Study On Remediation Of Petroleum Hydrocarbon Contaminated Soil By Biotechnology Fulvic Acid(BFA)

As an very important energy material,petroleum is widely mined and transported,which often produecd leakage and other pollution.Petroleum hydrocarbon pollutants contain a variety of alkanes and aromatic hydrocarbons,which are extremely harmful to the environment.This paper selected petroleum hydrocarbon contaminated soi as the research object,the soil culture experiment was carried out by controlling the petroleum hydrocarbon concentration and Biotechnology fulvic acid（BFA）mass fraction.The remediation of petroleum hydrocarbon contaminated soil by adding BFA alone and by adding BFA+oxidants were studied.The TPH content,pH,EC,soil aggregate structure and other indicators of soil samples at different intervals after the experimental treatment were determined and analyzed.The main conclusions are as follows:1.The remediation of petroleum hydrocarbon contaminated soil by BFA alone（1）The rate of TPH degradation increased by adding BFA alone,and it was better for low-concentration petroleum contaminated soil.Overall,the effect of 5%BFA is better than 2%BFA.After adding 2%BFA,the highest rates of TPH degradation for high-concentration and low-concentration petroleum contaminated soils was 34.1%and 60.3%,respectively.After adding 5%BFA,the highest rates reached 49.5%and70.2%respectively.（2）BFA alone caused Soil acidification in short term（pH is reduced to 6.3⁶.8）,but it will return to neutral level as time increases,which will not affect the acidity and alkalinity of the soil in the long time.（3）BFA increased soil conductivity in short term,but decreased over time.Adding5%BFA will have the risk of soil salinization.The EC values in the 2%BFA group belowed in 2.0 ms/cm in the early and late stages of the experiment.2.The remediation of petroleum hydrocarbon contaminated soil by adding BFA+oxidants（1）H₂O₂+BFA and Fenton+BFA experimental groups had better degradation rates than the control group for the high-concentration petroleum hydrocarbon contaminated soil,and the highest TPH degradation rates were 35.2%and 36.6%,respectively.However,there was no significant difference compared to the addition of2%BFA alone.It may be that the H₂O₂ concentration is high and most of it consumed by soil organic matter.In addition,H₂O₂+BFA and Fenton+BFA have little effect on low-concentration petroleum hydrocarbon contaminated soil.（2）H₂O₂+BFA and Fenton+BFA groups caused soil acidification in different degrees in the short term,but not affected in long term.After 5 days of soil culture experiments,the pH value of H₂O₂+BFA soil sample>7.0,and Fenton+BFA>6.0.（3）Both H₂O₂+BFA and Fenton+BFA increased soil electrical conductivity,but did not exceed 2.0ms/cm during the culture period.And long-term effects on soil conductivity need to be further tested.（4）The rate of TPH degradation not increased by adding Na₂S₂O₈+BFA in alkaline soil,and had opposite effect,which may be related to the initial pH value of the soil.The soil pH value recovered slowly,and 5%BFA+Na₂S₂O₈ group was more acidic（pH<5.0）.Soil samples all reached a moderate degree of salinization because of Na₂S₂O₈,BFA did not lead to a re-increase in soil conductivity.3.Effect of BFA on the structure of soil aggregates（1）The aggregates size of soil aggregates with BFA alone were concentrated to>10mm or 3⁵ mm,and the effect of 5%BFA is more obvious than 2%BFA.BFA alone also enhanced the water stability of soil aggregates,with a significant increase in the proportion of water-stable aggregates above 0.5 mm.（2）H₂O₂+BFA increased the proportion of soil aggregates that>3mm in high concentrations petroleum contaminated soil significantly,and the optimization effect is obvious;The proportion of soil aggregate of 0.25²mm was increased in low-concentration petroleum hydrocarbon contaminated soil.Fenton+BFA has increased the proportion of soil aggregates that are 5¹0mm in high-concentration petroleum contaminated soil and 0.25²mm in low-concentration petroleum contaminated soil.And the combination of 2%BFA and oxidant improved the water stability of soil aggregates.In conclusion,both the degradation of petroleum hydrocarbon and soil structure improved by adding BFA,which has lower cost and can provide reference for the remediation of organic pollution such as petroleum hydrocarbons in farmland.The cost of 2%BFA and the risk of salinization are lower,H₂O₂+BFA and Fenton+BFA are suitable for high concentration of petroleum hydrocarbon contaminated soil.