Showing papers on "Trace metal published in 1994"

Evaluation of a sequential extraction procedure for the determination of extractable trace metal contents in sediments

Abstract: The determination of extractable trace metals in sediments using sequential extraction procedures has been performed in many laboratories within the last ten years in order to study environmental pathways (e.g. mobility of metals, bounding states). However, the results obtained by different laboratories could hardly be compared due to lack of harmonized schemes. Owing to the need for standardization and subsequent validation of extraction schemes for sediment analysis, the Measurements and Testing Programme (formerly BCR Programme) of the European Commission has organized a project to adopt a sequential extraction procedure that could be used as a mean of comparison of data of extractable trace metals in sediments. A scheme was designed after a series of investigations on existing schemes and tested in interlaboratory studies. This paper presents the results of two round-robin exercises on extractable trace metals using this sequential extraction protocol and describes the final version of the extraction procedure amended according to the most recent improvements.

Metal Speciation and Contamination of Soil

Abstract: Land Contamination by Metals-Global Scope and Magnitude of Problem, U. Forstner Kinetics of Metal Sorption Reactions, D.L. Sparks Implications of Complexation, Sorption, and Dissolution Kinetics for Metal Transport in Soils, J.G. Hering Colloidal Transport of Metal Contaminants in Groundwater, L. Liang and J.F. McCarthy Redox Reactions in Phyllosilicates and Their Effects on Metal Transport, J.W. Stucki, G.W. Bailey, and H. Gan Detection of Anionic Sites on Bacterial Walls, Their Ability to Bind Toxic Heavy Metals and Form Sedimentable Flocs and Their Contribution to Mineralization in Natural Freshwater Environments, T.J. Beveridge, S. Schultze-Lam, and J.B. Thompson Trace Metal Chemical Reactions in Groundwater: Parameterizing Coupled Chemistry Transport Models, T.L. Theis and R. Iyer Assessment of Metal Mobility in Soil-Methodological Problems, W.W. Wenzel and W.E.H. Blum Vibrational and NMR Probe Studies of SAz-1 Montmorillonite, C.T. Johnston, W.L. Earl, and C. Erickson Treatment of Soils Contaminated with Heavy Metals, R.W. Peters and L. Shem Effect of Mine Waste on Element Speciation in Headwater Streams, M.C. Amacher, R.W. Brown, R.C. Sidle, and J. Kotuby-Amacher Assessment of Metal Contaminants Dispersed in the Aquatic Environment, J. Liu, H. Tang, Y. Lin, and M. Mao Application of Inorganic-Contaminated Groundwater to Surface Soils and Compliance with Toxicity Characteristic (TCLP) Regulations, C.L. Bergren, M.A. Flora, J.L. Jackson, and E.M. Hicks Conclusions References

Nutrient and metal accumulation in a freshwater tidal marsh

Abstract: Stratigraphic records from sediment cores collected in a freshwater tidal marsh and in the estuary upstream and downstream from the marsh were used to determine the accumulation of nutrients and trace metals over long time periods. Analysis of pollen and seeds show that the high marsh has formed only within the past 100 yr, following increased sedimentation rates in the area. Variations in nutrient and trace metal accumulations over several decades show that pollutants from agricultural runoff and wastewater discharge are stored to a greater extent in high-marsh than in low-marsh sediments. Greater accumulation rates in the high marsh are probably related to its greater sedimentary organic carbon concentration.

Trace Metals as Tracers of Dredging Activity in Cleveland Bay - Field and Laboratory Studies

Abstract: This study has investigated in detail trace metal concentrations in Cleveland Bay in the central Great Barrier Reef and assessed the significant carrier phases of several metals during a simulated disturbance of sediments designed to investigate the effects of dredging. Organic, iron oxide and carbonate phases were shown to be important carrier phases for several trace metals. The application of an acid-leach technique to monitor labile or pollutant concentrations of copper, zinc, lead and nickel in sediments collected from coral reefs sampled before and after two dredging events in 1991 yielded useful information on the fate of dredged sediment. Trace metal contamination close inshore was attributed to port activities, sewage discharge and urbanization.

