*3.1.2 Spatial variability*

To assess the spatial distribution, sulfate atmospheric deposition fluxes were analyzed by site. A mean value of 13.78 Kg Ha<sup>−</sup><sup>1</sup> year<sup>−</sup><sup>1</sup> was found, with a maximum value of 25.82 Kg Ha<sup>−</sup><sup>1</sup> year<sup>−</sup><sup>1</sup> . From **Figure 3**, it can be observed that the highest mean value was found in site IV (Instituto Tecnológico de León) located at SE, whereas the minimum value (1.81 Kg Ha<sup>−</sup><sup>1</sup> year<sup>−</sup><sup>1</sup> ) was registered for site III, where monitoring station IMSS-T21 is located just at downtown of the city. Considering extreme values, the higher fluxes were found for site IV; however, when Friedman test was applied, significant differences were not found. It suggests a certain homogeneity in sulfate deposition levels in the study region, which confirms the regional character of sulfate precursor (SO2).
