Mineralogical controls on arsenite adsorption onto soils: Batch experiments and model-based quantification.

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Arsenic accumulation in agricultural soils presents a human health risk, influenced by its adsorption onto soil minerals.
• Understanding arsenic adsorption is crucial for predicting its long-term fate and transport in soil ecosystems.

Purpose of the Study:

• Quantify the adsorption capacities of different soil minerals for As(III).
• Predict As(III) adsorption isotherms in bulk soils from the Datong Basin.
• Identify the specific mineral contributions to overall As(III) adsorption.

Main Methods:

• Linear programming calculations to determine mineral adsorption contributions.
• Sequential chemical extractions to characterize iron speciation (Fe_Si).
• Surface complexation modeling to predict As(III) adsorption isotherms.

Main Results:

• Fe-bearing minerals, illite, dolomite, and soil organic matter contribute significantly to As(III) adsorption.
• A substantial portion of soil iron (90.1%) is associated with silicates (Fe_Si), which do not adsorb As(III).
• Surface complexation models accurately predict As(III) adsorption for aeolian and riverine soils but underestimate it for lacustrine soils.

Conclusions:

• Fe-bearing minerals and non-Fe minerals play vital roles in As(III) adsorption.
• Significant differences exist in the As(III) adsorption capacities among various soil minerals.
• Accurate reactive transport models for As(III) require comprehensive consideration of diverse soil mineralogical factors.