Molybdenum Release Triggered by Dolomite Dissolution: Experimental Evidence and Conceptual Model

Area of Science:

• Environmental Science
• Geochemistry
• Hydrogeology

Background:

• Managed aquifer recharge (MAR) using oxygenated water can mobilize metal(loid)s in anoxic aquifers.
• Understanding metal(loid) mobilization during MAR is crucial for water resource management.

Purpose of the Study:

• To investigate the mechanisms controlling molybdenum (Mo) release in dolomitic aquifers during MAR.
• To develop a conceptual model for MAR-induced Mo mobilization.

Main Methods:

• Sequential chemical extractions to determine Mo association.
• Energy dispersive X-ray spectroscopy and scanning electron microscopy for mineralogical analysis.
• Batch experiments to assess Mo release kinetics and influencing factors.

Main Results:

• Molybdenum (Mo) is primarily associated with easily soluble sulfurized organic matter within dolomite.
• Batch experiments confirmed rapid mobilization of Mo, dissolved organic carbon, and sulfur.
• Increased shaking intensity in batch tests significantly enhanced Mo release by 36%.

Conclusions:

• MAR-induced Mo release is linked to pyrite oxidation and subsequent dolomite dissolution.
• Dissolution of dolomite enhances access to sulfurized organic matter, facilitating Mo mobilization.
• A conceptual model illustrates the process: oxygenated water injection -> pyrite oxidation -> proton release -> dolomite dissolution -> Mo release from organic matter.