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Individual and joint effect of oleic acid imidazoline and CeCl3 on carbon steel corrosion in CO2-saturated brine solution
No full textIn production and transportation systems of the oil industry, brine solutions contain high concentrations of chloride and dissolved CO2, which is a very corrosive medium to which carbon steel is exposed. Therefore, finding new effective and environmentally friendly corrosion inhibitors is of great importance. The effect of CeCl3 (in concentrations from 5 mg dm−3 to 20 mg dm−3) and oleic acid imidazoline (IOA) (in concentrations from 5 mg dm−3 to 20 mg dm−3) separately and their mixtures (in concentrations from 5 mg dm−3 to 15 mg dm−3 of CeCl3 and from 5 mg dm−3 to 20 mg dm−3 of IOA) as corrosion inhibitors of AISI 1018 carbon steel corrosion in simulated brine solution saturated with CO2 at 60 °C were examined by means of weight-loss testing, electrochemical measurements (polarization resistance, linear polarization with Tafel extrapolation, electrochemical impedance spectroscopy) and surface analyses (scanning electron microscopy with energy-dispersive X-ray spectroscopy analyses, Raman spectroscopy and X-ray diffraction). All test methods showed a higher efficiency of compounds′ mixtures (from 62.77% to 97.94%) and a higher degree of corrosion protection compared to the action of individual compounds (efficiency from 3.43% to 94.61% for IOA and from 57.58% to 96.27% for CeCl3). Imidazoline, a common corrosion inhibitor in CO2-saturated systems, most likely forms a surface film with voids via its adsorption on steel surface, while cerium carbonate tends to fill these voids by creating a more compact film. In this way, a denser and thicker surface film is formed
Modeling and design aspects of shallow geothermal energy piles—a case study on large commercial building complex in Zagreb, Croatia
No full textWith ambitious targets set by the EU for the reduction of emissions from the energy sector by 2030, there is a need to design and develop more building projects using renewable energy sources. Even though in Europe, heating and cooling share from renewable resources is increasing, and in 2021, the total share in this sector in Croatia was at 38%, the share of heat production by heat pumps is rather low. One possibility to increase this share is to install energy piles when constructing a building, which is becoming an increasingly common practice. This case study focuses on such a system designed for a large, non-residential building in Zagreb, Croatia. The complex was designed as 13 separate dilatations, with central heating and cooling of all facilities, covered by 260 energy piles (130 pairs in serial connection), with a length of the polyethylene pipe of 20 m in a double loop inserted within the pile. The thermo-technical system was designed as a bivalent parallel system, with natural gas covering peak heating loads and a dry cooler covering cooling peak loads when the loads cannot be covered only by ground-source heat pumps. In the parallel bivalent system, the geothermal source will work with a much higher number of working hours at full load than is the case for geothermal systems that are dimensioned to peak consumption. Therefore, the thermal response test was conducted on two energy piles, connected in series, to obtain thermogeological parameters and determine the heat extraction and rejection rates. The established steady-state heat rate defines the long-term ability to extract heat energy during constant thermal load, with the inlet water temperature from the pile completely stabilized, i.e., no significant further sub-cooling is achieved in the function of the geothermal field operation time. Considering the heating and cooling loads of the building, modeling of the system was performed in such a manner that it utilized renewable energy as much as possible by finding a bivalent point where the geothermal system works efficiently. It was concluded that the optimal use of the geothermal field covers total heating needs and 70% for cooling, with dry coolers covering the remaining 30%. Additionally, based on the measured thermogeological parameters, simulations of the thermal response test were conducted to determine heat extraction and rejection rates for energy piles with various geometrical parameters of the heat exchanger pipe and fluid flow variations
The effects of using the pipe bomb with ANFO explosive as an improvised explosive device
No full textImprovizirane eksplozivne naprave predstavljaju veliku opasnost za sigurnost civilnog stanovništva i pripadnike vojnih formacija. Jednostavnost izrade, dostupnost komponenti za izradu razlog su njihove raširene upotrebe kod terorističkih i kriminalnih napada diljem svijeta. U radu je dan opis različitih vrsta improviziranih eksplozivnih naprava te povijesni pregled terorističkih napada u kojima su korišteni eksplozivi na osnovi amonijevog nitrata. Osim toga, predstavljeni su rezultati ispitivanja učinaka primjene cijevnih bombi izrađenih od različitih metala s eksplozivnim punjenjem od ANFO eksploziva. Djelovanje zračnog udarnog vala izračunato je pomoću EXPLO 5 računalnog programa. Prilikom ispitivanja utvrđeno je da debljina stijenki i masa metala utječu na izmjerenu brzinu detonacije ANFO eksploziva i učinkovitost cijevnih bombi.Improvised explosive devices (IEDs) pose a major threat to the safety of the civilian population and members of military formations. The ease of manufacture and the availability of components for manufacture are the reason for the widespread use of IEDs in terrorist and criminal attacks worldwide. The paper presents the different types of IEDs and a worldwide attack with IEDs in which ammonium nitrate (AN) based explosives were used. It also presents the results of tests of the effectiveness of pipe bombs made of various metals with a charge of ANFO explosive. EXPLO 5 program is used to calculate overpressure. During the tests, it was found that the thickness of the walls and the mass of the pipe influence the measured detonation velocity of ANFO explosives and the effectiveness of pipe bombs
