Atmospheric particulate matter composition

Table 14.5. Atmospheric particulate matter elemental composition and the relative concentrations (Skua Lake, 1986-1987)...

When a liquid or solid substance is emitted to the air as particulate matter, its properties and effects may be changed. As a substance is broken up into smaller and smaller particles, more of its surface area is exposed to the air. Under these circumstances, the substance, whatever its chemical composition, tends to combine physically or chemically with other particles or gases in the atmosphere. The resulting combinations are frequently unpredictable. Very small aerosol particles (from 0.001 to 0.1 Im) can act as condensation nuclei to facilitate the condensation of water vapor, thus promoting the formation of fog and ground mist. Particles less than 2 or 3 [Lm in size (about half by weight of the particles suspended in urban air) can penetrate the mucous membrane and attract and convey harmful chemicals such as sulfur dioxide. In order to address the special concerns related to the effects of very fine, iuhalable particulates, EPA replaced its ambient air standards for total suspended particulates (TSP) with standards for particlute matter less than 10 [Lm in size (PM, ). 

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... 

Mean Chemical Composition and Atmospheric Concentrations of Suspended Particulate Matter Sampled by the United States Environmental Protection Agency s Inhalable Particle and National Air Surveillance Networks—/rg/m and Percentage of Total Mass Sampled, 1980... 

The major purpose of ambient particulate sampling is to obtain mass concentration and chemical composition data, preferably as a function of particle diameter. This information is valuable for a variety of problems effects on human health, identification of particulate matter sources, understanding of atmospheric haze, and particle removal processes. 

The three major characteristics of particulate pollutants in the ambient atmosphere are total mass concentration, size distribution, and chemical composition. In the United States, the PM q concentration, particulate matter with an aerodynamic diameter <10 /nm, is the quantity measured for an air quality standard to protect human health from effects caused by inhalation of suspended particulate matter. As shown in Chapter 7, the size distribution of particulate pollutants is very important in understanding... 

A high-nickel alloy is used for increased strength at elevated temperature, and a chromium content in excess of 20% is desired for corrosion resistance. An optimum composition to satisfy the interaction of stress, temperature, and corrosion has not been developed. The rate of corrosion is directly related to alloy composition, stress level, and environment. The corrosive atmosphere contains chloride salts, vanadium, sulfides, and particulate matter. Other combustion products, such as NO, CO, CO2, also contribute to the corrosion mechanism. The atmosphere changes with the type of fuel used. Fuels, such as natural gas, diesel 2, naphtha, butane, propane, methane, and fossil fuels, will produce different combustion products that affect the corrosion mechanism in different ways. 

Airborne particulate matter, which includes dust, dirt, soot, smoke, and liquid droplets emitted into the air, is small enough to be suspended in the atmosphere. Airborne particulate matter may be a complex mixture of organic and inorganic substances. They can be characterized by their physical attributes, which influence their transport and deposition, and their chemical composition, which influences their effect on health. The physical attributes of airborne particulates include mass concentration and size distribution. Ambient levels of mass concentration are measured in micrograms per cubic meter (mg/m ) size attributes are usually measured in aerodynamic diameter. Particulate matter (PM) exceeding 2.5 microns (/i) in aerodynamic diameter is generally defined as coarse particles, while particles smaller than 2.5 mm (PMj,) are called fine particles. 

Air The composition of gases that make up the earth s atmosphere, approximately 79% nitrogen and 21% oxygen. Pure air has no definite meaning regarding the proportion of these gases this term is used to imply the absence of industrial particulate matter. 

The deposition velocities depend on the size distribution of the particulate matter, on the frequency of occurrence and intensity of precipitation, the chemical composition of the particles, the wind speed, nature of the surface, etc. Typical values of and dj for particles below about 1 average residence time in the atmosphere for such particles is a few days. 

The relationship of particle size to molecular composition is highly significant. (2). Particles below 1-3 fun (submicron size class) in diameter are considered respirable by animals, in that this material can reach the lower alveoli of the lung. Particle size information may be used to determine the sources of various atmospheric pollutants. Particulate matter formed from gaseous pollutants tends to be found in the less than the 1-3 /nm particle diameter size range. Supermicron sized particles (particles greater than 1- 3 typically originate from primary emission sources, (i.e., stack emissions, vehicles, soil). 

We now consider the abstract presented in excerpt 8G, which reverses the emphases observed in excerpts 8C-8F. In excerpt 8G, moves 1 and 2 comprise the bulk of the abstract, and move 3 is just a single sentence. Much of the abstract is used to elucidate important gaps in the field that (1) a size-based standard for regulating atmospheric particulate matter is inadequate because it does not take into account chemical composition, and (2) compositional analyses are difficult, especially for metals, because they often exist in multiple oxidation states. These gaps help to establish the relevance of the authors work. Only in the last sentence do the authors mention their work specifically (move 3). Here, they identify their method (micro-XANES) and tell readers what results will be presented at the conference. 

Move 1] Currently atmospheric particulate matter is regulated based on various size categories because of the apparent association between particle size and adverse health effects. [Move 2] However, the current size-based understanding of atmospheric particles is relatively crude because it does not account for differences in the chemical composition of these particles. Presumably a chemically reactive particle has a greater potential for damage than a chemically inert particle of comparable size. Of the metals potentially... 

The Beijing area in north China is well situated for investigating relationships between the elemental composition of atmospheric particulate matter and air mass movements. The municipality of Beijing (Beijing shi) has a population of 7 million, half of whom live in the city proper, and pollution sources of trace gases... 

Lindberg, J. D., 1975. The composition and optical absorption coefficient of atmospheric particulate matter, Opt. Quant. Electron., 7, 131-139. 

Beautiful blue skies and pink-color sunsets are direct consequences of the existence of an atmosphere. Sunlight scattered by gaseous molecules around our planet is responsible for the blue color of the sky. When we look at sunless sky, the light we observe is mainly scattered light. On the other hand, particulate matter also scatters light but toward the red side of the visible spectrum, and therefore small airborne dust particles produce a spectacular pink-reddish color. In this chapter we discuss the location, composition, and some properties of our atmosphere. 

Thus, in general, the anthropogenic aerosol is not only the aerosol, whose chemical composition and other parameters differ from those of natural particles, but also natural particulate matter generated by nonnatural mechanisms. For instance, the aerosols, both injected into the atmosphere and formed in situ as a result of nuclear explosions in the atmosphere. 

Input is balanced by output in a steady-state system. The concentration of an element in seawater remains constant if it is added to the sea at the same rate that it is removed from the ocean water by sedimentation. Input into the oceans consists primarily of (1) dissolved and particulate matter carried by streams, (2) volcanic hot spring and basalt material introduced directly, and (3) atmospheric inputs. Often the latter two processes can be neglected in the mass balance. Output is primarily by sedimentation occasionally, emission into the atmosphere may have to be considered. Note that the system considered is a single box model of the sea, that is, an ocean of constant volume, constant temperature and pressure, and uniform composition. 

Mroz, E.J. and Zoller, W.H., 1975. Composition of atmospheric particulate matter from the eruption of Heimaey, Iceland. Science, 190 461—464. 

Iron may be supplied to the euphotic zone from advective and diffusive processes within the ocean as well as by atmospheric deposition of particulate matter to the ocean surface. In coastal areas the water composition can be affected by the contribution of rivers and in polar regions the glacier effect, in terms of ice melt and erosion during the ice flow, can be important. 

Table 14.7. Atmospheric particulate matter concentrations (Skua Lake, Italian station, 1988- elemental -1989) composition and the relative...

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