Lead, zinc, and copper redistributions in soils along a deposition gradient from emissions of a Pb-Ag smelter decommissioned 100 years ago.

Sourcing and understanding the fate of anthropogenic metals in a historical contamination context is challenging. Here we combined elemental and isotopic (Pb, Zn, Cu) analyses with X-ray Absorption Spectroscopy (XAS) measurements (Zn) to trace the fate, in undisturbed soil profiles, of historical metal contamination emitted by a 167-year-old Pb-Ag smelter decommissioned 100 years ago located in the Calanques National Park (Marseilles, France). Lead isotopic measurements show that entire soil profiles were affected by 74 years of Pb emissions up to ~7 km from the smelter under the main NNW wind, and indicate particulate transfer down to 0.

Atmosphere-soil carbon transfer as a function of soil depth.

The exchange of carbon between soil organic carbon (SOC) and the atmosphere affects the climate and-because of the importance of organic matter to soil fertility-agricultural productivity. The dynamics of topsoil carbon has been relatively well quantified, but half of the soil carbon is located in deeper soil layers (below 30 centimetres), and many questions remain regarding the exchange of this deep carbon with the atmosphere. This knowledge gap restricts soil carbon management policies and limits global carbon models.

Tracing contamination sources in soils with Cu and Zn isotopic ratios.

Copper (Cu) and zinc (Zn) are naturally present and ubiquitous in soils and are important micronutrients. Human activities contribute to the input of these metals to soils in different chemical forms, which can sometimes reach a toxic level for soil organisms and plants. Isotopic signatures could be used to trace sources of anthropogenic Cu and Zn pollution.