Results And Discussion

Six metals were analyzed in all soil samples (Table 26.1). High levels of Pb, Zn, As, and W were recorded in the soils. The Pb in the soil was very high, reaching a maximum of 2497.2 ppm in the collected samples. The maximum Zn content in soils was 3599.6 ppm, a level that can be extremely toxic for plants. Maximum concentration of As in soils was 469.5 ppm. Soil content of W was also high, reaching a maximum of 230.7 ppm. The maximum concentrations of Cu and Bi in soils were 356.7 ppm and 2.74 ppm, respectively.

A total of 95 plant species from 37 families were investigated for their ability to accumulate metals in these mine complexes (Table 26.1). Analysis of metals performed in plant material (aerial parts, leaf, needles, fruit, flower, phyllode, root, seed, and twig) indicated that a variable degree of accumulation of metals was present in different plant parts (Table 26.1). The most representative family is Fabaceae with 11 species, followed by Asteraceae with 9 species, Cistaceae with 7, Lamiaceae with 6, Caryophyllaceae with 5, Poaceae with 5, Rosaceae with 5, Scrophulariaceae with 4, Polygonaceae with 4, Fagaceae with 4, Cyperaceae with 3, and the rest with 1 or 2.

Lead concentration in plants was rather high for some species (Figure 26.1), varying from 0.71 ppm in leaves of Salix atrocinera and 1.03 ppm in leaves of Eucalyptus globulus to 157.8 ppm in roots and 97 ppm in the aerial parts of Typha dominguensis. In the aerial parts of another Poacea, Briza maxima, lead content of 97.02 ppm was recorded. Myriophyllum alterniflorum also showed high content of Pb in the whole plant, with 93.76 ppm (Figure 26.1). This aquatic species also accumulated Zn in the above-ground tissues, demonstrating its capacity to take up toxic metals from soil (Table 26.1). In Andryala integrifolia, a frequent species in other mining areas (unpublished data), a content of 77.02 ppm of lead in the above-ground tissue was recorded. This frequent finding of common species in diverse mining areas with distinct paragenesis is worth pointing out because metals and other environmental stress factors play a critical role. Ecological convergence seems clear in this particularly hard environment.

Other species that showed high content of Pb (Figure 26.1) were Ononis cintrana (65.69 ppm), Lotus corniculatus L. var. corniculatus (62.6), Elatine macropoda (62.5), Daphne gnidium (59.47), Digitalis thapsi (55.89), Dittrichia viscosa (37.08), Pterospartum tridentatum (38.6), Ludwigia palustris (35.1), and Phlomis lychnitis (29.8).

With respect to As, the aquatic species Elatine macropoda showed a remarkable content of As in the above-ground tissues: 531.4 ppm (Figure 26.2). This species also accumulated high levels of Pb (62.5 ppm), Co (127.8 ppm), and Zn (2258.5 ppm) (Table 26.1). The aquatics Typha dominguensis and Myriophyllum alterniflorum, with 16.97 and 10 ppm of As, respectively, again were among the plants accumulating more As. These two species also showed high content of zinc in the whole plant: 389.7 ppm in T. dominguensis and 507.83 ppm in M. alterniflorum. Other species that showed high content of As (Figure 26.2) were Adenocarpus complicatus (12.9 ppm), Asparagus acutifolius (19.62), Galium palustre (11.98), and Lactuca viminea (11.64).

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