*4.2.1 Mine tailings*

*Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques…*

of sulfide tailings. Fe-oxides and Fe-hydroxides have also been identified.

In some occasions, the ore minerals are not identified by X-ray diffraction, or are identified in low amounts. In these cases, a detailed study by environmental scanning electron microscopy (ESEM) coupled with energy dispersive X-ray analysis (EDX) is necessary. Four examples of the application of ESEM-EDX are presented in **Figure 2**. Primary sulfide minerals (e.g. galena) identified in low amounts by XRD were also recognized by ESEM-EDX in Monte Romero tailings. Galena occurred as cubic crystals commonly showing octahedron faces. Other sulfide phases such as arsenopyrite, chalcopyrite, and galena were not detected by X-ray diffraction in La Naya tailings. Secondary mineral phases recognized by ESEM-EDX were Fe-oxyhydroxides. Cryptocrystalline Fe-oxyhydroxides frequently occurred around other minerals such as quartz, completely or partially replacing primary sulfides (pyrite and sphalerite). In San Quintín mine, primary ore minerals were not identified by XRD due to the optimized mining works. Pyrite, galena, chalcopyrite, and gangue minerals (barite) were identified by ESEM-EDX (**Figure 2**). In San

inefficient metallurgical processing of the benefited ore during the operational years. Because of the re-working of tailing mine areas, San Quintín area shows the lower ore mineral content. In other cases, like Brunita deposit, different ore minerals amounts are associated with the two different mines exploited and dumped: Brunita and Eloy mines. Cinnabar was identified by X-ray diffraction in one borehole sample from San Quintín. Its presence is due to the experimental metallurgical works carried out during the last period of operations in the Almadén mine (Ciudad Real, Spain). Secondary mineralogy is mainly represented by Fe-sulfates (jarosite and rozenite), Ca-sulfates (gypsum), and Al-sulfates (alunite). Fe-bearing sulfide oxidation increases the metal mobility from these materials compared to the levels mainly composed by sphalerite and galena. Significant amounts of secondary gypsum are typically found in this type

*Backscattered electron (BSE) images: (a) galena crystal from Monte Romero; (b) pyrite crystal from San Quintín; (c) altered faces of a pyrite crystal from San Cristóbal; (d) subidiomorphic magnetite from Las* 

**94**

**Figure 2.**

*Moreras.*

Total ferric iron (Fe2O3total), S, and trace element (Ag, As, Au, Cd, Cu, Ni, Pb, Sb, Sn, and Zn) concentrations, and pH values from tailing samples of the four mine district are summarized in **Table 3**. All samples showed a pH range of 2.2–5.6. This value range reflects the typical acid character of stored mine tailings. The composition of all tailing samples is characterized by the high contents of ore-bearing elements in each district: As, Cu, and Pb in the Iberian Pyrite Belt, Pb and Zn in Cartagena-La Unión and Alcudia Valley, and As, Pb, and Zn in Mazarrón. The total ferric iron content is significantly high in analyzed samples from all mine districts due to the omnipresence of Fe-bearing minerals like pyrite. The significantly high contents of potentially hazardous elements like Fe, Cu, Pb, and/or Zn are due to the nature of the mined ore, which is mainly composed of pyrite, chalcopyrite, sphalerite, and galena (**Table 2**). The highest metal contents are related to the mining history of each district, and the efficiency of the metallurgical processing in the benefited ore during the operational period of time. In the case of San Quintín mine, approximately 3 million tons of minerals from the tailings were re-worked. Then, the lowest Pb and Zn contents are located at the upper levels of the ponds. High Hg content measured in the San Quintín mine tailings is related to the experimental metallurgical works previously cited (Section 2). Significant Hg values were measured in Monte Romero mine related to the formation of a replacive mineralization. Pb (up to 21,130 μg g<sup>−</sup><sup>1</sup> ) and Zn (41,841 μg g<sup>−</sup><sup>1</sup> ) contents in the tailings from Mazarrón district (**Table 3**) as well as the significant Ag content from San Cristóbal mine related to the exploitation of Ag-bearing galena deserve special mention.

