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81.
J. Keder M. Střižík P. Berger A. Černý P. Engst I. Němcová 《Meteorology and Atmospheric Physics》2004,85(1-3):155-164
Summary Air pollution problem in the Czech Republic is very complex due to large number of factors as turbulent dispersion and chemical reactions concurring in the status of the PBL. For this 3D distribution of pollutants is a key information that cannot be given by conventional monitoring stations. Combined use of DIAL lidar and sodar can give access to such information. Case studies of air pollutants transport are presented using 3D concentration fields of NO2 and ozone measured by lidar and meteorological conditions monitored by Doppler Sodar. 相似文献
82.
F. García-Rodríguez D. Metzeltin P. Sprechmann R. Trettin G. Stams L.F. Beltrán-Morales 《Journal of Paleolimnology》2004,32(2):117-135
Paleolimnological data are presented on trophic development in relation to sea level variation in Rocha Lagoon, a 72 km2 coastal lagoon in southern Uruguay. Using sediment cores that extended to ∼20,000 yr BP, analyses of grain size, organic matter, carbonate, total carbon, nutrients, and diatoms allowed us to infer changes in trophic state and paleosalinities, which were closely related to Holocene relative sea level variation. Higher trophic states were observed during regressive events, most probably due to increases in runoff and erosion as regressions progressed. Diatom Association Zones (DAZ) were identified in both cores. Those DAZ corresponding to transgressive events were dominated by marine/brackish taxa and relatively low organic matter and nutrient values, while those DAZ corresponding to regressive events showed increases in brackish/freshwater diatoms and both organic matter and nutrients. Although the lagoon formed after the first Holocene marine transgression, our data indicate the existence of a marine/brackish aquatic system during upper Pleistocene (i.e., before 15,000 yr BP), but by ∼20,000 yr BP, the system was still likely to be a semi-arid terrestrial system. 相似文献
83.
V Sanfelix ET Gòmez MM Jordán T Sanfeliu S Pallarés AB Vicente 《Environmental Geology》2005,47(6):811-819
The objective of this work is to assess the concentrations of three factions of air particles (settable particles, TSP and PM10) and the levels of several toxic elements in a clay atomisation industry through aerosol sampling at several points inside an industrial plant. Mechanical activities, which produce diffuse emissions, are the main process of discharge of particles in both indoor and outdoor workplace environments in the atomisation plant. The levels of As, Cd, Pb, Zn, Ba and Ni increase in the zones with higher concentrations of particles and lower ventilation. The concentrations of As and F are not influenced by the recycling processes. The levels of Cd and Pb do not show great enrichment in air particles collected inside the atomisation plant although the content of both elements is associated with ceramic muck recycling. Finally, the content of B in waste water is mainly transferred in gaseous phase to the atmosphere during the process of drying by atomisation. 相似文献
84.
SVLBI (space very long baseline interferometry) has some important potential applications in geodesy and geodynamics, for which one of the most difficult tasks is to precisely determine the orbit of an SVLBI satellite. This work studies several technologies that will possibly be able to determine the orbit of a space VLBI satellite. Then, according to the types and charac- teristics of the satellite and the requirements for geodetic study and the geometry of the GNSS (GPS, GALILEO) satellite to track the space VLBI satellite, the six Keplerian elements of the SVLBI satellite (TEST-SVLBI) are determined. A program is designed to analyze the coverage area of space of different altitudes by the stations of the network, with which the tracking network of TEST-SVLBI is designed. The efficiency of tracking TEST-SVLBI by the network is studied, and the results are presented. 相似文献
85.
86.
The possibility of filling empty underground spaces, which exist owing to the extraction of mineral raw materials, with fly
ash and cement fly ash mixes has been studied for the purpose of reducing the impact of deep mining on the surface. The method
of physical modelling was used to study the behaviour of fly ash mixes deposited in extracted mine spaces. The models were
constructed for two different geometries of underground extracted mine spaces: into cavities of the type of large slits created
in the course of mining in steeply lode deposits without subsequently filling the empty space and in vertical shafts of rectangular
or circular cross-section with horizontal side headings that have partly caved in due to mine shocks or other seismic events. 相似文献
87.
