Complejación de metales por sustancias húmicas acuáticas como proceso natural, tomando como caso de estudio el Lago de Xochimilco

22 This work discusses the importance of organic matter, specifically Aquatic Humic Substances (SHA) 23 within the speciation and distribution of metals within an aquatic system, in this case Xochimilco 24 Lake, a site with great ecological importance. This lake is the natural habitat of the endemic species 25 “axolotl” (ajolote). In this research, complexation reactions between SHA and metals (Cu, Mn, Pb 26 and Zn) were carried out under different reaction conditions, the source of AHS was water samples 27 taken in Xochimilco Lake in presence and absence of pH buffer dissolution and varying the 28 concentration of metals. The results show that there is a direct competition between the major 29 elements and trace elements to react with the AHS. Under the pH conditions of Xochimilco Lake 30 complexes formation is possible. 31

Mineral lithotype identification on the andrill AND-2A drillcore, antarctica by using ternary mineral rock physics templates built from a self-consistent approach

In this work, wet bulk density ?WBD and compressional wave velocity VP core log data obtained along the AND-2A drillcore are plotted on density-velocity ternary mineral Rock Physics Templates (RPTs) built from a Self-Consistent (SC) micromechanics modelling with the purpose to deter- mine data trends that allow us to assist in identifying mineral lithotypes and lithological features throughout the 1138 m length of the drillcore. The elastic properties of the three dominant miner- als present in the drillcore (mixed clays, quartz, and calcite) and the pore-filling fluid (brine) were used as input data for the SC model. The interpreted lithology is then compared to that obtained from the analysis of the AND-2A drillcore ?WBD and VP log data using Gardner type density-velocity cross plots. Results from both the SC and Gardner methods are in good agreement with the main lithologies present in the AND-2A drillcore already reported in the scientific literature. Our findings also agree well when compared to the lithological description of six selected rock samples obtained at different depths on the AND-2A drillcore. These results suggest that the proposed SC approach could be helpful to assist to identify lithology in scientific drill holes where downhole elastic proper- ties may exist over intervals where portions of the drillcore were not recovered. Furthermore, even when elastic property data sets come from measurements on cores, the SC approach is likewise useful because, from visual analysis alone, lithology can sometimes be difficult to determine, and additional information from the analysis of the elastic properties may provide more insight.

The 1815 Tambora eruption: Its significance to the understanding of large-explosion caldera formations

Volcanic calderas, plentiful on the Earth and the moon, have been of much interest to volcanologists because of their large dimensions and extensive volumes of ejecta. Here, we consider the dynamics of caldera-forming by major explosive eruptions, examining how the breakdown of the earth's surface is caused by violent igneous activity. This leads to the definition of “typical explosion caldera”, which is a prototype of several newly-formed calderas in the historical timescale. There are three examples of such calderas: Tambora (Sumbawa), Krakatau (Sunda Straits), and Novarupta (Alaska). Tam- bora Caldera is the best example of a well-documented, recently formed typical explosion caldera, with no significant subsequent eruptions occurring after its formation. The subsurface structure of Tambora Caldera is discussed and compared to the 1883 eruption of Krakatau, the second largest eruption in historical times. Then, contrasting with the typically basaltic “collapse-type” calderas, a “Tambora-caldera type” is defined as a large “explosion-type” caldera, that may reach up to 10 km in diameter. The Tambora- type caldera concept is useful to qualify and understand the structure and components of other major calderas in the world. Fully developed larger explosion calderas such as Aso and Aira Calderas in Kyushu, Japan are discussed and explained as composite calderas based on geophysical data. Those calderas have repeatedly ejected massive pyroclastic products causing their original structures to grow wider than 10 km.

Projection of land use to 2030 and its impacts on water availability in a brazilian sub-basin: A LCM and SWAT approach

