Eduardo Ferreira da Silva

Heavy metal pollution downstream the abandoned Coval da Mó mine (Portugal) and associated effects on epilithic diatom communities.

This study examined trace-element concentrations in 39 sediment samples collected in the vicinity of the abandoned Coval da Mó mine, and evaluated the anthropogenic contaminant effects and other environmental variables in the taxonomic composition, structure and morphological changes of benthic diatom communities. The results show the existence of extremely high contamination in Pb, Zn and Cd (the mean values exceed the background values 376, 96 and 19 times, respectively) on the first 2.5 km in the water flow direction. Also Co, Cu, Mn and Ni are present in high concentrations. Dilution by relatively uncontaminated sediment reduces metal concentrations downstream, but Zn concentrations increase downstream Fílvida stream, as a result of several factors such as sewage and agriculture. To evaluate the biological effects caused by Pb, Cd and Zn, three sites were selected. In the stressed environment, near the mining area (C232), diatoms were extremely rare, however there was a slight recovery at site C79 located 2km downstream. Fragilaria capucina var. rumpens, Fragilaria cf. crotonensis and Achnanthidium minutissimum showed abnormal valves which may be related to high levels of metals. Six km downstream, in Fílvida stream (C85), an increase in species richness and diversity was registered while the relative percentage of valve teratologies was lower. In the absence of OM, nutrients and low pH the diatom community patterns must be attributed to the metal concentration at some sites. Considering that community diversity can be affected by abiotic and biotic variables and valve deformations are caused by a small number of variables, basically metals, and acid conditions, we consider the presence of teratologies as an indication of the presence of metals.

Sources of potentially toxic elements and organic pollutants in an urban area subjected to an industrial impact

Urban and industrial development has caused a major impact on environmental soil quality. This work assesses the extent and severity of contamination in a small urban area subjected to an industrial impact and identifies the major anthropogenic inputs. Twenty-six soil samples were collected from agricultural and urban sites, and concentrations of potentially toxic elements (As, Cd, Cu, Cr, Fe, Mn, Ni, Pb and Zn), PAHs and PCBs, were determined. In spite of the low median concentrations observed, some sites represent a potential hazard for human health and ecosystems. Concentrations of contaminants were higher than those found in a nearby city, indicating that the study area is affected by the surrounding industry. The use of multivariate statistical analyses allowed for the identification of the main factors controlling the variability of potentially toxic elements and organic pollutants in the soils. The presence of Cr, Fe, Mn and Ni was associated with geogenic inputs, and Cu, Pb, Zn, As, PAHs and PCBs were associated with anthropogenic inputs. Industry and traffic were the most important anthropogenic sources. Soil characteristics were identified as important factors controlling the spatial variability of elements, both from recognised natural and anthropogenic origin. Differences between land uses were observed, which may be attributed to both management practices and proximity to sources.

Heavy elements in the phosphorite from Kalaat Khasba mine (North-western Tunisia): Potential implications on the environment and human health

Tunisia is one of the largest phosphate producers in the world (more than 10 million tons per year since the early nineties). The Kalaat Khasba mine (NW of Tunisia) has operated from 1893 until 1993 and data demonstrate that, in the phosphorites of Kalaat Khasba, Cd is enriched 105-208 times, when compared with shales, and U is enriched by a factor varying between 18 and 44. The general trend shows an increase in heavy elements content with decreasing particle size. On the other hand, concentrations of Sr, Cr and U exhibit the same distribution for the different size fractions. It was found that Cd concentrations exceed the allowed EC soil limits for growing crops. Hence, owing to the tailings exposure and to the mobilisation of the finest particles by rainfall and wind, Cd could have detrimental effects on human health and on the environment because a significant portion of Cd was found in the exchangeable form.

Assessment of human exposure to environmental heavy metals in soils and bryophytes of the central region of Portugal

This study intends to identify the spatial patterns of variation for some metals and metalloids, in soils and mosses, in the central region of Portugal. The purposes were: (i) to identify relationships amongst five elements (Cu, Pb, Zn, Cr and As) in three different media (topsoil, bottom soil and bryophytes) and with some site-specific characteristics, using Multiple Correspondence Analysis; (ii) to define spatial patterns of variation for the associations identified by Multiple Correspondence Analysis using Variography and Ordinary Kriging; and (iii) to assess atmospheric deposition as a source of heavy metals to the topsoil by crossing results with the biomonitors. The results indicated relatively low metal concentrations in soils and mosses. Some metal associations and dissociations were identified. The spatial patterns of variation of bottom and topsoil are distinct. There is some evidence that different site-specific characteristics control the spatial distribution of different elements. The areas within the central region of Portugal with a higher vulnerability to metal contamination were identified.

Source and pathway analysis of lead and polycyclic aromatic hydrocarbons in Lisbon urban soils.

