Ammonium aerosols

Walker, J. T., WhitaU, D. R., Robarge, W., and Paerl, H. W. (2004). Ambient ammonia and ammonium aerosol across a region of variable ammonia emission density. Atmos. Environ. 38, 1235—1246. 

These ammonium aerosols (d = 0.3-1 ini) occur at low humidity as solid particles. The reactions given above can be compared with precipitation reac-... 

In the atmosphere, ammonia can react with acidic substances in the air to produce ammonium aerosols, which can undergo dry or wet deposition. The best estimate of the half-life of atmospheric ammonia is a few days. In water, ammonia can volatilize to the atmosphere, be removed by microbial processes, or adsorb to sediment and suspended organic material. In soil, ammonia can volatilize to the atmosphere, adsorb to soil, undergo microbial transformation to nitrate or nitrite anions, or be taken up by plants. 

Crutzen 1983 Dawson 1977 Galbally and Roy 1983 Moller and Schieferdecker 1985). The reaction of atmospheric ammonia with acidic substances in the air results in the formation of ammonium aerosols that can subsequently be removed from the atmosphere by dry or wet deposition. In general, dry deposition processes predominate where there are high amounts of NH3 emissions where NH3 emissions are lower, wet deposition of particulate NH/ predominates (Asman et al. 1998). 

Ammonia plays an important role in the acid-base chemistry in the troposphere where the unionized ammonia (NH3) is converted into ionized ammonia (NH4) via a reaction that neutralizes atmospheric acids as HNO3 and H2SO4. This leads to the formation of ammonium aerosols such as the stable ammonium sulfate. Eventually the ammonia returns to the surface by dry or wet deposition. 

Climate Change Sulfate, nitrate and ammonium aerosols may offset global warming in the shortterm, but nitrous oxide is a potent greenhouse gas Moore et al. 1997 Dillon et al. this volume... 

Schlenker, J. and Martin, S. (2005). Crystallization pathways of sulfate-nilrate-ammonium aerosol particles, J. Phys. Chem. A, 199, pp. 9980-9985. 

VA/crotonates/vinyl neodecanoate copolymer is the most used polymer in aerosol hair sprays (ca 1993). Like its precursor above, it has free carboxyhc acid groups which can be neutralized to give various film properties. Recommended neutralizing agents include aminomethyl propanol, ammonium hydroxide, and dimethyl stearamine. Recommended percent neutralization is 90%, but products can be found in the 80—110% range. 

A small but important use of ammonium nitrate is in the production of nitrous oxide during the 1980s consumption for this purpose averaged about 30,000 t. The gas is generated by controlled heating of ammonium nitrate above 200°C. Nitrous oxide is used primarily as an anesthetic and as an aerosol propellant for food products (see Anesthetics Aerosols). 

FIG. 17-47 Performance curve for orifice scrubber collecting ammonium flii-orescin aerosol, Semrau et at, EFA 600/2-77-237, 1977.)... 

ITie major component of atmospheric haze is sulfate particulate matter (particularly ammonium sulfate), along with varying amounts of nitrate particulate matter, which in some areas can equal the sulfate. Other components include graphitic material, fine fly ash, and organic aerosols. 

A portion of nitrogen dioxide in the atmosphere is converted to nitric acid (HNO3) and ammonium salts. Nitrate aerosol (acid aerosol) is removed from the atmosphere... 

On molybdenum sulfate roasting, downstream of a scrubber, to remove ammonium sulfite and sulfate aerosols which form in the ammonia scrubbing stage, and SO2,... 

Nitrates those gases and aerosols that have origins in the gas-to-aerosol conversion of nitrogen oxides, e.g., NOj of primary interest are nitric acid and ammonium nitrate. Ammonium nitrate is very hygroscopic so its contribution to visibility impairment is magnified in the presence of water vapor. 

Sulfuric acid (H1SO4) and ammonium bisulfate (NH4HSO4) contribute importantly to ambient acid aerosols, particularly in geographic locations where sulfur-rich coal is used for power plant fuel, such as the eastern United States.Studies on animals and human subjects have shown that H2SO4 and NH4HSO4 alter mucociliary transport in a dose-dependent fashion and... 

