Pedogenesis of Soils Formed in Technogenic Parent Materials.

Soils formed in technogenic parent materials are spreading in the world and their pedogenesis remains still inadequately known. As a result of human activities, technogenic materials are likely to display a wide range of constituents and properties, a high spatial variability and a discontinuous deposition, which may influence the soil formation. The potential specificities of the pedogenesis of these soils was discussed from the previous investigation of a soil formed in iron industry deposits and from the literature concerning soils formed in various technogenic materials (e.g. construction debris, mine spoil, excavated bedrocks, sediments). Processes occurring in these soils are generally similar to processes leading to the development of natural soils but some of them are rarely encountered simultaneously in natural environments. Inherent features of technogenic materials (e.g. original mixture of constituents, high spatial variability, temporal discontinuities) in interaction with other soil-forming factors, make possible the simultaneity of processes, coexisting rarely in natural soils developing in the same pedoclimatic region. This particular combination of processes and their possible interactions during the early pedogenesis of soils formed in technogenic materials could orientate their evolution. The prediction of the evolution of these young soils influenced by human activities requires to further investigate these peculiar combinations of processes and their potential interactions in a larger range of soils formed in technogenic materials. Modeling of pedogenesis should be adapted to take into account these possible complex relations between the processes, which could change the orientation and the rate of pedogenesis. Space-scale should be adjusted to fit the potential distinct soil development over a short distance, related to the usual high spatial variability of technogenic materials. Time-scale should take into account the likely evolution in several steps of varying rate, depending on the reactivity of the technogenic materials to the environmental factors.