Determination Of Zinc Species Using Ultrafiltration And Different Solid Sorbents.

A method or the determination of operationally-defined metal species at natural concentration levels has been developed. The method is based on a combination of physical characterization by size fractionation using ultrafiltration and chemical characterization by retention studies on different solid sorbents

Determination Of Zn Species Using Ultrafiltration And Different Solid Sorbents.

A method for the determination of operationally-defined metal species at natural concentration levels has been developed. The method is based on a combination of physical characterization by size fractionation using ultrafiltration and chemical characterization by retention studies on different solid sorbents

Nondetrital and total metal distribution in core sediments from the U-Tapao Canal, Songkhla, Thailand

The U-Tapao Canal is the main source of freshwater draining into the outer part of Songkhla Lake, which is the most important estuarine lagoon in Thailand. Songkhla Lake is located in southern Thailand between latitudes 7 08 and 7 50 N and longitudes 100 07 and 100 37 E. Acetic acid (HOAc)-soluble Cu, Fe, Mn, Pb, and Zn and the total concentration of these metals along with Al concentration, organic carbon, carbonate, sand, silt, and clay contents were determined in 4 sediment cores obtained at selected intervals from the mouth of the canal to 12 km upstream. Readily oxidizable organic matter in the cores varies from 1.52% to 7.30% and is generally found to decrease seaward. Total concentrations of Al (61.7 99.0 g kg 1; 2.293.67 mol kg 1), Cu (12.4 28.2 mg kg 1; 195 444 Amol kg 1), Fe (25.2 42.0 g kg 1; 451 752 mmol kg 1), Mn (0.220.49 g kg 1; 4.08.9 mmol kg 1), Pb (16.743.1 mg kg 1; 80.6208 Amol kg 1), and Zn (48.6122.7 mg kg 1; 0.741.88 mmol kg 1) vary to a certain extent vertically and seaward in the U-Tapao Canal core sediments. These concentrations are at or near natural levels and show no indication of anthropogenic contamination. Overall, the data show that total metal concentrations in the surface and near surface core sediments are enriched in varying degrees relative to Al in the order of ~ZnNMnNPbNFeNCu. Chemical partitioning shows that the enrichment in the surface and near surface sediments is related to the relatively high proportion of the total metal concentrations (MnNZnNFeNCuNPb) that occur in the acetic acid-soluble (nondetrital) fraction, and they generally decrease with depth. Nondetrital Cu, Pb, and Zn likely derive from those metals held in ion exchange positions, certain carbonates, and from easily soluble amorphous compounds of Mn and perhaps those of Fe. Diagenetic processes involving Mn and to a lesser extent, Fe compounds, as well as the vertical changes in the oxidizing/reducing boundaries, appear to be the most important factors controlling the behavior of the metals in these cores. Organic matter and the aluminosilicate minerals, however, appear to be less important carriers of the metals studied

The chromium isotopic composition of seawater and marine carbonates

Chromium isotopes are fractionated during redox reactions and have the potential to provide a record of changes in the oxygenation levels of the oceans in the geological past. However, Cr is a trace metal in seawater and its low concentrations make isotopic measurements challenging. Here we report the first determinations of View the MathML source for seawater from open ocean (Argentine Basin) and coastal (Southampton Water) settings, using a double-spike technique. The total chromium concentration in seawater from Southampton Water is 1.85 nM, whereas the Cr content of Argentine Basin samples is 5.8–6.6 nM. The View the MathML source value of seawater from the Argentine Basin is 0.491–0.556‰ in intermediate and deep waters, and varies between 0.412 and 0.664‰ in surface waters (<150 m). The View the MathML source value of Southampton Water seawater is 1.505‰, which may reflect in situ reduction of Cr(VI) to Cr(III). All of our seawater samples have higher View the MathML source than crustal and mantle silicates, and mass balance modelling demonstrates that river water must also be enriched in heavy Cr isotopes, indicating that Cr isotopes are fractionated during weathering and/or during transport to the oceans. We also show that the Cr isotopic composition of modern non-skeletal marine carbonates (0.640– 0.745‰) encompasses the range that we measure for Argentine Basin seawater. Thus, fractionation of Cr isotopes during precipitation of these marine carbonates is likely to be small (<0.2‰), and they have the potential to provide a record of the Cr isotopic composition of ancient seawater. Phanerozoic carbonates are also characterised by heavy View the MathML source and a correlation between View the MathML source and Ce/Ce⁎ suggests that the Cr and Ce cycles in the ocean are linked