【作者】 李明；

【导师】 董德明； 花修艺；

【作者基本信息】 吉林大学 ， 环境科学， 2014， 博士

【摘要】 昼夜变化是自然界的基本变化规律之一，光化学过程是污染物的环境行为中非常重要的一个环节。在自然水体环境中，溶解有机质（DOM）在光照条件下生成的活性氧（ROS）对有机污染物的降解等环境行为影响较大。此外，昼夜变化可通过改变藻类的新陈代谢进而使水体微环境（pH和DO等）发生周期变化，从而导致水体中重金属的浓度和形态发生周期性的显著改变，这对痕量金属的迁移转化、生物可利用性及最终归宿具有重要作用。藻类生理学的相关研究表明，新陈代谢（光合作用）过程除了可以生成溶解氧改变pH外，也可以生成ROS。然而，关于昼夜变化对自然水体中有机污染物影响的研究十分有限。自然水体生物膜，普遍存在于河流、湖泊、湿地等自然水体环境中的表层沉积物、沙石、岩石等各种固相物质表面上，微藻（硅藻、绿藻为主）是其重要的组分之一。所以，光照变化可能通过影响生物膜中藻类新陈代谢的变化（光合作用和呼吸作用）间接影响ROS的生成，进而影响污染物的环境行为。由于自然水体生物膜几乎含有天然水环境中所可能包含的绝大部分的物质成分和绝大部分的污染物行为，污染物在水-自然水体生物膜体系中的环境行为比单一的人工培养的藻类体系更能反映污染物在天然水环境中的行为。因此，非常有必要开展研究光照变化对自然水体生物膜与典型有机污染物间作用的影响及其机制，来了解光照变化对水环境中有机污染物迁移转化的影响，这有助于进一步认识有机污染物在自然界昼夜周期变化情况下的实际环境行为。本研究以实验室模拟为主要研究手段，通过构建水-自然水体生物膜体系作为模拟实验体系，选择十二烷基苯磺酸钠（DBS）为非挥发、非持久性的有机污染物代表，研究不同光照条件下，水-自然水体生物膜体系中DBS的降解规律和机制，具体包括：不同活性的生物膜存在时体系中DBS和过氧化氢（H2O2）的含量变化情况，来验证生物膜体系中H2O2的生成和DBS的降解；研究主要影响因素对模拟体系中H2O2的生成及其对DBS降解的影响；研究生物膜组分和典型离子对H2O2降解DBS的影响与机制；研究H2O2与其他ROS的关系及其对DBS降解的影响。在此基础上，分析总结光照对自然水体生物膜与典型污染物间作用的影响和机制，并进一步总结昼夜变化对水环境中有机污染物环境行为的影响规律。本论文在对生物膜活性对H2O2生成和DBS降解影响的研究中发现：在同样生物量的情况下，只有活性的生物膜体系中有生成H2O2，并且DBS浓度和TOC含量都明显降低。活性生物膜在光照和无光条件下，H2O2的生成量分别约为34.0μmol/L和17.2μmol/L，DBS含量分别减少了约85.2%和12.9%，TOC分别减少了约67.1%和10.9%。这说明光照和无光条件下，生物膜具有生物活性是生成H2O2的关键，光照是生物膜生成H2O2的重要影响因素，H2O2是DBS降解的原因之一。通过进一步的H2O2溶液体系实验，对比同一浓度的H2O2在光照和无光条件下对DBS降解的影响，验证了H2O2对DBS的降解作用。生物膜生成的H2O2对DBS的降解主要有两种方式：（1）H2O2可以直接氧化降解DBS；（2）H2O2转化生成ROS间接参与DBS的降解。生物膜也可能直接产生其他ROS参与DBS降解。此外，发现光照既可以促进生物膜生成H2O2，也可以使H2O2发生光化学反应促进DBS降解，这表明光照是生物膜生成H2O2和DBS降解的重要影响因素。在对生物膜形态和生物膜数量的研究中发现：光照或无光条件下，生物膜的形态和数量对H2O2的生成和DBS的降解都有影响。在光照条件下，生物膜的形态对生成H2O2和降解DBS的影响明显小于无光条件下。H2O2的生成量和DBS的降解量都与生物膜数量呈正比例增加。在溶解氧（2mg/L≤DO≤20mg/L）对生物膜生成H2O2和降解DBS影响的研究中发现：光照条件下，随着溶解氧含量的升高，H2O2的生成量和DBS的降解量也在升高，但是与溶解氧浓度呈非线性关系：在溶解氧浓度较低时其对H2O2生成和DBS降解的影响更显著。无光条件下，H2O2的生成量和DBS的降解量与溶解氧含量呈近似线性的关系。研究结果表明在光照和无光条件下，溶解氧都是生物膜生成H2O2和降解DBS的重要影响因素。溶解氧不但可以促进生物膜产生H2O2，可能还可以参与DBS降解的中间产物的氧化分解。对于水-生物膜体系中H2O2生成和DBS降解的机理，在O-2生成及其对H2O2的生成和Fe2+的释放的实验中发现：光照条件下生物膜可以产生O-2，并且对生物膜体系中H2+2O2的生成和Fe2+的释放具有显著的影响， O-2与H2O2的生成和Fe的释放都存在密切的联系。此外， O-+2和Fe2以及光照在一定程度上会促进H2O2转化生成其他ROS（如OH和1O2）。在H2O2溶液体系进行的生物膜组分和铁锰离子对H2O2降解DBS的影响实验结果表明：生物膜中的典型组分和铁锰离子（Fe2+、Fe3+和Mn2+）对H2O2降解DBS都有促进作用，特别是Fe2+存在时。所以，自然水体生物膜存在条件下，DBS的降解是多种原因共同作用的结果。但是本研究至少证明生物膜可以生成H2+2O2和Fe，那么在生物膜的表面附近或局部可能形成微观类Fenton体系生成ROS降解有机污染物。更多还原

