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31.
For the first time Arundian and Holkerian faunas have been recognized from the lower part of the Dinantian succession in North Wales. These limestones and sandstones, hitherto regarded as Asbian, have a macrofauna and microfauna confirming their older age, and this discovery' has necessitated a revision of the palaeogeography in the North Wales region. Biostratigraphical correlations have been made with contemporaneous platform successions in the Central, Northern, and Southwest Provinces of Britain. A new genus and species of foraminifer, Groessensella moldensis, is described. 相似文献
32.
J. Phelps M.C. Guerrero D.A. Dalabajan B. Young E.L. Webb 《Global Environmental Change》2010,20(2):322-332
Despite remaining uncertainties, Reducing Emissions from Deforestation and forest Degradation in developing countries (REDD) projects are being planned and implemented across the tropics, primarily targeting countries with high forest cover and high deforestation rates. However, there is growing recognition that REDD planning requires a broadened approach; a future REDD mechanism should incentivise emissions reduction in all developing forested countries, and should address critical non-carbon dimensions of REDD implementation—quality of forest governance, conservation priorities, local rights and tenure frameworks, and sub-national project potential. When considering this broader suite of factors, different REDD priorities can emerge, including in countries with low forest cover that would be overlooked by conventional site selection criteria. Using the Philippines as a case study, the paper highlights the importance of an enabling environment to REDD implementation, and presents a more comprehensive and inclusive approach for thinking about what comprises a “REDD country.” 相似文献
33.
Chemical degradations of coal resins, coal asphaltenes and coal residues have been performed with selective, non-oxidative reagents. The coal comprise samples a rank interval 0.30–1.21 %Rm. Degraded low-molecular-weight compounds were analyzed by GC-MS. The distributions of pentacyclic terpanes, isoprenoids, n-alkanes, acids and alcohols obtained as degradation products illustrate a considerable variability between the macromolecular coal fractions. A structural study on the molecular level of the degraded compounds from coal resins and coal asphaltenes show their potential to generate hydrocarbons during coalification process. 相似文献
34.
Martin Wessels Angela Lenhard Federico Giovanoli Andreas Bollhöfer 《Aquatic Sciences - Research Across Boundaries》1995,57(4):291-304
Sediments in Lake Constance have been dated by radiometric methods and lamination counting. Investigations into the concentrations of lead and zinc in the sediments were carried out to get detailed information about environmental history. Maximum concentrations were found at the beginning of the 1960's. The lead maximum contamination occurred 3 years before the zinc maximum and has an unidentified source. The use of coal, leaded gasoline or the remobilization within the sediment could be excluded to result in the lead maximum. The fluctuations in zinc contamination could be explained with increasing and decreasing pollution (industry, coal burning, building of sewage plants). The greatest fluctuations of both metals occur during periods of great change in the economic history of Germany. 相似文献
35.
The aqueous geochemistry of Zn, Cu, Cd, Fe, Mn and As is discussed within the context of an anaerobic treatment wetland in Butte, Montana. The water being treated had a circum-neutral pH with high concentrations of trace metals and sulfate. Reducing conditions in the wetland substrate promoted bacterial sulfate reduction (BSR) and precipitation of dissolved metal as sulfide minerals. ZnS was the most common sulfide phase found, and consisted of framboidal clusters of individual spheres with diameters in the submicron range. Some of the ZnS particles passed through the subsurface flow, anaerobic cells in suspended form. The concentration of "dissolved" trace metals (passing through a 0.45 μm filter) was monitored as a function of H2S concentration, and compared to predicted solubilities based on experimental studies of aqueous metal complexation with dissolved sulfide. Whereas the theoretical predictions produce "U-shaped" solubility curves as a function of H2S, the field data show a flat dependence of metal concentration on H2S. Observed metal concentrations for Zn, Cu and Cd were greater than the predicted values, particularly at low H2S concentration, whereas Mn and As were undersaturated with their respective metal sulfides. Results from this study show that water treatment facilities employing BSR have the potential to mobilize arsenic out of mineral substrates at levels that may exceed regulatory criteria. Dissolved iron was close to equilibrium saturation with amorphous FeS at the higher range of sulfide concentrations observed (>0.1 mmol H2S), but was more likely constrained by goethite at lower H2S levels. Inconsistencies between our field results and theoretical predictions may be due to several problems, including: (i) a lack of understanding of the form, valence, and thermodynamic stability of poorly crystalline metal sulfide precipitates; (ii) the possible influence of metal sulfide colloids imparting an erroneously high "dissolved" metal concentration; (iii) inaccurate or incomplete thermodynamic data for aqueous metal complexes at the conditions of the treatment facility; and (iv) difficulties in accurately measuring low concentrations of dissolved sulfide in the field. 相似文献
36.
