Nutrient Synergistic Fungal Remediation Study Of Motor Oil Contaminated Soil

Due to the accelerated industrialization and persecution of the ecological environment,the available soil resources have been drastically reduced.Petroleum hydrocarbons are the main pollutants of organically contaminated soil.Excess total petroleum hydrocarbons enter the soil environment and are difficult to remove,and directly damage the ecosystem and threaten human health through unconscious diffusion and release.In this paper,the feasibility of degrading oil by strains in the petroleum hydrocarbon-contaminated soil of the site was studied,and the influence of different environmental factors on its degradation effect.Different types of nutrients were used to stimulate strains to remediate oil-contaminated soil,and the microbial diversity in soil before and after restoration was discussed.The main research results are as follows:Several strains with oil-degrading properties can be screened out from the petroleum hydrocarbon-contaminated soil of high-concentration sites,and the strain with the best effect can be screened out.After ITS(Internal transcribed spacer)sequencing identification,this strain is the Aspergillus versicolor.Four single factors were explored,the influence of variables(the amount of bacteria added,p H,salinity,degradation time)on its degradation effect,the initial concentration of oil in water is 2500 mg/L,the amount of bacteria added is 5%,p H=6.0,and salinity is 3 g/L,under the condition of lasting 5 d,the maximum degradation rate of the strain to the oil in water can reach 42.6%.Only changing the environmental factors is more limited improving the degradation effect,but adding 1.8 m L of sophorolipids or1.5 m L of tea saponin solution for bioaugmentation can increase the removal rates of strains by 19.4%and 28.6%,respectively,and the highest degradation rate can be increased to 71.2%.Total petroleum hydrocarbon concentration in motor oil contaminated soil was 5225mg/kg,the direct degradation of total petroleum hydrocarbons in contaminated soil by Aspergillus versicolor was not satisfactory,and the addition of nutrients to the oil-contaminated soil could effectively enhance the degradation and petroleum hydrocarbon availability of Aspergillus versicolor,and the best effect was achieved with additional C sources such as sucrose and tartaric acid as nutrients,when Aspergillus versicolor bacterial solution amount was 20%,with 10%sucrose or 7%tartaric acid as nutrients,the degradation rates of petroleum hydrocarbons in soil were 53.23%and 31.12%for 15 d,and 55.63%and 42.9%for 30 d,respectively.The CO₂ release from the naturally placed oil-contaminated soil was 22.28?31.83(m L·kg^-1)after 30 d of remediation,and the average CO₂ release from the sucrose remediation group was 174.59(m L·kg^-1),and the soil respiration intensity could be enhanced about 5 times.The SEM morphology showed that the pores of petroleum hydrocarbon-contaminated soil were clogged,and the pore structure of uncontaminated soil and remediated soil was loosened.Stimulation of Aspergillus versicolor with sucrose and glucose complex nutrients,for 30 d of restoration,significantly increased the efficiency of Aspergillus versicolor in degrading petroleum hydrocarbons,up to 76.1%in the soil.The degradation time of sucrose-stimulated fungi had less effect on its degradation effect,and the degradation effect of sucrose compounded with glucose stimulated strains was positively correlated with the degradation time,and the degradation rate could be as high as 72.5%after 5 weeks.Microbial diversity changed significantly before and after bioremediation,W1 was clean soil,W2 was motor oil contaminated soil,W3 was Aspergillus versicolor remediated soil,W4 was sucrose stimulated Aspergillus versicolor remediated soil,and W5 was sucrose compounded with glucose stimulated Aspergillus versicolor remediated soil,the removal effect of petroleum hydrocarbons in soil after three bioremediation treatments W3<W4<W5.For the fungal level,W2 and W1 fungal community richness is similar,fungal diversity W1>W2>W3>W4>W5,indicating that the better removal effect the more homogeneous fungal species,W2 dominant phylum is Ascomycota,W3,W4,W5 in the community structure increased by 99.64%,99.92%,99.81%,respectively,the dominant genus from Cladosporium changed to Aspergillus,indicating that the restoration of Aspergillus versicolor was effective;For the bacterial level,compared to W2,the abundance of W4 and W5 increased significantly,the abundance of W3 decreased,bacterial diversity W4>W5>W1>W2>W3,the dominant phyla in W1 and W2 were Firmicutes and Actinobacteiota,and the proportion of Actinobacteiota in W3,W4 and W5 increased to 40.92%,56.20%and 61.57%respectively,while the proportion of Firmicutes in W4 and W5 decreased sharply.Bacillus was still the dominant genus,but the proportion decreased to 8.15%and 9.35%,respectively,and another dominant genus Microbacterium was added,accounting for about 34%of the soil bacterial community in each restoration group.