Manuel Azenha

Abstract Micro/nanomotors represent a burgeoning field of research featuring small devices capable of autonomous movement in liquid environments through catalytic reactions and/or external stimuli. This review delves into recent advancements in light-driven semiconductor-based micro/nanomotors (LDSM), focusing on optimized syntheses, enhanced motion mechanisms, and emerging applications in the environmental and biomedical domains. The survey commences with a theoretical introduction to micromotors and their propulsion mechanisms, followed by an exploration of commonly studied LDSM, emphasizing their advantages. Critical properties affecting propulsion, such as surface features, morphology, and size, are presented alongside discussions on external conditions related to light sources and intensity, which are crucial for optimizing the propulsion speed. Each property is accompanied by a theoretical background and conclusions drawn up to 2018. The review further investigates recent adaptations of LDSM, uncovering underlying mechanisms and associated benefits. A brief discussion is included on potential synergistic effects between different external conditions, aiming to enhance efficiency-a relatively underexplored topic. In conclusion, the review outlines emerging applications in biomedicine and environmental monitoring/remediation resulting from recent LDSM research, highlighting the growing significance of this field. The comprehensive exploration of LDSM advancements provides valuable insights for researchers and practitioners seeking to leverage these innovative micro/nanomotors in diverse applications.

Abstract Purpose Pejao Mining Complex locates in Castelo de Paiva municipality and, until its closure in 1994, was one of the most important coal mines in the Douro Coalfield. This work aims to study the presence, quantify, and evaluate the dissemination of mercury (Hg), a potentially toxic element (PTE) of major public health concern by the World Health Organization (WHO), from a waste pile affected by coal fires.Materials and methods Samples from areas affected and unaffected by the combustion and from surrounding soil were collected from Fojo waste pile region. First, the Hg pseudo-total concentration was estimated for all collected samples by soil microwave-assisted digestion with aqua regia (USEPA 3051A). Then, a sequential extraction procedure (SEP), the USEPA 3200, was applied for Hg fractionation and speciation aiming to evaluate Hg mobility and bioavailability to surrounding ecosystems.Results and discussion The results obtained showed a Hg enrichment in soil samples when compared to Portuguese and international reference values for soils. Relatively to the Hg availability and mobility, although it predominates in the semi-mobile fraction, the waste pile materials exposed to combustion showed a concerning increase of Hg levels in the mobile fraction that contains the more labile Hg species, being a major source of environmental contamination by Hg.Conclusions This study allowed to conclude that combustion of mining residues increased Hg mobility, toxicity, and bioavailability, increasing the contamination potential of the coal waste pile. The methodology applied in this work can be replicated in other abandoned mines to monitor, control, and/or mitigate the Hg environmental impact in the surrounding soils and waters.

Abstract The occurrence of drought in soils, particularly in those contaminated by metals, poses a current threat to crops, as these factors can interact and induce unique stress responses. Therefore, this study mainly focused on understanding the crosstalk between drought and copper (Cu) stress in the physiology of the barley (Hordeum vulgare L.) plant. Using a bifactorial experimental design, seedlings were grown in a natural soil under the following treatments: plants continuously irrigated in uncontaminated soil for 14 days (control); plants continuously irrigated in Cu-contaminated soil (115 mg Cu kg-1) for 14 days (Cu); plants only irrigated during the initials 7 days of growth in uncontaminated soil (drought); plants co-exposed to Cu and drought (combined). After 14 days of growth, the results revealed that drought prevented Cu bioaccumulation in barley roots, which were still severely affected by the metal, both individually and in combination with the water deficit. Furthermore, individual and combined exposure to these stressors resulted in impaired photosynthetic performance in barley plants. Despite the increased activation of enzymatic and non-enzymatic antioxidant defence mechanisms, particularly in the green organs, the plants co-exposed to both stress factors still showed higher oxidative damage, severely impacting biomass production.

Abstract Soil contamination with metals is a major threat for the environment and public health since most metals are toxic to humans and to non-human biota, even at low concentrations. Thus, new sustainable remediation approaches are currently needed to immobilize metals in soils to decrease their mobility and bioavailability. In this work, we explore the application of discarded substrates from hydroponic cultivation, namely coconut shell and a mixture of coconut shell and pine bark, for immobilization of metals (Cd, Cr, Ni, Cu, Pb, Hg, Sb and As) in a naturally contaminated soil from a mining region in Portugal. The immobilization capacity of substrates (added to the soil at 5% mass ratio) was assessed both individually and also combined with other traditional agriculture soil additives (limestone and gypsum, at 2% mass ratio) and nanoparticles of zero-valent iron (nZVI) at 1–3% mass ratio. The overall results obtained after a 30-d incubation showed that the discarded substrates are a viable, economic, and environmental-friendly solution for metal remediation in soils, with the capacity of immobilization ranging from 20 to 91% for the metals and metalloids studied. Furthermore, they showed the capacity to reduce the soil toxicity (EC50 ∼ 6000 mg/L) to non-toxic levels (EC50 > 10000 mg/L) to the bacteria Aliivrio fischeri. © 2024 The Authors

Abstract Conventional tomato production is widely threatened by environmental changes that impose increasingly frequent and severe conditions of soil salinization and water shortage. The assessment of the wild germplasm has become an appealing strategy for the stress-resilience improvement of crops. Tomato interspecific diversity encompasses wild species that are native to the dry shores and high-elevated deserts of the Andean countries, often thriving under circumstances of drought and salinity. The present work aimed to compare the effects of moderate salinity stress under different watering regimes on the ion distribution, redox homeostasis, osmoregulation, and antioxidant defenses between a domestic cultivar of tomato (Chico III) and the wild tomato species Solanum galapagense (LA1403), Solanum habrochaites (LA1223), and Solanum neorickii (LA2194). Results showed that although wild tomato plants grew slower than the cultivar, their growth was less affected by exposure to salt or to lower water availability. S. galapagense revealed a Na+ includer behavior under salt stress, increasing Na+ levels by 6-fold over control, reaching levels 4 times higher than in the cultivar. Nonetheless, H2O2-detoxifying enzymes were activated, and shoot elongation was sustained in this species, suggesting an efficient Na+ compartmentalization. On the other hand, the domestic cultivar had the highest accumulation of Na+ in roots and showed the lowest ability to sustain growth under combined stress. Leaves of S. habrochaites showed a huge proline buildup under salt stress, whereas S. neorickii and S. galapagense seemed to prevent proline accumulation. S. habrochaites also had high levels of antioxidant metabolites and superoxide dismutase activity under control conditions but downregulated further antioxidant defenses in response to stress exposure. No oxidative damages were noticed despite the almost 2-fold increase in ROS content in the leaves of S. neorickii under salt stress, which showed a negative correlation with growth traits, but an improvement in the antioxidant potential. A principal component analysis (PCA) revealed five PCs with eigenvalues >1, explaining 84 % of the total variability, and suggesting a separation of the evaluated samples mainly in accordance with the type of redox disturbances and antioxidant defenses employed, levels of photosynthetic pigments, balance between Na+ and K+ uptake and proline accumulation. These findings show that wild tomato plants respond differently than cultivated ones under moderate salinity and reduced water availability, suggesting interesting osmoregulatory and antioxidant mechanisms in S. galapagense and S. habrochaites.