Enhanced Ryegrass Uptake Of PAHs By Anionic-nonionic Mixed Surfactants

The soil contamination with hydrophobic organic compounds (HOCs) such as polycyclic aromatic hydrocarbons (PAHs) is a widespread environmental problem. Surfactant-enhanced phytoremediation has been suggested as a promising technology for the remediation of contaminated soils. The anionic-nonionic mixed surfactant had greater capacity in enhancing the solubilization of HOCs and the potential in enhancing the biodegradation of PAHs. Up to date, little information is available on the plant uptake of HOCs in the presence of anionic-nonionic mixed surfactants.In this paper, the uptake of PAHs by ryegrass in the presence of anionic-nonionic mixed surfactants was investigated using a hydroponic system. Various factors including the compositions and concentrations of mixed surfactants and the physicochemical properties of the contaminant were assessed. The main valuable conclusions are shown as follows:(1) SDBS-TX100 and SDBS-Tween80 mixture with various compositions could enhance the uptake of PAHs by ryegrass. For example, SDBS-TX100 mixture with a mole ratio of SDBS to TX100 at 9:1 had the greatest capacity in enhancing the uptake of phenanthrene and pyrene, and the corresponding maximal concentrations of phenanthrene and pyrene in ryegrass roots were 216 and 8.16 times those without surfactants, respectively. Thus the anionic-nonionic mixed surfactant had greater capacity in enhancing the uptake of PAHs and would be a preferred selection for surfactant-enhanced phytoremediation technology to contaminated soil.(2) The major factors including the compositions and concentrations of mixed surfactants and the physicochemical properties of the contaminant were discussed. The results showed that the anionic-nonionic mixed surfactant SDBS-TX100 and SDBS-Tween80 can enhance the uptake of PAHs by ryegrass in a wider range of surfactant concentrations in comparing with corresponding single surfactants, and the maximal contents of PAHs in ryegrass roots were obtained with the surfactant concentrations around critical micelle concentrations. SDBS-Tween80 with certain compositions and concentrations could enhance traslocation of acenaphthene, fluorene and phenanthrene from roots to shoots.