| Polycyclic aromatic hydrocarbons(PAHs)are important environmental pollutants,which are composed of two or more benzene rings and are formed by incomplete combustion of coal,oil and other organic compounds.PAHs have been listed as priority control pollutants by many countries because of their carcinogenic,teratogenic,mutagenic effect to human.With the development of industrialization in China,PAHs have been widely distributed in soil,air and other environmental media.PAHs can be retained in soil for a long time due to their high octanol water partition coefficient.Therefore,it is detrimental to human's health after they enriched in the food chain.Biochar is a kind of highly aromatic and insoluble solid matter which is derived from pyrolytic carbonization of biomass in limited air condition.It is rich in carbon content and nutrients and has well-developed pore structure,large surface area and thus a strong absorption capability.Based on these characteristics,biochar plays a significant role in maintaining the balance of the soil ecosystem.Biochar can be used for soil remediation which was contaminated by PAHs.It can improve the physical and chemical properties of soil,enhance the soil fertility and the keep the ability of keeping entropy.However,the characteristics of biochar can be influenced by environment once it was applied in soil,to investigate the changes of biochar which effected of leaching and oxidation in soil is necessary.The experiment studied the effect of fresh biochar and aging biochar on the total and bioavailable of PAHs in soil with corn straw biochar,in order to provide theoretical basis for remediation of contaminated soil.The addition of biochar into soil can increase PAHs adsorption capacity to soil.When the adding amount was 0.1%~5.0%,the soil adsorption capacity of PAHs can be greater with the increase of biochar amendment.At the end of the incubation,the total concentrations of phenanthrene and pyrene in the amended treatments decreased by 15.6%~27.4% and 12.8%~36.5%,respectively,when compared to the control(without biochar ad dition).The bioavailable concentrations of phenanthrene and pyrene decreased 14.7%~37.4% and 23.4%~52.3%,respectively.With the respect of volatile PAHs,an obvious inhibition was observed in 5.0% amendment at the beginning of the incubation.The volatile phenanthrene and pyrene in 5.0% biochar addition decreased by 54.5%~56.5% and 81.1%~83.6%,respectively,when compared to the 0.1%,1.0%,2.0% application.However,at the end of the incubation,no significant differences(P>0.05)were observed for the inhibition rate between phenanthrene and pyrene,regardless of the biochar amended rate.The dose-effect of biochar in reducing the total and bioavailable PAHs and inhibiting volatilization of PAHs highly depended on the species of PAHs,the difference in the degree of dose-effect can be greater with the increase of biochar amendment.Fresh biochar,oxidized biochar and deashing biochar were added into soil at the rate of 5.0%,the reduction of total concentrations of phenanthrene raises to 27.3%,27.7%,28.5%,and 34.5%,34.8,35.7% for pyrene,respectively,when compared to the control,the groups were no significant differences(P>0.05).The volatile PAHs of phenanthrene and pyrene decreased 21.9%~25.5% and 27.9%~28.6% in three treatment groups,respectively,no significant differences(P>0.05)were observed between the fresh biochar and aging biochar(oxidized biochar,deashing biochar).On reducing the bioavailable phenanthrene in soil,fresh biochar,oxidized and deashing biochar also have no significant differences(P>0.05)except the first week,but on reducing the bioavailable pyrene in soil,the reduction rate of the oxidized biochar and deashing biochar significant higher than fresh biochar(P<0.05),were 93.1%,92.5%,91.5% respectively. |
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