Influence of mining layout on efficiency of NRE drill rig
No full textThe selection of an appropriate mining method, along with the corresponding machinery, is a crucial and highly strategic decision in the field of mining engineering. This decision directly influences the efficiency, safety, and economic viability of a mining operation. An optimal combination of mining techniques and equipment is essential to ensure the effective exploitation of the ore deposit while minimizing costs and maximizing productivity. This paper briefly overviews existing mechanized mining machines for narrow reef mining. The NRE fleet is presented in more detail, together with the results of trial tests conducted using the NRE Drill Rig in narrow reef platinum mines situated in the Great Dyke of Zimbabwe and the Bushveld Igneous Complex in South Africa. The trials were carried out using two distinct mining layouts: the bord and pillar layout and the breast mining layout. The test results clearly demonstrated that the Drill Rig is more effective in breast mining layout compared to the bord and pillar layout in narrow reef mining. The breast mining layout showed superior performance in terms of the number of drilled boreholes and overall efficiency despite the lower availability and utilization of the Drill Rig
Metodologija modeliranja podložnosti na klizanje malih i plitkih klizišta u Panonskom bazenu u krupnom mjerilu primjenom statističkih metoda : doktorski rad
No full textApproximately 30% of Croatian territory is prone to landslides, which pose a significant threat to structure, infrastructure and population. A successful disaster risk reduction management implies mitigation of landslide impact by the development of landslide hazard zonation maps, which can express in probabilistic terms, where, when and how large landslides will occur. Susceptibility is key information for an effective hazard evaluation and quantifies the spatial probability of a landslide occurrence. In the framework of this doctoral dissertation, a methodology for assessing landslide susceptibility at a large scale is established. The methodology is developed for small and shallow landslides, which are widespread in the Pannonian Basin, and it is based on the use of statistically-based methods specifically applied for large scale landslide susceptibility modelling. The proposed methodology was developed on the following research framework: (i) analysing data quality; (ii) testing classification methods for continuous landslide conditioning factors; (iii) exploring sampling strategies for landslide data (i.e. stable and unstable areas); (iv) verifying the use of diversified statistically-based methods for susceptibility assessment; and (v) verifying the use of diversified evaluation metrics. The research framework was applied in three study areas characteristic and representative of the geo-environmental setting in the Pannonian Basin, i.e. part of Hrvatsko Zagorje (20 km2), part of Podsljeme area (21 km2) and whole Podsljeme area (130 km2). The results of data quality analysis showed that preparation of a representative landslide inventory and spatially accurate landslide conditioning factors are a key step, and it can be accomplished by utilizing mainly remote sensing data, i.e. high-density LiDAR (Light Detection and Ranging) point cloud and high-resolution digital orthophoto imagery. Machine learning methods, such as neural networks and random forests resulted in the highest performance metrics while being more sensitive to certain modelling parametrization, unlike logistic regression and information value methods, which demonstrated to be more stable, still being up to par with performance metrics. Furthermore, sampling stable areas as randomly generated points has to be preferred, whereas classifying continuous landslide conditioning factors shows optimal performance metrics when resulting in >10 classes, or ideally as much as possible (i.e. usage without classification). Practical application of preliminary large scale landslide susceptibility models over larger areas, was successfully tested in the Podsljeme area (130 km2) to increase cost-effectiveness of large-area susceptibility mapping. This required the selection of a smaller but geologically and geomorphologically representative area (Podsljeme area (21 km2)), a crucial step for a reliable susceptibility assessment. The doctoral research yielded new insights into the qualitative assessment of landslide susceptibility models, which proved to be highly significant alongside commonly used quantitative assessments. The methodological framework, based on relevant research findings, defines crucial modelling steps to obtain large scale landslide susceptibility maps. Alongside necessary input data, i.e. landslide inventories and landslide conditioning factors, these maps are applicable for landslide risk reduction and mitigation.Modeliranje podložnosti na klizanje provodi se u okviru procjene podložnosti, a rezultat su karte zoniranja podložnosti koje imaju višestruku primjenu u upravljanju opasnostima od klizišta. Unatoč brojnim znanstvenim radovima tijekom prethodnih 40 godina o procjeni i kartama podložnosti na klizanje, ne postoji definirana metodologija za modeliranje podložnosti malih i plitkih klizišta u krupnom mjerilu. Glavna svrha doktorskog istraživanja bila je razviti metodologiju za procjenu podložnosti na klizanje u krupnom mjerilu primjenom statističkih metoda i testirati ju na pilot područjima u Panonskom bazenu. Metodologija je razvijena koristeći podatke daljinskih istraživanja visoke kvalitete dobivene LiDAR (Light Detection and Ranging) tehnologijom. Prva skupina istraživačkih tema obuhvaća istraživanja prostorne točnosti ulaznih podataka za modeliranje podložnosti na klizanje koje su odgovarajuće za krupno mjerilo. U drugoj skupini su istraživanja povezana sa sustavnim, detaljnim i istovremenim testiranjem parametara modeliranja podložnosti. Treća skupina istraživačkih tema usmjerena je na istraživanje mogućnosti za razvoj jedinstvenog pristupa procjeni podložnosti na klizanje u krupnom mjerilu, kao i za razvoj preporuka koje nedostaju u literaturi
