Effects Of Different Soil Organic Matter Fractions On The Aging And Bioavailability Of Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons?PAHs?are typical POPs that are fused with two or more benzene rings and are carcinogenic,teratogenic,and mutagenic.PAHs enter the soil through dry and wet sedimentation,sewage irrigation,sludge application,etc.,and can persist in soil for a long time,thus causing harm to human health.Therefore,the study on the migration and transformation of PAHs in soil and the bioavailability of PAHs in soil have important environmental significance for environmental pollution assessment and restoration.In this study,the method of continuous removal of different organic matter components in soil was used to obtain heavy fraction?de-light organic matter?,heavy fraction without the loosely combined humus and tightly combined humus.The PAHs highly degrading bacteria Pyr-10?Agromyces sp strain?selected by the laboratory studied the effects of different organic matter components on the bioavailability of PAHs.The specific research concentrations include:1.The distribution characteristics of PAHs in different organic matter in the field contaminated soil;2.The influence of different organic matter components on the aging and bioavailability of artificially added Pyr;3.The PAHs bioavailability in different organic matter components in the field contaminated soil.The main findings are as follows:1.The concentration and composition of contaminated soil and its LF and HF,PAHs in six typical areas?steel plants,coking plants,etc.?were analyzed.The results show that?1?the concentration and composition of PAHs in soil under different pollution modes are obvious characteristic differences.The characteristics of Nap,Phe and FluA in soil contaminated by coking plant are relatively high;the concentrations of Pyr,BaA and Chry in steel,oil and gas plants and contaminated soil by farms are relatively high;?2?PAHs concentration and composition in soil LF are quite different from the whole soil and HF,The concentration of high molecular weight PAHs in LF of farms,oil and gas plants and steel plants is significantly higher than that of coking plants,while the concentration of low molecular weight PAHs is lower than that of coking plants.?3?The classification of PAHs in different soil LF under the same pollution mode is quite different,the concentration of Nap and Pyr in Guizhou Coking Plants is higher than that of Shanxi Coking Plants,which may be related to the structural heterogeneity of the LF and its turnover rate.TEQ_BaP of PAHs in soil LF is much higher than whole soil and HF,and there is a large ecological risk.2.The 240-day aging phenomenon and microbial degradation under different time aging were studied in the soil and soil components of Brown soil and Latosols soil with different organic matter concentration.The results showed that in the Brown soil,the extractable rate of Pyr in each component can be well fitted by the kinetic equation?R²=0.93⁰.98?,Within 0-15 days of aging,the extractable rate of Pyr in all soils and organic matter components?34.3³8.9%?was significantly lower than that of whole soil and organic matter components in aging 0 days?P<0.05?,while the Brown soil de-light organic matter,heavy fraction without the loosely combined humus and tightly combined humus under the same aging time.There was no significant difference in the Pyr extractable rate?P>0.05?.The extractable rate of Pyr in whole soil was significantly lower than that of other components after LF removal at 15-240 days.In Latosols soil,the extractable rate of Pyr in each component can also be well fitted by kinetic equation?R²=0.96⁰.98?.The decline trend of the extractable rate of Pyr in each organic component is maintained to 30 days,and the whole soil is aging 240 days.The extractable rate of Pyr?6.23%?was significantly lower than that of Pyr after removal of LF?17.8¹8.7%??P<0.05?,indicating that the removal of LF resulted in the adsorption of soil organic matter on Pyr.There was no significant difference in the extraction rate of Pyr between de-light organic matter,heavy fraction without the loosely combined humus and tightly combined humus under the same aging time?P>0.05?.Among the whole soil and different organic matter components of brown soil,the degrading bacteria have higher degradation rate for each organic matter component.However,in addition to de-light organic matter the other components,the longer the aging time,the lower the degradation rate of Pyr in the organic matter.The degradation rate of Pyr in each component of Latosols soil also showed a similar trend.3.The biodegradation of PAHs in the soil and its different soils of long-term pollution of PAHs with different organic matter concentrations was studied.The results showed that the concentration of PAHs in the whole soil of Cinnamon soil was significantly higher than other components of the removed LF.The concentration of PAHs in the whole soil of Paddy soil was significantly higher than that of other components.In the soil organic matter of the two soils,the PAHs in the whole soil showed a significant decrease?P<0.05?,but there was no significant change in the PAHs concentration in other organic components.