**Author details**

presence of these humic substances. Moreover, the R<sup>2</sup>

soil. The results showed the presence of the species Cr<sup>2</sup>

which is not water soluble and is thus difficult to leach.

organic matter (humic and fulvic acids) throughout the soil profile.

to assume that Cr (VI) species may have complexed with humic acids.

for the remediation of soils and waters contaminated with Cr (VI).

with humic acids.

42 Agricultural Waste and Residues

**4. Conclusions**

the Kd values.

Agua (CIRA).

**Acknowledgements**

**Conflict of interest**

that accumulated in the soil matrix.

ter such as humic and fulvic acids.

showed that the isotherm can describe the sorption or complexation behavior of chromium

An X-ray diffraction analysis was performed to verify the precipitation of chromium in the

layer with the greatest amount of organic matter, confirming the removal of chromium by precipitation. Considering that most of the reducers used here and reported in the literature are less effective at alkaline pH values [5], natural organic matter (humic acid) could be used

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

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>

The chromium accumulated in the soil profile may have combined with natural organic mat-

The 3D fluorescence analysis of the soil-saturated solutions showed the presence of natural

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 dispersion coefficient of humic acids was similarly to that of chromium, so it is possible

This study was funded by Instituto Potosino de Investigación Científica y Tecnológica (IPICYT) and Universidad Autónoma del Estado de México - Centro Interamericano de Recursos del

The authors declare is no conflict of interest regarding the publication of this paper.

O5 , Cr5

O12, CrO<sup>2</sup>

values found along the soil column

, and Cr7

C3

in the soil

O3 , Rosa María Fuentes-Rivas1,4\*, Francisco Martin-Romero<sup>2</sup> , Daury García Pulido<sup>3</sup> , Reyna Maria Guadalupe Fonseca-Montes de Oca3 , Janete Moran Ramírez<sup>4</sup> and Jose Alfredo Ramos Leal<sup>4</sup>

\*Address all correspondence to: rmfuentesr@uaemex.mx

1 Facultad de Geografía, Universidad Autónoma del Estado de México, Toluca, Estado de México, México

2 Departamento de Geoquímica, Instituto de Geología, Universidad Nacional Autónoma de México, México D.F., México

3 Centro Interamericano de Recursos del Agua, Toluca, Estado de México, México

4 División de Geociencias Aplicadas, Instituto Potosino de Investigación Científica y Tecnológica, San Luis Potosí, México
