Lourdes Rufo

Heavy Metal Content in Erica andevalensis: An Endemic Plant from the Extreme Acidic Environment of Tinto River and its Soils

The Tinto River (Huelva, Spain) constitutes a complex and singular system characterized by extreme acidity and high concentrations of iron and other metals (Cu, Co, Mn, Zn, Pb, As) of its soils and waters. Traditional mining activity and the resulting intensive deforestation have eliminated its natural vegetation. Communities of the endemic Erica andevalensis colonize the fluvial terraces of the mining areas of the Tinto River, from drier to more humid soils, reaching its optimum in the proximity of rivers and streams. Concentrations of 22 (S, K, Ca, Mn, Fe, Co, Ni, Cu, Zn, As, Pb, Sr, Cr, Na, Mg, Al, Sc, Ti, Rb, Cd, Ba, Hg) elements have been determined for soils and E. andevalensis specimens at several points near the origin of the river. Erica andevalensis shows a remarkable capacity to survive with meager quantities of nutrients and an extraordinary tolerance to high concentrations of heavy metals. However, this heath does not show a lack of nutrients (Ca: 2012–5942 ppm; K: 223–3771 ppm; Mg: 883–2566 ppm) nor an excess of metals in its tissues (Fe: 73–514 ppm; Cu: 9–16 ppm; Co: ND–2 ppm). These abilities make E. andevalensis an ideal candidate for revegetation of mining areas and phytostabilization of heavy metal contaminated soils. These characteristics together with the exclusive extreme habitat on which E. andevalensis grows, make it possible to classify it as a metal bioindicator, e.g., for Cu.

Metal accumulation screening of the Río Tinto flora (Huelva, Spain).

Río Tinto (Huelva, Spain) is located in one of the most important mining regions in the world. Its soils are characterized by their extreme acidity and elevated concentrations of heavy metals. Due to these characteristics, the Tinto ecosystem is considered unique and an ideal location to study biological adaptations to this type of habitat. Plant species that present these adaptations might be useful to mining and other metal pollution restoration programs. This study reports the results for the screening of Ca, Mg, Na, Mn, Fe, Ni, Cu, Zn, As, and Pb in aerial tissues of 97 plant species from the Tinto basin flora. In addition, plant–soil relationships were analyzed using the biological absorption coefficient (BAC) to detect the main plant adaptations in the Tinto flora. The species selected are representative of the biomass of the main dominant edaphophile and climatophile vegetation communities of the three river sections, forest, and subseral stages. Plant and soil elemental analyses were performed using inductively coupled plasma–mass spectrometry technique (ICP-MS). The results indicate that in general, Tinto flora shows a pattern of accumulation of the analyzed elements in aerial tissues which agrees with the nutritional requirements of vascular plants (macronutrients > micronutrients > indifferent or toxic elements). Among macronutrients, Ca seems to be an essential element in this habitat. This element accumulates in the aerial plant tissues. Basically, the Río Tinto flora is made of Fe, Cu, Zn, Ni, As, and Pb excluders, although some analyzed species of Erica, Quercus, Lavandula, Cistus, Genista, and Cytisus genera can be considered Mn accumulators. The results of this study make up a body of fundamental knowledge of the strategies used by plants to thrive in habitats with high concentrations of toxic heavy metals. This information is vital when it comes to planning a restoration program. Plants must be selected and used according to the requirements, always respecting the characteristics of the territory and facilitating the development of suitable vegetation.

An Improved Semiquantitative Method for Elemental Analysis of Plants Using Inductive Coupled Plasma Mass Spectrometry

A semiquantitative ICP-MS method suitable for evaluating metal content in plants exposed to high metal concentrations is described. The methodology which has been tested using different plant reference material is able, in only a few minutes, to obtain qualitative and quantitative information from the sample. Recoveries close to 100% were obtained for more than half of the referenced elements with an RSD <10%, thus avoiding the generation of a calibration line for each of the elements to be analyzed. The use of multi-standards improves the results obtained with conventional standards by a factor of two. In these conditions the semiquantitative multi-elemental analysis is a valid alternative for most of the analyzed elements with the exception of Si, Al, and P which requires the use of a quantitative ICP-MS analysis for its determination. Two different digestion protocols were tested, with and without the addition of HF to the HNO3 + H2O2 extraction mixture. Similar results were obtained for poplar and bush reference materials using the HNO3 + H2O2 mixture. The addition of HF did not improve the recovery of different elements, in general, but is critical for the quantitative measurements of Al and Si as its presence allows results to be obtained with an RDS <5%.

