Nitrate cloud composition

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]. 

Sea aerosols initially have an ionic composition of sea water but quickly loose water to attain equilibrium with water vapour in the surrounding air, simultaneously cumulating reactive trace gases and undergoing chemical reactions (Pszenny et al., 1998). Also cloud droplets may imdergo dehydration, depending on air humidity. The concentration of nitrate may reach very high values, a mole per (hir and over, when droplets evaporate almost to dryness. 

The composition of cloud and precipitation water was investigated by Petrenchuk and Drozdova (1966), among others they developed a special cloud water collector that worked at positive as well as at negative temperatures. Their results, obtained over the European parts of the U.S.S.R., are given in Table 28. It can be seen that over clean northern regions the difference between the sum of ions in cloud and precipitation elements is not great. In these areas the concentration of sulfate and nitrate ions is relatively small while the chloride content is great. This situation can be explained by maritime influences. In comparison, sulfate is the... 

The idealized calculation just presented shows what are thought to be the essential elements of the aqueous-phase chemistry of acid rain. Measurements of H2O2 in rain and cloudwater show a range of concentrations between approximately 10 and 1(X) /itM (Kok, 1980 Zika et al., 1982). Water with this composition is in equilibrium with between 0.1 and 1.0 ppb gas-phase H2O2. Kleinman (1984) has examined the question of whether H2O2 can account for the in-cloud oxidation of SO2 and found that under summertime conditions between 3 and 5 ppb of H2O2 would be required to account for estimated incloud sulfate formation. Seigneur et al. (1984) presented the results of simulations of atmospheric sulfate and nitrate formation by both gas- and aqueous-phase paths under... 

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