Solubilities of Al, Pb, Cu, and Zn in rain sampled in the marine environment over the North Atlantic Ocean and Mediterranean Sea

Abstract: Chemical processes controlling the dissolved and particulate phase distribution of crustal (Al) and noncrustal metals (Pb, Cu, and Zn) appear to differ in marine precipitation sampled over the North Atlantic Ocean and Mediterranean Sea. Dissolved Al appears to be in equilibrium with a trivalent Al salt at rainwater pH 80% of the total Pb, Cu, and Zn concentrations are delivered to the surface oceans in the dissolved form. For a corresponding pH range, Al solubility varies from 60%. Over the wider observed pH range (of 3.5 to 6.9), the solubilities of Pb, Cu, Zn, and Al are highly variable. The use of mean trace metal solubilities for the assessment of dissolved atmospheric trace metal wet deposition fluxes, and their effects on surface ocean biogeochemistry should be constrained by taking into account rainwater pH in future estimates in global models.

A 50-yr Record of Pollution by Nutrients, Trace Metals, and Organic Chemicals in the St Lawrence River

Abstract: The deposition chronology of algal pigments, organic C, N, P, trace metals, and organic contaminants (PCB congeners, DDD, DDE, Mirex, hexachlorobenzene) is described for two sites in fluvial lakes (St. Francis and St. Louis) of the St. Lawrence River. Pigment concentrations rapidly decrease in the top 10 cm due to degradation, but show a broad secondary peak consistent with higher primary productivity between 1960 and 1975. In Lake St. Francis, deposition of organic C, N, and P peaked between 1950 and 1975. In both lakes, trace metal concentrations reached maximum values between 1960 and 1970 and decreased considerably between 1970 and 1980. At both sites, surficial trace metal concentrations are approaching (within a factor of 3) those observed in preindustrial sediments except Cd, which is still 5–6 times higher. Concentrations of Cr, Cu, Ni, and Zn are inversely related (p < 0.05) to river discharge whereas those of Pb are positively related to discharge. Concentrations of organic contaminants have dec...

Trace Metal/Phytoplankton Interactions in the Sea

Abstract: Recent evidence indicates that trace metal nutrients (most importantly iron, and to a lesser extent zinc and manganese) can profoundly influence the productivity, species diversity, and ecological interactions of marine phytoplankton communities. In this chapter, several aspects of marine trace metal/phytoplankton interactions are examined, including (1) the chemistry of bioactive metals in seawater, (2) the interaction of these metals with phytoplankton at the molecular, cellular, community, and ecosystem levels of biological organization, and (3) the mechanisms by which phytoplankton communities regulate the distributions, cycling, and chemical speciation of trace metals. In controlling the chemistry and cycling of metal nutrients, important feedback mechanisms are established, which can have global scale impacts on the physics, chemistry, and biology of the Earth.

Study of the stability of extractable trace metal contents in a river sediment using sequential extraction

Abstract: Sequential extraction schemes have been used in recent years to study the environmental behaviour of trace metals present in soils and sediments. Owing to the variety of the different extraction procedures, the results obtained were not comparable as they were highly dependent on the procedure. Moreover, the lack of suitable reference materials for this type of analysis prevents quality control of the measurements. In 1987 the Community Bureau of Reference (BCR, now Measuring and Testing Programme) started a programme to harmonize the methodology and to produce certified reference materials. This paper presents the work carried out to prepare a river sediment sample to be analysed in an intercomparison exercise using a common sequential extraction scheme adopted at Sitges by a group of European experts. The studies of homogeneity and stability with time of the extractable trace metal contents in the sample are also reported.

Processes influencing the fate of trace metals in the North Sea

Abstract: Measurements were made in the southern North Sea of trace metals (dissolved and particulate Mn, Fe, Ni, Co, Cu, Zn, Cd, Pb) with contrasting biogeochemical behaviours. The extent to which distributions of dissolved metals over the survey area were determined by the mixing of river waters with seawater varied among the metals, and also seasonally; even for nickel and copper, which behaved most conservatively, other processes were significant. Specific instances of the effects of scavenging by particles and of inputs from benthic recycling are evident from the data and these processes lead generally to modifications of fluxes of dissolved metals in estuarine plumes. While the effect of atmospheric inputs on dissolved concentrations of metals is, on the basis of other evidence, a factor contributing to spatial and temporal variability, specific features arising from them were not identified; they probably account, however, for increased concentrations of dissolved lead observed at high salinities in the Humber plume. Seasonal variations in concentrations of dissolved metals, paralleling those of micronutrients, were not identified but manganese showed a pronounced seasonal variability related to its reduction-oxidation chemistry. Wide differences occurred in the partition between dissolved and particulate fractions, although for copper and zinc the partition could be described by a narrow range of distribution coefficients under certain conditions.

