A new approach was used to derive the recoil ejection factor based on BET measurements and the fractal dimension of chalk surface. Consideration of preferential leaching and recoil allows a more accurate modeling of weathering rates.

Keywords: Weathering; Chalk; U-series; Uranium; Groundwater』

1. Introduction
2. Description of field area and sampling
3. Analytical methods
4. Results
5. Results of dissolution experiment
6. Modeling approach
7. Discussion
　7.1. Weathering rates in the soils and in the chalk
　7.2. Weathering signatures in the interstitial waters
　7.3. Role of carbonate reprecipitation in the saturated zone
　7.4. Mass balance of uranium in surface waters
8. Summary and conclusions
Acknowledgements
Appendix A. Supplementary data
References