Salt aerosol

Chlorides are often found as the salt aerosols of the atmosphere, and consequently may strongly influence the corrosion performance of structures and plant, particularly in marine or coastal situations. This influence on corrosivity reduces proportionately with distance from the seawater surface, though local environmental factors such as prevailing wind direction, level... 

Fig. 9.21 Waier trap in steel girder assembly of a bridge. Salt aerosol, bird excrement, etc., may also find their way into this stagnant water, producing an extremely corrosive fluid...

Chameides, W. L. and Stelson, A. W. (1992). Aqueous-phase chemical processes in deliquescent sea-salt aerosols a mechanism that couples the atmospheric cycles of S and sea salt. /. Geophys. Res. 97, 20565-20580. 

Sievering, H., Boatman, J., Gorman, E., Kim, Y., Anderson, L., Ennis, G., Luria, M., and Pandis, S. (1992). Removal of sulphur from the marine boundary layer by ozone oxidation in sea-salt aerosols. Nature, 360, 571-573. 

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]. 

Disselkamp, R.S., Chapman, E.G., Barchet, W.R., Colson, S.D., Howd, C.D. BrCl production in NaBr/NaCl/HNOs/Os solutions representative of sea-salt aerosols in the marine boundary layer, Geophys. Res. Lett., 26(13) 2183-2186, 1999. 

From British National Formulary 40, September 2000. Liquid, tablet and powder preparations contain salbutamol as the sulphate salt aerosols contain the free base. 

Dust particles, water droplets, and sulfuric acid mist (and if present, ammonium salt aerosols) are electrically charged in the same way as in the dry precipitator. The negatively charged particles are collected on the positive collecting electrodes. 

It is likely that there are as yet ill-defined aqueous-phase reactions in the airborne seawater droplets that release photochemically labile chlorine gases. For example, Oum et al. (1998a) have shown that Cl2 is formed when sea salt aerosols above their deliques-... 

Vogt, R., P. Crutzen, and R. Sander, A Mechanism for Halogen Release from Sea-Salt Aerosol in the Remote Marine Boundary Layer, Nature, 383, 327-330 (1996). 

Winkler, T., J. Goschnick, and H. J. Ache, Reactions of Nitrogen Oxides with NaCl as Model of Sea Salt Aerosol, J. Aerosol Sci., 22, S605-S608 (1991). 

Chameides, W. L., and A. W. Stelson, Aqueous Phase Chemical Processes in Deliquescent Sea-Salt Aerosols A Mechanism That Couples the Atmospheric Cycles of S and Sea Salt, J. Geophys. Res., 97, 20565-20580 (1992b). 

Sievering, H., J. Boatman, J. Galloway, W. Keene, Y. Kim, M. Luria, and J. Ray, Heterogeneous Sulfur Conversion in Sea-Salt Aerosol Particles The Role of Aerosol Water Content and Size Distribution, Atmos. Environ., 25A, 1479-1487 (1991). 

Marine 100-400 Three modes Dp 0.1, 0.1-0.6, and >0.6 p,m most (>95%) of particle mass but only 5-10% of total number in largest mode large particles mainly sea salt aerosol, smallest are products (e.g., SO ) of gas (e.g., DMS) to particle conversion... 

As might be expected, the salt concentration and to some extent the size distribution depend on the meteorology, especially wind speed, which drives the wave action. For a detailed discussion of sea salt aerosol, the reader is referred to Blanchard and Woodcock (1980), Blanchard (1985), Erickson et al. (1986), Fitzgerald (1991), Gong and Barrie (1997), Gong et al. (1997), and O Dowd et al. (1997). 

Similar reactions involving bromine and iodine in sea salt particles have also been suggested based on measurements of their concentrations in sea salt aerosols (Moyers and Duce, 1972a, 1972b Duce et al.,... 

O Dowd, C. D., and M. H. Smith, Physicochemical Properties of Aerosols over the Northeast Atlantic Evidence for Wind-Speed-Related Submicron Sea-Salt Aerosol Production, J. Geophys. Res., 98, 1137-1149 (1993b). 

Tang, I. N., H. R. Munkelwitz, and J. G. Davis, Aerosol Growth Studies. IV. Phase Transformation of Mixed Salt Aerosols in a Moist Atmosphere, . /. Aerosol Sci., 9, 505-511 (1978). 

Sievering, H., J. Boatman, E. Gorman, Y. Kim, L. Anderson, G. Ennis, M. Luria, and S. Pandis, Removal of Sulphur from the Marine Boundary Layer by Ozone Oxidation in Sea-Salt Aerosols, Nature, 360, 571-573 (1992). 

Vogt, R., Crutzen, P.J., and Sander, R. (1996) A mechanism for halogen release from sea-salt aerosol in the remote marine boundary layer. Nature 383, 327-330. 

The reason why SIA is higher in urban areas is less obvious as these are secondary aerosols. The observed increment is predominantly caused by more nitrate and sulphate. The reaction of nitric acid and sulphuric acid with the sea-salt aerosol in a marine urbanised environment follows an irreversible reaction scheme. In essence, the chloride depletion stabilises part of the nitrate and sulphate in the coarse mode and may partly explain part of the observed increment. However, it also raises the question how to assign the coarse mode nitrate in the mass closure. The sea salt and nitrate contributions cannot simply be added any more as nitrate replaces chloride. Reduction of NOx emissions may cause a reduction of coarse mode nitrate, which is partly compensated by the fact that chloride is not lost anymore. A reduction would yield a net result of ((N03-C1)/N03 = (62-35)/62=) 27/62 times the nitrate reduction (where the numbers are molar weights of the respective components), and this factor could be used to scale back the coarse nitrate fraction in the chemical mass balance. A similar reasoning may be valid for the anthropogenic sulphate in the coarse fraction. Corrections like these are uncommon in current mass closure studies, and consequences will have to be explored in more detail. 

Moldanova J, Ljungstrom E (2001) Sea-Salt Aerosol Chemistry in Coastal Areas A Model Study. J Geophys Res 106 1271... 

McDowell, W. H., C. Gines-Sanchez, C. E. Asbury, and C. R. Ramos-Perez. 1990. Influence of sea salt aerosols and long-range transport on precipitation chemistry at El Verde, Puerto Rico. Atmospheric Environment 24A 2813-2821. 

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