Downscaling projections of climate change in Sao Tome and Principe Islands,Africa

Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work.     

Surface atmospheric circulation patterns and associated minimum temperatures in the Maipo and Casablanca valleys, central Chile

This paper analyzes the influence of circulation anomalies on the magnitude of minimum air temperature (T _min) at a daily scale in two important agricultural valleys of Chile (Maipo and Casablanca) during the period 2001–2007. A statistical classification of synoptic fields was performed, resulting in eight circulation patterns (CPs, 84 % of explained variance). The corresponding anomalies of T _min (AT_min) of each CP were analyzed in order to understand their synoptic-scale forcing mechanisms. Results showed a direct association between AT_min and the synoptic structure. The average weakening in sea level pressure (SLP) yields positive AT_min, while negative AT_min is associated with a strengthening in SLP. In the latter case, it was also found that a synoptic structure (10.2 % of frequency) corresponding to a migratory high-pressure system passing eastward across the Andes led to the lowest AT_min and a higher probability of frost in both valleys (22 % on average) in winter and springtime.     

Laser Ablation in the Synthesis of Zirconium Oxide

Results of an experimental study of the oxidation of a zirconium plasma generated by laser ablation of a metallic target under low pressures of oxygen are presented. The crystallographic identification of the collected product by electronic diffraction shows metastable ZrO cubic phase. The oxidation phenomena are interpreted by thermochemical simulation suggesting a model in accordance with other cases of synthesis of metastable oxides at high temperatures, such as plasma reactors.     

A model of characteristic earthquakes and its implications for regional seismicity

Regional seismicity (i.e. that averaged over large enough areas over long enough periods of time) has a size–frequency relationship, the Gutenberg–Richter law, which differs from that found for some seismic faults, the Characteristic Earthquake relationship. But all seismicity comes in the end from active faults, so the question arises of how one seismicity pattern could emerge from the other. The recently introduced Minimalist Model of Vázquez‐Prada et al. of characteristic earthquakes provides a simple representation of the seismicity originating from a single fault. Here, we show that a Characteristic Earthquake relationship together with a fractal distribution of fault lengths can accurately describe the total seismicity produced in a region. The resulting earthquake catalogue accounts for the addition of both all the characteristic and all the non‐characteristic events triggered in the faults. The global accumulated size–frequency relationship strongly depends on the fault length fractal exponent and, for fractal exponents close to 2, correctly describes a Gutenberg–Richter distribution with a b exponent compatible with real seismicity.     

Analysis and survival of amino acids in Martian regolith analogs

Abstract— We have investigated the native amino acid composition of two analogs of Martian soil, JSC Mars‐1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low latitudes on the Martian surface. The effects of the simulated conditions have been examined using high‐performance liquid chromatography (HPLC). Exposure to energetic ultraviolet (UV) light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which is interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H₂O are at work within the Martian soil. We discuss the influence of UV radiation, low temperatures, and gaseous CO₂ on the intrinsic amino acid composition of Martian soil analogs and describe, with the help of a simple model, how these studies fit within the framework of life detection on Mars and the practical tasks of choosing and using Martian regolith analogs in planetary research.     

Phytoremediation potential and morphological changes of plants growing in the vicinity of lead smelter plant

With the increasing industrialization, heavy metals concentration in soils has greatly increased. Phytoremediation is a low-cost, non-intrusive and aesthetically harmonious technology that uses plants to remediate contaminated sites by heavy metals. The aim of the study was to determine Cd, Pb and Zn concentration in the biomass of plant species growing on a multi-metal-contaminated site of lead smelter processing, to assess the workability of using these plants for phytoremediation purposes and highlight possible damage in morphological leaf changes. Two plant species, i.e., Ipomoea asarifolia and Urochloa decumbens and the associated soil samples were collected and analyzed Cd, Pb and Zn concentrations and then calculating the bioconcentration factor and translocation factor parameters for each element. Leaves and roots samples were observed by light microscopy. Metal concentrations varied greatly and majorly depend on site sampled, plant species and tissue. Cd, Pb and Zn in tissue ranged from 0 to 102.48, 0 to 381.04 and 12.84 to 295.02 mg Kg^?1. However, none of the plant showed potential for hyperaccumulation. Both plants showed bioaccumulation factor more than one, where it was 7.66 and 6.82 for Pb and Zn in U. decumbens, respectively. Translocation factor was calculated below one for both plants and all metals. Morphological studies revealed development of adaptive features that strengthen the U. decumbens to grow in contaminated soil. Our study suggests that I. asarifolia and U. decumbens have potential for phytostabilization at multi-metal-contaminated site.     

