Nitric oxide smog pollutant

Reduction of metal oxides with hydrogen is of interest in the metals refining industry (94,95) (see Metallurgy). Hydrogen is also used to reduce sulfites to sulfides in one step in the removal of SO2 pollutants (see Airpollution) (96). Hydrogen reacts directiy with SO2 under catalytic conditions to produce elemental sulfur and H2S (97—98). Under certain conditions, hydrogen reacts with nitric oxide, an atmospheric poUutant and contributor to photochemical smog, to produce N2 ... 

Nitric acid synthesis, platinum-group metal catalysts in, 19 621 Nitric acid wet spinning process, 11 189 Nitric oxide (NO), 13 791-792. See also Nitrogen oxides (NOJ affinity for ruthenium, 19 638—639 air pollutant, 1 789, 796 cardioprotection role, 5 188 catalyst poison, 5 257t chemistry of, 13 443—444 control of, 26 691—692 effect on ozone depletion, 17 785 mechanism of action in muscle cells, 5 109, 112-113 oxidation of, 17 181 in photochemical smog, 1 789, 790 reduction with catalytic aerogels, l 763t, 764... 

Nitric oxide (NO) A gas formed by combustion under high temperature and high pressure in an internal combustion engine it is converted by sunlight and photochemical processes in ambient air to nitrogen oxide. NO is a precursor of ground-level ozone pollution, or smog. 

Until the mid 1980 s the simple chemical species nitric oxide, NO, was generally associated with the numerous nitrogen oxides found in photochemical smog and other forms of urban pollution but was suddenly identified as an essential biological... 

Nitrogen oxides (NOx) such as nitric oxide (NO), nitrous oxide (N2O), and nitrogen dioxide (NO2) make one of fhe most common groups of air pollufanfs. They are released mainly from internal combustion engines and furnaces and are considered fo be harmful atmospheric pollutants, as they can cause acid rain, photochemical smog, and greenhouse effects (Zhou et ah, 2007). 

We can observe this process by analyzing polluted air at various times during a day (see Fig. 5.28). As people drive to work between 6 and 8 a.m., the amounts of NO, N02, and unburned molecules from petroleum increase. Later, as the decomposition of N02 occurs, the concentration of ozone and other pollutants builds up. Current efforts to combat the formation of photochemical smog are focused on cutting down the amounts of molecules from unburned fuel in automobile exhaust and designing engines that produce less nitric oxide (see Fig. 5.29). 

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. 

One of the key culprits in the formation of photochemical smog is NO (nitric oxide), a colorless but reactive gas. Its nominal concentration in our atmosphere is quite low, and there are natural sources of nitric oxide about which we can do little. It is the anthropogenic nitric oxide about which we are most concerned, as it is a pollutant over which we may have some control. Where does this nitric oxide come from You are probably aware that an... 

The nitric oxide gas formed in this way is an important species in several pollution pathways and is itself an irritant molecule. For example, NO(g) reacts further with oxygen to form nitrogen dioxide, whose brown color is largely responsible for the dark haze typical of urban smog. Example Problem 9.10 shows how this type of equation can be used to determine heats of reaction of specific quantities of substances. 

In summary, then, the primary pollutants from the internal combustion engine of an automobile are carbon monoxide, lower hydrocarbons, and nitric oxide. These are dangerous, toxic materials in themselves but are just the beginning of the story. The action of sunlight on the primary pollutants is what really still makes photochemical smog one of the most difficult problems facing humankind as we begin the twenty-first century. 

Nitrogen oxide is a serious air pollutant because it is oxidized to nitrogen dioxide, NO2, which reacts with water to form nitric acid and with other products of the incomplete combustion of hydrocarbons to form nitrates. The latter are eye irritants in photochemical smog. 

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