Toxic substances in waters or in sediments also affect soil organisms (edaphon) and can substantially modify their survival in the flooded soil. Harmful agents penetrate into the soil for a short time during floods, and for a long time in the case of acid rain. Even changes in soil water pH values influence soil biota. Both the equilibrium and species composition in soil assemblages, food webs, organic matter decomposition and soil-forming processes are disturbed by these processes.
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