2025-12-16
16:40 |
Co lze vyčíst z dynamiky hladiny podzemní vody v rašeliništích?
Vlček, Lukáš ; Kocum, Jiří
Práce se zabývá dynamikou hladiny podzemní vody v rašeliništích a zdůrazňuje, že jediná úroveň měřené hladiny nedokáže postihnout složité hydrologické procesy v těchto ekosystémech. Vysvětluje rozdíly mezi reakcí akrotelmu a katotelmu, význam hloubky a perforace vrtů i roli podloží v pohybové dynamice vody. Ukazuje, že kombinace více vrtů různé hloubky umožňuje určit směry proudění, identifikovat vliv klimatu a podzemní vody a přesněji hodnotit stav a zranitelnost rašelinišť. Závěry podtrhují nutnost komplexního monitoringu pro správnou interpretaci hydrologického režimu.
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2025-12-16
16:40 |
Response of dissolved organic carbon to rainfall-runoff events in streams draining peatbogs
Matoušková, M. ; Fraindová, K. ; Bejčková, M. ; Kliment, Z. ; Vlach, V. ; Vlček, Lukáš
The presented study investigates the dynamics of DOC concentrations in headwater peatbog areas with respect to the extreme rainfall-runoff (R-R) events hydrometeorological catchment preconditions. The main data sources were automatic devices for monitoring of groundwater level, discharges and rainfalls installed in the Vydra River catchment and one automatic water sampler ISCO in sub-catchment of the Rokytka River basin in the Šumava National Park. Changes in groundwater level and discharges had the greatest influence on DOC concentrations. Higher mean and maximum DOC were measured during events after a longer period without an extreme R-R event. The greater lag time of maximum DOC after peak flow and the higher mean DOC during the event were primarily due to hydrometeorological preconditions of the catchment. The highest DOC was in autumn after previous summer period with low discharges and low groundwater level. DOC was also positively corelated with air and water temperatures.
Úplný záznam
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2025-12-16
16:40 |
Transpirace buku a smrku: propojení měření mízního toku a stabilních izotopů
Pátek, Karel ; Šípek, Václav ; Kocum, Jiří ; Vlček, Lukáš ; Bouda, Martin ; Tesař, Miroslav
Transpirace stromů, jako významná složka vodní bilance, byla zkoumána za pomoci dvou různých přístupů. Prvním bylo měření mízního toku, které umožnilo porovnat množství vody spotřebované buky a smrky. Druhým přístupem bylo sledování izotopového složení mízy ve stromech, které ukázalo, jestli stromy používaly vodu pocházející ze zimních nebo letních srážek. Získané poznatky o chování buků a smrků jsou důležité nejen pro popis současné vodní bilance, ale umožní také předpovědět očekávané důsledky klimatické změny spojené s nárůstem teplot nebo přeměnou druhového složení lesů.
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2025-12-16
16:40 |
Úplný záznam
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2025-12-16
16:40 |
Nový postup extrakce půdní vody pro analýzy stabilních izotopů
Kocum, Jiří ; Haidl, Jan ; Gebouský, Ondřej ; Falátková, Kristýna ; Šípek, Václav ; Šanda, M. ; Orlowski, N. ; Vlček, Lukáš
Zařízení pro extrakci půdní vody slouží k získávání vody z půdních vzorků za účelem jejího následného laboratorního analyzování, zejména stanovení izotopového složení. Výsledky těchto analýz lze využít například při určování původu vody, stanovení doby jejího zdržení v půdním profilu či sledování dynamiky půdní vody, což může najít uplatnění v environmentálním výzkumu i v praktických předpovědních modelech hospodaření s vodními zdroji.
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2025-12-16
16:40 |
Hydrologie malého povodí 2025
Hnilicová, Soňa ; Tesař, Miroslav
The book is a collection of scientific contributions to the Conference "Hydrology of small basins". The conference topics were: 1. Changes in the regime of water resources in small basins; 2. Complex monitoring a and water storage balance in small basins; 3. Hydrological extremes (flash floods, drought); 4. Effect of land use and land cover on water balance; 5. Hydrophobicity and transportation processes in soil; 6. Hydrological modelling und uncertainties; 7. Biogeochemical fluxes in a small watershed and eutrophication of surface waters; 8. Mountainous experimental small basins (deposited precipitation, snow regime, …); 9. New methods, techniques and instrumentation in hydrology and hydroecology.
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2025-05-11
00:00 |
Headwaters biogeochemistry focused on different rainfall-runoff conditions, and the role of waterlogged areas
Fraindová, K. ; Kliment, Z. ; Matoušková, M. ; Vlček, Lukáš ; Vlach, V.
