Showing papers on "Trace metal published in 1970"

Trace metal characterization in aquatic environments by anodic stripping voltammetry

Abstract: Generally it is accepted that trace metals such as Cu, Zn, Cd, Co, Cr, Ni, and Mo play a significant role in bio logically mediated reactions in the aquatic environment. In trace quanti ties many of these metal ions are es sential micronutrients for enzymatic transformations, but in high concen trations they may be inhibitory or toxic to biological systems. The con trolling role of metal ions on the eco logical balance and productivity of fresh waters has been emphasized by several authors (1) (2) (3) (4). For example, molybdenum, considered an essential micronutrient for nitrogen fixation and the formation of the plant enzyme nitrate reductase, controls the primary productivity of Castle Lake, Calif. (1). The trace metals in the aquatic en vironment also may serve as "mark ers" in the identification of water masses. The distribution and relative abundance of metal ions may offer valuable information on the geochemi cal history and pollutional character istics of natural waters. The exchange of metal ions between the hydrosphere and the biosphere, lithosph?re, and atmosphere must be considered in studying metals in natural waters.

Trace Metal Analysis by Gas Chromatography

Abstract: Gas chromatography offers a promising new approach to the quantitative and qualitative analyses for trace amounts of metals. This technique has excellent potential because of its high sensitivity and the low cost of instrumentation. The method utilizes the formation of metal complexes, e.g., fluorinated chelates which are volatile and stable enough for gas chromatographic separation and measurement. Some of these metal chelates can be detected at extremely low concentrations, e.g., at the 10−13-g level by using the electron capture detector which is very sensitive to fluorinated metal chelates. The significance of this research is its potential use in medicine, chemistry, environmental health, and metallurgy, where the presence or absence of ultratrace amounts of metals can be extremely important.

Preliminary assessment and biological impact of trace metal pollution in Piles River (Spain)

Abstract: We have analyzed the contents of copper, lead and cadmium in water, sediments and eel populations of Piles river in an upstream rural area and a downstream urban area. All heavy metals were determined by an electrochemical method (PSA). Sediment analyses showed that concentrations of these heavy metals in the samples from rural upstream were higher than those from urban downstream, suggesting that the main source of metal pollution in Piles river was originated by agricultural activities. There were significant correlations between copper, lead and cadmium concentrations in eel livers and sediments. For those metals, eels have proven to be a good indicator of aquatic environment pollution.

Trace Metal Analysis Using Ion ChromatographyIn Water Partitioned From Crude-oil Spills

Abstract: All crude oil contains trace metals with nickel (Ni) and vanadium (V) generally being the predominant elements. In the past, these trace metals were only a concern from the perspective of the fuel cracking process. However, in recent years, Ni/V ratios have been used as biomarkers for determining the origin of crude oil in spills of unknown origin. Boscan crude from Venezuela, for example, has Ni levels on the order of 100 ppm and V of 1,000 ppm. Spills as large as those seen in Kuwait create some concern for the partitioning of these trace metals to the environment. To assess the environmental impact of such spills, one first needs to determine if porphyrins keep these metals from partitioning, and if not, how to detect them at the expected low concentrations and in a speciated form. A cost-effective analysis for looking at these potential trace metals in their various speciations may be the use of ion chromatography with non-metallic pumps and plumbing. Utilization of concentration techniques and the injection of 4-ml samples allow consistent and reproducible detection of most metals at 0.5 ppb or lower. The lower limit is mainly a function of trace metals found naturally in deionized waters, contaminants in chemicals used, or from complication of having several oxidation states in metals such as vanadium. A perfecting of this detection method is discussed as a prelude to answering the question on partitioning and speciation.

Preliminary Results Of Atmospheric Trace MetalDeposition In Portugal Quantified By MossBiomonitoring

Abstract: The atmospheric deposition of trace metal in Portugal was assessed by moss monitoring. Concentrations of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were quantified in samples of Hypnum cupressiforme and Scleropodium touretii collected in the whole country after acid wet digestion and atomic spectrometry analysis. Distribution maps of the elements was drawn after ordinary kriging estimation and the analysis of the patterns obtained allowed the identification of some local contamination sources. Among them, urban and road traffic, mine exploration, power plants and metal industries were identified as principal fonts for some elements. Particular attention was given to soil as source for moss contamination as dust, which may be of major importance in areas with mediterranean characteristics, in which a large part of the country is included.