Air pollutants primary

Chemicals can be labeled as either a primary air pollutant or secondary air pollutant. Primary air pollutants are those such as carbon monoxide and sulfur dioxide that enter the atmosphere directly as a result of human or natural events. Carbon monoxide s primary source in the atmosphere is the incomplete combustion of gasoline. Hundreds of different chemicals are present in gasoline. The combustion of octane, C Hj, can be used to represent the general reaction of hydrocarbons in an automobile engine to produce energy ... 

Air pollution occurs when the concentration of natural and/or man-made substances in the atmosphere becomes excessive and the air becomes toxic. Emissions from transportation, industry, and agriculture are man-made sources of air pollution. Primary pollutants are gases, liquids, and particulates dispersed into the atmosphere through either man-made or natural processes. In the United States, the primary pollutants are carbon monoxide, sulfur dioxide, nitrogen oxides, volatile organic compounds (VOCs), and particulate matter (soot, dust, etc.). Secondary pollutants are derived from primary pollutants that undergo a chemical reaction and become a different type of toxic material. In the United States, secondary pollutants are ozone, photochemical smog, and acid rain. 

In discussing atmospheric pollution, it is important to make the distinction between primary and secondary air pollutants. Primary air pollutants are those that are pollutants in the form in which they are emitted into the atmosphere. An example would be light-scattering fine ash particles ejected from a smokestack. Secondary air pollutants are those that are formed from other substances by processes in the atmosphere. A prime example of a secondary pollutant develops when otherwise relatively innocuous levels of hydrocarbons (including terpenes from pine and citrus trees) and NO are emitted into the atmosphere and subjected to ultraviolet radiation from the sun, resulting in a noxious mixture of ozone, aldehydes, organic oxidants, and fine particles called photochemical smog. 

The Clean Air Act (CAA) limits the emission of pollutants into the atmosphere and protects human health and the environment from the effects of airborne pollution. The EPA established National Ambient Air Quality Standards (NAAQS) for several substances. The NAAQS provide the public some protection from toxic air pollutants. Primary responsibility for meeting the requirements of the CAA rests with each state. States must submit plans for achieving NAAQS compliance. Under section 112 of the CAA, the EPA has the authority to designate hazardous air pollutants and set national emission standards for hazardous air pollutants. Common air pollutants include the following (1) ozone, (2) nitrogen dioxide, (3) carbon monoxide, (4) particulate matter, and (5) sulfur dioxide. 

Air pollution can be considered to have three components sources, transport and transformations in the atmosphere, and receptors. The source emits airborne substances that, when released, are transported through the atmosphere. Some of the substances interact with sunlight or chemical species in the atmosphere and are transformed. Pollutants that are emitted directiy to the atmosphere are called primary pollutants pollutants that are formed in the atmosphere as a result of transformations are called secondary pollutants. The reactants that undergo transformation are referred to as precursors. An example of a secondary pollutant is O, and its precursors are NMHC and nitrogen oxides, NO, a combination of nitric oxide [10102-43-9] NO, and NO2. The receptor is the person, animal, plant, material, or ecosystem affected by the emissions. 

The lead-bearing components ate released from the case and other nordead-containing parts, followed by the smelting of the battery plates, and refinement to pure lead or specification alloys. The trend toward battery grid alloys having Httle or no antimony, increases the abiHty of a recovery process to produce soft lead (refined). As requited in the production of primary lead, each step in the secondary operations must meet the environmental standards for lead concentration in ait (see Air pollution Lead compounds, industrial toxicology). 

Air pollution (qv) problems are characteri2ed by their scale and the types of pollutants involved. Pollutants are classified as being either primary, that is emitted direcdy, or secondary, ie, formed in the atmosphere through chemical or physical processes. Examples of primary pollutants are carbon monoxide [630-08-0] (qv), CO, lead [7439-92-1] (qv), Pb, chlorofluorocarbons, and many toxic compounds. Notable secondary pollutants include o2one [10028-15-6] (qv), O, which is formed in the troposphere by reactions of nitrogen oxides (NO ) and reactive organic gases (ROG), and sulfuric and nitric acids. 

Aerosol Dynamics. Inclusion of a description of aerosol dynamics within air quaUty models is of primary importance because of the health effects associated with fine particles in the atmosphere, visibiUty deterioration, and the acid deposition problem. Aerosol dynamics differ markedly from gaseous pollutant dynamics in that particles come in a continuous distribution of sizes and can coagulate, evaporate, grow in size by condensation, be formed by nucleation, or be deposited by sedimentation. Furthermore, the species mass concentration alone does not fliUy characterize the aerosol. The particle size distribution, which changes as a function of time, and size-dependent composition determine the fate of particulate air pollutants and their... 