Mineralogical and geochemical characteristics of the host-rocks from Ag-polymetallic Rupice deposit, Bosnia and Herzegovina : master's thesis
No full textThe Triassic succession of the Rupice deposit comprises deep-sea siliciclastic-carbonate, volcanoclastic, and chert units. Five cores were selected for petrographic and geochemical analysis to determine the characteristics and deposition conditions of lithotypes, as well as the genesis of the deposit. Five facies and eleven lithotypes were differentiated: 1. Siliciclastic-carbonate facies (lithotypes dolomitic marl, silicified marl, dolomitic silt-stone, silicified siltstone, dolomicrite, LD dolomite, and dolomite breccia), 2. Spilite facies (lithotypes tuff, amygdaloidal basalt, spilite breccia), 3. Chert facies (lithotype radiolarite), 4. Ore-bearing facies (sulphide mineralization and mineralized dolomitic breccia), and 5. Limestone facies (lithotype mudstone). The deep-sea siliciclastic-carbonate facies were deposited in the Anisian during the opening of the Dinaric Tethys, fol-lowed by advanced rifting in the Anisian-Ladinian, which was accompanied by the deposition of radiolarite and followed by a magmatic-hydrothermal phase. In the Eocene-Oligocene, the basin closure occurred through reverse faulting, resulting in overthrusts and a duplex structure of the deposit
Determination of the Western Herzegovina and Southern Dalmatia karst spring water origin based on natural and artifical tracers : doctoral thesis
No full textKompleksni hidrogeološki slijevni sustav južne Dalmacije i zapadne Hercegovine površine preko 2300 km2, predmet je dugogodišnjih hidrogeoloških istraživanja, koja su detaljno analizirana za potrebe izrade ovog doktorskog rada. No, ranija istraživanja nisu uključivala istodobno praćenje većeg broja izvora u obje države kako bi se odredilo podrijetlo izvorskih voda ovoga područja. U dosadašnjim istraživanjima sljevovi pojedinih izvora su se preklapali u velikoj mjeri, što je ukazalo na potrebu za delineacijom, što ujedno predstavlja temelj za mnogobrojne hidrogeološke analize poput određivanja zaliha podzemnih voda, izrade karata ranjivosti ili izrade karata poplavnih hazarda, izračuna vodne bilance. Isto tako, po prvi su put obavljena i istraživanja stabilnih izotopa kisika 18 (δ18O), deuterija (δ2H) i sumpora 34 (δ34S), kako bi se odredila starost vode te podrijetlo povišenih koncentracija sulfatnih iona. Hidrogeološka istraživanja trajala su od rujna 2013. godine do rujna 2020. godine i uključivala su primjenu više različitih metoda, što je rezultiralo novim saznanjima o ovom krškom podzemnom sustavu i njegovoj interakciji s oborinama, površinskom i morskom vodom. Na terenu su automatskim mjeračima mjereni temperatura, elektrolitička vodljivost i razine podzemne vode, mjereni su protoci na nekoliko lokacija te su in situ mjereni fizikalno-kemijski pokazatelji. Uzorci podzemne i površinske vode prikupljani su na 31 lokaciji za laboratorijsko određivanje ionskog sastava. Rađena je i analiza stabilnih izotopa kisika 18 (δ18O), deuterija (δ2H) i sumpora 34 (δ34S) u različitim hidrološkim uvjetima, kako bi se protumačile i sezonske promjene. Na terenu je provedeno i simultano trasiranje dvama traserima te su prikupljani podataci o oborinama i protocima te mikrobiološkim pokazateljima. Rezultati su ukazali kako je najveći dio područja napajanja u zapadnoj Hercegovini, manji dio u neposrednom zaleđu, a konačna zona istjecanja u južnoj Dalmaciji. Ukazano je i kako voda većinski prolazi kroz karbonatne naslage, a prema rezultatima analize stabilnih izotopa δ34S djelomično i kroz evaporitne stijene permotrijaske starosti. Rezultati ukazuju i kako se vodonosnik obnavlja s oborinskom vodom te se radi o izrazito mladoj vodi, na brzo dreniranje zbog izrazite okršenosti terena, i na moguće antropogene izvore u vodi (gnojiva, otpadne vode). Delineirano je šest podsljevova ili utjecajnih površina, što je i prikladniji opis, jer se podzemne vode u nekim hidrološkim uvjetima dokazano kreću preko naznačenih granica.The complex hydrogeological transboundary catchment of Southern Dalmatia and Western Herzegovina, located in two neighbouring countries, Croatia and Bosnia and Herzegovina, covers an area of 2300 km2. In addition to numerous previous hydrogeological studies, a new research was carried out from September 2013 to September 2020 for the purpose of this thesis. During this period monthly sampling of five spring and surface water locations in Western Herzegovina, 20 locations of spring and surface water in Southern Dalmatia and six locations of spring and surface water at Baćina lakes was performed. Additional research included hydrogeological mapping, a simultaneous tracing experiment (on September 30th and October 2nd, 2014), and stable sulphur δ34S analyses from SO4- ions in water samples, taken during hydrological maximum (April) and minimum (October) of 2019 at ten locations. The study area is composed of sedimentary rocks of Permian, Triassic, Jurassic, Cretaceous, Palaeogene, Neogene and Quaternary ages. The oldest, Upper Permian rocks have been tectonically uplifted to the surface through diapirism and reverse faulting N of the studied catchment area and consist of evaporitic rocks with some carbonate and clastic rocks (sandstones and marls) interbeds. Hydrogeologically they could potentially represent a barrier to groundwater flows, but since they occur outside of the study area they do not influence hydrogeological relationships. However, a very locally restricted diapir in the northern part of the study area as well as extraordinary high sulphur concentrations