Atmospheric Occurrence

NielsenT. 1984. Chapter 6 Atmospheric occurrence of organolead compounds. In Grandjean P, ed. Biological effects of organolead compounds. Boca Raton, FL CRC Press, 43-62. 

Since surfactants are ingredients of pesticide formulations, it appears likely that, after they are sprayed, aerosol-associated surfactant molecules occur in the atmosphere. However, to the best of our knowledge, no accounts of atmospheric occurrence of surfactants exist in the literature. 

Leuenberger C, Czuczwa J, Tremp J, et al. 1988. Nitrated phenols in rain Atmospheric occurrence of phytotoxic pollutants. Chemosphere 17 511-515. 

Acrolein is relatively unstable in the atmosphere therefore, transport within the atmosphere is expected to be limited. The relatively high vapor pressure of acrolein [220 mm Hg at 20 °C (Eisenreich et al. 1981 Hess et al. 1978)] suggests that this compound will not partition from the vapor phase to particulates in the atmosphere. Occurrence of acrolein in rainwater (Grosjean and Wright 1983 Nishikawa et al. 1987b) indicates that this compound may be removed from the atmosphere by washout. 

In this chapter, the sources, the atmospheric occurrence and behavior, the analyti-... 

The atmospheric occurrence of trace metals is determined by the source strength, the atmospheric dispersion, and the deposition processes. The source strength for the... 

T. E. Graedel, D. T. Hawkias, and L. D. CExton, Atmospheric Chemical Compounds Sources, Occurrence and Bioassay, Academic Press, New York, 1986. Atmospheric O ne 1985, World Meteorological Organization, Geneva, Switzerland (3 vols.) an excellent compendium on tropospheric and stratospheric processes. 

The process is carried at moderate (slightly above atmospheric) pressures, but at very high temperatures that reach a maximum of 1900°C. Even though the reaction time is short (0.6—0.8 s) the high temperature prevents the occurrence of any condensable hydrocarbons, phenols, and/or tar in the product gas. The absence of Hquid simplifies the subsequent gas clean-up steps. 

Irradiation of ethyleneimine (341,342) with light of short wavelength ia the gas phase has been carried out direcdy and with sensitization (343—349). Photolysis products found were hydrogen, nitrogen, ethylene, ammonium, saturated hydrocarbons (methane, ethane, propane, / -butane), and the dimer of the ethyleneimino radical. The nature and the amount of the reaction products is highly dependent on the conditions used. For example, the photoproducts identified ia a fast flow photoreactor iacluded hydrocyanic acid and acetonitrile (345), ia addition to those found ia a steady state system. The reaction of hydrogen radicals with ethyleneimine results ia the formation of hydrocyanic acid ia addition to methane (350). Important processes ia the photolysis of ethyleneimine are nitrene extmsion and homolysis of the N—H bond, as suggested and simulated by ab initio SCF calculations (351). The occurrence of ethyleneimine as an iatermediate ia the photolytic formation of hydrocyanic acid from acetylene and ammonia ia the atmosphere of the planet Jupiter has been postulated (352), but is disputed (353). 

Dimethyl sulfoxide occurs widely at levels of <3 ppm. It has been isolated from spearmint oil, com, barley, malt, alfalfa, beets, cabbage, cucumbers, oats, onion, Swiss chard, tomatoes, raspberries, beer, coffee, milk, and tea (5). It is a common constituent of natural waters, and it occurs in seawater in the 2one of light penetration where it may represent a product of algal metaboHsm (6). Its occurrence in rainwater may result from oxidation of atmospheric dimethyl sulfide, which occurs as part of the natural transfer of sulfur of biological origin (7,8). 

Indirect diyers are suited to diying under reduced pressures and inert atmospheres to permit the recoveiy of solvents and to prevent the occurrence of explosive mixtures or the oxidation of easily decomposed materials. 

It may he necessary to separate the live phases within the terminal box to eliminate any occurrence of a flashover or a shon-circuit and a subsequent explosion.. Such explosions may be very severe, depending upon the short-circtiii level of the system and the surrounding atmosphere and... 

