Trace metal

Abstract: An analytical procedure involving sequential chemicai extractions has been developed for the partitioning of particulate trace metals (Cd, Co, Cu, Ni, Pb, Zn, Fe, and Mn) into five fractions: exchangeable, bound to carbonates, bound to Fe-Mn oxides, bound to organic matter, and residual. Experimental results obtained on replicate samples of fluvial bottom sediments demonstrate that the relative standard deviation of the sequential extraction procedure Is generally better than =10%. The accuracy, evaluated by comparing total trace metal concentrations with the sum of the five Individual fractions, proved to be satisfactory. Complementary measurements were performed on the Individual leachates, and on the residual sediments following each extraction, to evaluate the selectivity of the various reagents toward specific geochemical phases. An application of the proposed method to river sediments is described, and the resulting trace metal speciation is discussed.

Abstract: 1 Introduction.- 2 Interactions with Ligands, Particulate Matter and Organisms.- 2.1 Introduction.- 2.2 Metal Ions in Aquatic Systems.- 2.3 Speciation of Dissolved Metals.- 2.3.1 Physical Separation.- 2.3.2 ASV-Labile Species.- 2.3.3 Ion-Exchange Methods.- 2.3.4 Speciation Schemes.- 2.4 Interaction with Ligands.- 2.5 Interaction with Particulate Matter.- 2.5.1 Sorption Processes.- 2.5.2 Mechanisms.- 2.5.3 Sorption on Metal Oxides and Organic Substances.- 2.5.4 Sorption of Metal-Organic Complexes.- 2.5.5 Interactions in Natural Systems.- 2.6 Solid Speciation.- 2.7 Metal Interaction with Organisms.- 2.7.1 Metal Uptake by Organisms.- 2.7.2 Solid Speciation and Bioavailability.- 2.7.3 Transformation of Metal by Organisms.- 3 Sediments and the Transport of Metals.- 3.1 Introduction.- 3.2 Composition of Sediments.- 3.3 Transport of Sediments.- 3.4 Distribution and Deposition.- 3.5 Grain Size Effects.- 3.6 Anthropogenic Influences on Metal Concentrations in Sediments.- 3.6.1 Background Concentrations.- 3.6.2 Sediment Core Studies.- 3.6.3 Quantification of Environmental Impact.- 3.7 Early Diagenesis of Trace Metal Compounds in Sediments.- 3.7.1 Sampling of Interstitial Waters.- 3.7.2 Diagenetic Environments.- 3.7.3 Diagenetic Mobilization of Trace Metals.- 4 Metals in the Atmosphere.- 4.1 Introduction.- 4.2 Natural and Anthropogenic Emissions of Trace Metals.- 4.3 Atmospheric Particles.- 4.4 Deposition of Atmospheric Particles.- 4.5 Metal Concentrations in Urban, Rural and Remote Atmospheres.- 4.6 Environmental Impact of Airborne Trace Metals.- 4.6.1 Terrestrial Ecosystems..- 4.6.2 The Arctic and Antarctic Aerosol.- 4.6.2.1 Concentrations in Arctic and Antarctic Areas.- 4.6.2.2 Seasonal Changes.- 4.6.2.3 Origin of the Arctic Aerosol.- 4.6.3 Metals in the Oceanic Aerosol: Continental or Ocean Derived?.- 4.6.3.1 Formation of the Oceanic Aerosol.- 4.6.3.2 Sea Surface Microlayer.- 4.6.3.3 Composition of the Oceanic Aerosol.- 5 Metals in Continental Waters.- 5.1 Introduction.- 5.2 Metals in Rocks and Soils.- 5.2.1 Igneous and Metamorphic Rocks.- 5.2.2 Weathering and Element Migration.- 5.2.3 Chemistry of Sedimentary Rocks.- 5.2.4 Metals in Soils.- 5.2.4.1 Soil Constituents and Metal Binding.- 5.2.4.2 Trace Metal Concentrations in Soils.- 5.2.4.3 Metal Transfer from Soil to Plants.- 5.2.4.4 Problems with River-borne Metal Pollutants on Agricultural Soils.- 5.2.4.5 Land Disposal of Metal-Contaminated Waste Materials.- 5.3 Metals in Rivers.- 5.3.1 Trace Metals in River Water.- 5.3.2 Dissolved and Solid Transport.- 5.3.2.1 Geographical Variability.- 5.3.2.2 Seasonal Variability.- 5.3.3 Metals in River Sediment.- 5.3.3.1 Factors Affecting Compositions.- 5.3.3.2 Variability of Data.- 5.3.3.3 Influence of Grain Size.- 5.3.3.4 Metal Forms.- 5.3.4 Impact of Metals in River Systems.- 5.3.4.1 Distribution of Metal Pollutants.- 5.3.4.2 Historical Evolution.- 5.3.4.3 Metal Budgets and Local Inputs.- 5.3.5 Complexing Agents in River Systems.- 5.4 Metals in Lakes.- 5.4.1 Introduction.- 5.4.2 Accumulative Phases in Lake Sediments.- 5.4.3 Trace Metal Fluxes as Reflected in the Sediments.- 5.4.4 Metals Cycling in Lakes.- 5.4.5 Metals Cycling in Stratified Lakes.- 5.4.6 Atmospheric Inputs in Lakes.- 6 Metals in Estuaries and Coastal Environments.- 6.1 Introduction.- 6.2 Estuarine Circulation.- 6.3 Conservative and Non-Conservative Behaviour.- 6.4 Behaviour of Particulate Trace Metals During Estuarine Mixing.- 6.5 Iron and Manganese.- 6.6 Trace Metals in Estuaries: Field Investigations.- 6.7 Trace Metals in Estuaries: Laboratory Investigations and Simulations.- 6.8 Environmental Impact Studies.- 6.8.1 United States Estuaries and Coastal Areas.- 6.8.2 Mediterranean Sea.- 6.8.3 Western Europe.- 6.8.4 Environmental Impact of Metals in Biota.- 6.9 Estuaries as Sinks for Trace Metals?.- 7 Metals in the Ocean.- 7.1 Introduction.- 7.2 Vertical and Horizontal Distribution of Trace Metals..- 7.3 Particulates and Metal Behaviour.- 7.4 Composition of Oceanic Sediments.- 7.4.1 Marine Sedimentary Facies.- 7.4.2 Metal Concentrations.- 7.4.3 Metal Enrichment in Deep-Sea Sediments.- 7.4.3.1 Diagenetic Metal Enrichment-Manganese Nodules.- 7.4.3.2 Metal Enrichment from Hydrothermal Inputs.- 7.5 Cycling of Trace Metals Between Continents and Oceans.- 8 Summary and Qutlook.- References.

