Application Of PAHs Pollution In Soil And Soil Nutrient Regulation In Remediation Of Contaminated Soil In An Economic Development Zone

In this paper,30 surface soil samples were collected in Nanjing Economic Development Zone to analyze the content and source of 16 kinds of PAHs in the soil;indoor soil culture experiment was conducted by adding different amounts of nitrogen and phosphorus fertilizer to regularly detect the residual amount of PAHs in the polluted soil,and compare the remediation effect of different fertilizers on the polluted soil.To explore the role of enzymes in soil remediation by investigating the changes of enzyme activities in different soils.The main research results are as follows:The total content of 16 PAHs in the soil collected from Nanjing Economic Development Zone ranged from 137.96 to 1303.56μg·kg^-1,with an average of 356.39μg·kg^-1and a median value of 246.50μg·kg^-1.The soil pollution was generally in a mild pollution level.PAHs in the soil of the development zone mainly come from the combustion of biomass and coal,followed by oil combustion.The teqbap of 36.67%of the sampling sites exceeded 33μg·kg^-1of the 10 PAHs specified in the Dutch soil standard,and the distribution of the points was relatively concentrated.The soil in the section with heavy road traffic and the location of the petrochemical plant had been polluted by PAHs,and there was potential ecological risk.The rest of the sampling sites did not exceed the limit.The contents of 16 PAHs in topsoil of four areas（Qixia,Xingang,Longtan and LCD Valley）in Nanjing Economic Development Zone were499.86μg·kg^-1,399.56μg·kg^-1,211.14μg·kg^-1and 201.31μg·kg^-1,respectively.The average content of soil in Qixia area is the highest,mainly from the pollution emissions of petrochemical enterprises deposited in the soil;Xingang area takes the second place,because the points are mainly distributed along the road,so the PAHs in the soil are from automobile exhaust;the low content of soil in Longtan and LCD valley areas is due to the distribution of points in the areas with less vehicles and human activities.In this paper,fluoranthene was used as the target pollutant.The results of indoor cultivation experiments showed that the addition of nitrogen and phosphorus could significantly improve the removal rate of fluoranthene in soil.The removal rates of fluoranthene in TN11,TN12,TN13 and TN14 were 187.6%,225.5%,169.4%and157.2%higher than those in CK1,respectively.The removal rates of fluoranthene in TN21,NT22,TN23 and TN24 were 410.6%,426.8%,137.8%and 92.2%higher than those in CK2,respectively.The addition of nitrogen and phosphorus could significantly improve the removal rate of fluoranthene in soil,mainly because nitrogen and phosphorus fertilizer increased soil nutrient elements,improved soil nutrient cycle,and increased soil microbial biomass,and the removal rate of fluoranthene in soil was positively correlated with the addition of nitrogen and phosphorus.The removal rate of fluoranthene was the highest when the addition of nitrogen and phosphorus were 300 mg·kg^-1and 150 mg·kg^-1,respectively.The removal rate of fluoranthene decreased with the increase of nitrogen and phosphorus.The K value of fluoranthene removal rate constant was significantly higher than that of the control,and the half-life T1/2 of fluoranthene was significantly shortened.The number of bacteria,fungi and actinomycetes in soil increased significantly with the increase of nitrogen and phosphorus in soil.Under the same conditions,the promotion effect of nitrogen on the growth of microorganisms in soil was more obvious.Under the same nitrogen and phosphorus,the higher concentration of fluoranthene in soil would reduce the growth rate of microorganisms.In the same concentration of fluoranthene,the growth rate of microorganism was negatively correlated with the amount of nitrogen and phosphorus.The number of bacteria,fungi and actinomycetes in the soil was significantly positively correlated with the removal rate of fluoranthene（P<0.01）,indicating that the more active the microorganisms in the soil,the higher the removal rate of fluoranthene in the soil.The removal rate of fluoranthene was significantly positively correlated with K value（r=0.559;r=0.559;r=0.559;r=0.559）;P<0.05)。The changes of soil enzyme activities,including sucrase,polyphenol oxidase,urease and phosphatase,during indoor cultivation were studied.The results showed that there was a significant positive correlation between the activity of PPO and the removal rate of fluoranthene（r=0.850;r=0;P<0.01）。The activities of sucrase,urease and polyphenol oxidase were increased with the increase of nitrogen,while the activities of sucrase,acid phosphatase and polyphenol oxidase were increased with the increase of phosphorus.The effects of nitrogen on invertase and PPO were more significant.Both nitrogen and phosphorus can increase the activity of polyphenol oxidase in soil and promote the removal of fluoranthene.