Physical characteristics atmosphere

The methods just noted tell something about the physical characteristics of atmospheric particulate matter but nothing about its chemical composition. One can seek this kind of information for either individual particles or all particles en masse. Analysis of particles en masse involves analysis of a mixture of particles of many different compounds. How much of... 

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. 

The unique physical characteristics of the Great Lakes also contribute to their sensitivity to toxic substance inputs. The vast surface areas of the lakes makes atmospheric contributions of these chemicals, even at low concentrations, quantitatively significant. The relatively large ratio of the lake surface to drainage basin area, and the fact that the boundary of the drainage basin in some locations... 

Table 7-2 includes most of the main gaseous constituents of the troposphere with observed concentrations. In addition to gaseous species, the condensed phases of the atmosphere (i.e. aerosol particles and clouds) contain numerous other species. The physical characteristics and transformations of the aerosol state will be discussed later in Section 7.10. The list of major gaseous species can be organized in several different ways. In the table, it is in order of decreasing concentration. We can see that there are five approximate categories based simply on concentration ... 

Cyclodimer 3 proved to be somewhat difficult to manipulate, thus contributing to the complexity of its characterization. The bowed diacetylenic linkages revealed in the X-ray data impart surprising physical characteristics to the molecule. The energy-rich hydrocarbon was sufficiently strained that it decomposed explosively upon grinding (i. e. preparing a Nujol mull) or when heated above 80°C. At room temperature, crystals blackened within a few days and apparently auto-polymerized, even when stored under vacuum in the dark. Only dilute solutions of 3 in benzene or pyridine were fairly stable over time, especially when stored cold under an inert atmosphere. 

The abundance patterns of individual stars of different ages and environments enable us to unlock the evolutionary history of galaxies. Many physical characteristics of a galaxy may change over time, such as shape and colour, however the metal content and abundance ratios of stellar atmospheres are not so easy to tamper with. Stars retain the chemical imprint of the interstellar gas out of which they formed, and metals can only increase with time. This method to study galaxy evolution has been elegantly named Chemical Tagging [2],... 

The physical characteristics of individual particles also are of environmental significance. For example, the smaller particles (diameters on the order of 1 micrometer of less) generally are most important in that they have very long atmospheric residence times (18), are least effectively controlled by pollution control devices (19), are preferentially deposited in the pulmonary regions of the lung (20,21), and may be most enriched in toxic species on a specific concentration (iig/g) basis (22-24). 

Improved control devices now frequently installed on conventional coal-utility boilers drastically affect the quantity, chemical composition, and physical characteristics of fine-particles emitted to the atmosphere from these sources. We recently sampled fly-ash aerosols upstream and downstream from a modern lime-slurry, spray-tower system installed on a 430-Mw(e) coal utility boiler. Particulate samples were collected in situ on membrane filters and in University of Washington MKIII and MKV cascade impactors. The MKV impactor, operated at reduced pressure and with a cyclone preseparator, provided 13 discrete particle-size fractions with median diameters ranging from 0,07 to 20 pm with up to 6 of the fractions in the highly respirable submicron particle range. The concentrations of up to 35 elements and estimates of the size distributions of particles in each of the fly-ash fractions were determined by instrumental neutron activation analysis and by electron microscopy, respectively. Mechanisms of fine-particle formation and chemical enrichment in the flue-gas desulfurization system are discussed. 

As a result of these widespread implications, understanding their direct sources, their formation from chemical reactions in air, their fates, and how their physical and chemical properties determine health and visibility impacts is critical. While many of the overall chemical and physical characteristics of particles have been elucidated, as we shall see in this chapter, there remain large gaps in our knowledge in areas central to policy and regulatory issues (National Research Council, 1998). As a result, this is a particularly active and rapidly evolving area of research in atmospheric chemistry. 

Inhalation. The respiratory system is an important portal of entry, and for evaluation purposes animals must be exposed to atmospheres containing potential toxicants. The generation and control of the physical characteristics of such contaminated atmospheres is technically complex and expensive in practice. The alternative—direct instillation into the lung through the trachea—presents problems of reproducibility as well as stress and for these reasons is generally unsatisfactory. 

Over a considerable fraction of the high-latitude global ocean, sea ice forms a boundary between the atmosphere and the ocean, and considerably influences their interaction. The details and consequences of the role of sea ice in the global climate system are still poorly known. Improved knowledge is needed of the broad-scale time-varying distributions of the physical characteristics of sea ice, particularly ice thickness and the overlying snow-cover thickness, in both hemispheres, and the dominant processes of ice formation, modification, decay and transport which influence and determine ice thickness, composition and distribution. We do not know how accurate present model predictions of the sea ice responses to climate change are, since the representation of much of the physics is incomplete in many models, and it will be necessary to improve coupled models considerably to provide this predictive capability. 

Whitby, K.T. (1978) The physical characteristics of sulfur aerosols. Atmospheric Environment, 12, 135-59. 

