The impact of a storm surge on business establishments in the Houston MSA

This paper examines the possible storm surge damage from a major hurricane to hit the Houston Metropolitan Statistical Area (MSA.) Using storm surge analysis on a unique data set compiled from the Texas Workforce Commission (QCEW), the paper estimates the expected industry-level damage for each county in the Houston MSA. The advantages of using GIS to analyze the expected storm surge damage estimation is that it provides an accurate estimation of the number of affected employees and probable wages losses, by industry and county, based on QCEW data. The results indicate that the ‘Basic Chemical Manufacturing’ and ‘Oil and Gas Extraction’ industries incur the highest employee and payroll losses while the ‘Restaurants and Eateries’ has the largest establishment damage if a major hurricane were to hit the Houston MSA.     

Geologie und Erdöl von Comodoro Rivadavia (Patagonien)

Ohne Zusammenfassung     

A survey of groundwater quality in Tulum region,Yucatan Peninsula,Mexico

The city of Tulum, in the state of Quintana Roo (Mexico) depends almost exclusively on groundwater for water supply. The groundwater is exploited from a coastal aquifer which contains a karst network that is considered as one of the largest ones on earth. Given the nature of karst aquifers, the whole area is very sensitive to contaminants and bacteria transport, because flow paths, residence time and degradation rates differ significantly from what can be observed in the porous aquifer. The present study focuses on isotopes (¹⁸O and ²H), dissolved ions’ concentration and Escherichia coli (E. coli). The result of our survey points out the anthropic impact on groundwater quality. Furthermore, the chloride concentrations illustrate the influence of seawater mixing and geological heterogeneity over the study area. Due to an exponential growth of the tourism industry, the needs in terms of water supply and water treatment increase significantly. Tulum is a coastal city, facing a coral reef and is bordered by the Sian Ka’an biosphere reserve, therefore, an environmental issue is added to the sanitary issue, both being the basis of the local economic development. Our results show that E. coli remains a major issue, as several samples tested were contaminated, in particular those in the city center. Ions’ survey shows an anthropic impact through nitrate, phosphate and fluoride concentrations, but the obtained values are not alarming. Considering the saline intrusion, chloride concentrations indicate that the area below the Tulum city center seems to be less permeable (and maybe less karstified) than the surrounding areas, as groundwater is less subject to seawater mixing than other sampling sites at similar distance to the coast.     

Über Schichten-Zusammensinken in Patagonien infolge von Unterwaschung

Ohne Zusammenfassung     

Modeling of asymmetric light curves of eclipsing binaries on the Cyber 205 supercomputer

A major program at the University of Calgary's Rothney Astrophysical Observatory (RAO) is the study of eclipsing close-binary stars, which, because of circularization effects, are all cases of the restricted three-body problem. The physical properties of such systems are derived from modeling of the light and radial velocity curves. Uniqueness questions notwithstanding, careful use of the technique is found to yield reliable elements of the orbit and parameters of the component stars, even in the face of light curve perturbations. This work requires a greatly enlarged data base over previous work, and more complex modeling procedures, necessitating the use of a supercomputer. A version of the generalized synthetic light curve program of Wilson (1979) with star spot simulations has been adapted to and optimized for the University of Calgary's Cyber 205 supercomputer and further improvements are underway. With the use of personal computer graphics software, results have been transformed into three-dimensional, rotating models which help visualize the overcontact and perturbation conditions.     

Low Ozone Episodes at Amphitrite Point Marine Boundary Layer Observatory,British Columbia,Canada

