To understand what changes in the soil may be brought about by a change in the level of atmospheric acid deposition, it is useful to develop at least a conceptual model of the major system components and the processes by which they interact. The interaction between the solid and solution phases in the soil is critical in determining the nature of these changes. Although the system in total is extremely complex, a relatively simple subset of the processes involved is sufficient for our purpose. In this chapter, we describe the major processes that control the composition of the soil solution and how this composition is modified by acid impact. Our approach is to consider the anions in solution and the processes by which their concentration is controlled. The principle of electroneutrality requires the equivalence of positive and negative charges, so that if the anion concentrations are known, the total charge of the cations in solution is also known. We can then proceed to consider the processes by which the distribution of the various cations in solution is determined.
KeywordsSoil Solution Organic Anion Base Cation Acid Deposition Base Saturation
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