Showing papers on "Trace metal published in 1987"

Accuracy of selective extraction procedures for metal speciation in model aquatic sediments

Abstract: The interpretability of a selective extraction procedure for metals in aquatic sediments was tested by means of synthetic models. The major sedimentary geochemical phases were prepared and characterized by X-ray diffraction and scanning electron microscopy. A specific trace metal was doped into each phase by adsorption or coprecipitation, content being verified by atomic absorption (AA). The phases and metals were calcite (Pb), iron sulfides (zn), humic acid (Cu), and iron oxyhydroxides (Cu or Ni). Three different model sediments were prepared by combining phases and diluting with silica or illite. Measurements of extracts by AA and inductively coupled plasma (ICP) indicated that trace metals were not recovered in the appropriate fractions. This implies that selective extraction procedures as currently practiced may not be suitable for distinguishing the phase association of metals in real sediments.

Partitioning of trace metals in sediments: Relationships with bioavailability

Abstract: As a result of complex physical, chemical and biological processes, a major fraction of the trace metals introduced into the aquatic environment is found associated with the bottom sediments, distributed among a variety of physico-chemical forms. As these different metal forms will generally exhibit different chemical reactivities, the measurement of the total concentration of a particular metal provides little indication of potential interactions with the abiotic or biotic components present in the environment. In principle, the partitioning of sediment-bound metals could be determined both by thermodynamic calculations (provided equilibrium conditions prevail) and by experimental techniques. The modelling of sediment-bound metals is far less advanced than is that of dissolved species, primarily because the thermodynamic data needed for handling sediment-interstitial water systems are not yet available. The partitioning of a metal among various fractions obtained by experimental techniques (e. g., sequential extraction procedures) is necessarily operationally defined. These methods have, however, provided significant insight into the physico-chemical factors influencing the bioavailability of particulate trace metals; some of these factors are discussed.

Sediments as a source for contaminants

Abstract: This review article covers the processes affecting trace metals in deposited sediments The sediment-water system can be divided in three parts: the oxic layer, the anoxic layer and the oxic-anoxic interface Available data show that trace metals like Cu, Zn and Cd occur as sulphides in marine and estuarine anoxic sediments Calculations show that organic complexation is unlikely and the dominant species are sulphide and bisulphide complexes Chromium and arsenic are probably present as adsorbed species on the sediments; their concentrations in the pore waters, therefore depend on the concentrations in the sediments The oxic-anoxic interface plays the major role in the potential flux of trace metals from the sediments, however this interface is not well studied at present Changes from an anoxic to an oxic environment as occurs during dredging and land disposal of contaminanted sediments may cause a remobilization of some trace metals

Trace metal geochemistry in the Cariaco Trench

Abstract: Profiles of dissolved Mn, Fe, Co, Ni, Cu and Cd were determined in the Cariaco Trench. Solubility trends are consistent with previous metal studies in axoxic fjords and landlocked seas, and serve as a model for the effects of anoxia in an oceanic regime. Class B metals (Cu and Cd) exhibit nearly quantitative removal in the anoxic water column. Transition metal concentrations (Mn, Fe, Co) initially increase across the O2/H2S interface due to the reductive dissolution of metal oxides, and then decrease at depth because of solid phase uptake. Ni profiles show no comparable response to anoxia, but contrast sharply with Ni profiles of the adjacent Venezuelan Basin. Metals which are observed or predicted to be more insoluble in anoxic water (Cu, Cd, Zn, Pb and Mo) can be expected to be enriched relative to detrital input in the underlying sediments. A box model describing this enrichment flux is used to explain the contrasting sediment enrichment patterns observed in the sediments of the Cariaco Trench and Framvaren Fjord, a highly anoxic fjord in Norway. A sediment enrichment hierarchy (Mo > Cd > Cu > Zn > Pb) is derived that predicts which metals should be the most sensitive indicators of open ocean anoxia.