Models can be used to study human exposure to air pollutants and to identify cost-effective control strategies. In many instances, the primary limitation on the accuracy of model results is not the model formulation, but the accuracy of the available input data (93). Another limitation is the inabiUty of models to account for the alterations in the spatial distribution of emissions that occurs when controls are appHed. The more detailed models are currendy able to describe the dynamics of unreactive pollutants in urban areas. 

Carbon monoxide was discovered in 1776 by heating a mixture of charcoal and 2inc oxide. It provided a source of heat to industry and homes as a component of town gas and was used as a primary raw material in German synthetic fuel manufacture during World War II its compounds with transition metals have been studied extensively (see Carbonyls). Most recently, carbon monoxide emission from vehicle exhausts has been recognized as a primary source of air pollution (qv). 

A primary concern in coal-fired power generation is the release of air pollutants. Limits on SO2 output, 0.52 g/MJ equivalent of coal input to a new plant, have been estabflshed. Eor a bituminous coal of 27.9 MJ/kg there is thus an upper limit of 0.72% sulfur content. Relatively few coals can meet this requirement. The U.S. Department of Energy indicated recoverable reserves of 420 x 10 t in 1987 (2) that were categorized by sulfur content 33.5% had 0.6% S or less, 15.4% had between 0.61% and 0.83% S, 16.1% had between 0.84 and 1.67% S, 12.4% had between 1.68 and 2.50% S, and 22.6% had more than 2.5% S. The lowest sulfur coal, 86%, is found west of the Mississippi River, mainly in Montana and Wyoming, quite distant from the electric power demand centers in the East. A trend to utilization of the western coals has developed. 

There are two different types of air pollution problems in urban areas. One is the release of primary pollutants (those released directly from sources). The other is the formation of secondary pollutants (those that are formed through chemical reactions of the primary pollutants). 

At least three types of problems contribute to air pollution problems on the regional scale. One is the carryover of urban oxidant problems to the regional scale. With the existence of major metropolitan areas in close proximity, the air from one metropolitan area, containing both secondary pollutants formed through reactions and primary pollutants, flows on to the adjacent metropolitan area. The pollutants from the second area are then added on top of the "background" from the first. 

There are several different strategies for air pollution control. The strategy just discussed and shown in Fig. 5-1 is called the air quality management strategy. It is distinguished from other strategies by its primary reliance on the development and promulgation of ambient air quality standards. 

Air pollutants may enter plant systems by either a primary or a secondary pathway. The primary pathway is analogous to human inhalation. Figure 8-2 shows the cross section of a leaf. Both of the outer surfaces are covered by a layer of epidermal cells, which help in moisture retention. Between the epidermal layers are the mesophyll cells—the spongy and palisade parenchyma. The leaf has a vascular bundle which carries water, minerals, and carbohydrates throughout the plant. Two important features shown in Fig. 8-2 are the openings in the epidermal layers called stomates, which are controlled by guard cells which can open and close, and air spaces in the interior of the leaf. 

The U.S. Clean Air Amendments of 1977 define two kinds of air quality standards primary standards, levels that will protect health but not necessarily prevent the other adverse effects of air pollution, and secondary standards, levels that will prevent all the other adverse effects of air pollution (Table 22-7). The amendments also define air quality levels that cannot be exceeded in specified geographic areas for "prevention of significant deterioration" (PSD) of the air of those areas. Although they are called "increments" over "baseline air quality" in the law, they are in effect tertiary standards, which are set at lower ambient levels than either the primary or secondary standards (Table 22-8). 

Air pollution control systems using wet scrubbers will remove some water-soluble gases, but the removal of particulate matter is the primary concern for a control system. The air pollution control system, therefore, is usually a single device such as a wet scrubber, small-diameter multiple cyclones, fabric filters, or ESPs. The multicyclones are the least expensive system and the ESPs the most expensive. 

Air Pollution Emissions from Primary Zinc Processing... 

With torroidal air flow, combustors will operate without visible smoke when properly developed for a primary-zone equivalence ratio below 1.5. Visible smoke is an air-pollution problem. 

Combustion processes are the most important source of air pollutants. Normal products of complete combustion of fossil fuel, e.g. coal, oil or natural gas, are carbon dioxide, water vapour and nitrogen. However, traces of sulphur and incomplete combustion result in emissions of carbon monoxide, sulphur oxides, oxides of nitrogen, unburned hydrocarbons and particulates. These are primary pollutants . Some may take part in reactions in the atmosphere producing secondary pollutants , e.g. photochemical smogs and acid mists. Escaping gas, or vapour, may... 

Primary Standard a pollution standard based on human health effects. Primary standards are set for criteria air pollutants. See also secondary standard. 

Develop a list of air pollution issues and discuss possible permitting requirments you may have to face with a treatment plant that relies on both primary and secondary clarifiers for municipal sewerage treatment. 

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