Manganese reductive dissolution coupled to Sb mobilization in contaminated shooting range soil

Area of Science:

• Environmental Science
• Geochemistry
• Microbiology

Background:

• Antimony (Sb) contamination in soils poses environmental risks.
• Understanding Sb mobilization mechanisms is crucial for remediation strategies.
• Manganese (Mn) oxyhydroxides are known to influence trace element fate.

Purpose of the Study:

• To investigate the impact of moderately reducing conditions on Sb, Mn, and Fe mobilization and speciation.
• To compare Sb mobilization in a redox-stat bioreactor (R_MnR) with a control bioreactor (R_CTRL).
• To identify key microbial players and geochemical factors influencing Sb release.

Main Methods:

• Utilized a "redox-stat" bioreactor to simulate controlled moderately reducing conditions (+420 mV).
• Compared elemental mobilization (Mn, Sb, Fe) and speciation (Sb(III)/Sb(V), Fe2+/Fe3+) with a control bioreactor.
• Employed multiple linear regression analysis and bacterial community composition analysis.

Main Results:

• Reducing conditions increased effluent Sb(V) and Mn(II), indicating Sb release linked to Mn oxyhydroxide reduction.
• Mn concentration significantly correlated with Sb effluent concentrations in R_MnR.
• Similar overall Sb release in R_MnR (10.40%) and R_CTRL (10.37%) suggested a subordinate role for anoxic processes like Fe-reductive dissolution.

Conclusions:

• Microbial reductive dissolution of Mn oxyhydroxides is a primary mechanism for Sb mobilization under moderately reducing soil conditions.
• Redox-stat bioreactors are effective tools for quantifying specific trace element mobilization mechanisms.
• Contaminated soils retain significant Sb mobilization potential even after aging, highlighting persistent environmental effects.