Arsenic containing phases in soils from São Domingod mining area and in non-contaminated soils from Pomarão and Serra do Caldeirão

São Domingos mining area is located in the Iberian Pyrite Belt, in south-east Portugal. Intensive gossan gold, copper and silver mining was done in roman times. More recently, mining activities were concentrated in the copper, zinc, arsenic and lead rich sulfide orebodies. To evaluate arsenic hazard, soils developed on the gossan mine waste piles were analysed, using as reference non- contaminated soils from Pomarão (south east Portugal) and Serra do Caldeirão (south of Portugal). Soils were characterized by the classical methodologies for pH (H2O), particle size distribution, cation exchange capacity, Fe and Mn oxides, and mineralogy. The soils (fraction <2 mm) were analysed, for total concentrations of As, Cu, Fe, Mn, Pb and Zn by instrumental neutron activation analysis after acid digestion and, for the concentration of As associated with the different soil phases (exchangeable complex, organic matter, total and non-crystalline Fe oxides and Mn oxides), by hydride generation atomic absorption spectrometric after selective chemical extractions with appropriate reagents using the parallel method. São Domingos soils contain high levels of total As (1940-3030 mg kg-1) but the available fraction is very low (<0,02% from total) being lower than Pomarão and Serra do Caldeirão available fractions (respectively, 0,13 and 1% from total). Arsenic is mainly in the residual fraction of the soils of São Domingos mining area (91-94% of total) while in the Pomarão and Serra do Caldeirão reference soils arsenic is mainly associated with crystalline Fe oxides (respectively, 24 and 37% of total). The arsenates: carminite (Fe2Pb(AsO4)2(OH)2), mimetite (Pb5(AsO4)3Cl), segnitite (Fe3Pb(AsO4)(HAsO4)(OH)6), and seldom kankite (FeAsO4·3.5H2O) were identified in São Domingos soils. The low solubility of these solid phases can explain the low availability of arsenic present in these soils in spite of the high concentrations of total arsenic. The results show that, under the present physical-chemical conditions, arsenic in the soils of the São Domingos mine presents no environmental hazard

Lead uptake capacity of Cistus plants growing in mining areas

Mining activity can give rise to large quantities of chemically unstable waste rocks and tailings which can drain potential environmentally harmful lixiviates rich in chemical elements. Plants growing in such environments can minimize chemical, physical and visual negative impacts. To evaluate lead absorption by native Cistus growing in Braçal (NW Portugal) and São Domingos (SE Portugal) mining areas, Cistus inflatus (aerial parts) and Cistus ladanifer (leaves) were analysed by instrumental neutron activation analysis and atomic absorption spectrometric, respectively, after acid digestions. Soils were characterized by pH(H2O), organic carbon, cation exchange capacity, free Fe and Mn, total nitrogen, and assimilable K and P. Total lead was determined in soils (fraction < 2 mm) by inductively coupled plasma emission spectrometry after acid digestion, and Pb available fraction was determined by atomic absorption spectrometric and inductively coupled plasma mass spectroscopy after calcium nitrate extraction. High concentrations of total Pb are present in both mining areas soils. However, in São Domingos soils the Pb available fraction is smaller (8.3–67.3 mg kg-1) than in Braçal (276–6175 mg kg-1). Cistus inflatus aerial parts contain higher concentrations of lead (49.5–217 mg kg-1) than Cistus ladanifer leaves (40.4–48.6 mg kg-1). Both Cistus, showing no external stress signals, are well adapted to these contaminated soils with low nutrient and high Pb contents. It is apparent that these plants can be used for phytostabilization in similar mining areas

Biogeochemistry evaluation of soils and arbutus trees in the Panasqueira mine area

Panasqueira mine is one of the most important mines in Portugal. Over the last century exploration of tungsten, copper and tin has contributed to produce many waste materials that constitute tailings with huge dimensions generating high visual and chemical impacts. The objective of this work was to study the biogeochemical impact of mining on the soils and arbutus trees (Arbutus unedo) in this are

Availability of Cu, Pb and Zn in Canal Caveira and São Domingos mine areas from Iberian pyrite belt

