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1.
The composition and temporal distribution of planktonic diatoms were studied in three small shallow karstic lakes – Modro Oko, Desne, and Kuti – throughout the seasons in 1994, 1995, 1997, and 1998. Physico-chemical parameters did not differ among the three lakes, except for NO3 concentrations. Altogether, 137 diatom taxa within 41 genera were found in all three lakes combined. The highest number of taxa belonged to the genera Surirella (13), Navicula (12), andCymbella (9). Most taxa were tychoplanktonic, with true panktonic taxa contributing only 14% of the total. Despite their physical-chemical similarity, the lakes showed differences in the structure and dynamics of their diatom communities. Blooms occurred at different times in each of the lakes, and community similarity (Jaccard index) among all three was low (17.6–29.1%). The highest mean values of surface diatom abundance in Modro Oko (2199 cells L−1), Desne (7900 cells L−1), and Kuti (20690 cells L−1) were not significantly different. Margalef's species richness index did not differ either among the lakes or seasonally. Only five diatom taxa in quantitative samples, and 22 taxa in net-samples, were common to all lakes. The most frequent diatoms were Cyclotella striata (56–93%), Fragilaria ulna (50–67%), and Asterionella formosa (27–83%). The most abundant taxa in Modro Oko, Desne, and Kuti were, respectively, Cymbella sp. 1 (402 cells L−1), Cyclotella striata (3000 cells L−1) and Asterionella formosa (20690 cells L−1). Eighteen taxa were recorded for the first time in Croatia: Amphora commutata, Caloneis amphisbaena var. subsalina, C. silicula var. peisonis, Campylodiscus echeneis, Coscinodiscus lacustris, Denticula elegans, Gyrosigma acuminatum var. lacustre, G. distortum var. parkeri, G. fasciola, Navicula menisculus var. menisculus, N. pusilla, N. helensis, Stauroneis parvula var. prominula, Staurosira construens f. subsalina, Stephanodiscus sp. 1, Surirella gracilis, S. ovalis, and S. striatula. The genus Stephanodiscus was recorded for the first time in Croatia. 相似文献
2.
The groundwater response of coastal aquifers to tidal forcing is described by Laplace's equation coupled with the nonlinear phreatic-free surface boundary condition. Here we describe fluctuations in the water table using two small parameters, extending previous work by proposing an ansatz to compute higher order, semi-analytical solutions. The new solutions are compared with known lower order solutions. The relative difference between the linear solution and higher order solutions can reach up to 30% of the linear solution for shallow beaches. The new solutions exhibit a reduction in the over height of the groundwater fluctuations compared with the lower order solutions. In addition, the super elevation of the water table, both near shore and as the aquifer tends landward, is examined with the inclusion of higher order terms. 相似文献
3.
Dubravka Relić Dragana Đorđević Aleksandar Popović 《Environmental Earth Sciences》2011,63(6):1303-1317
We used elemental carbon, nitrogen, hydrogen and sulfur as well as ratios of hydrogen and nitrogen with total organic carbon
for investigation of source and conditions of organic matter in alluvial Danube sediments. We also determined the pseudo total
concentrations of metals presented as a sum of extracted concentration after five sequential extraction steps. The pseudo
total metal concentrations were found to be (mg kg−1) for Mn, 666; Fe, 25,852; Mg, 16,193; K, 2,063; Ni, 32.4; Zn, 72.2; Pb, 15.0; Cu, 26.0 and for Cr, 15.9. Correlation analysis
and two multivariate analysis methods (principal component and cluster analysis) were helpful in determining the associations
between the pseudo total extracted fractions of metals and with elemental carbon, hydrogen, nitrogen, sulfur, total inorganic
and organic carbon. These correlations will help us to identify substrates of trace metals in different oxic/anoxic conditions.
The correlation results of the trace metals and Fe, K, Mg and Mn suggest their adsorption, mainly onto Fe and Mn (hydro)oxides
and K alumosilicates, whereas correlations of metals with sulfur indicate that they were precipitated as Fe-sulfides. 相似文献
4.
