随着现代工业不断的发展，土壤包气带中多环芳烃（PAHs）的沉积量逐年增加，严重威胁着土壤安全。光降解反应能够显著影响土壤中多环芳烃的迁移转化行为。它能够有效降低土壤表层中多环芳烃的含量，减少其向下迁移污染地下水源的可能。本论文以陕北风沙滩地区典型土壤类型风积沙为反应基质，多环芳烃—菲（Phe）为目标污染物进行光降解实验研究，在分析风积沙理化性质的基础上，查明了光源种类、菲的初始浓度、环境条件等因素对光降解反应的影响；建立了光降解的动力学模型；探讨了光降解机理、产物及路径。主要结论如下： （1）通过各影响因素对光降解的影响研究得到：①光源的种类会影响菲的光降解，其波段不同，Phe的降解效果也不同。相同条件下，紫外光（UVA、UVB、UVC）对Phe的光降解能力大小为UVC>UVA>UVB。②菲的降解率随着光源辐射强度的增强而增大；③三个紫外光照体系中，随着污染物初始浓度的增大，光降解率增加，达到一定浓度后，光降解率随着浓度的增加而减小。④光降解率随着pH值的增大而增加，碱性环境适于Phe在风积沙中的光降解。⑤光降解率随着温度的增高而增大。⑥风积沙的含水率越高，越有利于菲的光降解。⑦沙样中适当含量的腐殖酸能够促进Phe的光降解，但若含量高过一定浓度反而会起到抑制作用。 （2）菲在风积沙中的光降解过程符合一级动力学模型，UVA、UVB、UVC光源下的光解速率常数分别为0.204、0.121、0.645d-1。 （3）光降解机理分析结果表明，•O2-对风积沙中Phe的自然光降解起主要作用；光降解过程中苯环上的不饱和=C-H键被破坏。 （4）菲在风积沙中的降解路径可分为三种：①菲接受光照后变成化学活性更高的同分异构体—蒽，蒽发生氧化、加成等反应后逐步变成小分子化合物；②菲直接与氧自由基接触，在其9，10位发生氧化反应，再由大分子有机物逐步向小分子有机物转化；③菲的9，10位与有机质发生反应，接着与氧自由基反应形成含有羰基的化合物，再进一步转化为小分子有机物。 本研究结果进一步揭示了PAHs在土壤特别是风积沙表层的光降解转化过程，为利用光能降解土壤中多环芳烃有机污染物提供了理论依据，有助于深入理解PAHs在土壤包气带中的迁移、转化和归宿，且对利用光能或高级光氧化技术处理PAHs及类似有机污染物的污染问题具有指导意义。

With industrial development, the deposition of polycyclic aromatic hydrocarbons (PAHs) increased every year, which brings a serious threat to the safety of soil. Photodegradation reaction has an important influence on the migration behavior of PAHs in soil. It can reduce not only the content of PAHs in soil surface, but also reduce the risk of groundwater pollution. In this study, aeolian sand in blow-sand region of Northern Shaanxi was chosen as typical soil and phenanthrene (Phe) as typical pollutant of PAHs. The effects of light source, aeolian sand, initial concentration of pollutants and other environmental conditions were investigated and the photocatalytic degradation mechanism of Phe in Aeolian sand was established. In addition, explored the product and proposed reaction pathways of Phe in aeolian sand．The results obtained were as follows: （1）Research to the impact of various factors on photodegradation indicated: ① The type of light source would affect phenanthrene photodegradation. The Phe degradation effect was different due to different bands. Under the same conditions, the ability of Phe photodegradation of ultraviolet (UVA, UVB, UVC) was UVC> UVA> UVB. ② The rate of phenanthrene degradation increases as the light radiation intensity increases.③Among three UV lighting systems, the law of the impact of initial concentration of pollutents on photodegradation was substantially the same, that is, the degradation rate increased as the concentration increased; when up to a certain concentration, the rate decreased as the concentration increased.④ Photodegradation rate substantially increased with the increasing of pH value, which meant an alkaline environment was more suitable for Phe photodegradation in aeolian sand. ⑤ Phe degradation rate increased as the temperature increased. ⑥ The higher the moisture content of aeolian sand was, the higher the rate of phenanthrene photodegradation would be. ⑦ Appropriate amount of humid acid in aeolian sand could promote Phe photodegradation. However, if the concentration of humid acid was too high, it would suppress photodegradation. （2）The process of Phenanthrene photodegradation in aeolian sand met the first-order kinetics model. The photodegradation rate constant of Phe in UVA, UVB, UVC were 0.204、0.121、0.645d-1. （3）The analysis of photodegradation mechanism showed that •O2- played a major role in Phe degradation of natural light in aeolian sand. During the process of photodegradation, unsaturated carbon-hydrogen bond on benzene ring was destroyed. （4）Pathways of Phenanthrene degradation in aeolian sand can be divided into three types: ① Phe turned into an isomers—anthracene, which had higher chemical activity after receiving the light. It could not only conduct the addition reaction, but also could react with oxygen free radical and generate peroxides; then macromolecular compounds further transformed into small molecule organic compound.② Phe was oxidized directly by oxygen free radicals on its position 9,10 keys, and then transformed into small molecule organic compound. ③ The 9,10 keys of Phe firstly reacted with organic matter, then was oxidized by oxygen free radicals into carbonyl compounds, then further transformed into small molecule organic compound. This research further reveals the photodissociation process of PAHs in soil, especially the aeolian sand, which would deepen our comprehension on migration, conversion and ultimate destination of PAHs in unsaturated zone. Our study will also have a better scientific value and clinical significance to the degradation of organic pollutant by light energy or advanced light oxidation technology for future.