Cocentration of nox and o3 in smoggy day pdf
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- 2. Tropospheric ozone: background information
- Evaluation of Ozone Smog Alerts on Actual Ozone Concentrations:A Case study in North Carolina
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In atmospheric chemistry , NO x is a generic term for the nitrogen oxides that are most relevant for air pollution , namely nitric oxide NO and nitrogen dioxide NO 2. NO x gases are usually produced from the reaction among nitrogen and oxygen during combustion of fuels, such as hydrocarbons , in air; especially at high temperatures, such as in car engines. NO x gases are also produced naturally by lightning. The term NO x is chemistry shorthand for molecules containing one nitrogen and one or more oxygen atom. It is generally meant to include nitrous oxide N 2 O ,  although nitrous oxide is a fairly inert oxide of nitrogen that has many uses as an oxidizer for rockets and car engines, an anesthetic , and a propellant for aerosol sprays and whipped cream. Nitrous oxide plays hardly any role in air pollution, although it may have a significant impact on the ozone layer ,  and is a significant greenhouse gas. Because of energy limitations, oxygen and nitrogen do not react at ambient temperatures.
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Ozone O 3 is produced in the troposphere as a result of a complex set of reactions that involve volatile organic compounds VOCs and oxides of nitrogen NO x. These reactions are discussed in detail in Chapter 5. Because the initial atmospheric concentrations and corresponding emissions of VOCs and NO x are not directly proportional to the maximum ozone concentration ultimately formed, a principal question associated with the VOC-NO x -O 3 system is ''What is the maximum amount of ozone that can form from a given initial mixture of VOCs and NO x?
Ground-level ozone is an important pollutant regulated under the Clean Air Acts that affects respiratory morbidity, decreases lung function, and negatively affects those with existing respiratory conditions like asthma. Moreover, this program encourages people to reduce air pollution by using voluntarily alternative transportation modes, such as carpooling and public transit, especially when a smog ozone alert is issued. Finally, the effects on ozone levels coming from the change in the warning threshold from 80 particles per billion ppb to 75 ppb, which took place in , are established. In addition, the air quality is improved when smog alerts are associated with the program. Finally, taken additionally into consideration the change of the threshold at 75 ppb the air quality is improved by 1.
2. Tropospheric ozone: background information
Ozone O 3 decomposition in the troposphere is a very important process which prevents excessive O 3 accumulation in the air. It is particularly significant on warm summer days which are marked by a high risk of photochemical smog. Nitrogen oxide concentrations were measured continuously by the chemiluminescence method, and O 3 concentrations were determined by the UV photometric method. The obtained results suggest that the rate of decomposition of tropospheric O 3 is affected mostly by the presence of NO x , high temperature, and air humidity positive correlation as well as by wind speed negative correlation. In the warm season, precipitation slowed down the rate of O 3 decomposition, mostly because NO x were scrubbed by rain.
This lists the logos of programs or partners of NG Education which have provided or contributed the content on this page. Powered by. Smog is air pollution that reduces visibility. The term "smog" was first used in the early s to describe a mix of smoke and fog. The smoke usually came from burning coal.
Not a MyNAP member yet? Register for a free account to start saving and receiving special member only perks. Second, ambient ratios often exceed by a substantial mount those calculated from emissions inventories. The goal of this chapter is to examine data gathered from atmospheric observations to determine if ambient VOC, NO x , and O 3 concentrations follow a regular pattern as one moves from an urban or suburban area to a rural area and then to a remote area. By comparing these patterns with those observed in smog-chamber experiments, it may be possible to establish to what degree smog-chamber experiments, and the chemical models based on these experiments can be applied to the atmospheric VOC-NO x -ozone system. By comparing patterns found in urban and suburban areas with those found in rural and remote locations, it may be possible to infer the relative effectiveness of controlling VOC versus NO x in different parts of the country.
Evaluation of Ozone Smog Alerts on Actual Ozone Concentrations:A Case study in North Carolina
Ground level ozone O 3 concentration was monitored during the period of December to November in an urban area in Greater Cairo Haram, Giza. During the winter and summer seasons, nitrogen dioxide NO 2 and nitric oxide NO concentrations and meteorological parameters were also measured. The mean values of O 3 were The diurnal cycles of O 3 concentrations during the four seasons revealed a uni-modal peak in the mid-day time, with highest O 3 levels in summer due to the local photochemical production. The diurnal variations in NO and NO 2 concentrations during the winter and summer showed two daily peaks linked to traffic density.
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