Erika S. Santos

Inter-population variation on the accumulation and translocation of potentially harmful chemical elements in Cistus ladanifer L. from Brancanes, Caveira, Chança, Lousal, Neves Corvo and São Domingos mines in the Portuguese Iberian Pyrite Belt

PurposeThis study aimed to compare the variation on the accumulation and translocation of potentially harmful chemical elements and nutrients (As, Ca, Cu, Fe, K, Mg, Mn, Ni, Pb and Zn) in Cistus ladanifer L. belonging to populations growing in different mine areas from the Portuguese Iberian Pyrite Belt (Brancanes, Caveira, Chança, Lousal, Neves Corvo, São Domingos). These mines are abandoned (except Neves Corvo that is still operating) and have different contamination levels.Materials and methodsComposite samples of soils (n = 31), developed on different mine wastes and/or host rock, and C. ladanifer plants (roots and shoots) were collected in the mine areas. Soils were characterized for pH, NPK and organic C, by classical methodologies. Soils (total fraction—four acid digestion, and available fraction—extracted with aqueous solution of diluted organic acids, simulating rizosphere conditions) and plants (ashing followed by acid digestion) elemental concentrations were determined by ICP. Soil–plant transfer and translocation coefficients were calculated. Principal components analysis in both ways, the classical method and a second approach with adaptations used mostly in multivariate statistical processes control data, were done in order to compare the plants populations.Results and discussionSoils had large heterogeneity in their characteristics. Caveira, Lousal, Neves Corvo and São Domingos soils showed the highest total concentrations of As, Cu, Pb and Zn. Independently of the mine, available fractions of elements were low. Intra- and inter-population variations in accumulation and translocation of elements were evaluated. Plants were not accumulators of the majority of the analysed elements. Nutrients were mainly translocated from roots to shoots, while trace elements were stored in roots (except in Neves Corvo for As and Pb, and São Domingos for As). Elements concentrations in plant populations from Lousal, Chança and São Domingos did not present much variation. Brancanes soils and plants presented strong differences compared to other areas.ConclusionsCistus ladanifer plants are able to survive in mining areas with polymetallic contamination at different elements concentrations in total and available fraction. This species presented variations inter- and intra-populations in accumulation and translocation of chemical elements; however, all studied populations, except Brancanes, can belong to the same population cluster.

The physiological mechanisms underlying the ability of Cistus monspeliensis L. from São Domingos mine to withstand high Zn concentrations in soils

Cistus monspeliensis L. is a species that grows spontaneously in contaminated mining areas from the Iberian Pyrite Belt. This species can have high concentrations of Zn in the shoots without visible signs of phytotoxicity. In order to understand the physiological mechanisms underlying this tolerance, C. monspeliensis was grown at several concentrations of Zn(2+) (0, 500, 1000, 1500, 2000µM) and the effects of this metal on plant development and on the defence mechanisms against oxidative stress were evaluated. Independently of the treatment, Zn was mainly retained in the roots. The plants with the highest concentrations of Zn showed toxicity symptoms such as chlorosis, low leaf size and decrease in biomass production. At 2000µM of Zn, the dry biomass of the shoots decreased significantly. High concentrations of Zn in shoots did not induce deficiencies of other nutrients, except Cu. Plants with high concentrations of Zn had low amounts of chlorophyll, anthocyanins and glutathione and high contents of H2O2. The highest concentrations of Zn in shoots of C. monspeliensis triggered defence mechanisms against oxidative stress, namely by triggering antioxidative enzyme activity and by direct reactive oxygen species (ROS) scavenging through carotenoids, that are unaffected by stress due to stabilisation by ascorbic acid.

Evaluation of chemical parameters and ecotoxicity of a soil developed on gossan following application of polyacrylates and growth of Spergularia purpurea.

