María José Sierra

Antarctica, although one of the planet’s most pristine regions, is not exempt from global pollution such as mercury (Hg), an element with a complex biogeochemical cycle. Hg emissions originate from natural and anthropogenic sources, and its long atmospheric residence time allows transport to remote regions. Polar regions act as sinks for Hg, particularly in ice-free areas where periglacial processes are dominant. Fildes Peninsula (King George Island) is one of the most densely populated areas in Antarctica with permanent scientific bases, an airport, and seasonal tourism, which increases environmental impacts. There are few in-depth studies on Hg in Antarctic soils, making it crucial to improve understanding of Hg behaviour and distribution within soil profiles from site-specific areas. This work examines Hg distribution in eleven soil profiles on Fildes Peninsula, identifies relationships between Hg and physicochemical soil parameters and evaluates potential drivers controlling Hg distribution. The results show three groups of soil profiles based on Hg depth patterns and soil properties: (1) neutral profiles in which Hg decrease with depth, where Hg is mainly associated with external inputs such as erosion processes, volcanic eruptions, periglacial processes, ocean aerosols, rainwater and/or snowmelt; (2) neutral profiles in which Hg increases with depth, where Hg is mainly linked to the parent material; and (3) ornithogenic profiles, where Hg is primarily related to organic residues derived from ornithogenic inputs. Furthermore, some profiles show evidence of anthropogenic influence from combustion emissions. Overall, organic matter, iron oxides and zeolites act as important Hg drivers across all analyzed profiles. Graphical Abstract The graphical abstract summarizes the main results of the study by illustrating observed mercury (Hg) depth patterns in Antarctic soil profiles and the soil properties controlling their distribution. Maps of Antarctica indicate the locations of the sampled sites, providing the geographical context of the investigation. The central part of the graphic presents representative soil profiles showing three distinct Hg depth trends identified in the study: neutral soils with decreasing Hg concentrations with depth, neutral soils with increasing Hg concentrations toward the parent material, and ornithogenic soils characterized by Hg enrichment associated with organic residues from bird activity. Upward- and downward-pointing triangles indicate Hg concentration changes with depth and are illustrated using field photographs of the sampled profiles. Potential Hg sources (atmospheric deposition, volcanic inputs, erosion processes, anthropogenic combustion, and organic residues) are shown as external inputs. The key drivers identified by the study—organic matter, Fe₂O₃, and zeolites—are highlighted as the main controls governing Hg retention and vertical redistribution within the soil profiles. Arrow thickness indicates the relative influence of these drivers on the different soil types.

The Almadén mining district is known to be one of the richest mercury areas in the world. Despite the high concentrations of this metal, this territory has well-established vegetation that provides a wide range of mercury-tolerant plants that can be used as ecosystem services. This is the case of some species of Cistus that grow wild and spontaneously as part of the natural flora of Almadén. The objective of this study was to evaluate if there were differences between the absorption and distribution of Hg of five species of the genus Cistus in spontaneous growth and to evaluate their potential application in phytotechnologies. The work has been carried out with plant samples collected under field conditions in the “Fuente del Jardinillo” located in the old mining area of Almadén (Ciudad Real). The experimental plot was divided into three previously characterised subplots to ensure that all the sampled plants had grown in similar soil conditions (pH, organic matter content, EC, CEC, total Hg and available Hg). Additionally, the experiment was carried out in triplicate. The results showed that despite the homogeneity of the soil, the absorption of Hg in the aerial part of the plants showed significant differences related to Cistus species. The values in the bioaccumulation of mercury in the aerial part were also different. Based on the uptake of mercury by the plants sampled in this study, its potential use in phytotechnologies was established, classifying them as phytoextractors (Cistus albidus, C. ladanifer and C. monspeliensis) and phytostabilisers (C. crispus and C. salviifolius).

The objective of this work was the evaluation of the release patterns of nitrogen from various types of fertilizers and their impact on selected chemical parameters of calcareous soil. Three mineral fertilizers and two organic fertilizers were tested in the laboratory for 35 days. This study showed the rapid release of nitrogen from mineral types. More than 70% of the nitrogen was released from the ammonium granules and 98% from the urea granules. The rate of nitrogen release from pellets of organic origin was much slower than from mineral pellets, the released N was 15–28% of the original amount. Soil pH was altered by incubation. The content of soil N changed significantly due to the incubation of N mineral fertilizers; no changes were observed for organic fertilizers. The EC value of the soil solution was significantly modified under the influence of mineral granules, it reached a maximum of 1147 µS cm⁻¹ on the 10th day, and for organic fertilizers of 944 µS cm⁻¹ on the 35th day. The results of this study characterize each N release pattern, providing data to support a more efficient nutrient management strategy in calcareous soils and the effect of incubated fertilizers on soil chemical parameters.