Nickel distribution in the hyperaccumulator Alyssum serpyllifolium Desf. spp. from the Iberian Peninsula

Abstract The relative concentration and distribution of nickel (Ni) in vegetative tissues (leaves, stems and trichomes) and reproductive organs (seeds) was studied using energy-dispersive X-ray microanalysis (EDXS) and scanning electron microscopy (SEM) in two previously studied Ni-hyperaccumulator subspecies of Alyssum serpyllifolium Desf. growing naturally in ultramafic soils of the Iberian Peninsula: A. serpyllifolium ssp. lusitanicum Dudley & P. Silva and A. serpyllifolium ssp. malacitanum Rivas Goday ex G. López. Both taxa showed that Ni accumulates preferentially in the leaves, exhibiting a homogeneous distribution on both epidermis surfaces. The highest Ni concentrations were found inside the epidermal cells and at the base of trichome stalks. Ni accumulation in seeds was lower than in the vegetative organs. The location of Ni in these plants allows us to postulate that its accumulation is a protection mechanism against external stress.

Nickel localization in tissues of different hyperaccumulator species of Euphorbiaceae from ultramafic areas of Cuba

Pantropical species of the genera Phyllanthus and Euphorbia and the Cuban endemic genus Leucocroton from the Euphorbiaceae family, were selected for nickel localization microanalysis. Scanning Electron Microscopy coupled with Energy Dispersive X-ray Microanalysis (SEM-EDX) was used for qualitative detection of nickel in the selected Ni-hyperaccumulator species: Euphorbia helenae, Leucocroton linearifolius, L. flavicans Phyllanthus orbicularis, P. discolor and P. xpallidus, all collected from Cuban ultramafic soils. The leaves and stems from the Euphorbiaceae species analyzed were the organs with higher nickel accumulation. Elemental mapping of leaves and stem tissues from these species have been compared. The highest Ni concentrations were found in the laticifer tubes of stems and the epidermis tissues of leaves in all the analyzed species, suggesting a general pattern of the Euphorbiaceae family for nickel accumulation. The high nickel concentrations and its rather homogeneous distribution found in leaves of these Ni-hyperaccumulating plants suggest a possible role in protection mechanisms against environmental stress, such as UV irradiation.

A micromorphological and phylogenetic study of Sarcocornia A.J. Scott (Chenopodiaceae) on the Iberian Peninsula

This study presents a comprehensive revision of the genus Sarcocornia (Chenopodiaceae) on the Iberian Peninsula based on macromorphological, micromorphological and phylogenetic data, and considering caryological, ecological and biogeographical information. Three species of Sarcocornia have been identified on the Iberian Peninsula: Sarcocornia perennis (Miller) A.J. Scott, Sarcocornia fruticosa (L.) A.J. Scott and Sarcocornia alpini (Lag.) Rivas-Martínez. Several authors have proposed that S. alpini is a specific and subspecific rank of S. perennis. Fuente, Rufo and Sánchez-Mata have recently described a new species, Sarcocornia hispanica. The micromorphological and molecular studies (sequence of the internal transcribed spacer region) indicate that there is a broad diversity within Sarcocornia in the Western Mediterranean. This article proposes a new species (Sarcocornia pruinosa) and subspecies (S. alpini subsp. carinata) in view of the new data.

Successional Dynamics of the Climatophile Vegetation of the Mining Territory of the Río Tinto Basin (Huelva, Spain): Soil Characteristics and Implications for Phytoremediation

This study deals with plant communities of the mining area of the Río Tinto basin, their relationship with the environment, specifically their soils, and their successional processes. The vegetation was studied by phytosociological methods. The results reveal that current vegetation of the Río Tinto mining area is mainly composed of ten plant communities that present a progressive and regressive sequence that constitutes a vegetation series. The mining actions in the area have led to the loss of the original soils and to a fast regression of the vegetation to the first colonizer stages. This regressive process entails a loss of diversity and a change in the Raunkiers life-form spectrum. Soil physical and chemical analysis showed that the progressive processes of the vegetation involve an evolution of the soils, which tend to reduce their acidity and toxic metal concentration and to enrich in phyllosilicates. The results obtained give an overview of the potential vegetation that should exist in this territory. They allow the establishment of restoration programs in the mine tailored to the existing substrates and the native vegetation, favoring the conservation of both endemic species and plant communities in the region.

