T2. Geochemistry and transfer of water and contaminants in the environment

The object of this theme is the reconstruction, using geochemical methods, of flows of water and of particulate or dissolved constituents, both within various environmental compartments (soils, surface water, groundwater, etc.) and between compartments. It seeks to evaluate the chemical quality of solutions and solids, to trace the origins of this quality by identifying the sources, and, finally, to evaluate the dynamics by using indicators of residence-, transit and renewal times.

Sub-themes and associated methods

The approach is based on three complementary aspects:

T2.1 Chemical quality of solutions and solids

Chemical quality of solutions (including the particulate phase) and solids (e.g. soils, sediments), which allow us to reveal the potential presence of contaminants in the broadest sense since we may be dealing with compounds that are toxic at low doses for humans and/or the environment (e.g. certain metals) or compounds that become problematic at high concentrations (e.g. water potability criteria: practically all elements are concerned).
[Chemical analyses of major-, minor- and trace elements]

T2.2 Tracing the origin of water and elements/compounds in continental hydrosystems.

This is carried out by comparing their geochemical and isotopic signatures with those of potential sources. This step allows us to construct a conceptual model of the transfers and to quantify exchanges between the different reservoirs present in the system under investigation.
[Chemical analyses of major-, minor- and trace elements] [ Isotopic analysis of O, H, C, He, Sr, B, metal] [¹⁴C ]

T2.3 Quantification of the dynamics of continental hydrosystems.

This is carried out by establishing time constraints that can be obtained from geochemical and isotopic records and by measuring the concentrations of radioactive- (decay) and radiogenic- (accumulation) elements, as well as the concentration of elements whose introduction chronology in the system is known (anthropogenic). Clearly this temporal information is invaluable for identifying the impacts (quantitative and qualitative) of climate change and human activity on resources (water, soils) and for evaluating current and future vulnerability of these resources.
[Measurement of ³H, ³He, ⁴He, CFCs, and SF6]; [¹⁴C]