Aerosol particles trace elements

Bernstein, D. M. and K. A. Rahn. New York Summer Aerosol Study Trace Element Concentrations as a Function of Particle Size. Ann. N.Y. Acad. Sci. 322 87-97 (1980). 

Interest in the elemental composition of aerosol particles arises from concerns about health effects and the value of these elements to trace the sources of suspended particles. The following physical analysis methods have been applied for the elemental measurements of aerosol samples. A schematic drawing of an x-ray fluorescence system is presented in Fig. 13.42. 

Trace elements are delivered to the ocean by atmospheric, or aeolian, processes in both particulate and soluble forms. Most of the aeolian particles entering the ocean are less than 10 pm in size and are referred to as aerosols. Aeolian transport of particles occurs when winds, such as the Trades, pick up small particles from the land s surface and carry them over the ocean. Some trace elements, such as mercury, have a high enough vapor pressure that they are present as atmospheric gases. Still others are ejected during volcanic eruptions in either particulate or gaseous form. 

Cluster analysis Is used to determine the particle types that occur in an aerosol. These types are used to classify the particles in samples collected from various locations and sampling periods. The results of the sample classifications, together with meteorological data and bulk analytical data from methods such as instrunental neutron activation analysis (INAA). are used to study emission patterns and to screen samples for further study. The classification results are used in factor analysis to characterize spatial and temporal structure and to aid in source attribution. The classification results are also used in mass balance comparisons between ASEM and bulk chemical analyses. Such comparisons allow the combined use of the detailed characterizations of the individual-particle analyses and the trace-element capability of bulk analytical methods. 

Quinn, T. L., and J. M. Ondov, Influence of Temporal Changes in Relative Humidity on Diy Deposition Velocities and Fluxes of Aerosol Particles Bearing Trace Elements, Atmos. Environ., 32, 3467-3479 (1998). 

In a number of studies, the elemental composition of aerosol particles has been related to their source. Schroeder and co-workers (1987) review the sources, sinks, analysis, deposition, chemical forms, and global cycles of various trace elements. Because the relative amounts of trace elements vary for coal compared to oil-fueled power plants, for example, it has been suggested that certain elements or ratios of elements may serve as tracers for various sources (e.g., see Gordon, 1988 and Rahn and Lowenthal, 1984). Thus V and Ni are indicative of oil combustion, and elevated concentrations of elements such as As and Se are usually... 

Trace element compositions of airborne particles are important for determining sources and behavior of regional aerosol, as emissions from major sources are characterized by their elemental composition patterns. We have investigated airborne trace elements in a complex regional environment through application of receptor models. A subset (200) of fine fraction samples collected by Shaw and Paur (1,2) in the Ohio River Valley (ORV) and analyzed by x-ray fluorescence (XRF) were re-analyzed by instrumental neutron activation analysis (INAA). The combined data set, XRF plus INAA, was subjected to receptor-model interpretations, including chemical mass balances (CMBs) and factor analysis (FA). Back trajectories of air masses were calculated for each sampling period and used with XRF data to select samples to be analyzed by INAA. 

The haze which can be seen in fair weather is mainly due to submicron ammonium sulphate particles. This aerosol also contains soot, agglomerates of very small carbon particles with adsorbed high molecular weight organic compounds and appreciable amounts of certain trace elements, e.g. lead, zinc, iron, nickel, cadmium etc. 

Senior CL, Helble JJ, Sarofim AF (2000) Emissions of mercnry, trace elements, and fine particles from stationary combustion sonrces. Fnel Process Technol 65 263-288 Seto T, Nakamoto T, Oknyama K, Adachi M, Knga Y, Takenchi K (1997) Size distribntion measurement of nanometer-sized aerosol particles nsing DMA nnder low-pressure conditions. J Aerosol Sci 28 193-206... 

Fig. 2 shows the different pathways in which chemical elements contained in rocks are released to the different environmental compartments. Five main processes are responsible for their dispersion into the different ecosystems (1) Weathering, either directly by rain water on rock outcrops, by soil percolation water or by root exsu-dates, which interact with rock fragments, contained in the soil cover (2) Down hill mechanical transport of weathered rock particles, such as creep and erosion and subsequent sedimentation as till material or alluvial river and lake sediments (3) Transport in dissolved or low size colloidal form by surface and groundwater (4) Terrestrial and aquatic plants growing in undisturbed natural situations will take up whatever chemical elements they need and which are available in the surface and shallow groundwater. Trace elements taken up from the soil will accumulate in the leaves and will possibly enrich the soil by litterfall (5) Diffuse atmospheric input by aerosols and rain rock particles from volcanic eruptions, desertic areas (Chester et al., 1996), seaspray and their reaction with rain water. A considerable part of this can be anthropogenic. 

Arimoto R, Ray BJ, Duce RA et al (1990) Concentrations, sources, and fluxes of trace-elements in the remote marine atmosphere of New Zealand. J Geophys Res 95 22389-22405 Arimoto R, Duce RA, Savoie DL et al (1992) Trace-elements in aerosol-particles from Bermuda and Barbados—concentrations, sources and relationships to aerosol sulfate. J Atmos Chem 14 439 57... 

Aerosol work has also profited from micro-PIXE, as single particle analysis has become feasible. Accurate correlation between the chemical composition of such particles and their size and shape provides information about the sources of the particles and about the transformations that take place during atmospheric transport. In other environmental studies, micro-PIXE has been used to measure the uptake of trace elements in plants, roots, and trees. In parti cular, tree rings, which also record time information, have been analyzed in several laboratories. 

Figure 2 shows the PIXE spectrum from a single ambient aerosol particle, showing the major and trace elements detected. 

Quay J, Reed W, Devlin RB. Residual oil fly ash upregulates IL-6 gene expression by processes involving NF-kB. Am J Cell Respir Mol Biol 1998 19 98-106. Schroeder WH, Dobson D, Kane DM, Johnson ND. Toxic trace elements associated with airborne particulate matter a review. Environ Sci Technol 1987 9 838-845. Mathias-Maser S, Jaenicke R. Examination of atmospheric bioaerosol particles with radii > 0.2 J.m. J Aerosol Sci 1994 25 1605-1613. 

The submicrometer mode of all the 35 elements determined by INAA, occured at 0.11 Mm except for those of Cr (Figure 3) and Mn (not shown) which occurred at 0.14 Mm. Particles in this size range are so highly concentrated (10l3 particles/cm at 0.07 Mm) that they coagulate very rapidly. Therefore, the shift in the modes of Cr and Mn may correspond to a temporal increment separating the formation of Cr and Mn aerosols from the other elements. Alternatively however, this may indicate that Cr and Mn aerosols are formed by a different mechanism than are the other elements. More careful analysis of the modes of the individual elements may provide insights into the trace-... 

Ultrafine aerosols are commonly defined as particles with diameters less than 0.1 /rm fine particles have diameters of approximately 0.1 to 2 /xm. Fine particles may be formed by coagulation of ultrafine particles or through gas to particle conversion processes. In industrialized areas, fine particles tend to be mainly composed of SO -, NO3, NFff (all from gas to particle conversion processes), elemental carbon, organic carbon, and trace metals. Particles formed from gases are typically less than 1 ptm in diameter and cause reduced... 

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