Chemical Forms Of Heavy Metals Research Articles

Heavy metals in rivers and soils of central Chile

Industrial and domestic waste waters in Chile are discharged without previous treatment into rivers and other inland waters which are used to irrigate agricultural lands. The present study reports on results obtained when analyzing inland waters for Cd, Cu, Zn, Hg and As. Copper content was found to be high in most of the rivers studied and its sources were identifiable copper mining wastewaters. Cadmium and Zn levels are above accepted levels in some instances, whereas Hg and As content of river waters under study studied were found to be within accepted levels. The more reactive chemical forms of heavy metals in soils irrigated with polluted waters, as determined by sequential extraction, were found to be the most abundant ones. These forms are easily bio-available.

Chemical forms of heavy metals in carbonate-derived laterite and enrichment of its iron oxide minerals

In this paper the seven-step continuous extracting method was employed in the study of chemical forms of the six heavy metals Co, Zn, Pb, Cu, Cr and Mn. The result shows that the metals in the laterite are present in the chemical form of crystalline iron oxides and residues, and they are transformed toward organic and exchangeable forms in the surface soil. Linear regression analysis indicates that the above heavy metals have a positive correlation with the crystalline iron oxide minerals. The crystalline iron oxide minerals have a very important role to play in the enrichment of heavy metals, especially the solid components in the laterite.

Recycling wastes in agriculture: heavy metal bioavailability

Recycling wastes in agriculture is an essential disposal method, and according to waste characteristics can produce supplementary organic-matter resources (sewage sludge, compost) for crop production, or valuable soil amendments (coal fly-ash). However, since heavy-metal content in waste materials is often higher than in the soil, application rates have to be carefully controlled, to obviate the possible accumulation of toxic metals in agricultural soils. The risk of the possible pollution of crops by heavy metals makes it necessary to use guidelines for waste utilization. Generally, guidelines and legislation refer to the total amounts of heavy metals in wastes and in soil. The total amount however, is of very low environmental importance and much international experimentation concerning these elements is actually engaged in determining the real availability of heavy metals to plants in relation to the chemical forms of heavy metals in the soil. This paper emphasizes the extractability of metals in relation to soil chemistry, and plant uptake bioassay as an important diagnostic tool for metal bioavailability.

Metals and their chemical and mineralogical forms in industrial pollutants of the atmosphere

Abstract The contents and chemical forms of heavy metals in different types of industrial dusts have been examined and mineralogical composition of dusts characterized. Dusts emitted by the metallurgical plants contain iron minerals: magnetite and hematite, carbonates: calcite and dolomite, sulphates: gypsum and anhydrite and silicates: quartz and mullite. Dusts emitted by the chemical plants contain fluoroapatite and calcite. Sylvite, quartz and calcite are the main components of dusts from cement plants. Mullite and quartz are the main phases of dusts from power plants. In dusts emitted by metallurgical plants, rich in iron oxides a high content of Mn, Zn, Pb and Cu has been stated. Dusts originating from chemical plants are rich in Cd and Cr. In the examined dusts two groups of metals can be distinguished: metals such as Cd, Zn, Mn and Ni, which have a relatively large potentially mobilizable portion, and metals such as Cr, Pb, Fe and Cu that are more stably bound to dust particles.

Speciation of particulate trace metals in sediments of Anarbe reservoir∗

Total concentration and chemical forms of heavy metals in samples of sediment from a drinking water reservoir have been analysed. The result of total metal contest shows Fe and Mn concentration increase along the reservoir, from 4.4% in Fe and 0.07% in Mn in the end part to 6.4% Fe and 0.22% Mn at the dam. However, a decrease in organic matter along the reservoir is observed. In order to test the accuracy of the digestion methods used, a standard reference material was also analysed. Trace metal concentrations, with exception of Cadmium, Pb and Mn, found in fraction 5 are higher than those observed in the others extractions, Fe, Ni, Zn, Cr and Cu content in non‐residual fraction is found mainly in moderately reducible fraction, but the percentage of this fraction in each metal is very different.

The content and chemical forms of heavy metals in the river sediments of the Cracow area the role of clay minerals

Abstract The content of heavy metals (Cd, Pb, Zn, Cu, Cr, Ni, Mn and Fe), the grain size distribution and the mineralogical composition was estimated in the bottom sediments of the Vistula and its tributaries: the Rudawa and Wilga rivers. The concentration of metals was variable, depending on the grain size and mineralogical composition, and primarily on the sampling locality. A few samples were subjected to selective chemical extraction to establish the chemical associations of some heavy metals. According to the type of chemical forms, these metals can be divided into two groups: ones showing relatively high mobility (Cd, Zn, Mn) and metals more strongly bonded to sediment particles (Cr, Cu, Pb, Fe, Ni).

The diverse chemical forms of heavy metals in tissue extracts of some metallophytes from Shaba Province, Zaïre

Copper and cobalt were determined in tissue extracts of five metallophytes from Shaba Province, Zaïre. About 4O% of the cobalt and copper was extractable into deionized water and a further 4O% was extractable in 0.2M hydrochloric acid. It was concluded that copper and cobalt are bound to several different ligands instead of a single ligand as in the case of nickel hyperaccumulators. Proton microprobe studies on the cobalt accumulator Haumaniastrum robertii showed a strong inverse correlation between the spatial distributions of cobalt and potassium, as well as a direct relationship between cobalt and calcium. It is suggested that some of the cobalt may be immobilized with calcium in oxalate crystals.