Nitrogen atmospheric residence time

Jacobi and Andre (113) found a longer time of 20 to 50 days, which is consistent with the lifetime calculated by Bates and Hays (11) for odd nitrogen. However, Francis, Chester and Haskin (66) found that dust containing fission products had been aged and that analysis of filtered rainwater gave a much shorter lifetime of approximately 10 days. Recently Poet, Moore, and Martell (195) estimated a mean atmospheric residence time of about four days for particles in the lower troposphere and about one week for particles in precipitation. 

The oxidized inorganic nitrogen species not included in NO is N2O. It is produced during nitrihcation and denitrification (Figure I). It has an atmospheric residence time of 100 yr and, because of this, emissions are globally distributed. Because of its stability, no significant chemical reactions take place in the troposphere but, once in the stratosphere, it is converted to NO by UV radiation ... 

Table 12-8. Global Fluxes and Atmospheric Residence Times of Nitrogen Associated with Biological Nitrogen Fixation, Inorganic Atmospheric Oxidation, Agricultural Fertilizer Production, Combustion Process, and the Sedimentary Cycle...

The atmospheric residence times of many synthetic organic compounds are relatively long compared with those of the metals and nitrogen species, as mentioned previously. Many of these substances are found primarily in the gas phase in the atmosphere, and they are thus very effectively mobilized into the atmosphere during their production and use. Their long atmospheric residence times of weeks to months leads to atmospheric transport that can often be hemispheric or near hemispheric in scale. Thus... 

The majority of thermal polymerizations are carried out as a batch process, which requires a heat-up and a cool down stage. Typical conditions are 250—300°C for 0.5—4 h in an oxygen-free atmosphere (typically nitrogen) at approximately 1.4 MPa (200 psi). A continuous thermal polymerization has been reported which utilizes a tubular flow reactor having three temperature zones and recycle capabiHty (62). The advantages of this process are reduced residence time, increased production, and improved molecular weight control. Molecular weight may be controlled with temperature, residence time, feed composition, and polymerizate recycle. 

The influence of the reactor temperature on the conversion of methane was examined during pulsed operation. The heat performance of the foil heater was slowly increased while the reactor was continuously supplied with gas pulses consisting of pure oxygen at 129.5 ml min-1 together with a flow of methane (0.5 ml min-1). The volume flow of the carrier gas nitrogen was adjusted to 130 ml min-1 at atmospheric pressure, delivering a residence time in the coated spiral of 0.4 s. The cat-... 

In the development of these processes and their transference into an industrial-scale, dimensional analysis and scale-up based on it play only a subordinate role. This is reasonable, because one is often forced to perform experiments in a demonstration plant which copes in its scope with a small produdion plant ( mock-up plant, ca. 1/10-th of the industrial scale). Experiments in such plants are costly and often time-consuming, but they are often indispensable for the lay-out of a technical plant. This is because the experiments performed in them deliver a valuable information about the scale-dependent hydrodynamic behavior (arculation of liquids and of dispersed solids, residence time distributions). As model substances hydrocarbons as the liquid phase and nitrogen or air as the gas phase are used. The operation conditions are ambient temperature and atmospheric pressure ( cold-flow model ). As a rule, the experiments are evaluated according to dimensional analysis. 

Nitrogen Oxide. The photochemical smog reaction involves nitrogen oxides, hydrocarbons, and sunlight. The global importance of this pollutant system depends upon the amounts of materials emitted to the atmosphere, their residence time in the atmosphere, and their reaction products. 

The atmosphere is an important conveyor belt for many pollutants. The atmosphere reacts most sensitively to anthropogenic disturbance because proportionally it represents a much smaller reservoir than land and water furthermore, the residence times of many constituents of the atmosphere are smaller than those that occur in the other exchange reservoirs. Water and atmosphere are interdependent systems. Many pollutants, especially precursors of acids and photooxidants, originate directiy or indirecdy from the combustion of fossil fuels. Hydrocarbons, carbon monoxide, and nitrogen oxides released by thermal power plants and, above all by automobile engines, can produce, under the influence of sunlight, ozone and other photooxidants. 

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