Aerosol instruments current

Figure 2. Size and time scales covered by current aerosol instruments.

The arsenal of aerosol measurement methods has expanded dramatically over recent years, but a number of needs for fundamental research into the nature and origins of the atmospheric aerosol cannot be met by the current instrumentation. Instrumentation that has proven most valuable in the chemical characterization of the atmospheric aerosol is woefully inadequate either for following the chemical dynamics of aerosols because of the rapid changes that occur in homogeneous reacting systems or for unraveling the complexity of the aerosol products. 

Ultraviolet) instrument and from SAGE II (Stratospheric Aerosol and Gas Experiment II), together with supporting data from ozonesondes and satellite instruments such as SME (Solar Mesosphere Explorer) and TOMS (Total Ozone Mapping Spectrometer). The model interpolates monthly ozone values to its timestep and this time-varying ozone repeats every simulation year. The model currently does not allow the ozone to become interactive, neither does it represent any change in ozone due to chemical processes, although work is underway to incorporate these features. 

If one focuses on the particle size distribution function as a central framework for describing aerosols, one can conveniently classify the measurement instruments according to the properties of the size distribution function. Organization of instrumentation gives perspective on the ideal requirements as contrasted with the practical limits imposed by current technology. An idealized hierarchy was suggested by S. K. Friedlander in 1977. As an ideal, the modern aerosol analyzer gives a continuous... 

There are instruments capable of measuring the composition of individual particles (Chapter 6)t and eventually it will be possible to determine the size-composition p.d.f. Currently, such measurements are made on a research basis in practice the average composition of the particles in a discrete size interval is determined by collecting an aerosol sample over a period of several hours using a cascade impactor (Chapter 6) and analyzing the material on each stage chemically. The concentration measured in this way is related to g(u, wj,. rt. r, f) as follows ... 

In this section, we briefly review three types of instruments, the optical particle counter, electrical aerosol classifier, and diffusion battery. These system.s are based on very dilTerent physical characteristics of the aerosols. The optical counters respond to signals from individual particles. The electrical analyzers depend on the measurement of a current carried by a slreaJTi of cbrnged aerosol particles. The ditfusion battery also depends on the behavior of particle clouds. The system often used to cover the size range from about 10 nm to 10 /jm is a combination of (a) the electrical analyzer up to about 0.2 jum and (b) the optical particle counter over the rest of the range. 

The technical portion of the NOSH Consortium filtration study focused on three areas where current aerosol filtration methods and instrumentation can be explored, including (1) isolating and quantifying particle losses due solely to aerosol particle interactions with filter media, (2) measuring the... 

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