Electric Resistivity of Soils and Upper Permafrost Layer of the Gydan Peninsula

Abstract

Soils of the Gydan Peninsula have been investigated during the complex expedition “Yamal Arctica 2013” during the “Professor Molchanov” vessel route in August and September 2013 with special aim to characterize soil morphology in relation with parameters of electric resistivity with use of vertical electric sounding methodology. Data obtained show that soils investigated are quite different in terms of solum morphology, soil stratigraphy and active layer thickness. Main soil types of the Gydan Peninsula (Siberia, Russian Federation) are Cryosols with features of raw organic matter accumulation and gleyification features. These soils dominate on the watersheds and in lowlands due to poor drainage of parent materials and presence of continual permafrost in landscape. In some cases, two Gleyic layers formed in one soil profile – one in the upper or middle part due to seasonal fine earth over moisting, and second one – on the contact of the solum with permafrost. Histic soils with Cryic features are more typical for lowlands (relief depressions). Soils of the Beliy Island are presented by slightly podsolised soils in upper part, this is due to lithological contrast of sediments (sandy textured solum changes by loamy textured one). The Electric resistivity (ER) was measured directly in the soil profiles with using the vertical electrical sounding (VERS) method, which provides data on the changes in the electrical resistivity throughout the profile from the soil surface without digging pits or drilling. This method allows to divide the soil pit vertically into layers with different properties. A VERS modification with shorter electrode spans was used to study the upper up to 5-m thick layer in detail. The distance between the A and B electrodes was from 5 to 500 cm. Soils have been sounded be thoroughly from the 5 cm to 3-5 m in depth. It was shown that use of VERS methodology in soil survey is quite useful for identification of the permafrost depth without digging of soil pit. This method allows identify soil heterogeneity, because the ER values are strongly affected by soil properties and intensively changes on the border of different geochemical regimes, i.e. on the border of active layer and permafrost. VERS data obtained show that the upper border of the permafrost layer coincides with that border, which were identified in field on the base of soil profile morphology. The VERS method also can be used for identifycation of Gleyic, Histic and Podzolic layers. VERS methodology is useful for preliminary soil survey in the regions with permafrost affected soil cover. It is also can be applie