【作者】 孙晓春；

【导师】 杨桂朋；

【作者基本信息】 中国海洋大学 ， 海洋化学， 2008， 硕士

【摘要】 海洋有机光化学是海洋化学的重要分支,并与海洋生物、海洋环境等学科密切相关。对海洋有机光化学进行系统深入的研究对进一步了解海洋中有机污染物的迁移变化规律具有重要的理论意义和实际意义。农药的光化学降解是农药在环境中分解、转化的重要途径之一。农药分子吸收光能,导致分子键断裂,发生直接或间接光解。因此,研究农药在海水中的光化学降解具有非常重要的意义,通过对农药的降解研究,推测其在环境中的降解途径,了解农药使用的安全性,并指导农药的使用和新农药的实际合成。本论文在已有科学研究的基础上,采用实验室模拟的方法,以两种有代表性的农药为研究对象,探讨了其在水环境中的光化学降解行为。通过仪器检测和实验分析,系统地研究了三唑酮和乐果的光降解反应。具体结果如下:1.三唑酮的光降解情况:(1) 300 W高压汞灯照射下,在所选取的实验条件下,三唑酮发生了光降解反应,且符合一级反应动力学行为。各种实验条件下速率常数(k)的变化范围为0.0027～0.0607 min-1。(2)反应影响因素:a.光源:太阳光照下,三唑酮在三种介质中的降解较慢。高压汞灯对光反应的激发效率明显高于天然日光,三唑酮能够发生明显地降解。而在黑暗条件下,三唑酮几乎不发生光降解反应。b.光强:三唑酮在500 W高压汞灯照射条件下比300 W高压汞灯照射条件下降解速率明显要快。c.溶液介质:三唑酮在去离子水中(DW: deionized water)光反应最快,人工海水(ASW: artificial seawater)与天然海水(NSW: natural seawater)相比,在人工海水中反应速率稍快。d.重金属离子:不同的重金属离子对不同的物质表现出不同的作用,本论文验证了五种重金属离子的存在影响了三唑酮的光降解反应。通过改变金属离子的浓度观察其对光反应的影响,证明了不同浓度的重金属离子对三唑酮光降解反应的作用有所不同。此外,实验还证明了重金属离子对农药光降解反应的影响是与溶液介质相互作用的结果。e.光敏剂:在不同介质中光敏剂对三唑酮的光降解都表现出促进作用,促进作用大小依反应物及反应溶液介质而定。(3) pH测定:对三唑酮光降解过程中反应液进行pH检测,发现在不同介质中pH均表现为降低趋势,但降低的程度及表现各不相同。(4)产物检测:用GC-MS对三唑酮的降解产物进行检测,共检测出三种产物以及一种未知物质。2.乐果的光降解情况:(1)在60 min内,300 W高压汞灯照射下乐果几乎不发生降解。采用H2O2为催化剂,高压汞灯照射下乐果可发生迅速降解,在所选取的实验条件下,乐果的降解符合一级反应动力学行为。各种实验条件下速率常数(k)的变化范围为0.0213～0.0744 min-1。(2)影响因素包括:a. H2O2用量:H2O2的最佳用量为2.8 g/L。b.溶液介质:乐果在NSW中降解最慢,ASW与去DW比较,在ASW中略快。c.重金属离子:在NSW中,五种重金属离子表现出不同的作用。d.硝酸盐及亚硝酸盐:硝酸盐及亚硝酸盐的添加对乐果的光解均表现出抑制作用,且猝灭效应强度随硝酸盐及亚硝酸盐添加浓度的增加而增强。综上所述,本论文针对海水中两种农药,对其光降解和光催化降解的反应情况、动力学及影响因素等方面进行研究,取得出了一系列研究结果。根据实验模拟结果,我们可以更好地了解天然海洋环境中该类农药的降解情况,为海洋环境中农药污染的治理提供重要的理论依据。更多还原