at some locations indicate probable diapiric uplifts also in the studied area. Triassic deposits, in large part composed of dolomites, form partial barriers to water circulation within the study area. Jurassic rocks, dolomites and limestones. Cretaceous deposits, mostly composed of bedded to massive limestones with rare dolomites prevail in this area. Palaeogene and Neogene deposits consist of a wide range of lithologies, but clastic rocks (mostly sandstones and marls) predominate, especially Eocene flysch deposits which have a diverse impact on groundwater movement. Quaternary deposits cover numerous karst poljes, as well as areas along streams and rivers. The most permeable rocks in the study area are Mesozoic limestones and dolomites, while the least permeable rocks belong to flysch and Quaternary deposits. A complex underground conduit system and extreme karst forms heterogeneity are typical for the study area, characterised by very variable relief from mountains and hilly parts, river valleys and karst poljes to the Adriatic coast. The study area can be divided into five or six hypsometric levels. The first or the lowest level is the discharge zone almost at the sea level. iii This zone extends from Gradac and the nearby coastal karst spring Mandina Mlinica, across the Baćina Lakes and the Klokun 1 spring to the Neretva River valley and its marginal karst springs Prud, Modro oko, Čeveljuša, and several smaller springs. Vrgoračko polje is part of the second level (25 m a.s.l.) and Rastok polje of the third level (70 m a.s.l.). The fourth level includes springs in the Trebižat–Mlade–Tihaljina River valley in Bosnia and Herzegovina (120–180 m a.s.l.), while the fifth level, the highest one, stretches across the Imotski–Bekija polje (260 m a.s.l.). In the nortwesteern part, the fifth level comprises the wider area of the Posuško polje (570–620 m a.s.l.), but the highest part of the area around the Rakitno polje (900 m a.s.l.) could be separated as the sixth level. The study area is abundant in high-quality spring water, of which only a small amount is used for public water supply. Over a hundred temporary and permanent karst springs occur in the area with annual discharge of the largest springs (Klokun 1, Butina, Modro oko, Borak, Vrelo Tihaljine, Prud, Opačac, Klokun 2) ranging from 1.5 to over 10 m3/s. Rivers Ričina, Suvaja, Sija, Vrljika, Tihaljina, Sita, Mlade and Trebižat actually represent the same river characterized by repeated springing, flowing on the surface, sinking, and underground stream sections, along its 106 km long course from the highest spring to its confluence with the Neretva River. Most of the surface waters in the area flow towards the Neretva River, but part of groundwaters flow southwards. The recharge zone of this large catchment area is predominantly in Bosnia and Herzegovina, whereas the final discharge zone is along the Croatian coast and Neretva River valley. During the study for this thesis an integrated hydrogeological map of the whole catchment area has been made by combining four basic geological maps and attributing specific hydrogeological characteristics to all geological units. Furthermore, further delineation of the catchment boundaries and the catchment area was performed, which is an extremely complex task in the karst areas. In order to define external and internal boundaries of such a large and complex catchment area different methods were used, including detailed study of all available geological and hydrogeological data, hydrogeochemical properties of individual springs, hydrological data, and tracing tests data combined with water balance calculated in previous reports. Out of a large number of reviewed studies and published papers on the study area very few of them included the simultaneous monitoring of a large number of springs in both countries. In addition, a simultaneous tracer test was carried out for the purpose of this thesis. iv Since some of the previously determined groundwater connections confirmed by tracing experiments were cutting previously defined groundwater boundaries within some of the subcatchments, it became evident that a new definition of some subcatchments should be introduced. Up to now there were no research of stable isotopes of oxygen 18 (δ18O), deuterium (δ2H) and sulphur 34 (δ34S) within the study area. Those natural stable isotopes are especially important for the determination of the water age and origin, especially in areas where artificial tracing is not feasible at the scale of the regional catchments. Moreover, as evaporite diapirs crop out in the vicinity of the study area and increased levels of sulphur were determined at some studied locations, it was assumed that some diapirs exist in the shallow underground of the research area in contact with groundwater paths, enriching Southern Dalmatia and Western Herzegovina groundwater with sulphate ions. Hence, for the first time in the study area, stable δ34S isotopes from sulphate ions in water samples were analysed to determine their origin. Therefore, the conducted hydrogeological investigations of the studied large catchment area were carried out using several methods to fulfil all the objectives of this thesis. The methods used included: 1) measurements of various water parameters, such as temperature, electrolytic conductivity, and water level measurements with automatic loggers, 2) in situ measurements of physico-chemical parameters, 3) water sampling and laboratory analyses for the determination of the ion composition, 4) analyses of δ18O, δ2H and δ34S stable isotopes, 5) flow measurements, 6) simultaneous tracing with artificial tracers, and 7) collection of available data on precipitation, discharge and microbiological parameters. Delineation of a large and complex karst catchment into six subcatchments from which surface and groundwater flow in different directions was the main result of this thesis. Subcatchments are defined according to their specific