**4. Conclusions**

We conclude that:

**Figure 3.** Linearized Freundlich isotherms for atrazine adsorption (A) and desorption (B) from a clay-loam soil.

Clay-loam 8.2148 0.8230 0.992 0.0001 5.4992 1.436 0.245 0.036 0.573

**Table 2.** Freundlich isotherm parameters and hysteresis index values for atrazine adsorption-desorption in a clay loam

The Freundlich constant for adsorption of atrazine was 8.2148, which was higher than that reported by Kulikova et al. [7], who studied the absorption of atrazine to three soils with different textures (silt-loam: sod-podzolic [*K*F = 4.51] and gray forest [*K*F = 0.81] and clay-loam: chernozem [*K*F = 5.54]). These authors suggest that clay-loam soil has high levels of organic carbon (organic matter), which leads to a high rate of atrazine absorption. In our study, the soil also possessed this characteristic, as a high organic matter content (4.35%) was detected in the soil analysis due to the incorporation of crop residues (sugarcane stalks) to the soil. In another study, Naga-Madhuri et al. [40] reported a lower *K*F (=2.66) for atrazine adsorption in a silty clay-loam soil; the authors suggested that this value is high and may be due to the high electric

*K***<sup>F</sup>** *n r***<sup>2</sup>** *P-***value** *K***<sup>F</sup>** *N r***<sup>2</sup>** *P-***value H**

<sup>F</sup> log log 1/ log *q K nC e e* = + (1)

= regression coefficient; H = hysteresis index.

**Soil Adsorption Desorption**

202 Soil Contamination - Current Consequences and Further Solutions

*K*F = Freundlich adsorption-desorption constant; *n* = absorbent constant; *r*<sup>2</sup>

conductivity and organic matter content of the studied soil.

soil.

