Fractionation Of Metals In Sediments Research Articles

Characteristics and accumulation of heavy metals in sediments originated from an electroplating plant

Heavy metals in river water and sediments originated from an electroplating plant in Jiangsu Province of China were studied and analyzed for their environmental impact. The results indicated that the wastewater from the plant degraded the quality of the aquatic environment downstream from the plant. In surface water, considerable concentrations of Cu, Ni, Zn, Mn and Cr were present at the sites near the plant. Unsafe levels of Cu were observed at all sites, and unsafe levels of Ni, Zn, and Cr were present at some sites. Significant accumulation of Ni, Cu, Zn and Cr was identified, and heavy metal longitudinal distribution in sediments was similar to that in water. The contents of Ni, Cu and Cr at all sites and Zn at some sites were likely to result in harmful effects on the environment. The risks posed by Ni, Cu, Zn and Cr in water and sediments decreased with increasing downstream distance. Moreover, a modified sequential extraction procedure was employed to determine exchangeable, carbonate-bound, iron–manganese oxide bound, organic matter bound and residual fractions of metals in sediments. The results showed that Ni was distributed in every fraction except for iron–manganese oxide bound, significant Mn exhibited in exchangeable fractions, and high percentage of Cu was in the organic matter and residual fractions. Residual fraction was the dominant fractions for Pb and Zn. According to RACs, Ni and Mn posed a high risk to the environment, Zn exhibited medium to high risk, Cu had low to high risk, and Pb possessed a low to medium risk.

Relationships of Heavy Metals in Natural Lake Waters with Physico-chemical Characteristics of Waters and Different Chemical Fractions of Metals in Sediments

The relationships between heavy metal concentrations and physico-chemical properties of natural lake waters and also with chemical fractions of these metals in lake sediments were investigated in seven natural lakes of Kumaun region of Uttarakhand Province of India during 2003–2004 and 2004–2005. The concentrations of Cr, Mn, Fe, Ni, Cu, Zn, Cd and Pb in waters of different lakes ranged from 0.29–2.39, 10.3–38.3, 431–1407, 1.0–6.6, 5.3–12.1, 12.6–166.3, 0.7–2.7 and 3.9–27.1 μg l−1 and in sediments 14.3–21.5, 90.1–197.5, 5,265–6,428, 17.7–45.9, 13.4–32.0, 40.0–149.2, 11.1–14.6 and 88.9–167.4 μg g−1, respectively. The concentrations of all metals except Fe in waters were found well below the notified toxic limits. The concentrations of Cr, Mn, Ni, Cu, Zn, Cd and Pb were positively correlated with pH, electrical conductivity, biological oxygen demand, chemical oxygen demand and alkalinity of waters, but negatively correlated with dissolved oxygen. The concentrations of Cr, Ni, Zn, Cd and Pb in waters were positively correlated with water soluble + exchangeable fraction of these metals in lake sediments. The concentrations of Zn, Cd and Pb in waters were positively correlated with carbonate bound fraction of these metals in lake sediments. Except for Ni, Zn and Cd, the concentrations of rest of the heavy metals in waters were positively correlated with organically bound fraction of these metals in lake sediments. The concentrations of Cr, Mn, Ni, Cu and Zn in waters were positively correlated with reducible fraction of these metals in lake sediments. Except for Cd, the concentrations of rest of the metals in waters were positively correlated with residual fraction and total content of these heavy metals in lake sediments.

Multi-way data modeling of heavy metal fractionation in sediments from Gomti River (India)

This study presents analysis of the multi-way data set obtained through the sequential extraction procedure based fractionation of thirteen heavy metals/elements in three different particle sizes of the river bed sediments collected from ten different sites. The three-way (sampling sites, elements, particle size-bound elemental fractions) data set was analyzed using multi-way (three-way) component analysis method to evaluate the associations of heavy metals and their chemical fractions with the particle sizes of river sediments and their spatial distribution. A multi-way component analysis was performed using the Tucker3 model. The two-way PCA could not extract information about the behaviour of sampling sites and distribution pattern of metals with particle size. The three-way Tucker3 model applied to the three-dimensional data set allowed to visualize information about the three ways that could be interpreted jointly. The constructed three-way Tucker3 model (3,2,3) capturing about 46.34% of the data variance successfully provided in-depth information about the sampling sites, elements, particle size-bound elemental fractions and their distribution in different particle sizes of the river bed sediments. It allowed the interpretation of the metals’ fractionation data in all three modes.

