Dynamics of nitrogen, phosphorus and metals in eutrophic wetlands affected by mine wastes. Effects of liming on plant growth and metals mobility

Abstract

and water-soluble organic carbon in the soil solution were regularly monitored. Before and after the flooding period, a soil P-fractionation was performed.-In relation to N dynamics, the NO 3 concentrations in the soil solution decreased between 70 and 90% by the second day of flooding, except in the unvegetated pots with the soil of pH~6.2. Denitrification was the main mechanism associated to the removal of NO 3 -. The role of vegetation in improving the rhizospheric environment was relevant in the soil of pH~6.2 because higher sand content, lower pH, and higher soluble metal concentrations might strongly hinder microbial activity.-In relation to P dynamics, the PO 4 3concentrations in the soil solution decreased between 80 and 90% after three hours of flooding, with and without vegetation. The Fe/Mn/Al oxides and the Ca/Mg compounds played an important role in soil P retention. In the pots with S. fruticosa, the reductive conditions induced P release from metal oxides and P retention to Ca/Mg compounds. In turn, P. australis may have favoured the release of P from carbonates, which was transferred to Fe/Mn/Al compounds. In the second experiment, soils with fine texture from the Marina del Carmolí (in this case of pH~6.4) and sandy soils from the Lo Poyo salt marsh (in this case of pH~3.1) were used. Each type of polluted soil was mixed with a lime amendment (dose of 20 g kg -1 ), assaying two treatments: non-limed and limed soil. Cuttings of S. fruticosa were planted in pots prepared with the soil treatments. The pots were irrigated for 10 months with eutrophic water and soluble metal concentrations (Al, Cd, Mn, Pb, and Zn) and plant survival, plant biomass, and plant metal content were determined. The lime amendment decreased the concentrations of soluble metals and favoured the growth of S. fruticosa, enhancing the capacity of the plant to phytostabilise metals in roots. In the third experiment, soils with fine texture from the Marina del Carmolí (in this case of pH~6.4) and sandy soils from the Lo Poyo salt marsh (in this case of pH~3.1) were used. Each type of polluted soil was mixed with a lime amendment (dose of 20 g kg -1 ). Simulated soil profiles (60 cm depth) 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 employed was S. fruticosa. Three horizons were differentiated in the soil profiles: A (never under water), C1 (alternating flooding-drying conditions), and C2 (always under water). The pH, Eh, and soluble metal concentrations (Cd, Cu, Fe, Mn, Pb, and Zn) were measured regularly at each depth for 18 weeks. At the end of the experiment a soil metalfractionation was applied. The lime amendment favoured the growth of S. fruticosa, an increase in pH, and a drop in Eh. -In relation to Fe dynamics, liming decreased Fe solubility, mainly in the soil of pH~3.1, but also facilitated a drop in Eh, favouring the dissolution of amorphous Fe oxides and hence increasing the c...

Procesos biogeoquímicos y eliminación de nitrógeno y fósforo de aguas eutrofizadas en humedales del entorno del Mar Menor: resultados experimentales en mesocosmo

“…Diversos trabajos destacan a los humedales como sistemas altamente efectivos en la depuración de aguas con elevadas concentraciones de NO 3 y PO 4 3-(Jiménez-Cárceles y González-Alcaraz, 2012;, por lo que se les ha denominado como filtros verdes.…”

“…Tabla 2.2. Concentraciones de metales pesados (cadmio -Cd-, cobre -Cu-, plomo -Pb-y zinc -Zn-) en suelos y sedimentos (mg kg -1 ) en el Mar Menor y en los saladares de la Marina del Carmolí y Lo Poyo (modificado de González-Alcaraz, 2012…”