Earthworm Enhanced Phytoremediation of U in Army Test Range Soil with Indian Mustard and Sunflower

Abstract

Wars and military testing have resulted in the depleted uranium (DU) contamination of military proving grounds. In the present study, a pot experiment was conducted to explore the effects of earthworms on the uranium phytoremediation process. Effects of cattle manure and Eisenia fetida on biomass and U accumulation of plants, U solubility, and pH in soil were investigated using DU-contaminated soil from Yuma Proving Ground in Arizona, U.S. Results showed that the growth of plants was promoted with the addition of cattle manure and earthworms, which was more obvious for sunflowers. Moreover, the U accumulation was significantly enhanced by earthworms and cattle manure, with a 68.5% (Indian mustard) and 85.0% (sunflower) increase in the cattle manure plus earthworm treatments, and the removal efficiencies of U were correspondingly improved. No significant effect on soil pH was observed, while the soil water extractable U was increased by 84.9–87.8% in the earthworm treatments. Moreover, after the 4-week cultivation, cattle manure benefited the survival of earthworms and slightly increased their average fresh weight in DU-contaminated soil. Therefore, this study concludes that earthworms combined with agricultural organic wastes was an alternative approach to effectively remediate DU-contaminated soils in firing ranges.