Project 6

Tracing metal-CO2(aq)-solid interactions from deep sources to shallow aquifers

Lead partner: Amphos 21 Consulting SL, Spain
Marie Curie fellow: Marco Agnelli, Italy (ESR, PhD student)

The effects of dissolved CO2 on the mobility of some metals in aquifers is a first-order concern in the deployment of CO2 geological storage, since it can jeopartdize the quality of water resources. Up to now, research has been mainly focused on Fe(III) solubility in CO2-bearing fluids, and experimental results match observations in naturals systems where high Fe concentration can be found under oxic, circum-neutral solutions. The enhanced solubility of Fe(III) has an additional and unwanted side effect: the inhibition of the precipitation of Fe(OH)3 (am), which is a major sink for many trace and minor elements.

The aim of the project is to constrain the behaviour of metals and metalloids that are mobilised by CO2-bearing groundwaters by identifying the isotopic fractionations caused during incorporation in precipitating phases, and so quantify this process from groundwaters measurements.

Data from natural systems in NE and central Spain on stable U, Cu, Cr, and Fe isotopes will be compared to experimental weathering and precipitation data on fractionation into Fe phases under various conditions to predict behaviour in different environments.