Heavy Metals In Recent Sediments Research Articles

Heavy metal distribution in recent sediments along the Tiet^|^ecirc; River basin (S^|^atilde;o Pauro, Brazil)

The distribution of heavy metals in recent sediments deposited along the Tiete River, a highly polluted river in southeast region of Brazil was studied. Around the metropolitan area of Sao Paulo city (25 million people), the pollution is related to municipal wastes and industrial effluents with reinforced downstream by agricultural activities. The observed increase of heavy metal concentrations is particularly important for Zn in the upper basin and Cu, Co and Cr at mouth. Geo-accumulation index calculation, related to the regional background, showed that the sediments along the basin are seriously polluted by heavy metals of anthropogenic origin, mainly Cu, Co, Cr and Zn. Calculated index suggests medium to very strongly pollution.

Distribution and Enrichment of Heavy Metals in Recent Sediments of Safaga Bay, Egypt

The present study was undertaken for assessing the level of heavy metals such as iron, manganese, zinc, copper, nickel, cadmium, lead, and cobalt in recent sediment samples of Safaga Bay, Egypt. Concentration of heavy metals in sediments shows significant variability and ranges from 863.37 to 1144.93 ppm for Fe, 64.29–586.8 ppm for Mn, 2.7–12.68 ppm for Zn, 3.01–7.2 ppm for Pb, 1.53–3.29 ppm for Ni, 0.55–1.57 ppm for Co, 0.16–1.37 ppm for Cu, and 0.22–0.4 ppm for Cd. Sediment pollution assessments were carried out using an enrichment factor and geoaccumulation index. The calculation of enrichment factor showed that Cd is enriched by 4.1 due to phosphate sources in Safaga Bay. The Geoaccumulation index results revealed that there are positive and negative correlations between Fe, Zn, Mn, Pb, Ni, Cu, Co, and Cd indicating that these metals have complicated geochemical behaviors.

Distribution and chemical fractionation of heavy metals in recent sediments from Lake Taihu, China

Distribution and chemical fractionation of heavy metals in recent sediments from Lake Taihu, China

Heavy metals in recent sediments and bottom-fish under the influence of tanneries in South Brazil

Selected metals were evaluated in surface sediments from Cadeia and Feitoria Rivers (Brazil), potentially affected by tanneries. Statistical factor analysis of sediment data allowed the identification of critical} metals and priority areas for biological monitoring, i.e., chromium and mercury at the lower course of Feitoria River. Non-piscivorous bottom-fish from the species Rineloricaria cadeae (violinha) were collected at reference and contaminated sites. Chromium was undetected} in fish tissues, and mercury accumulated in individuals living in contact with contaminated deposits. Mercury contents in fish were below World Health Organization quality standard for human consumption (0.5 μg/g). The ratio of total mercury content in fish (wet weight) to sediment (dry weight, <63 μm) was 0.5 and 0.7 at reference and contaminated sites, respectively. A risk assessment based on hazard index showed that maximum consumption of fish from contaminated site by human population should be 32 g/day, while at reference site the allowable amount could reach 140 g/day.

Speciation of heavy metals in recent sediments of three coastal ecosystems in the Gulf of Cádiz, southwest Iberian Peninsula.

A live-step sequential extraction technique was used to determine the partitioning of Cr, Mn, Fe, Cu, Zn, Cd, and Pb among the operative sedimentary phases (exchangeable ions, carbonates, manganese and iron oxides, sulfides and organic matter. and residual minerals) in coastal sediment from three locations in the southwest Iberian Peninsula. Two sites are located close to industrial areas, the salt marshes of the Odiel River and Bay of Cádiz, and one in a nonindustrial area, the Barbate River salt marshes. The Odiel River salt marshes also receive the drainage from mining activities in the Huelva region. In the sediments from the Bay of Cádiz and Barbate River salt marshes, Cr, Cu, Fe, and Zn were extracted from the residual fraction at percentages higher than 60%. In the sediments from the Odiel River salt marshes, concentrations of all the metals, except Cu. Zn, and Cd, exceeded 60% in the residual fraction as well. In the sediments from the Bay of Cádiz and Barbate River salt marshes, the main bioavailable metals were Mn and Cd; in those from the Odiel River salt marshes, the main bioavailable metals were Zn and Cd, respectively. The environmental risk was determined by employing the environmental risk factor (ERF), defined as ERF = (CSQV - Ci/CSQV), where Ci is the heavy metal concentration in the first four fractions and CSQV is concentration sediment quality value (the highest concentration with no associated biological effect). Our results showed that the sediments from the Cádiz Bay and Barbate River salt marshes do not constitute any environmental risk under the current natural conditions. In contrast, in the Odiel River salt marshes, Cu, Zn, and Pb yielded ERFs of less than zero at several sampling stations and, consequently, pose a potential threat for the organisms in the area. This is a consequence of the high levels of metals in the area derived from the mining activity (pyrite) and industrial activities and the association of these heavy metals with more labile fractions of the sediments.