Trace metal reduction by phytoplankton: the role of plasmalemma redox enzymes

Abstract: The phytoplankton cell surface reduces external copper(II) and iron(III) complexes and redox dyes. This reductive activity appears to be mediated by one or more plasmalemma redox enzymes. Trace metal complexes are directly reduced by the redox enzyme, therefore the reduction rate is not regulated by the metal free ion activity in solution. This is in direct contrast to previous measurements of trace metal interactions with the phytoplankton cell membrane. Half-saturation constants for the reduction of Cu(II) complexes with carbonate, phenanthroline and bathocuproinedisulfonate are in the range 2.3-14.7 ..mu..M, which suggests that trace metal complexes are not the main electron acceptor in natural waters. In the diatom Thalassiosira weissflogii there is additional reductive activity associated with the cell wall.

Atmospheric input of trace metals to the western Mediterranean Sea: 1. Factors controlling the variability of atmospheric concentrations

Abstract: The factors controlling the variability of atmospheric trace metal concentrations over the western Mediterranean Sea have been investigated using a combination of geochemical and meteorological approaches. Al, Br, Cd, Na, Pb and 210Po concentrations from bulk filters and cascade impactor samples collected during five cruises (1980–1983) have been used to characterize the aerosol sources: the marine source (Na), the aeolian soil mobilization (Al), the anthropic sources (Cd, Pb), and the volcanic source (210Po). It has been confirmed that Cd and Pb directly derive from anthropic sources. As shown by three-dimensional air mass trajectory analyses, the variability of daily atmospheric concentrations reflects both changes in continental source strengths and in airflow patterns. Atmospheric concentrations appear to be higher during episodes of short-range transport of continental material from riparian countries. It is suggested that such source regions can be precisely identified by a careful examination of both geochemical data and three-dimensional trajectories. From our data set, southwestern Europe would be responsible for the largest Pb and Cd inputs to the western Mediterranean atmosphere (30–40%), but the inputs from North Africa are also likely to be significant (20–25%). However, it cannot be ascertained whether this conclusion is valid on a yearly time scale. Indeed, whereas our sample set is representative of the yearly airflow climatology, it has not been possible to assess the effect of seasonal (for Pb) or sporadic (for Al) changes in source strengths. This points out that over such a marine environment, continuous sampling programs are needed to assess the respective contributions of individual source regions to the atmospheric burden of particulate trace elements.

Micronutrient effects on cyanobacterial growth and physiology

Abstract: Trace metals play crucial roles in the carbon and nitrogen metabolism of cyanobacteria. Physiological responses to metal limitation and toxicity in culture have shown that iron is important for photosynthesis and energy distribution in the cell while both iron and molybdenum are biochemically involved in nitrate reduction and nitrogen fixation. Nitrogen fixation is also relatively sensitive to copper toxicity. Consequently, factors that affect the supply rate, chemical speciation, or the recycling of trace metals can alter patterns of primary productivity and nitrogen metabolism. Overall, three trace metal dependent processes may contribute towards dominance: efficient use of limiting light, nitrogen fixation, and production of extracellular iron binding compounds.

A method for the collection, handling, and analysis of trace metals in precipitation.

Abstract: A method is described for the automated collection, proper handling, and accurate analysis of trace metals (Fe, Zn, Cu, Mn, Pb, Cd, Ni, V) in precipitation. The method has been successfully used in both rural coastal (Lewes, DE) and semiremote (Bermuda) marine environments but should be generally applicable. The collection device is a commercially modified automatic collector with polyethylene bag liners in the collecting buckets. Strict protocols for acid washing, deployment, and blanking are necessary to ensure accurate contamination-free samples. The freshly collected event samples are postacidified below pH 1.6 with ultraclean HCl to ensure desorption and preservation of the sample. Trace metal concentrations are quantitatively analyzed by heated graphite atomization in an atomic absorption spectrophotometer. A comparison of the results obtained by this method with earlier published trace metal results suggest that serious sampling and analytical artifacts may be present in most earlier data bases. 24 references, 5 table.

