Parameters Affecting Dispersion

A wide variety of parameters affect atmospheric dispersion of toxic materials  

Puff Moves Downwind and Dissipates by Mixing with Fresh Air 

As release height increases, this distance increases. The increased distance leads to greater dispersion and a lower concentration at ground level. 

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First order parameters affecting dispersion stem from meteorological conditions. These, as much as any other consideration, determine how a stack is to be designed for air pollution control purposes. Since the operant transport mechanisms are determined by the micro-meteorological conditions, any attempt to predict ground-level pollutant concentrations is dependent on a reasonable estimate of the convective and dispersive potential of the local air. The following are meteorological conditions which need to be determined ... 

The injected sample volume is by far the most important parameter affecting dispersion in flow injection analysis, as it has a pronounced influence on the height, width and area of the recorded peak (Fig. 5.11). 

Emulsions Almost eveiy shear rate parameter affects liquid-liquid emulsion formation. Some of the efrecds are dependent upon whether the emulsion is both dispersing and coalescing in the tank, or whether there are sufficient stabilizers present to maintain the smallest droplet size produced for long periods of time. Blend time and the standard deviation of circulation times affect the length of time it takes for a particle to be exposed to the various levels of shear work and thus the time it takes to achieve the ultimate small paiTicle size desired. 

Parameters Affeeting Gas Dispersion A wide variety of parameters affect the dispersion of gases. These include (1) wind speed, (2) atmospheric stability, (3) local terrain characteristics, (4) height of the release above the ground, (5) release geometry, i.e. from a point, line, or area source, ( momentum of the material released, and (7) buoyancy of the material released. 

Parameters Affecting Atmospheric Dispersion The parameters important to atmospheric dispersion can be divided roughly into three categories contaminant source atmospheric and terrain properties and contaminant interaction with the atmosphere. 

Parameters Affecting the Performance and Storage Stability of DDT 75% Water-Dispersible Powder... 

In bubble columns, since the gas bubbles are dispersed in the continuous liquid phase, fractional gas holdup (Eg) is an important design parameter, affecting column performance. The most direct and obvious effect is on the column volume, since a significant fraction of the volume is occupied by the gas. The indirect influences are also important. For instance, the possible spatial variation of Eg gives rise to pressure variation, which results in intense liquid phase motion. These secondary motions govern the rates of mixing plus heat and mass transfer. 

Another parameter affecting sample dispersion in flow injection analysis is the way that the sample is inserted. The influence of Vs on the shape of the recorded signal is, however, relatively independent of the mode of sample insertion, and this is perhaps the main reason why this aspect is rarely reported. 

Most flow injection analysers exploit either loop-based or time-based injections (see 6.2.2), and the main difference between these injection modes is the shape of the initial sample plug. A critical comparison of these strategies is given elsewhere [85]. This aspect is of minor concern as a parameter affecting sample dispersion in flow injection analysis. 

Better system ruggedness and analytical sensitivity are attained in flow injection systems designed in the confluence configuration. Reagent addition by confluence is therefore an important parameter affecting sample dispersion. 

The origin of the critical point can be traced to the temperature effect on miscibility. Patterson [1982] observed that there are three principal contributions to the binary interaction parameter, the dispersive, free volume and specific interactions. As schematically illustrated in Figure 2.16, the temperature affects them differently. Thus, for low molecular weight systems where the dispersion and free volume interactions dominate, the sum of these two has a U-shape, intersecting the critical value of the binary interaction parameter in two places — hence two critical points, UCST and LCST. By contrast, most polymer blends derive their miscibility from the presence of specific interactions, characterized by a large negative value of the interaction parameter that increases with T. The system is also affected by the free volume contribution, as well as relatively unimportant in this case dispersion forces. The sum of the interactions reaches the critical value only at one temperature — LCST. 

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