Distribution Of Copper In Soils Research Articles

Influence of agro-industrial wastes on the sorption, desorption, and distribution of copper in soils polluted by mine tailings

The objective of this work was to modify minimally two agro-industrial wastes, to evaluate their effectiveness for the retention of copper in soils contaminated by mining tailings, as well as to evaluate the changes in the chemical forms of the metal in the soil and thus also evaluate the attenuation of copper desorption in a short period after a mine tailing spill on the soil. The solid wastes of olive mill and grape stalks of the wine-making process were modified minimally, through washing processes and partial alkalization, to obtain substrates with greater capacity for copper sorption. Two agricultural soils near a tailing impoundment were studied: a sandy loam soil with pH close to neutral and high total and available copper content and a clay soil with low copper content, slightly acid pH, and high clay content. Both soils were treated with mine tailings from the same site to simulate an involuntary spill of mining waste. The contaminated soils were treated with the organic amendments to study the sorption, desorption, and distribution of Cu in a period of 30 days. The application of simple procedures such as alkalinization or washing of the agro-industrial wastes improved the Cu sorption capacity and facilitated the application of these materials to the soil. The application of mine tailings to the soils decreased the Cu sorption and the affinity of the substrate for the metal. This adverse effect was ameliorated by the incorporation of minimally treated olive mill wastes and grape stalks, increasing the sorption by a range of 15 to 75% compared to untreated soils. In substrates with sandy loam soil, both amendments decrease the soluble fraction of Cu, an effect that was not observed in clay soil. In parallel, both amendments increased the fraction of metal bound to the oxidizable fraction, an effect that was greater for grape stalks. The organic amendments used in this study were effective to reduce the initial contamination by copper after a spill of mine tailing wastes containing this metal. In this sense, both amendments applied to sandy loam soil increased the organic matter content and the Cu sorption capacity, effects that are maintained for at least 30 days. In clay soil, these effects were observed only for grape stalks, probably due to its greater metal sorbent capacity compared to the olive oil waste.

Distribution and Fractionation of Copper in Soils of Apple Orchards (5 pp)

Frequent application of Bordeaux mixture, which includes copper, as a fungicide in fruit and grape orchards may lead to copper accumulation in the soil, especially when orchard age and application times increase. The objectives of this study were: (i) to investigate the copper content and its spatial distribution in orchard soils; (ii) to identify the copper fractionation in soil and its relationship with plant uptake; (iii) to understand the characteristics of copper contamination in orchard soils. Soil profile samples were taken in apple orchards with ages of 0, 5, 10, 20, 30 years and pot experiments were also carried out to study the effects of external copper input on copper fractionation. All soil samples were air-dried, ground and extracted with 0.43 mol L(-1) HNO3 for the total absorbed copper. Fractionation determination was conducted following Tessier and Shuman sequential extraction methods, and copper was measured with AAS. Plant samples were first dry ashed, dissolved with 6 mol L(-1) HCI and then copper and other elements were measured with ICP-MS. Soil total Cu was higher in the apple orchards than that in non-orchard fields and was seen to have increased with orchard age. Soil Cu increased substantially with the average annual copper increase, ranging from 2.5 to 9 mg Cu kg(-1). The distribution of copper in the soil profile was uneven, decreasing from surface to deeper layers, and the differences were significant, but the contents in every layer were also significantly correlated with those in the next layers. For all copper fractions, the organically bound, crystalline Mn oxide bound, and amorphous Fe bound fractions extracted with the Shuman method were much higher than the exchangeable and residual fractions. Using the Tessier method, organically bound, carbonate bound and Fe-Mn oxide bound fractions were much higher. With an increase in external copper input, the organically bound, crystalline Mn oxide bound and amorphous Fe bound fractions in the Shuman method and organically bound, carbonate bound and Fe-Mn oxide bound fractions in the Tessier method all increased significantly, while the changes in other fractions were not significant. Soil total copper and copper fractions were found to have good correlations with apple tree uptake. Copper in fruit flesh had significant correlations with soil total content in the 0-10 cm layer, all the copper fractions in the 0-5 cm layer, and some fractions in the deeper layers. Copper content in orchard soils increased significantly with intensive application of Bordeaux mixtures and orchard age. Copper content decreased sharply from the topsoil to deeper soil layers. The copper contents in different layers also significantly correlated with those in the next layers. Dominant fractions of the copper in soil were mainly associated with organic matter, iron and manganese oxides and carbonates. A close relationship was found between the copper content in soils and in apple tree organs (which contained 8.9 to 66 mg kg(-1) Cu). Though most copper in the soil was specifically adsorbed or immobilized, and copper was mainly distributed in topsoil, which was essentially devoid of roots, the copper concentration of fruit still had significantly positive correlations with soil copper and most copper fractions. Therefore, measures must be taken to control copper accumulation in orchard soils and to make the apple fruit production sustainable.

Distribution of fungicide-derived copper in soils, litter and vegetation of different aged stands of coffee (Coffea arabica L.) in Kenya

Samples of soils, litter and vegetation, collected from 24, 14 and 4 years old stands of coffee (Coffea arabica L.), which had been routinely treated with copper fungicides, were analysed for copper content. Total soil copper content was found to be a function of (a) stand age and (b) soil depth. Highest levels were encountered in the 0–20 cm zone of the 24 year old stand; soil collected beneath these bushes showed significant contamination to a depth of 80 cm. Soils from the younger stands showed proportionally less copper contamination. Copper levels in litter samples showed increases relative to stand age; litter from the oldest stand was heavily contaminated and leaf litter showed a higher copper content than that of the woody fraction. Tissues from coffee bushes could be divided into 2 groups on the basis of their copper content; those tissues which demonstrated a progressive age-dependent increase (bark, lateral stems and fine roots) and those tissues where copper levels did not reflect the cumulative exposure of the plant to this element (wood, different age classes of foliage).