ICARUS Chamber Experiment: Ziemann_20190320_Methyl nitrite/Nitric oxide/2-Decyl nitrate_Hydroxyl radical_DOS

Goals: Determine SOA yield of OH radical oxidation of the VOCSummary: Experiments were performed at ambient temperature (25 C) and pressure (84 kPa) in an 8 m^3 FEP Teflon environmental chamber. Purified air was supplied by AADCO clean air generators (less than 5 ppb hydrocarbons, and less than 1% RH). The chamber was first seeded with 200 ug/m^3 of either dioctyl sebacate (DOS) or dioctyl phthalate (DOP) polydisperse aerosol with peak particle diameter of 200 nm, which was added from an evaporation-condensation source. A measured mass of an alkyl nitrate was then added from a heated glass bulb using ultra-high purity (UHP) N2. Thermal decomposition was avoided by heating the bulb to only 65 C, well below the temperatures alkyl nitrates encounter during gas chromatographic analysis, and limiting the residence time in the gas phase to 1 s^-1 by flushing with 15 L/min of UHP N2. Glass bulbs containing a measured pressure of methyl nitrite or NO were prepared on a vacuum manifold and added to the chamber with UHP N2 in amounts sufficient to achieve concentrations of 5 ppm of each in the chamber. Reactions were initiated by turning on blacklights that are located on two sides of the chamber for 60 minutes at a light intensity corresponding to an NO2 photolysis rate constant of 0.37 min^-1. Under these conditions OH radicals were generated from the photolysis of methyl nitrite (Atkinson et al. 1981) with average concentrations of 3 x 107 molecules/cm^3, based on the amount of alkyl nitrate that reacted and an estimated rate constant for its reaction with OH radicals (Ziemann and Atkinson 2012).Organization: Ziemann Lab Affiliation: University of Colorado, Boulder, Boulder, CO, USA Chamber: Janet (Chamber 1)Experiment Category: Gas phase chemical reaction, Photolysis, any phase, Aerosol formation Oxidant: Hydroxyl radical Reactants: Methyl nitrite, Nitric oxide, 2-Decyl nitrate Reaction Type: Photooxidation Relative Humidity: 1 Temperature: 25 Seed Name: DOS Pressure: 630

研究目标：确定挥发性有机化合物（VOC，Volatile Organic Compound）经羟基自由基氧化后的二次有机气溶胶（SOA，Secondary Organic Aerosol）产率。
实验概况：实验于环境温度（25℃）、压力（84 kPa）下，在容积为8 m³的FEP聚四氟乙烯（FEP Teflon）环境烟雾箱中开展。实验所用净化空气由AADCO洁净空气发生器提供，其烃类含量低于5 ppb，相对湿度（RH，Relative Humidity）低于1%。首先向烟雾箱中注入200 μg/m³的多分散气溶胶种子，该种子为癸二酸二辛酯（DOS，Dioctyl Sebacate）或邻苯二甲酸二辛酯（DOP，Dioctyl Phthalate），其峰值粒径为200 nm，通过蒸发-冷凝源添加。随后，采用超高纯（UHP，Ultra High Purity）氮气作为载气，通过加热玻璃储样瓶将定量的硝酸烷基酯引入箱内；为避免热分解，将储样瓶加热温度控制在65℃以下，远低于气相色谱分析时硝酸烷基酯所处的温度，并以15 L/min的流速通入超高纯氮气，将其在气相中的停留时间限制为1 s⁻¹。通过真空歧管制备充有定量亚硝酸甲酯或一氧化氮（NO，Nitric Oxide）的玻璃储样瓶，随后以超高纯氮气将其注入烟雾箱，使箱内两种物质的浓度均达到5 ppm。通过开启烟雾箱两侧的黑光灯启动反应，光照时长为60分钟，光照强度对应的二氧化氮（NO₂）光解速率常数为0.37 min⁻¹。在此条件下，羟基自由基由亚硝酸甲酯光解产生（Atkinson等，1981），其平均浓度为3×10⁷ 分子/cm³，该浓度基于已反应的硝酸烷基酯的量及其与羟基自由基反应的估算速率常数（Ziemann与Atkinson，2012）计算得到。
研究机构：齐默曼实验室（Ziemann Lab）
隶属单位：美国科罗拉多大学博尔德分校（University of Colorado, Boulder, Boulder, CO, USA）
烟雾箱编号：Janet（1号箱）
实验类别：气相化学反应、光解反应、多相反应、气溶胶生成
氧化剂：羟基自由基
反应物：亚硝酸甲酯、一氧化氮、2-癸基硝酸酯
反应类型：光氧化反应
相对湿度：1%
温度：25℃
气溶胶种子名称：DOS
压力：630