Temperature and soil pollution affect dissolved and colloidal antimony release from flooded shooting range soils

Area of Science:

• Environmental Science
• Geochemistry
• Soil Science

Background:

• Antimony (Sb) mobility in soils is a growing environmental concern, yet its behavior under changing climatic conditions is poorly understood.
• Shooting ranges are potential sources of soil contamination with antimony and lead (Pb).
• Microbial biomass significantly influences the geochemical processes affecting contaminant mobility.

Purpose of the Study:

• To investigate the effect of temperature on antimony (Sb) release from contaminated soils under flooded conditions.
• To assess the role of soil microbial biomass in mediating Sb release and mobility.
• To characterize the colloidal fraction of antimony in soil pore water.

Main Methods:

• A 28-day microcosm experiment using two shooting range soils with varying Sb, Pb, and microbial biomass levels.
• Sequential extractions and pore water analyses to quantify Sb release at 20°C and 25°C.
• Asymmetric flow field-flow fractionation (AF4) to determine Sb size distribution and characterize colloidal Sb.

Main Results:

• Elevated temperatures decreased Sb release in less contaminated soil with high microbial biomass, but increased release in highly contaminated soil with low microbial biomass.
• Microbial biomass played a critical role in mediating temperature-dependent Sb release, likely through redox transformations.
• A significant fraction (13-36%) of pore water Sb was present as colloids, with AF4 identifying organic/microcrystalline and mineral nanoparticle populations.

Conclusions:

• Soil microbial biomass is a key factor controlling antimony redox transformations and release under varying temperature conditions.
• Colloidal transport is an important pathway for antimony mobility in soils.
• Understanding these processes is crucial for assessing environmental risks associated with antimony contamination, especially under future climate scenarios.