Angela Marinoni Paolo Laj Pierre Alexandre Deveau Federica Marino Grazia Ghermandi Fabien Aulagnier Hlne Cachier 《Atmospheric Research》2005,74(1-4):565-580
The physical and chemical properties of aerosol particles were investigated at Plan d'Aups, one of the ESCOMPTE sites located in the St. Baume mountain area (700 m a.s.l.), 50 km east of Marseilles (France). The site is ideally located for assessing the vertical and horizontal extent of the pollution plume from the Marseilles–Berre area.Our study showed that polluted air masses from the Marseilles–Berre area are advected to Plan d'Aups in the early afternoon. Average daily concentration of particles reaches up to 40 μg m−3 while 1-h average particle number concentration is greater than 30,000 cm−3. Most of the particle mass is composed of SO42− and organic carbon (OC). The chemical properties of the particles revealed that an additional source, possibly from the industrial area of Gardanne, contributes to the aerosol mass. This last source is characterised by significant emissions of elements, such as Zn, V, Al and Si.In addition to transport, we found that gas-to-particle conversion takes place at the interface between the free troposphere and the boundary layer. We estimated that on average, 30% of the particle number is accounted for by direct nucleation. This is potentially a major aerosol source to the free troposphere. 相似文献
37.
Glria da Silva Cezar Paula Lucia Ferrucio da Rocha Angela Buarque Ariovaldo da Costa 《Journal of Applied Geophysics》2001,47(3-4)
The application of the ground penetrating radar (GPR) at two archaeological sites, Serrano and Morro Grande, situated in Araruama County, Rio de Janeiro, Brazil, aids the study of a prehistoric indigenous culture, associated with the “Tupinambá” that inhabited the region during prehistoric times.The archaeological remains of the study area are mainly characterized by pottery artifacts for several uses, including funerary urns, which were buried within layers of sand and clay. Several profiles were acquired using a RAMAC system, with a 200 and 400 MHz frequency antennae. At the Serrano site, the profiles were acquired around some partially exposed pottery shards, due to sand exploitation. The resultant profiles provided a response model to guide the interpretation of new profiles acquired at other sites in the area, which present similar characteristics.The results showed the great importance of the dielectric permittivity contrast which exists between the targets and the host media, in order for possibly significant features to be identified in radar data. 相似文献
38.
Jean-François Chiffoleau Dominique Auger Emmanuelle Chartier Pierre Michel Isabelle Truquet André Ficht Jean-Louis Gonzalez Louis-Alexandre Romana 《Estuaries and Coasts》2001,24(6):1029-1040
Cadmium (Cd) is among the major contaminants in the Seine estuary. In the biota, the RNO (Réseau National d’Observation, the French Mussel-Watch) has shown that Cd concentrations in mussels living at the mouth of the estuary are related to changes in inputs to this area of phosphogypsum, a calcium sulphate that is a by-product of the phosphoric acid naturally enriched with Cd. In the water column, Cd concentrations at several key estuary sites show a very marked trend toward decreased contamination in the particles as well as in the dissolved phase. The behavior of Cd in the estuary has been studied between 1991 and 1998 in the framework of the scientific program Seine-Aval. This program has highlighted punctual Cd inputs in the estuarine water column. The partition of Cd between the dissolved and the particulate phase, previously described in various estuaries, is characterized by an intense phenomenon of solubilization in the mixing zone freshwater-seawater, but the colloidal Cd fraction remains low along the whole salinity gradient, about 5% to 10% of the apparent dissolved fraction. Although the decrease of inputs induced a fall of Cd concentrations in the water column, laboratory experiments show that the estuarine particles are far from being exhausted in Cd. Despite continuous efforts to reduce the urban and industrial inputs into the estuarine and coastal waters, the Seine estuary still remains very contaminated by Cd. 相似文献
39.
Michele Bossi Gianantonio Guerrero Luciano Mantegazza Marco Scardia 《Astrophysics and Space Science》1982,85(1-2):25-29
Photoelectric observations of the Delta Scuti star KW 207 (HD 73576) are given. In spite of the low variations, the analysis of the light curves shows at least two sighificant periodicities, which seem to be related to non-radial pulsations.A third frequency, corresponding to the radial fundamental mode, is probably bame out by our data. 相似文献
40.
Angela M. Gurnell 《Applied geography (Sevenoaks, England)》1981,1(3):167-183
The criteria which may be employed when selecting an approach to a particular evapotranspiration mapping problem are discussed in the light of previous attempts at mapping evapotranspiration. Evapotranspiration mapping involves two main stages: firstly the derivation of point evapotranspiration estimates, and secondly the interpolation of isolines around these estimates. Many studies have emphasized the first stage, frequently applying estimation formulae to data from climate stations, and have given substantially less attention to the interpolation of isolines. In the present study, where potential evapotranspiration estimates were derived for only 70 stations over the area of the European Economic Community and where maps showing the general trends in potential evapotranspiration were required, the technique of isoline interpolation was of great importance. Two forms of polynomial trend surface analysis were applied to the point estimates and a technique employing a restricted use of all three dimensions of location was found to be appropriate for denning the position of the smoothed evapotranspiration isolines. 相似文献