Air pollutants secondary

Frank H, H Scholl, D Renschen, B Rether, A Laouedj, Y Norokorpi (1994) Haloacetic acids, phytotoxic secondary air pollutants. Environ Sci Pollut Res 1 4-14. 

The effects of the secondary air pollutant, ozone, on growing plant systems have been extensively documented phenomenologically, There are at least three proposed mechanisms by which ozone could cause injury, each of which must operate within a framework of temporal sensitivity determined by the state of differentiation of the plant (11),... 

The decomposition of the catalyst beads can cause a secondary air pollution emission consisting of the particulate dust generated by abrasion of the surface of the catalyst. Operating cost for catalyst replacement varies directly with catalyst attrition rate. The system can process waste streams with VOC concentrations of up to 25% of the lower explosive limit (LEL). The proprietary catalyst contains up to 10% chromium, including 4% hexavalent chromium. This could lead to the emission of hexavalent chromium in some applications of the technology. 

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 ... 

Of particular interest in terms of atmospheric chemistry are reactions of certain PAHs in VOC-NOx-air atmospheres to form biologically active polycyclic aromatic compounds, PACs. Thus, not only is the fundamental chemistry of the formation and fates of these secondary air pollutants of interest, but it can also have major toxicological implications. For example, in some airsheds certain PACs that are reaction products (e.g., nitro-PAH and nitro-PAH lactones) contribute signifi-... 

In short, a combined VOC-NOx reduction strategy seems to be the optimum approach to controlling ozone and other secondary air pollutants, and there is evidence from the experience in southern California that this approach is effective. For differing viewpoints, however, see articles by scientists from General Motors... 

Nazaroff, W.W. and Weschler, C.J. (2004) Cleaning products and air fresheners exposure to primary and secondary air pollutants. Atmospheric Environment, 38, 2841-65. 

Ammonia is sometimes used as a reducing agent for the selective reduction of NOE in emissions from industrial installations, but unreacted ammonia creates a secondary air pollution problem because it is itself hazardous. Consequently, selective catalytic oxidation (SCO) is required to convert traces of ammonia to nitrogen downstream of the reactor 134... 

In photochemical smog episodes, secondary air pollutants such as ozone, nitrogen dioxide, aldehydes, and peroxyacetyl nitrate are formed as a result of the chemical interaction of the primary air pollutants, principally nitric oxide and hydrocarbon vapors, with sunlight and air (Fig. 2.6) [49]. This interpretation of the processes involved has been verified by smog chamber experiments (Fig. 2.7), and has since been confirmed by field measurements as the sensitivity of ambient air instrumentation has improved [50, 51]. In photochemical smog episodes, it is the secondary pollutants that cause severe eye irritation and upper respiratory effects felt by people and at the same time causes serious damage to plants. 

With an increasing temperature the rate of H2S conversion In elemental sulfur, which is the most common reaction product, increased. The undesired side eflecl is an increase in the rate of SO2 production when temperature reached 445 K. This limits the application temperature due to secondary air pollution problems. An increase in the content of oxygen added to the gas stream significantly increases the conversion of H2S, as expected based on the mechanism of the reaction. With the oxy n content on the level of one time stoichiometric ratio the maximum conversion rate at 348 K is 80 % with a decrease to 40 % after 1000 minutes. When the content of oxygen is three times the stoichiometric ratio the initial conversion rate is almost 100 % and decreases to 86 % after 800 minutes. An increase in the flow rate and a decrease in the bed depth have also negative effect on the H2S conversion on activated carbon. With a three times increase in the flow rate the conversion rate can decrease even 40 % [67]. A similar effect is found when the bed depth decreases four times. The smallest alteration is observed with a decrease in pressure. When it decreases from 289 kPa to 104 kPa the initial conversion rate drops only 3 percent. 

National Academy of Sciences (1991) Human exposure assessment for airborne pollutants advances and opportunities. National Academy Press, Washington, DC Nazaroff W, Weschler C (2004) Cleaning products and air fresheners exposure to primary and secondary air pollutants. Atmos Environ 38 2841-2865 Oberdorster G, Sharp Z, Atudorei V et al (2004) Translocation of inhaled ultrafine particles to the brain. Inhala Toxicol 16 437 145... 

The definition of environmental chemistry shown in Figure 1.1 could very well be illustrated with nitrogen oxides, NO and NO2, emitted to the atmosphere. What would be the sources of these gaseous nitrogen oxides Which secondary air pollutant would they form interacting with volatile hydrocarbons in the sunlight Could acid rain result from these oxides and, if so, what would be the formula of the acid ... 

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. 

In what sense is acid rain a secondary air pollutant What is the chemistry behind the formation of most acid rain constituents Explain how particles in the atmosphere may be either primary or secondary air pollutants ... 

In what sense is nitrogen dioxide, NO2, a secondary air pollutant Explain. Why is NO2 especially harmful in the atmosphere ... 

Why are secondary air pollutants from hazardous waste sites usually of only limited concern as compared with primary air pollutants What is the distinction between the two ... 

Although acid rain can originate from the direct emission of strong acids, such as HCl gas or sulfuric acid mist, most of it is a secondary air pollutant produced by the atmospheric oxidation of acid-forming gases such as the following ... 

Hazardous-waste chemicals can enter the atmosphere by evaporation from hazardous-waste sites, by wind erosion, or by direct release. Hazardous-waste chemicals usually are not evolved in large enough quantities to produce secondary air pollutants. (Secondary air pollutants are formed by chemical processes in the atmosphere. Examples are sulfuric acid formed from emissions of sulfur oxides and oxidizing photochemical smog formed under sunny conditions from nitrogen oxides and hydrocarbons.) Therefore, species from hazardous-waste sources are usually of most concern in the atmosphere as primary pollutants emitted in localized areas at a... 

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