【Abstract】 Diurnal rhythm is one of the basic laws of nature and photochemical process is avery important aspect of the pollutants environmental behavior. In natural waterenvironments, photochemical process can produce reactive oxygen species (ROS)which will have great impact on pollutants environmental behavior. The ROS innatural waters is usually generated by non-living substances dissolved organic matter(DOM) under illumination. In addition, diurnal rhythm periodically altersmicro-environmental parameters (pH and DO) by altering the metabolism of algae,which results in the periodically change of concentrations and forms of heavy metalsin waters, and this has important impact on migration and transformation,bioavailability and ultimate fate of trace metals. However, there are many organicpollutants in natural waters, but studies on the impact on diurnal rhythm of organicpollution in natural waters are very limited. Algal physiology studies indicate that themetabolism (photosynthesis) process can not only generate dissolved oxygen to alterpH, but also can generate ROS.Natural biofilms naturally exist on the surfaces of solid materials such as surfacesediment, sand, rocks and so on in rivers, lakes, wetlands and other natural waterenvironments. Therefore, illumination variation may affect the variation of themetabolism (photosynthesis and respiration) of algae in biofilms and indirectly affectthe generation of ROS, thereby affects pollutants environmental behavior. Sincebiofilms contain almost most of the material composition and pollutants behavior thatmay contain in natural waters environments. The pollutants environmental behavior inwater-biofilm system can better reflect the pollutants in natural water environmentalbehavior than in single artificial algae system. Therefore, it is necessary to carry on the studies on laws and mechanism of biofilms and typical organic pollutants underillumination variation to further understand the impact of illumination variation onmigration and transformation of organic pollutants in water environments, whichcontributes to a better understanding of the actual environmental behavior of organicpollutants under natural diurnal rhythm condition.In this study, the degradation laws and mechanism of sodium dodecyl benzenesulfonate (non-volatile and non-persistent DBS, used as a representative of degradableorganic pollutant) under different illumination conditions were investigated throughsimulation experiments and by the construction of water-biofilm system as a carrier.These include: effects of activity of natural biofilms on DBS and hydrogen peroxide(H2O2) concentration to verify whether the biofilm system can generate H2O2; mainfactors affecting H2O2generation and its impact on DBS degradation in simulationsystem; influences and mechanisms of biofilm components and typical ions on H2O2degradation; the relation between H2O2and other ROS, and its impact on DBSdegradation. On this basis, this paper will analyze and summarize the influence lawsand mechanisms of illumination on natural biofilms and typical pollutants, and furthersummarize the influence of diurnal rhythm laws on organic pollutants environmentalbehavior in water environments.In this study for the research on H2O2generation and DBS degradation, it isfound that under the same biomass condition, the biofilm system which has activitycan generate H2O2, and the concentrations of DBS and TOC are significantly reduced.The amount of H2O2generation was34.0μmol/L and17.2μmol/L, DBS leveldeclined85.2%and12.9%, TOC level declined67.1%and10.9%respectively underillumination and in darkness. It explains that biological activity is the key to H2O2generation and then DBS degradation under illumination and in darkness.Illumination is an important factor on biofilms generating H2O2, and H2O2is one ofthe reasons of DBS degradation. Through degradation of H2O2solution on DBSexperiment, it is verified the degradation effect of H2O2on DBS, and analysis resultsare: there are two main ways for H2O2generated by biofilms to degrade DBS:(1)H2O2can directly degrade DBS;(2) H2O2is likely to generate ROS and then indirectly degrade DBS. Biofilms may also generate other ROS to degrade DBS. Inaddition, illumination can not only promote biofilms to generate H2O2, but also havephotochemical reaction with H2O2and promote DBS degradation. Illumination is animportant factor of H2O2generation and DBS degradation.In the study of existing form and the amount of biofilms, it is found that bothexisting form and amount of biofilms affect H2O2generation and DBS degradationunder illumination and in darkness. Under illumination, existing form of biofilms hasless impact on H2O2generation and DBS degradation than that in darkness. Theamount of H2O2generation and DBS degradation are proportionally increased withthe increase of the amount of biofilms, and the increase amount is higher underillumination than that in darkness.For the study of the influences of dissolved oxygen (2mg/L≤DO≤20mg/L) on H2O2generation and DBS degradation, it is found that under illumination,the amount of H2O2generation and DBS degradation was nonlinear increased with theincreasing of DO concentration. DO is an important factor on H2O2generation andDBS degradation, especially in darkness. DO can not only promote biofilms togenerate H2O2, and affect the concentration of H2O2that have been generated, butalso maybe involved in the degradation process of DBS degradation intermediateproducts.The study of H2O2generation and DBS degradation mechanism in water-biofilmsystem combined with biofilms generating O-2and releasing Fe2+experiments andthe effects on H2O2generation found that: Biofilms can generate superoxide anionradicals (O-2), which has a significant effect on H2O2generation and Fe2+release andis closely linked to H2O2generation and Fe2+release, O-2. Fe2+and illumination willpartly promote H2O2to transform and generate other ROS (such as OH and1O2). Inthe H2O2solution experiments of biofilm components and iron and manganese ionson H2O2degrate DBS, it can be drawn that typical components and iron andmanganese ions (Fe2+、Fe3+and Mn2+) in biofilms will promote H2O2to degrade DBS,especially in the presence of Fe2+. So, DBS degradation in natural biofilms is theresult of various reasons. But this study proved that at least biofilms can generate H2O2and Fe2+, and then on the surface of or near the biofilms can form similarmicro-Fenton system to degrade organic.更多还原