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| Morphological transformation and migration of chromium in horizontal subsurface flow and vertical flow constructed wetlands |
| Received:December 06, 2022 Revised:March 09, 2023 |
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| KeyWord:constructed wetlands;Coix lacryma-jobi L.;chromium;chromium chemical speciation;soil enzymes;dissolved organic matter |
| Author Name | Affiliation | E-mail | | WU Zhenhua | College of Agriculture, Guangxi University, Nanning 530004, China | | | LI Liangxiang | College of Agriculture, Guangxi University, Nanning 530004, China | | | LI Suli | College of Agriculture, Guangxi University, Nanning 530004, China | | | CHENG Xiran | College of Agriculture, Guangxi University, Nanning 530004, China | | | WANG Xueli | College of Agriculture, Guangxi University, Nanning 530004, China | | | LI Zhengwen | College of Agriculture, Guangxi University, Nanning 530004, China | | | LI Zhigang | College of Agriculture, Guangxi University, Nanning 530004, China | lizhigangnn@163.com |
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| Abstract: |
| In this study, a small vertical flow-constructed wetland(VC) and a horizontal subsurface flow-constructed wetland(HC)were constructed with Coix lacryma-jobi L. as a wetland plant. The effects of different water management techniques on the migration and transformation of chromium in Cr6+ wastewater were investigated. The results revealed that:Under Cr6+ treatment, the growth of Coix lacryma-jobi L. in the two wetlands was inhibited, and the growth of Coix lacryma-jobi L. in horizontal subsurface flow-constructed wetland was less inhibited than that in vertical flow-constructed wetland. The content of chromium in the horizontal subsurface flowconstructed wetland was higher, whereas the content of exchangeable and carbonate-extractable chromium in the vertical flow-constructed wetland was higher. The pH value and Eh of the substrate decreased as Cr6+ concentration increased. The pH and Eh values of vertical flowconstructed wetlands were higher than those of horizontal subsurface flow-constructed wetlands. Compared with the enzyme activities related to the subsurface flow-constructed wetland, vertical flow-constructed wetland could increase the sucrase activity in the substrate; however, the urease activity under Cr6+ treatment was lower than that in the horizontal subsurface flow-constructed wetland. Highthroughput analysis demonstrated significant differences in microbial communities between the two constructed wetlands under different treatments. Horizontal subsurface flow-constructed wetland microorganisms were more conducive to converting chromium into difficult-touse chromium forms. Horizontal subsurface flow-constructed wetland is more effective at removing Cr6+ from wastewater. The results demonstrated that the horizontal subsurface flow-constructed wetland was beneficial in promoting Cr6+ transformation into chromium form, which was challenging to use, and improved the removal ability of Cr6+ in wastewater. |
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