geological setting and hydrogeological relations, but their boundaries should not be considered as strict water divides because groundwater or surface water may intersect them during different hydrological conditions. Yet, they are fundamental for water balance calculations and estimating influence on even distant karst springs. Furthermore, new term redefining subcatchments as influential areas was introduced. The proposed term can be used for the description of comparable large karst catchments characterised by interaction between subcatchments. In such subcatchments groundwater fluctuates depending on the water table levels affected by changes in precipitation. Given the hydrogeological conditions during late winter and spring, when the snow melts and v precipitation significantly increases, groundwater often discharges across the defined boundaries. Therefore, the term subcatchment in this case, as in most of the Dinaric karst terrains, can only be used tentatively for easier understanding of the topic, while the term influential area could be far more appropriate. Results of stable δ34S isotopes composition from the measured sulphate ions were compared with the Permian evaporites δ34S isotope curves from the literature, which supports the possible sulphate ions origin from permian evaporites in Western Herzegovian and Southern Dalmatian groundwaters. Since the main recharge area of the studied large system is located in Western Herzegovina and the final discharge zone in Southern Dalmatia, the groundwater mostly passes through karstified carbonate rocks prevailing in the entire area, but is probably partly influenced by underground deposits of evaporite rocks that were probably uplifted close to the surface in the form of diapirs. Results of stable isotops analyses of sulphur from the sulphate ion in different hydrological conditions indicate a rapid reaction of the system to precipitation and mixing of dissolved sulphate from evaporites (mostly gypsum) with rainwater and possibly polluted water (sewage water). The presented comprehensive hydrogeological study has shown that the studied system has a zone of underground and surface runoff (sometimes intertwined) between the the Neretva River valley and hydrogeological barrier of flysch deposits along the Adriatic coast. Furthermore, research indicated that most of the studied major springs recharge from the same aquifer in their hinterland. Higher concentrations of sulphate ions in several springs of the Southern Dalmatia also indicate recharging from more distant areas – mainly W and N of Trebižat–Mlade–Tihaljina River, where evaporite rocks are cropping out and where the domination of sulphate ions in water was documented. Seawater impact was recorded in some coastal springs and surface waters, indicating fresh–seawater interaction. Such springs are located closer to the flysch barrier edge, in contact with permeable carbonates. Further to the east, the effect of underground penetration of the seawater decreases. In addition, multivariate mathematical cluster analysis of hydrogeochemical data shows two main clusters within the system, lithogeochemical cluster and marine cluster, while multivariate mathematical factor analysis separated three factors – seawater influence factor, carbonates and evaporates dissolution factor, and biological/chemical reactions factor. Determined three main hydrochemical facies within the investigated area (calcium–hydrogen carbonate facies, calcium–sulphate/hydrogen carbonate facies, and sodium–chloride facies) reflect the chemical response of lithology and groundwater flow pattern. vi Physico-chemical parameters of spring waters indicate shorter water retention time and domination of conduit flow, whereas recession curve analysis indicates rapid drainage of the aquifer due to immense karstification. Time-series data (cross-correlation analysis) indicates a rapid response to precipitation. All aforementioned analyses provided insight into the main aquifer characteristics and represented a basis for the interpretation of δ34S stable isotope data. Obtained results could improve the quality of the establishment of sanitary protection zones, as the new tracing experiment proved that the groundwater has much higher apparent velocity than considered previously, as well as better management of the, studied and similar transboundary catchments, which can often be challenging due to differences in development and policies between different countries. Thesis could be of great importance for the future management of this transboundary catchment because ensuring high-quality groundwater is crucial for sustainable development and protecting the ecosystem integrity of each country. In conclusion, the local and regionally important scientific contribution of the Ph.D. Thesis is manifested in: (1) Detailed determination of Southern Dalmatia and Western Herzegovina transboundary catchment area hydrogeological properties; (2) Newly proposed delineation of the studied large and complex karst catchment; (3) Establishing a new classification of subcatchments as influential areas applicable to other complex karst terrains; (4) Introducing sulphur δ34S stable isotope analysis as an important research methodology fa or complex karst catchment area of the Outer Dinarides
Hidrogeološka karta slijevnog područja južne Dalmacije i zapadne Hercegovine : prilog 5.
No full textDinamika nitrata u nesaturiranoj i saturiranoj zoni u priljevnom području crpilišta Velika Gorica : doktorski rad
