Ozone concentrations influences

The documentation of regional level terrestrial consequences of acid deposition is complicated. For example, forested ecosystems m eastern North America can he influenced by other factors such as high atmospheric ozone concentrations, drought, insect outbreaks and disease, sometimes from non-native sources. However there is a general consensus on some impacts of acidic depositon on both soils and forests m sensitive regions. 

Coupled closely with the effect causing horizontal distributions are the vertical distributions of ozone concentrations. These distributions have an intimate influence on the urban-rural interchange of ozone. Miller and Ahrens presented detailed vertical time and space cross sections of ozone concentrations at altitudes up to 2,500 m. A low-altitude temperature inversion may actually lead to lower concentrations of oxidant, because the destruction rate can be increased by the injection of nitric... 

A dramatic departure of ozone measurements from total oxidant measurements has b Mi reported for the Houston, Texas, area. Side-by-side measurements suggested that either method was a poor predictor of the other. Consideration was given to known interferences due to oxides of nitrogen, sulfur dioxide, or hydrogen sulfide, and the deviations still could not be accounted for. In the worst case, the ozone measurements exceeded the national ambient air quality standard for 3 h, and the potassium iodide instrument read less than 15 ppb for the 24-h period. Sulfur dioxide was measured at 0.01-0.04 ppm throughout the day. Even for a 1 1 molar influence of sulfur dioxide, this could not explain the low oxidant values. Regression analysis was carried out to support the conclusion that the ozone concentration is often much higher than the nonozone oxidant concentration. 

Riesenfeld and Bohnholtzer and Riesenfeld and Schumacher used ozone concentrated by liquefaction and distillation. From their kinetic measurements they conclude that a reaction of the second order and one of the first order take place simultaneously at quite low pressures, 6-60 mm. Hg the first order reaction predominates. The velocity constants of the second order reaction are not influenced by the total pressure, while those of the first order reaction appear to be inversely proportional to the total pressure. The figures given show that the first order reaction at the lower pressures is considerably influenced by the surface, and is quite probably a heterogeneous reaction, though the authors themselves do not consider this to be definitely shown. The decomposition appears to be rather sensitive to catalysts such as dust particles. 

However, the mass transfer rate can be influenced not only by physical properties, but by chemical reactions as well. Depending on the relative rates of reaction and mass transfer, a chemical reaction can change the ozone concentration gradient that develops in the laminar film, normally increasing the mass transfer coefficient, which in turn increases the mass transfer rate. 

In the following first example the liquid ozone concentration and the OH-radical concentration are calculated with semi-empirical formula from the mass balance for ozone (Laplanche et al., 1993). For ozonation in a bubble column, with or without hydrogen peroxide addition, they developed a computer program to predict the removal of micropollutants. The main influencing parameters, i. e. pH, TOC, U V absorbance at 254 nm (SAC254), inorganic carbon, alkalinity and concentration of the micropollutant M are taken into consideration. 

In this study we will present aspects of STE in relation with the budget and concentrations of ozone in the troposphere, specifically in the Northern Hemisphere. Firstly, we present ozone observations in the tropopause region from the measurement campaign MOZAIC, and discuss their correlation with potential vorticity. The results have been used to improve the parameterization of stratospheric ozone in a coupled tropospheric chemistry - general circulation model. We will show examples of the performance of the model regarding the simulation of ozone in the tropopause region, and present the simulated seasonality of cross-tropopause ozone transport in relation to other tropospheric ozone sources and sinks. Finally, we will examine and compare the influence of cross-tropopause transports to surface ozone concentrations for simulations with contemporary, pre-industrial, and future emission scenarios. 

The model tropopause is defined by a PV level of 3.5 pvu poleward of 20° latitude, and by a -2 K km 1 temperature lapse rate equatorward of 20° latitude. Consequently, in this study the troposphere is defined as the volume between the surface and the simulated tropopause. Because the model does not consider typical stratospheric chemical reactions explicitly, ozone concentrations are prescribed from 1-2 levels above the model tropopause up to the top of the model domain at 10 hPa. In both hemispheres we apply monthly and zonally averaged distributions from a 2D stratospheric chemistry model [31]. In the present version of the model, we use the simulated PV and the regression analysis of the MOZAIC data (Section 2) to prescribe ozone in the NH extratropical lower stratosphere, which improves the representation of ozone distributions influenced by synoptic scale disturbances [32, 33]. Furthermore, the present model contains updated reaction rates and photodissociation data [34]. 