Adsorption of methylene blue and crystal violet on low-cost adsorbent: waste fruits of <Emphasis Type="Italic">Rapanea ferruginea</Emphasis> (ethanol-treated and H<Subscript>2</Subscript>SO<Subscript>4</Subscript>-treated)

This study assesses the ability of two low-cost adsorbents made from waste of Rapanea ferruginea treated with ethanol (WRf) and its H₂SO₄-treated analog (WRf/H₂SO₄) for the removal of two cationic dyes methylene blue (MB) and crystal violet (CV) from aqueous solutions. The adsorbent was characterized by scanning electron microscopy, Fourier transform infrared spectrometry, thermogravimetric analysis, point of zero charge (pH_pzc), specific surface, and functional groups. The adsorption of dye onto the adsorbents was studied as a function of pH solution (2–12), contact time (up to 120 min) and initial concentration (20–120 mg/L), and temperature (25, 35, and 55 °C). The influence of these parameters on adsorption capacity was studied using the batch process. The response surface methodology (RSM) was used in the experimental design, modeling of the process, and optimizing of the variables and was optimized by the response involving Box–Behnken factorial design (15 runs). The results show that the data correlated well with the Sips isotherm. The maximum adsorption capacities of MB and CV onto WRf were found to be 69 and 106 mg/g, and onto WRf/H₂SO₄, the adsorption capacities were 33 and 125 mg/g, respectively. The kinetic data revealed that adsorption of cationic dyes onto the adsorbents closely follows the pseudo-second-order kinetic model. Regression analysis showed good fit of the experimental data to the second-order polynomial model, with coefficient of determination (R²) values for MB (R²?=?0.9685) and MB (R²?=?0.9832) for WRf and CV (R²?=?0.9685) and CV (R²?=?0.9832) for WRf/H₂SO₄ indicated that regression analysis is able to give a good prediction of response for the adsorption process in the range studied. The results revealed that waste from R. ferruginea is potentially an efficient and low-cost adsorbent for adsorption of MB and CV.     

What is wrong with post-fire soil erosion modelling? A meta-analysis on current approaches,research gaps,and future directions

In the near future, a higher occurrence of wildfires is expected due to climate change, carrying social, environmental, and economic implications. Such impacts are often associated with an increase of post-fire hydrological and erosive responses, which are difficult to predict. Soil erosion models have been proven to be a valuable tool in the decision-making process, from emergency response to long-term planning, however, they were not designed for post-fire conditions, so need to be adapted to include fire-induced changes. In recent years, there have been an increasing number of studies testing different models and adaptations for the prediction of post-fire soil erosion. However, many of these adaptations are being applied without field validation or model performance assessment. Therefore, this study aims to describe the scientific advances in the last 20 years in post-fire soil erosion modelling research and evaluate model adaptations to burned areas that aim to include: (i) fire-induced changes in soil and ground cover; (ii) fire-induced changes in infiltration; (iii) burn severity; and (iv) mitigation measures in their predictions. This study also discusses the strengths and weaknesses of these approaches, suggests potential improvements, and identifies directions for future research. Results show that studies are not homogeneously distributed worldwide, according to the model type used or by region most affected by wildfire. During calibration, 73% of cases involved model adaptation to burned conditions, and only 21% attempted to accommodate new processes. Burn severity was addressed in 75% of cases, whilst mitigation measures were simulated in 27%. Additionally, only a minor percentage of model predictions were validated with independent field data (17%) or assessed for uncertainties (13%). Therefore, further efforts are required in the adaptation of erosion models to burned conditions, to be widely used for post-fire management decisions. © 2020 John Wiley & Sons, Ltd.     

Geochemical evidence for melting of carbonated peridotite on Santa Maria Island, Azores

The islands of the Azores archipelago emerge from an oceanic plateau built on lithosphere increasing in age with distance from the Mid-Atlantic Ridge from 10 to 45 Ma. Here, we present the first comprehensive major and trace element and Sr–Nd–Pb isotope data from Santa Maria, the easternmost island of the archipelago, along with published data from the other Azores islands situated much closer to the Mid-Atlantic Ridge axis. We can show that the distinctively more variable and more enriched trace element ratios at Santa Maria combined with a relatively small range in Sr–Nd–Pb isotope ratios are the result of low degrees of partial melting of a common Azores mantle plume source underneath thicker lithosphere. This implies that melt extraction processes and melting dynamics may be able to better preserve the trace element mantle source variability underneath thicker lithosphere. These conclusions may apply widely for oceanic melts erupted on relatively thick lithosphere. In addition, lower Ti/Sm and K/La ratios and SiO₂ contents of Santa Maria lavas imply melting of a carbonated peridotite source. Mixing of variable portions of deep small-degree carbonated peridotite melts and shallow volatile-free garnet peridotite could explain the geochemical variability underneath Santa Maria in agreement with the volatile-rich nature of the Azores mantle source. However, Santa Maria is the Azores island where the CO₂-rich nature of the mantle source is more evident, reflecting a combination of a smaller extent of partial melting and the positioning at the edge of the tilted Azores mantle plume.