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Heavy metal toxicity has become a global concern due to the ever-increasing contamination of soil, water and crops. Until recent decades little has been known about the remediation of mining sites using spontaneous plants in Latin America. Soil and plant samples were taken in Peru, at a polymetallic mine (mainly silver, lead and copper) in Cajamarca Province, Hualgayoc district. Top soils (0–20 cm) were analyzed for physical and chemical properties by standard methods. Total Pb and Zn concentrations in top soils were determined by ICP-OES. Similar metals in plants were analyzed separately (aerial and root system). Ti content was used as an indicator for contamination of plant samples with soil particles. Translocation Factor (TF) and Shoot Accumulation Factor (SAF) were determined to assess the tolerance strategies developed by these species and to evaluate their potential for phytoremediation purposes. The non polluted soils had near neutral pH (6.8 ± 0.1), a great content of organic carbon (42 ± 4.0 g kg − 1 ) and a silt loamy texture. According to the total metal concentrations, the polluted soils exceeded toxicity thresholds; large Pb (13,105 ± 3147 mg Pb kg − 1 ) and Zn (28,393 ± 3458 mg Zn kg − 1 ) concentrations were detected. Unusually elevated concentrations of these metals were detected in roots of Bidens triplinervia L. (e.g. up to 5180 mg Pb kg − 1 and 9900 mg Zn kg − 1 ) while Senecio sp. accumulated more heavy metals in shoots (e.g. up to 4250 mg Pb kg − 1 and 3870 mg Zn kg − 1 ). The TF values were B. triplinervia and > 1 in Senecio sp., while the SAF were B. triplinervia can be considered potentially useful for phytostabilization due to its capacity to restrict the accumulation of elevated amounts of Pb and Zn to the roots, while Senecio sp. could be utilized for phytoextraction technologies. Moreover, these plants showed an elevated transfer factor and grew in the presence of other toxic metals. The present study, to the best of our knowledge, is the first report on the metal accumulation in roots of B. triplinervia and provides a pioneer contribution to the very small volume of data available on the potential use of native plant species from contaminated sites in phytostabilization and phytoremediation technologies.

Metal mining gives access to very important resources but contributes to severe and diverse environmental problems. Until recently, little has been known about the remediation of mining sites in Latin America using metallophytes. The present study was designed to identify and characterize spontaneously growing heavy metal tolerant plant species in the area around the polymetallic Carolina mine in Hualgayoc (Cajamarca, Peru). The aim was to find species that are potentially useful for phytoremediation. Plants and soils were sampled and analysed for concentrations of As, Fe, Mn, Pb, Zn and Ti. The Translocation Factor (TF) and the Bioaccumulation Factor (BF) were determined and used to measure the amount of each element accumulated in shoots and roots of each plant species. The top soil had a neutral pH (7.4 ± 0.5), an organic carbon content of 24 ± 11 g kg− 1 and a loam texture. According to the total metal concentrations, all samples exceeded soil toxicity thresholds. Indeed, high Pb (from 120 to 111,290 mg kg− 1) and Zn (from 380 to 46,500 mg kg− 1) concentrations were detected in all soil samples. In plants, great Pb and Zn concentrations were found in the shoots of Plantago orbignyana Steinheil (from 6070 to 8240 mg Pb kg− 1 and from 8290 to 11,560 mg Zn kg− 1), Lepidium bipinnatifidum Desv. (from 6300 to 7240 mg Pb kg− 1 and from 4610 to 5370 mg Zn kg− 1), Baccharis latifolia Ruiz & Pav Pers. (from 2120 to 3060 mg Pb kg− 1 and from 1090 to 1490 mg Zn kg− 1), and Sonchus oleraceus L. (from 2180 to 2900 mg Pb kg− 1 and from 1340 to 1910 mg Zn kg− 1). The great TFs indicate that these plant species effectively translocate metals. L. bipinnatifidum shows the greatest TF values (i.e., 143 for Pb and 21.5 for Zn). These species could have potential for phytoextraction due to their large capacity to uptake and transfer elements, and their ability to grow in the presence of other toxic metals. To the best of our knowledge, the present study is the first report describing the metal accumulation ability of these plant species.

This study determines extractable levels of Cd, Cu, Pb, Zn, Ni and Co in western Almeria (Spain) greenhouse surface soil horizons using EDTA solution, which is identified as the fraction available for organisms and plants. It also establishes background levels, geochemical baseline concentration and reference values (RV), and investigates the possible relationships between soil properties and elemental concentrations. The results show that the soil concentration of these extractable heavy metals was high as those reported by other authors for Spanish agricultural soils. The available RV concentrations obtained (mg kg −1 ) were: Cd 0.17, Cu 1.6, Pb 13.8, Zn 5.0 Ni 1.7 and Co 2.9. Using the upper baseline criterion, 95% of greenhouse soils present a relatively higher content of extractable heavy metals given their Cd and Cu concentration. Significant correlations between total and EDTA-extractable metal levels were found for Zn, Pb, Cu, Cd and Ni. Soil properties also related to heavy metals content, suggesting that Cd, Cu, Pb and Zn are of similar origin and relate to anthropic activities, and implies the same interactions and/or relationships among these metals.

The study of metal contents in industrial, agricultural or/and polluted soils compared with natural or unpolluted soils is currently necessary to obtain reference values and to assess soil contamination. Nonetheless, very few works published appear in international journals on elements like Se, Li and Sr in Spanish soils. This study determines the total levels of Se, Li, Sr, As, Cd, Co, Cr, Cu, Ni, Pb, V, Zn, Fe, Mn and Ba in 14 natural (unpolluted) soils (Gypsisols, Leptosols, Arenosols and Acrisols), 14 agricultural soils (Anthrosols, Fluvisols and Luvisols), and 4 industrial–urban affected-surface soil horizons (Anthrosols and Fluvisols) of Eastern Spain. The geochemical baseline concentrations (GBC) and reference values (RV) have been established, and the relationships among elements and also between soil properties and elemental concentrations have been analysed. The RV obtained in this study were (mg kg −1 ): Se 2.68, Li 115, Sr 298, Cd 0.97, Co 35, Cr 217, Cu 46, Ni 50, Pb 137, V 120, Zn 246, Fe 124,472, Mn 2691, and Ba 743. The RV for Se and Li were used as a preliminary approach to assess soil contamination in Spanish soils. The results confirm human impact on Sr, As, Cd, Cr, Cu, Ni, Pb and Zn soil concentrations, but evidence no deviation from natural Se, Li, Co, V, Fe, Mn and Ba concentrations. The results obtained from the statistical analysis reveal significant correlations between some elements and clay and soil organic matter (SOM) contents, indicating that metal concentrations are controlled by soil composition. One particularly interesting finding is the high correlation coefficients obtained between SOM and Se, Cd, Cr, V, Fe, and Mn, and between clay and Cd, Zn, V, Fe and Mn. Once again, these facts confirm the role of SOM and clay minerals in soil functions and that soil is an ecosystem element responsible for maintaining environmental quality.