At Amphitrite Point, ozone (O₃) mixing ratios are observed to drop steadily to 5–15?ppb over a period of 12 hours or less with a frequency approaching one event per week (with highest frequencies occurring in summer and fall). Analysis of 47 such O₃ depletion events reveals that low O₃ episodes are a predominantly nocturnal phenomenon associated with anticyclonic conditions characterized by light onshore or alongshore winds and an absence of fog and mist. Back-trajectories show air carried to the Amphitrite Point Observatory (APO) during depletion events remains in the marine boundary layer and is not brought to the surface from aloft. There is no strong correlation with other “criteria” pollutants (CO, NO_x, SO₂, PM_2.5) that might be indicative of a mechanism for O₃ destruction linked to human, terrestrial, or marine pollutant sources. However, CO₂ mixing ratios are observed to increase, coincident with O₃ depletion. Together, these results point to a natural marine boundary layer phenomenon in which O₃ destruction dominates O₃ production and/or replenishment by vertical mixing. While there are several candidate mechanisms, the conditions for O₃ depletion (and CO₂ buildup) to occur are set by meteorology and, in particular, development of a stable marine boundary layer in which vertical mixing is suppressed. Support for this interpretation is provided by simultaneous increases in CO₂ in the stable marine boundary that are indicative of an important role played by marine biogenic processes (respiration). Future research should be directed at elucidating the chemical mechanisms responsible for O₃ destruction in the coastal zone, which means that there would be a need for a much broader range of measurements at APO (including halogenated species) as well as offshore measurements of both chemical and marine boundary layer meteorological variables.     

Variation in nitrate uptake and denitrification rates across a salinity gradient in Mediterranean semiarid streams

Streams are significant locations for nitrate (NO₃ ^?) processing within landscapes. This is especially important in dry climates given the limited water availability for biological processes elsewhere. In arid and semiarid regions, many streams are naturally saline. Elevated salinity can constrain the structure and function of aquatic organisms, which is expected to increase worldwide being associated to global warming. We investigated whole-reach NO₃ ^? uptake and denitrification in nine semiarid streams of variable water salinity (i.e. from freshwater to hyposaline) to test if NO₃ ^? processing would decrease with increasing salinity. We used pulse additions and Tracer Addition for Spiraling Curve Characterization (TASCC) to measure whole-reach uptake of added NO₃ ^?, and the acetylene block technique to measure sediment denitrification. TASCC results showed that only five of nine streams were able to retain added NO₃ ^?. Of these five retentive streams, four were saline; however, salinity did not control significantly the variation in whole-reach NO₃ ^? uptake observed across streams. Other measured environmental variables such as streambed NH₄ ⁺ and organic carbon availability were better at explaining this variation. Denitrification was detected in all streams except one and its variation across streams was also independent of salinity. Although denitrification rates tended to be high, their contribution to whole-reach NO₃ ^? uptake was insignificant (≤2.16 %). Alternative pathways, heterotrophic assimilation and/or dissimilatory NO₃ ^? reduction to NH₄ ⁺, were probably responsible for most whole-reach NO₃ ^? uptake. Together, our results highlight that the function of streams in controlling external NO₃ ^? inputs is highly variable and salinity does not apparently constrain this role.     

Preconditioning effects of intermittent stream flow on leaf litter decomposition

Autumnal input of leaf litter is a pivotal energy source in most headwater streams. In temporary streams, however, water stress may lead to a seasonal shift in leaf abscission. Leaves accumulate at the surface of the dry streambed or in residual pools and are subject to physicochemical preconditioning before decomposition starts after flow recovery. In this study, we experimentally tested the effect of photodegradation on sunlit streambeds and anaerobic fermentation in anoxic pools on leaf decomposition during the subsequent flowing phase. To mimic field preconditioning, we exposed Populus tremula leaves to UV–VIS irradiation and wet-anoxic conditions in the laboratory. Subsequently, we quantified leaf mass loss of preconditioned leaves and the associated decomposer community in five low-order temporary streams using coarse and fine mesh litter bags. On average, mass loss after approximately 45 days was 4 and 7% lower when leaves were preconditioned by irradiation and anoxic conditions, respectively. We found a lower chemical quality and lower ergosterol content (a proxy for living fungal biomass) in leaves from the anoxic preconditioning, but no effects on macroinvertebrate assemblages were detected for any preconditioning treatment. Overall, results from this study suggest a reduced processing efficiency of organic matter in temporary streams due to preconditioning during intermittence of flow leading to reduced substrate quality and repressed decomposer activity. These preconditioning effects may become more relevant in the future given the expected worldwide increase in the geographical extent of intermittent flow as a consequence of global change.     

Vulkanischer Aschenregen im La Plata-Gebiete am 11./12. April 1932

Ohne Zusammenfassung