Ornamental hyperaccumulator Mirabilis jalapa L. phytoremediating combine contaminated soil enhanced by some chelators and surfactants

Abstract

Mirabilis jalapa L. is an ornamental plant of the composite family, which was found hyperaccumulating Cd. Due to its larger biomass, developed root system, root exudation, and microbial interactions, certain organic pollutants in its rhizosphere can be effectively degraded. Thus, M. jalapacan be used to co-remediate heavy metal and organic pollutant co-contaminated soil. The aim of this paper is to explore the remediation capacity of M. jalapa for Cd-PAHs co-contaminated soil in the presence of five chelators or surfactants. The concentrations of Cd and PAHs in collected soil samples were 0.85 mg kg⁻¹ Cd and 1.138 mg kg⁻¹ PAHs (16 kinds of priority control polycyclic aromatic hydrocarbons by USEPA). The chelators or surfactants of EDTA, EGTA, CA, TW80, and SA were respectively spiked to the pots according to the experiment design at 1 month before the plant harvested. The results showed that the capacity of Cd in shoot of M. jalapa was 7.99 μg pot⁻¹ without any addition (CK4, M. jalapa in original soil without amendment). However, Cd capacity in shoot of M. jalapa was increased (p < 0.05) by 31.7%, 181.7%, and 107.4% in treatment of R_EGTA, R_CA and R_{EGTA + SA}, respectively. As for the degradation of PAHs in soil, there was no significant decrease (p < 0.05) in the treatment of CK2 (original soil spiked with 0.9 SA without M. jalapa), CK3 (original soil spiked with 0.3 TW80 without M. jalapa), and CK4 compared to the control CK1 (original soil without M. jalapa and amendment). When amendments were added to soils with M. jalapa,the PAHs concentrations in soils significantly decreased (p < 0.05) by 21.7%, 23.8%, 27.0%, 19.8%, 21.8%, 31.2%, and 25.5% for the treatment of R_{EDTA + SA}, R_{EDTA + T80}, R_{EGTA + SA}, R_{EGTA + T80}, R_{CA + T80}, R_{SA + T80 + EDTA}, and R_{SA + T80 + CA}, respectively. Basically, Cd capacity in shoot of M. jalapa was improved by chelators. PAHs degradation was caused by the existence of surfactants in rhizosphere of M. jalapa. But the roles of different chelators or surfactants were quite distinct. In short, the Cd capacity in the shoot and PAHs degradation in the rhizosphere of M. jalapa in the treatment of R_{EGTA + SA} were all significantly increased (p < 0.05), which was more practical for M. jalapa phytoremediating Cd-PAHs co-contaminated soil.