Assessment of the pseudo total metal content in alluvial sediments from Danube River,Serbia     

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   

Size-differential feeding in Pinna nobilis L. (Mollusca: Bivalvia): Exploitation of detritus,phytoplankton and zooplankton     

John Davenport  Daria Ezgeta-Balić  Melita Peharda  Sanda Skejić  Živana Ninčević-Gladan  Slavica Matijević 《Estuarine, Coastal and Shelf Science》2011

The endangered fan shell Pinna nobilis is a large bivalve mollusc (<120 cm shell length) endemic to the Mediterranean that lives one-third buried in soft substrata, generally in shallow coastal waters. We hypothesised that P. nobilis of different sizes would ingest different food sources, because small fan shells will inhale material from closer to the substratum than do large fan shells. We studied stomach contents and faeces of 18 fan shells, 6 small (mean 23.0 cm length), 6 medium-sized (mean 41.5 cm length) and 6 large (mean 62.7 cm length) living in a small area of a low-energy coastal detritic bottom characterised by mud, sand and macroalgae at Mali Ston Bay, Croatia. We found that all P. nobilis ingested copious quantities of undetermined detritus (probably at least 95% of ingested material), phytoplankton, micro and mesozooplankton and pollen grains. Large P. nobilis stomach contents showed a preponderance of water column calanoid copepods, while small fan shells had higher numbers of bivalve larvae. All fan shells took in high numbers of harpacticoid copepods that are benthonic, feeding on microbial communities of detritus and benthic vegetation. There was also a significant selection of phytoplankton species, some apparently occurring between inhalation and ingestion. The stomach contents of small P. nobilis had a higher organic matter content than either medium-sized or large fan shells; this indicated that small fan shells ingested detritus of higher organic content than did larger P. nobilis. As the faeces of all P. nobilis had similar organic matter content, this also indicates higher assimilation efficiencies in small fan shells. The demonstration of differential dietary selectivity by different sized animals has implications for future trophic studies of this endangered species. This study also provides the first demonstration of predation on zooplankton by P. nobilis.  相似文献   

In situ Raman observation of the crystallization in NaNO3–Na2SO4–H2O solution droplets     

Kirsten Linnow  Michael Steiger  Christine Lemster  Hilde De Clercq  Maja Jovanović 《Environmental Earth Sciences》2013,69(5):1609-1620

Several double salts have been detected in building materials and most of these salts are incongruently soluble compounds. In contrast to single salts, however, no systematic investigations of the crystallization behavior and deleterious effects of incongruently soluble double salts exist. To assess the damage potential of these salts, a systematic investigation of their highly complex behavior is desirable. This paper deals with the crystallization behavior of various solids in the ternary mixed NaNO₃–Na₂SO₄ system including the formation of the double salt darapskite, Na₃NO₃SO₄·H₂O. The crystallization sequence during droplet evaporation experiments at room conditions was determined using Raman and polarization microscopy. The basic idea of this research is to use deviations of the crystallization sequence of a salt or a mixed salt solution from the equilibrium pathway as an indicator to detect the degree of supersaturation. The observed crystallization pathway includes the formation of the metastable phases Na₂SO₄(III), Na₂SO₄(V) and darapskite. The experimental observations are discussed on the basis of the NaNO₃–Na₂SO₄–H₂O phase diagram and the results provide evidence for crystal growth from highly supersaturated solutions in both systems. If the crystals growing under these conditions are confined, these supersaturations result in substantial crystallization pressures.  相似文献   

Cation exchange capacity of loess and overlying soil in the non-carbonate loess sections, North-Western Croatia     

Nenad Tomašić  Štefica Kampić  Iva Juranović Cindrić  Kristina Pikelj  Mavro Lučić  Danijela Mavrić  Tajana Vučetić 《Central European Journal of Geosciences》2013,5(4):457-464

The adsorption properties in terms of cation exchange capacity and their relation to the soil and sediment constituents (clay minerals, Fe-, Mn-, and Al-oxyhydroxides, organic matter) were investigated in loess, soil-loess transition zone, and soil at four loess-soil sections in North-Western Croatia. Cation exchange capacity of the bulk samples, the samples after oxalate extraction of Fe, Mn and Al, and after removal of organic matter, as well as of the separated clay fraction, was determined using copper ethylenediamine. Cation exchange capacity (pH～7) of the bulk samples ranges from 5 to 12 cmol _c /kg in soil, from 7 to 15 cmol _c /kg in the soil-loess transition zone, and from 12 to 20 cmol _c /kg in loess. Generally, CEC values increase with depth. Oxalate extraction of Fe, Mn, and Al, and removal of organic matter cause a CEC decrease of 3–38% and 8–55%, respectively, proving a considerable influence of these constituents to the bulk CEC values. In the separated clay fraction (<2 μm) CEC values are up to several times higher relative to those in the bulk samples. The measured CEC values of the bulk samples generally correspond to the clay mineral content identified. Also, a slight increase in muscovite/illite content with depth and the vermiculite occurrence in the loess horizon are concomitant with the CEC increase in deeper horizons, irrespective of the sample pretreatment.  相似文献   

Height transformation models from ellipsoidal into the normal orthometric height system for the territory of the City of Zagreb     

