腐植酸作用下γ-HCH在冰和雪中的光转化
发布时间：2018-07-25 11:05
【摘要】：光化学反应是有机污染物在环境中迁移转化的重要途径之一。腐植酸作为天然光敏剂能够促进有机污染物发生间接光转化反应,对于有机污染物的迁移、转化和归宿都有着非常重要的影响。同时在全球气候作用下,冰雪已经成为持续性有机污染物的重要积累场所,冰雪中的持久性有机污染物及其降解产生的二次污染物已对冰雪覆盖地区环境产生了重要影响。因此,对于腐植酸存在下冰雪中有机污染物光化学反应的研究至关重要。本文拟通过添加腐植酸(Humic Acid,简称HA),选取典型有机氯农药γ-Hexachlorocyclohexane(简称γ-HCH)为目标污染物,选用80 W高压汞灯作为光源(λ(?)280 nm),研究HA存在情况下冰雪体系中有机污染物的光转化规律,进一步揭示环境中有机污染物在自然冰雪环境中的迁移转化机制,为温带及寒带地区污染控制对策的制定提供理论依据。研究结果表明： (1)水、冰以及雪中γ-HCH的光转化率：雪冰相水相。这是由于在冰相中存在冷冻浓缩效应及在结冰过程中溶解氧对γ-HCH的抑制作用减缓,使得冰中γ-HCH的光转化率大于水中；雪中γ-HCH的光转化率大于冰中是由于雪拥有更大的比表面积以及类似液体层(LLL层)。 (2)研究了冰相中γ-HCH初始浓度、HA浓度、盐离子浓度、pH、Fe3+、NO2及N03-、比表面积对γ-HCH的光转化率的影响。γ-HCH初始浓度、HA浓度对γ-HCH的光转化率呈现低浓度促进、高浓度抑制的现象；盐离子浓度、pH、Fe3+、NO2及N03-、比表面积对γ-HCH的光转化率均有促进作用。(3)研究了雪中盐离子浓度、pH、Fe3+对γ-HCH的光转化率的影响。与冰相中盐离子浓度对γ-HCH光转化率的影响相比,雪中盐离子浓度对γ-HCH光转化率影响较小,这主要是由于雪中的LLL层要比冰中的LLL层厚,已经有足够的γ-HCH进入到LLL层中,不会带来γ-HCH光转化率发生更大的变化；pH对γ-HCH光转化率的影响结果与冰中所得的结果相似；Fe3+低浓度时就出现了抑制现象,这可能是由于γ-HCH在雪中的光转化反应比冰中的反应要快,对于Fe3+抑制性的响应也要更加灵敏。(4)冰相中HA通过产生单线态氧(1O2)、羟基自由基(·OH)及三重激发态(HA*)加速γ-HCH的光转化。 (5)自然光照下,冰样中γ-HCH的光转化率和实验室模拟光照下γ-HCH的光转化率基本保持一致,然而,雪样中γ-HCH的光转化率要比实验室模拟光照下γ-HCH的光转化率低。 (6)HA存在下γ-HCH的光转化产物主要是五氯环己烯、邻二氯苯和间二氯苯、一氯苯,光转化过程中1O2通过消耗中间产物间接加速了γ-HCH的光转化过程。
[Abstract]:Photochemical reaction is one of the important ways to transfer and transform organic pollutants in the environment. Humic acid, as a natural Guang Min agent, can promote the indirect photoconversion of organic pollutants and play an important role in the migration, transformation and fate of organic pollutants. At the same time, under the action of global climate, ice and snow has become an important accumulation of persistent organic pollutants, the persistent organic pollutants in snow and ice and the secondary pollutants produced by their degradation have had an important impact on the environment of snow and ice covered areas. Therefore, it is very important to study the photochemical reaction of organic pollutants in ice and snow in the presence of humic acid. In this paper, a typical organochlorine pesticide 纬 -Hexachlorocyclohexane (纬 -HCH) was selected as the target pollutant by adding humic acid (Humic Acid, for short, and 80 W high pressure mercury lamp was chosen as the light source (位 280 nm),) to study the phototransformation of organic pollutants in ice and snow system in the presence of HA. The migration and transformation mechanism of organic pollutants in the natural ice and snow environment is further revealed, which provides a theoretical basis for the formulation of pollution control measures in temperate and cold regions. The results show that: (1) the light conversion of 纬 -HCH in water, ice and snow: the water phase of snow ice. This is due to the freezing concentration effect in ice phase and the inhibition of dissolved oxygen on 纬 -HCH in ice, which makes the light conversion rate of 纬 -HCH in ice larger than that in water. The light conversion of 纬 -HCH in snow is higher than that in ice because the snow has a larger specific surface area and similar liquid layer (LLL layer). (2) the effects of the initial concentration of 纬 -HCH in ice phase, the concentration of HA, the concentration of salt ion, the pH of Fe _ 3O _ 2 and N _ 03-and the specific surface area on the photoconversion rate of 纬 -HCH were studied. The initial concentration of 纬 -HCH and HA concentration increased the photoconversion rate of 纬 -HCH at low concentration and inhibited it at high concentration; The effect of salt ion concentration (pH = Fe _ 3O _ 2 and N _ 03-H _ 2O _ 3) and specific surface area on the photoconversion of 纬 -HCH was studied. (3) the effect of salt ion concentration (pH = Fe _ 3) on the photoconversion of 纬 -HCH was studied. Compared with the effect of salt ion concentration in ice phase on the light conversion of 纬 -HCH, the effect of salt ion concentration in snow on the light conversion of 纬 -HCH is less, which is mainly due to the fact that the LLL layer in snow is thicker than the LLL layer in ice, and enough 纬 -HCH has already entered the LLL layer. The effect of pH on the light conversion rate of 纬 -HCH is similar to that obtained in ice. This may be due to the fact that the photoconversion of 纬 -HCH in snow is faster than that in ice, and the response to the inhibition of Fe3 is more sensitive. (4) HA in ice phase accelerates the photoconversion of 纬 -HCH by producing monolinear oxygen (1O2), hydroxyl radical (OH) and triple excited state (HA*). (5) the light conversion rate of 纬 -HCH in ice samples was basically the same as that of 纬 -HCH under simulated light. However, the light conversion rate of 纬 -HCH in snow samples was lower than that in simulated illumination in laboratory. (6) in the presence of HA, the photoconversion products of 纬 -HCH were mainly pentachlorocyclohexene, o-dichlorobenzene and m-dichlorobenzene, and monochlorobenzene. 1O2 indirectly accelerated the photoconversion process of 纬 -HCH by consuming intermediate products.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X131
