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Abstract: The aim of this study was to evaluate the effects of liming and vegetation on the dynamic of Fe in eutrophic wetland soils affected by mine wastes, under different flooding regimes. Simulated soil profiles were constructed with two types of wastes (pH∼3.1 and ∼6.4) collected from polluted salt marshes and four treatments were assayed: without liming+without plant, without liming+with plant, with liming+without plant, and with liming+with plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated in the profiles: A horizons (never underwater), C1 (alternating flooding–drying conditions), and C2 (always underwater). The pH, Eh, salinity, and the concentrations of DOC and soluble Fe were measured regularly at each horizon for 18 weeks. Liming decreased Fe solubility, mainly in the acidic waste (maximum average concentrations ∼18mgL−1 without liming and ∼6mgL−1 with liming). However, liming also facilitated a drop in Eh, increasing soluble Fe content. Plant rhizosphere re-distributed this Fe, which was accumulated in the upper horizons of the treatments with liming+with plant, particularly in the acidic waste (average concentrations ∼10mgL−1 in the A horizon and ∼5mgL−1 in the C1 and C2 horizons). Therefore, we conclude that the combined use of liming and vegetation enhance the mobilization of Fe in eutrophic wetland soils polluted by mine wastes under alternating flooding–drying conditions. This should be considered for the environmental management of these sites due to the role of Fe-minerals as sink for potentially-harmful compounds. [Copyright &y& Elsevier]

Abstract: The aim of this study was to assess the effectiveness of combining liming and vegetation for the phytomanagement of strongly acidic, saline eutrophic wetlands polluted by mine wastes. Simulated soil profiles were constructed and four treatments were assayed: without liming+without plant, without liming+with plant, with liming+without plant and with liming+with plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated: A (never under water), C1 (alternating flooding–drying conditions) and C2 (always under water). The soluble Cd, Cu, Mn, Pb and Zn concentrations were measured regularly for 18weeks and a sequential extraction procedure was applied at the end of the experiment. Liming was effective (between ∼70% and ∼100%) in reducing the soluble Zn, Cu and Pb. In contrast, soluble Mn and Cd increased with liming, especially in the treatment with liming+with plant, where the concentrations were 2-fold higher than in the non-limed treatments. The amendment increased the contents of Zn, Mn and Cd bound to potentially-mobilisable soil fractions at the expense of the most-environmentally-inert fractions. Hence, the combined use of liming and vegetation may increase the long-term environmental risk of metals solubilisation. [Copyright &y& Elsevier]

Abstract: The aim of this study was to identify the effectiveness of liming in combination with vegetation for the recovery of slightly acidic, saline soils of eutrophic wetlands affected by mine wastes, under fluctuating flooding conditions. Simulated soil profiles were constructed and four treatments were assayed under greenhouse conditions: control, only plant, only liming, and liming and plant. The plant species was the halophyte Sarcocornia fruticosa. Three horizons were differentiated: A (never under water), C1 (alternating flooding-drying conditions), and C2 (always under water). The pH, Eh, salinity, and the concentrations of dissolved organic carbon and soluble metals were measured regularly for 18 weeks. Liming favoured the growth of S. fruticosa, an increase in pH and a fall in Eh. The amendment was effective for reducing Mn, Zn, and Cd in pore water of bare soils, but not Cu and Pb. In the treatment with liming and plant, the growth of S. fruticosa counteracted the effect of the amendment, strongly increasing the concentrations of metals in pore water and distributing them along the soil profile. Hence, the combined use of liming and plants may increase the risk of metals mobilisation. [Copyright &y& Elsevier]

Abstract: Salt marshes near urban, industrial and mining areas are often affected both by heavy metals and by eutrophic water. The aim of this study was to assess and evaluate the main processes involved in the decrease of nitrate concentration in pore water of mine wastes flooded with eutrophic water, considering the presence or absence of plant rhizhosphere. Basic (pH∼7.8) carbonated loam mine wastes and free-carbonated acidic (pH∼6.2) sandy-loam mine wastes were collected from polluted coastal salt marshes of SE Spain which regularly receive nutrient-enriched water. The wastes were put in pots and flooded for 15 weeks with eutrophic water (dissolved organic carbon ∼26mgL−1, PO4 3− ∼23mgL−1, NO3 − ∼180mgL−1). Three treatments were assayed for each type of waste: pots with Sarcocornia fruticosa, pots with Phragmites australis and unvegetated pots. Soluble organic carbon, nitrate, soluble Cd, Pb and Zn, pH and Eh were monitored. But the 2nd day of flooding, nitrate concentrations had decreased between 70% and 90% (equivalent to 1.01–1.12gN-NO3 − m−2 day−1) with respect to the content in the water used for flooding, except in unvegetated pots with acidic wastes. Denitrification was the main mechanism associated with the removal of nitrate. The role of vegetation in improving the rhizospheric environment was relevant in the acidic wastes because higher sand content, lower pH and higher soluble metal concentrations might strongly hinder microbial activity Hence, revegetation of salt marshes polluted by acidic sandy mining wastes might improve the capacity of this type of environment to act as a green filter against excessive nitrate contents flowing through them. [Copyright &y& Elsevier]