Cadmium (Cd) speciation changes in non-contaminated soils: Is Cd isotope composition a tracer of Cd speciation change

Cadmium in agricultural soils is a matter of increasing concern, for food safety reasons. While some Cd is anthropogenic – mostly added with fertilisers – soils also contain geogenic Cd. To decipher the combined impact of Cd from fertilisers and soils, it is essential to better understand the fate of geogenic Cd from the bedrock to the soil profiles. The aim of the proposal is to understand the speciation of Cd in soil horizons from different soil types, previously characterized. We selected 3 soil types of agricultural significance (Cambisol) and wide occurrence and/or biogeochemically contrasted (Regosol, Podzol), developed on various bedrocks (granitic, versus calcareous), with various Cd content. The overarching goal is to explore the possible relation between the evolution of Cd speciation from bedrock to upper soil horizons with the Cd isotope signature and decipher the possibility to develop a new indirect tracer of Cd speciation in the critical zone.