EN
The studies were conducted on peat materials at various states of secondary transformation characterised by the W1 index. The positive correlation between the specific surface area calculated from water vapour adsorption and the water holding capacity index W1 was found. However, no direct relationship between the specific surface area determined from nitrogen adsorption was noticed. The variable surface charge increases with the value of W1 for all samples. The soils investigated are divided into two groups. For investigated soils only the dispersive surface free energy component can be determined. Contact angles were calculated using the component of the surface free energy and water surface tension determined earlier by the Young equation.