Aerosols composition influenced

The chemical composition of aerosols is influenced by other substances present in the air. An equilibrium is rapidly established between ionic components in the particles or droplets and the corresponding gaseous components, i.e., NH /NH, NO /HNO, Cl /HCl,... 

FIGURE 26.1 Measured aerosol composition of three elements in seven samples for a site influenced by automobiles (emitting Pb and Br) and a coal-fired power plant (emitting Al). 

The campaigns at the 4 sites were conducted consecutively, not simultaneously. Therefore, seasonal changes in aerosol composition will have influenced the results. Although the consecutive sampling pattern is not very suitable for a direct comparison of the localities, our study provides a detailed information on distribution of compounds producing multiple biological effects in the inhalable fraction of atmospheric particulate matter and the gas-phase. 

Bertram and Thornton recently introduced a method for performing direct aerosol flow tube uptake studies on ambient aerosol particles [148, 149]. They are able to correlate observed N2O5 reactive uptake coefficients with simultaneous measurements of aerosol composition using other techniques. When the flow tube technique of Bertram and Thornton is coupled with a technique capable of detecting the presence of surface-active organics in the aerosol, potential exists for the influence of these organics on N2O5 uptake by ambient aerosol to be inferred. 

CCN closure studies, where observations of ambient aerosol CCN activity are compared to the CCN concentration predicted via Kohler theory based on the particle size distribution and composition, often show discrepancies that can be attributed to kinetic limitations to droplet growth. Besides affecting cloud properties, kinetic limitations to droplet growth in the atmosphere may also impact the lifetime of aerosol particles. Changes in particle lifetime may influence the aerosol composition due to photochemical aging or heterogeneous processing of the aerosol. 

The evaporite source is characterized by covariation of sulfate (from gypsum) and chloride (from halite). That elements can be recycled from the ocean to land by movement of saltbearing aerosols (so-called "cyclic salts") has confused the interpretation of river flux data somewhat. While this cycling generally follows the ratio of salts in the sea, the S/Cl ratio is an exception. Taking the S/Cl ratio of the cyclic component to be 2 (based on compositional data for marine rains) and assuming that all chloride in rivers is cyclic, an upper limit for the cyclic influence can be calculated. 

The first purified and characterized drug substances were administered as aerosols as a topical treatment for asthma approximately 50 years ago. More recently, drugs have been evaluated for systemic delivery. For each category of drug the mechanism of clearance from the airways must be considered. These mechanisms may be listed as mucociliary transport, absorption, and cell-mediated translocation. The composition and residence time of the particle will influence the mechanism of clearance. 

When considering the impact of uptake by aerosol, the chemical composition of the aerosol is also likely to be significant. Bates et al. (1998, 2001) measured strong variations in the chemical composition of the Aitken, accommodation and sea-salt dominated coarse modes that would influence the free radical uptake rates, particularly the extent of aerosol acidification. Without data on the size segregated aerosol chemical composition during SOAPEX-2 and the relevant laboratory data, it is not possible to calculate accurate accommodation coefficients. 

Three components are similar to the results for the West Seattle-Maple Leaf PLS model except that the acid aerosol component no longer has high a loading from nitrate. This specie Is ordinarily associated with automobile emissions. The Tolt site Is remote enough that auto emissions are not as Important an Influence on Che variability In rainwater composition as In Seattle. The fourth component for this PLS model might represent emissions from a cement plant which does not Influence Che West Seattle site. The soil factor is apparently local In nature since It appears In the PCA results but not the PLS results. 

Although the measurement uncertainties limit the conclusions which can be drawn from these results, the data set proved useful for the determination of general Influences on rainwater composition In the Seattle area and for the demonstration of the application of these exploratory data analysis techniques. Current efforts to collect and analyze aerosol and rainwater samples over meteorologically appropriate time scales with precise analytical techniques are expected to provide better resolution of the factors controlling the composition of rainwater. 

Andrews GE, Abbass MK, Williams PT, et al. 1989. Factors influencing the composition of the organic fraction of diesel particulates. Journal of Aerosol Science 20(8) 1373-1376. 

Some degree of fractionation as function of distance from the power station smoke stack is to be expected coarse particles will fall out in the immediate vicinity of the power station, whereas fine fly ash will be transported further, and gaseous emissions might be expected to be transported the furthest. Thus, from the point of view of environmental health, not only the chemical composition of emitted particles and aerosols, but also their size, is relevant (Teinemaa et al. 2002). As particulate matter is dominated by basic oxides (e.g., CaO) and gaseous emissions by acidic gases (e.g., CO2, SO2), this fractionation will influence the pH of... 

The monitoring network in EMB compared to those established in Central and North Europe or even with the Western Mediterranean Basin (e.g. Spain) is rather insufficient. Particularly there is a lack of data on continuous or long-term monitoring of the chemical composition of particulate matter [12], For some substances (e.g. carbonaceous aerosol), the variability is expected to be much larger than can be resolved by integrating the available measurements and the research studies need to be supported by assessment of the local scale variability. In order to understand the temporal evolution (trends) there is also a particular need for aerosol measurements at additional sites with little influence from local and regional emission sources. 

The concentration of metals in atmospheric aerosols and rainwater (Table 7.1) is therefore a function of their sources. This includes both the occurrence of the metals in combustion processes and their volatility, as well as their occurrence in crustal dust and seawater. As a result of this, the size distribution of different metals is very different and depends on the balance of these sources. For a particular metal this distinction is similar in most global locations (Table 7.2), although some variability does occur as wind speed and distance from source exert an influence on the particle size distribution spectrum (Slinn, 1983). Once in the atmosphere particles can change size and composition to some extent by condensation of water vapour, by coagulation with other particles, by chemical reaction, or by activation (when supersaturated) to become cloud or fog droplets (Andreae et al., 1986 Arimoto et al., 1997 Seinfeld and Pandis, 1998). 

Hodge, V, Johnson, S.R. and Goldberg, E.D. (1978) Influence of atmospherically transported aerosols on surface ocean water composition. Geochem.f., 12, 7-20. 

Similarly, the relative humidity has a strong influence on the chemical composition of the secondary organic aerosol formed in the atmosphere by the reaction of ozone with 1-tetradecene <2000EST2116> thermal desorption particle beam mass spectrometric determinations found that the main products are a-hydroxytridecyl hydroperoxide and a peroxy-hemiaceta 1. 

The Pb-isotopic trend from top to bottom of the soil profiles indicates that compositions of US aerosols (industrial lead) overlap the leach fractions of the surface soil layers (0-10 cm) (Fig. 12.6). The data suggest that the profiles are influenced by Pb-isotopic contributions from the aerosols perhaps dominated by those in the period of 1997—1999, perhaps generally decreasing in a trend from the top layer to the bottom layer. The Fe-hydroxides also overlap in composition with... 

The composition of liquid-water clouds and processes responsible for this composition are of obvious current interest in conjunction with the so-called acid precipitation phenomenon since clouds constitute the immediate precursor of precipitation. Additionally, cloud composition is of interest because impaction of cloud droplets on surfaces may directly deliver dissolved substances onto natural or artificial materials. In-cloud processes also influence clear-air composition since dissolved substances resulting from such reactions are released into clear air as gases or aerosol particles upon cloud evaporation. It is thus desired to gain enhanced description of the composition of clouds and the mecha-... 

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