Lead dissociation and redistribution properties of actual contaminated farmland soil after long-term EKAPR treatment

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Abstract
Electrokinetic-assisted phytoremediation (EKAPR) is a potential technology much affected by the metal species and accessibility to plant roots. In this study, Pb-contaminated red soil was remediated with Sedum plumbizincicola to investigate the changes in soil pH, available nutrients, dissociation and redistribution of Pb under a long-term periodic reversal direct-current electric field. This approach could effectively activate soil P, K, organic matter (OM) and Pb, without significant soil acidification; the effect was positively correlated with applied voltage. Soil Pb can be continuously dissociated, migrated, and tended to accumulate in the middle region. The maximum Pb removal rate in the anodic section of the EKAPR system was 21.4%, and the aggregation rate in middle regions was 14.4%, higher than the available Pb content of the original soil. The Pb desorption in aqueous solution increased significantly with increasing voltage, irrespective of the solution pH. At a voltage of 20 V, the Pb cumulative desorption content reached 91.1 mg kg−1 (pH = 7), which was 2.7 times than that without electric field (33.2 mg kg−1). Compared to original soil (2.80 mg kg−1) and the control (14.54 mg kg−1), the available Pb in the anode section of EKAPR system (20.66 mg kg−1) increased by 637.9% and 42.1%, respectively. These results indicated that except for the indirect influence of soil pH changes, electrodynamics can directly promote the bioavailability and dissociation of Pb at the soil–water interface. This finding provides a new perspective for further studies on the mechanism of Pb speciation evolution and accumulation changes using EKAPR. Graphical abstract
Funding Information
  • National Natural Science Foundation of China (51768074, 41701362)
  • Yunnan Agricultural Foundation Research Projects (202101BD070001-113)
  • Science and Technology Planning Project of Yunnan Province (2018FD020)
  • Scientific Research Foundation of Yunnan Agricultural University (A2002419)
  • Innovation Team for Farmland Non-pollution Production of Yunnan Province (2017HC015)
  • oung and Middle-aged Academic and Technical Leaders Reserve Talent Project of Yunnan Province (202205AC160080)

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