Retarding Effect And Mechanism Of Cationic Surfactant On The PAH-migration In Soil-plant System

Surfactants have significant effects on the environmental behavior and bioavailability of organic pollutants. Based on the review of surfactant effects on the migration of organic pollutants in soil-plant systems, this thesis investigated the effect and mechanism of cationic surfactant on the PAH-behavior at the soil/water/air/plant interfaces. The retarding effect of cationic surfactant on plant uptake and accumulation of polycyclic aromatic hydrocarbons (PAHs) was found, which may provide a new approach to obtain safe agricultural products from contaminated soils.The main results of this thesis are shown below:(1) The different efficiencies of cationic surfactants in enhancing soil sorption of PAHs should be attributed to the different sorption amount of surfactant on the soil components, and the different PAH partition capabilities for the adsorbed surfactants. Linear relationships between the surfactant-normalized PAH distribution coefficients by the sorbed surfactant (Ksf) and the loadings of cationic surfactant (Q) were found for each soil component, which provided a possibility to predict the efficiency of the cationic surfactant in enhancing soil sorption of organic contaminants.(2) The effect and mechanism of cationic surfactant on the volatilization of naphthalene (NAP), acenaphthene (ACE), and phenanthrene (PHE) from soil to air was studied. The soil-sorbed surfactant had a significant negative effect on the solid-vapor volatilization of NAP, ACE and PHE. However the dissolved surfactant with low concentration promoted the liquid-vapor volatilization of the dissolved NAP, ACE and PHE in soil solution. The relative contribution of these two opposite effects was changed with the water content of soil. The PAH-volatilization inhibition by cationic surfactant was more significant when the soil was moister.(3) The retarding effect of cationic surfactant on plant uptake and accumulation of phenanthrene and pyrene was investigated, and the influence factors such as soil properties, plant characteristics, the time-depended effectiveness, dosing frequency and the ecological safety of the surfactant were studied. The technique was more suitable for the soil with higher clay content and the plant with more fat content. Multiple-low-dose treatment of cationic surfactant on contaminated soil can reduce the surfactant lose and promote the retarding effect. The surfactant had no significant impact on the plant growth or soil microbial activity.