Percorrer por autor "Alonso-Vega, Flora"
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- Concentración y reservorio de Hg en el sistema suelo-planta en el bosque caducifolio Mediterráneo nativo del NE de PortugalPublication . Parente-Sendín, Andrea; Méndez-López, Melissa; Calvo-Portela, Noemi; Fonseca, Felícia; Figueiredo, Tomás de; Nunes, Luís; Pontevedra-Pombal, Xabier; Alonso-Vega, Flora; Nóvoa-Muñoz, Juan CarlosEste estudio se desarrolló en parcelas de bosque nativo mediterráneo, dominado por Quercus pyrenaica, situadas al noreste de Portugal. Se determina la concentración y reservorio de mercurio (Hg) en la biomasa aérea (hojas, ramas y tronco) y en horizontes orgánicos (OL, OF y OH) y minerales (hasta 30 cm) del suelo. La acumulación de Hg en la biomasa aérea es 0,22, 0,10 y 0,5 g ha-1 en hojas, ramas y madera de tronco, respectivamente. El rango de concentración de Hg total (THg) en los horizontes orgánicos fue de 75-122 μg kg-1 y 78-112 μg kg-1 en el suelo mineral. El Hg almacenado (RHg) en los horizontes O (OL+OF+OH) y suelo mineral (hasta 30 cm) es 1,9 y 255 g ha-1, respectivamente. Las correlaciones de THg y RHg con C orgánico total, N total y la relación C/N, apuntan a la dinámica de la materia orgánica como principal factor de influencia en la presencia y almacenamiento de Hg en el suelo. La alteración del ciclo del C afectaría al papel del suelo como sumidero de Hg, promoviendo un mayor riesgo de movilización de Hg hacia componentes más sensibles de los ecosistemas terrestres como la biota y aguas superficiales y freáticas.
- Mercury mobilization in shrubland after a prescribed fire in NE Portugal: insight on soil organic matter composition and different aggregate sizePublication . Méndez-López, Melissa; Jiménez-Morillo, Nicasio Tomás; Fonseca, Felícia; Figueiredo, Tomás de; Parente-Sendín, Andrea; Alonso-Vega, Flora; Arias-Estévez, Manuel; Nóvoa-Muñoz, Juan CarlosSoils constitute the major reservoir of mercury (Hg) in terrestrial ecosystems, whose stability may be threatened by wildfires. This research attempts to look at the effect of prescribed fire on the presence of Hg in a shrubland ecosystem from NE Portugal, delving into its relationship with soil aggregate size and the molecular composition of soil organic matter (SOM). During the prescribed fire, on average 347 mg Hg ha 1 were lost from the burnt aboveground biomass of shrubs and 263 mg Hg ha 1 from the combustion of the soil organic horizon. Overall, Hg concentration and pools in the mineral soil did not show significant changes due to burning, which highlights their role as long-term Hg reservoirs. The higher Hg concentrations found in smaller aggregates (<0.2 mm) compared to coarser ones (0.5–2 mm) are favored by the higher degree of organic matter decomposition (low C/ N ratio), rather than by greater total organic C contents. The Hg-enriched finest fraction of soil (<0.2 mm) could be more prone to be mobilized by erosion, whose potential arrival to water bodies increases the environmental concern for the Hg present in fire-affected soils. The SOM quality (molecular composition) and the main organic families, analyzed by Fourier-transform infrared spectroscopy in combination with multivariate statistical
- Mobilization of mercury by sediment transport after a prescribed fire in NE Portugal: Insight into size classes and temporal variationPublication . Méndez-López, Melissa; Parente-Sendín, Andrea; Acemel-Míguez, Lara; Fonseca, Felícia; Santos, Israel; Figueiredo, Tomás de; Arias-Estévez, Manuel; Alonso-Vega, Flora; Nóvoa-Muñoz, Juan CarlosTerrestrial ecosystems are important sinks for atmospheric mercury (Hg). It is well known that high severity wildfires can mobilize Hg in the surroundings of burned areas due to changes in ecosystem stability, but it is unclear whether this also occurs after lower severity fires, such as prescribed fires. The present study determined Hg concentrations and mobilization rates in different size fractions of sediments collected after a prescribed fire in a scrubland area. Sediments, collected from eight erosion plots on six occasions, were analysed for total Hg, C and N in several size classes (<0.2 mm, 0.2–0.5 mm, 0.5–2 mm and >2 mm) and Hg mobilization rates (HgST) were calculated for each size fraction. Average total Hg were 38, 57, 94 and 126 μg kg^-1 for size fractions > 2, 0.5–2, 0.2–0.5 and < 0.2 mm, respectively. Total Hg was negatively correlated with C/N ratio, involving the humification degree of organic matter of sediments in Hg retention. In the last event (eight months after fire), sediments had 45–106 % more Hg, depending on size fraction, compared to the initial event. Mercury mobilization rates varied between 32 and 78 mg ha^-1, with the fraction 0.5–2 mm accounting for 46 % of the mobilized Hg. The results revealed that prescribed fires can mobilize Hg, so their use to prevent wildfires must be done with caution.
- The role of afforestation species as a driver of Hg accumulation in organic horizons of forest soils from a Mediterranean mountain area in SW EuropePublication . Méndez-López, Melissa; Gómez-Armesto, Antía; Alonso-Vega, Flora; Pontevedra-Pombal, Xabier; Fonseca, Felícia; Figueiredo, Tomás de; Arias-Estévez, Manuel; Nóvoa-Muñoz, Juan CarlosForest areas are a primary sink of atmospheric mercury (Hg) within terrestrial ecosystems, whereas forest vegetation plays a key role in atmospheric Hg transfer to soil horizons. This study assessed variations in total Hg contents (HgT) and accumulation (HgRes) in the soil organic horizons of a forest area in NE Portugal, where post-wildfire afforestation led to the substitution of the native deciduous species (Quercus pyrenaica) by fast-growing coniferous species (Pseudotsuga menziesii and Pinus nigra). The study also evaluated, for each species, the links between Hg contents and other biophilic elements of soil organic matter (C, N, S) present in organic subhorizons (OL, OF, OH). Mean HgT in the organic horizons of the different tree species follow the sequence: P. nigra (88 μg kg−1) < Q. pyrenaica (101 μg kg−1) < P. menziesii (141 μg kg−1). The highest HgRes for the entire organic horizon was found under P. menziesii (471 μg m−2), followed by P. nigra (253 μg m−2) and Q. pyrenaica (189 μg m−2). Among the organic subhorizons, values of HgT and HgRes follow the sequence OL < OF < OH, which is consistent with the degree of organic matter humification. Indeed, HgT and HgRes correlated significantly with the C/N and C/S ratios for all species and organic subhorizons, suggesting that the quality of organic matter may influence strongly the Hg fate in these forest soils. Soils from P. menziesii plots have shown an HgRes 2.5 times higher than in plots dominated by the native Q. pyrenaica. Hg accumulation in the organic horizons, promoted in the coniferous species, may increase the risk of Hg mobilization due to wildfires and forest management practices. Therefore, forest management plans should select cautiously the tree species for afforestation in order to minimize adverse environmental effects caused by changes in the biogeochemical cycle of contaminants such as Hg.