RCEES OpenIR  > 环境化学与生态毒理学国家重点实验室
冰冻水体中卤素转化 及溶解性有机质卤化研究
郝智能
Subtype博士后
Thesis Advisor江桂斌 ; 刘景富
2019-05
Degree Grantor中国科学院生态环境研究中心
Place of Conferral北京
Degree Name理学
Degree Discipline环境科学
Keyword溶解性有机质,冰冻氧化,冰冻还原,活性卤物质,有机卤化物 Dissolved Organic Matter, Freeze Oxidation, Freeze Reduction, Reactive Halogen Species, organoHalogen Compounds
Abstract

         溶解性有机质(DOM)广泛存在于环境水体中,其与环境中的活性卤物质(RHS)发生反应生成的卤代有机物(OHCs)被认为是环境中OHCs重要而广泛的来源。冰冻过程具有浓缩等效应,能加速已知化学反应或者导致未知化学反应的发生。其中冰冻过程加速卤素的转化生成RHS的反应寒冷环境或者极地地区中重要的反应,进而导致的DOM卤化可能是寒冷环境或者极地地区中OHCs重要的天然来源,对卤素的全球地球化学循环具有重要的影响。为此,为科学评估寒冷环境或者极地地区中OHCs的来源和环境效应,迫切需要研究卤素的转化和DOM卤化的产物及其转化机制。

      溴酸盐是饮用水或者游泳池水消毒过程中生成的消毒副产物,因其具有潜在致癌性和化学稳定性,其在环境中的去除引起了广泛关注,不仅如此,溴酸盐也可在自然环境过程生成。碘离子广泛存在于自然水体中,由于其具有较低的氧化还原电位,易被氧化生成活性碘物质(RIS)进而导致有机碘化物(OICs)的生成。尽管溴酸盐在水体环境中稳定性好,碘离子在水环境中氧化速率很慢,但有文献报道,冰冻过程能加速溴酸盐的还原和碘离子的氧化,DOM的存在即可与该过程生成的RHS发生反应生成OHCs。因此,该过程可能是寒冷环境或者极地地区中OHCs重要的来源。基于此,本文开展了DOM冰冻还原溴酸盐及其溴化,以及碘离子的冰冻氧化及DOM的碘化工作。论文主要包括以下内容:

      第一部分,首先介绍了环境中DOM的来源、分离富集及其光谱和结构表征。随后重点介绍了DOM在环境中的非生物卤化过程和机理,论述了环境中OHCs的分析进展。最后介绍了冰冻过程加速化学反应和导致新化学发生的机制,以及卤素在冰冻环境中的转化。

      第二部分,冰冻水体因具有浓缩效应,能显著促进DOM还原溴酸盐(BrO3–),同时该过程也会生成活性溴物质(RBrS),进而与DOM反应生成有机溴化物(OBCs)。研究表明,与常温液态水和不含DOM的对照实验相比,冰冻过程能显著促进DOM还原BrO3–。冰冻48 h后,在pH 3和pH 4以及不同DOM和BrO3–初始浓度条件下,有78.1%–100%的BrO3–被还原。Br–是主要还原产物之一,其占BrO3–初始含量的30.9%–47.8%。其余的转化产物主要是RBrS和DOM反应生成的OBCs,以OBCs的总有机溴(TOBr)含量/BrO3–初始浓度比值计算BrO3–经DOM冰冻还原生成OBCs的转化率,该值在28.2%到52.5%之间,并取决于BrO3–/DOM含量的比值。FT-ICR MS共检测到110–603种目标化合物,其中大部分是由亲电取代或加成反应生成的高度不饱和酚类化合物。通过对除生成OBCs前体物外只含C、H和O氧原子的物质分析发现,冰冻体系中还原BrO3–的主要组分为具有低碳氧化态的物质。


      第三部分,冰冻水体因具有浓缩效应,能显著促进O2氧化I–的反应,进而生成大量活性碘物质(RIS)以及有机碘化物(OICs)。为此,以3,5-二甲基吡唑作为RIS的探针分子,探究了I–的冰冻氧化及环境条件对该过程的影响。结果表明,I–可在液态水体中发生氧化,生成的RIS约为0.03–0.42 μmol L–1,冰冻反应能显著加速I–的氧化反应,尤其是在偏酸性条件下,反应72 h后在pH 7至pH 3条件下生成的RIS量分别为0.16、0.18、0.25、4.71和31.6 μmol L–1。除pH外,I–的浓度、溶液含氧量以及冻融循环次数也可影响I–的冰冻氧化。上述环境因素对偏酸性环境下I–冰冻氧化的影响更为显著。在此基础上,基于HPLC和ICPMS分析了DOM碘化生成的OICs的总有机碘含量(TOI),在液态水体中检测出0.32–0.39 μmol L–1的TOI,冰冻后TOI含量都有相应提升,在pH 3和pH 4检出的TOI达到了1.20和2.83 μmol L–1。受限于DOM的浓度,检出的TOI浓度远低于对应的RIS生成总量。同样,环境条件对OICs的生成具有显著影响。最后利用FT-ICR MS对OICs进行了分析表征,在液态水体中检测出94–129种OICs,冰冻水体中检出183–1197种OICs,这些OICs主要属于木质素和单宁类物质。

