In this study, the sorption of U(VI) on the farming soil (FS) and natural soil (NS) collected from northwest China was studied using batch and spectroscopic approaches. The sorption of U(VI) on NS, FS, decarbonated NS (DNS) and decarbonated FS (DFS) quickly increased with the pH increased. After removing carbonates, U(VI) sorption on DFS and DNS became slightly lower. The exchangeable fraction was the highest in NS, FS, DNS, and DFS. However, it was noted that the carbonate fraction took up 13–17% in FS and NS, suggesting that carbonate has an essential impact on the species distribution. [ABSTRACT FROM AUTHOR]