Biogeochemical exposure processes in the soil-water system

A brief review of soil leaching processes (after Johnson, 1992) 

A concept of anion mobility may be considered a useful paradigm for explaining the net retention and loss of cations from soils, and thus exposure pathways. This paradigm relies on the simple fact that total cations must balance total anions in soil solution (or any other solution), and, therefore, total cation leaching can be thought of as a function of total anion leaching. The net production of anions within the soil (e.g., by oxidation or hydrolysis reactions) must result in the net production of cations (normally H+), whereas the net retention of anions (by either absorption or biological uptake) must result in the net retention of cations. 

The higher concentrations of some heavy metals, like Zn, Cu, Ni, and Pb, in snowmelt waters in comparison with rain waters is possibly related to the elevated content of solid particles in snow. Deposition fluxes are less important in the 

Trace metal Rainwater Snowmelt water Ground water Rainwater Ground water 

We can see the rise of heavy metal groundwater contents in the southward direction with increasing content of total soluble salts. However, this increase is not similar for various metals. For example, Zn is the most abundant metal in the waters of Tundra 

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