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

GeoBioTec - GeoBioSciences, GeoTechnologies and GeoEngineering Research Center and Department of Geosciences, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
Science of The Total Environment (Impact Factor: 4.1). 08/2009; 407(21):5620-36. DOI: 10.1016/j.scitotenv.2009.06.047
Source: PubMed


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.

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    • "Past research on acidophilic and acid-tolerant algae showed that algae are tolerant to metals, having mechanisms to avoid toxic effects (Gross, 2000; Lessmann et al., 2000). Diatoms' frustule deformations have been correlated with high metal concentrations in a large number of studies (Cattaneo et al., 2004; Ferreira da Silva et al., 2009), including in an interesting review published by Falasco et al. (2009). In this sense, determining the chemical speciation of dissolved metals/metalloids is crucial to understand the causes of valve teratologies, since the toxicological effects vary according to the availability of different metal species. "

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    • "In particular, large amounts of sediment and debris can flow into nearby streams due to heavy rainfall during the monsoon season. The substantial modification in physicochemical properties related to mine activities has been investigated intensively by many researchers (Meju 2000; Ferreira da Silva et al. 2009; Jiao et al. 2013; Neiva et al. 2014), especially with regard to heavy metal pollution, stream sedimentation, and ground subsidence during mining work; however, few studies have investigated miningrelated landslides. Recently, one of the largest known debris flows occurred at the Bingham Canyon open-pit copper mine, also known as the Kennecott Copper Mine, near Salt Lake City, Utah, USA (Pankow et al. 2014). "

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    • "This threshold was exceeded from the first week following translocation in M1, M2, M3 and MS, and increased with time of exposure , highlighting metal contamination. Abnormalities are increasingly used to evidence the deleterious impacts of metals in the field (Duong et al. 2008, Ferreira da Silva et al. 2009, Luís et al. 2011, Corcoll et al. 2012, Lavoie et al. 2012). Here, the correlation with zinc bioaccumulation (R 2 = 0.25, p = 0.03) confirmed the reliability of this endpoint. "
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    ABSTRACT: Background and aims – Diatom-based water quality management is increasing, and specific indicators are required for the assessment of priority substances such as metals. We tested a variety of features of diatom communities, in a river exhibiting a gradient of zinc contamination (the Riera d'Osor, Spain), to determine the most relevant ones. Key results – Community composition changed over time of exposure, and with the intensity of metal contamination. Species richness was significantly lower at the most contaminated sites. Species composition was more even under background and low exposure levels, but low metal inputs selected for varieties of Cocconeis placentula (var. placentula, euglypta and lineata). Small taxa (Eolimna minina, or Achnanthidium minutissimum and A. pyrenaicum) dominated in the most contaminated sites, and deformed diatom cells were found abundant. Conclusions – Although species composition clearly responded to varied levels of zinc pollution, combining cell size classes or total biovolume of the community and percentages of deformities allowed reliable assessment of the presence, and intensity, of contamination. These descriptors present the major advantage of being independent of regional taxonomic peculiarities, thus providing robust assessment irrespective of the area studied.
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