Colloid-facilitated Pb transport in two shooting-range soils in Florida

Area of Science:

• Environmental Science
• Soil Science
• Geochemistry

Background:

• Shooting range soils often contain elevated lead (Pb) levels, posing environmental risks.
• Florida's sandy soils, high rainfall, and shallow groundwater exacerbate Pb migration concerns.

Purpose of the Study:

• To investigate colloid-facilitated Pb transport in two distinct Florida shooting range soils.
• To understand the impact of soil properties on Pb mobility.

Main Methods:

• Utilized large intact soil columns to simulate Pb and colloid mobilization.
• Applied simulated rainwater (SRW) under varying ionic strengths and flow rates.
• Analyzed Pb association with different colloid size fractions.

Main Results:

• Colloids were the primary drivers of Pb transport in both soil types, showing a strong correlation with Pb in leachates.
• Reduced ionic strength and increased flow rates enhanced colloid and Pb release.
• In low organic carbon soils, 87% of Pb was in coarse colloids; in high organic carbon soils, 66% was in nano-sized colloids.

Conclusions:

• Colloids are critical facilitators of Pb transport in shooting range soils.
• Soil physicochemical properties significantly influence the mechanisms and extent of Pb migration.
• Understanding colloid-Pb interactions is essential for managing Pb contamination in vulnerable environments.