Ecological and hygienic importance of mercury to environment results from its physical and chemical properties. At temperatures usual for the temperate climatic zone, the mercury is a liquid metal with relatively high tension of saturated vapours. Interaction of these vapours with a solid phase is realised predominantly by physical forces on the phase interface through the mediation of the adsorption mechanism. Contamination of the soil occurs and the soil consequently becomes an emitter of mercury since the processes of physical adsorption and desorption in the environment are reversible processes. On three examples the authors demonstrate the manifestations of physical adsorption and desorption on the soil samples and point out the relevant part of this contamination mechanism in the entire soil contamination. From the point of view of a possible separation of individual contributions to the solid phase contamination, either of anthropogeneous or natural origin, the authors recommend to use the recording of a thermodesorption curve for defining three regions characterizing the origin, or forms of mercury and its bound to the solid phase. Authors state that the current analytical methods for determining the mercury concentration in a solid phase provide an information on the so called entire mercury in it but do not distinguish individual mercury forms. From an ecological as well as hygienical point of view, the mercury content in a solid phase reveals more important from the physical adsorption, as it is the mercury form which is very mobil and interactive in respect of the other components of the environment.