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We studied the speciation of arsenic and antimony in the rhizosphere of 6 pioneer plants grown in zinc smelting slag to understand the main affecting factors of phytoremediation. Compared with the control slag, the pH of rhizosphere decreased significantly (p < 0.05) and the DOC content increased significantly (p < 0.05). Overall, the contents of arsenic (except Photinia serrulata and Lolium perenne) and antimony in the rhizosphere were lower than those of control slag. The proportions of residual arsenic and antimony in the rhizosphere were the highest and significantly higher than control slag. Exchangeable state, aluminum-bound state and calcium-bound state were lower than control slag. The contents of arsenic and antimony in plants were normal and followed the order of roots > leaves > stems. Arsenic and antimony were significantly positively correlated with Free iron and aluminum oxides and negatively correlated with DOC. After 7 years of phytoremediation, the content and bioavailability of arsenic and antimony in the rhizosphere were significantly reduced and have a normal contents in plants. It is speculated that phytoremediation increases the migration of arsenic and antimony to the surrounding area, and Photinia serrulata and Lolium perenne exhibited the best performance on stabilise arsenic in slag. [ABSTRACT FROM AUTHOR]