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| Synergistic remediation of Cr(Ⅵ)-contaminated soil by Stenotrophomonas sp., rice straw, and earthworms |
| Received:March 07, 2023 |
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| KeyWord:Cr;Stenotrophomonas sp.;rice straw;earthworm;soil aggregate |
| Author Name | Affiliation | E-mail | | SHEN Songrong | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | | | CHEN Yun | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | | | KANG Qianlin | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | | | XIANG Yuanling | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | | | GENG Yuhong | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | | | ZHANG Wei | Analysis and Test Center of Southwest University of Science and Technology, Mianyang 621010, China | | | HAN Ying | School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang 621010, China | 595749991@qq.com |
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| Abstract: |
| This study aimed to understand the remediation effect and mechanism of rice straw and earthworm combined with Cr-resistant bacteria on Cr bioavailability and its distribution in soil aggregates. This study explored the remediation effect of Stenotrophomonas sp.(F), rice straw(S), bacteria + rice straw (SF), rice straw + earthworm(Eisenia foetida,SE), and bacteria + rice straw + earthworms (SFE) under 50 mg·kg-1 and 300 mg·kg-1 Cr(Ⅵ)-contaminated soil, and changes in the bioavailability of Cr and the distribution of total Cr and Cr(Ⅵ) in soil aggregates through indoor analog experiment. The results showed that the total Cr and Cr(Ⅵ) removal rates of each treatment steadily increased in the early, middle, and late stages of the experiment. The total Cr and Cr(Ⅵ) removal rates of the SFE treatment were the highest in the later stages of 50 mg·kg-1 and 300 mg·kg-1 Cr(Ⅵ) exposure, with total Cr removal rates of 35.68% and 35.29%, respectively, while the removal rates of Cr(Ⅵ) were 99.28% and 75.33%, respectively. The SFE treatment significantly reduced soil reduction potential, increased soil pH and organic matter content, and promoted the aggregation of micro-aggregates into large aggregates. The proportion of large aggregates treated with SE was the highest, increasing by 14.57, 9.51, and 9.85 percentage points compared to the CK, and 3.73, 4.09, and 3.28 percentage points compared to the SFE, respectively, under 0, 50 mg·kg-1, and 300 mg·kg-1 Cr(Ⅵ) exposure. The influence of each treatment on the chemical form of chromium was as follows:SFE>SF>SE>S>F. Except for F, the proportion of various chemical forms of Cr in all other treatments steadily changed with the extension of the experimental time throughout the entire experimental process. Compared with the CK, in the SFE treatment after 50 mg·kg-1 and 300 mg·kg-1 Cr(Ⅵ) exposure, the proportion of the exchangeable state decreased by 35.55 percentage points and 21.02 percentage points, respectively, and the residual state increased by 22.45 percentage points and 12.51 percentage points, respectively. Total Cr was mainly distributed in large-aggregates, while Cr(Ⅵ) was mainly distributed in micro-aggregates, and the total Cr and Cr(Ⅵ) concentrations in aggregates of all particle sizes decreased with time. The SFE treatment significantly reduced the accumulation of total Cr and Cr(Ⅵ) in large and micro-aggregates. The results indicate that the synergistic treatment of rice straw, earthworm, and Stenotrophomonas sp. significantly increase the removal rates of total Cr and Cr(Ⅵ) in soil, reduce the proportion of bioavailable Cr, and improve the distribution of Cr in aggregates under exposure to 50 mg·kg-1 and 300 mg·kg-1 Cr(Ⅵ). |
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