A critical review of uranium in the soil-plant system: Distribution, bioavailability, toxicity, and bioremediation strategies

Increasing uranium (U) content in soils due to anthropogenic U contamination causes accumulation of U in plants, which greatly increases human health risks. This review identified the diverse sources of soil U contamination and their significant spatial variations in surface soils globally based on 789 soil sampling sites collected from 76 studies. The relationships between U biogeochemical transformation and its bioavailability in soil are significantly affected by soil redox potential, pH, metal (hydr)oxides, organic matter, and microorganisms. The toxicity/detoxification mechanisms of U in plants and microorganisms have been extensively studied, and further studies should combine with omics techniques (proteomics, genomics, and metabolomics) to narrow the knowledge gaps in molecular mechanisms. Moreover, the mechanisms and applicability of phytoremediation and microbial bioremediation in U-contaminated soils were summarized. Based on the present review, we further propose several critical challenges and directions for improving our knowledge and remediation strategies of U contamination in the soil-plant system. This review would help us better understand the geochemical behavior of U in soil-plant systems and its potential risks to human health.