Gibson Elizabeth R, Hudson Paula K, Grassian Vicki H
Department of Chemistry and the Center for Global and Environmental Research, The University of Iowa, Iowa City, Iowa 52242, USA.
J Phys Chem A. 2006 Oct 26;110(42):11785-99. doi: 10.1021/jp063821k.
As aerosols, such as sea salt and mineral dust, are transported through the atmosphere they undergo heterogeneous reactions with nitrogen oxides to form nitrate salts. The nitrate salt can have quite different physicochemical properties than the original aerosol, resulting in an aerosol that will markedly differ in its climate impact, heterogeneous chemistry, and photoactivity. In this Feature Article, we will review some aspects of the importance of aqueous nitrate aerosols as well as describe a new multi-analysis aerosol reactor system (MAARS) that is used to measure the physicochemical properties of these atmospherically relevant aerosols. Here we show measurements of the hygroscopic properties, cloud condensation nuclei activity, and FTIR extinction of nitrate salt aerosol. In particular, we have measured the hygroscopic growth of 100 nm size-selected nitrate particles including NaNO3, Ca(NO3)2, Mg(NO3)2, and a 1:1 mixture of Ca(NO3)2 and Mg(NO3)2 as a function of relative humidity (RH) at 298 K. Using Köhler theory, we have quantified the water content of these particles with increasing RH. FTIR extinction measurements of the full size distribution of each of the nitrate aerosols are analyzed to yield information about the local solvation environment of the nitrate ions and the long-wavelength light scattering of the particles at different RH. Furthermore, we have measured and compared the cloud condensation nuclei (CCN) activity of CaCO3, a large component of mineral dust aerosol, and Ca(NO3)2, a product of atmospherically aged CaCO3 through reaction with nitrogen oxides, at supersaturations from 0.1% to 0.9%. These quantitative physicochemical data are needed if we are to better understand the chemistry as well as the climate effects of atmospheric aerosols as they are entrained, transported, reacted, and aged in the atmosphere. Our studies here focus on aqueous nitrate salts, the products of the reaction of nitrogen oxides with sea salt and mineral dust aerosol.
诸如海盐和矿物粉尘等气溶胶在大气中传输时，会与氮氧化物发生非均相反应形成硝酸盐。硝酸盐的物理化学性质可能与原始气溶胶有很大不同，从而产生一种在气候影响、非均相化学和光活性方面有显著差异的气溶胶。在这篇专题文章中，我们将回顾水性硝酸盐气溶胶重要性的一些方面，并描述一种用于测量这些与大气相关的气溶胶物理化学性质的新型多分析气溶胶反应器系统（MAARS）。在此，我们展示了硝酸盐气溶胶的吸湿特性、云凝结核活性和傅里叶变换红外光谱消光的测量结果。特别是，我们测量了在298K下，包括硝酸钠、硝酸钙、硝酸镁以及硝酸钙和硝酸镁1:1混合物的100nm粒径选择硝酸盐颗粒的吸湿增长情况，作为相对湿度（RH）的函数。利用科勒理论，我们量化了这些颗粒随相对湿度增加的含水量。对每种硝酸盐气溶胶全尺寸分布的傅里叶变换红外光谱消光测量进行分析，以获取有关硝酸根离子局部溶剂化环境以及颗粒在不同相对湿度下长波长光散射的信息。此外，我们测量并比较了矿物粉尘气溶胶的主要成分碳酸钙以及通过与氮氧化物反应大气老化的碳酸钙产物硝酸钙在0.1%至0.9%过饱和度下的云凝结核（CCN）活性。如果我们要更好地理解大气气溶胶在被夹带、传输、反应和老化过程中的化学性质以及气候效应，就需要这些定量的物理化学数据。我们这里的研究重点是水性硝酸盐，即氮氧化物与海盐和矿物粉尘气溶胶反应的产物。