One hundred soil samples were collected from urban spaces, in Lisbon, Portugal, in two surveys that were carried out in consecutive years, to assess the potential adverse human health effects following exposure to potentially toxic elements and organic compounds in the urban soils. The study hereby described follows on from the earlier work of the authors and aims at performing a source-pathway-fate analysis of lead (Pb) and polycyclic aromatic hydrocarbons (PAHs) in the urban soils in order to increase current knowledge on factors influencing exposure of the population. Various techniques were combined to achieve the proposed goal. Geogenic and anthropogenic sources were apportioned by means of Pb isotope mixing models. Isotope data was further coupled with geographic information system mapping to assess local mixed sources of Pb and PAHs. Unleaded vehicle exhaust and cement production show the largest relative contribution to the total soil-Pb, but their respective importance depends on factors such as location and urban landscape. The primary sources of PAHs to the urban soils are probably air and land traffic. Multivariate analysis was used to investigate which soil properties could influence mobility and fate of the contaminants. Whilst principal components analysis indicates carbonates and other calcium phases as probable factors controlling the dispersion of Pb in the urban soils, the linear models obtained from stepwise multiple regression analysis show that soil phosphorous (P) and manganese (Mn) are good predictors of the total soil Pb content. No robust model was obtained for the PAHs, impeding identifying environmental factors most likely to influence their dispersion in the urban soils. The solid-phase distribution study provided critical information to untangle the, at a first glance, contradictory results obtained by the multivariate analysis. Carbonates and other calcium phases, having these a probable anthropogenic origin, are soil components containing major fractions of Pb, P, and Mn.

Integrated approach to assess the environmental impact of mining activities: estimation of the spatial distribution of soil contamination (Panasqueira mining area, Central Portugal)

Through the years, mining and beneficiation processes in Panasqueira Sn-W mine (Central Portugal) produced large amounts of As-rich mine wastes laid up in huge tailings and open-air impoundments (Barroca Grande and Rio tailings) that are the main source of pollution in the surrounding area once they are exposed to the weathering conditions leading to the formation of acid mine drainage (AMD) and consequently to the contamination of the surrounding environments, particularly soils. The active mine started the exploration during the nineteenth century. This study aims to look at the extension of the soil pollution due to mining activities and tailing erosion by combining data on the degree of soil contamination that allows a better understanding of the dynamics inherent to leaching, transport, and accumulation of some potential toxic elements in soil and their environmental relevance. Soil samples were collected in the surrounding soils of the mine, were digested in aqua regia, and were analyzed for 36 elements by inductively coupled plasma mass spectrometry (ICP-MS). Selected results are that (a) an association of elements like Ag, As, Bi, Cd, Cu, W, and Zn strongly correlated and controlled by the local sulfide mineralization geochemical signature was revealed; (b) the global area discloses significant concentrations of As, Bi, Cd, and W linked to the exchangeable and acid-soluble bearing phases; and (c) wind promotes the mechanical dispersion of the rejected materials, from the milled waste rocks and the mineral processing plant, with subsequent deposition on soils and waters. Arsenic- and sulfide-related heavy metals (such as Cu and Cd) are associated to the fine materials that are transported in suspension by surface waters or associated to the acidic waters, draining these sites and contaminating the local soils. Part of this fraction, especially for As, Cd, and Cu, is temporally retained in solid phases by precipitation of soluble secondary minerals (through the precipitation of hydrated metal sulfates) in warm, dry periods, but such minerals are easily dissolved during rainy periods. Climate is an important instability factor, and the hot and dry summers and cold, rainy, and windy winters in this region are physical phenomena that enhance the good receptivity of these soils to retain some of the metals present in the primary and also the secondary mineralogy. Considering the obtained results from both the sequential chemical extraction and the environmental risk assessment according to the risk assessment code, Ag, Cd, Cu, and Zn are classified with very high risk while As is classified with medium risk.

Diatom assemblages of thermal and mineral waters from volcanic environments in São Miguel Island, Azores

Volcanic areas are hostile environments where the release of toxic gases is added to the low pH and high temperature, subjecting living organisms to extreme conditions. High-temperature environments, particularly those associated with volcanic activity have been evolving on earth throughout time. The aim of this study is to contribute to increasing knowledge of these high-temperature events and describe their associated diatom assemblages. The fumarolic fields of São Miguel Island in the Azores Archipelago were selected as a case study due to its particular characteristics and were studied seasonally during 2007. Temperature, pH and conductivity variables were measured in situ. Other environmental data were available in the literature. Diatom diversity, assessed using the Shannon–Wiener Index (H′), ranged between 0.02 and 4. Statistical analyses revealed that temperature is a significant driver for the distribution of diatom species. Achnanthidium exiguum Grunow, Nitzschia cf. thermalis var. minor (Hilse) Grunow, Pinnularia joculata (Manguin) Krammer, P. trivialiformis Lange-Bertalot & Metzeltin and P. subcapitata Gregory were prominent with relative abundance above 40% of diatom assemblages. Some diatom taxa with high relative abundance, such as N. cf. thermalis and P. joculata may be considered representative of thermal springs and may be considered important biological indicators of geochemical changes induced by volcanic activity.

