Infrared Interrogation of Atmospheric Aerosols

在地球大气层中发现了9303058种大小、形状和成分各异的尤因气溶胶。有些很容易被观测到为云、霾、烟雾或烟雾，它们会影响天气、气候学和辐射能量平衡。有些是成核点或云的形成。其他的则是丰富的化学和光化学的来源。由于气溶胶的重要性显而易见，许多技术都被用于气溶胶的研究。这项研究提出的观点是，通过探索重要大气气溶胶表面的物理和化学性质，将加强对它们的了解。这种勘探的一种通用分析技术是红外光谱分析。虽然许多类型的气溶胶可以进行红外光谱询问，但盐粒子被选为分析技术的例子。这些粒子特别相关。在海洋上产生的海盐气溶胶，即使不是全球大气中最丰富的颗粒负荷，也是其中之一。它们的组成被一种复杂的化学物质所改变。我们将研究在温控室中生产悬浮盐粒的两种方法。由于光程将超过100米，红外灵敏度允许询问气溶胶及其表面附着的分子的大小、形状和组成。对于固体盐气溶胶，将探索在表面和水覆盖层中加入OH-和其他离子。还将监测NO2在表面的反应。水、OH-、NO2和其他氧化物一直是实验室研究盐的目标，因为类似的表面化学很可能在大气中发生。还将进行探索负载盐颗粒性质的实验，并探索询问表面缺陷浓度的方法。这表明大气化学是在这些表面缺陷处启动的。对于冰粒，光谱询问很可能能够表征它们的内部结构(如无定形、冰I或微孔)以及它们的表面特性。是表面性质决定了气溶胶中发生的非均相化学的类型，无论是在实验室还是在大气中。首席调查员的实验室已经成功地进行了悬浮和支撑气雾剂的初步实验。这些成功表明了实验的实用性。对这些实验室生产的气溶胶的红外光谱询问将揭示未来在大气中进行气溶胶实验的可行性。

9303058 Ewing Aerosols in a variety of sizes, shapes and compositions are found throughout the earth's atmosphere. Some are easily observed as clouds, haze, smog or smoke and they affect weather, climatology and the radiation energy balance. Some are nucleation sites or cloud formation. Others are sources of rich chemistry and photochemistry. With the obvious importance of aerosols, many techniques have been directed toward their study. This research advances the view that an understanding of important atmospheric aerosols will be enhanced by exploring the physical and chemical properties of their surfaces. A versatile analytical technique for this exploration is infrared spectroscopy. While many types of aerosols are amenable to infrared spectroscopic interrogation, salt particles are chosen as examples of the analytical techniques. These particles are of particular relevance. Sea salt aerosols generated over the oceans contribute one of the, if not the, most abundant particulate loads on the global atmosphere. Their composition is transformed by an intricate chemistry. Two methods for producing suspended salt particles in a temperature controlled chamber will be investigated. Since the optical path will be in excess of 100 m, infrared sensitivity allows interrogation of the size, shape and composition of the aerosols as well as molecules stuck to their surfaces. For solid salt aerosols the incorporation of OH- and other ions at the surface as well as water overlayers will be explored. Reactions of NO2 at the surface will also be monitored. Water, OH-, NO2 and other oxides have been targeted for laboratory studies of salt because similar surface chemistry is likely to occur in the atmosphere. Experiments to explore the properties of supported salt particles will also be performed and methods for interrogating surface defect concentrations will be explored. It is suggested that atmospheric chemistry is initiated at these surface defects . For ice particles spectroscopic interrogation will likely be able to characterize their interior structure (e.g. amorphous, ice I, or microporous) as well as their surface properties. It is the surface properties that dictate the type of heterogeneous chemistry that occurs in aerosols, whether in the laboratory or in the atmosphere. Preliminary experiments with both suspended and supported aerosols have already been successful in the laboratory of the Principal Investigator. These successes suggest the practically of the experiments. The infrared spectroscopic interrogation of these laboratory produced aerosols will reveal the feasibility for future experiments on aerosols in the atmosphere.