【作者】 李智冬；

【导师】 全燮；

【作者基本信息】 大连理工大学 ， 环境科学， 2007， 硕士

【摘要】 为了了解土壤中石油类污染物的光化学转化过程，深入探索石油类污染物在土壤-水-气相间的迁移转化规律及生态风险，本文以某种实际石油为反应基质，模拟自然环境条件，考察石油在土壤表面的光化学行为。主要研究工作如下：(1)将传统的土壤薄层光化学实验方法进行一定的改进，进行密封处理，研究石油在土壤表面的光化学行为。结果表明，氙灯照射下，土壤表面石油发生了光化学转化。考察了土壤中的初始含油量、土壤类型和土壤pH值对土壤表面石油光化学反应的影响。含油量在较低范围内变化时，对其光降解速率的影响不大，但当土壤的含油量很高时，其光降解速率明显变慢；土壤的有机质含量越高，石油在土壤表面的光降解速率越慢；土壤pH值对于石油的光降解过程没有显著的影响。不同实验条件下，石油在60h的光反应期间内能较好的遵循准一级反应动力学。(2)通过紫外可见分光光度法、红外分光光度法和气相色谱法分别对土壤表面石油的光降解过程进行定量分析，考察石油中不同组分的光降解规律。紫外可见分光光度法主要反映的是芳香烃组分的光降解规律；红外分光光度法反映的是总石油烃的光降解规律；气相色谱法主要反映的是饱和烃组分的光降解规律。它们测定的石油光转化率依次降低，此结果表明，石油中的芳香烃组分较饱和烃组分更易进行光降解反应。(3)选择石油饱和烃和芳香烃的代表性组分正十六烷和蒽，考察典型石油烃在土壤表面的光化学过程，有助于推测石油组分的光降解规律。光照60 h土壤表面正十六烷的光转化率明显低于蒽的光转化率。此结果也表明，石油中的芳香烃组分更容易发生光化学转化，且正十六烷的光降解速率大于实际石油中饱和烃总体的光降解速率，蒽的光降解速率与实际石油中芳香烃的光降解速率较为一致。(4)通过紫外可见分光光度法、气相色谱、傅立叶红外光谱、气-质联用对石油的光降解演变规律进行定性分析，考察石油在土壤表面的光化学反应规律。结果表明，土壤萃取液中石油的UV-Vis吸收峰形保持相对不变，但吸收强度发生变化；光照后芳香烃组分的大部分色谱峰有明显降低或消失，低碳数的饱和烃相对含量提高；利用正构烷烃标准系列物可直接对照定性；光照60 h后土壤萃取液的红外谱图中出现一个比较明显的羰基吸收峰，说明石油在光降解过程中逐渐发生氧化。研究结果表明，光氧化是石油光化学的一个重要降解机理，石油的光氧化产物具有更高的生态风险。更多还原

【Abstract】 To understand photochemical transformation of petroleum pollutants in soil,photoreactions of crude oil on soil surface in simulated natural conditions were studied, whichis available to investigate its transfer and transformation regulations among the soil-water-airphases as well as its ecological risks. The main work is as follows:（1） Photoreaction experiments of petroleum on soil surface were operated according tothe amended classical approach which effectively reduces the volatilization loss. The resultsshow that photoreactions of petroleum occur on soil surface under xenon light exposure.The influence of the initial oil concentration in soil, soil types and pH on photoreactionof petroleum was investigated. Changes in loWer oil concentrations affect the photochemicalprocesses of petroleum slightly. However, the higher oil concentration reduces thephotoreaction rate distinctly. The photolysis rate of petroleum on soil surface decreases whenthe content of organic matter in soil increases. Different soil pH results in similar reactionrates of petroleum. Kinetic analyses illustrate that photochemical degradation of petroleum onsoil surface, in the initial 60 h, follows pseudo first-order kinetics well under differentexperimental conditions.（2） Photolytic regulations of different petroleum fractions were investigated throughvarious quantitative analyses including UV-Visible, IR Spectrometer and GasChromatography.UV-Vis Spectrometer mostly reflects the photolytic processes of aromatic hydrocarbonswith the highest phototransformation ratio of petroleum. IR Spectrometer responds totalpetroleum hydrocarbons with the medium phototransformation ratio. The lowestphototransformation ratio of petroleum is determined by GC-FID, which reveals thephotochemical rules of saturated hydrocarbons. These results indicate that aromatichydrocarbons of petroleum are readier to photodegrade than saturated ones.（3） Two petroleum hydrocarbons, hexadecane and anthracene, were selected asrepresentative compounds of saturated and aromatic hydrocarbons and then photoreactions oftypical petroleum hydrocarbons were evaluated to speculate on photolytic regulations ofdifferent petroleum components.After 60 h irradiation, the phototransformation ratio of hexadecane on the soil surface islower than that of anthracene obviously. This result also reveals that it is easier for aromatichydrocarbons to degrade under irradiation than saturated ones. In addition, the photolysis rate of hexadecane is higher than that of the whole saturated hydrocarbons in crude oil.Furthermore, the photolysis rate of anthracene is consistent with that of the whole aromatichydrocarbons in petroleum.（4） UV-Vis, GC-FID, FTIR and GC-MS were used for the characterization of petroleumhydrocarbons in the photochemical processes to review phototransformation regulations ofpetroleum on soil surface.Experimental results indicate that absorption peak shapes of the extract from soil almostremain the same in UV-Vis Spectra, but the peak intensities change. GC-FID analyses showthat, after 50 h irradiation, most chromatogram peaks of aromatics are weakened or disappear.Moreover, the content of saturated hydrocarbons with longer chain decreases, while theproportion of shorter chain ones increases slightly. In addition, direct comparison between.unknown compounds and the standard series of n-C₁₀～n-C₄₄ is performed for qualitativeanalysis. After 60 h photolysis, the appearance of carbonyl compounds in FTIR spectra of theextract from soil demonstrates that petroleum is gradually oxidized in the photolytic process.The results demonstrate that photooxidation is one of the important photodegradationmechanisms of petroleum, and the photooxidation products of petroleum exhibit moreecological risks.更多还原