大气气溶胶测量 atmospheric aerosol measurements

发布时间：2011-06-06 11:38:48 来源：文档文库

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A review of atmospheric aerosol measurements

Abstract

Recent developments in atmospheric aerosol measurements are reviewed. The topics included complement those covered in the recent review by Chow (JAWMA 45: 320}382, 1995) which focuses on regulatory compliance measurements and filter measurements of particulate composition. This review focuses on measurements of aerosol integral properties (total number concentration, CCN concentration, optical coefficients, etc.), aerosol physical chemical properties (density, refractive index, equilibrium water content, etc.), measurements of aerosol size distributions, and measurements of size-resolved aerosol composition. Such measurements play an essential role in studies of secondary aerosol formation by atmospheric chemical transformations and enable one to quantify the contributions of various species to effects including light scattering/absorption, health effects, dry deposition, etc. Aerosol measurement evolved from an art to a science in the 1970s following the development of instrumentation to generate monodisperse calibration aerosols of known size, composition, and concentration. While such calibration tools permit precise assessments of instrument responses to known laboratory-generated aerosols, unquantifiable uncertainties remain even when carefully calibrated instruments are used for atmospheric measurements. This is because instrument responses typically depend on aerosol properties including composition, shape, density, etc., which, for atmospheric aerosols, may vary from particle-to-particle and are often unknown. More effort needs to be made to quantify measurement accuracies that can be achieved for realistic atmospheric sampling scenarios. The measurement of organic species in atmospheric particles requires substantial development. Atmospheric aerosols typically include hundreds of organic compounds, and only a small fraction (&10%) of these can be identified by state-of-the-art analytical methodologies. Even the measurement of the total particulate organic carbon mass concentration is beset by difficulties including the unknown extent of evaporative losses during sampling, adsorption of gas-phase organic compounds onto sampling substrates, and the unknown relationship between carbon mass and mass of the particulate organics. The development of improved methodologies for such measurements should be a high priority for the future. Mass spectrometers that measure the composition of individual particles have recently been developed. It is not clear that these instruments will provide quantitative information on species mass concentrations, and more work is needed to routinely interpret the vast quantities of data generated during field sampling. Nevertheless, these instruments substantially expand the range of atmospheric aerosol issues that can be explored experimentally. These instruments represent the most significant advance in aerosol instrumentation in recent years. 2000 Elsevier Science Ltd., All rights reserved.

Keywords: Fine particles; Size distributions; Aerosol sampling; Particle properties

论大气气溶胶测量

摘要：本文对大气气溶胶测量的最新发展进行了评述。论述包括近来周所作评论的补充(JAWMA 45: 320}382, 1995)，这些补充评论聚焦在微粒成分的合规测量和过滤器测量上。本评论集中在气溶胶整体性能测量（总浓度、CCN浓度、光系数等），气溶胶物理化学性质（密度、折射率、平衡水分率等），气溶胶大小分布测量和由大小决定的气溶胶组成测量。这种测量对研究因大气化学反应引起的二次气溶胶形成发挥着重要作用，并使人们可以量化各物种对其效果贡献，包括光的散射或吸收、健康效应、干沉积等。气溶胶测量在20世纪70年代从一门艺术发展为科学，在生产具有已知大小、组成和浓度的单分散校准气溶胶技术发展之后。虽然这种校正工具使仪器可以对已知的实验室生成气溶胶进行精确评估，并使用精密校正仪器进行气溶胶测量，但无法量化的不确定因素仍然存在。这是因为仪器反应典型地取决于气溶胶的性质，包括构成、形状、密度等，而这些性质，对于大气气溶胶来说，各个粒子都可能会有所不同并通常是未知的。我们需要作出更多努力来量化测量准确性，以达到实际大气采样情况。大气粒子中有机类的测量需要实质的发展。大气气溶胶通常包括数百个有机化合物，只有一小部分（＆10％，）可以用最先进的分析方法鉴定出。即便测量微粒有机碳总量的质量浓度，也被各种困难所困扰，包括未知的采样过程中蒸发的损失程度、取样基层中气相有机化合物的吸附量以及碳和微粒的质量间的未知关系。未来对这一测量方法的改进发展应是优先考虑的。测量粒子个体组成的质谱仪近来已经有所发展。目前尚不清楚这些仪器是否将提供关于物质质量浓度的数量信息，而通常还有大量现场取样时所得的数据需要更多的解析。然而，这些仪器本质上扩大了可被实验地探索的大气气溶胶问题的范围。这些仪器代表了近年气溶胶器械方面最为重大的进展。2000年Elsevier科学有限公司，版权所有。