Ozone forms in the upper stratosphere from molecular oxygen under the influence of UV solar radiation. In the lower stratosphere and troposphere, the source of ozone is the decomposition of nitrogen dioxide under the influence of UV and visible radiation. The formation of the vertical profile of ozone concentration is connected with its meridional and vertical transport. The general characteristic of this profile is the total amount of ozone measured by the thickness of its layer given in Dobson units (1 DU = 0.001 cm). 

Intaestingly, this results suggests that TCE conversion, x, was apparently influenced only by reaction time r, not by ozone concentration, which dif finm the bulk reaction directly influenced by ozone concentration [Hoigne et al, 1983 ]. This suggests that thoe will be conclusive factors that have a strongly effect on the apparent reaction behavior, indqiendent of the characteristics of the adsoibent nature. Thus, the effect of otho flictors such as particle size (binder... 

The initial pressure of the ozone mixture affects the detonation properties through the influence of pressure on the degree of dissociation of the product gases— in this case just oxygen. Therefore initial pressure values were chosen for calculations in Table I to correspond to conditions in the experiments. For low ozone concentrations,... 

Atmospheric pollution cannot be controlled so long as the nature and the mechanism of formation of its deleterious constituents remain unknown. While many chemical constituents of polluted atmospheres have been identified, their presence or concentration does not seem to follow a regular pattern. On the other hand, ozone is always present in polluted outdoor atmospheres. Its concentration consistently rises from a normal value of a few parts per hundred million to many times this value during periods of severe contamination. Whether ozone is the primary cause of pollution or is a secondary effect of the reaction of other substances is not entirely clear, but it appears to be an important link in the chain of chemical reactions which produce atmospheric pollution. Very likely, a knowledge of the variations of ozone concentration in atmospheres would permit a study of the influence of the various parameters, and this knowledge may eventually furnish a lead to an explanation of the mechanism of formation and the effects of pollutants. 

Carbon monoxide (CO) is also formed in aquatic environments from the photochemical degradation of DOM [3,4,8,22,94-105]. Strong gradients of CO have been observed in the lowest 10 metres of the atmosphere over the Atlantic Ocean [97]. The samples nearest the ocean surface were some 50 ppb higher than at the 10-metre altitude-sampling inlet. This implies that the ocean is a source of CO to the atmosphere and that this source can increase the atmospheric concentration. CO is reactive in the troposphere and thus its emissions from the ocean may influence the hydroxyl radical (OH) and ozone concentrations in the marine atmospheric boundary layer that is remote from strong continental influences. 

The polymer lifetime is also influenced indirectly by stratospheric ozone and its photochemistry. Terrestrial fluxes of the solar UV radiation are changing with the stratospheric ozone concentration. Stratospheric ozone depletion accounting for global ozone losses of 2.7 1.4% per decade may have increased to about... 

While ozone is not produced in the aqueous phase, at least 12 different chemical pathways consuming ozone have been identified. As a result of the relatively small aqueous-phase solubility of ozone, none of these reactions is rapid enough to significantly influence gas-phase ozone concentrations (Pandis and Seinfeld, 1989a). The fastest of these reactions is that with 02 ... 

It is known that measured ozone concentrations are lower than can be accounted for by the simple Chapman cycle. This has led scientists to look for other influences on the concentration of ozone. First, let s briefly consider one of the natural reactions that destroys ozone. UV radiation can break the oxygen-hydrogen bond of a water molecule in the stratosphere to generate hydrogen atoms and hydroxyl radicals ( OH). These two species are involved in many reactions, some of which actually convert Og to Og. However, this process, which scientists now believe is an efficient process above 50 km, has been occurring since the ozone layer developed, and there is little, if anything, that humans can do about it. The system has obviously attained a steady state that includes this perturbation. 

Ozone is formed in the troposphere from its preem ors by a complex series of chemical reactions which take place under the influence of solar hght. Smface ozone concentrations often reach maximal concentrations between 30 and 70 km downwind of large emission sources depend-... 

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