Several mining areas are abandoned in the Iberian pyrite belt (IPB) leading to important points of environmental contamination. The potential and immediate environmental risk and impact on public health of hazardous elements from soil can be estimated from availability analysis. The aim of this study was to evaluate the availability of Cu, Pb and Zn in São Domingos and Canal Caveira mining areas located in the IBP

Potencialidades do Pinus pinaster e Cytisus multiflorus na fitoestabilização de escombreiras na mina de ouro de Santo António (Penedono) Potencialities of Pinus pinaster and Cytisus multiflorus on the phytostabilization of the Santo António (Penedono) gold mine dumps

A mina de Santo António, localizada a cerca de 10 km ao norte de Penedono (Viseu), foi um importante centro mineiro, tendo-se aí principalmente explorado o ouro e outros elementos químicos, como o arsénio. Actualmente, todo o complexo mineiro está abandonado e bastante degradado. As escombreiras, cortadas por dois barrancos de grande dimensão, estão sujeitas a intensa erosão eólica e hídrica. Estas apresentam teores totais elevados para vários elementos, dos quais se destacam As, Pb, Cd e Au que atingem, respectivamente, 40 000, 653, 14 e 9,8 mg kg-1 . Estudou-se na área mineira, e em particular na envolvente das escombreiras, os solos e as plantas aí desenvolvidas (Pinus pinaster, Quercus pyrenaica, Castanea sativa, Cytisus multiflorus e uma gramínea do género Agrostis). As águas de drenagem da escombreira não vegetalizada apresentavam valores de pH de 2,58 e teores de As e Cd respectivamente de 160 e 0,05 mg/L. As águas recolhidas a jusante de escombreiras vegetalizadas com pinheiros e giestas, mostraram um decréscimo drástico de todos os elementos, em especial do As que ocorria com valores ambientalmente aceitáveis (<0,1 mg/L). O pH dos solos varia entre 2,9 e 5,3. O arsénio nos solos próximos das escombreiras pode atingir valores de 23900 e 220 mg kg-1 respectivamente para os totais e disponíveis. A fracção disponível de Al e Cu atinge também valores elevados, respectivamente 32,9 e 55,4 mg kg-1, enquanto que os teores de Pb disponível são relativamente baixos quando comparados com os totais. As plantas colhidas nos solos adjacentes às escombreiras são bastante tolerantes aos elementos metálicos pois não manifestam sintomas visuais de toxicidade. O P. pinaster, o C. multiflorus e a gramínea apresentam teores elevados de As, Al e Pb na parte aérea, que são superiores aos das outras espécies. Estas espécies apresentam, no entanto, bom desenvolvimento vegetativo e boa cobertura do solo, minimizando assim a erosão hídrica e eólica. Por esta razão, a fitoestabilização das escombreiras desta mina pode ser efectuada por plantas autóctones do estrato arbóreo (Pinus pinaster), arbustivo (Cytisus multiflorus) e herbáceo (gramíneas do gén. Agrostis) que absorvem e translocam para a parte aérea teores relativamente elevados de As, reduzindo a sua lixiviação.<br>The Santo António mine is located 10 km north of Penedono (Viseu, Portugal). This mine was in the first half of the twenty’s century an important gold and arsenic mining centre. Nowadays the mining complex is abandoned and presents high level of physical degradation. The waste dumps crossed by two large gullies are under strong water and wind erosion. The total concentrations of As, Pb, Cd e Au, in the dump material reached values as high as 40 000, 653, 14 and 9,8 mg kg-1, respectively. Soils and native plants as Pinus pinaster, Quercus pyrenaica, Castanea sativa, Cytisus multiflorus and gramineous plants (gen. Agrostis) from the mining area and the waste dumps surroundings were collect and analysed. The draining waters from a no vegetated dump presented a pH value of 2.58, and As and Cd concentrations of 160 and 0.05 mg/L, respectively. On the other hand, the draining waters from vegetated dumps with P. pinaster and C. multiflorus showed much lower levels for the concentrations of all analysed elements, particularly As that presented environmentally acceptable concentrations (<0,1 mg/L). Soil pH is between 2.9 and 5.3. Arsenic total and available concentrations in the soils surrounding the waste dumps were as high as 23900 and 220 mg kg-1, respectively. Aluminium and Cu concentrations in the available fractions were, respectively, 32.9 e 55.4 mg kg-1. However, Pb concentrations were quite low in the available fractions when compared with the total concentrations in the soils. Plants growing on the dump adjacent soils are metal tolerant without any visible symptoms of toxicity. P. pinaster, C. multiflorus and Agrostis gramineous plants showed higher levels for As, Al, and Pb in the aerial part when compared with other species. Nevertheless, these species show a good vegetative development and soil coverage, which minimises the wind and water erosion. For this reason, the phytostabilization of Santo António waste dumps can be undertaken by native plants as P. pinaster trees, C. multiflorus shrubs and gramineous plants (Agrostis), which absorb and translocate to the aerial part high levels of As, thus decreasing the amounts lixiviated

