Remote Atmosphere Monitoring

Remote Atmospheric Monitoring.— Several techniques for remote atmospheric monitoring of pollutants, trace gases, etc. by LIDAR (Light Detection And Ranging) have become popular over recent years. Of these, DIAL (Differential Absorption Lidar) spectroscopy would seem to be of most interest to the 

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Table L Average Elemental Concentration in ng/m for Fine Mode Aerosol Particle (dp<2 m) in three Remote Atmospheric Monitoring Stations in the Amazon Basin ( ).

H. Edner, K. Fredriksson. A. Sunesson, S. Svanberg, L. Uneus, W. Wendt Mobile remote sensing system for atmospheric monitoring. Appl. Opt. 26, 4330 (1987)... 

The principal requirement of a sampling system is to obtain a sample that is representative of the atmosphere at a particular place and time and that can be evaluated as a mass or volume concentration. Remote monitoring techniques are discussed in Chapter 15. The sampling system should not alter the chemical or physical characteristics of the sample in an undesirable manner. The major components of most sampling systems are an inlet manifold, an air mover, a collection medium, and a flow measurement device. 

Provisions must be made to ensure worker protection for a process located in a containment building. For example, the atmosphere in the containment structure should be monitored for hazardous vapors, operations should be remotely controlled from outside the containment structures, access should be restricted, and proper personal protective equipment should be used when entry into the containment structure becomes necessary. 

Nickel releases to the atmosphere are mainly in the form of aerosols that cover a broad spectrum of sizes. Particulates from power plants tend to be associated with smaller particles than those from smelters (Cahill 1989 Schroeder et al. 1987). Atmospheric aerosols are removed by gravitational settling and dry and wet deposition. Submicron particles may have atmospheric half-lives as long as 30 days (Schroeder et al. 1987). Monitoring data confrrm that nickel can be transported far from its source (Pacyna and Ottar 1985). Nickel concentrations in air particulate matter in remote, rural, and U.S. urban areas are 0.01-60, 0.6-78, and 1-328 ng/m, respectively (Schroeder et al. 1987). 

Additionally, in two different monitoring campaigns conducted in the center of Milan, Italy, Ciccioli and co-workers (1993) reported 2-nitrofluoranthene, 2-nitropyrene, and 1-nitropyrene were the only ni-troarenes detected. Subsequently, in a comprehensive study of the atmospheric formation and transport of 2-nitrofluoranthene and 2-nitropyrene, they established their presence and levels in ambient particles collected at sites located in urban, suburban, forest, and remote areas in Europe, Asia, America, and Antarctica (Ciccioli et al., 1996, and references therein see also Ciccioli et al., 1995). 

Measurements either from the ground or from satellites have been a major contribution to this effort, and satellite instruments such as LIMS (Limb Infrared Monitor of the Stratosphere) on the Nimbus 7 satellite (I) in 1979 and ATMOS (Atmospheric Trace Molecular Spectroscopy instrument), a Fourier transform infrared spectrometer aboard Spacelab 3 (2) in 1987, have produced valuable data sets that still challenge our models. But these remote techniques are not always adequate for resolving photochemistry on the small scale, particularly in the lower stratosphere. In some cases, the altitude resolution provided by remote techniques has been insufficient to provide unambiguous concentrations of trace gas species at specific altitudes. Insufficient altitude resolution is a handicap particularly for those trace species with large gradients in either altitude or latitude. Often only the most abundant species can be measured. Many of the reactive trace gases, the key species in most chemical transformations, have small abundances that are difficult to detect accurately from remote platforms. 

For long-lived atmospheric species a limited number of measurement stations around the globe may provide an adequate monitoring networic. However, for short-lived species and species having sources that are variable in time and space, the global measurement of concentrations can best be made from remote sounding instrumentation aboard orbiting space-based platforms. 

Emission measurement techniques have in many applications proven very useful in providing an alternative to the absorption method. Emission measurements free the experimenter from the time and position restraints imposed by a celestial source and remove the complications imposed by the necessity to position a remote source in line with the gas sample of interest. One example of the application of emission measurements and their effectiveness, is their use to measure the effluents from sources such as smoke stacks (57). In this application there is usually a temperature differential which allows discrimination between the target and the ambient atmosphere. This type of measurement is most effective in monitoring target gases when they are in close proximity to the source since the target gas temperature soon becomes the same as the ambient atmosphere and their measurement becomes much more difficult if not impossible. 

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