Electrokinetic-assisted Phytoremediation of Soil Cadmium Pollution in Paddy Fields under Polarity Exchange Technology
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    Abstract:

    The feasibility of electrokineticassisted phytoremediation (EKPR) with polarity reversal to remove cadmium (Cd) contaminants from paddy soils under controlled irrigation was investigated. The experiments were carried out in cuboid pots powered by solar energy. The rice crops were planted near the electrodes under controlled irrigation, and the Scirpus tabernaemontani was planted as hyperaccumulator between two rows of rice plants. The results showed that H+ and OH-produced by electrolysis reactions could be directly neutralized by the polarity reversal operation, thus effectively avoiding the polarization of soil pH value. The soil current was varied from 0.08A to 0.36A, indicating that polarity exchange and high soil water content effectively ensured the number and mobility of free-moving ions in soils, which could drive heavy metal migration. Compared with CK treatment, EKPR treatment significantly increased the root dry biomass of Scirpus tabernaemontani by 34.93%. EKPR treatment significantly reduced the root and brown rice dry biomasses by 17.21%~30.16% and 16.18%~22.28% respectively, while significantly increased the leaf and stem dry biomasses by 3.82%~13.17% and 7.59%~30.91%, respectively. EKPR treatment increased the Cd content in root and ground parts by 15.49%~22.45% and 33.30%~35.45%, respectively. The content of Cd in rice root and brown rice was decreased by 14.48%~35.06% and 39.04%~57.43%, respectively. The electrokineticassisted phytoremediation technology could increase the Cd enrichment of Scirpus tabernaemontani and decrease the Cd enrichment of rice crops. Compared with CK treatment, the bioenrichment of Cd in Scirpus tabernaemontani under EKPR treatment was significantly increased by 46.48%, and that in rice crops was significantly decreased by 24.75%. At the end of EKR experiments, the soil Cd content near rice roots was decreased by 16.33%~19.14%.The results showed that under controlled irrigation, the electrokineticassisted phytoremediation with polarity reversal was a feasible method for cadmium contaminants in paddy soils. It had a good application prospect and practical significance to use electrokineticassisted phytoremediation to achieve soil purification in crop production.

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History
  • Received:October 30,2023
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  • Online: January 22,2024
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