Evaluation of inundation areas resulting from the diversion of an extreme discharge towards the sea: case study in Tabasco,Mexico

This investigation comprises the hydraulic characterisation of a river located in the Mexican State of Tabasco, including the performance of its flood plain under the action of an extreme river discharge. This is done through the combination of a high‐quality validation dataset, remote sensing information, and a standard 2D numerical model. The dataset was collected during an intensive field campaign that took place in August 2009. In particular, in situ measurements of river discharge, bathymetry, water level, and velocities through a whole tidal cycle are employed along with multi‐spectral satellite imagery. The purpose of this study is twofold. Firstly, the integrated approach comprising the combination of a 2D hydrodynamic model, high‐quality in situ measurements and satellite imagery reduce the uncertainty in the model parameterisation and results. Secondly, it is shown that freely available sources of information, such as the Shuttle Radar Topographic Mission (SRTM) data can be processed and utilized in 2D hydraulic models. This is particularly important in countries where high‐resolution elevation data is not yet available. It is demonstrated that the selected approach is useful when the study of possible consequences in a flood plain induced by an extreme flood discharge are sought. Copyright © 2011 John Wiley & Sons, Ltd.     

Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations

We obtained estimates of the Johnson V absolute magnitudes (H) and slope parameters (G) for 583 main-belt and near-Earth asteroids observed at Ond?ejov and Table Mountain Observatory from 1978 to 2011. Uncertainties of the absolute magnitudes in our sample are <0.21 mag, with a median value of 0.10 mag. We compared the H data with absolute magnitude values given in the MPCORB, Pisa AstDyS and JPL Horizons orbit catalogs. We found that while the catalog absolute magnitudes for large asteroids are relatively good on average, showing only little biases smaller than 0.1 mag, there is a systematic offset of the catalog values for smaller asteroids that becomes prominent in a range of H greater than ～10 and is particularly big above H ～ 12. The mean (H_catalog ? H) value is negative, i.e., the catalog H values are systematically too bright. This systematic negative offset of the catalog values reaches a maximum around H = 14 where the mean (H_catalog ? H) is ?0.4 to ?0.5. We found also smaller correlations of the offset of the catalog H values with taxonomic types and with lightcurve amplitude, up to ～0.1 mag or less. We discuss a few possible observational causes for the observed correlations, but the reason for the large bias of the catalog absolute magnitudes peaking around H = 14 is unknown; we suspect that the problem lies in the magnitude estimates reported by asteroid surveys. With our photometric H and G data, we revised the preliminary WISE albedo estimates made by Masiero et al. (Masired, J.R. et al. [2011]. Astrophys. J. 741, 68–89) and Mainzer et al. (Mainzer, A. et al. [2011b]. Astrophys. J. 743, 156–172) for asteroids in our sample. We found that the mean geometric albedo of Tholen/Bus/DeMeo C/G/B/F/P/D types with sizes of 25–300 km is p_V = 0.057 with the standard deviation (dispersion) of the sample of 0.013 and the mean albedo of S/A/L types with sizes 0.6–200 km is 0.197 with the standard deviation of the sample of 0.051. The standard errors of the mean albedos are 0.002 and 0.006, respectively; systematic observational or modeling errors can predominate over the quoted formal errors. There is apparent only a small, marginally significant difference of 0.031 ± 0.011 between the mean albedos of sub-samples of large and small (divided at diameter 25 km) S/A/L asteroids, with the smaller ones having a higher albedo. The difference will have to be confirmed and explained; we speculate that it may be either a real size dependence of surface properties of S type asteroids or a small size-dependent bias in the data (e.g., a bias towards higher albedos in the optically-selected sample of asteroids). A trend of the mean of the preliminary WISE albedo estimates increasing with asteroid size decreasing from D ～ 30 down to ～5 km (for S types) showed in Mainzer et al. (Mainzer, A. et al. [2011a]. Astrophys. J. 741, 90–114) appears to be mainly due to the systematic bias in the MPCORB absolute magnitudes that progressively increases with H in the corresponding range H = 10–14.     

