Zinc, lead and cadmium speciation in Dnieper water‐bodies

Abstract

Data on the concentrations and movements of Zn, Pb and Cd in Dnieper reservoirs and the Dnieper‐Bug estuary are considered. There is a clear trend of increasing concentrations, often two‐ to fourfold, of these materials from the 1960s to the end of the 1980s. Large increases may be explained as the result of increased human impact on the water‐bodies and also because of reduced water discharge in the Dnieper River (discharge has been reduced by nearly 10 km3 in recent years). At present, the average concentrations of Zn, Pb and Cd in Dnieper water‐bodies are 35.0–50.0, 15.0–18.0 and 0.5–1.8 μg L–1, respectively. Anodic stripping voltammetry, membrane filtration, ion‐exchange and gel permeation chromatography on neutral sephadexes were methods used for analysis. The influence of adsorption and complexation processes on the mobility of Zn, Pb and Cd, and the ratio of their forms were compared. Ratios of free metal ions to ions bound in complexes with natural organic ligands were studied. The binding of metals in complexes with dissolved organic matter (DOM), or their adsorption onto suspended particles, were major processes reducing the concentration of free ions in their most toxic form. The percentage of Zn, Pb, and Cd free ions in the total balance of dissolved forms was no more than 3.6–4.8, 0.2–0.6 and 7.2–9.5%, respectively. The molecular‐weight distribution of organic metal complexes and their chemical nature, as well as the potential for complexing of DOM were investigated. Most Zn, Pb and Cd was found as complex compounds with DOM of different chemical natures and molecular weights. Humic substances, particularly fulvic acids, played a major role in the migration of the metals. These ligands bind from 40 to 80% of metals in the composition of organic complexes. Metal complex compounds of relatively low molecular weight (< 5000 Da) predominated in organic complexes of Zn (38–50%), Pb (38–52%) and Cd (22–47%). The role of inorganic ligands in complexation in surface waters was less important.

Mercury and Lead Levels in Common Soaps from Local Markets in Mashhad, Iran

“…A number of these occur as natural constituents of the earth crust including arsenic, cadmium, chromium, lead, mercury, manganese and so on [7,9,10].…”

Physical, Chemical, and Biological Properties of Soil under Decaying Wood in a Tropical Wet Forest in Puerto Rico

“…This is plausible since higher concentrations of DOC have been reported in leachates from CWD [19]. The availability of cations can in turn be related to the formation of complexes with the soil organic matter [53,71]. Therefore, it is possible that divalent cations are being retained more strongly in the soil influenced by the older logs, where the accumulation of humic substances is higher [53].…”

Influences of Cadmium and Zinc Interaction and Humic Acid on Metal Accumulation in Ceratophyllum Demersum

“…DOM largely controls dissolved metals (i.e., metals passing through 0.45 μm filters) speciation (Florence, 1982). Numerous studies indicate that a large proportion of the trace metals found dissolved in natural waters are in the organic fraction (i.e., in the form of metal-DOM complexes) (Linnik, 2000). A major fraction of DOM in natural water (∼60%-70% of total dissolved organic carbon) is composed of humic substances which consist mainly of humic acid and fulvic acid.…”