Speciation atmospheric aerosol

Modified filter sampling methods that are available will measure ambient levels of strong acid in ambient aerosol samples, and these methods do so with acceptable precision and accuracy [as indicated by the balance between measured anions and cations (56, 57)] in the absence of significant levels of particulate weak acids. Additional intercomparisons involving intrinsically different techniques for particulate strong acidity [e.g., IR spectroscopy (48), thermal speciation (38, 45), and filter methods (28)] are needed. Further information on the occurrence of various weak acids in airborne particles is needed, along with further studies of techniques for their specific determination in atmospheric aerosol samples. 

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... 

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... 

Querol X, Zhuang X, Alastuey A, Viana M, Lv W, Wang Y, Lopez A, Zhu Z, Wei H, Xu S (2006) Speciation and sources of atmospheric aerosols in a highly industrialized emerging mega-city in Central China. J Environ Monit 8 1049-1059... 

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. 

Williams BJ, Goldstein AH, Kreisberg NM, Hering SV (2006) An in-situ instrument for speciated organic composition of atmospheric aerosols thermal desorption aerosol GC/MS-FID (TAG). Aerosol Sci Technol 40(8) 627-638. doi Doi 10.1080/02786820600754631... 

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... 

The organic fraction present in atmospheric particles is a highly complex mixture, which makes the speciation of individual compounds a difficult task. The traditional analytical approach has usually been solvent extraction of aerosol particles collected in a filter followed by gas chromatographic separation coupled to mass spectrometry (GC-MS) detection for individual compound identification and quantification. Although a large number of compounds, sometimes in trace amounts, have been... 

In addition to aerosol age, phosphorus aerosol speciation is also affected by the humidity of the ambient environment (Van Voris et al. 1987). Washout and rainout processes transport both the reaction products of vapor phase phosphorus and unreacted particles of phosphorus to water and land (Berkowitz et al. 1981). Because of its lower water solubility, physical state (gas), and slower reactivity, phosphine formed during the combustion of white phosphorus or released to the atmosphere from other media persists in the atmosphere longer than other reaction products. 

The atmospheric input of trace metals to the oceans has now been recognised to be of considerable importance to the marine system. Riverine sources have, for many years, been thought to be the dominant input route for metals into the oceans. Recent studies show, however, that these terrestrial fluxes may be equalled or even exceeded by inputs from the atmosphere. Thus, because of the importance of atmospheric input to the oceans, many of the examples considered here will focus on metal speciation in remote marine areas. In Table 7.1, average metal values in aerosols and rain at several sites are reported to show the range of concentrations of interest. 

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. 

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. 

In addition due to inadequate methods for in situ analysis at ambient concentrations analysis of airborne particles in their various forms has been limited. Even if the aerosols are analysed in detail changes have been found to occur in aerosol composition when collected by filters as they tend to react with the filter material itself. Therefore not only is improved identification of sulphate and nitrate speciation reaction mechanisms required but also improved techniques for in situ analysis to facilitate greater understanding of the quantitative aspects of the atmosphere which play a fundamental role in the long range transport of these pollutants. 

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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