Citric acid as a soil leaching agent for phytoremediation of arsenic-contaminated soil: migration, plant uptake and remediation efficacy

Phytoremediation and soil washing are effective methods for the remediation of arsenic-contaminated soil. In this study, citric acid solution was utilized as a soil leaching agent for in-situ leaching of arsenic-contaminated soil <i>via</i> drip irrigation, aiming to explore the migration and distribution of arsenic in the soil. Hydroponic experiments were conducted to investigate the influence of citric acid on plant absorption and translocation of arsenic. Finally, intercropping of <i>Brassica rapa</i> L. ssp. <i>chinensis</i> and <i>Zea mays</i> L. was carried out under drip irrigation, to explore the effectiveness of citric acid as a soil leaching agent in phytoremediation of arsenic-contaminated soil. The results indicated that after drip irrigation with citric acid solution, the arsenic in the soil undergoes directional migration and exhibits differentiated distribution. Citric acid significantly affected the absorption and transport of arsenic in <i>Brassica rapa</i> L. ssp. <i>chinensis</i> and <i>Zea mays</i> L. Notably, the lowest arsenic content in <i>Brassica rapa</i> L. ssp. <i>chinensis</i> was observed at a citric acid concentration of 2 mmol·L^-1. After drip irrigation with 2 mmol·L^-1 citric acid solution, the arsenic content in <i>Zea mays</i> L. (remediation plant) increased by 23.34%, while the arsenic content in <i>Brassica rapa</i> L. ssp. <i>chinensis</i> decreased by 10.70%. As a soil leaching agent, citric acid effectively enhanced the phytoremediation of arsenic-contaminated soil.