【Abstract】 Marine organic photochemistry (MOP), as one of the important branches of marine chemistry, has a close relationship with many marine subjects such as marine biology and marine environmental science. The comprehensive study on MOP is of realistic significance for further understanding the removal patterns of organic pollutants in the ocean.The photodegradation of pesticides is an important pathway for their decomposition and transformation in natural environment. Pesticide molecules can absorb the light energy and be photodegraded themselves (direct degradation).The degradation may also be sensitized by other compounds, which referred to indirect degradation. It is of great significance to study the photodegradation of pesticides in seawater, because through the study, we can get the products and pathway for their photodegradation in natural environment and realize the safety of pesticides in order to instruct the use of pesticides and synthesize new products.Based on the former research work, the thesis focused on the photochemical degradation reaction of two representative pesticides in seawater by the simulative method in laboratory. Through instrument detection and experimental analysis, we systematically studied the photochemical degradation of triadimefon and rogor and obtained the following results:1. Photochemical degradation of triadimefon(1) Triadimefon could be significantly degraded under the irradiation of 300 W high pressure mercury lamp and showed the first-order reaction kinetic behavior. Under the different experimental conditions,the rate constants (k) of triadimefon varied from 0.0027 to 0.0607 min-1.(2) Many factors in the experiments would influence the photodegradation: a. Light source: Triadimefon was photodegraded a little under the irradiation of sunlight while it could be significantly degraded under the irradiation of 300 W high pressure mercury lamp. However, no photolysis of triadimefon was observed in the dark.b. Light intensity: The photolysis rate of triadimefon under 500 W high pressure mercury lamp was faster than that under 300 W high pressure mercury lamp, showing that light intensity is an important factor for the photodegradation of triadimefon.c. Aquatic media: The photodegradation of triadimefon in deionized water was the fastest among the three media-deionized water, natural seawater and artificial seawater. The photodegradation of triadimefon in artificial seawater was a little faster than that in natural seawater.d. Heavy metal ions: In all the reactions, different metal ions in different reaction systems displayed different effects. The results were obtained by changing the concentrations of five heavy metal ions in triadimefon solution. The effects of heavy metal ions were caused mainly by the interaction between ions and aquatic media.e. Photosensitizer: The selected photosensitizer - acetone could accelerate the reactions of triadimefon and the influence degree was determined by reactant and aquatic media.(3) pH: The pH of solutions reduced in all kinds of systems when pH was measured during the process of photodegradation of triadimefon, while the effects were different for the different systems.(4) Identification of degradation products: Three products have been identified using GC-MS detection. However, the fourth product, probably being the intermediate product of triadimefon, was not identified because of the lack of an authentic standard sample.2. Photochemical degradation of rogor(1) Rogor was hardly degraded under the irradiation of 300 W high pressure mercury lamp within 60 min, but was quickly degraded when H2O2 was added into the solution as a catalyst. Under the different experimental conditions, the photolysis of rogor showed the first-order reaction kinetic behavior and the rate constants (k) of rogor varied from 0.0213 to 0.0744 min-1.(2) Many factors in the experiments would influence the photodegradation:a. Aquatic media: The reaction in natural seawater was the slowest compared with the b. Amount of H2O2: The optimum dosage of H2O2 was 2.8 g/L.c. Heavy metal ions: In seawater, five metal ions (such as Cu2+, Zn2+, Cd2+, Hg2+, Pb2+) displayed different effects.d. Nitrate and nitrite: Both nitrate and nitrite showed photoquenching effects on degradation of rogor and the quenching degree was enhanced with increasing concentration of nitrate and nitrite.In brief, for the two pesticides in seawater, a series of results have been obtained in the respects of photochemical degradation, photocatalytic degradation, kinetic behavior and the factors influencing them. Based on the experimental results, we can have a further understanding of the photodegradation situations of these two kinds of pesticides in the marine environment.更多还原