The aim of this study was to evaluate the chemical characteristics and ecotoxicity of a mine soil developed on gossan materials and amended with hydrophilic polyacrylate polymers after a growth cycle of Spergularia purpurea. Different acute bioassays (Daphnia magna immobilization; microalgae growth inhibition; germination and growth of lettuce and oat) were carried out with simulated leachates, pore water and soil samples. The germination and growth of native shrubs (Cistus ladanifer and Lavandula sampaioana) were also evaluated in the lysimeters where S. purpurea had grown. The soil had high total concentrations (g/kg) of Al (3.50-8.60), As (2.55-2.73), Cu (0.13-0.91) and Pb (4.48-6.16). However, the percentages of elements in aqueous extracts (simulating leachates, pore water, and the conditions of the rhizosphere soil) were small when compared to their total soil concentrations (less than 9% except for Na in leachates). Growth of S. purpurea and other natural colonization of plant species (Poaceae, Fabaceae and Asteraceae families) improved chemical characteristics but the application of the polyacrylate polymers contributed to a further improvement of soil quality. However, this was not sufficient to ensure the growth of a large number of shrubs despite a great germination rate. Among the several species used on the ecotoxicological assessment, the D. magna test was the only bioassay that showed a clear toxicity of soil leachates, suggesting the importance of using several ecotoxicological tests to assess the environmental risk of soil contamination and its rehabilitation. Although the studied soil can be considered contaminated taking into account the total soil concentrations of Al, As, Cu and Pb, the low concentrations of the same chemical elements in extractable solutions, that simulated the fractions really available for organisms, did not demonstrate a substantial toxic effects in the organisms and, consequently, negative impact on the environment.

Potential Hazardous Elements Fluxes from Soil to Plants and the Food Chain

Chemical elements exist naturally in the environment with different concentrations. However, human activities can increase these concentrations, what represent a serious threat to ecosystems and to the human health. In soil, the chemical elements are distributed in different physicochemical forms; inorganic species, organic complexes, adsorbed on solid phases or as constituents of solid phases with different solubility degrees. Plants can absorb only the elements present in the so-called available fraction, which is associated to the exchange complexes and soluble fractions in the soil solution. Absorption, translocation and accumulation of the elements in the plants depend on the species and ecotype as well as on the plant organ, climatic conditions and season of the year. Usually, essential elements (macro and micro-nutrients) are absorbed and translocated to the aerial part of the plant, while toxic elements are retained in the roots, however some hazardous elements are also transported to shoots. High concentrations of toxic elements in the plants can affect their biological processes and/or trigger different physiological responses to combat the oxidative stress (e.g. antioxidative enzymes, glutathione, phytochelatins). The elements accumulated in edible organs of crops or in spontaneous plants represent the major entry point in the food chain. Even at concentrations below phytotoxic levels, hazardous elements can pose health risks for humans due to the augmentation effect along the food chain. The objective of this chapter was to elucidate/clarify the pathways of the chemical elements in the soil-plant-human system as well as the physiological mechanisms that plants develop to respond to the absorption and accumulation of hazardous chemical elements.

Hazard Assessment of Soils and Spoils From the Portuguese Iberian Pyrite Belt Mining Areas and Their Potential Reclamation

Abstract Mining activity in the Iberian Pyrite Belt (IPB) is ancient and leads to several environmental problems associated with chemical characteristics of the mine wastes and their leachates. In general, mine wastes have limiting conditions for the healthy development of most of the organisms. Soils developed on mine wastes or influenced by mine wastes or acid mine drainage have multielemental contamination and wide heterogeneity in their properties. The quality and hazard risk of soils and mine wastes have been measured by the alteration of several chemical, ecotoxicological and biological indicators. The rehabilitation of these areas is essential in order to decrease environmental risk. This chapter is a review of the environmental problems associated with mine wastes and contaminated soils from the Portuguese sector of the IPB, the methodologies used for their quality evaluation, and advantages and limitations of rehabilitation/reclamation techniques.

