In this work it was estimated accumulation of iron in the upper lake of Rose Valley park of the Chisinau, separating different forms of metal migration's and contribution of this forms in self-purification processes with free radicals. Approximate balance for iron in the upper lake shows that annual accumulates 129,78 kg of metal and from this amount of the metal deposits 89,33% in bottom sediments and 10,67% remains in the liquid phase. It was found that the winter-spring seasons, colloidal forms of iron with size (0,2 ÷ 0,45) have a favorable influence on radical self-purification processes, compared to dissolved forms. Seasonal migration of total iron show that maximal concentration of metal in the object of research was established in summer (232, 25 μg/l), and the minimum concentration was detected in winter (63, 25 μg/l) and autumn (8, 5 μg/l).