Carbon monoxide primary pollutant

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. 

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). 

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... 

Emissions to the atmosphere from ammonia plants include sulfur dioxide (SOj), nitrogen oxides (NOJ, carbon monoxide (CO), carbon dioxide (COj), hydrogen sulfide (HjS), volatile organic compounds (VOCs), particulate matter, methane, hydrogen cyanide, and ammonia. The two primary sources of pollutants, with typical reported values, in kilograms per ton (kg/t) for the important pollutants, are as follows ... 

Transportation accounts for about one-fourth of the primary energy consumption in the United States. And unlike other sectors of the economy that can easily switch to cleaner natural gas or electricity, automobiles, trucks, nonroad vehicles, and buses are powered by internal-combustion engines burning petroleum products that produce carbon dioxide, carbon monoxide, nitrogen oxides, and hydrocarbons. Efforts are under way to accelerate the introduction of electric, fuel-cell, and hybrid (electric and fuel) vehicles to replace sonic of these vehicles in both the retail marketplace and in commercial, government, public transit, and private fleets. These vehicles dramatically reduce harmful pollutants and reduce carbon dioxide emissions by as much as 50 percent or more compared to gasoline-powered vehicles. 

The Clean Air Act recognizes a number of so-called primary air pollutants, and the EPA has established standards for these substances. Ozone, nitrogen oxides, and sulfur dioxide are among these (the others are carbon monoxide and lead, discussed below, and total suspended particulates ). The EPA s standard for ozone is 0.08 parts of the gas per million parts of air (0.08 ppm), averaged over eight hours. Standards also exist for the oxides of sulfur and nitrogen. These are designed to prevent chronic respiratory toxicity of any kind. 

The classes of major primary pollutants that are important in urban areas are listed in Table 2-1. The pollutants most responsible for oxidant formation in the air are the nitrogen oxides, hydrocarbons, aldehydes, and carbon monoxide. The internal-combustion engine is a major source of emission of these primary pollutants, although many stationary sources. 

Rollback Both linear rollback and modified rollback models were used by Barth to examine federal motor-vehicle goals for standards governing carbon monoxide, hydrocarbon, and oxides of nitrogen. The linear rollback principle was suggested and applied to these primary pollutants ... 

The time-series analysis results of Merz et were expressed in first-order empirical formulas for the most part. Forecasting expressions were developed for total oxidant, carbon monoxide, nitric oxide, and hydrocarbon. Fitting correlation coefficients varied from 0.547 to 0.659. As might be expected, the best results were obtained for the primary pollutants carbon monoxide and nitric oxide, and the lowest correlation was for oxidant. This model relates one pollutant to another, but does not relate emission to air quality. For primary pollutants, the model expresses the concentrations as a function of time. 

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 ... 

The air emissions of fossil fuel combustion are dispersed and diluted within the atmosphere, eventually falling or migrating to the surface of the Earth or ocean at various rates. Until recently, most attention was focused on the so-called primary pollutants of fossil fuel combustion that are harmful to human health oxides of sulphur and nitrogen, carbon monoxide, suspended particles (including soot), heavy metals, and products of incomplete combustion. These pollutants are most concentrated in urban or industrialized areas close to large or multiple sources. However, the primary pollutants may interact with each other, and with atmospheric constituents and sunlight, forming secondary pollutants that disperse far beyond the urban-... 

The health effects of carbon monoxide make it a primary air pollutant. The federal government has established national standards for CO to protect the general population from this toxic gas. The national standard is 9 ppm (parts per million) averaged over 8 hours or 35 ppm averaged over 1 hour. Table 23.1 summarizes the health effects associated with different CO concentrations. 

Reductions in ambient concentrations of some but certainly not all air pollutants have taken place over the past decade. In the United States, the US Environmental Protection Agency (EPA) is the primary agency responsible for promulgating and regulating air pollution standards. National ambient air quality standards (NAAQS) have been established for six classes of outdoor pollutants lead, carbon monoxide, ozone, nitrogen dioxide, sulfur dioxide, and particulate matter. These standards (Table 1) are periodically reviewed and updated based on currently available data regarding adverse health effects. Bases on new evidence, the standards for ozone and... 

Environmental criteria have been established for many of these, but the utility and applicability of such criteria for indoor environments is controversial for at least four reasons. Eor example, the goals of the threshold limit values often do not include preventing irritation, a primary concern in indoor environments with requirements for close eye work at video display terminals. For most of the pollutant categories, the problem of interactions, commonly termed the multiple contaminants problem , remains inadequately defined. Even for agents that are thought to affect the same receptor, such as aldehydes, alcohols, and ketones, no prediction models are well established. Finally, the definition of representative compounds for measurement is unclear. That is, pollutants must be measurable, but complex mixtures vary in their composition. It is unclear whether the chronic residual odor annoyance from environmental tobacco smoke correlates better with nicotine, particulates, carbon monoxide, or other pollutants. The measure total volatile organic compounds is meanwhile... 

Includes hydrocarbon vapors, nitrogen oxides, sulfur oxides, and carbon monoxide. Tncludes the primary gaseous air pollutants, plus particulates and aerosols. 

Air pollutants are also categorized, like the pollution sourees. The two eategories are primary and secondary pollutants. Primary pollutants are the ehemieals that are direetly emitted to the atmosphere from known sources, while secondary pollutants are the speeies that are formed by the chemical reactions of primary pollutants (Wayne, 2000). Primary pollutants include sulphur oxides (SOx), nitrogen oxides (NOx), carbon monoxide (CO), hydroearbons (HC), and particulate matter (PM). One of the most important secondary pollutants is ozone. 

At local and urban levels, it is essentially a question of vicinity pollution. Several air pollutants are concerned sulphur dioxide, SO2 (primary pollutant) nitrogen oxides NO (primary or secondary pollutants) particulate matter PM (primary and secondary pollutants) carbon monoxide, CO, (primary pollutant) (volatile) organic compounds, HC (or VOCs) (primary and secondary pollutants), and photochemical oxidants, O3, PAN (secondary pollutants). Organic compounds account for a wide range of hydrocarbons and are found in solid, liquid, and gas forms. 

When gasoline, which is a mixture of hydrocarbons, burns in the cylinders of a car engine, the primary products are carbon dioxide and water. Unfortunately, the hydrocarbons are not burned completely, so the exhaust leaving the cylinders also contains some unbumed hydrocarbons and some carbon monoxide, which are serious pollutants. 

This sequence of the reactions describes the formation of a secondary pollutant originating during the interaction of primary pollutants directly in the atmosphere. This production represents the main source of the atmospheric carbon monoxide. 

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