Tidal River Sediments in the Washington, D.C. Area. I. Distribution and Sources of Trace Metals

Abstract: Thirty-three bottom sediments were collected from the Potomac and Anacostia rivers, Tidal Basin, and Washington Ship Channel in June 1991 to define the extent of trace metal contamination and to elucidate source areas of sediment contaminants. In addition, twenty-three sediment samples were collected directly in front of and within major storm and combined sewers that discharge directly to these areas. Trace metals (e.g., Cu, Cr, Cd, Hg, Pb, and Zn) exhibited a wide range in values throughout the study area. Sediment concentrations of Pb ranged from 32.0 μg Pb g−1 to 3,630 μg Pb g−1, Cd from 0.24 μg Cd g−1 to 4.1 μg Cd g−1, and Hg from 0.13 μg Hg g−1 to 9.2 μg Hg g−1, with generally higher concentrations in either outfall or sewer sediments compared to river bottom-sediments. In the Anacostia River, concentration differences among sewer, outfall, and river sediments, along with downriver spatial trends in trace metals suggest that numerous storm and combined swers are major sources of trace metals. Similar results were observed in both the Tidal Basin and Washington Ship Channel. Cadminum and Pb concentrations are higher in specific sewers and outfalls, whereas the distribution of other metals suggests a more diffuse source to the rivers and basins of the area. Cadmium and Pb also exhibited the greatest enrichment throughout the study area, with peak values located in the Anacostia River, near the Washington Navy Yard. Enrichment factors decrease in the order: Cd>Pb>Zn>Hg>Cu>Cr. Between 70% and 96% of sediment-bound Pb and Cd was released from a N2-purged IN HCl leach. On average, ≤40% of total sedimentary Cu was liberated, possibly due to the partial attack of organic components of the sediment. Sediments of the tidal freshwater portion of the Potomac estuary reflect a moderate to highly components area with substantial enrichments of sedimentary Pb, Cd, and Zn. The sediment phase that contains these metals indicates the potential mobility of the sediment-bound metals if they are reworked during either storm events or dredging.

Distribution of trace metals in sediments and the relationship with their accumulation in earthworms

Abstract: Concentrations of Cd, Pb, Cu and Zn and their speciation in river sediments (Guadalquivir River, Spain), were determined. Relationships between trace metal concentrations in sediments and earthworms were studied in order to estimate the rate at which metals accumulated in organisms living in sediments. The bioavailable fraction of Cd represented more than 50 % of the total Cd found in sediments, and this percentage was much greater than those of the other elements examined. Most of the Cu was present in the organic and residual fractions. Lead and Zn were mainly associated with the crystalline iron oxide fraction. The application of factorial analysis to the total heavy metal concentrations and some soil properties reduced the number of original variables to only three, namely factors, which explained the total variance of 94 %. Metals accumulated in earthworms were related by a second grade polynomial equation with fractions where the metals were mainly bound. Cd exhibited the highest accumulati...

Trace metal solid state speciation changes associated with the down-column fluxes of oceanic particulates

Abstract: The ‘global carbon flux’, which is dominated by large-sized organic aggregates, removes dissolved trace metals from sea water and delivers suspended particulate material to the sediment surface. Dissolved trace metals sequestered by the sinking particulates can have different speciation signatures; for example, Cu is removed principally via an organic association, whereas Mn is mainly scavenged via an inorganic surface association involving small particles which are ‘dragged down’ by the aggregates. The trace metal speciation signatures in suspended particulate material appear to be similar on a global ocean basis, but once the particulates reach the sediment surface they are subjected to a variety of processes which are constrained by the depositional environment, especially the redox conditions. In some marginal hemi-pelagic deposits the original suspended particulate trace metal speciation signatures can be retained in the buried sediment, but in open-ocean pelagic sediments deposited under oxidizing conditions the particulates suffer severe modification as the organic carbon in the sinking aggregates is destroyed during oxic diagenesis. The solid state speciation signatures of trace metals reflect these modifications, and so can be used as ‘tracers’ to monitor the chemical changes affecting particulate material incorporated into deep-sea sediments via the ‘global carbon flux’. This is illustrated with respect to the speciation signatures of Fe, Cu and Mn in surface sea water particulates and deep-sea sediments from the Atlantic Ocean.