All of these species are very soluble in a rain or cloud drop and are an important source of atmospheric aerosols. For ammonia and ammonium, the condensed phases (I and s) represent approximately two-thirds of the total atmospheric burden, whereas for nitric acid and nitrates, about two-thirds is in the gas phase (Soderlund and Svensson, 1976). 

Atmospheric aerosols have a direct impact on earth s radiation balance, fog formation and cloud physics, and visibility degradation as well as human health effect[l]. Both natural and anthropogenic sources contribute to the formation of ambient aerosol, which are composed mostly of sulfates, nitrates and ammoniums in either pure or mixed forms[2]. These inorganic salt aerosols are hygroscopic by nature and exhibit the properties of deliquescence and efflorescence in humid air. That is, relative humidity(RH) history and chemical composition determine whether atmospheric aerosols are liquid or solid. Aerosol physical state affects climate and environmental phenomena such as radiative transfer, visibility, and heterogeneous chemistry. Here we present a mathematical model that considers the relative humidity history and chemical composition dependence of deliquescence and efflorescence for describing the dynamic and transport behavior of ambient aerosols[3]. 

Surfactants employed for w/o-ME formation, listed in Table 1, are more lipophilic than those employed in aqueous systems, e.g., for micelles or oil-in-water emulsions, having a hydrophilic-lipophilic balance (HLB) value of around 8-11 [4-40]. The most commonly employed surfactant for w/o-ME formation is Aerosol-OT, or AOT [sodium bis(2-ethylhexyl) sulfosuccinate], containing an anionic sulfonate headgroup and two hydrocarbon tails. Common cationic surfactants, such as cetyl trimethyl ammonium bromide (CTAB) and trioctylmethyl ammonium bromide (TOMAC), have also fulfilled this purpose however, cosurfactants (e.g., fatty alcohols, such as 1-butanol or 1-octanol) must be added for a monophasic w/o-ME (Winsor IV) system to occur. Nonionic and mixed ionic-nonionic surfactant systems have received a great deal of attention recently because they are more biocompatible and they promote less inactivation of biomolecules compared to ionic surfactants. Surfactants with two or more hydrophobic tail groups of different lengths frequently form w/o-MEs more readily than one-tailed surfactants without the requirement of cosurfactant, perhaps because of their wedge-shaped molecular structure [17,41]. 

Eberlein and Kattner [194] described an automated method for the determination of orthophosphate and total dissolved phosphorus in the marine environment. Separate aliquots of filtered seawater samples were used for the determination orthophosphate and total dissolved phosphorus in the concentration range 0.01-5 xg/l phosphorus. The digestion mixture for total dissolved phosphorus consisted of sodium hydroxide (1.5 g), potassium peroxidisulfate (5 g) and boric acid (3 g) dissolved in doubly distilled water (100 ml). Seawater samples (50 ml) were mixed with the digestion reagent, heated under pressure at 115-120 °C for 2 h, cooled, and stored before determination in the autoanalyser system. For total phosphorus, extra ascorbic acid was added to the aerosol water of the autoanalyser manifold before the reagents used for the molybdenum blue reaction were added. For measurement of orthophosphate, a phosphate working reagent composed of sulfuric acid, ammonium molyb-... 

Apart from NO, ammonia also occurs in the atmosphere which is largely formed by the natural ecosystem. In industrial regions it can undergo a series of reactions to produce ammonium sulphate aerosol in presence of sulphuric acid, or alternatively form NH2, N2O and NO. These species are responsible for the destruction of ozone in the troposphere9. 

FIGURE 3-5 Hourly variatioiis of secondary aerosol organics, nitrates, sulfates, and ammonium as percent of total aerosol. Pasadena, Califixnia, July 25, 1973. Reprinted with permis from Grosjean and Friedlandn. ... 

Chemical radicals—such as hydroxyl, peroxyhydroxyl, and various alkyl and aryl species—have either been observed in laboratory studies or have been postulated as photochemical reaction intermediates. Atmospheric photochemical reactions also result in the formation of finely divided suspended particles (secondary aerosols), which create atmospheric haze. Their chemical content is enriched with sulfates (from sulfur dioxide), nitrates (from nitrogen dioxide, nitric oxide, and peroxyacylnitrates), ammonium (from ammonia), chloride (from sea salt), water, and oxygenated, sulfiirated, and nitrated organic compounds (from chemical combination of ozone and oxygen with hydrocarbon, sulfur oxide, and nitrogen oxide fragments). ... 

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