No full textThe Zagreb aquifer system hosts strategic groundwater reserves of the Republic of Croatia and supplies drinking water to one million inhabitants of the capital city and Zagreb County. Nitrate ions (NO3 ‒) are one of the most common contaminants in the groundwater of the Zagreb aquifer system and elevated nitrate concentrations have been confirmed through previous research. Previous research conducted in the Zagreb area did not investigate the nitrogen (N) dynamics in the soil and unsaturated zone, the processes affecting NO3 ‒ infiltration into the aquifer, nor did it quantify the proportional contributions from different sources of N. Therefore, field and laboratory research, monthly sampling and analyses of groundwater and surface water, precipitation and soil water, as well as analyses of soil and various local N sources were conducted in the catchment area of the Velika Gorica well field, located on the right bank of the Sava River, in the southern part of the Zagreb aquifer system. The main goal was to define the sources and dynamics of NO3 ‒ in the unsaturated and saturated zone within the area of the Eutric Cambisols on the Holocene deposits, one of the most common soils developed in the area of the Zagreb aquifer system. A multi-method approach was used, integrating physicochemical, hydrogeochemical and isotopic data (water and nitrate stable isotopes) together with analyses of molar ratios, statistical techniques and mixing models. As a starting point, research demonstrates the approach to estimate the ambient background value (ABV) of nitrate in order to assess the presence of groundwater contamination. The ABV of nitrate determined for the catchment area of the Velika Gorica well field ranged from 7.1 to 7.5 mg/L. Furthermore, a new water sample preparation method for stable isotopic analysis of nitrogen and oxygen in dissolved NO3 ‒ was implemented. The combination of a nitrous oxide isotopic analyzer and the new sample preparation method provides reliable measurements of δ15NNO3 and δ18ONO3, with optimal stability achieved under specific conditions. Soil moisture content, pH, organic carbon availability and soil texture are important controlling factors influencing the dynamics of N species within the soil. In the deepest soil horizon within the coarse-grained Eutric Cambisols, N is present mostly as nitrites (NO2 ‒) and nitrates (NO3 ‒) due to soil ammonium (NH4 +) nitrification and leaching from the upper soil horizons during intense rainfall. Under such aerobic conditions, which promote stability and the potential for transport, N migrates to deeper parts of unsaturated zone in the form of NO2 ‒ and NO3 ‒. The isotopic composition of water and two-component mixing model showed that groundwater is predominantly recharged by the Sava River but its contribution varied spatially. The results also show the existence of a different source of recharge in the southern part of the aquifer system. Nitrate in the groundwater predominantly originates from organic sources, with nitrification as the main biogeochemical process, while denitrification was identified at sampling sites with specific anaerobic conditions. However, the Bayesian mixing model showed that contribution from mineral fertilizer exists and confirmed its significance as the source of NO3 ‒ and possible cause of elevated NO3 ‒ concentrations. Hydrogeochemical data, molar ratios and correlation analyses suggested that most part of nitrate concentrations were associated with the multiple contamination inputs, but at the same time did not clearly recognize the influence of mineral fertilizer. Therefore, the findings of this research highlighted the importance of employing a multi-method approach if NO3 ‒ originates from multiple sources in order to obtain reliable and comprehensive understanding of NO3 ‒ dynamics.Zagrebački vodonosni sustav sadrži strateške zalihe podzemne vode Republike Hrvatske, te je iznimno važan izvor pitke vode za oko milijun stanovnika. Ima visoku do vrlo visoku prirodnu ranjivost, što u urbanim područjima i područjima s intenzivnijim industrijskim i poljoprivrednim aktivnostima dovodi do povišenih koncentracija onečišćivala u podzemnoj vodi. Nitrati (NO3 ‒) su prepoznati kao jedni od najčešćih skupina onečišćivala podzemne vode zagrebačkog vodonosnog sustava, a povišene koncentracije nitrata u podzemnoj vodi potvrđene su kroz ranija istraživanja. Glavni antropogeni izvori nitrata povezani su s procjeđivanjem iz propusnih septičkih jama i kanalizacijske mreže, organskim stajskim gnojivom i intenzivnom uporabom anorganskih mineralnih gnojiva, dok značajni prirodni izvori uključuju atmosfersko taloženje dušika (N) i razgradnju organskog dušika iz tla. Za utvrđivanje postojanja onečišćenja podzemne vode, važno je razlikovati prirodne i antropogene utjecaje na kakvoću podzemne vode. Kako bi razlikovali prirodne i antropogeno uvjetovane koncentracije neke tvari u vodi, osmišljen je koncept ambijentalne pozadinske vrijednosti (engl. ambient background value, ABV), koji opisuje nemjerljivo poremećenu i ne više netaknutu pozadinsku koncentraciju tvari u podzemnoj vodi. Pozadinske koncentracije tvari, određene na razini regionalnih vodonosnih sustava, mogu se značajno razlikovati od pozadinskih koncentracija istih tvari određenih u homogenim područjima unutar vodonosnih sustava. Za identifikaciju izvora, te procesa koji utječu na transformaciju i dinamiku NO3 ‒ nužno je koristiti stabilne izotope dušika i kisika iz otopljenog nitrata (δ15NNO3 i δ18ONO3). Analiza δ15NNO3 i δ18ONO3 omogućena je razvojem različitih laboratorijskih metoda za pripremu uzoraka. Postojeće metode koje se trenutno provode u većini svjetskih laboratorija, poput bakterijske denitrifikacijske metode ili metode redukcije kadmija (azid metoda), uključuju više koraka pretvorbe ili upotrebu toksičnih kemikalija. Godine 2019., razvijena je titanij(III) redukcijska metoda za određivanje izotopnog sastava nitrata koja predstavlja metodu kemijske pretvorbe u jednom koraku primjenom reagensa Ti(III) klorid otopine koji reducira NO3 ‒ u N2O plin. Metoda je jednostavnija, brža i isplativija u odnosu na ostale laboratorijske metode. Iako je izotopna analiza vrijedan alat za praćenje dinamike nitrata, procesi nitrifikacije i denitrifikacije te prisutnost više izvora nitrata kompliciraju jednoznačno određivanje podrijetla i procesa transformacije nitrata. Zbog navedenoga, kombinacijom