Underlying lithology controls trace metal mobilization during redox fluctuations
E K King1, A Thompson2, J C Pett-Ridge3
1College of Earth, Ocean, and Atmospheric Sciences, Oregon State University, Corvallis, OR 97331, United States of America.
The Science of the Total Environment
|March 22, 2019
Summary
Soil lithology, not just redox fluctuations, controls trace metal mobility. Different bedrock types influence soil properties, impacting how metals like aluminum and iron move, even in weathered soils.
Area of Science:
- Environmental Science
- Soil Science
- Geochemistry
Background:
- Redox state fluctuations are key drivers of trace metal mobilization in soils.
- Underlying lithology can influence soil properties, potentially modulating the impact of redox changes on metal mobility.
Purpose of the Study:
- To investigate the interplay between trace metal behavior, soil lithology, and redox state.
- To determine how contrasting lithologies affect trace metal mobilization under fluctuating redox conditions.
Main Methods:
- Surface soils from two distinct lithologies underwent consecutive 8-day redox cycles.
- Quantified trace metals (e.g., Al, Mn, Fe, REEs, Pb, U) in aqueous and colloidal phases of soil slurries.
- Utilized Mössbauer spectroscopy to characterize iron (oxyhydr)oxide phases.
Main Results:
- In volcaniclastic-derived soils (high clay, abundant short-range-ordered Fe phases), redox events and colloids drove metal mobilization.
- In granite-derived soils (lower clay, fewer short-range-ordered Fe phases), overall mobilization was lower and not redox-dependent.
- Molybdenum isotopes showed no redox-dependent behavior.
Conclusions:
- Lithology is a dominant factor controlling trace metal mobility in soils, overriding redox effects.
- Soil properties, influenced by parent material, dictate metal behavior even after significant weathering.
- Understanding lithology is crucial for predicting trace metal behavior in diverse soil environments.
Keywords:
Critical zoneLithologyMolybdenum isotopesRedox biogeochemistrySoil formationTrace metal mobilizationMore Related Videos
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