## 3 Results and Discussion
### Environmental Indicators  
The Mobility Factor (MF), Geo accumulation Index (Igeo) and Enrichment Factor (EF) were used to assess and quantify pollution levels on the substrates of the study area. The mobility factors are presented at the end of Table 7, varying from 8.74 to 46.13% with a mean of 26.67%, and from 14.01 to 55.75% with a mean of 28.48% for soils and sediments, respectively. Sites S1 and S2 had the lowest mobility factors observed in the dry period, whereas site S12 presented the highest values for both rainy and dry season for soil. In sediment samples, the lowest value was obtained in sample S22 and the highest value in S1, both obtained during the rainy season. The MF high value of S1 is consistent with the high value of the carbonates bound fraction. Overall, the mobility factors for Pb exceeded 20% (62.5% for soil and 93.7% for sediment), thus representing significant bioavailability for living organisms and a potential threat to the environment [40; 41].  
The Igeo has been widely employed to assess environmental contamination by comparing differences between current and preindustrial concentration in soils and sediments samples [57; 58]; Figure 2 shows the Igeo values of Pb at each sampling site vary in a wide range, with at least one sample in each class, from \"unpolluted\" (class 0) to \"extremely polluted\" (class 6). However, a reduction in the content of Pb can be observed with increasing distance from the mine, with a subsequent increase at point S22 (City of Aguascalientes) that was classified as \"moderately polluted\" to \"highly polluted\". S4 showed similar indices from \"unpolluted to moderately polluted\" to \"highly polluted\"; S1 and S2 (sites nearest to mining activity) with significantly higher indices than in other sites, from \"moderately polluted to highly polluted\" (class 3) to \"extremely polluted\" (class 6). Sediment samples at these sites were classified as \"extremely polluted\" (class 6) making the influence of mining activity on the environment evident. The highest-class level (class 6) reflects an enrichment of almost 100-fold when compared with the background level [59].  
The EF values of Pb in soil and sediment samples are shown in Figure 3. Aluminum, the most common reference value used to calculate the EF, was selected to be the normalizing element [45; 46], with the values for the samples provided in Table A1 (Appendix A). EF has been widely used to quantify the degree of metal enrichment or contamination in soils and sediments samples due to human activity [60; 61; 62]. As was the case in the Igeo analysis, sites S1 and S2 were categorized as having \"extremely high enrichment\", for both soils and sediments. With the exception of sediment samples obtained during the rainy season, site S4 also represented \"extremely high enrichment\"; the low value for S4 to sediment  
Figure 2: Index of Geo Accumulation for soils and sediments during dry and rainy seasons. Class: 0 (Unpolluted), 1 (Unpolluted to moderately polluted), 2 (Moderately polluted), 3 (Moderately to highly polluted), 4 (Highly polluted), 5 (Highly to extremely polluted), 6 (Extremely polluted).  
in rainy season is due to the increase in the volume of the reservoir, confirming with the pseudo-total concentration of Pb for that sample (see Table 7). S6 for soil and sediment during all seasons and as S12 and S15 for soil during the rainy season showed the lowest EF values, classed as \"moderated enrichment\". The rest of the samples were categorized as having \"significant enrichment\" (Class 3) or higher. It's important to note that values above 1.5 suggest anthropogenic origin [60; 61; 62].