Application of mixotrophic acidophiles for the bioremediation of cadmium-contaminated soils elevates cadmium removal, soil nutrient availability, and rice growth

Abstract

A major challenge in radically alleviating the threats posed by Cd-contaminated paddy fields to human health is to reduce the Cd levels in both soils and rice grains. In this study, the microbial extraction (ME) treatment using a mixotrophic acidophilic consortium was used for the bioremediation of Cd-contaminated soils. The results showed that the ME treatment enhanced the total Cd (40%) and diethylenetriamine pentaacetic acid-soluble Cd (DTPA-Cd, 64%) removal efficiencies in contaminated soils. In addition, ME treatment decreased the levels of Cd acid-soluble and reducible fractions and thereby reduced Cd uptake in rice tissues. Microbial community analysis indicated that the indigenous soil microbial diversity and composition were not changed after the ME treatment, but the relative abundance of functional microbes associated with Cd removal was improved. Notably, soil available nutrient levels were elevated upon inoculation with mixotrophic acidophiles, resulting in an increase in rice growth and grain weight. This study provides a scientific basis for the potential application and evaluation of ME treatment in the field for remediating Cd-contaminated paddy soils.