The goal of the study was to research the relationship between the source rocks and the sediment deposited in the Vransko Lake in the Ravni Kotari area and to study the sedimentation pattern in the ...lake. Sediment was classified as the sandy silt and the phase analysis showed the presence of the calcite, quartz, micas, and pyrite. It is possible that the anoxic conditions formed in the sediment due to the pyrite presence. Carbonate component predominates in the sediment composition. CaCO.sub.3 mass fractions in the range 72-94% with the mean values in the range 82-88% were determined. sup.40K mass activities were in the range 31-166 Bq/kg, sup.232Th in the range 3.1-18 Bq/kg, and sup.137Cs in the range 0.3-68 Bq/kg. Negative correlations between CaCO.sub.3 mass fractions and radionuclides mass activities were determined. Correlations between the radionuclides mass activities were positive. In the NW part of the lake sedimentation rates of 10.0, 4.1 and 5.0 mm/a were estimated for the 1954-1964, 1964-1986, and the 1986-2010 periods, respectively. At the SE part sedimentation rates for the respective periods were as follows: 8.0, 2.3 and 2.5 mm/a. Average sedimentation rates were 6.4 mm/a for the NW part of the lake and 4.2 mm/a for the SE part. Sedimentation rate in the Vransko Lake varies in time and showed a significant decrease after the 1964. The input of the carbonate and silicate material into the lake is also variable. Keywords Sedimentation rate * Vransko Lake * Radionuclide * sup.137Cs * sup.232Th * sup.40K * Gamma-spectrometry * Source rock
Ichthyological, physical, chemical and bacteriological examinations of Vransko Lake (Croatia) were conducted in 1989 (June, September and December) and 1990 (April). Special attention was given to ...the examination of phytoplankton structure as an indicator of water quality. In addition to collecting phytoplankton specimens, the temperature and transparency of water were measured at 5 different places. The phytoplankton specimens were taken at the depths of 0.5 m, 10 m, 20 m and 40 m. The water temperature was mostly under the influence of surrounding air temperature. The thermic stratification in summer and the manifestation of isotherm in the colder period of year were observed. The phytoplankton was composed of 60 planktonic algae which belonged to the following groups: Cyanophyceae, Euglenophyceae, Dinophyceae, Chrysophyceae and Chlorophyceae. While representatives of Bacillariophyceae outnumbered other groups, the species Ceratium hirundinella which belongs to the Dinophyceae dominated all phytoplankton specimens of Vransko Lake. Qualitative analysis of phytoplankton implied good water quality and quantitative analysis showed oligotrophic character of the lake. According to representation of particular phytoplankton species at the time of examination, the dominant phytoplankton group in the lake belonged to the type Cyclotella-Dinobryon-Ceratium.
U radu je analizirano ponašanje dnevnih razina podzemne vode mjerenih u tri duboka piezometra locirana u slivu Vranskog jezera na otoku Cresu. Obuhvaćeno je razdoblje od 10. rujna 1997. do 31. ...prosinca 2000., dakle ukupno 1209 dana. Ponašanje razina u sva tri piezometra bilo je gotovo identično, jer su se vrijednosti kvadrata koeficijenata linearne korelacije između parova piezometara kretale između R2=0,955 i R2=0,998. Izračunati su i dnevni dotoci, kao i gubitci iz jezera. Maksimalni srednji dnevni dotok u jezero u analiziranom razdoblju iznosio je Q=8,9 m3/s, dok je maksimalni srednji dnevni gubitak iz jezera iznosio Q=-1,9 m3/s. Analizirane su razlike između istovremeno mjerenih razina podzemne vode u svakom pojedinom piezometru i vodostaja jezera. Utvrđeno je da je na piezometru B1, udaljenom 335 m od obale jezera, razina podzemne vode samo 56 dana (4,6 % analiziranog vremena) bila viša ili jednaka vodostaju jezera. Na piezometru B2, udaljenom 540 m od obale jezera, razina podzemne vode bila je 262 dana (21,7 % analiziranog vremena) viša ili jednaka vodostaju jezera, dok je na najudaljenijem piezometru B3, izbušenom 790 m od obale jezera, razina podzemne vode bila viša ili jednaka vodostaju jezera 89,1 % analiziranog vremena. Ovakav odnos je neočekivan i teško ga je objasniti ili korigirati bez dodatnih mjerenja, a što je nužno s obzirom da postoji sumnja u realnost izmjerenih razina podzemnih voda. Činjenica da Vransko jezero na Cresu predstavlja u svijetu jedinstvenu vodnu masu formiranu na krškom otoku zahtijeva da se procesi koji se u i oko njega zbivaju pouzdano rasvijetle, što predstavlja osnovni cilj ovog rada.
Provider: - Institution: - Data provided by Europeana Collections- Na fotografiji iz leta 1957 so učenci 5. b razreda OŠ Vransko. Razrednik je bil Plavčak Mihael.Fotografijo je prispevala Polona ...Lipovšek.- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
U radu su izneseni rezultati malakološkog istraživanja najvećeg hrvatskog jezera - Vranskog jezera, te drugih vodenih staništa na području istoiomenog Parka prirode. Ukupno je zabilježena 21 vrsta ...slatkovodnih mekušaca (15 vrsta puževa i 6 vrsta školjkaša), od kojih je u samom jezeru pronađeno samo 10 vrsta, što je najvjerojatnije posljedica povišenog saliniteta. U lokvi Benča pronađena je populacija zaštićene i ugrožene vrste puža Anisus vorticulus.
Provider: - Institution: - Data provided by Europeana Collections- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain ...Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
Cilj istraživanja je, usporedbom 7 determinističkih metoda interpolacije, odabrati najprikladnije interpolatore za potrebe geomorfoloških istraživanja. Za izradu modela i usporedbu metoda ...interpolacije korišten je skup visinskih podataka prikupljenih aerofotogrametrijskom izmjerom i stereorestitucijskom obradom. Točnost metoda interpolacije ispitana je analizom 8 statističkih parametara koji su dobiveni metodama unakrsnog vrednovanja, podijeljenih uzoraka i ponovno uzorkovanje (jackknifing). Osim analize parametara, interpolacijske metode su uspoređene i vizualno, kroz grafički prikaz podataka (dvodimenzionalno i trodimenzionalno) na osnovi vjerodostojnih grafičkih prikaza skupa podataka. Ispitan je utjecaj eksponenta udaljenosti, broja susjeda, udaljenosti i sektora na izlazne rezultate. Utvrđeno je da je multikvadratna radijalna osnovna funkcija (MK-ROF) po svim parametrima najbolja deterministička metoda interpolacije.
In the late forties the freshwater Mediterranean Vransko lake was stocked with common carps (97,5% mirror ones of farm origin and 2,5% scaled ones of river origin). The 122 carps (52 females and 70 ...males) from that lake were collected for this research in 1979 and 1982. The 120 were scaled and only two lined, all being between 2+ and 11+. The condition coefficients (K) varied between 1,15 and 1,40 and the standard length - maximum height ratio was 3,01 ± 0,19. The correlation between standard and total lengths can be expressed by the following formula: SL = 8,274 + 0,845 TL (p, < 01) Length - mass relationship was determined to be: log W = -4,738 + 2,94 log L (p, < 01) All these parameters show that common carps in Vransko lake transformed and stabilized themselves into the wild form. Compared to other wild stocks and not any more to the cultured carps, they adapt well to the lake environment, their growth and condition being fair good. However, the question of whether they should have been introduced into this lake at all remains open.
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