Mercury mobilization in shrubland after a prescribed fire in NE Portugal: insight on soil organic matter composition and different aggregate size

Soils 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 statisticalThis work was supported by the Interreg V-A Spain-Portugal program (POCTEP) 2014–2020 (Project 0701_TERRAMATER_1_E) funded by the European Regional Development Fund (FEDER), the EROFIRE project (PCIF/RPG/0079/2018) funded by FCT, Portugal and the InMerForEcos project (PID 2021-125114OB-I00) funded by Ministerio de Ciencia e Innovaciónn and Agencia Estatal de Investigaciónn (MCIN/ AEI) and FEDER. M. Méndez-López was supported by the predoctoral grant FPU (FPU17/05484) funded by the Ministerio de Educaciónn y Formación Profesional. N.T. Jiménez-Morillo was supported by a “Ramón y Cajal” contract (RYC2021-031253-I) funded by MCIN/AEI/10 .13039/501100011033 and the European Union “NextGenerationEU”/ PRTR”. The financial support of the Consellería de Cultura, Educación e Universidade (Xunta de Galicia) through the contract ED431C2021/46- GRC granted to the research group BV1 of the University of Vigo is also recognized. Open-access funding for this research has been provided by the University of Vigo/CISUG.info:eu-repo/semantics/publishedVersio

Mercury in a birch forest in SW Europe: Deposition flux by litterfall and pools in aboveground tree biomass and soils

Financiado para publicación en acceso aberto: Universidade de Vigo/CISUGAtmospheric mercury (Hg) is largely assimilated by vegetation and subsequently transferred to the soil by litterfall, which highlights the role of forests as one of the largest global Hg sinks within terrestrial ecosystems. We assessed the pool of Hg in the aboveground biomass (leaves, wood, bark, branches and twigs), the Hg deposition flux through litterfall over two years (by sorting fallen biomass in leaves, twigs, reproductive structures and miscellaneous) and its accumulation in the soil profile in a deciduous forest dominated by Betula alba from SW Europe. The total Hg pool in the aboveground birch biomass was in the range 532–683 mg ha−1, showing the following distribution by plant tissues: well-developed leaves (171 mg ha−1) > twigs (160 mg ha−1) > bark (159 mg ha−1) > bole wood (145 mg ha−1) > fine branches (25 mg ha−1) > thick branches (24 mg ha−1) > newly sprouted leaves (20 mg ha−1). The total Hg deposition fluxes through litterfall were 15.4 and 11.7 μg m−2 yr−1 for the two years studied, with the greatest contribution coming from birch leaves (73 %). In the soil profile, the pool of Hg in the mineral soil (37.0 mg m−2) was an order of magnitude higher than in the organic horizons (1.0 mg m−2), mostly conditioned by parameters such as soil bulk density and thickness, total C andNcontents and the presence of certain Al compounds.Ministerio de Educación y Formación Profesional | Ref. FPU17/05484Xunta de Galicia | Ref. ED431C2021/46-GRCXunta de Galicia | Ref. ED431F2018/06- EXCELENCI

Physicochemical properties and microbiome of vineyard soils from DOP Ribeiro (NW Spain) are influenced by agricultural management

Agricultural management influences the soil ecosystem by affecting its physicochemical properties, residues of pesticides and microbiome. As vineyards grow crops with the highest incidence of pesticides, the aim of this study was to evaluate the impact of conventional and sustainable management systems of vineyards from DOP Ribeiro on the soil’s condition. Samples from soils under three different management systems were collected, and the main soil physicochemical properties were evaluated. A selection of 50 pesticides were investigated by liquid chromatography with tandem mass spectrometry. The bacterial and fungal microbiomes were characterized through amplicon sequencing. The results show that organic agriculture positively influences soil pH and the concentration of some nutrients compared to conventional management. Our microbiome analysis demonstrated that transitioning from conventional to organic management significantly improves several BeCrop® indexes related to key microbial metabolism and soil bio-sustainability. Such a transition does not affect soil alpha diversity, but leads to a higher interconnected microbial network structure. Moreover, differential core genera and species for each management system are observed. In addition, the correlation of the microbiome with geographical distance is evidence of the existence of different microbial terroirs within DOP Ribeiro. Indeed, sustainable management leads to higher nutrient availability and enhances soil health in the short term, while lowering pesticide usage.Consellería do Medio Rural—Xunta de Galicia | Ref. AC2021E-0

Concentración y reservorio de Hg en el sistema suelo-planta en el bosque caducifolio Mediterráneo nativo del NE de Portugal

Este 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.The present study was carried out in native forest plots, dominated by Quercus pyrenaica, located in northeastern Portugal. The concentrations and reservoirs of mercury (Hg) in different plant compartments (leaves, branches, and bole wood), organic horizons (OL, OF, and OH sub horizons) and mineral soil (up to 30 cm depth) were determined. The accumulation of Hg in aboveground biomass is 0.22, 0.10, and 0.50 g ha-1 in leaves, branches and bole wood, respectively. Ranges of total Hg concentration (THg) were 75-122 μg kg-1 and 78-112 μg kg-1 for organic horizons and mineral soil respectively. Mercury stored in soil (RHg) is 1.9 g ha-1 for O horizons (OL+OF+OH) and 255 g ha-1 for mineral soil (up to 30 cm depth). The correlations between THg and RHg with total organic C, total N and the C/N ratio suggest that soil organic matter dynamic is the main responsible for the occurrence and storage of Hg in soil. Changes in the C cycle would affect the role of soils as Hg sink, promoting a greater risk of Hg mobilization to more sensitive components of the terrestrial ecosystems such as wildlife, surface waters and groundwater.info:eu-repo/semantics/publishedVersio