Vegetable oil has the ability to extract polycyclic aromatic hydrocarbons(PAHs)from contaminated sandy soil for a remediation purpose,with some of the oil remaining in the soil.Although most of the PAHs were removed,the risk of residue oil in the soil was not known.The objective of this study was to evaluate the effects of the vegetable oil residue on higher plant growth and sandy soil properties after soil extraction for a better understanding of the soil remediation.Addition of sunflower oil and column experiment were performed on a PAH contaminated soil and/or a control soil,respectively.Soils were incubated for 90 d,and soil pH was measured during the soil incubation.Higher plant growth bioassays with Avena sativa L.(oat)and Brassica rapa L.(turnip)were performed after the incubation,and then soil organic carbon contents were measured.The results show that both the nutrient amendment and the sunflower oil degradation resulted in the decrease of soil pH.When these two process worked together,their effects were counteracted due to the consumption of the nutrients and oil removal,resulting in different pH profiles.Growth of A.sativa was adversely affected by the sunflower oil,and the nutrient amendments stimulated the A.sativa growth significantly.B.rapa was more sensitive to the sunflower oil than A.sativa.Only 1%sunflower oil addition plus nutrient amendment stimulated B.rapa growth.All the other treatments on B. rapa inhibited its growth significantly.The degradation of the sunflower oil in the soils was proved by the soil organic carbon content.
Solubilizing experiments were carried out to evaluate the ability of biodiesel to remove polycyclic aromatic hydrocarbons(PAHs)from highly contaminated manufactured gas plant(MGP)and PAHs spiked soils with hydroxypropyl-β-cyclodextrin(HPCD)and tween 80 as comparisons.Biodiesel displayed the highest solubilities of phenanthrene(420.7 mg·L^(-1)),pyrene(541.0 mg·L^(-1)),and benzo(a)pyrene(436.3 mg·L^(-1)).These corresponded to several fold increases relative to 10%HPCD and tween 80.Biodiesel showed a good efficiency for PAH removal from the spiked and MGP soils for both low molecular weight and high molecular weight PAHs at high concentrations.Biodiesel was the best agent for PAH removal from the spiked soils as compared with HPCD and tween 80;as over 77.9%of individual PAH were removed by biodiesel.Tween 80 also showed comparable capability with biodiesel for PAH solubilization at a concentration of 10%for the spiked soils.Biodiesel solubilized a wider range of PAHs as compared to HPCD and tween 80 for the MPG soils.At PAH concentrations of 229.6 and 996.9 mg·kg^(-1),biodiesel showed obvious advantage over the 10%HPCD and tween 80,because it removed higher than 80%of total PAH.In this study,a significant difference between PAH removals from the spiked and field MGP soils was observed;PAH removals from the MGP soil by HPCD and tween 80 were much lower than those from the spiked soil.These results demonstrate that the potential for utilizing biodiesel for remediation of highly PAH-contaminated soil has been established.
Jinbao WUZongqiang GONGLiyan ZHENGYanli YIJinghua JINXiaojun LIPeijun LI
