Electro-remediation of tailings from a multi-metal sulphide mine: comparing removal efficiencies of Pb,Zn, Cu and Cd

Sulphidic mine tailings characterised by high concentrations of heavy metals (Pb 3532?±?97?mg/kg, Zn 8450?±?154?mg/kg, Cu 239?±?18?mg/kg and Cd 14.1?±?0.3?mg/kg) and abundant carbonate (17%) were subjected to eight lab-scale electrodialytic remediation (EDR) experiments to investigate the influence of current density, treatment time and particle size on removal efficiency. Pb and Cu removal improved when increasing current density, while Zn and Cd removal did not. In contrast Zn and Cd removal improved by grinding the tailings, while Pb and Cu removal did not. At the highest current density (1.2?mA/cm²), 94%, 75%, 71% and 67% removal of Pb, Zn, Cu and Cd could be achieved, respectively, on grinded tailings in 28 days. Sequential chemical extraction made before and after EDR revealed larger oxidisable fractions of Zn, Cu and Cd, representing large fractions of sulphides, which was likely to be the main barrier to be removed as efficiently as Pb. This was in accordance with acid/base extraction tests in which Pb showed high solubility at both high and low pH (up to 65% and 86% of extraction, respectively), while considerable extraction of Zn (55%) happened only at low pH; and very limited extraction (<20%) of Cu and Cd occurred at any pH.     

The gastropod Osilinus atrata as a bioindicator of Cd,Cu, Pb and Zn contamination in the coastal waters of the Canary Islands

The aim of this study was to assess the use of Osilinus atrata (Gastropoda, Mollusca) as a biomonitor of heavy metals (Cd, Cu, Pb and Zn) within the coastal zone of the Canary Islands. In general, this top-shell snail showed high intraspecific variability in its tissue metal concentrations, which decreased according to the following sequence: Cu≥Zn>Cd≥Pb. In particular, Cd and Zn concentrations were higher in males than in females, whereas Cu concentrations increased slightly with weight, and Pb concentrations decreased. Cd and Cu concentrations showed notable spatial variability; Cd concentrations were higher in the eastern islands (Alegranza, La Graciosa, Lanzarote and Fuerteventura) and La Palma, whereas Cu levels were highest in some western islands (Gran Canaria, La Gomera and El Hierro). The arrival of waters from the African coastal upwelling, the pollution of coastal waters with agricultural fertilisers and the competition for uptake between metals appear to be the likely causes within these patterns of accumulation. In conclusion, O. atrata presents a great potential as a biomonitor of heavy metals, however, more information and further studies are necessary.     

Levels of heavy metals (Zn,Cu, Cd,and Pb) in mudskippers (Periophthalmodon schlosseri) and sediments collected from intertidal areas at Morib and Remis,Peninsular Malaysia

The concentrations of Zn, Cu, Cd, and Pb were determined in different tissues of mudskipper fishes Periophthalmodon schlosseri caught at two selected locations (Morib and Remis) of the intertidal mudflat area of Selangor state, West Coast of Peninsular Malaysia and in surface sediment samples. Metal concentrations in the mudskipper tissue and in the sediment samples tended to vary significantly (p < 0.05) between the two locations. Higher metal concentrations (except for Zn) were mostly found in the tissues of mudskippers from Remis. For sediment samples, significantly (p < 0.05) higher metal concentrations of all metals were also found at Remis. Generally, metal distribution between different tissues of mudskipper varied with scales being highly accumulative of Zn, Cd, and Pb, while for Cu, the highest mean concentrations were found in the liver. The lowest mean concentrations of Zn, Cu, and Cd were found in the muscles except for Pb, which was lowest in the liver. This study suggests that mudskippers can be potential biomonitoring organisms for heavy metal bioavailability and contamination of intertidal coastal mudflats. The concentrations of Cd and Pb were slightly above the acceptable limits of Malaysian and European food safety guidelines.     

Tissue distribution of Cd,Cu, Zn,Ni, Cr,Pb and Hg in striated heron,Butorides striatus (Aves: Ardeidae), in a fluvial ecosystem

In this study, the striated heron (Butorides striatus), a species that reproduces in the Middle Paraná River floodplain, was examined for lead, cadmium, chromium, zinc, nickel, mercury and copper concentrations, using liver, kidney, muscle, vertebra and feathers. The results showed low exposure to chromium because all tissue samples had concentrations below the limit of detection. Similar results were obtained for nickel and lead, with the exception of vertebra. This might be associated with either long-term exposure to these metals, or it may be that both nesting and wintering areas are non-polluted. Zinc and copper, both essential metals, were found in all tissues and their concentrations were within the ranges reported in the literature. Mercury was also found in all tissues, but at very low concentrations and even at concentrations below those that produce negative effects in several species of birds (e.g. reproductive success, food intake). Studies of this type are needed to interpret the role of organisms within environments impacted by different human activities.     