There are many studies on the beneficial effects of silicon (Si) in plants related to a decrease of stress (biotic/abiotic). The objective of the present work was to study how plant‐available Si in highly calcareous soil with different soil chemical properties, amendments and growing conditions can affect Si absorption by Hordeum vulgare L. (Barley) and its biomass. Barley was cultivated under field conditions in dryland agriculture. Three treatments were compared: phytolithic biochar, compost pellets and no amendment. Greenhouse trials with the same soil and treatments were also carried out to achieve a better understanding of the dynamics in the soil–plant system under controlled growing conditions. In both experiments, physical and chemical soil and plant parameters were determined from collected samples. Results showed that the Si uptake and biomass in soils with the highest available Si (33 ± 1 mg kg ⁻¹ ) was 4.7‐fold and 2.4‐fold higher, respectively, than in soils with the lowest available Si (22 ± 1 mg kg ⁻¹ ). Also, with greater Si uptake there was an increase in N uptake (τ = 0.68, p  < 0.01). Therefore, Si could improve N use efficiency within the plant. A strategy to improve Si values would be to use organic amendments that are enriched with Si and supply N in a form other than ammonium (). A high pH in this type of soil produces dissolution of the biogenic Si pool and low electrical conductivity values improve plant‐available Si values. It is important to increase plant‐available Si in highly calcareous soils as this has important implications for improving barley production.

While it is well-known that the toxicity of mercury for plants is related to its bioavailability in the environment in which the plant lives, few studies have addressed Hg effects under controlled conditions of life-limiting available Hg concentrations. This study examines the effects of Hg on the holm oak (Quercus ilex L.) exposed to medium-high available Hg concentrations. Holm oak seeds were sown in a perlite substrate and grown in the presence of a nutrient solution containing 0, 5, 25, or 50 μM Hg. The variables determined as outcome measures were impacts on germination, growth, and nutrient accumulation along with Hg concentration in leaves, stems, and roots at different growth stages. Our findings suggest no overall detrimental effects of the metal on germination, nutrient accumulation, and plant growth, although root morphology was clearly modified. Mercury accumulation in the plant varied according to time, organ, Hg treatment dose, and plant growth stage. When comparing Hg build-up in the different organs, highest concentrations of the metal were detected in the roots, followed by the leaves and stems. The Hg accumulation pattern was positively correlated with time and Hg dose, whereas negative correlation was observed with growth stage. The impacts of all these factors on Hg accumulation were not additive pointing to interesting interaction effects that should be explored in future work.

Monomethylmercury (MeHg) is one of the most toxic and the most commonly occurring organomercury compound and the wetlands are one of the main areas of generation of this Hg form. Concretely, it is in the macrophyte root system where better conditions are given for its generation. However, the knowledge of absorption and subsequent distribution of mercury (Hg) and monomethylmercury in aquatic plants is still limited. Mercury mining district such as Almadén (Ciudad Real, Spain) is a natural laboratory where different rivers flow and the species Typha domingensis Pers. is a common macrophyte which grows in their riverbanks. The aim of the present work is to apply a recently developed method specially designed to analyze Hg species in plant tissues to the different fractions of T. domingensis under real field conditions and to study the accumulation and distribution of Hg species (inorganic Hg and MeHg) within the plant. The results proved that whatever Hg species has preference to be accumulated in the belowground fractions and demonstrated a high efficiency in the accumulation of MeHg.

BACKGROUND: Potato (Solanum tuberosum) is a global crop and by far the most important non‐cereal crop in the world. Therefore, it is necessary to assure its safe consumption. This is especially relevant in the case of its cultivation in abandoned mining areas, where the population tends to return to agriculture. In the present work, the objective is to evaluate the contribution to the diet of nutrients and contaminants of potato grown in soils from the Almadén area (mining district) by studying the intestinal absorption (in vitro) of the tuber, taking into account the preparation methods for its consumption.RESULTS: The results of contaminant and nutrient contents show that the potato peel retains significantly more elements (mainly in the case of toxic elements) than the flesh. Furthermore, potato (peel and flesh) is a good source of iron.CONCLUSION: It is recommended to boil potatoes with the peel in order to minimize nutrient loss and, before consumption, peeling them to eliminate possible risks due to contaminants. In addition, to minimize the risk due of mercury and to improve the levels of calcium, magnesium, potassium and sodium, it is recommended to add salt during the boiling process. © 2017 Society of Chemical Industry