Evaluation of the soil quality in the vicinity of Inowrocław soda plants

The aims of this study were to assess the quality of soils affected by strongly saline waste products and to analyze the spatial distribution pattern of soil properties influenced by a soda plant. Soil samples were analyzed for electrical conductivity (EC), sodium adsorption ratio (SAR), pH, trace element content and dehydrogenases activity. The research was conducted in the vicinity of the waste ponds of the Ciech Soda Poland S.A. company (Central Poland), where 35 groundwaters, 63 surface (0–20 cm) and 60 subsurface (80–100 cm) samples were collected. Although the waste ponds are currently not used for regular disposal of waste products, a high level of salinity of groundwater and soil, especially in the subsurface layer, is still being observed. The electrical conductivity of soil saturation extract (ECse) values varied between 0.9–15.4 and 1.0–87.2 dS·m^-1 for surface and subsurface layer, respectively. Analysis of the spatial distribution of soil salinity reveals a correlation with microrelief and groundwater levels. Maps of the spatial distribution of heavy metals showed that their content in the subsurface layer was a result of chemical migration from the waste ponds, and in the surface layer by other sources (atmospheric deposition). The soil salinity did not influence dehydrogenases activity.