The Mina Concepción samples were collected with a manual sampler from the first meter in depth. That is the reason for the lower metal contents to be associated with the more recent and efficient metallurgical works. Related to the Iberian Pyrite Belt district, relevant variations as a function of depth were identified in all of the analyzed element contents from Monte Romero samples. Possible explanations for these variations could be argued: (a) periods with higher mineral benefit, due to improvements in metallurgic processes or to a higher grade mineralogy and (b) a change in the exploitation targets, originally focused on galena (Pb) mining but later re-directed to pyrite (Fe) and sphalerite (Zn) mining due to environmental policies that do not recommend the use of lead in many industrial fields.

#### *4.2.2 Sediments and soils*

Total ferric iron, S and trace element concentrations, and pH values from colluvial and watercourse sediment, and soil samples of the Alcudia Valley and Mazarrón districts are summarized in **Table 4**.


*Fe*

**97**

was 157–16,193 μg g<sup>−</sup><sup>1</sup>

*Geoenvironmental Characterization of Sulfide Mine Tailings*

**Alcudia Valley Mazarrón**

**Sample Colluvial Soil Blank Sediment Sediment** Ag 0–3 (2) 0–3 (1) 0.2 21–60 (38) 0–7 (3) As 8–24 (17) b.d.-26 (15) 11 216–312 (259) 15–131 (33) Cd 1–7 (3) b.d.-7 (b.d.) b.d. 2–4 (3) 1–6 (3) Cu 38–196 (76) 5–39 (17) 18 70–122 (96) 45–482 (177) Fe2O3 total 5.3–9.5 (6.9) 1.7–4.7 (3.5) 4.2 7.6–33.5 (18.3) 4.0–12.0 (5.9) Ni 46–93 (59) 13–46 (34) 30 10–14 (12) 30–61 (47)

S 0–0.2 (0.1) 0–0.3 (0.1) 0.01 2.7–4.5 (3.9) 0.1–3.0 (1.0) Sb 5–40 (24) 2–30 (9) 2 98–124 (111) 2–48 (14) Sn 3–5 (4) 2–3 (3) 2 5–10 (7) 2–6 (4)

pH n.a. 5.7–6.2 (5.9) 5.1 3–3.4 (3.2) 7.0–7.7 (7.4) *Ag, As, Au, Cd, Cu, Ni, Pb, Sb, Sn, and Zn in μg/g. Fe2O3 and S in wt%. Mean in brackets. b.d.: below detection.* 

*Fe2O3 total, trace element content, and pH values in the studied colluvial, soil, and watercourse sediment samples.*

(318)

34–1180 (335)

**San Quintín San Cristóbal Las Moreras**

34 9395–16,193

(12,800)

49 815–1660 (1334) 452–10,693 (2907)

157–1880 (555)

The highest contents were found in the pond samples, and the intermediate contents in the colluvial samples from San Quintín area. The ponds were not waterproofed, and hazardous metals from the upper ponds have percolated through the underlying colluvial sediments. Cu, Pb, and Zn contents show significant amounts. Five representative soil samples were analyzed in order to determine the importance of contamination (**Table 4**). Two mine soil samples show similar metal and As content to the upper tailing samples. The other two were agricultural soil samples, showing significantly lower metal and As content, but higher Hg and Pb contents than the local background sample (blank in **Table 4**), collected from an agricultural soil 4.5 km to the south-east. However, remarkably high As, Pb, and Zn contents were still found in this background sample, suggesting that the surrounding agricultural soils are also contaminated. In fact, Ag, Cd, Pb, and Zn contents from agricultural soil samples are

higher than geochemical baselines reported by [22] for this Spanish region.

