Risk Assessment And Remediation Technology Development Of Petroleum Hydrocarbon Pollution In Soil Surrounding Oil Field

As an important energy source,petroleum has contributed a huge role in the process of economic development.However,petroleum pollutants（petroleum hydrocarbons,polycyclic aromatic hydrocarbons,etc.）leaked into the soil during petroleum exploitation and transportation have damaged the balance of soil ecological environment.Polycyclic aromatic hydrocarbons in soil also have strong three carcinogenic effects（carcinogenic,teratogenic and mutagenic）,which will bring serious risks to soil ecological environment and food safety.Therefore,it is very important to study the level of oil pollution and the remediation technology of oil polluted soil.Taking the soil around Yanchang Oilfield as the research object,the contents of TPH,petroleum hydrocarbons(C₁₀～C₄₀)and 16 kinds of PAHs in the study area were investigated,the potential risks of TPH and PAHs in the soil were assessed,and the pollution sources were analyzed.On this foundation,the technical system of surfactant leaching and advanced oxidation（discharge plasma technology and Peracetic acid oxidation）post-treatment of leaches was established for the remediation of oil-polluted soil,the influence of different factors on the degradation of petroleum hydrocarbons were investigated,the removal law of petroleum hydrocarbons in leaches by typical advanced oxidation technology was clarified,and the treatment process was optimized.The main research findings are as follows:（1）The TPH content of 75 soil samples in the study area ranges from 102.06～4290.03mg/kg,and the pollution degree is positively correlated with the distance from the oil well,and gradually decreases with the increase of soil depth.It is concluded that the study area belongs to the high and severe pollution level.The pollution levels of petroleum hydrocarbon(C₁₀～C₄₀)in the samples were investigated.The contents of C₁₀～C₄₀ in the profile and surface samples were 207.72～3420.82 mg/kg and 87.04～2530.48 mg/kg,respectively,which were dominated by short and medium chains,and the petroleum hydrocarbon content was higher near the oil well.16 kinds of monomer polycyclic aromatic hydrocarbons in the soil in the study area were detected,has been widely polluted by PAHs,lowest and highest PAHs concentration of monomer,Chrysene（Chr）and Anthracene（Ant）,16 kinds of PAHs concentration combinedΣ16 PAHs in the range of216.48～3637.59 betweenμg/kg.In the representation of component characteristics,the 3～5rings are relatively large.The ecological risk of PAHs was assessed by benzo[a]pyrene toxicity equivalent method and risk quality benchmark method.The results showed that the toxic equivalent concentration(TEQ_{Ba P})of most samples was higher than the standard value,and there was a large degree of pollution risk and a certain degree of biological toxicity risk.The results of the lifetime cancer risk method showed that adults and children had a higher risk of cancer through ingestion and skin absorption of PAHs.The results of source analysis showed that the main sources of PAHs were petroleum and biomass combustion,and there were some petroleum sources.（2）The surfactant leaching and discharge plasma treatment process has a good effect on the degradation of soil petroleum pollution.Considering the leaching effect and economic benefit,sodium dodecyl benzene sulfonate（SDBS）was selected as the repair detergent.After 72 h reaction,the eluting rate of petroleum hydrocarbon reached 69.86%in the first time and 57.44%in the second time.When the discharge voltage is 16 k V and the gas flow rate is 160 L/h,the degradation rate of petroleum hydrocarbon in the eluent by discharge plasma can reach 81.51%.The free radical quenching experiment showed that·OH and·O₂^-played a major role in the reaction,resulting in the decomposition of petroleum hydrocarbons to produce microbial metabolites,humic acids and tryptophan-like protein substances.The detection of degradation intermediates could indicate that large hydrocarbons were degraded into small molecules of alkanes,aromatic hydrocarbons,alcohols,etc.After three times of recovery,the elution rates of petroleum hydrocarbon were 65.05%,50.95%and 20.19%,respectively.With the increase of the number of times,the recycling performance of petroleum eluent decreased gradually,which was 9.38%for the fourth time.（3）On the basis of washing petroleum polluted soil with SDBS,the effect of oxidation of Peracetic acid（PAA）on the removal of petroleum hydrocarbon from petroleum eluents was investigated.The change of PAA concentration in the reaction system using two aqueous solutions of water and SDBS-Peracetic acid for oxidative degradation of petroleum hydrocarbons was analyzed.It was found that the PAA concentration decreased significantly after washing the soil with SDBS,but did not change significantly during washing,indicating that SDBS and PAA jointly promoted the reaction.The effects of different PAA concentration and p H on the degradation rate of petroleum were explored.When the PAA concentration was 0.2%and p H=7,the degradation rate of TPH was75.75%,slightly lower than that of the discharge treatment.It was found that R-O·played the most important role in identifying the types and functions of active free radicals.The difference between the degraded petroleum hydrocarbon components and the discharge reaction system is the tyrosine-like protein substances.The degraded intermediates mainly consist of alkanes,aromatic hydrocarbons,esters,alcohols and other complex components,which are different from the discharge to remove petroleum pollution.The comparative analysis of the two post-treatment processes shows that the degradation rate of petroleum under the same treatment time is higher than that under Peracetic acid oxidation.The former has a larger k value and a lower energy efficiency than that under Peracetic acid oxidation for petroleum hydrocarbon degradation.However,the cost of the two processes is not much different.The results show that both discharge plasma and Peracetic acid oxidation can be widely used in the remediation of petroleum polluted soil.In conclusion,the pollution levels of soil at different distances from oil fields indicate that oil exploitation has different degrees of harm to surrounding soil,and the potential risk assessment and source analysis of soil oil pollution are put forward.Considering the ecological environmental benefits,economic benefits and social benefits,a reaction system of the leaching of contaminated soil by surfactant-discharge plasma technology and the oxidative degradation of petroleum hydrocarbons by Peracetic acid was established,which can provide technical support for the actual risk assessment and remediation of petroleum soil pollution.