【作者】 李伟；

【导师】 黄山；

【作者基本信息】 暨南大学 ， 环境工程（专业学位）， 2022， 硕士

【摘要】 有机硝酸酯是当前大气化学机理研究中的热点和难点物质,其大气行为可连接挥发性有机物VOCs、氮氧化物NO_x、二次有机气溶胶（SOA）、臭氧及氧化性自由基（如OH和NO₃自由基）等。颗粒态有机硝酸酯可能是研究大气PM_2.5和臭氧协同控制的关键切入点之一。本研究在广州城区开展外场观测,利用高分辨率飞行时间质谱仪（HR-To F-AMS）对有机硝酸酯进行量化,使用两种估算方法进行比较确定准确浓度,得到的浓度数据与部分外部数据结合分析,对大气有机硝酸酯的主要来源、大气转化过程和影响因素进行初步探索。由于比值定量的方法依赖经验参数,具有不确定性并且只能估算有机硝酸酯浓度的上下限;以及与外部FIGAERO-HR-To F-CIMS测量得到的分子水平的有机硝酸酯进行相关性分析,其中AMS-PMF方法与CIMS方法估算的有机硝酸酯出来的相关性（R=0.79）高于比值法（R=0.44）,依据以上的原因最终使用AMS-PMF方法估算出珠三角城市地区有机硝酸酯的浓度范围在0.08-5.37μg/m³,平均浓度为1.53μg/m³。有机硝酸酯中二次生成比一次排放多,分别占总有机硝酸酯87.88%和12.12%,其中二次生成过程包括最为老化的氧化性因子MOOA（该来源占据总有机硝酸酯44.80%）、生物质燃烧的老化源a BBOA（25.13%）及OH和NO₃自由基对VOCs氧化本地生成的源LOOA（16.02%）。在污染时段和清洁时段,二次生成的有机硝酸酯浓度皆高于一次排放,清洁时段MOOA贡献的二次有机硝酸酯更多,表明清洁时段颗粒态有机硝酸酯受远距离传输影响较大;在高NO_x浓度的环境下,有机硝酸酯总浓度明显高于低NO_x条件。在日间,有机硝酸酯平均浓度低于夜间,可能因为夜间更低的边界层不利于扩散,导致浓度更高,并且有机硝酸酯白天和夜间生成机制不同。基于观测得到的大气挥发性有机物（VOCs）浓度及相关参数,本研究估算了不同VOCs通过OH自由基（日间）和NO₃自由基（夜间）氧化生成有机硝酸酯的生成潜势,据此识别了广州城区有机硝酸酯的主要VOC前体物:日间主要由OH自由基氧化形成,单萜烯和正戊烷等VOCs生成有机硝酸酯的能力最大,夜间大部分为NO₃自由基氧化单萜烯反应形成。高浓度NO_x、温度为22℃-28℃以及RH为60%-80%的条件下有机硝酸酯的浓度更高,有机硝酸酯与O_x的相关性说明上午的形成主要受到大气氧化性控制。更多还原

【Abstract】 Particulate organonitrates are the key component in the current atmospheric chemical mechanism research,and its atmospheric behavior can connect to organic compounds（VOCs）,nitrogen oxides（NO_x）,secondary organic aerosols（SOA）,ozone and oxidizing radicals（such as OH radicals and NO₃ radicals）.Particulate organonitrates may be one of the key entry points for studying the coordinated control of atmospheric PM_2.5 and ozone.In this study,field observations were carried out in the urban area of Guangzhou,and high-resolution time-of-flight mass spectrometry（HR-To F-AMS）was used to quantify organic nitrates,and two estimation methods were used to compare and determine the exact concentration.The obtained concentration data combined with some external data for analysis,the main sources,atmospheric transformation processes and influencing factors of atmospheric organic nitrates were initially explored.Since the method of ratio quantification relies on empirical parameters,it has uncertainties and can only estimate the upper and lower limits of the organic nitrates concentration;and the correlation analysis with the molecular level organic nitrates measured by external FIGAERO-HR-To F-CIMS,where the correlation（R=0.79）of the organic nitrates estimated by the AMS-PMF method and the CIMS method is higher than that of the ratio method（R=0.44）.Based on the above reasons,the AMS-PMF method was finally used to estimate the organic nitrates in the urban area of the Pearl River Delta.The concentration range of 0.08-5.37μg/m³,with an average concentration of 1.53μg/m³.The secondary generation of organic nitrates is more than the primary discharge,accounting for 87.88%and 12.12%of the total organic nitrates,respectively.The secondary generation process includes the most aging oxidative factor MOOA（this source accounts for 44.80%of the total organic nitrates）.a BBOA（25.13%）,the aging source of material combustion,and LOOA（16.02%）,a local source of oxidation of VOCs by OH and NO₃ radicals.During the pollution period and cleaning period,the concentration of secondary organic nitrates was higher than that of primary discharge,and MOOA contributed more secondary organic nitrates during the cleaning period,indicating that the particulate organic nitrates were greatly affected by long-distance transmission during the cleaning period;Under the high NO_x concentration environment,the total concentration of organic nitrates was significantly higher than that under the low NO_x condition.During the day,the average concentration of organic nitrates was lower than that at night,possibly because the lower boundary layer at night was not conducive to diffusion,resulting in higher concentrations,and the generation mechanism of organic nitrates was different during the day and night.Based on the observed concentrations of atmospheric volatile organic compounds（VOCs）and related parameters,this study estimated the generation potential of different VOCs to form organic nitrates through the oxidation of OH radicals（daytime）and NO₃ radicals（nighttime）.The main VOC precursors of organic nitrates in Guangzhou urban area are:mainly formed by the oxidation of OH radicals during the day,VOCs such as monoterpenes and n-pentane have the greatest ability to generate organic nitrates,and most of the NO₃ radicals oxidize monoterpenes at night.reaction is formed.The concentration of organic nitrates was higher under the conditions of high concentration of NO_x,temperature of 22℃-28℃,and RH of 60%-80%.The correlation between organic nitrates and O_x indicated that the formation of morning was mainly controlled by atmospheric oxidation.更多还原