In Mazarrón district, both tailings and watercourse sediments showed high amounts of potentially toxic elements, slightly lower at the sedimentary level (3.0–5.5 m depth). The total iron content ranged between 4.0 and 33.5 wt%, Pb

(**Table 4**). Other trace elements that displayed high values were: As, Cu, and Sb. The sediments mark a defined geochemical limit with the tailing unit. The upper mine tailings are significantly concentrated in Fe2O3total and heavy metals, whereas the sediments display marked lower values. This decrease is not absolutely regular, with major peaks in Cu and Zn contents, and minor increases in As, Cu, Fe2O3total, Pb, and Zn. The amount of calcite in the Las Moreras sedimentary unit (**Table 2**) controls the pH, buffering to within a small range of 7.2–7.7 (**Table 4**). In turn, the

, and the Zn content ranged between 815 and 10,693 μg g<sup>−</sup><sup>1</sup>

*DOI: http://dx.doi.org/10.5772/intechopen.84795*

Pb 79–577 (315) 41–1110

(503)

Zn 186–844

*n.a.: not analyzed.*

**Table 4.**

**Mine district**

**Study mine**


*Geoenvironmental Characterization of Sulfide Mine Tailings DOI: http://dx.doi.org/10.5772/intechopen.84795*

*Ag, As, Au, Cd, Cu, Ni, Pb, Sb, Sn, and Zn in μg/g. Fe2O3 and S in wt%. Mean in brackets. b.d.: below detection. n.a.: not analyzed.*

#### **Table 4.**

*Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques…*

**96**

**Mine district**

**Study** 

**LN**

**MR**

**MC**

**BR**

**SQ**

**SC**

**LM**

**area**

Ag As Au Cd Cu

Fe

Ni Pb

S Sb Sn Zn pH

2.8–3.5 (3.2) *Ag, As, Au, Cd, Cu, Ni, Pb, Sb, Sn, and Zn in μg/g. Fe*

*(BR), San Quintín (SQ*

**Table 3.**

*Fe*

*O2*

*3 total, trace element content, and pH values in the studied tailings.*

50–260 (143)

0.5–6.9 (4) 2.5–3.2 (3.0)

*O2* *), San Cristóbal (SC), and Las Moreras (LM).*

n.a.

2.4–3.7 (3.0)

n.a. *3total and S in wt%. Mean in brackets. b.d.: below detection; n.a.: not analyzed. La Naya (LN), Monterromero (MR), Mina Concepción (MC), Brunita* 

2.2–3.6 (2.5)

2.8–5.6 (4.0)

200–970 (511)

2020–2112,150 (6315)

1250–4470 (2418)

2500–11,405 (4101)

12,810–41,841 (27,738)

b.d.

b.d.

b.d.

31.3–50.4 (35.2)

168–861 (338)

16.2–67.5 (40)

3–54 (30) 14–244 (76)

3–7 (5)

8–121 (83)

n.a.

n.a.

n.a.

3.8–19.1 (11.8)

0.3–1.0 (0.4)

36–162 (79)

108- > 200 (149)

54–136 (93)

24–37 (30)

3.5–53.0 (6.6)

7.1–12.8 (9.3)

51–222 (133)

295–12,610 (4615)

71–475 (264)

1610–5950 (3211)

1510–10,500

5987–39,877 (21,130)

3940–5239 (4665)

(3992)

b.d.

b.d.

b.d.

O2 3 total

8.51–14.1 (11.5)

2.12–27.2 (14.57)

6.11–24.1 (14)

22.3–52.6 (38.7)

11–40 (22)

4.5–6.3 (5.6)

29–61 (44)

11–41 (21)

9.8–22.9 (19.2)

306–4511 (998)

914–16,582 (4874)

n.a.

n.a.

n.a.

n.a.

