Studies On Transport And Degradation Of Polycyclic Aromatic Hydrocarbons In Soil-plant Systems

Polycyclic Aromatic Hydrocarbons (PAHs) are the ubiquitous persistent organic pollutant in the environment. Recently, more and more attentions are paid on the behaviors and fates of polycyclic aromatic hydrocarbons because of their potential hazard and risks to environment and humans. There will be very important practical meaning to effectively control pollution of PAHs and protect humanity from harm if we make clear the transport of polycyclic aromatic hydrocarbons and its influence factors in soil-plant systems. Because of these above reasons, this paper studied the transport of polycyclic aromatic hydrocarbons and effects of soil amendments and plant species diversity on the degradation of PAHs.The main results are summarized as follows:(1) Adsorption behaviors of pyrene in soils were investigated .The results showed that adsorption of pyrene in soils can be reached by two mainly processes,"quick"and"slow".Pyrene is rapidly adsorbed into soil particle surface in the first five hours of this experiment, subsequently, the adsorption rate becomes slow and stable gradually. The adsorption basically reaches equilibrium after 24 hours. There is good linear relationship between adsorption of pyrene in 4 kinds of soils and the concentrations of pyrene in aqueous phase ,and LogKoc values of pyrene in four soils are almost same.(2)Effects of soil amendments(bone char,activated carbon,peat) on the transport and degradation of pyrene,fluoranthene and benzo[k]fluoranthene in soil-plant system were investigated. The results indicated that all of three soil amendments could significantly decrease concentrations of pyrene, fluoranthene and benzo[k]fluoranthene in soils , inhibit the transport of three PAHs into ryegrass,reduce accumulation of three PAHs in ryegrass. and concentrations of pyrene,fluoranthene and benzo[k]fluoranthene in soils,and ryegrass are negatively correlated with mass of three amendments.(3) Ryegrass, white clover and alfalfa were used to studied effects of plant species diversity on transport and degradation of pyrene in soil-plant system.Results showed that plant species diversity raise bioconcentration of pyrene in white clover and alfalfa, promote transport of pyrene from soil into white clover and alfalfa, increase accumulation of pyrene in roots and shoots of white clover and alfalfa, but bioconcentration of pyrene in ryegrass and pyrene concentrations in roots and shoots of ryegrass are essentially unchanged. In addition, plant species diversity increases soil microbial biomass, improves polyphenol oxidase activity of soil and accelerates degradation of pyrene in soils. Therefore, pyrene in soils are significantly reduced,and concentrations of pyrene in soils grown plants are respectively different from that in soils without plants. Concentrations of pyrene in soils with different treatment are lower and lower with increase in plant species diversity in this paper.