Sediment trace metal contamination in the Ivory Coast, West Africa

Abstract: To help expand our global perspective on trace metal contamination, concentrations of Cu, Fe, Hg, Mn, Ni, Pb, and Zn were determined for sediments from the Ebrie Lagoon in the Ivory Coast, a developing West African nation. Excess loading of several metals, especially Hg, Pb, and Zn was found at several sites. The maximum concentration of Hg measured in sediments from the Ebrie Lagoon (2250 ng g−1) is about 30 times greater than natural levels. Similarly, Pb and Zn concentrations for the Ivorian lagoonal sediments are as high as 250 and 560 μg g−1, respectively, showing sizeable anthropogenic inputs. Trace metal sources to the Ebrie Lagoon include untreated sewage and industrial wastes.

A comparison of atmospheric inputs and deep-ocean particle fluxes for the Sargasso Sea

Abstract: Trace metal distributions in ocean waters are dominated by internal recycling processes. However, fluxes out of the water column must balance inputs if steady state is to be maintained. We use deep-sea particle fluxes at 3200 m in the Sargasso Sea as measured by sediment traps to define the flux to the sediments beneath the Sargasso Sea and compare this flux to the atmospheric input for a group of trace metals. Despite the uncertainties associated with the comparison, several important features are revealed. For elements predominantly associated with crustal particles (Al, Mn, Fe, and V), lateral advection provides a significant part of the deep-sea particle flux. For Cd, Cu, Ni, Pb, and Zn this lateral component is minor, and atmospheric inputs to the Sargasso Sea exceed deep-sea particle fluxes. These excesses appear to be consistent with calculations of the export of these metals from the Sargasso Sea arising from ocean boundary scavenging (Pb) and release from decomposing organic matter in the southward flowing North Atlantic Deep Water (Cd, Cu, Ni, and Zn). In the atmospheric deposition itself, wet deposition exceeds dry deposition for Cd, Cu, Mn, Ni, Pb, and Zn, while wet and dry deposition are of similar magnitudes for V, Fe, and Al.

A hydrogen-peroxide digestion system for tissue trace-metal analysis.

Abstract: Tissue digestion prior to analysis for trace metals is usually carried out with strong acids. Nitric acid, alone or in combination with perchloric acid, is most commonly used. In addition to the laborious acid washing of all glassware prior to use, the digestion necessitates exposure to potential environmental contamination. Use of perchloric acid mandates a specially constructed hood with facilities for washing to remove acid deposits. A simple digestion procedure using 30% hydrogen peroxide in polyethylene vials in an oven at approximately 75°C has been previously described for the measurement of zinc in tissues using flame or flameless atomic absorption spectrophotometry and of selenium in liver by flameless atomic absorption. Readings for reagent blanks were insignificant. The technique has been further developed with a reduction in digestion time using 50% H2O2. Analysis of liver has been extended to include copper, manganese, and arsenic. Although the level of arsenic present was too low to be detected, 50 and 100 ng of this element added to the liver powder was completely recovered. The digest obtained when dissolved in appropriate solvent is suitable for analysis for multiple trace metals.

Comparison of trace metal concentrations in muscle tissue of a benthopelagic fish coryphaenoides armatus from the atlantic and pacific oceans

Abstract: Specimens of Coryphaenoides armatus , a benthopelagic fish, were collected from the North Atlantic and North Pacific for trace metal analysis. Concentrations of cadmium and lead in muscle tissue of Atlantic fish were not significantly different from those of Pacific fish. Differences in copper concentrations in the two groups may be related to size difference. Higher concentrations of nickel, cobalt, iron and manganese observed in muscle tissue from the Pacific fish may be due to differences in fish size and differences in deep water metal chemistry between the two oceans.

