**4. Conclusions**

The use of a dissolved organic matter solution had a direct effect on the soil reduction conditions, improving the reduction of Cr (VI) to Cr (III) and producing a precipitate of chromium that accumulated in the soil matrix.

In the species distribution diagram of chromium, the oxidation–reduction potential and pH values found in the soil-saturated solutions correspond to the area of predominance of Cr<sup>2</sup> O3 , which is not water soluble and is thus difficult to leach.

The chromium accumulated in the soil profile may have combined with natural organic matter such as humic and fulvic acids.

The 3D fluorescence analysis of the soil-saturated solutions showed the presence of natural organic matter (humic and fulvic acids) throughout the soil profile.

The highest accumulation of chromium occurred in the first 10 cm of the soil column, suggesting, like the Bach tests, that chromium has a high affinity for organic matter, as evidenced by the Kd values.

The dispersion coefficient of humic acids was similarly to that of chromium, so it is possible to assume that Cr (VI) species may have complexed with humic acids.
