I. Santa Regina

Arsenic, antimony, and other trace element contamination in a mine tailings affected area and uptake by tolerant plant species.

The study was conducted to characterize mineralogical and elemental composition of mine tailings in order to evaluate the environmental hazards, and identify the metal accumulation potential of native plant species from São Domingos mine, one of the long-term activity mines of the Iberian Pyrite Belt dating back to pre-Roman times. The mine tailings including soils and different plant species from São Domingos were analyzed for determination of tailings characteristics and chemical element contents in tailings and plants. The large amounts of mining wastes are causing significant adverse environment impacts due to acid mine drainage production and mobilization of potentially toxic metals and metalloids in residential areas, agricultural fields, downstreams, and rivers. The typical mineralogical composition is as follows: quartz, micas, K-feldspar, olivine-group minerals, magnetite, goethite, hematite, jarosite, and sulfides. The mine tailings were highly contaminated by As, Ag, Cr, Hg, Sn, Sb, Fe, and Zn; and among them, As and Sb, main contaminants, attained the highest concentrations except Fe. Arsenic has exhibited very good correlations with Au, Fe, Sb, Se, and W; and Sb with As, Au, Fe, Se, Sn, and W in tailings. Among the all plant species, the higher concentrations of all the metals were noted in Erica andevalensis, Erica australis, Echium plantagium, and Lavandula luisierra. Considering the tolerant behavior and abundant growth, the plant species Erica australis, Erica andevalensis,Lavandula luisierra,Daphne gnidium, Rumex induratus, Ulex eriocladus, Juncus, and Genista hirsutus are of major importance for the rehabilitation and recovery of degraded São Domingos mining area.

Mercury in soils and plants in an abandoned cinnabar mining area (SW Spain)

An abandoned cinnabar mining area located in the South-West of Spain has been studied with the aim of assessing its mercury pollution level and enhancing the knowledge about the Hg soil/plant relationship. To do so, soils and plants were sampled near an inactive smelter and around two mining sites present in this area. Critical total Hg concentrations were found in the close environs of pollutant sources. These also show high levels of elemental Hg (up to 8 mg kg(-1)), but quite low exchangeable Hg contents (0.008-0.038 mg kg(-1)). Most plant specimens display in their aboveground tissues Hg concentrations comprised in the range 0.1-10 mg kg(-1), with a great proportion (50%) showing critical levels. Greater Hg contents were found in plant specimens growing in soils with higher elemental Hg concentrations. The plant species displaying the greatest Hg levels are either perennial species of small-medium size and/or showing medium-highly corrugated leaves, or annual plants of small size. Marrubium vulgare L., Bromus madritensis L. and Trifolium angustifolium L. are the plant species with the highest Hg contents (37.6, 12.7 and 9.0 mg kg(-1), respectively). Leaf specific surface seems an important feature in the atmospheric Hg uptake by plants.

Antimony, arsenic and lead distribution in soils and plants of an agricultural area impacted by former mining activities

An agricultural area impacted by the former exploitation of an arsenical lead-antimony deposit was studied in order to assess the current and eventual environmental and health impacts. Samples of soils and cultivated (wheat) and spontaneously growing plants were collected at different distances from the mine pits and analyzed for the toxic element content and distribution. The soil total concentrations of Sb, As and Pb found in the uppermost soil layer (14.1-324, 246-758 and 757-10,660 mg kg(-1), respectively) greatly surpass their maximum tolerable levels in agricultural soils. Wheat grain Pb concentrations (0.068-1.36 mg kg(-1)) exceed the prescribed health standard, whereas Sb (<0.05-0.103 mg kg(-1)) and As (<0.05-0.126 mg kg(-1)) concentrations are below the permissible limits fixed for cereals. Of the spontaneously growing plants, Dactylis glomerata L. shows a relatively high root Pb accumulation and a very low Pb translocation, suggesting its feasibility to be used in Pb phytostabilization strategies.

Antimony and Arsenic Uptake by Plants in an Abandoned Mining Area

Abstract The degree of antimony (Sb) and arsenic (As) pollution and their bioavailability in mining‐affected grassland soils were determined. Antimony and As concentrations in aboveground parts of plants, collected in three consecutive years, were measured to investigate their uptake capacity, food chain contamination, and ecological risks. Total Sb and As contents in soils ranged from 60 to 230 mg/kg and from 42 to 4530 mg/kg, respectively, indicating a high degree of pollution of soils. The mobile fractions of Sb (0.02–0.27% of the total Sb content) and As (0.02–0.70% of the total As content) in soils, which reflect the plant‐available portion, are extremely low compared to total Sb and As contents in soils. The Sb and As contents in plants were also very low in both study areas. This lower accumulation of Sb and As in the plants is attributed to the low bioavailability of Sb and As in mine soils. Antimony and As contents in some plants were lower than the controls, and the concentrations in some plants were slightly higher than the normal grass mean level but were less than the phytotoxic or toxic levels for human or livestock consumption. The results of this study demonstrate that the plants growing in these mining areas, which have evolved As and Sb tolerance and detoxification capacity, can be cultivated to phytostabilize the metalloid‐contaminated mining sites.

Arsenic distribution in soils and plants of an arsenic impacted former mining area.

A mining area affected by the abandoned exploitation of an arsenical tungsten deposit was studied in order to assess its arsenic pollution level and the feasibility of native plants for being used in phytoremediation approaches. Soil and plant samples were collected at different distances from the polluting sources and analysed for their As content and distribution. Critical soil total concentrations of As were found, with values in the range 70-5330 mg kg(-1) in the uppermost layer. The plant community develops As tolerance by exclusion strategies. Of the plant species growing in the most polluted site, the shrubs Salix atrocinerea Brot. and Genista scorpius (L.) DC. exhibit the lowest bioaccumulation factor (BF) values for their aerial parts, suggesting their suitability to be used with revegetation purposes. The species Scirpus holoschoenus L. highlights for its important potential to stabilise As at root level, accumulating As contents up to 3164 mg kg(-1).