Heat capacities of concentrated aqueous solutions of sodium sulfate, sodium carbonate, and sodium hydroxide at 25 °C

Heat capacities of aqueous solutions of Na2SO4 and Na2CO3 up to near saturation (1.9 and 2.5 mol·kg-1, respectively) and of NaOH (to 7 mol·kg-1) have been measured at 25 °C with a Picker flow calorimeter. The calorimeter performance was checked using concentrated NaCl(aq) solutions. On the basis of these measurements, an experimental protocol suitable for the reliable determination of the heat capacities of concentrated electrolyte solutions by Picker calorimetry was established. The heat capacities for Na2SO4(aq), Na2CO3(aq), and NaOH(aq) and literature data for the apparent molar volumes of NaOH(aq) at 25 °C were correlated using the Pitzer formalism. A number of inadequacies in previous models at high concentrations and for extrapolation to infinite dilution are discussed. In particular, it has been confirmed that the heat Capacity data for Na2CO3(aq) at low concentrations must be corrected for the hydrolysis of the carbonate ion. Standard partial molar heat capacities for the three salts and the standard partial molar volume of NaOH(aq)have been derived at 25 °C

Heat capacities of concentrated aqueous alkaline aluminate solutions at 25°C

Heat capacities of aqueous NaOH/NaAl(OH)4 solutions at total stoichiometric ionic strengths of up to 6 mol kg-1 and with up to 60 mol% substitution of OH- by Al(OH)4- have been measured at 25°C using a Picker flow calorimeter. The mean apparent molar heat capacities (Cpφ) of the NaOH/NaAl(OH)4 mixtures were linear with respect to Al(OH)4- substitution, consistent with Young's rule. This enabled Cpφ values to be derived for the hypothetical pure NaAl(OH)4(aq) solutions. The results so obtained are well described by a Pitzer model adapted from the literature, even up to high concentrations

Disponibilidade de Cu, Pb e Zn nas áreas mineiras de Canal Caveira e São Domingos - Faixa Piritosa Ibérica Availability of Cu, Pb and Zn in Canal Caveira and São Domingos mine areas from Iberian Pyrite Belt

Avaliou-se a disponibilidade do Cu, Pb e Zn nos solos das áreas mineiras de São Domingos e Canal Caveira (Faixa Piritosa Ibérica) com o objectivo de determinar a potencialidade de dispersão daqueles ele­mentos no meio. Em ambas as áreas as concentrações totais dos elementos foram elevadas e a dis­ponibilidade variou consoante as parcelas e, consequentemente, com as características dos solos. A fracção disponível de Pb é superior nos solos de Canal Caveira, contu­do para o Zn observou-se o contrário. Em ambos os solos, a fracção de Cu disponível é Several mining areas are abandoned in the Iberian Pyrite Belt (IPB) leading to important points of environmental con­tamination. The potential and immediate environmental risk and impact on public health of hazardous elements from soil can be estimated from availability analy­sis. The aim of this study was to evaluate the availability of Cu, Pb and Zn in São Domingos and Canal Caveira mining ar­eas located in the IPB. Both mining areas had high soil ele­mental total concentrations. Metals avail­ability changed with plots and, is related with soils characteristics. In Canal Caveira mine area, the Pb available frac­tion in soils was higher than in São Domingos soils however, the opposite was observed for Zn. The fractions of available Cu, in both mine soils, are <0.6 % of the total concentration. In both min­ing areas, Cu and Zn are mainly associ­ated with the residual fraction, while Pb is associated with residual fraction in São Domingos and with organic matter in Ca­nal Caveira soils