The author investigated a 0-3 cm layer of two forest brown soils: brown acid and brown leached. These forest soils were under handsome beech trees (Fagus sp.) between 100 and 120 years old. The author compared the chemical properties of the soils. The soil existing near the tree trunk (1 m² of surface, strongly washed by rain water polluted by chemical substances) and the soil existing under the tree umbrella ( 40 m² of surface in the area of the tree-tops, washed poorly by rain water). This comparison showed changes in these properties, dependent upon the degree of atmospheric contamination. It was found that, at the same level of atmospheric contamination, higher changes of properties were found in brown leached soil than in brown acid soil. Less acidified soils (with alkaline or neutral pH reaction) are more suitable in these researches. The investigations of the forest soil layer 0-3 cm (12 soil profiles) showed that changes in their chemical properties in relation to tree trunk-tree umbrella can be the basis of assessment of the degree of atmospheric contamination.