[Show abstract][Hide abstract]ABSTRACT: 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.
Full-text · Article · Aug 2009 · Science of The Total Environment
[Show abstract][Hide abstract]ABSTRACT: In order to study the anthropogenic impact of trace metals in the Caima and Mau River basins (north-central Portugal), 415 stream sediment samples were randomly collected in the main streams of these rivers and the minus 80-mesh fraction was analysed by Inductively Coupled Plasma – Optical Emission Spectrometry (ICP-OES). The presence of abandoned mines was identified as the main source of Cu, Pb, Cd and Ni in the area. A strong pair-wise correlation between Pb, Zn, Cd and Ni was found. In this study, the geochemical indices (Contamination Index (CI) and Multiple Pollution Index (MPI)), and the diatom indices (Specific Pollution Index (SPI) and Biological Diatom Index (BDI)) are used to define the Caima and Mau River basins environmental quality. The estimation of the CI and MPI indices shows that the sediments near Coval da M area are enriched with Pb, Cd, Zn Ni and Co suggesting an anthropogenic origin of metal contamination in this zone. In order to evaluate the biological effects caused by the trace metals, 17 sites were selected from the two River basins. Surface water and epilithic diatom communities were sampled during the summer of 2001. In general, the water and diatom data showed medium to good water quality. However, samples collected near the mining areas (Coval da M) revealed low abundance and diversity of diatom taxa indicating a stressed environment. Some diatoms showed morphologically abnormal valves that may be related to the high level of metal pollution in this area.
No preview · Article · Sep 2003 · Water Air and Soil Pollution