49–100 (70)

191–909 (472)

1110–2740 (1650)

311–744 (558)

22–86 (53)

n.a. 3–67 (22) 76–323 (179)

5–22 (13) 42–381 (171)

121–882 (406)

4–833 (110)

n.a.

n.a.

n.a.

97–373 (186)

168–356 (230)

17.7–28.5 (23.7)

41–59 (49)

223–1080 (613)

39–385 (195)

b.d.

31–81 (48)

b.d.

2–8 (4)

5–29 (12) 16–54 (28)

400–633 (490)

20- > 100 (55)

14–26 (20)

181–630 (366)

**Iberian Pyrite Belt**

**Cartagena-La Unión**

**Alcudia Valley**

**Mazarrón**

*Fe2O3 total, trace element content, and pH values in the studied colluvial, soil, and watercourse sediment samples.*

The highest contents were found in the pond samples, and the intermediate contents in the colluvial samples from San Quintín area. The ponds were not waterproofed, and hazardous metals from the upper ponds have percolated through the underlying colluvial sediments. Cu, Pb, and Zn contents show significant amounts. Five representative soil samples were analyzed in order to determine the importance of contamination (**Table 4**). Two mine soil samples show similar metal and As content to the upper tailing samples. The other two were agricultural soil samples, showing significantly lower metal and As content, but higher Hg and Pb contents than the local background sample (blank in **Table 4**), collected from an agricultural soil 4.5 km to the south-east. However, remarkably high As, Pb, and Zn contents were still found in this background sample, suggesting that the surrounding agricultural soils are also contaminated. In fact, Ag, Cd, Pb, and Zn contents from agricultural soil samples are higher than geochemical baselines reported by [22] for this Spanish region.

In Mazarrón district, both tailings and watercourse sediments showed high amounts of potentially toxic elements, slightly lower at the sedimentary level (3.0–5.5 m depth). The total iron content ranged between 4.0 and 33.5 wt%, Pb was 157–16,193 μg g<sup>−</sup><sup>1</sup> , and the Zn content ranged between 815 and 10,693 μg g<sup>−</sup><sup>1</sup> (**Table 4**). Other trace elements that displayed high values were: As, Cu, and Sb. The sediments mark a defined geochemical limit with the tailing unit. The upper mine tailings are significantly concentrated in Fe2O3total and heavy metals, whereas the sediments display marked lower values. This decrease is not absolutely regular, with major peaks in Cu and Zn contents, and minor increases in As, Cu, Fe2O3total, Pb, and Zn. The amount of calcite in the Las Moreras sedimentary unit (**Table 2**) controls the pH, buffering to within a small range of 7.2–7.7 (**Table 4**). In turn, the


*Values in μg/L. b.d.: below detection. Mina Concepción (MC), Brunita (BR), San Quintín (SQ ), San Cristóbal (SC), and Las Moreras (LM). LK: leakage; WT: water table; BO: borehole; AMD: acid mine drainage; and WC: watercourse.*

#### **Table 5.**

*Fe2O3 total, trace element content, and pH values in the water samples.*

upper tailing unit of Las Moreras shows much lower pH values (2.8–5.6), due to the sulfide content and the complete absence of calcite.

#### *4.2.3 Waters*

The composition of leakage sample waters of a restored mine pond (Mina Concepción) indicates that these waters represent acid mine drainage, as reflected by their very low pH (<2.6) (**Table 5**). Trace element contents are very high for Cu and Zn (>2 mg/l), both higher than the EPA's maximum recommended limits for irrigation waters (0.2 mg/l for Cu and 2 mg/l for Zn [23]). This is also the case for As in samples leaking from the dyke wall and the puddle. Lead also goes beyond the legislation limits in samples from the dyke wall and the drainage pipes. Acid mine drainage was observed in the northern part of the Brunita mine pond (pH < 2.4) (**Table 5**). The concentrations were very high for Cu, Zn, Cd, Ni, and Fe in the water sample. Results from complementary techniques (ERT), shown in Section 4.3 of this chapter, have confirmed the formation of AMD waters in Mina Concepción and Brunita mines.

