Rubén Forján

Recovering a copper mine soil using organic amendments and phytomanagement with Brassica juncea L.

A 3-month greenhouse experiment was carried out for evaluating the effect of an amendment mixture and mustards on the chemical characteristics of a mine soil and the metal uptake by plants. A settling pond soil was amended with increasing percentages of a technosol and biochar mixture and vegetated with Brassica juncea L. Adding amendments and planting mustards increased the soil pH from 2.83 to 6.18 and the TSC from u.l to 131 g kg(-1) and generally reduced the CaCl2-extractable metal concentrations in the soil. However, the amendments increased the pseudo-total soil concentration of Ni from 9.27 to 31.9 mg kg(-1), Pb from 27.9 to 91.6 mg kg(-1) and Zn from 46.5 to 577 mg kg(-1). The technosol and biochar mixture increased the shoot biomass from 0.74 to 2.95 g and generally reduced the metal concentrations in plants, meaning B. juncea as a potential candidate for phytostabilization of mine soils.

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.

Nickel, Lead and Zinc Sorption in a Reclaimed Settling Pond Soil

Abstract The wastes used to amend soils sometimes have high concentrations of metals such as nickel (Ni), lead (Pb) and zinc (Zn). To determine the capacity of soils to retain these metals, the sorption capacities of different mine soils with and without reclamation treatments (tree vegetation and waste amendment) for Ni, Pb and Zn in individual and competitive situations were evaluated using the batch sorption technique. The untreated settling pond soil had low capacity for Ni, Pb and Zn retention. The site amended with wastes (sewage sludges and paper mill residues) increased the sorption capacity most, probably because of the higher concentrations of soil components with high retention capacity such as carbon and clay fraction. No significant competition was observed between metals in the competitive sorption experiment, indicating that the maximum of sorption was not achieved by adding 0.5 mmol L−1 of metal. We can conclude that, despite the possible additions of Ni, Pb and Zn from wastes to degraded soils, sewage sludges and paper mill residues have a high sorption capacity that would prevent the metals from being in a mobile form.

Planting trees and amending with waste increases the capacity of mine tailings soils to retain Ni, Pb and Zn

The sorption capacity for Ni, Pb and Zn of mine tailings soil with and without reclamation treatment (tree planting and waste amendment) was evaluated using the batch adsorption technique. It is important to determine the capacity of waste-amended soils to retain Ni, Pb and Zn, as the sludges used usually have high concentrations of these metals. The results obtained in the present study showed that the untreated mine tailings soil had a low capacity for Ni, Pb and Zn retention. The sorption capacity for Pb increased significantly in all of the treated soils, without any significant differences between them. The treatment that most increased the sorption capacity for Ni and Zn was planting with trees and amending with waste simultaneously, as this increased the concentration of both organic and inorganic carbon, exchangeable calcium, soil pH and effective cation exchange capacity

Remediation of a copper mine soil with organic amendments: compost and biochar versus Technosol and biochar

The contamination produced by metal mining activities is a major environmental problem; for this reason, sustainable management strategies are required for remediating mine soils. The present study focused on the effect of applying organic amendments combined with vegetation in a settling pond soil of a depleted copper mine of Touro (Spain). Two different amendments were applied in different soil/substrate ratios: (1) a mixture made of Technosol and biochar and (2) a mixture of compost and biochar. A 3-month greenhouse experiment was carried out to evaluate the effect of both amendments and mustard plants on the chemical characteristics of the mine soil and the metal uptake by plants. The results showed that the addition of both amendments and planting mustards significantly increased soil pH as well as C and N soil concentrations. The treatments also reduced the CaCl2-extractable metal concentrations in the soil. However, the amendments increased the pseudototal concentration of Zn in the mixtures, since Zn was present in the Technosol and the compost used. Mustard plants extracted Ni from the soil amended with compost and biochar, and Zn from the soil amended with Technosol and biochar. These results suggest Brassica juncea L. is a potential candidate to revegetate mine soil for their tolerance to Ni and Zn.

Effect of waste mixed with biochar as soil amendment on trace element solubility in a mine soil

Abandoned mining sites often cause contamination of surface and subsurface waters. A 3-month pot experiment was performed to evaluate the influence of waste mixed with biochar as a soil amendment on a series of chemical characteristics and trace element solubility in a mine soil. Trace element concentrations were measured in pore water of the mine soil reclaimed with different proportions of waste-biochar amendment (20, 40, 80 and 100%) and grown with Brassica juncea. The results showed that amendment application improved soil conditions such as pH, total carbon, dissolved organic carbon, total nitrogen, and strongly reduced the concentration of Al (99.99%), Co (99.95%), Cu (99.97%), Fe (99.79%) and Ni (99.91%) in pore water, compared to the unamended soils. Waste and biochar also promoted the establishment of B. juncea in the mine soil. These results highlight the importance of mitigating the impacts from abandoned mines sites on water quality. The use of waste and biochar as soil amendment combined with B. juncea plants was effective in reducing metal concentrations in pore water and the associated toxicity risk.