摘要/Abstract

使用离子色谱分析了常温、常压、湿润和氧气存在条件下，NH₃和Cl₂在γ-Al₂O₃颗粒物表面非均相反应的产物及其受NH₃浓度、反应时间等的影响；并定量分析了NH₃、Cl₂、SO₂和NO₂单独及共存条件下，γ-Al₂O₃表面Cl^-、NO₃^-和SO₄^2-等二次无机颗粒物的生成总量.结果表明：NH₃和Cl₂在γ-Al₂O₃表面具有协同作用，2 h后Cl^-的生成总量可达589.65 μg，其生成量随时间延长而不断增加.表面氯化物的生成量在NH₃浓度为400 ppm时达到峰值，且随NH₃浓度的增加呈先增加而后减少的趋势.活性氯存在下，NH₃对颗粒物表面Cl^-、NO₃^-和SO₄^2-的生成有促进作用，且四种气体共存时复合正反馈效应最明显.同时，本研究对NH₃和Cl₂在颗粒物表面的非均相反应机理及活性氯和氨的排放对大气中二次无机颗粒物的贡献进行了探讨.
关键词: 非均相反应, 二次无机颗粒物, NH₃, Cl₂
The effect of NH₃ concentration, reaction time and other conditions on the heterogeneous reaction of NH₃ and Cl₂ on the surface of γ-Al₂O₃ particles was investigated at the room temperature, pressure and in the presence of oxygen by ion chromatography (IC). The formation of the surface species (Cl^-, NO₃^-, and SO₄^2-) via both individual reaction and co-existing reaction of NH₃, Cl₂, SO₂ and NO₂ on the surface of γ-Al₂O₃ was investigated as well. The results revealed that NH₃ (400 ppm) and Cl₂ (400 ppm) had synergistic effect on the surface γ-Al₂O₃, and the total yield of Cl^- was 589.65 μg after reaction of 2 h. The formation of the surface chlorides increased firstly and then decreased with the increase of ammonia concentration, and the maximum yield of Cl^- was reached at 400 ppm of NH₃. In the presence of active chlorine, NH₃ significantly promoted the generation of the adsorptive species on the surface, such as Cl^-, NO₃^- and SO₄^2-, and the most obvious synergistic effect was induced to form on the conditions of four gases co-existence. The heterogeneous reaction mechanism of NH₃ with Cl₂ and the influence on the atmospheric environment were also discussed as well. Additionally, the mixing ratios used in the study are extremely high compared with ambient levels, which could be as a simulation to explore whether the synergistic effect obtained in this paper are also present in the real ambient conditions. We have studied a relatively low mixing ratios for heterogeneous reaction experiments, but the content of nitrate and chloride on the surface of γ-Al₂O₃ were lower than the limit of detection of ion chromatography. Therefore, other researches such as Knudsen cell and smog chamber study, field monitoring, and mode study are also worth for exploring in future study. The results of this study could provide reference data for the study of the contribution of active chlorine and ammonia to the formation of secondary inorganic particles.
Key words: heterogeneous reaction, secondary inorganic particles, NH₃, Cl₂


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