O 2 The Ozone example essay topic

The source of the tropospheric ozone The tropospheric ozone has two major sources. One is intrusion from the stratosphere. Most of ozone in the atmosphere is in the stratosphere and created from solar UV radiation. The stratospheric ozone sometimes flows into the troposphere by the upper layer trough and cut-off low activities. Some part of ozone may subside in the troposphere directly by the Hadley circulation or the Brewer Dobson circulation. Another source is production from photochemical reactions.

Ozone is produced from relatively longer-wavelength solar radiation under NOx and non-methane hydrocarbons rich environments. These photochemical reactions possibly bring about photochemical smog in urban area. web characteristics of the tropospheric ozone About 8% of the total column ozone is in the troposphere. The tropospheric ozone also plays an important role in the atmosphere. 1) Ozone is a green house gas and possibly contributes to the global warming. 2) Ozone is harmful for human being and crops in the troposphere. 3) Ozone oxidizes many chemical substances in the troposphere, and controls tropospheric chemistry.

The trend of the tropospheric ozone Some global monitoring stations show the increase of ozone in the troposphere. It may be a big problem, because if tropospheric ozone increases, it might damage to human beings and many crops, and fairly contribute to the global warming and change the tropospheric chemistry. If the tropospheric chemistry changes, the nature of pollution and acid rain might change. But not all monitoring stations show the increasing trend.

We have to monitor the tropospheric ozone at many suitable observation points. This also has the mean to study influence of human activities on Nature. Causes of ground-level ozone Other culprits-besides car and truck exhaust-are gas lawn mowers, over-filling and topping-off a gas tank, which allows vapors to escape, and leaking fuel, which react with sunlight and heat to produce ozone. Alternatives that reduce air pollution and ground-level ozone include using native plants for landscaping rather than a lawn, using an electric or push mower, limiting planting areas for lawns, carpooling and public transportation.

Effects on people with preemptive problems Ground-level ozone can cause flare-ups of asthma, chronic bronchitis, other lung diseases and cardio respiratory illnesses. Symptoms may take days to appear following exposure. Ground-level ozone can decrease lung function and cause chest tightness and coughing. In addition, ozone and microscopic particulates, small enough to be inhaled into the lungs and 'sticky' enough to attract pollens and other allergens, can contribute to asthma and allergy attacks, and make other lung diseases more severe. Things that can be done to lower the risk? When ground-level ozone levels are high -- in the 101-150 air quality index (AQI) range and above -- children and people with respiratory diseases are at risk.

Stay indoors if you " re able. If not, don't exert yourself when outdoors; walk don't run. If you exercise, do so in the morning or evening, when ground-level ozone numbers tend to drop. Be aware of high pollution days, check the Environmental Protection Agency and your local health department's Web sites for air pollution levels, avoid congested areas where pollution accumulates, use public transportation and carpool. The troposphere equation Ozone is produced photo chemically via a different mechanism: the photolysis of nitrogen dioxide, as follows: hf a NO 2 NO + O (5) f"U 400 no + O 2 + M O 3 + M, where M = N 2, O 2 (6) The ozone formed in this way can be removed by nitric oxide, NO: NO + O 3 = NO 2 + O 2 (7) Thus a photochemical equilibrium exists and the ozone equilibrium concentration can be calculated by a certain chemical equation. This equilibrium is disturbed by the oxidation of NO to NO 2 by proxy radicals (HO 2) formed in the course of oxidation of carbon monoxide (CO) and hydrocarbons by OH radicals: For CO: CO + OH CO 2 + H H + O 2 HO 2 HO 2 + NO OH + NO 2 For hydrocarbons (e. g., CH 4): CH 4 + OH CH 3 + H 2 OCH 3 + O 2 CH 3 O 2 CH 3 O 2 + NO CH 3 O + NO 2 CH 3 O + O 2 CH 2 O + HO 2 HO 2 + NO OH + NO 2 The net result of this chemistry is to produce NO 2 from NO by other means than by reaction (7), thus leading to enhanced ozone concentrations following reactions (5) and (6).

Tropospheric ozone accounts for about 10% of the total ozone. Ozone affects human health (exposure to ozone can cause mucosa l irritation, headache, reduced physical performance, reduction in resistance to infections and respiratory diseases particularly if the concentration is higher than 100 ppb). It is and causes damage to materials (e. g., it accelerates rubber cracking, fading of textile dye, loss of tensile strength in fabrics and the deterioration of works of art). In addition, tropospheric (including surface) ozone is a main oxidant in photochemical smog, a good indicator for air pollution. Thus, with all these effects, tropospheric ozone is bad. Tropospheric ozone as a GHG Tropospheric ozone is also a greenhouse gas (GHG) as it absorbs upward directed terrestrial radiation.

It plays a key role in atmospheric chemistry. As a strong oxidant, it affects the lifetimes and hence the concentrations of most atmospheric trace gases, including CH 4 and the replacements of the CFCs such as hydro chlorofluorocarbons (H CFCs) and hydro fluorocarbons (HFCs), which, in turn, are greenhouse gases that have implications for global climate. The relatively short lifetime of ozone has made it both a regional climate forcing mechanism and a relatively highly variable greenhouse gas, hence the need for frequent regional measurements of vertical profiles. One of the major 'remaining uncertainties regarding the causes, effects, magnitude and timing of climate change' is the contribution of tropospheric ozone as a greenhouse gas, as the global distribution of tropospheric ozone is still poorly known, especially in the tropics and subtropics where data are sparse.

Thus, any research effort to reduce this major scientific uncertainty would be a useful contribution to our understanding of our climate system.