Trace metal

About: Trace metal is a research topic. Over the lifetime, 5125 publications have been published within this topic receiving 181046 citations.

Chemical Properties of Metal-Humic Acid Fractions of a Sewage Sludge-Amended Aridisol

Abstract: Humic acid (HA) was extracted from a Domino soil (Xerollic Calciorthids) cropped with barley (Hordeum vulgare L.) and sorghum [Sorghum bicolor (L.) Moench] in experimental plots that received applications of sewage sludge for 4, 5, 6, or 7 yr at rates of 0,22.5, 45, or 90 Mg ha⁻¹ yr⁻¹. The HA samples were characterized chemically by elemental and functional group analyses, total trace metal content, infrared (IR), and electron spin resonance (ESR) spectroscopy. As compared to the nonamended Domino (Xerollic Paleorthids) soil HA, the highest sludge-amended soil HA was extracted in higher yields and had higher N and S contents, lower C/N molar ratios, higher total acidity and phenolic OH content, lower organic free radical content, and higher relative intensity of the amide I and amide II IR absorption bands. These differences are believed to be caused by the incorporation of components typical of the applied sludge organic fraction into the soil HA, i.e., proteinaceous materials, sulfur-containing compounds, and phenolic components. The HA also exhibited a well-defined selectivity in respect to trace metal adsorption/desorption. Copper, Ni, Zn, Fe, and Cr were adsorbed strongly onto readily available sites, or through exchange with more weakly adsorbed trace metal ions (Mn, V, Ti, and Mo). However, the soil HA tended to reach metal saturation at the highest sludge application rates. The ESR analysis showed the presence of indigenous Cu²⁺, Fe³⁺, and VO²⁺-HA complexes in all HA samples. These complexes had similar chemical and structural properties, and were concluded to represent the speciation of the metals in association with HA. In general, the impact of the organic constituents in fresh sludge on the soil HA appeared to be mitigated somewhat by the continual tendency of soil organic matter to attain equilibrium, whereas the metal-organic portion of the soil HA was significantly affected by sludge application. Contribution from the Dep. of Soil and Environ. Sci., Univ. of California, Riverside.

Depuration of twelve trace metals in tissues of the oysters Crassostrea gigas and C. virginica

Abstract: The depuration of 12 trace metals in the mantle, gill, digestive gland, and kidney of Crassostrea gigas and C. virginica was investigated under natural field conditions; oysters from a relatively contaminated environment (Redwood Creek in south San Francisco Bay) were transplanted to a relatively clean environment (Tomales Bay). In the transplanted oysters, the digestive gland and kidney depurated Cd, Cu, Hg, Ag, and Zn more readily than the mantle and gill. Other trace metals As, Fe, Mn, Ni and Se showed varying depuration patterns. The results for Cr and Pb were inconclusive, since initial concentrations were too low to follow any losses. Interspecific differences in trace metal depuration were observed. Biological half-lives for most trace metals were on the order of 23 to 60 d for C. gigas and on the order of 70 to 180 d for C. virginica.

Transmural Movements of Zinc, Manganese, Cadmium and Mercury by Rat Small Intestine

Abstract: To elucidate some features of the mechanism of distribution and localization of trace metals in soft mammalian tissues, we studied the simultaneous uptake and transport patterns of 2 essential metals, Zn and Mn, and 2 nonessential metals, Cd and Hg. The radioisotopes of the metals and loops of rat small intestine were used in a new in vitro perfusion method. The characteristic rates of metal uptake and metal transport varied markedly. During the first hour of perfusion, very small amounts of Zn, Hg or Cd were transported across the rat intestinal wall, whereas Mn was transported to an appreciable extent. Except for Mn, when the tissue uptake of a metal was high, its accumulation in the serosal solution was proportionately slow. The relative uptake-to-transport molar ratios for Zn, Hg, Cd and Mn were approxi mately 20:12:6:1, respectively. The uptake or transport of a metal was strikingly en hanced or depressed by the presence of a second metal particularly when the initial concentration of the second metal exceeded the concentration of the first. The effects of each of the chemical agents, L-ascorbate, dehydroascorbate, phlorhizin, iodoacetate and EDTA on the simultaneous uptake and transport of each of these 4 metals were measured. Zinc, Cd and Mn uptakes were depressed by L-ascorbate, dehydroascorbate or EDTA, whereas their transports were enhanced, except for Mn transport which was unaffected by L-ascorbate. Iodoacetate depressed Zn and Hg transports but markedly enhanced the uptakes of Zn, Hg, and Cd. Phlorhizin enhanced the uptake and depressed the transport of Cd nearly 3-fold. Both Zn uptake and transport were enhanced by phlorhizin. The transmural passages of this tetrad of metals Zn, Mn, Cd, and Hg are not dependent on the expenditure of metabolic energy, are not unidirec tional, and are not carried against a concentration difference. Competition among these metals for uptake and transport appears to be primarily a competition for the common available uptake sites. Transport is controlled to a lesser degree by the dif- fusibility characteristics of the ions of the particular metal. Advances in understanding the nature Zn, Mn, Cd and Hg by segments of rat of the mechanisms involved in the absorp- small intestine. The uptake by the intesti- tion of divalent trace metals by cells and nal wall of the rat and transport across it tissues have been slow. Relatively little is were simultaneously measured. Observa- known about the characteristics of the tions on the effects of various pharma- movements of these metals whereby their cologic agents on metal uptake and trans- tissue concentrations are regulated. That port as well as mutual competition for there is some control mechanism operative transmural passage between pairs of these at the cell membrane level, at least for the metals are also presented, essential metals, is suggested by their selec tive tissue localization and their variability