Calculation of free seepage from watercourses with curvilinear profiles

A strict hydromechanical solution is given to the problem of free seepage from watercourses (rivers, canals, water bodies, industrial and agricultural ponds) for a family of smooth and complex curvilinear profiles with the use of conformal mappings and with the representation of the flow domain as the basis of the water-course profile in the Zhukovski complex domain. All necessary parameters of the flow are determined, including the outline of the curvilinear profile of the watercourse, depression curves and constant pressure lines (isobars), seepage flow, etc. For the particular case of a circular base of the watercourse profile, the results of obtained solution coincide with the known exact solutions derived by V.V. Vedernikov and N.N. Pavlovskii. Specific numerical examples of calculations for watercourses with different relative widths are given.     

Prediction of the abiotic degradability of organic compounds in the troposphere

A statistically relevant correlation between the reaction rate coefficient, k _OH, for the OH radical reaction with 161 organic compounds in the gas phase at 300 K, and the corresponding vertical ionisation energies E _i,v, reveals two classes of compounds: aromatics where –log(k _OH/cm³s^-1)3/2E _i,v(eV)–2 and aliphatics where –log(k _OH/cm³s^-1)4/5E _i,v(eV)+3. The prediction of the rate coefficient, k _OH, for the reaction of OH with organic molecules from the above equations has a probability of about 90%. Assuming a global diurnal mean of the OH radical concentration of 5×10⁵ cm³, the upper limit of the tropospheric half-life of organic compounds and their persistence can be estimated.     

Die Bedeutung der Versumpfung für die Entstehung von Hochmooren in Deutschland

Zusammenfassung Es ist nur bei Gebirgsmooren zulässig, von Versumpfungsmooren zu reden. Die als solche erscheinenden Hochmoore des Flachlandes dürften in der Mehrzahl der Fälle keine Versumpfungsmoore im engeren Sinne sein, sondern nur durch Versumpfugserscheinungen in ihrer Ausbreitung geförderte Hochmoore, die ursprünglich als Hochmoore auf eutrophen und mesotrophen Moorschichten begannen (sogen. kombinierte Profile).Das Vorhandensein von Hochmooren des Flachlandes, die wirklich durch Versumpfung ins Leben gerufen worden sind, ist erst noch zu beweisen.     

The geochemistry of uranium occurrences and speciation in groundwater of Chinnar sub basin,South India

An attempt has been made in Chinnar sub basin of Dharmapuri district, South India to isolate the geochemistry of uranium occurrences in groundwater. The geology of the area is mainly of charnockite and granite gneiss. Groundwater samples were collected for two different seasons post and pre monsoon in two different litho units (granite gneiss and charnockite) and analysed for major, minor and uranium concentrations. Higher uranium (18.45 μg L^?1) has been recorded during pre monsoon season in granite gneiss with increasing pH. The saturation index calculation for the groundwater isolated minerals like uaraninite, coffinite, haiweeite and soddyite to be precipitating and uranium oxides like UO_2.25, UO_2.25beta, UO_2.33beta as oversaturated. The Eh-pH diagram attempted represents solubility of uraninite within the pH range of 6.0 to 8.0. The study isolate uranium in groundwater of the study area is controlled by the presence of (U₄O₉) uranium oxide.     

Groundwater Evolution and Mineral Alteration Reactions in the Basaltic Rock Sequence of Mt. Wasserkuppe, Germany: A Case Study

Groundwater sampling was accomplished in the basaltic sequence of the Rh?n mountain range, Germany, in order to investigate hydrochemical groundwater evolution and to delineate mineral alteration reactions involved in natural weathering. The hydrochemical compositions of near-surface groundwaters indicate a Ca/Mg–HCO₃ type with near-neutral pH and evolve to a Na–HCO₃ type with high pH at greater depth. Column experiments were performed with basaltic and phonolitic rock samples to determine individual mineral alteration reactions. The basic reactions could be related to the alteration of olivine, Ca-pyroxene, plagioclase, pyrrhotite, and feldspathoids under formation of secondary clay minerals (smectites, illite) and goethite. The mineral alteration reactions deduced from the leaching experiments by inverse modelling were found to be consistent with the mineral reactions associated with the natural groundwaters. The reactions calculated for groundwater evolution involve the alteration of primary and secondary minerals to produce low-T mineral phase. The conversion of secondary Na-beidellite to illite occurs at a later stage of groundwater evolution, reducing the concentrations of K⁺ and Mg²⁺. Near-surface groundwaters do not indicate significant cation exchange. Initial cation exchange requires elevated pH values, with Mg²⁺ removed from solution preferred to Ca²⁺. Na-alkalisation of the groundwaters at greater depth suggests the exchange of Na⁺ for Mg²⁺ and Ca²⁺ on Na-beidellite, supported by cation exchange on coatings of iron hydroxides as alteration products. Among the mature high-pH groundwater at greater depth, the dissolution of anorthite and albite has significant effect on groundwater composition.     

