ICARUS Chamber Experiment: Ziemann_20180211_Methyl nitrite/Nitric oxide/3-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, 3-Decyl nitrate Reaction Type: Photooxidation Relative Humidity: 1 Temperature: 25 Seed Name: DOS Pressure: 630

研究目标：明确挥发性有机化合物（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。
实验概述：实验于环境温度（25℃）与压力（84 kPa）下，在容积为8 m³的FEP聚四氟乙烯环境舱中开展。实验所用净化空气由AADCO型洁净空气发生器提供，其产出空气中烃类物质浓度低于5 ppb，相对湿度（RH，Relative Humidity）低于1%。实验舱首先以200 μg/m³的癸二酸二辛酯（DOS，Dioctyl Sebacate）或邻苯二甲酸二辛酯（DOP，Dioctyl Phthalate）多分散气溶胶进行种子气溶胶接种，该气溶胶的粒径峰值为200 nm，通过蒸发-冷凝源进样。随后通过加热玻璃容器，以超高纯（UHP，Ultra-High Purity）氮气吹扫，将定量质量的硝酸烷基酯注入舱内。为避免热分解，将玻璃容器加热温度仅设为65℃，该温度远低于硝酸烷基酯在气相色谱分析中所经历的温度；同时以15 L/min的超高纯氮气吹扫，将其在气相中的停留时间控制为1 s⁻¹。在真空歧管上制备装有定量压力的亚硝酸甲酯或一氧化氮（NO）的玻璃容器，随后以超高纯氮气将其注入实验舱，调整注入量使得舱内两者浓度均达到5 ppm。通过开启位于实验舱两侧的黑光灯，以对应二氧化氮（NO₂）光解速率常数为0.37 min⁻¹的光强条件下照射60分钟，以此引发反应。在此条件下，羟基自由基由亚硝酸甲酯光解产生（Atkinson等，1981），根据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和Atkinson，2012），可计算得其平均浓度为3×10⁷ 个分子/立方厘米。
研究机构：齐曼实验室（Ziemann Lab）
所属单位：美国科罗拉多大学博尔德分校（University of Colorado, Boulder），地址为科罗拉多州博尔德市
实验舱：珍妮特（1号舱）
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、硝酸3-癸酯
反应类型：光氧化反应
相对湿度：1%
温度：25℃
种子气溶胶名称：癸二酸二辛酯（DOS）
压力：630