Luisa Andrade

Influence of mineral and organic components on copper, lead, and zinc sorption by acid soils

Sorption isotherms were constructed for the sorption of Cu, Pb and Zn by the surface horizons of three soils [a Humic Cambisol (G1), a Haplic Podzol (G2) and an Umbric Gleysol (G3)] and by fractions obtained by sequential removal of organic matter and oxides. All were of L-type except the H-type isotherms recorded for sorption of lead by whole G2, and all were fitted well by the Langmuir model, with determination coefficients > 0.91. Langmuir equation parameter β correlated well (r 2 = 0.985) with experimentally maximum sorption capacity. For all soils, metal sorption capacities decreased in the order Zn > Cu > Pb. Sorption by organic matter was one of the main contributions to total sorption. Sorption by oxides was generally most substantial in G1, which had the largest total oxides content, while the sorption of lead by G3 was attributable to its high Mn oxides content. The clayey residue contributed significantly to sorption of zinc by G1, and G3 (due to their respective vermiculite and gibbsite contents) and to sorption of copper by G1 due to its vermiculite content.

Improving Soil Fertility to Support Grass–Legume Revegetation on Lignite Mine Spoils

The short-term sequential effects of different treatments on soil fertility and revegetation of mine spoils were examined in a lignite mine in northwestern Spain. Experimental plots were established both on old and recent spoils after tillage and treated with compost or nitrogen (N), phosphorus (P), potassium (K), + magnesium limestone before seeding with a grass–legume species mixture. Compost improved plant production and, contrary to NPK, maintained soil N levels and supplied enough P for the establishment and early growth of the vegetation. Severe magnesium (Mg), calcium (Ca), and K limitations in recent spoils were only alleviated by compost + magnesium limestone, allowing the rapid growth and coating of the soil surface. The amendment based on NPK + magnesium limestone improved plant production in the short term but caused proliferation of weeds. Results suggest that revegetation in combination with the appropriate amendments is a key issue for the reclamation of lignite mine spoils.

Heavy metal content and toxicity of mine and quarry soils

PurposeSoils formed in metallic mines and serpentinite quarries, among other unfavourable features, have high levels of heavy metals. They can release into the environment causing surface and subsurface water contamination, uptake by plants, their accumulation in the food chain and adverse effects on living organisms. In this work, we studied the magnitude of the soils’ toxic effects not only on spontaneous plants but also on two species with phytoremediation potential.Materials and methodsSeveral soils from two different exploitations were selected: a lead and zinc mine and a serpentinite quarry. Soils were characterized, and the pseudo-total and extractable contents of Co, Cr and Ni in soils from a serpentinite quarry were determined. The Cd, Pb and Zn pseudo-total and extractable contents were determined in soils developed in the Pb/Zn abandoned mine. Using a biotest, the chronic toxicity of the soil samples on higher plants was determined. Festuca ovina L., Cytisus scoparius (L.) Link., Sinapis alba L. and Brassica juncea L. were selected, the first two because they are spontaneous plants in the study areas and the last two because they have heavy metal phytoremediation potential.Results and discussionPseudo-total contents of Co, Cr and Ni in the serpentinite quarry soils and of Zn, Pb and Cd in the Zn/Pb mine soils exceed generic reference levels. CaCl2 is the reactant that extracts the highest proportion of Co, Cr and Ni in the quarry soils and EDTA the largest proportion of Pb Zn and Cd content in the mine soils. The germination index values based on seed germination and root elongation bioassays revealed increasing plant sensitivity to the mine soils in the following order: B. juncea < S. alba < F. ovina < C. scoparius. The wide range of GI values indicates that the response of test plants to soil heavy metals depended on their concentrations and soil characteristics, especially pH and organic matter content.ConclusionsThe pollution index indicates severe Cd, Pb and Zn contamination in the mine soils, as well as high Cr and Ni and moderate Co contamination in the serpentinite quarry soils. The performed biotests were suitable for identifying toxic soils and showed that the studied soils are toxic to the spontaneous plants, more to C. scoparius than to F. ovina. They also indicate that the mine soils are more toxic than the quarry soils for both species.

Effect of long‐term cultivation on zinc and copper contents in soils from the bahía blanca horticultural belt (Argentina)

Abstract The objectives of this work were to quantify the total and available copper (Cu) and zinc (Zn) contents in soils which have been used for intensive agricultural production and to investigate the influence of the soils properties on the absorption and migration of these metals. Total and available Zn and Cu contents in the topsoil and their variation with depth in Mollisols from the Bahía Blanca (Argentina) horticultural belt have been studied. Total contents of Cu and Zn were extracted by means of acid digestion in Teflon bombs placed in a microwave oven. The available Cu and Zn contents were extracted using the DTPA method and the analysis of Cu and Zn was carried out by atomic absorption spectrophotometry. High contents of Cu and Zn were found in the surface layers of all the plots studied and lower contents were noted in plots recently used for horticulture. The lowest contents were found in control farms. The results showed that 70% of the Zn in the surface layers were found in unavailable form, whereas almost 50% of the Cu was in available form. No relationship was noted between each kind of cultivation and Cu content. Most of the Zn in the different plots was adsorbed or complexed by organic ligands and clay. The variation of Cu and Zn content with the depth indicated a greater mobility of Cu. Most of the Zn was detected in the surface soil, whereas no differences were noted in Cu content between surface and subsoil. The results obtained confirmed the anthropic origin of these metals in the cultivated plots. The correlation found between the different forms of Zn and Cu as well as between their total and available contents suggested that these metals have been applied together via agrochemicals and waste.

Uso de Arcillas Especiales para Depuración de Aguas Residuales

Para evaluar la eficacia de las arcillas especiales para la remocion de metales pesados de aguas residuales, se muestrearon y caracterizaron varios tipos de arcillas y las aguas de tres efluentes residuales industriales. Los componentes mayoritarios de las arcillas fueron: sepiolita: montmorillonita (76%); bentonita magnesica: vermiculita (74,4%); bentonita aluminica: esmectita (69,1%) y paligorskita (80%). Las aguas residuales se hicieron circular a traves de lechos de cada una de las arcillas; manteniendo un tiempo de contacto de tres horas. Se analizo el contenido de metales pesados disueltos en las aguas antes y despues de pasar a traves de cada lecho. La sepiolita y la bentonita magnesica son eficaces para reducir la concentracion de metales pesados en aguas residuales industriales. Se concluye que la adsorcion depende del pH, del contenido de metales y del contenido de solidos en suspension en las aguas