Studies On Degradation Characteristics And Impact Factors Of Pahs In Soils

Polycyclic aromatic hydrocarbons(PAHs) are persistent organic pollutants(POPS) widely existing in the environment.PAHS have received popular and environmental attention due to their strongly recalcitrant degradability and the carcinogenic,mutagenic and tumorigenic properties.The behaviors of PAils in the environment are of increasing concern.They are widespread in human life of the natural environment such as air,water, soil,crops and food.In recent years the large number of studies indicated the pollution of polycyclic aromatic hydrocarbons has been a threat to human health and ecological security, on the basis of self-purification capacity in the natural world,through various effective ways or measures to promote the rapid transformation of nature,environmental degradation in the accumulation of PAHS,is of great significance.In this paper,benzo[a]pyrene(BaP) and dibenzo[a,hi anthracene(DBA) as the representative,a method to rapidly extract BaP and DBA in soil was established.Through laboratory testing,degradation characteristics of BaP and DBA in different environmental factors were studied.Simulation of biological reactor restoration techniques of the two pollutants were preliminary established.A method to determine BaP and DBA in soil was established by ASE-HPLC-PAD.In order to intensify ultraviolet response of target components and reduce the interference, detection wavelengths(λ_max of BaP 294.6nm,DBA 295.8nm),extract solvent and extraction methods were optimized,dichloromethane and acetone-dichloromethane (volume ratio of 1:1) as extract solvent and ASE method were selected.When the added concentration in soils between 0.02～0.50mg/kg,the recovery rates of BaP and DBA were 77.26%～109.56%,RSD were 0.60%～2.74%.The minimum detectable concentration was 2.5μg/kg and 1.0μg/kg respectively.Under laboratory conditions,a more systematic study was made on the degradation and impact factors of BaP and DBA in the soil.Four kinds of soil,Loamy soil from Shanghai,Red Soil from Jiangxi Province,Black Soil from Northeast China and Tai-lake Paddy Soil from Jiangsu province,were used.Results indicate that the degradation reaction of BaP and DBA was slow in above soils.The organic matter content and pH of soil have the obvious influence on their degradation.When the added concentration was 2.5mg/kg, BaP degraded quickly in the acidic soil of Jiangxi red soil,125 days later,the degradation rate reaches 87.3%;DBA degraded quickly in the neutral Tai-lake Paddy Soil,the degradation rate achieves 52.0%after 125 days.The suitable C-N content was adjusted by adding green manure to speed up the degradation of contamination soil.The main effect factor of bio-degradation of BaP and DBA in these four sorts of soils was indigene micro-organism.Aerobic condition is advantageous to the degradation of BaP and DBA,so we considerthat the microorganisms degrading BaP and DBA belong to aerobic bacterium.In use of simulated biological reactor technology,these two pollutants bioremediation control factors were explored and researched.The results showed that:additional EM bacteria,fertilizer,green manure and straw and the regulation of air traffic circumstances, can change degradation rates of these two pollutants in soil.In the 2 percent increase for green manure,ventilation flow rate of 0.10m³/h,the two pollutants achieve the best effect of the degradation,160 days after the degradation rate reached 44.6%and 67.6%.It reached good results in use of simulated biological reactor dealing with the two organic pollutants in soil.Through extraction methods of optimization of BaP and DBA in soil,begin with environmental limiting factors of degradation,studied the two PAHs contaminants' degradation characteristics in the soil and simulated biological reactor in degradation of the two pollutants.In the process of unique advantages,initially setting a pile of contaminated soil restoration of the main technical parameters,so as to establishing of an effective restoration of similar organic pollutants in soil and providing a theoretical basis.