Soil, erosion aerosol

The SDA dispersiveness in the air surface layer is determined by natural dispersiveness of soil as a source of aerosol, and by effectiveness of the sand-jet effect of saltating particles. The formation of the real size distribution of SDA in this atmospheric layer is determined by the processes of sedimentation, impingement, condensation and adsorption of gases and vapors, capture and sedimentation on obstacles and surfaces [6]. Real size distributions of soil-erosion aerosols (SEA) can be described by the power law ... 

Vanadium was discovered in 1830. It is present at 0.01% in earth s crust. Vanadium is released naturally into the air through the formation of continental dust, marine aerosols, and volcanic emissions. The natural release of vanadium into water and soils occurs primarily as a result of weathering of rocks and soil erosion. Anthropogenic sources include the combustion of fossil fuels, particularly residual fuel oils, which constitute the single largest overall release of vanadium to the atmosphere. Deposition of atmospheric vanadium is also an important source... 

Gillette, D. A. (1974). On the production of soil wind erosion aerosols having the potential for long-range transport. J. Reck Atmos. 8, 735-744. 

Figure 2 shows results at the ground site for a one-week period in June, when crops (corn and soybeans) were short enough to allow the generation of soil aerosols through cultivation and wind erosion. Figure 3 shows results from the tower sampler for a two-week period in July when crops were mature. Cultivation should have been absent, and wind erosion very limited, during this period. 

Figure A and 5 show results for a period during and after harvest, in October and November, 1978. Generation of soil aerosol by tilling was observed, and wind erosion was possible, during this period because of the removal of the crop cover from the soil surface. Figure A shows results of three weeks of sample collection from the ground site, and Figure 5 shows results from four weeks of sampling on the tower.

The natural mechanisms of atmospheric aerosol generation are as follows soil-wind erosion, ejections to the atmosphere of salt particles from sea and ocean surfaces, emission of gases and vapors by photo-synthesizing plants and by decay products, ejections of the products (soot aerosol, first of all) of natural fires of forests, steppes, peat bogs, and also volcanic eruptions. 

Consider whether the natural origins of vanadium account for the amounts observed. The major natural sources are marine aerosols produced by the bursting of bubbles at the sea surface and continental dust from wind erosion of rocks and soil. Some vanadium would also be injected into the atmosphere by volcanoes, but in the treatment below this is a minor perturbation on the dust contribution. 

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. 

Sea spray, volcanic eruptions, soil dust, as well as some industries (cement manufacturing) produce the so called primary aerosols, i.e. the material is emitted directly in particulate state (Klockow, 1982), and they are both line and coarse. Secondary aerosols are produced in the atmosphere usually by eondensation after emission from high temperature sources, and they are fine as a rule. Considering the difference in the chemical composition it is recognized that the major components of the fine aerosols are toxie substances of anthropogenic origin such as As, Cd, Pb, Se, Zn etc. while the course aerosols are enriched in elements like Ca, Fe, Si coming from erosion, sea aerosols and other natural sources. 

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