Dinámica de la descomposición de la hojarasca forestal en bosques de la cuenca del duero (provincia de zamora): Modelización de la pérdida de peso

Resumen Se ha estudiado la perdida de peso en el proceso de descomposicion de hojarasca en tres ecosistemas forestales de la zona semiarida Cuenca del Duero: un encinar climacico de Quercus rotundifolia Lam., un pinar paraclimacico de Pinus pinea L., y un pinar disclimacico de P. pinaster Ait. No se encuentran diferencias significativas entre la dinamica de descomposicion de las hojas en cada ecosistema, salvo cuando las hojas de encina se colocan en otros ecosistemas. La perdida de peso se ajusta a una curva exponencial negativa. En todos los casos, durante los cuatro primeros meses de experimentacion, el peso original se reduce en un 30%. Ello parece indicar que es la climatologia quien dirige fundamentalmente, a corto plazo, el proceso de descomposicion. En condiciones naturales, los indices de descomposicion (K j y K o) siguen la secuencia: encina > pino pinonero > pino maritimo, tanto en hojas como en hojarasca total.

Seasonal variation in nutrient concentration in leaves and branches of Quercus pyrenaica

. Seasonal variation in nutrient concentration in leaves and branches of Quercus pyrenaica was studied in natural Q. pyrenaica forest in the Sierra de Gata (Salamanca Province, Spain). Two permanent plots were established at the two extremes of a rainfall gradient in this area: annual mean precipitation from 720 mm at Fuenteguinaldo (granite bedrock) to 1580 mm at Navasfrias (schists and graywackes). Leaf and branch samples were collected every three weeks during the growing season from May to October, at three height levels of the tree canopy. Seasonal changes and internal nutrient dynamics were investigated for N, Ca, Mg, K, Na, Mn, Fe and P during a two-year period. The concentrations of all nutrients varied among the seasons; these variations were related to nutrient mobility and the annual physiological cycle. Nutrient concentrations decrease in the case of K and P, while the sparse mobile nutrients Ca, Mg, Mn and Fe gradually accumulated during each growing season. In Navasfrias a considerable resorption of P from senescing leaves was detected. Different patterns were found for the other nutrients studied (Na and N).

Dynamics of litter decomposition in two Mediterranean climatic zone forests of the Sierra de la Demanda, Burgos, Spain

Weight loss of litter due to decomposition was monitored for 2 years in two forest ecosystems in the Sierra de la Demanda, Spain, a Mediterranean climatic zone. The tree species considered were a climax beechwood (“Fagus sylvatica L.) and a reforested plantation of Scots pine forest fPinus sylvestris L). Weight loss due to decomposition of litter was similar in the two forest ecosystems, apparently due to the similarity in rainfall distribution at the sites. Jennys litter decomposition index (K) and Olsons litter decomposition index (Ko) were higher for the Scots pine forest than for the beech forest, 0.46 and 0.37, respectively, and Jennys leaves and Olsons decomposition indices were similar. The dynamics of carbon and nitrogen turnover during the 2 years was similar in the two sites, although there were seasonal rate differences. The decomposition rates in a Mediterranean climatic zone were closely related to those in temperate ecosystems.

Interaction between litter and soil epipedons in forest ecosystems of the Sierra de Gata Mountains, province of Salamanca, Spain

Potential and actual minimum returns of bioelements were estimated in four oak (Quercus pyrenaica) forest of the Sierra de Gata Mountains, Province of Salamanca, Spain, during two annual cycles. Leaves were the principal pool of potential bioele‐ment return, accounting for approximately 80% of return in Navasfrias and Villasru‐bias forests, and 70% in El Payo and Fuenteguinaldo forests. The greatest potential return of bioelements occurred in Fuenteguinaldo, especially N and Ca (53 and 32 kg ha−1 yf−1, respectively). The acidity of parent material seemed to affect the turnover of N, P, and K. The greater actual returns of N were found in Fuenteguinaldo (11.7 kg ha−1 yr−1), favored by a lower acidity of soil (pH = 5.4), and the losses of K were higher in the granite‐based soils (3.50 in the El Payo and 3.45 kg ha−1 yr−1 in the Fuenteguinaldo plots) due to an apparently greater plant assimilation of K. Granitic soils, above all at Fuenteguinaldo, were better nutrient balanced than the soils on schists, but ...

Mobility and phytoavailability of antimony in an area impacted by a former stibnite mine exploitation

A mining area affected by the abandoned mine exploitation of a stibnite deposit was studied to establish the current and eventual environmental risks and to propose possible remediation practices. Soil and plant samples were collected at different places in this area and analyzed for their Sb content and distribution. Critical soil total concentrations of Sb were found, with values ranging from 585 to 3184 mg kg(-1) dry weight in the uppermost soil layer, and decreasing progressively with soil depth. The readily labile Sb contents represent <2% of the total concentrations, whereas the soil Sb contents more susceptible of being mobilized under changing environmental conditions attain values of about 4-9% of the total concentrations. Remediation measures should be undertaken to limit off-site migration of Sb. Within the tolerant plant community growing in this area, the shrub Daphne gnidium L. stands out for its relatively high root Sb accumulation and low Sb translocation, suggesting its feasibility to be used in Sb phytostabilization strategies.