Graedel, T. E., Hawkins, D. T., and Claxton, L. D., "Atmospheric Chemical Compounds Sources, Occurrence, and Bioassay," Academic Press, Orlando, FL, 1986,... 

Ozone has received increased attention for its occurrence and function in the Earth s atmosphere.For example the decreasing ozone concentration in the stratospheric ozone layer, becoming most obvious with the Antarctic ozone hole. 

Conversely, the high-pressure hexagonal phase is one of high entropy for which the reverse inequality is true. In lower -paraffins, the occurrence of the rotator phase at atmospheric pressure is due to the fact that the orthorhombic-hexagonal (or rotator) transition temperature, is lower than the temperature of fusion of... 

In the case of alloys having one constituent considerably more reactive to oxygen than the others, conditions of temperature, pressure and atmosphere may be selected in which the reactive element is preferentially oxidised. Price and Thomas used this technique to develop films of the oxides of beryllium, aluminium, etc. on silver-base alloys, and thereby to confer improved tarnish resistance on these alloys. If conditions are so selected that the inward diffusion of oxygen is faster than outward diffusion of the reactive element, the oxide will be formed as small dispersed particles beneath the surface of the alloy. The phenomenon is known as internal oxidation and is of quite common occurrence, usually in association with a continuous surface layer of oxides of the major constituents of the alloy. 

Continued exposure of the nickel-chromium alloy to more severely sulphurising and reducing atmospheres results in local depletion of chromium to such an extent that nickel sulphide and the eutectic are formed internally. The latter constituents are not often observed in service failures, but the relative instability of nickel sulphide in the presence of chromium sulphide can result in its reduction to nickel during slow cooling on shut down. That nickel sulphide is formed is suggested by the frequent occurrence of blisters, associated with the formation of molten eutectic on the surface of sulphur-attacked specimens . 

The gas chromatograph (GC) resembles the MS in providing both qualitative and quantitative EGA but is significantly slower in operation. The interval between analyses is normally controlled by the retention time of the last component to be eluted from the column such delay may permit the occurrence of secondary reactions between primary products [162]. Several systems and their applications have been described [144,163— 167] sample withdrawal can be achieved [164] without the necessity for performing the reaction in an atmosphere of carrier gas. By suitable choice of separation column or combination of columns [162], it is possible to resolve species which are difficult to measure in a small low-resolution MS, e.g. H20, NH3, CH4, N2 and CO. Wiedemann [168] has made a critical comparison of results obtained by MS and GC techniques and adjudged the quality of data as being about equal. 

The advent of fast computers and the availability of detailed data on the occurrence of certain chemical species have made it possible to construct meaningful cycle models with a much smaller and faster spatial and temporal resolution. These spatial and time scales correspond to those in weather forecast models, i.e. down to 100 km and 1 h. Transport processes (e.g., for CO2 and sulfur compounds) in the oceans and atmosphere can be explicitly described in such models. These are often referred to as "tracer transport models." This type of model will also be discussed briefly in this chapter. 

The deposition velocities depend on the size distribution of the particulate matter, on the frequency of occurrence and intensity of precipitation, the chemical composition of the particles, the wind speed, nature of the surface, etc. Typical values of and dj for particles below about 1 average residence time in the atmosphere for such particles is a few days. 

Since feedbacks may have a large potential for control of albedo and therefore temperature, it seems necessary to highlight them as targets for study and research. Besides the simple example above of cloud area or cloud extent, there are others that can be identified. High-altitude ice clouds, for example, (cirrus) have both an albedo effect and a greenhouse effect. Their occurrence is very sensitive to the amount of water vapor in the upper troposphere and to the thermal structure of the atmosphere. There may also be missing feedbacks. 

As a result of its use as an insecticide on fruit trees, vegetables, and other crops, endosulfan is released directly to the atmosphere during application. The compound is applied principally by air-blast equipment or boom sprayers (WHO 1984). No information was found in the available literature regarding atmospheric releases from manufacturing or formulation operations, or occurrence of the compound in air samples collected at NPL sites. 

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