Xuekai Dou

Hydrophobic organic compounds (HOCs) in water–soil systems pose persistent risks to pore water quality and groundwater safety because of their low aqueous solubility and strong soil sorption affinity. Electrokinetic remediation has emerged as a promising technology for controlling HOCs in contaminated water–soil systems, as it can regulate pore water movement, ionic migration, and contaminant transport under an applied electric field. However, the limited transfer of HOCs from soil into the aqueous phase restricts their electrokinetic removal efficiency, necessitating the use of surfactants to overcome these technical bottlenecks. This review elucidates the mechanistic basis of surfactant-enhanced electrokinetic remediation, with particular emphasis on micellar solubilization in pore water, contaminant desorption from soil matrices, and electrically driven transport across water–soil interfaces. Building on this mechanistic framework, the applications and performance of nonionic, anionic, cationic, biosurfactant, and mixed surfactants are summarized. Furthermore, the key factors governing surfactant efficacy are analyzed, including soil properties, contaminant characteristics, remediation objectives, operational parameters, environmental safety, and economic feasibility. By integrating mechanistic insights with environmental considerations, this review establishes a science-based framework for surfactant selection in electrokinetic remediation. This work provides a reference for enhancing contaminant transfer from soil matrices to the aqueous phase, reducing secondary risks to pore water and groundwater, and advancing the theoretical development and implementation of surfactant-enhanced electrokinetic remediation in environmental management.

The remediation of large-areas of Cd-contaminated soil, especially agricultural land, remains a major global challenge. Phytoremediation using hyperaccumulators is an effective method for treating Cd-contaminated soils; however, its long-term effectiveness over successive growing seasons has been insufficiently investigated. This study evaluated the sustained phytoremediation capacity of the farmland weed Bidens pilosa L., a known Cd hyperaccumulator, in a three-year pot experiment using contaminated agricultural soil from the Shenyang Zhangshi Irrigation Area (2.08 mg/kg Cd). Two harvest regimes were compared: short-term (harvest at the flowering stage, 70 days) and long-term (harvest at the fruit maturity stage, 108 days). The results showed that although higher total Cd accumulation per harvest was obtained in long-term treatments, short-term experiments resulted in a 14.7% higher net removal rate per day (NR) due to their shorter growth cycle (64.8% of the long-term period). Soil extractable Cd concentrations decreased by an average of 31.2% over three consecutive years of phytoremediation, reducing environmental risk but also limiting subsequent Cd uptake by plants. These findings demonstrate that optimizing harvest timing can substantially improve remediation efficiency per unit of time without the need for soil quality improvement measures. The short growing season characteristic of weeds found in agricultural areas is a practical advantage of phytoremediation.