Changes in land use and land cover (LULC) can result in significant changes in a hydrographic ba- sin flow regime. Future projections about LULC and its interference with water availability help to identify extreme events in advance and help propose appropriate management measures. Thus, this study aimed to make the LULC projection for the year 2030 for the Alto Rio Grande (ARG) sub- basin, located in Southeastern Brazil. This region was chosen because of its intense water resources use and for having recently faced water scarcity as result of prolonged droughts and inadequate water resources management. To identify the LULC trend for the year 2030, the Land Change Modeler (LCM) was used, the map obtained was inserted in the Soil and Water Assessment Tool (SWAT) model previously calibrated and validated for the region’ environmental and climatic conditions. The ARG sub-basin was affected by heavy rains in 2011, which resulted in changes in the landscape due to landslides. This particularity of the region contributed to the projection of LULC for the year 2030 to present an increase in forest and pastures to the agricultural areas detriment. When evaluating the impacts of these changes in water availability, it was observed that the SWAT model presented, for the same rainfall conditions, a reduction in peak streamflows of up to 59% and a reduction in the average monthly flow of up to 63% in 2030 in relation to the LULC observed in 2017. Thus, this study provides an important contribution by identifying a considerable reduction in water availability. These results will help to formulate strategies for water resources management and the adoption of measures to promote water security in the region.

Radioactive heat production characterization of Ar-Rassafeh Badyieh area (area-2), Syria by using aerial gamma ray spectrometric and fractal modeling techniques

Aerial gamma-ray spectrometric technique is used herein to evaluate the radioactive heat production (HP) of Ar-Rassafeh Badyieh Area (Area-2), Syria. The nine already established lithological scored units of Area-2 have been separately characterized for the heat production HP parameter. The Concentration-number (C-N) model and the log-log plots associated with fractal technique are proposed and applied as a new approach to map the measured equivalent uranium (eU), the equivalent thorium (eTh), and potassium (K%) and the computed heat production (HP) of Area-2. The HP of Area-2 varies between a minimum of 0.06 and a maximum of 4.28 ?w/m3 with an average of 0.548 ?w/m3 and a standard deviation of 0.27?w/m3. The highest observed HP values are related to the phosphatic environments represented by two lithological scored units A and B.

Micromechanical modeling of ultrasonic velocity for pore-structure and porosity characterization considering anisotropy in carbonate samples

This work presents an approach to characterize the pore-structure and anisotropy in carbonate samples based on the Effective Medium Method (EMM). It considers a matrix with spheroidal inclusions which induce a transverse anisotropy. The compressional wave (VP), vertical (VSV) and horizontal (VSH) shear wave velocities are estimated taking into account parameters as characteristic length, frequency, angle of wave incidence, aspect ratio, mineralogy, and pore-filling fluid to predict pore shape in carbonates. Ranges of aspect ratios are shown to discriminate different pore types: intercrystalline, intergranular, moldic, and vuggy. The angle of wave incidence is a determinant parameter in the estimation of VP(0º, 45º, 90º), VSV(0º) and VSH(90º) to calculate dynamic anisotropic Young’s modulus (E33) and Poisson’s ratio (v31), as well as the Thomsen parameters, Epsilon, Gamma and Delta for quantification of the anisotropic pore-structure. The obtained results establish that the size, as well as the pore-structure, have a more significant impact on the elastic properties when the porosity takes values greater than 4% for the three frequencies, ultrasonic, sonic, and seismic. This investigation predicts the pore-structure and pore-size to improve characterization and elastic properties modeling of carbonate reservoirs. Validation of results includes porosity measurements and ultrasonic velocity data for different carbonate samples.

Magnetic parameters and palaeoclimate: A case study of loess deposits of North-East of Iran

Environmental magnetism techniques enable us to reconstruct paleoclimate conditions in some deposition such as losses. The magnetic properties of minerals are used as proxies for environmental changes. For this study, loess/paleosol sequence of Kolet section at Neka, north-east of Iran were magnetically investigated. We applied environmental magnetism methods, to reconstruct paleoclimate changes. We investigated relationship between paleoclimate changes and environmental magnetism proxies like magnetic susceptibility (?) variation. The laboratory techniques indicated the presence of main factor of magnetic property in loess/paleosol sequence, such as magnetite, maghemite and etc. We also estimated magnetically parameters (like SIRM, HIRM and etc.) to confirm concentrations of both aeolian and pedogenic particles versus variations of magnetic susceptibility enhancement. The ? values show prominent peaks for the three well developed soil and paleosol horizons, Recent Soil (S0), Upper Paleosol (S1) and Lower Paleosol (S2); which refer to warmer and wetter conditions. As result, we concluded that the increase/decreasing of magnetic susceptibility is coinciding with palaeosol/loess sequence, and probably with humid/arid conditions. Moreover, variations of magnetic susceptibility versus lithological column of Kolet section enabled us to recognize paleoclimatically periods known as interglacial/glacial cycles. The obtained magnetic data indicate that during over the past 50 ka, there have been at least two glacial/interglacial periods and since last 20 ka, there was no main glaciation occurrence, in the study area.

