ИСТИНА

Culture layers of ancient cities or urbosediments (US) and technogenic surface formations (TSFs) formed on the waste of mining enterprises and technogenic recrementogenic (sewage sludge, household waste) deposits of buried dumps of solid domestic and industrial wastes are increasingly spreading on the Earth's land surface. The soils on them radically differ from natural soils in morphology and composition and can be distinguished as soils of extreme conditions. US of ancient cities have a large capacity, contain features of past stages of urbopedogenesis, but also represent the parent material of modern urban soils. The US in the north of European Russia forming in conditions of humid climate and flat relief are represented by deep (2-5 m) organic layers, with a loss on ignition value of 50-80% and being in a constant waterlogged state. For several centuries, there was a relatively rapid accumulation of the remains of wooden buildings and other organic matter, as well as the accumulation of P, S, Ca, etc. Nowadays, organic layers are characterized by the decomposing organic matter and intensive carbon dioxide emission into the atmosphere, as well as a rapid loss of sulphur. So, in that case we see human-induced soils in extremely rich substrate conditions. US of southern cities with semiarid climate are characterized by loess or rocky mineral layers, with the features of carbonatization and salinization, with very low accumulation of carbon – extremely uncomfortable conditions for the pedogenesis. Many technogenic deposits (dumps, tailing dumps, etc.) are often enriched with toxic heavy metals: Pb, Zn, Sr, V, etc., the content of which several times exceeds the background values. They also contain by-product chemical compounds of production and flotation reagents (sulfides, salts, cyanides, phenols, etc.). The extremely toxic conditions for pedogenesis result in impoverished vegetation and soil biota for TSFs on recrementogenic depositions of landfills. The other uncomfortable factor for soil development in such conditions is high density of substrates and thus the limitation for root and mesofauna penetration. So, anthropogenic factors may result in extreme conditions for soil formation, both very rich and very poor in pedogenically important resources.