National Repository of Grey Literature 11 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
Hydrogen peroxide and the abiotic formation of chlorinated organic compounds in forest soil
Doležalová, Jana ; Forczek, Sándor Tamás (advisor) ; Pavlík, Milan (referee)
3 Abstrakt Peroxid vodíku je přirozenou součástí lesní půdy a vzniká především díky činnosti různých půdních organismů jako jsou houby rozkládající dřevo a mykorrhizní houby. Peroxid vodíku se v půdě účastní abiotické chlorace organických látek. Tato chlorace probíhá pravděpodobně pomocí Fentonové reakce: Fe2+ + H2O2 → Fe3+ + OH- + OH·. Vznikající hydroxylové radikály jsou schopny oxidovat chlorid na reaktivní HOCl a následně může proběhnout chlorace organických látek a vytváří se tak různé chlorované uhlovodíky. K měření H2O2 lze použít řady analytických optických, elektroanalytických či chromatografických metod. Cílem této práce byla optimalizace spektrofotometrické metody za použití xylenové oranže při stanovení H2O2 v lesní půdě. Tato metoda je spolehlivá, přístojově nenáročná, čas analýzy poměrně krátký. Metoda je vhodná k měření nízkých koncentrací hydroperoxidů ve vodě, ale pro půdní vzorky prozatím nebyla použita. Protože je matricí při této analýze půda, je vhodné užití metody standardního přídavku. Pro stanovení koncentrace z půdy byla přezkoušena také různá extrakční činidla, kdy se jako nejvhodnější ukázal aceton. Limit detekce peroxidu je 0,29 g H2O2/g půdy (n=8) a metoda je lineární až do hodnot 10 g H2O2/g půdy při čemž množství peroxidu v čerstvých jarních vzorcích půdy se pohybovalo od 2,5...
Enzymatic Studies of Organohalogen Formation By Model Compounds
Blažková, Ivona ; Tesařová, E. ; Forczek, Sándor
Research in recent years has demonstrated that halogenated organic compounds are formed in\nnature due to biotic and abiotic processes. One of the most known sources of these substances are\nfrom the reaction catalyzed by haloperoxidases which include chloroperoxidase enzyme (CPO)\nisolated from Caldariomyces fumago. CPO enzyme was incubated with chloride or bromide, in the\npresence of hydrogen peroxide and organic substrates. Experiments were conducted with three\nsubstrates (acetone, acetic acid, and glucose), and different concentrations of halides.\nMeasurement of the samples by gas chromatography with an ECD detector showed the influence\nof the substrate type and halide concentration on the formation of the organohalogen products.
Uptake and Distribution of Chlorphenols in Barley
Jíšová, Tereza ; Forczek, Sándor ; Tesařová, E.
Chlorinated phenols represent one of the most common groups of toxic industrial compounds.\nThey are resistant to biodegradation in the environment and persist for a long time. Food crops\nsuch as spring barley, are susceptible to contamination by various pesticides and organic waste,\nand these substances can then get into the plants. Uptake and distribution of 2-chlorophenol were\ninvestigated in axenic spring barley. After absorption of 14C-labelled 2-chlorophenol, the plants\nwere harvested and extracts were analyzed for 2-CP derived radioactivity. The uptake of 2-CP to\nroots and transport to leaves were confirmed. Radioactive balance was calculated for individual\nplants.
Natural Sources of Chlorinated Volatile Hydrocarbons in Spruce Forest Undergrowth
Štangelová, Pavla ; Wimmer, Zdeněk ; Tesařová, E. ; Forczek, Sándor
Chlorine as one of the most frequently occurring elements in nature, is involved in biogeochemical\ncycles. Several anthropogenic and even natural sources of volatile chlorinated hydrocarbons of\nemission is known, yet natural sources have not been explored enough. The aim of this study is to\ngather information of potential sources of chlorinated organic hydrocarbons in spruce forest\nundergrowth. Emissions of chlorinated volatile hydrocarbons of selected species of bryophytes,\nferns and fungi were measured by SMPE sampling technique and analyzed with GC-MS analysis.\nSodium chloride solution was used as a stressor to simulate increased environmental chloride load.\nTrichloromethane (chloroform) was found in most natural samples, dichloromethane,\ntetrachloroethene and tetrachloromethane were found occasionally. Increased chloride\nconcentration caused elevated emissions of trichloromethane and tetrachloromethane in some plant\nspecies.
Study of Factors Influencing the Development of "Water Bloom" in the Water Reservoir Seč
Forczek, Sándor ; Holík, Josef ; Rederer, L. ; Koza, V.
In this work, we monitored several parameters that influence the development of algal bloom on the\nwater reservoir Sec. Primarily climatic conditions belong to the monitored parameters that influence\nthe population dynamics of algae (air temperature and rainfall, incident light), temperature\nstratification of water, concentration of oxygen, concentrations of total phosphorus, phosphate,\nvarious forms of nitrogen and organic substances, turbidity and also diversity and frequency of\nphytoplankton and zooplankton species. Between 2012 and 2014 have not occurred massive algal\nblooms in the summer months, however the measured physical, chemical and biological data, can be\nused to assess the development of algal population. The population dynamic factors influencing algal\ngrowth must be understand to be able to predict formation and to attempt suppression of algal\nblooms.
Low Molecular Weight Volatile Organochlorine Compounds from Natural and Anthropogenically Influenced Ecosystems
Forczek, Sándor ; Holík, Josef ; Rederer, L. ; Ferenčík, M.
In the biogeochemical cycle of chlorine, chlorinated compounds participate in natural and\nanthropogenically influenced processes forming also compounds, which can be identical to\nchlorinated pollutants and determine by AOX (adsorbable organic halogens) method. Volatile\norganochlorines are in the center of interest due to their toxicity and possible role in degradation of\natmospheric ozone. Some volatile chlorinated hydrocarbons are both reactive and toxic, such as\nchloroform, which also has natural and anthropogenic sources and can be formed in abiotic and\nbiotic processes. In this study the occurrence of chloroform and AOX is determined in a natural\nclean environment at the Hamry water reservoir, Czech Republic. Furthermore, AOX and\nchloroform concentrations will be evaluated in correlation with meteorological and physicochemical\nconditions of water.

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