Degradation of 5α-cholestane into dimethylperhydrophenanthrenes: an experimental and theoretical study

A tetradeuteriated cholestane was heated with kerogen isolated from the Messel oil shale at 350 °C for 25 different time periods (ranging from 0.5 to 80 h) in borosilicate vessels. Three isomers of tetradeuteriated dimethylperhydrophenanthrene were formed and one of these was the major saturated hydrocarbon product under most conditions. The stereochemistry for these isomers was unknown but if the stable 5α,8β,9α(H),10β(CH₃) sterane configuration is inherited from the cholestane then there are four possible isomers namely: I and II [13β(H) and 13α(H) diastereomers, respectively, of 10,13-dimethylperhydrophenanthrene] as well as III and IV [14β(H) and 14α(H) diastereomers, respectively, of 10,14-dimethylperhydrophenanthrene]. Molecular mechanics revealed that I is the most stable form and therefore is the component that dominated the saturated hydrocarbon degradation products. The identification of only three isomers of deuteriated dimethylperhydrophenanthrene in the pyrolysis experiments is supported by the calculated stabilities (ΔΔG) as isomer IV is considerably more unstable (by 1.7 kcal/mol) than II which is the least stable of I, II and III. If these compounds can be detected in crude oils their distributions may be useful maturity indicators in oils that have been generated at high thermal maturity.     

Effects of hurricane Odile on the infrastructure of Baja California Sur,Mexico

In September 2014, the state of Baja California Sur (BCS), Mexico, was struck by hurricane Odile. The hurricane caused extensive damage to the infrastructure of the state of BCS, where the energy and water supply were interrupted for several days. The direct economic impact was estimated to be more than 1654 million USD. Considering this damage, few days after the cyclonic event, a technical visit to BCS was carried out. The objective of this study is to present the relevant information on the performance of the infrastructure observed after the event, and to make recommendations in order to mitigate the effects of future cyclonic storms in Mexico, based on the observations during the technical visit. The main causes of damage were the use of materials for non-structural elements with a weak performance under high wind speeds, failures in the design and construction of connections of structural and non-structural elements, accumulated damage, lack of maintenance and impact of wind-born debris, as well as the absence of a building code in the region. Background information about meteorological and climatological aspects of the cyclones that have affected the southern region of BCS, the characteristics of hurricane Odile, the analysis of structural damages and the conclusions, are also presented.     

Mineralogy,alteration patterns,geochemistry, and fluid properties of the Ag-Au epithermal deposit Nová Baňa,Slovakia

Mineralogy and Petrology - In this contribution, we report new data on mineralogy, alteration patterns, geochemistry, fluid properties and source of fluids for the deposit Nová Baňa, one...     

What feeds shelf-edge clinoforms over margins deprived of adjacent land sources? An example from southeastern Brazil

In southeastern Brazil, the Serra do Mar coastal mountain range blocks the sediment influx from arriving at a ca. 1,500 km long continental margin comprising Santos and Pelotas basins. Despite this deprivation, the margin accumulated a ca. 1 km thick sedimentary succession since the Mid-Miocene. Examination of seismic reflection and oceanographic data indicates that shelf-margin clinoform formation exhibits a regional variability, with major sigmoidal clinoforms developed in the transitional area between both basins. Laterally, poorly developed oblique clinoforms constitute isolated depocenters along the shelf margin. The continuous clinoform development in the transitional area is attributed to the major influence on sediment transport patterns of several ocean bottom currents flowing along the margin, such as the Brazil Coastal Current, the Brazil Current and the Intermediate Water Brazil Current. These currents erode, transport and distribute sediments across the shelf break and upper slope from distant sediment sources located either north or south of the study area. The progressive southward strengthening of the Brazil Current could be responsible for a major southward sediment redistribution from the northern Campos Basin, and/or for sediment entrainment from northward-induced transport by the Brazil Coastal Current, originally derived from the De la Plata Estuary. In the transition between Santos and Pelotas basins, the Intermediate Water Brazil Current splits forming the Santos Bifurcation, allowing for a continuous depositional process and clinoform generation. We suggest that ocean bottom currents may shape other shelf-edge ‘contouritic clinoforms’ in continental margins mainly constructed by along-strike sediment transport largely driven by long-term geostrophic currents.     