Vibrational temperatures in the atmospheres of nine M type giants of luminosity class III and subtypes M2-M8 located in the
Galactic plane have been determined from the γ band system of the TiO molecule. The relationship between T
exc and T
eff has been established in agreement with the chosen T
eff calibration scale. The deviation of T
exc with recspect to T
eff for our stars has been used as an indicator of the depth of the atmospheric layers in which the molecular bands are formed.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
5.
This paper presents a review of recent experimental and numerical studies which deal with the analysis of form-induced stress
in rough wall turbulent boundary layers. The aim of the paper is to assess the importance of this stress for various rough
wall geometries and flow conditions. Analysis of the significance of form-induced stress is first performed by comparing its
magnitude with the magnitude of Reynolds stress for each data set available in literature. Then, by selecting a special set
of data, we analyze the comparison between the gradients of both stresses. We point out that the comparison of stress gradients
gives a different perspective on the role of form-induced stress in rough wall boundary layers. 相似文献
6.
Dubravka Relić Aleksandar Popović Dragana Đorđević Josef Čáslavský 《Environmental Earth Sciences》2017,76(3):122
This study assessed the state of waters in Belgrade regarding pollution with musk compounds as the target contaminants. Eleven of these compounds were alicyclic, two were macrocyclic, and one was polycyclic. Solid-phase microextraction was used for the isolation of these compounds from waste, surface and underground waters and from processed water prepared for drinking, while comprehensive orthogonal two-dimensional gas chromatography with mass spectrometry was used as the final analytical method. In wastewater samples, galaxolide was detected in concentrations of 1.13 and 0.40 μg/L, while in the Sava River and underground water its concentrations were 0.09 and 0.038 μg/L. The lowest concentrations of the investigated musk compounds were detected in underground water samples, indicating that this is the cleanest water of all the analyzed sources with respect to musk compounds. Comparing the results of musk compound concentrations determined in surface river water samples and clean river water samples utilized for drinking, a lower concentration of these compounds was detected in the clean river water samples. The majority of musk compounds were found in waters utilized for drinking. Based on the concentration values, we conclude that the analyzed waters are moderately polluted with these compounds. 相似文献
7.
8.
The paper presents a simple approach to estimate the bottom shear stress in the swash zone by coupling the Non Linear Shallow Water Equations with the momentum integral equation for the bottom boundary layer. The approach allows not only the computation of the frictional dissipation term in the equations but also to have an insight into the flow structure in the water column during a swash event. The numerical results have been compared with a new set of experiments involving a single dam-break generated swash event. Three different grain sizes, ranging from coarse sand to gravel, have been tested in the laboratory. 相似文献
9.
Dušan Jovanović Miro Govedarica Filip Sabo Dubravka Sladić Aleksandar Ristić 《国际地球制图》2015,30(5):483-505
Main objective of this study was to establish a relationship between land cover and land surface temperature (LST) in urban and rural areas. The research was conducted using Landsat, WorldView-2 (WV-2) and Digital Mapping Camera. Normalised difference vegetation index and normalised difference built-up index were used for establishing the relation between built-up area, vegetation cover and LST for spatial resolution of 30 m. Impervious surface and vegetation area generated from Digital Mapping Camera from Intergraph and WV-2 were used to establish the relation between built-up area, vegetation cover and LST for spatial resolutions of 0.1, 0.5 and 30 m. Linear regression models were used to determine the relationship between LST and indicators. Main contribution of this research is to establish the use of combining remote sensing sensors with different spectral and spatial resolution for two typical settlements in Vojvodina. Correlation coefficients between LST and LST indicators ranged from 0.602 to 0.768. 相似文献
10.
Dubravka Kotnik-Karuza Michael Friedjung Patricia Whitelock 《Astrophysics and Space Science》2006,304(1-4):311-313
JHKL photometry of the symbiotic Mira RR Tel over 25 years shows variable fading in all bands, which can be explained by variable obscuration due to dust. The evolutionary track of the star is presented in a two-colour diagram together with the corresponding mean values for normal Miras with thick and thin dust shells and pulsation periods between 350 and 600 days. The observed colours for RR Tel are significantly shifted from the range shown by normal unreddened Miras. The distance of RR Tel is estimated from its K magnitude and the Mira period luminosity relation after correcting for reddening. The dust envelope is discussed with respect to a simple model involving two blackbodies. There appears to be rather little dust emission even at 3 μm, but considerable extinction. 相似文献