Nitrate 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... 

Okabayashi H. 1980. Differential movement of plutonium and americium in lungs of rats following the inhalation of submicron plutonium nitrate aerosol. J Radiat Res 21 111-117. 

The following problem, taken to match the conditions in Figure 2 of reference 13, is typical of those solved in less than one minute on an IBM PC with this model "a cloud at 278 K contains 0.5 grams of liquid water per cubic meter of air. The atmo here of the cloud contains 5 ppb sulfur dioxide, 340 ppm carbon dioxide, 0.29 jig/m of nitrogen base, 3 xg/m of sulfate aerosol, and no nitrate aerosol. What is the pH of the cloud water Figure 4 shows the Variable Sheet after solution. 

Hydrazine, monomethylhydrazine, and asymmetrical dimethylhydrazine have also been shown to react rapidly (k > 10 15 cm3 molecule- 1 s- ) with HN03 in the gas phase to form the corresponding hydrazinium nitrate aerosols (Tuazon et al., 1982). 

Wahner, A., T. F. Mentel, M. Sohn, and J. Stier, Heterogeneous Reaction of N205 on Sodium Nitrate Aerosol, . /. Geophys. Res., 103, 31103-31112 (1998b). 

Durham, J. L L. L. Spiller, and T. G. Ellestad, Nitric Acid-Nitrate Aerosol Measurements by a Diffusion Denuder A Performance Evaluation, Atmos. Environ., 21, 589-598 (1987). 

One procedure that is widely used to circumvent these complications is to remove ambient ammonia from the sampled air without removing particles by inserting one of several types of diffusion denuders upstream from the filter(s). In fact, in a recent Environmental Protection Agency (EPA)-sponsored intercomparison of methods for determination of strong acid content of aerosols, all but one protocol utilized an ammonia denuder (63), and all used an impactor or cyclone to remove coarse particles. The presence of this denuder clearly prevents neutralization of acidic aerosols by ammonia but also disturbs the gas-aerosol equilibrium between sulfate-nitrate aerosols and gaseous species. Ammonia and nitric acid are released from the depositing particles (64, 65) and must be collected downstream if accurate particulate ammonium and nitrate determinations are to be made. If equal amounts of ammonia and nitric acid are released, then the absolute [H+] (neq/m3) will not be altered. No specific evidence is available in the literature to demonstrate alteration of the observed [H+] as the result of reequilibration, but this area deserves further study. 

NOx emissions are implicated in phenomena such as acidification and eutrophication, with their subsequent impacts on the biodiversity of habitats, as well as radiative forcing of climate through the formation of nitrate aerosol and tropospheric ozone, and impacts on the carbon cycle [3]. 

Lunden MM, Revzan KL, Fischer ML, Thatcher TL, Littlejohn D, Hering SV, Brown NJ (2003) The transformation of outdoor ammonium nitrate aerosols in the indoor environment. Atmos Environ 37(39—40) 5633—5644... 

Production of sulfate and nitrate aerosols is also initiated by gas-phase reactions involving OH. Nitrate aerosols are produced from NOj through reaction (10), followed by the combination of HNO3 with atmospheric NH3 to produce... 

The amount of nitrate aerosol is controlled partly by the production of HNO3 (via Equations (11)-(13)) and partly by the availability of NH3 to form ammonium nitrate. Ammonium nitrate aerosol forms in equilibrium with gas-phase ammonia and nitric acid (Equation (14)) ... 

The availability of ammonia in the atmosphere is affected by the amount of other acid aerosols, such as sulfates, which also form compounds with ammonia. As a result, formation of nitrate aerosol can show complex dependence on emission rates of NH3 and SO2, as well as on NOj and VOCs (Pandis, 2003). 

Formation of ammonium nitrate aerosols also affects the global troposphere by transporting NO from polluted regions to remote locations (Horowitz et al., 1998). Gas-phase organic nitrates such as PAN, formed in polluted regions and exported to the remote troposphere, are often a significant source of in remote locations. Because ammonium nitrate is relatively long-lived (with a lifetime of days to weeks, similar to other fine particulates) it can also transport NO to the remote troposphere. 

The formation of ammonium sulfate and ammonium nitrate aerosols is an acid-base reaction in the atmosphere. Ammonia neutralizes the acids. Sulfuric acid has a very low vapor pressure (< 10 atm) and thus exists in the atmosphere as liquid particles, which react with NH3 and H2O (reaction 22). 

The behaviour of the oxides of nitrogen emitted from a source of pollution is much more complicated than for sulphur dioxide. The oxides of nitrogen are much more chemically reactive and form a whole family of oxidised nitrogen compounds. Each family member has a different fate and behaviour. Dry deposition and wet deposition occur downwind from the NO, source through the respective contributions from nitrogen dioxide, nitric acid and nitrate aerosol [17]. 

Sulfur dioxide (SO ) and nitrogen oxides (NO ) are oxidized to sulfate and nitrate aerosols either homogeneously rn the gas phase or heterogeneously in atmospheric microdroplets and hydrometeors Gas-phase production of nitric acid appears to be the dominant source of aerosol nitrate because the aqueous phase reactions of NO (aq) are slow at the nitrogen oxide partial pressures typically encountered in the atmosphere (5,i5). Conversely, field studies indicate that the relative importance of homogeneous and heterogeneous SO2 oxidation processes depends on a variety of climatological factors such as relative humidity and the intensity of solar radiation (4, -1 ). 

Kondo, Y., P. Aimedieu, M. Koike, Y. Iwasaka, P.A. Newman, U. Schmidt, W.A. Mathews, M. Hayashi, and W.R. Sheldon, Reactive nitrogen, ozone, and nitrate aerosols observed in the Arctic stratosphere in January 1990. J Geophys Res 97, 13,025, 1992. 

Harrison RM, Sturges WT, Kitto A-MN, et al. 1990. Kinetics of evaporation of ammonium chloride and ammonium nitrate aerosols. Atmos Environ 24(7) 1883-1888. 

Bassett, M. E., and Seinfeld, J. H. (1983) Atmospheric equilibrium model of sulfate and nitrate aerosols, Atmos. Environ. 17, 2237-2252. 

Dassios, K. G., and Pandis, S. N. (1999) The mass accommodation coefficient of ammonium nitrate aerosol, Atmos. Environ. 33, 2993-3003. 

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