Other Abstract

      Dissolved organic matter (DOM) widely exists in environmental water, it can react fastly with active halogen substances (RHS) in the environment to generate organohalogen compounds (OHCs), which is considered as an important and widespread source of OHCs in the environment. Due to the effects such as concentration, freezing process can accelerate known chemical reactions or lead to the happen of unknown chemical reactions, consequently, the reaction is very important in the cold environment. Therefore, DOM halogenation in cold areas may represent an important natural source of OHCs, which has an important impact on the global geochemical cycle of halogen. Thus, in order to scientifically evaluate the sources and environmental effects of OHCs in polar regions or cold environments, it is urgent to study the production of RHS and DOM halogenated products in frozen water and their transformation mechanisms.
      Bromate is a disinfection by-product generated in the disinfection process of drinking water or swimming pool water. Because of its potential carcinogenicity and chemical stability, the removal of bromate in the environment has attracted widespread attention. At the same time, bromate can also be generated in the natural environment process. Iodide is widely present in natural water bodies. Due to its low redox potential, it can be easily oxidized to active iodine substances (RIS), which in turn lead to the generation of organoiodine compounds (OICs). Although bromate has good stability in water environment and iodide oxidation rate is slow in water environment, freezing process have been reported to be able to accelerate bromate reduction and iodide oxidation, and then DOM can react with RHS generated in this process to produce OHCs. Therefore, this process may be an important source of OHCs in cold environments and plolar regions. Based on this, freeze-induced bromate reduction and DOM bromination, as well as iodide oxidantino and DOM iodization were carried out in this paper. The thesis mainly includes the following contents:
      In the first part, the sources, separation and enrichment techniques of DOM as well as its spectral and structural characterization were summarized. Subsequently, the processes and mechanisms of DOM abiotic halogenation in the environment were introduced emphatically, and the analysis progress of OHCs in the environment was discussed. Finally, the mechanism of accelerating chemical reaction and causing new chemistry in freezing process and halogen transformation in freezing environment were introduced.
       In the second part, because of the concentration effect, freezing can significantly enhanced the DOM-induced bromate reduction. At the same time, this process also accompanies with the reactive bromine species (RBrS), which would react with DOM to generate organobromine compounds (OBCs). This research found that compared with the normal liquid water and DOM-free control experiments, the freezing process can significantly promote BrO3– reduction by DOM.After 48 h of freezing, 78.1%–100% of BrO3– was removed at pH 3 and pH 4, and under different initial concentrations of DOM and BrO3–. Br– was one of the main reduction products, which accounted for 30.9%-47.8% of the total bromine. The rest of the conversion products are mainly OBCs, which were generated through the reaction of RBrS and DOM. The conversion rate of OBCs generated by DOM-induced freeze reduction was calculated according to the ratio of total organic bromine (TOBr) content to the initial concentration of BrO3–, which ranged between 28.2% and 52.5% and depended on the ratio of BrO3–/DOM content. FT-ICR MS detected 110–603 OBCs, most of which are highly unsaturated phenolic compounds formed by electrophilic substitution or addition reaction. Through the analysis of substances containing only C, H and O oxygen atoms except for those precursor compounds, it was found that the main components responsible for BrO3– reduction in freezing system is substances with low carbon oxidation state.
       In the third part, frozen water can significantly promote I– oxidation by O2 due to the concentration effect, which would generate a large amount of RIS and OICs. Therefore, 3,5-dimethylpyrazole was used as the probe molecule for RIS determination, and the freezing-induced I– oxidation and the impacts of environmental conditions on this process were investigated. The results showed that I– can be oxidized in liquid water, and the generated RIS was about 0.03–0.42 μmol L–1. Freezing reaction can significantly accelerate I– oxidation reaction especially under acidic conditions, the amount of RIS generated at pH 7 to pH 3 after 72 h was 0.16, 0.18, 0.25, 4.71 and 31.6 μmol L–1, respectively. In addition to pH, I– concentration, solution oxygen content and freeze-thaw cycles can also affect I– freeze oxidation. These environmental factors have greater influence on I– freeze oxidation in acidic environment. Based on this, the total organic iodine (TOI) content of OICs generated in the presence of DOM was analyzed based on HPLC and ICP-MS. The TOI was 0.32–0.39 μmol L–1 in normal liquid water. After freezing, the TOI content increased correspondingly. The TOI detected at pH 3 and pH 4 reached 1.20 and 2.83 μmol L–1. Due to the low concentration of DOM compared to the total RIS, the detected TOI concentration was far lower than the corresponding RIS generation amount. The environmental factors also impacted on on OICs generation. Finally, OICs were analyzed by FT-ICR MS, and 94–129 OICs were detected in normal solutions and 183-1197 OICs were detected in frozen water, these OICs mainly belonged to lignin and tannins.

Pages78
Language中文
Document Type学位论文
Identifierhttp://ir.rcees.ac.cn/handle/311016/42206
Collection环境化学与生态毒理学国家重点实验室
Recommended Citation
GB/T 7714
郝智能. 冰冻水体中卤素转化 及溶解性有机质卤化研究[D]. 北京. 中国科学院生态环境研究中心,2019.
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