Aerosol chemical speciation

Ng NL, Herndon SC, Trimbom A et al (2011) An Aerosol Chemical Speciation Monitor (ACSM) for routine monitoring of the composition and mass concentrations of ambient aerosol. Aerosol Sci Technol 45 780-794... 

Nico. R S. Werner, M. Anastasio, C. Marcus, M. A. Chemical Speciation of Chromium in Ambient Aerosol Particles. Proceedings of the 233rd American Chemical Society National Meeting, Chicago, IE, March 25-29, 2007. 

The availability of iron as a nutrient for phytoplankton growth is dependent on its chemical speciation (Wells et al., 1995). Thus processes which alter iron solubility in the atmospheric aerosols have the potential to influence bioavailability... 

The particular chemical form in which an element exists in water is its speciation. For example, an element can be present as a simple hydrated ion, as a molecule, as a complex with another ion or molecule, and so forth. From what was said previously, bare ions or bare polar molecules do not exist in water. At the least, they would be solvated species. Species of an element are distinguishable from one another stoichibmetrically, structurally, and energetically. In addition to aqueous species, one can distinguish elements in different phases, for example, as gaseous species, as solid phases, or in adsorbed states, and on the basis of particle sizes. In the atmosphere, for example, speciation extends over liquid, gas, and aerosol phases (Seinfeld, 1986). The notion of chemical speciation is central to equilibrium and kinetic aspects of aquatic chemistry, as will be evident throughout this book. 

Many chemical component-s present in such aerosols are relatively stable they can be measured long after (days, week.s, or more) the aero.sol has been collected on a filter or impactor plate, for example. Short-lived reactive and/or volatile species such as peroxides and aldehydes are not usually determined. This may make it difficult to evaluate the health and ecological effects of aerosols because chemically reactive chemical species tend to be the most active biochemically. The chemical components present in the particles collected on a filter or impactor plate may react with each other when they are in close proximity. Particle deposits in filters or on surfaces may also react with molecular components of the gases flowing over them. Chemical reactions between the gas and aerosol may not affect mea.surement.s of metallic elements but may modify chemical speciation (compound form) on the collector surface. All of these factors must be taken into account in selecting sampling and measurement methods for aerosol chemical properties. 

The relationship between air-lead and blood-lead in the occupational setting will also vary as a function of the particle-size distribution and chemical speciation of the lead contained within occupational aerosols [25]. The uptake of inhaled lead varies as a function of the area of the respiratory tract in which it deposits. Deposition patterns within the lung, in turn, will vary as a function of particle size. Very fine... 

Only a small fraction of the atmospheric flux of iron to the oceans ever becomes bioavailable, largely because of the low solubihty of the particulate and colloidal Fe(lll) phases that comprise the bulk of aerosol iron species. Nonetheless, bottle incubation experiments have shown that aerosol addition is an efficient stimulator of chlorophyll and biomass production in phytoplankton cultures [105,106], emphasizing the need to understand the factors and processes controlling the chemical speciation and solubihty of aerosol iron before and after deposition. 

Detailed study by use of optical and electron microscopy has shown that sulfate particles are often present in liquid or semi-liquid form. This feature has formed the basis for techniques by which the chemical "speciation" of atmospheric aerosol can be investigated (e.g. 18). It is now well accepted that acidic sulfate particles (which are typically composed of sulfuric acid or ammonium bisulfate) are hygroscopic and tend to leave impaction patterns indicative of a liquid shell, perhaps surrounding a solid core. 

The atmospheric pollution by cadmium is a result both of natural and man-made activities, such as the combustion processes based on fossil fuels (in particular coal and oil) and the emission from processes in the pyro-metallurigical non-ferrous metal industries. The deposition, transport, and inhalation processes are controlled predominantly by the size of the atmospheric aerosols, so that the primary type of speciation of interest to atmospheric chemists is the metal size distribution. However, chemical speciation (in terms of the distribution of both the dissolved/ particulate species and the inorganic/organic complexes) is important in governing... 

Addition of EGA to the analysis of atmospheric aerosol particles has permitted an independent speciation and determination of the nitrogenous component for samples which have not had chemical or physical pretreatment. The discovery from ESCA analyses that a substantial fraction of the particulate nitrogen exists chemically bound to the carbonaceous fraction has been confirmed by EGA. The indication from ESCA and EGA that inorganic sulfate... 

Similar to the situation in the reactor primary system (see Section 7.3.2.), interactions between iodine vapor and bulk material aerosols may occur in the containment atmosphere, although at a lower temperature level, and may have significant influence on iodine speciation and transport. Csl usually appears in the condensed form in the containment and is transported as aerosol particles. In rare cases, conditions may occur (e. g. in a BWR drywell) in which a significant fraction of the Csl present would exist in gaseous form, which can then migrate to cooler regions to condense on structural surfaces or on aerosols. However, in such a case normal condensation without additional chemical reactions is to be expected. 

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