Soil salinization processes in the impact zone of mineralized water discharge by the case study in the Yaroslavl Volga region, Russia

Abstract

Humid conditions do not encourage the formation of salt-affected soils due to leaching salts out of soil profiles. Nevertheless, the occurrence of salt-affected soils in a humid climate is evident as a result of other factors excluding the climate. Soil salinity in these landscapes is caused by anthropogenic salinization. The objective of this study was to identify types of chemical composition and salinity level of soils forming within the impact zone of artesian water discharge. We also determined the degree of contrast to adjacent non-saline soils and salt contamination boundaries. Soil and water samples were collected from three sites located in the Yaroslavl’ region, the Upper Volga. Sampling was done in June 2017. In the Upper Volga region high-mineralized water rises from saline aquifers via abandoned exploration wells drilled in the 1960s. These soils are found under an average annual rainfall of about 500–700 mm in the taiga zone. This type of climate and vegetation cover normally should lead to the formation of Albic Retisols. Saline waters affecting soils are dominantly Na-Cl or Ca-Na-Cl-SO4 brines. Total dissolved solids in the saline waters range from 10000 to 259500 mg·L–1. Salt-affected soils have from low to high salinity (0.1–0.8 %) but salt content does not exceed 1 %. In the study areas, maximum salinity in the investigated soils was fixed near the water table or was associated with lithic discontinuity or abrupt textural change. Salt leaching from the upper horizons prevails in the course of the annual cycle and that is what differs these soils from hydromorphic saline soils formed in arid climates. Field electrical surveys of salinity indicated the local zones of salinization. The salinization phenomenon in humid climates is not part of the main pedogenic processes, but an additional process. The upper horizons of salt-affected soils tend to have similar morphological features to zonal and intrazonal soils. The salt-affected soils studied were classified according to WRB as Orthofluvic Fluvisol (Humic, Loamic, Endosalic, Technic), Orthofluvic Gleyic Fluvisol (Humic, Siltic, Endosalic, Raptic), Amphistagnic Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic) and Albic Retisol (Siltic, Anoaric, Cutanic, Endosalic, Raptic).