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Knowledge of aerosol physical, chemical, optical properties is essential for judging the effect that particulates have on human health, climate and visibility. The aerosol time-of-flight mass spectrometer (ATOFMS) is capable of measuring, in real-time, the size and chemical composition of atmospheric aerosols. This was exemplified by the recent deployments of the ATOFMS to Mexico City and Riverside. The ATOFMS provided rapid information about the major particle types present in the atmosphere. Industrial sources of particles, such as fine mode particles containing lead, zinc and chloride were detected in Mexico City. The rapid time response of the ATOFMS was also exploited to characterize a coarse particle concentrator used in human health effects studies. The ATOFMS showed the ability to detect changes in particle composition with a time resolution of 15 min during short 2 hour human exposure studies.
An aerosol is a suspension of fine particles in a gas, usually air, and is generally taken to include both solid and liquid particles with dimensions ranging from a few nanometres up to around 100 micrometres in diameter. Aerosol sicence is the study of the physics and chemistry of aerosol behaviour and this includes techniques of generating particles of nanometre and micrometre dimensions: size classification and measurement, transport and deposition properties: chemical properties of aerosols in the atmosphere and in industry, as well as health effects from inhalation and industrial gas cleaning technology. Aerosols have important commercial implications, e.g. pressure-packaged `aerosol' products, agricultural sprays, atmospheric visibility and high technology materials and knowledge of aerosol properties is important in a wide range of disciplines, including industrial hygiene, air pollution, medicine, agriculture, meteorology and geochemistry. Written by an international team of contributors, this book forms a timely, concise and accessible overview of aerosol science and technology. Chemists, technologists and engineers new to aerosol science will find this book an essential companion in their studies of the subject. Those more familiar with aerosols will use it as an essential source of reference.
This new text offers experienced students a comprehensive review of available techniques for the remote sensing of aerosols. These small particles influence both atmospheric visibility and the thermodynamics of the atmosphere. They are also of great importance in any consideration of climate change problems. Aerosols may also be responsible for the loss of harvests, human health problems and ecological disasters. Thus, this detailed study of aerosol properties on a global scale could not be more timely.
Atmospheric mineral dust has a large impact on the earth's radiation balance and climate. The radiative effects of mineral dust depend on factors including, particle size, shape, and composition which can all be extremely complex. Mineral dust particles are typically irregular in shape and can include sharp edges, voids, and fine scale surface roughness. Particle shape can also depend on the type of mineral and can vary as a function of particle size. In addition, atmospheric mineral dust is a complex mixture of different minerals as well as other, possibly organic, components that have been mixed in while these particles are suspended in the atmosphere. Aerosol optical properties are investigated in this work, including studies of the effect of particle size, shape, and composition on the infrared (IR) extinction and visible scattering properties in order to achieve more accurate modeling methods. Studies of particle shape effects on dust optical properties for single component mineral samples of silicate clay and diatomaceous earth are carried out here first. Experimental measurements are modeled using T-matrix theory in a uniform spheroid approximation. Previous efforts to simulate the measured optical properties of silicate clay, using models that assumed particle shape was independent of particle size, have achieved only limited success. However, a model which accounts for a correlation between particle size and shape for the silicate clays offers a large improvement over earlier modeling approaches. Diatomaceous earth is also studied as an example of a single component mineral dust aerosol with extreme particle shapes. A particle shape distribution, determined by fitting the experimental IR extinction data, used as a basis for modeling the visible light scattering properties.
Helping you better understand the processes, instruments, and methods of aerosol spectroscopy, Fundamentals and Applications in Aerosol Spectroscopy provides an overview of the state of the art in this rapidly developing field. It covers fundamental aspects of aerosol spectroscopy, applications to atmospherically and astronomically relevant problem
This volume is a collection of review articles by scientists who have pioneered many of the recent advances in studies of the optical effects of small particles. The book begins with a review of the multitude of sharp dielectric resonances which exist in all optical spectra as a result of particle size and shape. Latest advances in absorption and fluorescence spectroscopy of a single particle and/or an ensemble of particles are also discussed, as well as advances in the energy transfer mechanisms for molecules embedded in the particle. The effects of laser-induced heating on a single particle are reviewed in terms of the hydrodynamics and thermodynamics of the liquid droplet and its ambient gas surrounding. The limits of applying bulk optical constants to small particles which lie between the bulk substance and the quantum-sized substance are also presented.
It has been thirty years since one of the authors (EJD) began a collaboration with Professor Milton Kerker at Clarkson University in Potsdam, New York using light scattering methods to study aerosol processes. The development of a relatively short-lived commercial particle levitator based on a modification of the Millikan oil drop experiment attracted their attention and led the author to the study of single droplets and solid microparticles by levitation methods. The early work on measurements of droplet evaporation rates using light scattering techniques to determine the size slowly expanded and diversified as better instrumentation was developed, and faster computers made it possible to perform Mie theory light scattering calculations with ease. Several milestones can be identified in the progress of single microparticle studies. The first is the introduction of the electrodynamic balance, which provided more robust trapping of a particle. The electrodynamic levitator, which has played an important role in atomic and molecular ion spectroscopy, leading to the Nobel Prize in Physics in 1989 shared by Wolfgang Paul of Bonn University and Hans Dehmelt of the University of Washington, was easily adapted to trap microparticles. Simultaneously, improvements in detectors for acquiring and storing light scattering data and theoretical and experimental studies of the interesting optical properties of microspheres, especially the work on morphology dependent resonances by Arthur Ashkin at the Bell Laboratories, Richard Chang, from Yale University, and Tony Campillo from the Naval Research Laboratories in Washington D. C.
Scientists have been observing a change in the climate since the beginning of the 20th century that cannot be attributed to any of the natural influences of the past. Natural and anthropogenic substances and processes perturb the Earth's energy budget, contributing to climate change. In particular, aerosols (particles suspended in air) have long been recognized to be important in processes throughout the atmosphere that affect climate. They directly influence the radiative balance of the Earth's atmosphere, affect cloud formation and properties, and are also key air pollutants that contribute to a variety of respiratory and cardiovascular diseases. Despite their importance, aerosol particles are less well-characterized than greenhouse gases with respect to their sources, temporal and spatial concentration distribution, and physical and chemical properties. This uncertainty is mainly caused by the variable and insufficiently understood sources, formation and transformation processes, and complex composition of atmospheric particles. Instruments that can precisely and accurately measure and characterize the aerosol physical and chemical properties are in great demand. Atmospheric relative humidity (RH) has a crucial impact on the particles' optical properties; the RH dependence of the particle extinction coefficient is an important parameter for radiative forcing and thus climate change modeling. In this work a Humidity-Controlled Cavity Ring-Down (HC-CRD) aerosol optical instrument is described and its ability to measure RH dependent extinction coefficients and related hygroscopicity parameters is characterized.