LAUSR

Addition of manganese (IV)-oxides (MnO2 ) and zeolite can affect mobility of As and V in soils due to geochemical changes which have not been studied well in calcareous, flooded soils. This study evaluated the mobility of As and V in flooded soils surface-amended with MnO2 or zeolite. A simulated summer flooding study was conducted for eight weeks using intact soil columns from four calcareous soils. Redox potential was measured in soils while pH, major cations, As and V concentrations were measured bi-weekly in pore water and floodwater. Aqueous As and V species were modeled at 0, 4, and 8 weeks after flooding (WAF) using Visual MINTEQ modeling software with input parameters of redox potential, temperature, pH, total alkalinity and concentrations of major cations and anions. Aqueous As concentrations were below the critical thresholds (< 100 μg L-1 ) while aqueous V concentrations exceeded the threshold for sensitive aquatic species (2 to 80 μg L-1 ). MnO2 -amended soils were reduced to sub-oxic levels while zeolite-amended and unamended soils were reduced to anoxic levels by 8 WAF. MnO2 decreased As and V mobility while zeolite had no effect on As but increased V mobility, compared to unamended soils. Arsenic mobility increased under anoxic conditions, and V mobility increased under oxic and alkaline pH conditions. Conversion of As(V) to As(III) and V(V) to V(IV) was regulated by MnO2 in flooded soils. MnO2 can be used as an amendment in immobilizing As and V while use of zeolite in flooded calcareous soils should be done cautiously. This article is protected by copyright. All rights reserved.