Metal speciation in solid wastes — Factors affecting mobility

Abstract: The availability of trace metals for metabolic processes is closely related to their chemical species both in solution and in particulate matter. For the differentiation of the solid metal species — e.g., cation exchangeable forms, carbonate phases, reducible fractions, associations with organic substances and sulfides, and the inert “residual” fractions — chemical extraction sequences have been developed, which can be used for (i) assessment of sources by characterization of typical speciation patterns, (ii) estimation of biological availability of metal pollutants, (iii) differentiation of geochemical environments, (iv) evaluation of diagenetic effects, and (v) estimation on the potential remobilization of metals under changing environmental condition. There is a tendency, that elements introduced with solid waste material are less stably bound than those in natural systems. Even at relative small proportions of these materials, therefore, mobilization (and subsequent transfer to biota) of potentially toxic elements by acidity, complexing agents, or redox changes, may be significantly increased.

Electrochemical preconcentration of metals using mercury film electrodes followed by electrothermal vaporization into an inductively coupled plasma and determination by atomic emission spectrometry.

Abstract: The production and use of mercury film electrodes for matrix separation and preconcentration of trace metals from biological materials prior to their determination by inductively coupled plasma atomic emission spectrometry (ICP-AES) are described. Separation and preconcentration are achieved by controlled potential electrolysis on mercury-plated, glassy carbon electrodes. Electrodes with trace metal amalgam are transferred to an electrothermal vaporization device, the mercury is removed by evaporation, and the metals are then evaporated and determined simultaneously by ICP-AES. The method is applied to the determination of eight trace elements, Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn, in water solution and in the biological standard reference materials urine and bovine liver. The method precision varied between 3.8 and 8.1%.

Size- and age-specific patterns of trace metal concentrations in freshwater clams from an acid-sensitive and a circumneutral lake

Abstract: We collected freshwater clams (Elliptio complanata) from an acid-sensitive and a circumneutral lake in south central Ontario and compared tissue metal concentrations. Clams from the acid-sensitive lake had higher concentrations of Cu and Cd and lower concentrations of Zn and Mn than clams from the circumneutral lake. Tissue concentrations did not reflect metal levels in the water. Competition may be occurring between metals for binding substrate in clam tissue. Clam size and (or) age successfully predicted tissue metal concentrations, but in a metal-specific and tissue-specific manner. Clam biomonitoring studies should therefore control for size and age variability. Lake buffering capability was not very important in influencing size- and age-specific patterns of tissue metal concentrations. However, this conclusion is based solely on data from two lakes.

Trace metals in precipitation in Sweden

Abstract: Trace metals (Cd, Cu, Fe, Mn, Pb, and Zn) concentrations in atmospheric precipitation have been routinely monitored in Sweden since the autumn of 1983. Concentrations are highest in southern Sweden and decrease northward. It is postulated that the long range transport of anthropogenic pollutants from the rest of Europe is the major source of Cd, Pb, and Zn in precipitation. Evidence for this hypothesis is that enrichment factors indicate anthropogenic origin, and Swedish atmospheric emissions of Zn and Cd are 2 to 3 times smaller than deposition fluxes. Also, Cd, Pb, and Zn concentrations are correlated in both space and time and are also well correlated with exSO4+, a substance known to be of anthropogenic origin transported long distances.

Trace metal uptake and accumulation in trees as affected by environmental pollution