Biomonitoring of heavy metal (Cd,Cu, Pb,and Zn) concentrations in the west intertidal area of Peninsular Malaysia by using Nerita lineata

Snails, Nerita lineata, were collected from 15 sites along the west intertidal area of Peninsular Malaysia from December 2005 until April 2006. The concentrations of heavy metals (Cd, Cu, Pb, and Zn) were determined in the total soft tissues, operculums, and shells of the snails. Different patterns of heavy metal distributions were found in the different tissues (shell, operculums, and soft tissues) as well as spatial variations of heavy metal concentrations in the snails. This shows that the distribution of metals in the shells and the total soft tissues of N. lineata were not similar which could be due to different rates of metal accumulation, excretion, and sequestration. Since N. lineata is abundant on the rocky shores, below jetties and mangrove trees along the west intertidal area of Peninsular Malaysia and accumulate heavy metals, the snails are therefore potential biomonitors of heavy metal contamination for the west intertidal area of Peninsular Malaysia.     

Use of different soft tissues of Perna viridis a s biomonitors of bioavailability and contamination by heavy metals (Cd,Cu, Fe,Pb, Ni,and Zn) in a semi-enclosed intertidal water,the Johore Straits

Green-lipped mussels, Perna viridis, were collected from the eastern and western parts of the Johore Straits in September 2004 and January 2005. Based on the heavy metal concentrations in the different soft tissues (gonad, foot, mantle, gills, muscle, and remaining soft tissues) of these mussel samples, the eastern part of the Johore Straits (which is divided into two portions by a causeway), recorded higher levels of bioavailability and contamination by Cd, Cu, Fe, Ni, and Zn when compared to the western part, while Kg. Pasir Puteh in the eastern part was found to record the highest bioavailability and contamination by heavy metals. The use of different soft tissues of P. viridis as biomonitors of bioavailability and contamination by Cd, Cu, Fe, Pb, Ni, and Zn in the semi-enclosed Johore Straits is proposed, since erroneous results due to spawning and the problem of defecation before dissection could be overcome. Hence, a more accurate interpretation of the bioavailability and contamination by heavy metals in coastal waters could be obtained. To our knowledge, this is the most detailed study on the bioavailability and contamination of heavy metals in the Johore Straits on the Malaysian side of the waterway carried out by using the different soft tissues and metal distribution based on the Mussel Watch approach.     

Contamination and vertical distribution of As,Cd, Cr,Cu, Pb,Tl, and Zn in paddy soil irrigated with untreated leachate from tailings retention ponds

The contamination and vertical distribution of As, Cd, Cr, Cu, Pb, Tl, and Zn in paddy soil irrigated with untreated leachate from the tailings retention pond were investigated. As, Cr, Cu, and Zn were slightly contaminated in the surface soil and hence their vertical distribution was not obvious. However, Cd and Pb were highly contaminated in the surface soil, while their concentrations decreased with depth, being negatively correlated with pH and positively with total organic matter. Tl was considerably contaminated in the surface soil and a V-shaped vertical distribution was observed where the concentration increased to a maximum at about 30 cm depth and decreased thereafter. The findings revealed that the regular irrigation with untreated leachate from the tailings retention ponds could cause considerable contamination of Cd, Pb, and Tl, and thus tailings should be stringently treated before disposal to minimize their potential environmental impacts on the surroundings.     

Seasonal variation and partition of trace metals (Fe, Zn, Cu, Mn, Cr, Cd and Pb) in surface sediments: relationship with physico-chemical variables of water from the Calabar River, South Eastern Nigeria

The seasonal variation and partition of trace metals (Fe, Cu, Zn, Mn, Cd, Cr and Pb) in the surface sediments of the Calabar River are reported. Chemical partition of the metals in the sediments reveals that 2–30% of the total metal load was contributed by the non-detrital (acid-soluble) fraction, while fine-grained host minerals/compounds are the main carriers of the detrital (acid-insoluble) fraction (70–98%). Using multivariate statistical analysis, the seasonal fluctuations in the distribution of some of the metals show significant influence by physio-chemical changes (dissolved oxygen, pH, salinity and conductivity) in the water column. Fe–Mn oxide grain coatings and sulphide materials have been identified as scavengers of some of the non-detrital and detrital trace metals in the sediments. On the basis of index of geoaccumulation (I-geo) and comparison with previous studies, the Calabar River surface sediments have been classified as unpolluted.