The experimental data are presented on lowering concentration of chrome(VI) ions in soil (with a purpose of rendering it harmless) by nanoparticles of iron in the presence of high concentration of an organic compound (saccharase) as a reducing agent. The reiterated repetition experiments has proved an effectiveness of synthesized before iron nanoparticles. The basic parameters of an effective reduction of Сr(VI) by nanoparticles of iron have been found out. They are as follows: the time of reduction (2 h) and concentration of organic substances (35.71 g/kg of soil). It has been established that a rise in reduction duration above 2 h lowers its effectiveness. The cause of this, revealed by us, consists in that a high concentration of the organic compound provides for inhibitating of Cr(VI). It occurs on account of 1) adsorption of substance on a surface of iron nanoparticles and as a result the decrease in their active surface, 2) interaction of the organic compound with the products of the reduction reaction, 3) dissolution of saccharase in liquid phase. As result of investigation the necessity of determining the significance of high concentration of the organic substance for an effective reduction of Cr(VI) in soil is exposed. At present the work in this direction is being continued.

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