Martina Gucek  Tomislav Bašić 《Studia Geophysica et Geodaetica》2009,53(1):17-38

The paper presents the testing of the possibility of determining the heights of GPS points in the homogeneous field in the new Croatian Height Reference System (HVRS71) by using the method of height transformation. The testing was made in the area of Zagreb. As part of the field works, normal orthometric heights of 27 GPS points were determined according to the new height system, by transferring the benchmark heights using the geometric levelling method, thus obtaining GPS/levelling points of known ellipsoidal and normal orthometric heights. The GPS/levelling points served as the basis for determining the transformation models that enabled the computation of normal orthometric heights from ellipsoidal heights of any GPS point in the observed area. The empirical data used for modelling were reduced undulation dN values of GPS/levelling points. As part of the dN modelling with parametric functions, the approximation surfaces were obtained on the basis of three polynomials: FN310, FN312 and FN318. The transformation models were also tested using non-parametric Watson and Loess algorithms. The FN318 and Loess models yielded the best results.  相似文献   

Deep water ventilation traced by <Emphasis Type="Italic">Synechococcus</Emphasis> cyanobacteria     

Ivica Vilibić  Danijela Šantić 《Ocean Dynamics》2008,58(2):119-125

The paper describes a finding of photoautotroph cyanobacteria Synechococcus in deep Adriatic waters during the spring of 2006. The maximum abundance in early May was positioned at 800 m, being of order of the values referred for the surface waters in the Adriatic Sea. The deep abundance maximum has been associated to the fast ventilation of deep Adriatic waters, usually occurring during wintertime strong cooling events. Two processes were detected: (1) deep convection in the South Adriatic Pit (SAP) and (2) density current going downslope. The first process was responsible for bringing the cyanobacteria down to 600-m depth in the area of convection, and the second one triggered the downslope transport of the cyanobacteria to the SAP very bottom. The depletion rate of Synechoccocus cyanobacteria in an extremely hostile environment has been computed to equal about 1 month.  相似文献   

Numerical modeling and simulation of pile in liquefiable soil     

Zhao Cheng  Boris Jeremić 《Soil Dynamics and Earthquake Engineering》2009,29(11-12):1405-1416

  相似文献   

A parallel mesh-free contaminant transport model based on the Analytic Element and Streamline Methods     

Karl W. Bandilla  Alan J. RabideauIgor Janković 《Advances in water resources》2009

This paper introduces a new method for simulating large-scale subsurface contaminant transport that combines an Analytic Element Method (AEM) groundwater flow solution with a split-operator Streamline Method for modeling reactive transport. The key feature of the method is the manner in which the vertically integrated AEM flow solution is used to construct three-dimensional particle tracks that define the geometry of the Streamline Method. The inherently parallel nature of the algorithm supports the development of reactive transport models for spatial domains much larger than current grid-based methods. The applicability of the new approach is verified for cases with negligible transverse dispersion through comparisons to analytic solutions and existing numerical solutions, and parallel performance is demonstrated through a realistic test problem based on the regional-scale transport of agricultural contaminants from spatially distributed sources.  相似文献   

Azimuthal anisotropy of the Pg-wave velocity in hypocentral volumes of NW Croatia     

Marijan Herak  Davorka Herak  Josip Stipčević 《Acta Geophysica》2009,57(3):600-615

Based on a large set of arrival times of the Pg phase reported by local and regional stations, we estimate azimuthal anisotropy of the Pg-wave velocity in focal volumes of the upper crust in NW Croatia. The method is based on analyses of the azimuthal dependence of ratios of cumulative differences of arrival times and travel paths between foci of earthquake pairs, computed for rays propagating within narrow azimuthal windows. The results clearly indicate the presence of anisotropy of 3.3% with the direction of fast velocity (approximately NNE-SSW) coinciding with the direction of the maximum tectonic pressure as revealed by 23 available focal mechanisms and previous geological investigations. Although a large part of observed anisotropy can be explained assuming that focal volumes are pervaded by a system of vertical extensive-dilatancy anisotropy (EDA) cracks aligned under the influence of local tectonic stress field, there is indication that — to a smaller extent — some role was also played by alignment of structural features in the region.  相似文献   

Changes in Components of the Water Balance in the Croatian Lowlands     

K. Zaninović  M. Gajić-Čapka 《Theoretical and Applied Climatology》2000,65(1-2):111-117

Summary ?This paper deals with variations and trends in some components of the water balance: the soil water content; evaporation loss from the soil (from the surface and underlying layers); transpiration; ground water recharge and runoff. These components are calculated by means of the Palmer procedure. This analysis is based on data from Osijek, Croatia from this century (1900–1995). Besides the meteorological input parameters necessary for the water balance calculations, i.e. precipitation, temperature and relative humidity, the pedological characteristics of this area have also been taken into account. Fluctuations have been considered by means of the 11-year binomial filtered series and linear trends were tested by means of the Mann-Kendall rank test. For a closer look on the trends of water balance components, a progressive analysis of the time series was performed, too. The results show a significant increase in potential evapotranspiration and evapotranspiration and decrease in runoff and soil water content has occurred during the century. Received February 22, 1999/Revised August 3, 1999  相似文献