Heavy metals in Hediste diversicolor (polychaeta: nereididae) and salt marsh sediments from the lagoon of Venice (Italy)

The nereid polychaete Hediste diversicolor was frequently used as biomonitor of heavy metals contamination in estuaries. In the present work, the bioaccumulation of five heavy metals (Cd, Cr, Cu, Mn, Pb) in tissues of H. diversicolor collected from six salt marshes in the lagoon of Venice is studied by analysing the relationships between concentrations of the operationally-defined reactive fraction of trace metals in sediments and total concentrations in tissues. The characterisation of sediment samples shows a clear distinction between sites near and far from the Industrial Zone; no analogous pattern is observed for tissue concentrations suggesting that metal bioaccumulation is controlled by complex interactions between metal bioavailability and physiological factors. Considering relationships between metals, strong inverse correlations are observed in polychaetes and sediments for Cu and Cr concentrations suggesting a possible interaction between these two metals. The role played by organic matter (OM) in the availability of metal is highlighted considering inverse relationships found between bioaccumulation factors for Cu, Cr, Cd and OM.

Release, bioavailability and toxicity of metals in lacustrine sediments: A case study of reservoirs and lakes in Southeast Brazil

Bioavailability and toxicity of metals in sediment were assessed in three water bodies in the State of São Paulo, SE Brazil, in one of the first investigations of the topic in the country. Weakly bound metals in bulk sediment samples taken from a highly-polluted reservoir, Billings, São Paulo, exhibited enrichment factors from 2.4 to 30 fold, compared to two other water bodies in the study, Barra Bonita Reservoir and Diogo Lake. High mortality rates occurred when Hyalella azteca and Ceriodaphnia dubia were exposed to Billings reservoir sediment. After forty-eight days of sediment oxidation, laboratory microcosms showed increases in the weakly-bound fraction of metals in sediments from Billings Reservoir (all metals), Diogo Lake (all metals except Zinc) and Barra Bonita Reservoir (Cadmium and Lead only). Chironomus xanthus was not sensitive to toxicity in sediment from any of the three environments. Ceriodaphnia dubia was sensitive to chronic toxicity in bulk field sediments from all three environments, and showed an increase in mortality rate in tests with oxidized sediment. Billings sediment, with or without aeration, caused 100 percent mortality, while in contact with Barra Bonita field sediment, a mortality of 10 percent of the adult organisms occurred, increasing up to 80 percent in post-aeration sediments. In Diogo Lake sediment, 30 percent mortality was observed in field or pre-aeration sediment rising to up to 60 percent in post aeration sediments. The two factors caused by oxidation of reduced substances in sediments, a fall in pH in the water and mobilization of bound metal, are invoked to explain this response.

Copper and other trace elements strongly bound to humic acids along sediment cores in the Ross Sea, Antarctica

Marine sediment cores sampled in three different areas, during the 1997/98 Italian Antarctic Expedition, were studied. The cores (40 cm) were immediately subdivided into 13 or 14 layers (2-4 cm) in order to obtain a high-depth resolution in the metal content and humic substance analyses. The results obtained for the amount of metals strongly bound to humic acids showed the following order: Cu >> Zn >> Co > As >or= Mn. The fraction of Cu, Zn and As bound to humic acid (microg g(-1) of HA) increases in the first 10-12 cm of cores, then a decrease is observed. This observation could be related both to the presence of a mobile fraction of metals in sediments successively bound to humic acids and to different structural features showed by humic acids along the cores, due to transformation processes. For the other metals a variable pattern along the cores was found.

Influence of the sea rush Juncus maritimus on metal concentration and speciation in estuarine sediment colonized by the plant.

Metal accumulation by Juncus maritimus and the role of this plant on the physical and chemical composition of sediments, from the Douro river estuary (NW Portugal), were investigated. The contents of Cd, Cr, Cu, Fe, Mn, Ni, Pb, and Zn were determined (by atomic absorption spectrophotometry) in sediments, rhizosediments (those among plant roots and rhizomes), and different plant tissues (roots, rhizomes, leaves, and stems). Metal fractionation in sediments through sequential extraction was carried out and used for interpretation of sediment/J. maritimus interactions. Two estuarine sites with different characteristics were studied: site I displayed sandy sediment with lower organic matter and metals more weakly bound to it than site II sediment, which was muddy. At both sites, higher metal contents were observed in rhizosediments than in the surrounding sediment, but metals were more weakly bound to rhizosediment. Therefore, J. maritimus markedly influenced the sediments among its roots and rhizomes, changing metal distribution and speciation. Different patterns of both metal uptake and metal distribution among J. maritimus tissues were observed at the two sites. Plant bioaccumulation was only observed for Cd, Cu, and Zn, being similar for Cd atthe two sites and significantly higher for Cu and Zn (9 and 4 times higher, respectively) at site I. In conclusion, J. maritimus was shown to have potential for phytoextraction (or phytostabilization) of Cd, Cu, and Zn in estuarine environment. However, an eventual application of J. maritimus for this purpose will require a periodic removal of the plants together with their own rhizosediment.

