Abstract. Basing on the concepts of the strongly acidic (TCA) and weakly acidic (TA) nature of the ionexchangers of soil colloids, the physicochemical behavior of heavy metals in soils is discussed. It is shown, that their physicochemical behaviour, depending on soil acidity passes through: 1) an ionic (toxic) mobilization in the case of incomplete neutralization of the strongly acidic ionexchanger by strong bases (Ca, Mg, K...) (soil pH <6.0); 2) a universal for plants acidic optimum, when the strongly acidic ionex changer is fully neutralized by strong bases, while the weakly acidic ionexchanger is protonated (pH around 6.0) and 3) a hydroxide precipitation (immobilization), when the hydrolytically alkaline salt of the weakly acidic ionexchanger with adsorbed strongly basic cations is active ( pH>6.0). On that basis, the permissible copper and zinc concentrations in soil are presented not as separate numbers, but as functions of soil acidity