Study On The Characteristics Of Vertical Migration And Ecotoxicity Of Petroleum In Loess Soil

Northern Shaanxi is an important petrochemical base in my country,which has helped the development of my country's industry,agriculture,and transportation.Oil-containing pollutants will inevitably leak during the process of oil extraction and transportation.These substances that are difficult to degrade naturally will migrate in the environment in a variety of ways,directly affecting the local soil,groundwater and other environmental media,and affecting the production and life of local residents.It also poses a serious threat.The composition and properties of oil are relatively diversified,making its migration process in the soil more complicated.According to the characteristics of climatic conditions and soil quality in northern Shaanxi,the paper conducts soil column leaching experiments.Taking the annual rainfall of 550 mm in northern Shaanxi as the specific climate background for the study,the analysis and comparison of petroleum hydrocarbon pollutants in the homogeneous loess soil(HMJ),heterogeneous loess soil(HMF),and campus homogeneous garden soil during the leaching process in northern Shaanxi were carried out.(HYJ),the characteristics of vertical migration in campus heterogeneous garden soil(HYF).The experimental results show that under the condition that the total leaching water volume in the three leaching cycles is 2800 m L,the petroleum pollutants in the four different soils are mainly trapped by the soil at 15 cm of the surface layer.The second and third cycles of leaching affect the 4 soils.The vertical migration of total petroleum hydrocarbons,C14-C30 alkane components,and polycyclic aromatic hydrocarbon components at a depth of 35 to 45 cm in the column has little effect.Among them,the order of interception capacity for TPH and C14-C30 alkanes is: garden heterogeneous soil> garden homogeneous soil> loessial heterogeneous soil> loessial homogeneous soil.In the same kind of soil,the effect of heterogeneous soil on the interception of petroleum pollutants is better than that of homogeneous soil.Use wheat seed germination experiment and earthworm acute toxicity experiment to analyze the ecotoxicity risk of total petroleum hydrocarbons(TPH).When the content of TPH in the soil is ? 15200 mg/kg,the germination rate of wheat is ?43.3%,and with the increase of TPH pollution concentration,the germination rate of wheat decreases significantly.The average plant height(3.90 cm)of wheat in oily soil(TPH ? 15200 mg/kg)15 days after sowing was significantly lower than that in uncontaminated soil(5.79 cm).The chlorophyll a,chlorophyll b,and carotenoids in wheat were significantly negatively correlated with the content of TPH in the soil(p<0.01).When the TPH in the soil is ?15000 mg/kg,the weight loss of earthworms in 14 days is ?94 mg(the blank group is 44 mg).The high concentration of petroleum hydrocarbons in the soil has a significant inhibitory effect on the growth of earthworms.Based on the 7:3 ratio of alkanes and polycyclic aromatic hydrocarbons in the total petroleum hydrocarbons,equivalent amounts of alkanes and polycyclic aromatic hydrocarbons were added to the clean soil for artificial pollution,and the ecological risks of different components of petroleum hydrocarbons were examined.When the content of alkanes in the soil is 14000 mg/kg,the germination rate of wheat at 7 days and 14 days after sowing is 50% and 63%,respectively;the weight of earthworms is reduced from 232 mg to 148 mg(7 d)and 168 mg(14 d),respectively.When the content of polycyclic aromatic hydrocarbons in the soil is 6000 mg/kg,the germination rates of wheat on 7 days and 14 days after sowing are 33% and 46.7%,respectively,and the weight of earthworms is reduced from 228 mg to 127 mg(within 7 days)and 143mg(Within 14 d).The contents of chlorophyll a,chlorophyll b and carotenoids in the soil contaminated by alkanes at 14 d were 5.17 mg/g,2.79 mg/g,0.41 mg/g;in the soil contaminated by polycyclic aromatic hydrocarbons: 4.57 mg/g,2.50 mg/g,0.30 mg/g;indicating that the toxicity risk contribution rate of polycyclic aromatic hydrocarbon components in petroleum hydrocarbons is higher than that of alkanes.The 16sRNA gene amplicon high-throughput sequencing technology was used to compare and analyze oily soil contaminated for 10 days.The sequencing results showed that the alkane component inhibited soil microbial diversity more significantly than the polycyclic aromatic hydrocarbon component.At the microbial level,the abundance of Proteobacteria in the soil contaminated by alkanes and polycyclic aromatic hydrocarbons increased to 39.07% and 31.87%,respectively;the abundance of Actinobacteria decreased to 41.7% and 48.81%;Pseudomonas increased to 23.91%,16.60%;it shows that the alkane component has a stronger effect on the growth of Proteobacteria and Pseudomonas than the polycyclic aromatic hydrocarbon component.Actinobacteria has the worst tolerance to alkane components.