One water sample was collected at 8 m depth in the borehole from San Quintín mine (**Table 5**). The high EC and acidic pH values are consistent with water from ore deposits retained in tailing ponds. Three samples showing low pH and significantly high trace element contents indicate AMD flowing from the remaining tailings. AMD was not observed in samples from the watercourse crossing the mining zone (**Table 5**). pH values in these waters are circumneutral, and EC values and metal contents are significantly lower than in samples from the tailings. Samples collected up- and downstream display the lowest trace element contents. Higher metal contents have been measured in the rest of watercourse samples, denoting that trace element contamination occurs through the mining area.

With regard to the San Cristóbal mine pond, AMD was clearly detected in the water sample: pH < 2, high redox potential, high EC, and Total dissolved salt values. Concentrations of trace elements were very high for As and Cu (>2000 μg/L), Zn

**99**

**Figure 3.**

*values. Modified from Martín-Crespo et al. [6].*

*Geoenvironmental Characterization of Sulfide Mine Tailings*

(>2500 μg/L), Cd and Ni (>5600 μg/L), and Fe (>100,000 μg/L). Water from the seasonal watercourse of Las Moreras was also analyzed. Significant contents of metallic elements (Cu, Fe, Ni, and Zn) were measured, all beyond the established

A singular case occurs in San Quintín mine where significantly high Hg content has been identified in the mine area. Gaseous Hg emissions were measured from the tailings and surrounding soils (**Figure 3**). The total gaseous mercury distribution in the studied area significantly changes between summer and winter. The area

Don Quixote Route in summer. TGM values are lower than the limit recommended for the general population by the World Health Organization (WHO) (1000 ng m<sup>−</sup><sup>3</sup>

for the worst scenario [24]: higher temperature and solar radiation during summer.

Multivariate analysis has been carried out on the significant metal contents from samples of tailings (Brunita), tailings + colluvial sediments (San Quintín), and tailings + watercourse sediments + bedrock (San Cristóbal and Las Moreras) (**Figure 4**). Statistical data processing was carried out using Minitab® 16 software. The multivariate analysis was based on clustering (group average linkage dendrograms, Euclidean distance) of the set of samples and significant trace elements (Ag, As, Cd, Cu, Pb, Sb, Sn, and Zn). The dendrogram of the metals and As in the Brunita tailing samples shows the metallic signature of the district ores: Ag-Pb-Cd-Zn, Cu, and As-Sb-Sn, with As being mainly related to Sb (tetrahedritetenanntite mineral group). Ag-Pb-Cd-Zn signature is clearly defined due to the mineral source. In the case of San Quintín, the dendrogram from tailings and colluvial sediments reflects again the metallic signature of the district (Pb-Ag-Sb, Cu, and Zn-Cd to a certain extent [13]), with As mainly related to Sb (bournonite and boulangerite) and Pb-Ag (galena). Some samples display a strong affinity to the Ag-Pb-Sb-As association, whereas other samples display Cd-Zn affinity. The same

*Total gaseous mercury (TGM) seasonal distribution in the San Quintín area: (a) summer and (b) winter* 

is restricted to the surroundings of the

, and extends into the

)

*DOI: http://dx.doi.org/10.5772/intechopen.84795*

affected by TGM values up to 100 ng m<sup>−</sup><sup>3</sup>

cinnabar stockpile in winter, but the affected area is 0.16 km2

limits for irrigation waters.

*4.2.5 Multivariate analysis*

*4.2.4 Hg in air*

(>2500 μg/L), Cd and Ni (>5600 μg/L), and Fe (>100,000 μg/L). Water from the seasonal watercourse of Las Moreras was also analyzed. Significant contents of metallic elements (Cu, Fe, Ni, and Zn) were measured, all beyond the established limits for irrigation waters.