Abstract: Of the 117 stream and lake systems sampled nationwide, fish from Manoa Stream on Oahu, Hawaii, have consistently shown the highest Pb concentrations. Therefore a detailed study was conducted to examine total metal contents in bed sediments from a 5.8-km stretch of Manoa Stream. A total of 123 samples (<63 μm) were examined for 18 elements and 14 samples for 21 elements. Selected samples were also examined using different leach solutions to examine metal phase associations. All trace metal data, computations of enrichment ratios and the modified index of geoaccumulation point to mineralogical control for Cr and Ni; minor anthropogenic contamination for Ba, Cd, Cu, Hg and Zn; and a very strong contamination signal for Pb. Maximum Pb contents (up to 1080 mg kg−1) were associated with anthropogenic material dumping in minor tributaries, storm sewer sediments and sediments in the “lower” section of the basin. Proportionally Pb had the highest non-residual component of elements examined; dominantly in the reducible phase associated with Mn and amorphous Fe oxyhydroxides. The contamination signal was typically lowest in the “undisturbed” headwater reach of the basin (above 5.1 km) with significant increases throughout the “residential” and “commercial-institutional” zones of the mid-basin. The spatial pattern of bed sediment contamination and evidence from storm sewer-outlet sediments strongly indicates that Pb, and to a lesser degree some other metals, is still being transported to the stream and the primary agent is soil erosion and transport of metals sorbed to sediments. The primary source of sediment-associated metals is considered to be the automobile, though other minor sources can not be ruled out.

Abstract: Accurate and precise sampling and analytical procedures are essential in environmental geochemical studies. This report provides a detailed description of the techniques and analytical procedures for sampling, grain size determinations, and for precise and accurate AAS determination of the major and trace metals in marine sediments and suspended particulate matter. In addition, it describes the procedures for the chemical partition of the metals, determination of readily oxidizable organic matter, and calcium carbonate. A separate section discusses the normalization of trace metal data.

Abstract: Trace elements mean elements present at low concentrations (mg kg � 1 or less) in agroecosystems. Some trace elements, including copper (Cu), zinc (Zn), manganese (Mn), iron (Fe), molybdenum (Mo), and boron (B) are essential to plant growth and are called micronutrients. Except for B, these elements are also heavy metals, and are toxic to plants at high concentrations. Some trace elements, such as cobalt (Co) and selenium (Se), are not essential to plant growth but are required by animals and human beings. Other trace elements such as cadmium (Cd), lead (Pb), chromium (Cr), nickel (Ni), mercury (Hg), and arsenic (As) have toxic effects on living organisms and are often considered as contaminants. Trace elements in an agroecosystem are either inherited from soil parent materials or inputs through human activities. Soil contamination with heavy metals and toxic elements due to parent materials or point sources often occurs in a limited area and is easy to identify. Repeated use of metal-enriched chemicals, fertilizers, and organic amendments such as sewage sludge as well as wastewater may cause contamination at a large scale. A good example is the increased concentration of Cu and Zn in soils under long-term production of citrus and other fruit crops. Many chemical processes are involved in the transformation of trace elements in soils, but precipitation–dissolution, adsorption–desorption, and complexation are the most important processes controlling bioavailability and mobility of trace elements in soils. Both deficiency and toxicity of trace elements occur in agroecosystems. Application of trace elements in fertilizers is effective in correcting micronutrient deficiencies for crop production, whereas remediation of soils contaminated with metals is still costly and difficult although phytoremediation appears promising as a costeffective approach. Soil microorganisms are the first living organisms subjected to the impacts of metal contamination. Being responsive and sensitive, changes in microbial biomass, activity, and community structure as a result of increased metal concentration in soil may be used as indicators of soil contamination or soil environmental quality. Future research needs to focus on the balance of trace elements in an agroecosystem, elaboration of soil chemical and biochemical parameters that can be used to diagnose soil contamination with or deficiency in trace elements, and quantification of trace metal transport from an agroecosystem to the environment. r 2005 Elsevier GmbH. All rights reserved.