hidrogeokemijskih analiza, analiza izotopnog sastava stabilnih izotopa vode i stabilnih izotopa nitrata, analiza molarnih omjera, statističkih metoda i modela miješanja, moguće je pouzdanije odrediti podrijetlo i dinamiku nitrata. Ranija istraživanja bila su usmjerena na utvrđivanje podrijetla nitrata u zagrebačkom vodonosnom sustavu, procjenu trendova nitrata u podzemnoj vodi i određivanje područja s najvećim rizikom od onečišćenja nitratima. Izotopni sastav δ15NNO3 i δ18ONO3 bio je izmjeren dominantno na uzorcima podzemne vode te su rezultati pokazali da su nitrati u podzemnoj vodi zagrebačkog vodonosnog sustava pretežito organskog podrijetla, a većina analiza pokazala je izotopni sastav karakterističan za nitrate iz otpadnih voda. Iako su provedena istraživanja pojave dušika u podzemnoj vodi, nije istražena dinamika dušika u zoni tla i nesaturiranoj zoni, geokemijski i hidrodinamički procesi koji utječu na procjeđivanje nitrata u vodonosnik i na dinamiku nitrata u saturiranoj sredini, kao ni kvantifikacija udjela različitih izvora onečišćenja nitratima u podzemnoj vodi. Praćenje izvora i procesa koji utječu na stvaranje i transformaciju NO3 ‒ u podzemnoj vodi, kao i u zoni tla, važno je za bolje razumijevanje ciklusa dušika, zaštitu kakvoće vode i održivo upravljanje vodonosnim sustavom. Kako bi se, osim podrijetla, odredila i dinamika NO3 ‒, potrebno je mjeriti izotopni sastav δ15NNO3 i δ18ONO3 i u površinskoj vodi, oborini i procjednoj vodi iz tla. Također, potrebno je provesti i analizu izotopnoga sastava ukupnog dušika u čvrstim uzorcima različitih izvora dušika, što dosad još nije napravljeno na području istraživanja. Crpilište Velika Gorica jedno je od najvažnijih crpilišta Zagrebačke županije, koje opskrbljuje pitkom vodom Grad Zagreb i grad Veliku Goricu i nalazi se na desnom zaobalju rijeke Save u južnom dijelu zagrebačkog vodonosnog sustava. Zagrebački vodonosni sustav izgrađen je od nekonsolidiranih kvartarnih sedimenata, koji se sastoje uglavnom od pijeska, šljunka i praha ili prahovitih glina, i sadrži dva hidraulički povezana sloja, plitki i duboki. Plitki, holocenski vodonosnik izgrađen je od aluvijalnih naslaga, uglavnom šljunka i pijeska. U izravnoj je hidrauličkoj vezi s rijekom Savom, koja predstavlja glavni izvor prihranjivanja podzemne vode. Dublji, pleistocenski vodonosnik izgrađen je od jezersko-barskih naslaga s raznim udjelima šljunka, pijeska, praha i gline. Crpilište se sastoji od pet zdenaca dok se u priljevnom području crpilišta nalazi 13 piezometara koji se uglavnom koriste za praćenje kakvoće podzemne vode u plitkom vodonosniku. Unutar prve zone sanitarne zaštitne crpilišta Velika Gorica izgrađen je znanstveno istraživački poligon Rudarsko-geološko-naftnog fakulteta Sveučilišta u Zagrebu, u kojem su se provodila mjerenja za potrebe ovog istraživanja. Istraživački poligon se nalazi u eutričnom smeđem tlu na holocenskim nanosima. Debljina nesaturirane zone na istraživanom području obično varira od 5 do 8 metara i ovisi o razini podzemne vode. U gornjem dijelu nesaturirane zone određeni su sljedeći pedološki horizonti tla: A (0–0,15 m), 2B (0,15–0,55 m), 3BC (0,55–0,9 m) i C (0,9–1,17 m). Gornjih 90 centimetara profila tla uglavnom se sastoji od prahovitih i pjeskovitih materijala, s proslojcima gline, dok šljunak dominira u donjem dijelu profila, sve do razine podzemne vode. Unutar istraživačkog poligona nalazi se meteorološka postaja i pedološka jama opremljena instrumentima za promatranje i mjerenje parametara u nesaturiranoj zoni. Dominantan način korištenja zemljišta, u priljevnom području crpilišta Velika Gorica, je poljoprivredno korištenje u izmjeni s izgrađenim (urbanim) zemljištem. Ciljevi ovog istraživanja bili su: (1) odrediti ambijentalnu pozadinsku koncentraciju nitrata u hidrogeološki homogenom području heterogenog vodonosnog sustava pod dugotrajnim utjecajem ljudske aktivnosti, (2) implementirati titanij(III) redukcijsku metodu za analizu stabilnih izotopa dušika i kisika iz otopljenog nitrata, (3) poboljšati sveobuhvatno razumijevanje dinamike nitrata u nesaturiranoj i saturiranoj zoni na području eutričnog smeđeg tla na holocenskim nanosima zagrebačkoga vodonosnika i (4) definirati dominantni prirodni oblik dušika koji se iz zone tla infiltrira u vodonosnik priljevnoga područja crpilišta Velika Gorica. U skladu s navedenim ciljevima, postavljene su sljedeće hipoteze: (1) ambijentalna pozadinska koncentracija nitrata u podzemnoj vodi priljevnoga područja crpilišta Velika Gorica je niža od 10 mg/L NO3 ‒, (2) u području bez antropogenih aktivnosti, dušik se dominantno unosi iz zone tla (eutrično smeđe tlo na holocenskim nanosima) u nesaturiranu zonu u obliku nitrita i nitrata i (3) izvor nitrata u podzemnoj vodi priljevnoga područja crpilišta Velika Gorica nisu mineralna gnojiva. Kao najvažniji znanstveni doprinos treba istaknuti: unaprjeđenje poznavanja procesa transformacije dušikovih spojeva u tlu, nesaturiranoj zoni i vodonosniku; određivanje dinamike i podrijetla nitrata, kao i kvantifikaciju udjela različitih izvora dušika, primjenom stabilnih izotopa 15N i 18O u otopljenom nitratu i izotopa 15N u potencijalnim izvorima onečišćenja nitratima; i izradu konceptualnog modela dinamike dušikovih spojeva u nesaturiranoj i saturiranoj zoni zagrebačkog vodonosnog sustava. Zbog navedenoga, u priljevnom području crpilišta Velika Gorica, hidrogeološki homogenom području unutar zagrebačkog vodonosnog sustava, provedena su terenska i laboratorijska istraživanja, mjesečna uzorkovanja u trajanju od jedne godine, analize kakvoće podzemne i površinske vode, oborine i procjedne vode iz tla, kao i analize tla i različitih izvora dušika. Uzorci podzemne vode prikupljeni su iz 10 piezometara, a izmjerene su i razine podzemne vode u svrhu izrade karata ekvipotencijala za vrijeme visokih i niskih podzemnih voda. Uzorci površinske vode uzorkovani su iz rijeke Save na lokaciji Podsusedski most. Insitu mjerenja uključivala su: pH, električnu vodljivost, sadržaj