Cistus monspeliensis L. as a potential species for rehabilitation of soils with multielemental contamination under Mediterranean conditions

The Iberian Pyrite Belt (IPB; SW of the Iberian Peninsula) is one of the most important volcanogenic massive sulphide ore deposits in the world. Cistus monspeliensis L. is a native woody shrub that grows spontaneously in non-contaminated soils as well as in soils with multielemental contamination from the IPB. In this study, different ecophysiological parameters of C. monspeliensis growing in soils with different levels of metal(loid)s were evaluated to assess the potential of this species for revegetation of degraded areas. Composite samples of plants and rhizosphere soils were sampled in São Domingos and Lousal mines and in a reference area without soil contamination (Pomarão, Portugal) (Portuguese sector of IPB). Classical characterisation of the soils and quantification of their total and available metal(loid) concentrations were done. Multielemental concentration was determined in plants (shoots and roots). Ecophysiological parameters were also determined in shoots: concentrations of pigments (chlorophylls, anthocyanins and carotenoids), antioxidants (glutathione and ascorbate) and hydrogen peroxide as well as activities of several antioxidative enzymes. Although mining soils present high total concentrations of potentially hazardous elements, their available fractions were low and similar among studied areas. Soil pH as well as concentrations of extractable P, total concentrations of As, Cd and Ni and concentrations of Cu, Cr, Ni, Pb and Sb in the soil available fraction differentiate the studied areas. Only concentrations of Cd, Pb and Sb in roots and shoots were explained by the concentrations of the same elements in the soil available fraction. Although the majority of elements were translocated from roots to shoots, the shoots concentrations were below the toxic values for domestic animals and only As, Mn and Zn reached phytotoxic concentrations. Ecophysiological parameters were similar independently of the studied area. Due to its adaptability, tolerance and standard plant features, C. monspeliensis is a good choice for rehabilitation of soils with multielemental contamination under similar climatic characteristics.

Rehabilitation of abandoned areas from a Mediterranean nature reserve by Salicornia crop: Influence of the salinity and shading

ABSTRACT In Reserva Natural de Castro Marim e Vila Real de Santo António (SE of Portugal), most of the salt marshes and saltpans are abandoned contributing to their degradation and, consequently, alteration of some ecological conditions. Rehabilitation of these areas by a Salicornia crop can contribute to their economic and environmental improvement by stimulation of biogeochemical processes and biomass commercialization. However, the development of agro-techniques adjusted to species and variable environmental conditions from Mediterranean are needed in order to improve the Salicornia crop. This study aimed to evaluate: i) potential use of seedlings from greenhouse in the field cultivation; and ii) survival, growth and yield of Salicornia under shading and different salinity conditions of the soils and irrigation waters. Autochthonous Salicornia species (S. ramosissima and S. patula) were tested. Germination tests under controlled conditions and in situ mesocosm assays were carried out. Assays were realized with a low density of seedlings from natural conditions and greenhouse, and soils and waters from estuary both with different salinities. Intermediate and high salinities (25–45 dS/m) affected only S. patula germination. In general, Salicornia growing in soils with low salinity had great fresh biomass accumulation independently of seedling source (from natural conditions and greenhouse) and/or growing season. The shading seems to improve the fresh biomass accumulation and yield. Under Mediterranean conditions, the transplantation of Salicornia from greenhouse to the field was a promising technique, independently of the salinity conditions. This study demonstrated that the abandoned and saline areas can be rehabilitated by a sustainable crop of Salicornia.

Engineered Soils Using Amendments for In Situ Rehabilitation of Mine Lands

Abstract Mining and quarrying activities have been carried out since ancient times. Although at different levels, both abandoned and active mines have several environmental problems associated to soil excavation and physical–chemical characteristics of the mine wastes and their leachates. Environmental impacts are highly variable but, in general, lead to the degradation of soils and waters (e.g., loss of soil structure and fertility, acidification/alkalinization, contamination by potentially hazardous elements, and decrease of the biodiversity). The rehabilitation of mining areas is essential to decrease environmental impacts and must include ecological approaches and economic considerations. This chapter presents a review on the environmental problems associated with quarries and mining areas of sulfide ores and coal and describes the advantages and limitations of some ecotechnologies for in situ rehabilitation.