Application of sequential extraction with supercritical CO(2), subcritical H(2)O, and an H(2)O/CO(2) mixture for estimation of environmentally mobile heavy metal fractions in sediments.

Results from use of a new isolation procedure based on sequential extraction with supercritical CO(2), subcritical H(2)O, and an H(2)O/CO(2) mixture in the same supercritical fluid extractor have been compared with results from the BCR-recommended three-step sequential extraction procedure. The new procedure gives more detailed information about environmentally mobile fractions (water-soluble, bicarbonate-forming), and in less time (5-6 h), than the BCR procedure.

Heavy Metal Fractionation in Sediments from the Tinto River (Spain)

Seventeen sediment samples from the Tinto and its main tributaries were analyzed for this study. For each of these samples, the association of metals (Cu, Zn, Cd, Pb, Fe, Ni, Cr and Co) was determined in four fractions: acid soluble, reducible, oxidizable and residual. The total metal content was also determined. Results showed high mean concentrations of Fe (109,000 mg/kg), Pb (2330 mg/kg), Zn (901 mg/kg), Cu (805 mg/kg), and Cd (2.7 mg/kg) in the sediments studied. However, the mean values found for Co (21 mg/kg), Cr (56 mg/kg) and Ni (17 mg/kg) are comparable to those in unpolluted areas. Heavy metal fractionation of the Tinto River sediments showed that the metals with the greatest mobility (i.e., metals that could pass easily into the water under changing environmental conditions) are Cd and Zn. These are the metals that showed the highest percentages in the first two fractions (the most labile) and the lowest percentages in the residual fraction. However, the percentage of metal present in the fourth fraction (residual) was high for Cr (78%), Ni (71%), and Co (66%), which implies that these metals are strongly linked to the sediments.

Effects of spatial and temporal variation of acid‐volatile sulfide on the bioavailability of copper and zinc in freshwater sediments

AbstractVariation in concentrations of acid‐volatile sulfide (AVS) in sediments from the upper Clark Fork River of Montana, USA, was associated with differences in bioaccumulation of Cu and Zn and growth of larvae of the midge, Chironomus tentans. Growth of midge larvae was significantly greater and bioaccumulation of Cu was significantly less in surface sections (0–3 cm depth) of sediment cores, which had greater concentrations of AVS and lesser ratios of simultaneously extracted metals to AVS (SEM:AVS ratios) than in subsurface sediments (6–9 cm). Concentrations of AVS were significantly less in sediments incubated with oxic overlying water for 9 weeks than in the same sediments incubated under anoxic conditions. Bioaccumulation of Cu differed significantly between incubation treatments, corresponding to differences in concentrations of AVS and SEM:AVS ratios, although midge growth did not. Bioaccumulation of Zn did not differ significantly between depth strata of sediment cores or between incubation treatments. When results from the two sets of bioassays were combined, bioaccumulation of Cu and Zn, but not growth, was significantly correlated with SEM:AVS ratios and other estimates of bioavailable metal fractions in sediments. Growth of midge larvae was significantly correlated with bioaccumulation of Zn, but not Cu, suggesting that Zn was the greater contributor to the toxicity of these sediments. Assessments of the toxicity of metal‐contaminated freshwater sediments should consider the effects of spatial and temporal variation in AVS concentrations on metal bioavailability.

Studies on redistribution during the analytical fractionation of metals in sediments

This paper examines a commonly used procedure for fractionation of metals in sediments, in order to determine whether redistribution of elements from one phase to another occurs during the extraction steps. Pure synthetic phases were added to portions of the sediments in order to provide fresh unoccupied sites for retention of any metals released during extraction. The spiked sediments along with an unaltered sample were subjected to the fractionation procedure and results compared. No redistribution occurred for cadmium, copper or nickel. Some limited redistribution to oxide and organic phases was observed for chromium, lead and zinc. A large shift of manganese from the exchange complex to other phases was found for all samples. It is concluded that some redistribution does occur during the procedure and it would be difficult to quantify the extent. However, for most elements redistribution may not be sufficiently large to invalidate the method.