The very shallow ( 1 txm) layer of air in contact with the surfaces, where stream lines for air-flow are approximately parallel to the surface and turbulence is suppressed by the viscosity of the air, is known as the laminar boundary layer. The thickness of this layer is determined by physical characteristics of the object (size, shape and surface structure) and by the velocity of air outside the laminar boundary layer. Although gases and small particles are transported by the same mechanism and at about the same rates in the free atmosphere, their transport through the laminar boundary layer differs considerably. Gases must diffuse through this layer by molecular diffusion, the concentration gradient and diffusion coefficient for the gas in question controlling the rate of transfer. 

Many of the physical characteristics of the atmosphere, such as wind, temperature, cloud cover, humidity, and precipitation, are easily perceived. Sometimes, chemicals in the atmosphere also can be observed, as in smoke plumes and smog, and their physical transport tracked downwind just as downstream transport of substances in a river can be measured. Other atmospheric processes are less apparent to the unaided observer, however, occurring either on the microscopic scale of a chemical reaction, or on a global scale, or at high altitudes. Such processes may be detected only by instrumentation on satellites or some high-altitude aircraft. 

The emphasis in chemical agent modeling appears to be on using plume models to predict the spread and concentration levels of a chemical release. However, the accuracy of such predictions is highly dependent on knowledge of the precise location and magnitude of the chemical release, the physical characteristics of the plume (e.g., the initial particle-size distribution), and detailed knowledge of the stochastic nature of local atmospheric dispersion. In reality, these parameters are likely to be poorly known in any cleverly executed asym-... 

Voyager 1 flew by Saturn on November 12, 1980, at a distance of three planet radii from the planet s atmosphere, while Voyager 2 flew past the planet on August 26, 1981, at a distance of 2.67 planet radii. The two spacecraft carried a variety of instruments that allowed them to measure the chemical composition of the planet s atmosphere, the presence and strength of its magnetic field, any electrical properties associated with the planet, and other physical characteristics of the planet, its satellites, and ring system. 

As such, it is absolutely clear that the chemical composition of the atmosphere as well as the physical characteristics of condensed phase trace species are of leading importance as determinants of climate. A well-known example is the increase in the temperature of the Earth s surface due to the absorption of infrared radiation from the Earth s surface by CO2 in the air (see box). Without CO2, the Earth s surface would be several degrees cooler than at present, depending on cloud cover, water vapor, and other controlling factors. Of course, there is substantial concern over the secular increase of CO2, which will double from its pre-industrial level by the early to mid-twenty-first century. 

To clarify the mechanisms of the clay-reinforced carbonaceous char formation, which may be responsible for the reduced mass loss rates, and hence the lower flammability of the polymer matrices, a number of thermo-physical characteristics of the PE/MMT nanocomposites have been measured in comparison with those of the pristine PE (which, by itself is not a char former) in both inert and oxidizing atmospheres. The evolution of the thermal and thermal-oxidative degradation processes in these systems was followed dynamically with the aid of TGA and FTIR methods. Proper attention was paid also to the effect of oxygen on the thermal-oxidative stability of PE nanocomposites in their solid state, in both the absence as well as in the presence of an antioxidant. Several sets of experimentally acquired TGA data have provided a basis for accomplishing thorough model-based kinetic analyses of thermal and thermal-oxidative degradation of both pristine PE and PE/MMT nanocomposites prepared in this work. 

Figure 4-5. Schematic diagram of the solar atmosphere with its different layers and physical characteristics.

Understanding the formation of the ions requires knowledge of the spectral distribution of solar radiation at short wavelengths, the structure of solar and galactic cosmic rays, as well as the chemical composition of the atmosphere and its physical characteristics such as pressure, temperature, and transport. The variations of solar activity must also be considered. 

Further investigations, funded by the European Commission CRAFT programme, have also been undertaken to develop a leather with both the resistance to acidic atmospheric attack exhibited by mineral tanned leathers and the physical characteristics of vegetable-tanned skins demanded by book binders and other leather workers. As a result of this work, leathers with these properties are now available commercially. 

FAVAP and PIERGIOVANNIL (1992), Carbon dioxide solnbility in foods packaged with modified atmosphere. II Correlation with some chemical-physical characteristics and composition. Industrie Alimentari, 31, 424-430. 

Clay particles formed before life began, so primordial soils had essentially the same chemical and physical characteristics as today s soils. Clays could adsorb and concentrate simple organic molecules as they fell in rain, or adsorb them directly from the atmosphere. Amino acids, for example, have been shown to polymerize when adsorbed on clay surfaces benzene and phenol polymerize spontaneously on Fe(III)- and Cu(lI)-coated clays. Whether such reactions actually led to the origin of life is speculation, but these reactions are much more likely in soils than in tidal pools. 

It would be superfluous to review here the story of e aq in the radiation chemistry of aqueous solutions. High energy radiations cause ionizations and the free electrons so generated dissipate their excess energy and are eventually trapped in solvation shells. The discovery of hydrated electrons showed that electrons in water were chemical entities (as distinct from possessing purely physical characteristics) in having diffusion properties, size and sphere of influence, associated ion atmosphere, and reaction rate parameters all of which are comparable to normal chemical reagents. 

An air pollutant is a component which is able, either directly, or after relevant conversions occurring in the atmosphere, to damage or threaten living organisms and to affect adversely the environment. Depending on chemical and physical characteristics, we can divide substances polluting the air into several groups ... 

---