Diagnosis and character of hydromorphic salinization of the “Varnicy” landscape (Rostov Veliky, Yaroslavskaya oblast’): experience and methodology of geo-electric methods application

Abstract

The main objective of this study is to find out the application of electrical resistivity measured in water saturated soil (ER) as a proxy to soil salinity assessment within a humid climate landscape located in the center of the Russian plain. The issue is not the only salinization, but some other processes controlling the soil formation can influence the ER significantly. These processes attributed to the phreatic water salinization are waterlogging, soil organic carbon accumulation, carbonate and gypsum sedimentation. For evaluation of landscape salinity of the nature reserve “Solyanoj istochnik Varnicy”, where saline spring discharging, soil and water samples were collecting five times during an annual monitoring study (2016–2017). The samples from the two soil pits and water samples from the spring, groundwater and surface water draining the local catchment were analyzed in terms of the relationship between the ER values and major ions concentrations. Correlation analysis revealed a close relationship between the values of ER and TDS, calcium and sulfate content in the soil water extract. At the same time, parametric statistical analysis found that seasonal fluctuations of ER were due to short-term fluctuations in sodium and chloride concentrations. The ER values measured in the drainage and groundwater of the study site were more sensitive as compared with the soil to changes in the salinity level during the annual hydrological cycle. A high correlation coefficient was observed between the ER and both the total salt content and the major ions concentrations in water samples. Geospatial salinity variation and salinization area were detected by horizontal electric profiling (HEP) within the site previously covered with detailed geodetic surveys. With an example of the hydromorphic Varniсky section in the humid climate it was shown that high soil salinity plays a main role in the resistivity value formation compared with other factors. The electrophysical parameters can be reliable indicators in monitoring studies of landscape salinity.