Seismic signatures of atmospheric disturbances in the Western Pacific as a tool for reconstruction of their dynamics

The wind and products of snowfalls and rainfalls touching the ground generate the seismic signals. During the decades, the study of seismic signatures of atmospheric disturbances, cyclones, was based on analysis of the ambient seismic noise in the low-frequency range which allowed identification of cyclones and location of the storm position. The methodology of monitoring of the atmospheric events using the short-period seismic signals recorded by a sensor installed at a height of about 4 km above sea level at the summit of dormant volcano Nevado de Colima is proposed. The methodology includes the indication of the seismic signatures of atmospheric disturbances on the daily helicorder displays of seismic signals with following analysis of waveforms, produced by the impact of rainfalls and snowfalls with the ground surface, and their Fourier spectral characteristics. Then, the reconstruction of the passage of the atmospheric events, based on the power spectral densities of the one-hour seismic records, which is performed mutually with the satellite observations. The methodology was applied to study the passage of hurricane Dora and its preceding tropical storm (June 2017) and the cold front system number 25 (January 2018). There were indicated the periods of actions of tropical storm, hurricane, and two stages of the cold front on the helicorder images. Then the characteristic waveforms for each period were selected. Analysis of the spectral characteristics of these waveforms demonstrated that the rainfalls, occurring during the tropical storm, hurricane and the initial stage of the cold front passage, generated the seismic signals within the frequency range between 1.0-1.8 Hz while the snowfall during the second stage of the cold front passage generated the seismic signals within the frequency range between 2.6 and 3.7 Hz. The reconstruction of dynamics of the passage of the atmospheric events based on the power spectral densities of the one-hour seismic records allowed to see the comparable intensity of tropical storm and hurricane, and two stages of the cold front. These results demonstrate a possibility for monitoring the passage of atmospheric disturbances in real time or to perform the reconstruction the dynamics of these events during past time using the short-period seismic signals recorded at the high heights.

Coastal response to the passage of tropical cyclone Juliette on the Central Pacific Coast of Mexico

In situ coastal oceanographic and meteorological data were collected on the Mexican Tropical Pacific coast near Barra de Navidad, Jalisco, Mexico during September 2001 from before and after the passing of Hurricane Juliette. When the leading and trailing edges of the hurricane passed through the study area, wind speeds reached 15 m s-1 and caused a significant deepening of the thermocline, mixing of the upper 40 m of the water column, and a rise in sea level of almost 50 cm at the coast, with effects lasting for about 5 days. A decrease in temperature and an increase in salinity occurred in the upper 20 m, with the opposite occurring below 20 m. Although analyses of open ocean responses to hurricanes are widely available from satellite data, in situ coastal water-column and sea-level data are difficult to acquire, yet crucial to inform coastal flooding models and risk assessment studies. This short data set provides a rare opportunity to explore in situ hurricane effects on this understudied coast.

Wavelet-based Characterization of Seismicity and Geomagnetic Disturbances in the South Sandwich Microplate Area

This paper analyzes geomagnetic disturbances associated with seismic events in the northern transcurrent margin of the South Sandwich microplate and South American plate, with their epicenter at distances within 350 km from King Edward Point geomagnetic observatory on the archipelago of the Georgias del Sur islands. Geomagnetic field records measured over a one-year period in three observatories of the INTERMAGNET network near the area under study are examined. Anomalous variations in geomagnetic records can be detected within approximately 3 hours before the manifestation of seismic events with a magnitude above 4.4 Mw. Based on the analysis of the differences in horizontal field components among the observatories and the frequency spectrum of the geomagnetic field observations using the wavelet method, oscillations of several nT can be observed before an event, in addition to magnetic peaks with variable amplitude and duration. It is worth noting that, during the period of study, no severe ionospheric effects were recorded as this was a phase of low solar activity (solar cycle 24 minimum). The observation of these potential magnetic precursors suggests that there is a critical preparatory period in a region with geological faults related to the stress generated in the rocks before the built-up energy is released in the hypocenter area, within the lithosphere, which may predict the mechanical motion based on anomalous geomagnetic records.