Beach recovery capabilities after El Niño 2015–2016 at Ensenada Beach,Northern Baja California

This study investigates the recovery capabilities of a single-barred beach in the Pacific Mexican coast before and after the 2015–2016 El Niño winter. Concurrent hydrodynamic and morphological data collected over a 3-year period (August 2014–2017) were analysed to determine the subaerial-subtidal volumetric exchange and cross-shore subtidal sandbar migrations, in relation to the incident wave forcing. The beach presented a seasonal seaward and landward sandbar migration cycle. The sandbar migrated offshore during the energetic waves between November and February, and onshore during the milder wave period in spring, until welding to the subaerial beach around May. The transfer of sediment towards the subaerial section continued over the summer, reaching a complete recovery by September/October. Prior to El Niño, the subaerial beach successfully recovered by the end of summer 2015 through the landward sandbar migration process. The 2015–2016 energetic winter waves caused a subaerial volume loss of ~ 140 m³ m^?1 (from October 2015 to March 2016), more than twice the amount eroded in the other winters, and the sandbar moved further offshore and to deeper depths (3–4 m) than the winter before. In addition, the energetic 2015–2016 winter waves lasted for 2 months longer than in other years, making the 2016 spring shorter. Consequently, during the onshore migration, the sandbar was unable of reaching shallow depths, and a large portion of sand remained in the subtidal beach. The subaerial beach recovered 60 and 65% of the loss in the 2016 and 2017 summers, respectively. It is concluded that the landward migration process of the sandbar during the spring is critical to ensure a full subaerial beach recovery over the mild wave period in summer. The recovery capabilities of the subaerial beach will depend on the cross-shore distance and depth where the sandbar is located, and on the duration of mild wave conditions required for the sandbar to migrate onshore.     

Organic complexation and its control of the dissolved concentrations of copper and zinc in the Scheldt estuary

Cathodic stripping voltammetry (CSV) is used to determine total (after UV-irradiation) and labile dissolved metal concentrations as well as complexing ligand concentrations in samples from the river Scheldt estuary. It was found that even at high added concentrations of catechol (1 m for copper and 0·4 m for iron) and of APDC (1 m for zinc) only part of the dissolved metal was labile (5–58% for copper, 34–69% for zinc, 10–38% for iron); this discrepancy could be explained by the low solubility of iron which is largely present as colloidal material, and by competition for dissolved copper and zinc by organic complexing ligands. Ligand concentrations varied between 28 and 206 n for copper and between 22 and 220 n for zinc; part of the copper complexing ligands could be sub-divided into strong complexing sites with concentrations between 23 and 121 n and weaker sites with concentrations between 44 and 131 n . Values for conditional stability constants varied between (logK′ values) 13·0 and 14·8 for strong and between 11·5 and 12·1 for weaker copper complexing ligands, whereas for zinc the values were between 8·6 and 10·6. The average products of ligand concentrations and conditional stability constants (a-coefficients) were 6 × 10² for zinc and 6 × 10⁶ for copper.The dissolved zinc concentration was found to co-vary with the zinc complexing ligand concentration throughout the estuary. It is argued that the zinc concentration is regulated, in this estuary at least, by interactions with dissolved organic complexing ligands. A similar relationship was apparent between the dissolved copper and the strong copper complexing ligand concentration. The total copper complexing ligand concentrations were much greater than the dissolved copper concentrations, suggesting that only strongly complexed copper is kept in solution.These results provide evidence for the first time that interactions of copper and zinc with dissolved organic complexing ligands determine the geochemical pathway of these metals.