Abstract: Regional-scale increases in combustion of fossil fuels, trace metal deposition profiles in lake sediments, and metal accumulation patterns in forest soils suggest that forests have been exposed to increasing levels of trace metals in recent decades Such increases are of concern because metals such as Al, Cd, Cu, Fe, Mn, Ni and Zn typically have long residence times in soil-plant systems and can adversely affect plant physiological and litter decomposition processes at sufficiently high concentrations Chronic effects of these metals at present regional concentrations are largely unknown, and their increased availability to trees can occur through multiple pathways, most of which are poorly characterized Our surveys of changes in tree-ring chemistry of conifers show that increased tissue concentrations of some metals are quite similar to temporal increases in local and regional fossil fuel combustion, suggesting a relationship between the two Highest metal concentrations in tree rings were found near a power plant and at high-elevation sites remote from point sources Levels of many trace metals, particularly Al, Fe, and Mn, in tree phloem tissues are at or exceed levels reported as toxic thresholds in other plant species In reviewing the literature, it is clear that toxic thresholds are strongly influenced by soil characteristics, plant species, and plant part Thus, until more information is obtained on toxic thresholds for individual and combined levels of trace metals on plant physiological and forest ecosystem-level processes, their role, if any, in forest declines must be considered conjectural

Role of Ecklonia radiata (C. Ag.) J. Agardh in determining trace metal availability in coastal waters. I. Total trace metals

Abstract: No seasonal variations were found in the concentrations of Zn, Cd, Cu, K, Ca, Mg and Na in the kelp E radiata collected from the marine-dominated Port Hacking estuary on the east coast of Australia Concentrations of Fe and Mn were about 60% higher in late summer The relative distributions of all metals between different kelp tissues, however, showed no seasonal variation Concentration factors (dry weight basis) for trace metals ranged from 2600 for Cu to 68 000 for Fe With high biomasses common in macroalgal ecosystems, a large proportion of the non-sediment- bound trace metals can be associated with the macroalgae, which therefore act as substantial buffers for these elements Metal concentration factors (Y, wet wt basis) were related to oceanic residence times (τ) by the equation log Y = -069 logτ + 54 The distribution of the aikaii and akaline earth metais (K, Ca, Mg and Na) was relativeiy uniform throughout the various kelp tissues However, concentrations of Fe, Mn, Zn and Cd were significantly higher in the older extremities (holdfast and eroding tip) than in the meristematic region Although the holdfast also had higher levels of Cu than the meristem, levels were lower in the eroding tip The results suggest either a slow net intracellular accumulation of metals with time or an increase in potential metal- binding sites as the extremities senesce Translocation and elimination of surplus metals through the eroding tip or holdfast was thought not to be important in E radiata as metal concentrations did not differ between live and dead haptera of the holdfast Likewise, storage of metals in either the holdfast or eroding tip was considered unlikely because of the constant relative tissue distribution throughout the year and lack of metal mobilization during periods of growth Pretreatment of kelp tissue with an EDTA wash released about 90% of the total Zn and Cd, 25% of the Cu and 7% of the Fe, suggesting that a large proportion of the total kelp Zn and Cd is associated with the apparent free space (AFS) With rapid exchange between seawater and the AFS, E radiata is therefore not generally useful as a sentinel accumulator species in pollution studies for assessing long term integrated changes of metals in the water column

Varietal variation and correlation of trace metal levels with ‚catechins’︁ and caffeine in Sri Lanka tea

Abstract: Trace elements, phosphorus, ‚catechins’ and caffeine levels in different varieties of Sri Lanka tea have been determined. The range and mean of zinc, copper, iron, lead and cadmium in 73 tea samples were as follows: zinc 22.5–62.5 and 35.0 μug g−1, copper 10.0–25.0 and 17.8 μug g−1, iron 40.0–185.0 and 128.1 μug g−1, lead 0.188–0.561 and 0.426 μug g−1, cadmium 0.156–0.380 and 0.239 μug g−1. Significant differences in zinc, iron, lead and cadmium were observed among tea varieties grown at different elevations in Sri Lanka. These levels were also compared with results obtained with samples from other countries. The phosphorus content in ‚black tea’ showed correlations with trace metal levels in the order lead>zinc>iron>copper>cadmium. Positive correlation with levels of ‚catechins’ were more significant with zinc and cadmium. Caffeine levels were found to be significantly correlated with lead and zinc in ‚black tea’. Studies of translocation of trace metals from soil have involved analysis of various parts of the tea shoot and supporting soil.