Seasonal Resistivity variations in some different swedish soils

摘要

Soil resistivity can vary considerably due to factors such as variation in geology, temperature, water content and water composition. When resistivity measurements are used for long-term monitoring purposes, it is of importance to estimate the natural variation depending on the season, so that possible anomalies can be distinguished. The study of seasonal resistivity variations and the reasons for these is also important for several fields of applications in agriculture, environmental and engineering geology. Resistivity variation measured during several years in five different geological environments in mid-Sweden were found to be noticeably large in coarse-grained material and dgyttja clay. The variation in apparent resistivity was 68 percent of the mean value in a clayey till, and over 90 percent of the mean value in the gyttja clay. The variation in fine-grained material also proved to be rather extensive. To find out which seasonal factors were the most important to explain the variation in the resistivity, correlations were established with groundwater level, precipitation and simulated soil water-content of the investigation area. The variation in resistivity could to some extent be explained by the seasonal variation in groundwater level and soil water-content, but not by the variation in precipitation.