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Water acquires its hydrochemical signature during its underground travel

Groundwater travels through rocks which all have their own geological history. This geological history leads to a different chemical signature of rocks according to the environment where they were formed. Two limestone rocks can thus have a different chemical signature in trace elements (Sr, Ba, Li...) depending on the depth and temperature of the sea when they were deposited. The water that circulates into a specific limestone will be marked by its chemical signature. Consequently each water mass has its own hydrochemical signature.

identifying hydrogeologic reservoirs and their contribution

Identification of hydrochemical signatures of the various water masses makes it possible to understand the relationships between groundwater and streams. The concentration of the suitable tracer (isotope or trace element) gives the amount of each water mass contribution.

Each pollutant also has its hydrochemical signature

The hydrochemical signature identification of a polluted groundwater could help estimating its origin by comparing signatures of the different potential sources.
The isotopic analysis allows going back to the origin of some pollutants like nitrates. In this case mineral nitrogen (linked to agricultural practices) has a different isotopic signature from the organic one (effluent sewage plants).