Mobilization of Soil Organic Matter by Ultrafresh Water: Modeling and Assessment of the Impact on the Mobility of Heavy Metals

The experiments on mobilization of soil organic matter during soil washing with ultrafresh water against the background of salinity pulsing were designed and performed. Unpolluted soil and the soil artificially polluted with copper(II) were used in experiments, namely, clay loamy typical chernozem (Haplic Chernozem) of the Alekhin Central Chernozemic Nature Reserve (Kursk oblast, Russia; 51°34.207 N, 36°05.444 E) and sandy loamy soddy-podzolic soil (Albic Glossic Retisol (Loamic, Cutanic, Ochric)) from the Domodedovo district of Moscow oblast, Russia (55°17.683 N, 37°50.045 E). Soil samples were taken from the upper humus-accumulative (A1) horizon (5–15 cm). A drastic change in the composition of washing solution from fresh water to 0.1 M NaCl solution and back led to destruction of soil aggregates under the impact of osmotic pressure. Soddy-podzolic soil proved to be more resistant to destruction as compared with typical chernozem. Copper(II) was leached off from artificially contaminated samples of soddy-podzolic soil with the flow of dissolved organic matter, whereas copper leaching from typical chernozem was associated with the destruction of aggregates and release of intraaggregate organic matter. It is argued that copper (II) migration models should take into account the amount of dissolved organic matter for soddy-podzolic soil and the content of aromatic fragments in the organic matter for typical chernozem. A conceptual model of the Cu(II) leaching from contaminated soddy-podzolic soil and typical chernozem in the course of soil washing with fresh water against the background of salinity pulsing and the destruction of soil structure is constructed.