Sporadic and recurrent geomagnetic disturbances in 1859–1860 according to the archived data from the Russian network of stations

Based on an analysis of the available archived data from the Russian network of geomagnetic stations, it has been indicated that the known event of August–September 1859 was the first and the greatest event in the series of the recurrent geomagnetic storms. Similar series were repeatedly observed in the next years. These series are caused by the processes on the Sun and in the heliosphere related to the superposition of the solar wind flows. The sporadic and regular components in joint activity of the complex, including active regions and coronal holes on the rotating Sun, play the role of the Bartels M regions responsible for initiation and development of geomagnetic storms. Neither coronal holes nor active regions can separately explain observations. During interpretation, active regions and coronal holes should be considered as a unified complex.     

Hypoxia in the northern Gulf of Mexico: Does the science support the Plan to Reduce,Mitigate, and Control Hypoxia?

We update and reevaluate the scientific information on the distribution, history, and causes of continental shelf hypoxia that supports the 2001 Action Plan for Reducing, Mitigating, and Controlling Hypoxia in the Northern Gulf of Mexico (Mississippi River/Gulf of Mexico Watershed Nutrient Task Force 2001), incorporating data, publications, and research results produced since the 1999 integrated assessment. The metric of mid-summer hypoxic area on the LouisianaTexas shelf is an adequate and suitable measure for continued efforts to reduce nutrients loads from the Mississippi River and hypoxia in the northern Gulf of Mexico as outlined in the Action Plan. More frequent measurements of simple metrics (e.g., area and volume) from late spring through late summer would ensure that the metric is representative of the system in any given year and useful in a public discourse of conditions and causes. The long-term data on hypoxia, sources of nutrients, associated biological parameters, and paleoindicators continue to verify and strengthen the relationship between the nitratenitrogen load of the Mississippi River, the extent of hypoxia, and changes in the coastal ecosystem (eutrophication and worsening hypoxia). Multiple lines of evidence, some of them representing independent data sources, are consistent with the big picture pattern of increased eutrophication as a result of long-term nutrient increases that result in excess carbon production and accumulation and, ultimately, bottom water hypoxia. The additional findings arising since 1999 strengthen the science supporting the Action Plan that focuses on reducing nutrient loads, primarily nitrogen, through multiple actions to reduce the size of the hypoxic zone in the northern Gulf of Mexico.     

Sr-isotope stratigraphy of the Upper Jurassic of central Portugal (Lusitanian Basin) based on oyster shells

Strontium isotope stratigraphy was performed on oyster shells from the Late Jurassic of the Lusitanian Basin (central Portugal). This represents the first approach to obtain numerical ages for these strata. The new chronostratigraphic data provide a more precise age determination of several units. After a basin-wide hiatus sedimentation in the Late Jurassic is proven in the Cabo Mondego and Cabaços formations to resume as early as the Middle Oxfordian. The Alcobaça formation can be placed in the latest Late Oxfordian to Late Kimmeridgian, while data from the upper part of the Abadia Formation indicate an Early to Late Kimmeridgian age. The Farta Pao formation ranges from the latest Kimmeridgian to the latest Tithonian. The largely synchronous Sobral, Arranhó I, and Arranhó II members are overlain by the late Early to Late Tithonian Freixial Member. The brief, local carbonate incursion of the Arranhó I member marks the Kimmeridgian–Tithonian boundary. Oysters are shown once more to be suitable for strontium isotope studies. Their calcitic shells are often unaffected by diagenesis. In particular for marginal marine Jurassic and Cretaceous strata, where belemnites are usually absent, oysters may serve as a valuable tool for isotope stratigraphy.     

Annealing studies of fission tracks in allanite

The annealing characteristics of fission tracks in allanite have been studied. All the tracks in the mineral fade at 720° C for one hour heating. The activation energy of allanite ranges from 1.4 to 3.4 eV.     

Probabilities of occurrence of great earthquakes in the Himalaya

Long-term conditional probabilities of occurrence of great earthquakes along the Himalaya plate boundary seismic zone have been estimated. The chance of occurrence of at least one great earthquake along this seismic zone over a period of 100 years (beginning the year 1999) is estimated to be about 0.89. The 100-year probability of such an earthquake occurring in the Kashmir seismic gap is about 0.27, in the central seismic gap about 0.52 and in the Assam gap about 0.21. The 25-year probabilities of their occurrence in these gaps are 0.07, 0.17, and 0.05 respectively. These probability estimates may be used profitably to assess the seismic hazard in the Himalaya and the adjoining Ganga plains.