Effects of Electric Field Dimensions on Electrokinetically Enhanced Cadmium Dissociation and Phytoremediation in Plateau Red Soil

The enhanced performance of electrokinetics (EK) on the cadmium (Cd) dissociation, redistribution, and phytoremediation of Cd-contaminated agricultural soil has been investigated based on the application of an electric field in different dimensions (1D, 2D, 3D). In electrokinetic-assisted phytoremediation (EKPR), unlike the uniform pH change observed in 1D treatment, more soil points (P1-P9) under 2D/3D electric fields were exposed to the influence of the anode (or cathode during polarity switching). <i>Sedum plumbizincicola</i> mitigates EK-induced soil acidification and alkalization, particularly anode acidification under high voltage (10-20 V). Studies reveal that EK promotes Cd dissolution into soil pore water, with a 227.82% maximum increase in the anode region under EK2 treatment of 10 V voltage, facilitating Cd phytoextraction. Periodically reversed DC electric fields enhanced <i>Sedum plumbizincicola</i> height more significantly than biomass, with no conspicuous regional differences. Overall, EKPR (voltage of 5-10 V) can effectively promote soil Cd phytoremediation due to the synergistic effect of direct interface action and indirect influence of the electric field to improve the Cd speciation evolution, dissociation, and bioavailability at the soil-water interface. The appropriate electric field arrangement and voltage were 2D treatment (EKPR2) and 5 V for <i>S. plumbizincicola</i>, respectively. In this case, the average Cd removal rate was as high as 50.23%, and the biomass and Cd accumulation increased by 16.59% and 29.31%. This suggests that plant growth constitutes the pivotal stage driving Cd accumulation and ultimately achieving Cd removal from soil, which is the key to enhancing remediation efficiency. Meanwhile, the configuration and intensity regulation of electric fields, as core elements ensuring the enhanced efficacy of electrokinetic-assisted phytoremediation (EKPR), can indirectly affect plant growth and Cd accumulation processes by modulating intermediate variables such as soil pH, nutrient status, and heavy metal speciation evolution.