Investigations of tungsten mobility in soil using column tests

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Tungsten (W) exhibits complex environmental geochemistry, existing as soluble tungstate and polymeric species.
• Previous studies indicate high tungsten solubility in soils, influenced by co-occurring analytes like calcium and phosphate.

Purpose of the Study:

• Investigate tungsten compound mobility in a model soil using column experiments.
• Evaluate the impact of varying aqueous leach solutions on tungsten leaching.
• Analyze the influence of pH on tungsten speciation and mobility.

Main Methods:

• Column experiments with a model soil and diverse aqueous leach solutions.
• Measurement of tungsten concentrations in column leachates.
• Analysis of tungsten speciation (monomeric vs. polymeric) over time.

Main Results:

• Leachate tungsten concentrations varied significantly with pH.
• Neutral to alkaline conditions yielded high effluent tungsten concentrations (>40 mg/L).
• Acidic leach eluents resulted in low tungsten concentrations (<1-3 mg/L).
• Observed leachate trends align with previously reported tungstate and polytungstate partition coefficients.

Conclusions:

• Soil pH is a critical factor controlling tungsten mobility and leaching.
• Understanding tungsten speciation is essential for predicting its environmental fate.
• The study provides valuable data for environmental risk assessments involving tungsten.