The Co-application of Willow and Earthworms/Horseradish for Removal of Pentachlorophenol from Contaminated Soils

Pentachlorophenol (PCP) was once commonly used as a pesticide worldwide, and is now a toxic and recalcitrant environmental pollutant. To explore a practical approach in the remediation of PCP-contaminated soils in China, we evaluated the efficacy of a local willow (Salix × aureo-pendula CL “J1011”) on removing PCP and assessed the potential of a native earthworm (Metaphire guillelmi) and horseradish (Armoracia rusticana Gaerth), alone and in combination with willow, to enhance the efficiency of removing PCP from spiked field soils. Willow, horseradish, and earthworms alone significantly increased PCP removal from soil. After 45 days, only 47.2% of the PCP remained in the presence of willow alone; 68.4, 51.4, and 46.3% of the PCP remained with 50, 100, and 200 g horseradish m^?2, respectively; and 41.1% of the PCP remained in the presence of earthworms. The removal of PCP from soils significantly increased with co-application of willow and horseradish (23.1% remaining) and especially with the co-application of willow and earthworms (2.2% remaining). Our results indicate that in terms of remediation efficiency, economic value, ecological benefits, and ease of use, a system consisting of this autochthonous willow and indigenous earthworms has great potential for the remediation of PCP-polluted soil in China.