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Wetlands are highly effective systems in removing large amounts of N from waters, preventing eutrophication processes. However, when wetlands are polluted by metal-mine wastes their capacity to act as green filters may be diminished. The objective of this study was to evaluate the effect of liming and plants (Sarcocornia fruticosa and Phragmites australis) on the removal of NO3 − from eutrophic water in slightly acidic, wetland soils polluted by metal-mine wastes. Simulated soil profiles were constructed and six treatments were assayed: (1) no liming + no plant, (2) no liming + S. fruticosa, (3) no liming + P. australis, (4) liming + no plant, (5) liming + S. fruticosa and (6) liming + P. australis. Three horizons were differentiated: A (never under water), C1 (alternating flooding-drying conditions) and C2 (always under water). The eutrophic water used to flood the soil profiles was enriched in N and organic carbon (pH ∼ 7.5, electrical conductivity ∼ 11 dS m−1, NO3 − ∼ 234 mg L−1 and dissolved organic carbon ∼ 106 mg L−1). The pH, Eh and concentrations of dissolved organic carbon (DOC), N–NO3 − and N–NH4 + were measured regularly for 18 weeks. Liming stimulated the growth of plants, especially for S. fruticosa (20-fold more plant biomass than without liming), increased the soil pH and favoured the decline of the Eh values, enhancing the removal of NO3 − via denitrification. Of all the treatments assayed, liming + S. fruticosa was the only treatment that removed almost completely the high concentration of NO3 − from the eutrophic flooding water, reaching ∼1 mg L−1 N–NO3 − at the end of the experiment, at all depths. The higher content of DOC in the pore water of this treatment could explain this behaviour, since more labile carbon was available to the soil microorganisms in the rhizosphere, favouring NO3 − removal through denitrification processes. However, the treatment liming + P. australis (2-fold more plant biomass that without liming) did not remove completely the high concentrations of NO3 − from the eutrophic water, except in the C2 horizon – which was permanently under water. Hence, our results show that the effectiveness of liming, regarding the removal of NO3 − from eutrophic flooding water in wetland soils polluted by metal-mine wastes, depends on the presence of plants, their growth and the production of organic compounds in the rhizospheric environment. [Copyright &y& Elsevier]

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]

This study aimed to evaluate the response of salt marshes to pulses of PO 4 3- -enriched water, with and without the presence of Phragmites australis . A one-year mesocosms experiment was performed in simulated soil profiles (fine-textured surface layers and sandy subsurface layers) from a coastal salt marsh of the Mar Menor lagoon under alternating flooding-drying conditions with eutrophic water, under low (1.95 mg L −1 P-PO 4 3- ) and high (19.5 mg L −1 P-PO 4 3- ) P load, and with the presence/absence of Phragmites . The PO 4 3- concentrations in soil porewater and drainage water were regularly measured, and P accumulated in soils (including a fractionation procedure) and plants (roots, rhizomes, stems and leaves) were analyzed. The experimental mesocosms were highly effective in the removal of P from the eutrophic flooding water (>90% reduction of the P added to the system both in the soil pore water and drainage water), regardless of the nutrient load, the season of the year and the presence/absence of Phragmites . The soil was the main sink of the P added to the system, while Phragmites had a minor role in P removal. The biomass of Phragmites accumulated ∼27% of the P added with the flooding water in the treatment with water of low P load while ∼12% of P in that of high P load; the rhizomes were the organs that contributed the most (∼67–72% of the total P retained by the plants). Ca/Mg compounds were the main contributors to the retention of P in the soil compartment, especially in the fine-textured surface soil layers (∼34–53% of the total P in the soil was present in this fraction). Phragmites favored the retention of P onto metal oxides (∼12% increase of the P retained in the metal oxides fraction in the treatment with water of high P load). Hence, the use of constructed wetlands to ameliorate the negative impacts of P-enriched waters in the Mar Menor lagoon and similar areas is recommended. We propose the incorporation of fine-textured carbonated materials, with high content of Ca/Mg compounds, and the use of Phragmites to favor the retention of P by these systems. [ABSTRACT FROM AUTHOR]