Infrared Interrogation of Atmospheric Aerosols

[9303058]地球大气中存在着各种大小、形状和成分的气溶胶。有些很容易观察到，如云、雾霾、烟雾或烟雾，它们影响天气、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，许多技术都被用于研究它们。这项研究提出了一种观点，即通过探索重要的大气气溶胶表面的物理和化学性质，将加强对它们的理解。红外光谱是一种通用的分析技术。虽然许多类型的气溶胶都适合红外光谱分析，但盐颗粒被选为分析技术的例子。这些粒子是特别相关的。在海洋上空产生的海盐气溶胶，即使不是全球大气中最丰富的微粒负荷，也是其中之一。它们的组成经过复杂的化学反应而发生变化。将研究在温度控制室中产生悬浮盐颗粒的两种方法。由于光程将超过100米，红外灵敏度允许对气溶胶的大小，形状和组成以及粘附在其表面的分子进行调查。对于固体盐气溶胶，OH-和其他离子在表面以及水覆盖层的掺入将被探索。二氧化氮在表面的反应也将被监测。水、OH-、NO2和其他氧化物已成为实验室研究盐的目标，因为类似的表面化学反应可能发生在大气中。我们还将进行实验来探索负载盐颗粒的性质，并探索询问表面缺陷浓度的方法。认为大气化学是由这些表面缺陷引起的。对于冰粒子，光谱分析很可能能够表征它们的内部结构（如无定形、冰I或微孔）以及它们的表面性质。无论是在实验室还是在大气中，都是表面性质决定了气溶胶中发生的非均相化学类型。在首席研究员的实验室里，悬浮和支撑气溶胶的初步实验已经取得成功。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进行红外光谱分析，将为未来大气中气溶胶的实验提供可行性。

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.