Phyto- and Microbial-Based Remediation of Rare-Earth-Element-Polluted Soil

Rare-earth elements (REEs) are strategic resources that have been extensively utilized in industrial manufacturing, aerospace engineering, and defense technology. Beyond their technological applications, REEs have been demonstrated to enhance agricultural productivity through growth promotion mechanisms in various crops, leading to their recognition as valuable trace element fertilizers in modern farming practices. Consequently, REEs have been increasingly introduced into ecosystems, where they are continuously accumulated in soil and transmitted into food chains, resulting in REE pollution, which has become a significant environmental concern. However, the regulatory mechanisms controlling REE contamination are not well understood. In recent years, the environmental impacts of REEs have attracted increasing attention, especially in their pollution mitigation from industrial and agricultural REE emissions. Bioremediation is regarded as a promising method for contaminated soil treatment. The application of plants and microorganisms to REE-polluted environments has been explored as an emerging research field that combines the synergistic advantages of plant rhizospheric microorganisms and vegetation systems. The combination of phytoremediation and microbial remediation approaches has been shown to enhance soil health restoration, thereby improving the purification efficiency of REE-contaminated soil. This paper, citing 179 references, reviews the roles of plants, microorganisms, and plant-microbe interactions in REE-contaminated soil remediation, and summarizes the available practical methods with which to address REE pollution and the fundamental mechanisms involved.