Sequential extraction schemes are used in determining the partitioning of trace metals in sediments. Among them the most widely used is that proposed by Tessier et al.5 A modified Tessier procedure, with successive extractions until completeness is attained, using pH control for extraction of metal solubilized by acetic acid-acetate buffer, control of extracted iron and manganese for metal extracted by hydroxylamine hydrochloride and control of redox potential (Eh) of extractant solution for metal solubilized by hydrogen peroxide, is proposed for copper, lead, chromium and nickel speciation. The results obtained with the initial Tessier procedure and those obtained with the modified procedure are compared with a heavily polluted sediment sample, and the resulting metal distributions are discussed.

Specific Procedure for Metal Solid Speciation in Heavily Polluted River Sediments

Diagenetic remobilization of manganese, iron, copper and lead in anoxic sediment of a freshwater pond

Sediments from a reservoir on the bank of the River Severn show the content of Pb, Zn,Cu, Cd, and Mn transported with sediments in the river back to 1965 when the reservoir was commissioned. The R.Severn is unpolluted as shown by the low levels of metals present in the sediment core; the most recent sediments show a decline in metal content. The chemical partitioning of metals is typical of fluvial sediments. Up to 68% of the Cd was exchangeable, while most of the Cu was present as an organic complex. The lead was in both the organic and residual fractions, and the Zn was in the Fe/Mn oxides and the residual fraction.

Recent transport of metals in the river severn as recorded by the sediments of chelmarsh reservoir, shropshire, U.K

A sediment core was collected from S Reservoir, which is located in the western part of Okayama Prefecture. The vertical distribution of heavy metals (Fe, Mn, Zn, Ni, Cu and Cd) and fine particles (<37μm) was measured. The heavy metal contents of the sediment core are relatively high in small grain layers. Partitioning of heavy metals into NH2OH HCl soluble, H2O2 soluble and HF soluble fractions has been determined with a selective chemical leaching technique on the sediment samples. The greatest parts of Mn and Cd are contained in the NHOH HCl soluble fraction (mostly iron and manganese oxide and hydroxide coatings on silicate minerals), whereas more than 50% of Fe, Zn, Ni and Cu is present in the HF soluble fraction (silicate lattice). The variations of heavy metal contents in the sediment core are chiefly due to those in NH2OH HCl soluble and HF soluble fractions. Only manganese is significantly enriched in the NH2OH HCl soluble fraction of the settling material collected by the sediment trap near the bottom, probably due to the release of manganese from bottom sediment into overlying water. Manganese oxide and hydroxide reprecipitated under oxic conditions of the bottom water after the release might have been effectively collected by the sediment trap.

Masahiro Sakata

Papers

Partitioning of Heavy Metals into Mineral and Organic Fractions in Sediments from a Reservoir