River headwaters have a high environmental value. Unfortunately, the biogeochemical process in headwaters in context of different rainfall-runoff conditions and specific land cover have not been fully examined. This study focuses on changes in correlations of 16 biogeochemical parameters related to different types of rainfall-runoff events and land cover conditions for eight headwater catchments in Central Europe. Multiple methods as linear regression, Spearman rank correlation, Principal Components Analysis and C/Q hysteresis loops revealed main relationships. Presence of peatlands and waterlogged spruce forests had decisive influence on the biogeochemistry (mainly for COD(Mn), humins, Fe, P-PO4(3-) TP, and N-NO3(-)). The strongest positive correlation of organic matter (COD(Mn)) and Fe is represented in a catchment with the largest area of damaged forest (70 %), but with a smaller proportion of wetlands (8 %). High flow rates influence the release of greater amounts of organic matter and N-NO3(-).
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2025-01-12
00:00 |
Mixing characteristics of a magnetically driven Rushton turbine in an unbaffled stirred tank reactor
Idžakovičová, Kristýna ; Haidl, Jan ; Gebouský, Ondřej ; Isoz, M.
The standard and well-researched stirred vessel configuration comprises a tank equipped with one or more impellers positioned in the vessel’s axis and multiple wall-mounted baffles preventing the central vortex creation. However, particular industries, such as biotechnology, have an increased need for a sterile environment that often results in the usage of atypical stirred vessel configurations. An example of a commonly equipped atypical stirred vessel is an unbaffled stirred tank with an eccentric magnetically driven impeller. However, there is only a little knowledge about the mixing characteristics of such designs. In this work, we list experimental results for both the standard and atypical stirred vessel configurations. Furthermore, we present a CFD model of the atypical configuration. The model is used to calculate its mixing characteristics that are subsequently compared against our experimental results. It is shown that for the liquid height (H) to the vessel diameter (T) ratio H/T ≲ 1.2, the characteristics of both the standard and atypical designs coincide. For higher liquid heights (i) the characteristics of the atypical design decrease dramatically, and (ii) the characteristics estimates based on approaches developed for the standard configuration become unreliable.
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2024-05-12
00:02 |
Flow simulations approach for flocculation tanks
Idžakovičová, Kristýna ; Bílek, Vojtěch ; Haidl, Jan ; Isoz, M. ; Pivokonský, Martin
Flocculation in water treatment facilities plays a key role in the separation of colloidal inorganic and organic substances. Its optimization leads to a significant increase in its efficiency and savings of operational costs. However, it is currently based on trial-and-error experimental approaches. In this contribution, we focus on flow modeling in stirred flocculation tanks that would, after coupling with a calibrated model of particle aggregation, enable simulationbased flocculation optimization. Despite the abundance of literature on stirred tank modeling, there is no universal agreement on the methodology used to describe turbulence nor on the approach to the computational mesh creation. Consequently, there is no unified methodology for simulations and their validation. To address this, we present a best-practice methodology for economical, yet reliable flow simulations in the said device. This methodology includes the choice of the turbulence model, the approach to the design of a high quality mesh suitable for arbitrary geometries, and results evaluation. It is developed based on an extensive literature review, a multitude of flow simulations using several meshes of progressively higher quality and resolution, and various strategies to converge to steady-state flow conditions. The simulation quality indicators used here involve comparison with the experimental data on fluid velocity, stirrer power output, and flow rate through the impeller zone. Additionally, the resulting flow simulation models are compared using tracer transport simulations, hinting at their potential for coupling with particle aggregation models.
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2024-05-12
00:02 |
Improvement of an unbaffled stirred tank mixing characteristics using variable speed impeller
Gebouský, Ondřej ; Haidl, Jan ; Bodnár, J. ; Pivokonský, Martin
Unbaffled mixing tanks with magnetically driven impellers are increasingly used in biotechnological and pharmaceutical industries, combining the benefits of a closed, sterile environment with easy equipment cleanability. On the other hand, missing internals, such as baffles or cooling coils, have an adverse effect on the equipment mixing characteristics, namely the batch\nhomogenization time. In our previous research, we uncovered that the eccentricity and inclination of the impeller – both employed routinely to enhance the mixing characteristics of unbaffled vessels – are not fully effective in the suppression of central vortex formation resulting in the increase in the homogenization time. In this work, we propose a simple solution to counteract the central vortex formation – a periodical variation of impeller rotational speed. This approach destabilizes the central vortex, significantly reducing homogenization time while maintaining the benefits of the original unbaffled setup. This innovation can seamlessly integrate into existing industrial setups, promising efficiency gains for biotech and pharmaceutical production.
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