Assessment of metal pollution in a former mining area in the NW Tunisia: spatial distribution and fraction of Cd, Pb and Zn in soil

This study aims to evaluate the impact of the former mining Touiref district (NW Tunisia) on the spatial distribution of metal contamination. In order to characterize the metal content of the tailings and to assess how far the soils from the district could be impacted by metals, a sampling campaign was conducted. According to the spatial distribution concentration maps of potential toxic elements (PTE), the highest concentrations occur near the flotation tailings and in mining facilities and decrease abruptly with distance. These results confirm that wind is the main agent capable of dispersing metals in a W–E direction, with concentrations exceeding the standards of soil quality for Cd, Pb and Zn over several hundred metres away from the source, facilitated by the small-size fraction and low cohesion of tailings particles. Chemical fractionation showed that Pb and Cd were mainly associated with the acid-soluble fraction (carbonates) and Fe-(oxy) hydroxides, while Zn was mainly associated with Fe-(oxy) hydroxides but also with sulphides. Thus, the immobilization of metals in solution may be favoured by the alkaline conditions, promoted by carbonates dissolution. However, being carbonate important-bearing phases of Cd and Pb (but also for Zn), the dissolution facility of these minerals may enhance the release of metals, particularly far away from the mine where the physicochemical conditions can be different. Also, the metal uptake by plants in these alkaline conditions may be favoured, especially if secondary phases with high sorption ability are reduced at this site. A remediation plan to this area is needed, with particularly attention in the confinement of the tailings.

Integrating geochemical (surface waters, stream sediments) and biological (diatoms) approaches to assess AMD environmental impact in a pyritic mining area: Aljustrel (Alentejo, Portugal)

Aljustrel mines were classified as having high environmental hazard due to their large tailings volume and high metal concentrations in waters and sediments. To assess acid mine drainage impacted systems whose environmental conditions change quickly, the use of biological indicators with short generation time such as diatoms is advantageous. This study combined geochemical and diatom data, whose results were highlighted in 3 groups: Group 1, with low pH (1.9-5.1) and high metal/metalloid (Al, As, Cd, Co, Cu, Fe, Mn, Ni, Pb, Zn; 0.65-1032 mg/L) and SO4 (405-39124 mg/L) concentrations. An acidophilic species, Pinnularia aljustrelica, was perfectly adapted to the adverse conditions; in contrast, teratological forms of Eunotia exigua were found, showing that metal toxicity affected this species. The low availability of metals/metalloids in sediments of this group indicates that metals/metalloids of the exchangeable fractions had been solubilized, which in fact enables metal/metalloid diatom uptake and consequently the occurrence of teratologies; Group 2, with sites of near neutral pH (5.0-6.8) and intermediate metal/metalloid (0.002-6 mg/L) and SO4 (302-2179 mg/L) concentrations; this enabled the existence of typical species of uncontaminated streams (Brachysira neglectissima, Achnanthidium minutissimum); Group 3, with samples from unimpacted sites, showing low metal/metalloid (0-0.8 mg/L) and SO4 (10-315 mg/L) concentrations, high pH (7.0-8.4) and Cl contents (10-2119 mg/L) and the presence of brackish to marine species (Entomoneis paludosa). For similar conditions of acidity, differences in diversity, abundance and teratologies of diatoms can be explained by the levels of metals/metalloids.

Contribution for the Derivation of a Soil Screening Value (SSV) for Uranium, Using a Natural Reference Soil

In order to regulate the management of contaminated land, many countries have been deriving soil screening values (SSV). However, the ecotoxicological data available for uranium is still insufficient and incapable to generate SSVs for European soils. In this sense, and so as to make up for this shortcoming, a battery of ecotoxicological assays focusing on soil functions and organisms, and a wide range of endpoints was carried out, using a natural soil artificially spiked with uranium. In terrestrial ecotoxicology, it is widely recognized that soils have different properties that can influence the bioavailability and the toxicity of chemicals. In this context, SSVs derived for artificial soils or for other types of natural soils, may lead to unfeasible environmental risk assessment. Hence, the use of natural regional representative soils is of great importance in the derivation of SSVs. A Portuguese natural reference soil PTRS1, from a granitic region, was thereby applied as test substrate. This study allowed the determination of NOEC, LOEC, EC20 and EC50 values for uranium. Dehydrogenase and urease enzymes displayed the lowest values (34.9 and <134.5 mg U Kg, respectively). Eisenia andrei and Enchytraeus crypticus revealed to be more sensitive to uranium than Folsomia candida. EC50 values of 631.00, 518.65 and 851.64 mg U Kg were recorded for the three species, respectively. Concerning plants, only Lactuca sativa was affected by U at concentrations up to 1000 mg U kg1. The outcomes of the study may in part be constrained by physical and chemical characteristics of soils, hence contributing to the discrepancy between the toxicity data generated in this study and that available in the literature. Following the assessment factor method, a predicted no effect concentration (PNEC) value of 15.5 mg kg−1 dw was obtained for U. This PNEC value is proposed as a SSV for soils similar to the PTRS1.