| With the continuous increase of oil exploitation and usage in China,the environmental pollution caused by leakage accidents caused by various improper operations in the process of oil transportation,processing and storage is becoming more and more serious.When crude oil enters the soil,it will block soil pores,affect soil water repellency,change soil physical and chemical properties,and affect soil water movement.Oil pollution will also reduce the content of available phosphorus and nitrogen in the soil,and some substances in the oil will stick to the root system of plants,hindering the respiration and water absorption of the root system,and affecting the growth of plants.Soil water infiltration and evaporation determine the level of soil water content.The effect of crude oil pollution on soil water process is directly related to the phytoremediation process.In this study,the effects of different crude oil pollution levels(0%,0.5%,1%,2%,4%)on the infiltration and evaporation process of loess soil and aeolian sand soil with different texture were simulated by indoor soil column.Ryegrass pot experiment was used to treat the oil-contaminated soil at five water levels: according to the water content of unpolluted soil 90%±3%,75%±3%,60%±3%,45%±3%,30%±3%,to study the effects of different water control on plant growth in oil-contaminated soil.The main results of this study are as follows:(1)The soil wetting front speed and infiltration rate of the two soils decreased with the increasing crude oil content.The wetting front of 4% reached the bottom of the soil column needed the longest time,and was 4 times,47 times longer than that of0% for Loessial soil and Aeolian sandy soil,respectively.The cumulative infiltration of Loessial soil decreased with the increasing crude oil content,while it increased to the max and then decreased as the crude oil content increased in Aeolian sandy soil.The cumulative infiltration curves of Aeolian sandy soil with high contents(2%,4%)crude oil presented "up-tail" phenomenon.Kostiakov infiltration model and Philip infiltration model could better fit the infiltration process than Green-Ampt model for Loessial soil with different crude oil content,however,the two models could only well fit the infiltration process for Aeolian sandy soil with low content of crude oil(0%,0.5%,1%).(2)With the increase of crude oil content,the ratio of daily evaporation to atmospheric evaporation and cumulative evaporation decreased for both soils.With the passage of evaporation time,the relative percentage value(cumulative evaporation of crude oil treatment-cumulative evaporation of control treatment)/cumulative evaporation of control treatment for loess soil with different crude oil pollution decreased gradually.The relative percentage of Aeolian soil polluted by different crude oil decreases gradually at low concentration and increases gradually at high concentration.For Black and Rose evaporation models,Rose evaporation model has better fitting effect on the evaporation process of oil-contaminated soil than Black evaporation model,which can more accurately reflect the change of soil cumulative evaporation with time under the condition of oil-polluted soil.(3)With the increase of crude oil concentration,the inhibition effect of crude oil on the growth of Lolium multiflorum was gradually enhanced,and the plant height,fresh weight and chlorophyll of Lolium multiflorum decreased.The higher the crude oil concentration was,the slower the growth was.With the increase of water control,the plant height,fresh weight and relative chlorophyll content of Lolium multiflorum increased,indicating that the increase of water content could promote the growth of Lolium multiflorum in crude oil contaminated soil and increase the biomass of Lolium multiflorum.With the increase of crude oil concentration,the total N,P and K content of Lolium multiflorum decreased,and crude oil had inhibitory effect on the absorption of N,P and K of Lolium multiflorum.The increase of water content promoted the metabolic activity of the plant and increased the content of N,P and K in the plant,thus promoting the growth of the plant.However,its promotion effect is related to soil properties and crude oil pollution degree. |
