Effects Of Petroleum Hydrocarbon Pollution On Soil Water Repellency,saturated Water Conductivity And Water Retention Characteristics

Soil pollution by petroleum hydrocarbons will have an impact on the physical,chemical and biological properties of soil,especially because of the non-hydrophilic nature of petroleum hydrocarbons,petroleum hydrocarbons entering the soil may lead to soil water repellency,thus affecting the saturated water conductivity,water holding characteristics and water availability of the soil.However,there are few studies in this field.In this paper,petroleum hydrocarbon contaminated soil was prepared artificially,The change characteristics of soil water repellency,saturated water conductivity and water holding capacity after petroleum hydrocarbon pollution were studied,The main conclusions are as follows:（1）At low concentrations,the soil contaminated by crude oil and diesel oil did not show water repellency,however,when the concentration of petroleum hydrocarbons exceeds 10,000mg·kg^-1,with the increase of pollution concentration,the water-repellent grade of the soil increases,and the water repellency is enhanced.Soil contaminated with crude oil is more water-repellent than soil contaminated with diesel oil,moderate water repellency occurred when crude oil was contaminated by 20000 mg·kg^-1,while diesel oil was contaminated by 50000 mg·kg^-1.（2）The contamination of soil by petroleum hydrocarbons resulted in the decrease of soil saturated water conductivity,With the increase of diesel oil and crude oil pollution concentration,the soil saturation water conductivity decreases.Soil saturated water conductivity decreased from 0.140 mm·min^-1to 0.0625 mm·min^-1under crude oil pollution at mass concentration of 5000 mg·kg^-1to 100,000 mg·kg^-1,when the crude oil pollution concentration reaches 200,000 mg·kg^-1,it decreases to 0.05 mm·min^-1;When the same concentration of crude oil and diesel oil pollutes the soil,the saturated water conductivity of the oil-contaminated soil is lower,that is,the crude oil pollution has a greater impact on soil infiltration.（3）Due to the pollution of crude oil and diesel oil,the soil moisture characteristic curves gradually moved downward,and all of them were located at the lower part of the unpolluted soil curve,especially the crude oil pollution.The parametersθ_sandθ_rof the Van Genuchten model of water characteristic curve decreased exponentially with the increase of pollution concentration.Soilθ_svalue decreased from 32.47%to 28.97%after diesel oil pollution,soilθ_svalue decreased from 32.47%to 28.57%under crude oil pollution,and soil residual water contentθ_rdecreased from 8.33%to 3.95%after crude oil pollution.The value ofαdecreases as a power function,the n value increases with the logarithm of the pollution concentration.（4）The saturated water content,field water capacity and wilting water content of soil decreased with the increase of pollution degree,and the influence of crude oil was more significant.When the crude oil pollution concentration is as high as 200,000mg·kg^-1,the saturated water content of uncontaminated soil decreased from 32.36%to28.17%,the soil field water content was 16.44%,and the soil wilting water content decreased from 9.32%to 3.59%;The soil available water content of diesel oil and crude oil showed a U-shaped change pattern with the pollution concentration decreasing first and then rising.