The percentage calculation of crystalline phases in atmospheric particulate matter samples by means of an adiabatic approach of the matrix-flushing method with preferred preparations that avoids preferential orientations, should never be interpreted as absolute values. On the contrary, it should be seen as an indicator of the significant differences between each and every analyzed sample. Factors such as the application of constants, which are only useful for preparations of polycrystalline samples free of preferential orientation, and/or like the deficient resolution shown by the diffraction diagrams for certain phyllosilicate phases, bring a high degree of uncertainty to these percentage calculations. An alternative method of crystalline and amorphous phase quantification is presented below. Once the majority phases in the samples were identified, appropriate pure phases corresponding to each of them were selected. Then, the corresponding calibration curves were built using corundum (number 676 NIST) as a reference pattern phase. After validating the obtained calibration curves, the constants corresponding to each phase and selected spacing were calculated. The ALJOR method has been used for the quantification of five samples. 相似文献
88.
The soil leakage ratio in the Mudu watershed,China 总被引:3,自引:0,他引:3
89.
New spherical integral formulas between components of the second- and third-order gravitational tensors are formulated in this article. First, we review the nomenclature and basic properties of the second- and third-order gravitational tensors. Initial points of mathematical derivations, i.e., the second- and third-order differential operators defined in the spherical local North-oriented reference frame and the analytical solutions of the gradiometric boundary-value problem, are also summarized. Secondly, we apply the third-order differential operators to the analytical solutions of the gradiometric boundary-value problem which gives 30 new integral formulas transforming (1) vertical-vertical, (2) vertical-horizontal and (3) horizontal-horizontal second-order gravitational tensor components onto their third-order counterparts. Using spherical polar coordinates related sub-integral kernels can efficiently be decomposed into azimuthal and isotropic parts. Both spectral and closed forms of the isotropic kernels are provided and their limits are investigated. Thirdly, numerical experiments are performed to test the consistency of the new integral transforms and to investigate properties of the sub-integral kernels. The new mathematical apparatus is valid for any harmonic potential field and may be exploited, e.g., when gravitational/magnetic second- and third-order tensor components become available in the future. The new integral formulas also extend the well-known Meissl diagram and enrich the theoretical apparatus of geodesy. 相似文献
90.
The Removal of Dissolved Metals by Hydroxysulphate Precipitates during Oxidation and Neutralization of Acid Mine Waters, Iberian Pyrite Belt 总被引:4,自引:0,他引:4
J. Sánchez España E. López Pamo E. Santofimia Pastor J. Reyes Andrés J. A. Martín Rubí 《Aquatic Geochemistry》2006,12(3):269-298
This study examines the removal of dissolved metals during the oxidation and neutralization of five acid mine drainage (AMD)
waters from La Zarza, Lomero, Esperanza, Corta Atalaya and Poderosa mines (Iberian Pyrite Belt, Huelva, Spain). These waters
were selected to cover the spectrum of pH (2.2–3.5) and chemical composition (e.g., 319–2,103 mg/L Fe; 2.85–33.3 g/L SO4=) of the IPB mine waters. The experiments were conducted in the laboratory to simulate the geochemical evolution previously
recognized in the field. This evolution includes two stages: (1) oxidation of dissolved Fe(II) followed by hydrolysis and
precipitation of Fe(III), and (2) progressive pH increase during mixing with fresh waters. Fe(III) precipitates at pH < 3.5
(stages 1 and 2) in the form of schwertmannite, whereas Al precipitates during stage 2 at pH 5.0 in the form of several hydroxysulphates
of variable composition (hydrobasaluminite, basaluminite, aluminite). During these stages, trace elements are totally or partially
sorbed and/or coprecipitated at different rates depending basically on pH, as well as on the activity of the SO4=
anion (which determines the speciation of metals). The general trend for the metals which are chiefly present as aqueous
free cations (Pb2+, Zn2+, Cu2+, Cd2+, Mn2+, Co2+, Ni2+) is a progressive sorption at increasing pH. On the other hand, As and V (mainly present as anionic species) are completely
scavenged during the oxidation stage at pH < 3.5. In waters with high activities (> 10−1) of the SO 4= ion, some elements like Al, Zn, Cd, Pb and U can also form anionic bisulphate complexes and be significantly sorbed at pH
< 5. The removal rates at pH 7.0 range from around 100% for As, V, Cu and U, and 60–80% for Pb, to less than 20% for Zn, Co,
Ni and Mn. These processes of metal removal represent a significant mechanism of natural attenuation in the IPB. 相似文献