Metal uptake and distribution in cultured seedlings of Nerium oleander L. (Apocynaceae) from the Río Tinto (Huelva, Spain).

Nerium oleander L. (Apocynaceae) is a micro-nano phanerophyte that grows in the riverbanks of the Río Tinto basin (Southwest Iberian Peninsula). The waters and soils of the Río Tinto area are highly acidic and have high concentrations of heavy metals. In this environment, N. oleander naturally grows in both extreme acidic (EA) and less extreme acidic (LEA) water courses, excluding, and bioindicating certain metals. In this work, we compared and evaluated the accumulation preferences and capacities, the distribution and processes of biomineralization of metals (Fe, Cu, Zn, Mn, Mg, Ca) in the first stages of growth of EA and LEA oleanders by means of inductively coupled plasma–mass spectrometry, scanning electron microscopy, and energy dispersive X-ray analyzer analysis. Seeds from both environments were grown and treated with a self-made solution simulating the most extreme red waters from the Río Tinto. LEA plants drastically reduces the metal uptake at the beginning, but later reactivates the uptake reaching concentration values in the same range as the EA plants. The results showed high Mn, Zn and Mg concentrations, accumulation of Fe and Cu in plants from both environments, differing from the metal concentrations of field-grown oleanders. Iron bioformations with traces of other metals were present inside and over epidermal cells and inside vascular cells of stems and roots. They were absent of leaves. The accumulation properties of N. oleander in its early stages of development make it a species to take in consideration in phytoremediation processes but optimized conditions are needed to ensure enough biomass production.

Saxifraga gemmulosa Boiss. (Saxifragaceae), an Endemic Nickel Bioindicator from Ultramafic Areas of the Southern Iberian Peninsula

Abstract The western Betic Mountain Range contains the largest ultramafic rock area in the Iberian Peninsula. The predominant flora of this southern territory (over two hundred taxa) was screened for Ni accumulation. Only two species showed important concentrations of Ni in their tissues, Alyssum serpyllifolium subsp. malacitanum (Brassicaceae), a Ni hyperaccumulator, and Saxifraga gemmulosa (Saxifragaceae). Saxifraga gemmulosa is a rare endemic species restricted to the ultramafic outcrops of Málaga (South Spain), mainly growing in basic or ultrabasic rock crevices, where it appears with other serpentinophytes such as Asplenium adiantum-nigrum subsp. corunnense (Aspleniaceae). Nickel and other representative elements present in Saxifraga gemmulosa and its soils from Sierra Bermeja (Málaga) were studied by inductively coupled plasma-mass spectrometry (ICP-MS). The structures of the plant were micromorphologically analysed by scanning electron microscopy (SEM) coupled to an Energy-Dispersive X-Ray Probe (EDX). The results showed the Ni hyperaccumulating characteristics of S. gemmulosa. As observed in other Ni hyperaccumulator plants, accumulation was mainly detected in leaf epidermis.

Pollen morphology and localization of Ni in some Ni-hyperaccumulator taxa of Alyssum L. (Brassicaceae)

Pollen morphology of seven Alyssum L. taxa growing on serpentine soils in different places in the European Mediterranean macrobioclimate territory were studied, described and compared. Cluster analysis was performed to show similarity between species and their populations. The shape of the pollen grains varies among the species and among the grains within the same anther. The pollen grains are 3-colpate, prolate, with long and narrow colpi reaching the poles. The ornamentation of the exine varies from micro-reticulate to reticulate between the species. Pollen sterility/fertility was also calculated. The highest percentage of sterile pollen (73.76%) was calculated for Alyssum murale subsp. murale and the lowest (9.54%) for A. bertolonii subsp. bertolonii. All species are representatives of sect. Odontarrhena (C.A. Meyer) Koch well known as Ni-hyperaccumulators. Nickel and other elements present in pollen and stamen were studied by inductively coupled plasma-mass spectrometry. The stamen parts of all species were micromorphologically analyzed by scanning electron microscopy coupled to an energy-dispersive X-ray probe. Accumulation of Ni was detected in the stamens of all studied species and rarely in the pollen grains. The distribution patterns of Ni were similar among the species examined.