Anthropogenically derived heavy metals in recent sediments of the Gulf of Finland, Baltic Sea

The anthropogenic loads of selected heavy metals in Recent soft sediments in the Gulf of Finland were studied through gravity corer sampling. Metals derived from silicates was excluded by applying a partial leach. Substraction of background values gave averages for the anthropogenically derived part of the heavy metal concentrations. The horizontal distribution of the metals in the surface sediments shows relatively high concentrations, especially in the eastern Gulf of Finland. The vertical distribution patterns vary from one part of the study area to another. Levels of all metals are relatively high in the upper part of the sediment profiles, usually with a decreasing trend in the topmost part of the profile. Averaged over the years 1993 to 1995 the annual accumulations of anthropogenically derived metals were, chromium 199 t, copper 158 t, cadmium 7.9 t, zinc 728 t, lead 165 t, cobalt 43.7 t and mercury 1.5 t.

Variation of heavy metals in recent sediments from Piratininga Lagoon (Brazil): interpretation of geochemical data with the aid of multivariate analysis

In the last decade, the Atlantic coast of south-eastern Brazil has been affected by increasing deforestation and anthropogenic effluents. Sediments in the coastal lagoons have recorded the process of such environmental change. Thirty-seven sediment samples from three cores in Piratininga Lagoon, Rio de Janeiro, were analyzed for their major components and minor element concentrations in order to examine geochemical characteristics and the depositional environment and to investigate the variation of heavy metals of environmental concern. Two multivariate analysis methods, principal component analysis and cluster analysis, were performed on the analytical data set to help visualize the sample clusters and the element associations. On the whole, the sediment samples from each core are similar and the sample clusters corresponding to the three cores are clearly separated, as a result of the different conditions of sedimentation. Some changes in the depositional environment are recognized using the results of multivariate analysis. The enrichment of Pb, Cu, and Zn in the upper parts of cores is in agreement with increasing anthropogenic influx (pollution).

Heavy metals in recent sediments from the Bay of Cadiz, Spain

Heavy metals in recent sediments from the Bay of Cadiz, Spain

Sources and sediment associations of heavy metals in polluted coastal regions

Vertical profiles and lateral distribution patterns of heavy metals in Recent sediments are increasingly employed in the assessment of the major sources of pollution in coastal regions, including estuaries and marginal seas. After a general review of studies from typical locations, examples from New Bedford Harbor, Mass./U.S.A., and from the southern German Bight in the North Sea are described in more detail. Chemical extraction procedures are used to evaluate different forms of metal associations in aquatic sediments: (i) heavy metals are transported and deposited as major, minor and trace constituents in the natural rock detritus, mostly in inert positions; (ii) slight alkalinity in sea water results in the formation and precipitation of hydroxides, carbonates, sulphides and phosphates of heavy metals; (iii) sorption and cation exchanges takes place in particular on fine-grained substances with large surface areas, e.g. on manganese dioxide, humic acids, hydrous iron oxides and clay minerals; (iv) organic substances play an important role in the transfer of metals between dissoved and solid phases, particularly by the process of flocculation; (v) under oxidizing conditions, the redox-sensitive Fe- and Mn-hydroxides and -oxides are significant “sinks” of heavy metals in aquatic systems. The characteristic rise in the residual content of lead, copper and cadmium in the polluted samples points toward the strong influence of atmospheric dust particles. Heavy metals immobilized in the bottom sediment constitute a potential hazard to water quality and aquatic life since they may be released as a result of chemical changes. In relation to the marine environment, the following mechanisms should be taken into account: (i) increased salinities at the inflow of rivers into the sea water will affect the partial exchange of metal cations sorbed onto the surface of suspended particles; (ii) oxygen deficiency in the bottom sediments may lead to the dissolution of hydrous iron and manganese oxides and to a release of co-precipitated heavy metals; (iii) complexing substances of both natural and synthetic origin increases the solubilization of metals; (iv) microbial activities can convert inorganic metal compounds to organic molecules and may thereby increase toxicity, as exemplified in organo-mercurial transformations.