本文编号：2143633
[Abstract]:Photochemical reaction is one of the important ways to transfer and transform organic pollutants in the environment. Humic acid, as a natural Guang Min agent, can promote the indirect photoconversion of organic pollutants and play an important role in the migration, transformation and fate of organic pollutants. At the same time, under the action of global climate, ice and snow has become an important accumulation of persistent organic pollutants, the persistent organic pollutants in snow and ice and the secondary pollutants produced by their degradation have had an important impact on the environment of snow and ice covered areas. Therefore, it is very important to study the photochemical reaction of organic pollutants in ice and snow in the presence of humic acid. In this paper, a typical organochlorine pesticide 纬 -Hexachlorocyclohexane (纬 -HCH) was selected as the target pollutant by adding humic acid (Humic Acid, for short, and 80 W high pressure mercury lamp was chosen as the light source (位 280 nm),) to study the phototransformation of organic pollutants in ice and snow system in the presence of HA. The migration and transformation mechanism of organic pollutants in the natural ice and snow environment is further revealed, which provides a theoretical basis for the formulation of pollution control measures in temperate and cold regions. The results show that: (1) the light conversion of 纬 -HCH in water, ice and snow: the water phase of snow ice. This is due to the freezing concentration effect in ice phase and the inhibition of dissolved oxygen on 纬 -HCH in ice, which makes the light conversion rate of 纬 -HCH in ice larger than that in water. The light conversion of 纬 -HCH in snow is higher than that in ice because the snow has a larger specific surface area and similar liquid layer (LLL layer). (2) the effects of the initial concentration of 纬 -HCH in ice phase, the concentration of HA, the concentration of salt ion, the pH of Fe _ 3O _ 2 and N _ 03-and the specific surface area on the photoconversion rate of 纬 -HCH were studied. The initial concentration of 纬 -HCH and HA concentration increased the photoconversion rate of 纬 -HCH at low concentration and inhibited it at high concentration; The effect of salt ion concentration (pH = Fe _ 3O _ 2 and N _ 03-H _ 2O _ 3) and specific surface area on the photoconversion of 纬 -HCH was studied. (3) the effect of salt ion concentration (pH = Fe _ 3) on the photoconversion of 纬 -HCH was studied. Compared with the effect of salt ion concentration in ice phase on the light conversion of 纬 -HCH, the effect of salt ion concentration in snow on the light conversion of 纬 -HCH is less, which is mainly due to the fact that the LLL layer in snow is thicker than the LLL layer in ice, and enough 纬 -HCH has already entered the LLL layer. The effect of pH on the light conversion rate of 纬 -HCH is similar to that obtained in ice. This may be due to the fact that the photoconversion of 纬 -HCH in snow is faster than that in ice, and the response to the inhibition of Fe3 is more sensitive. (4) HA in ice phase accelerates the photoconversion of 纬 -HCH by producing monolinear oxygen (1O2), hydroxyl radical (OH) and triple excited state (HA*). (5) the light conversion rate of 纬 -HCH in ice samples was basically the same as that of 纬 -HCH under simulated light. However, the light conversion rate of 纬 -HCH in snow samples was lower than that in simulated illumination in laboratory. (6) in the presence of HA, the photoconversion products of 纬 -HCH were mainly pentachlorocyclohexene, o-dichlorobenzene and m-dichlorobenzene, and monochlorobenzene. 1O2 indirectly accelerated the photoconversion process of 纬 -HCH by consuming intermediate products.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：X131
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