Study On The Improvement Effect Of Common Crop Wastes On Petroleum Hydrocarbon Contaminated Soil

Considering that it wasdifficult to treat the loess contaminated by petroleum hydrocarbon, this thesis chose the agricultural wastes — walnut shell, corn cob, soybean straw and wheat straw as soil conditioners to explore their improvement effects on loessial soil. Through 120 days’indoor decomposition and analysis of dynamic changes of various soil properties and their relationships with oil length, the principal component function model was set up to confirm the optimal conditioner for soil improvement on the basis of data processing of principal component analysis(PCA) and SPSS software. The results showed as follows:(1)Choosing the petroleum ether as extraction agent to detect the content of petroleum hydrocarbon in loessial soil by gravimetric method, the study found that there was an obvious linear relation between actual value and measured value, namely Y=0.63814+1.39684*X(R2=0.99416) and the calculated accuracy rate of oil length was up to above 94% with the deviation value of 3.27% relative to the standard value, which indicated this detection method had a better reproducibility by using petroleum ether to extract the content of petroleum hydrocarbon in loessial soil.(2) Compared with blank control group, adopting walnut shell, corn cob, soybean straw and wheat straw can decrease the oil length inordinately(13.59%,17.85%,27.38%,15.21%), lower pH values(0.35,0.56,0.46,0.45), promote soil respiration(66.32%, 216.94%,1874.17%,159.71%) and facilitate alkaline phosphatase activity(64.21%,81.47%,140.25%,147.69%). Meanwhile, adding corn cob, soybean straw and wheat straw simultaneously to the soil can promote invertase activity (8.89%,117.06%,3.08%) and soil catalase activity (1.77%,40.72%,1.10%); adding walnut shell merely to the soil can inhibit invertase activity (-9.44%) and soil catalase activity (-3.03%); additionally, adding the soybean straw only to the soil can accelerate urease activity(-31.15%). However, adding walnut shell, corn cob and wheat straw simultaneously can inhibit urease activity (-22.16%,-18.03%,-13.62%).(3)With the decreasing oil length in the soil, pH value and the urease activity decreased, oppositely, the soil respiration and the alkaline phosphatase activity increased by adding walnut shell, soybean straw and wheat straw simultaneously to the soil. The invertase activity which strengthened by adding corn cob, soybean straw and wheat straw to the soil, however, lowered in the walnut shell-added soil. The catalase activity increased in the soil added by soybean straw and decreased in the soil added by walnut shell, corn cob, wheat straw oppositely.(4) Using the SPSS software to acquire the aggregative principal component function model Y=0.61712 Y1+0.18307 Y2+ 0.15805Y3, which indicated:soybean straw(Y=2.762)>corn cob(Y= 0.360)>wheat straw(Y=-0.048)>walnut shell(Y=-1.175)>blank group(Y=-1.897). The principal component analy sis(PC A) showed that all of these 4 agricultural wastes were able to improve the soil, in which the soybean straw and corn cob can obviously promote loessial soil improvement contaminated by petroleum hydrocarbon.