otopljenog kisika i temperaturu. Uzorci procjedne vode iz tla prikupljeni su iz pedološke jame iz četiri horizonta tla, primjenom usisnih čašica. Satna mjerenja vlage u tlu i temperature tla provedena su pomoću TDR (engl. time domain reflectrometry) sonda, koje su instalirane u četiri horizonta tla. Meteorološka stanica, smještena blizu pedološke jame, kontinuirano je mjerila oborinu i temperaturu zraka, dok je oborina uzorkovana pomoću uzorkivača kiše. Svi tekući uzorci filtrirani su na terenu i pohranjeni u plastične HDPE (engl. high-density polyethylene) boce kako bi se obavile kemijske i izotopne analize. Čvrsti uzorci različitih izvora dušika prikupljeni su unutar područja istraživanja i uključivali su šest uzoraka organskog podrijetla i četiri uzorka mineralnog gnojiva. Organski uzorci uključivali su dva uzorka stajskog gnojiva, dva uzorka iz septičkih jama i dva uzorka otpadnih voda, dok su uzorkovana mineralna gnojiva uglavnom bila amonijska. Uzorci tla prikupljeni su do dubine od 1,2 metra po intervalima od 10 cm, blizu pedološke jame. U laboratorijima Rudarsko-geološko-naftnog fakulteta Sveučilišta u Zagrebu provedena su sljedeća mjerenja: analize glavnih aniona i kationa, analize izotopnog sastava stabilnih izotopa vode (δ2HH2O and δ18OH2O) i stabilnih izotopa nitrata (δ15NNO3 i δ18ONO3) u tekućim uzorcima, kao i analize odabranih fizikalno-kemijskih parametara u uzorcima tla. Uzorci za određivanje izotopnog sastava dušika i kisika iz nitrata pripremljeni su pomoću Ti(III) redukcijske metode. Analize izotopnog sastava ukupnog dušika (δ15Nbulk) i postotka dušika (%N) u čvrstim uzorcima različitih izvora dušika provedena su u laboratoriju Fakulteta geoznanosti Sveučilišta u Barceloni. U početnom koraku istraživanja, proveden je postupak procjene ambijentalne pozadinske koncentracije nitrata u svrhu definiranja prisutnosti onečišćenja podzemne vode. Ambijentalna pozadinska koncentracija nitrata procijenjena je korištenjem dostupnih povijesnih podataka o koncentraciji nitrata iz 12 piezometara smještenih u priljevnom području crpilišta Velika Gorica, korištenjem statističkih metoda temeljenih na modelima (iterativna 2σ tehnika, izračunata funkcija raspodjele, kumulativna frekvencijska krivulja i metoda temeljena na vjerojatnosnom grafu). Istodobno je testirana pouzdanost rezultata svake metode. Interpretacijom rezultata utvrđeno je da pozadinska koncentracija nitrata u priljevnom području crpilišta Velika Gorica iznosi od 7,1 do 7,5 mg/L, te se razlikuje od pozadinske koncentracije određene na razini zagrebačkog vodonosnog sustava. Istraživanje je pokazalo da N2O izotopni laserski uređaj GLA451-N2OI3, u kombinaciji s novijom metodom pripreme uzoraka, omogućava pouzdana mjerenja δ15NNO3 i δ18ONO3. Dinamika NO3 ‒ unutar eutričnog smeđeg tla i dominantni prirodni oblik N koji se infiltrira u vodonosnik definirani su na osnovi karakteristika tla i procjedne vode iz tla, primjenom parametarskih i neparametarskih statističkih testova, analizom i karakterizacijom fizikalnih i fizikalno-kemijskih parametara koji utječu na dinamiku dušikovih spojeva unutar zone tla te analizom izotopnog sastava stabilnih izotopa vode i nitrata u tlu. Rezultati su pokazali da su sadržaj vlage u tlu, pH, sadržaj organskog ugljika i tekstura tla važni faktori koji kontroliraju dinamiku dušikovih spojeva u zoni tla. Unutar najdubljeg horizonta tla (C horizont), koji je krupnozrnat, dušik je prisutan najvećim dijelom u obliku nitrita (NO2 ‒) i nitrata (NO3 ‒) kao rezultat nitrifikacije amonij iona (NH4 +) iz tla i procjeđivanja iz plićih horizonata uslijed oborina dužeg trajanja i jakog intenziteta. Uslijed takvih aerobnih uvjeta, koji omogućavaju stabilnost oksidiranih oblika dušika, omogućen je transport NO2 ‒ i NO3 ‒ u dublje dijelove nesaturirane zone. Izotopni sastav vode i model miješanja pokazao je da se podzemna voda na istraživanom području pretežno prihranjuje rijekom Savom, ali to prihranjivanje prostorno varira. Također, rezultati upućuju na postojanje različitog izvora prihranjivanja u južnom dijelu vodonosnika. Dinamika nitrata, podrijetlo i procesi koji utječu na transformaciju NO3 ‒ u podzemnoj vodi definirani su provedbom sveobuhvatnih analiza, koje su uključivale: analize fizikalno-kemijskih svojstava, hidrogeokemijske analize, analize izotopnog sastava stabilnih izotopa nitrata, analize molarnih omjera, statističke metode i model miješanja temeljen na Bayesovoj statistici. Interpretacijom rezultata utvrđeno je da su nitrati u istraživanom području najvećim dijelom organskog podrijetla, a nitrifikacija predstavlja glavni biogeokemijski proces koji se odvija u podzemnoj vodi, dok je proces denitrifikacije utvrđen na specifičnim lokacijama uzorkovanja kao rezultat anaerobnih uvjeta. Rezultati analize izotopnog sastava dušika u čvrstim uzorcima različitih izvora onečišćenja nitratima i modela miješanja temeljenog na Bayesovoj statistici su pokazali da su mineralna gnojiva značajan izvor onečišćenja nitratima na području zagrebačkog vodonosnog sustava i mogući uzrok povišenih koncentracija NO3 ‒ u podzemnoj vodi. Hidrogeokemijskim analizama, molarnim omjerima i korelacijskim analizama je utvrđeno postojanje različitih izvora onečišćenja nitratima u razdoblju uzorkovanja. Međutim, tim analizama nije jasno prepoznato onečišćenje koje dolazi iz mineralnih gnojiva. Iako takve metode predstavljaju vrijedan alat, trebaju se koristiti s dozom opreza kada nitrati potječu iz više izvora onečišćenja. Kroz istraživanje je istaknuta važnost primjene većeg broja metoda u svrhu pouzdanijeg i sveobuhvatnijeg razumijevanja onečišćenja nitratima
2D and 3D scans of granular rock material heaps and calibration models
No full textThe angle of repose (AoR) is critical for studying granular materials in mining, geotechnical engineering, pharmaceuticals, and agriculture. Accurate AoR measurements are essential for understanding material stability and movement. The descriptor includes photographs of 86 heaps of rock materials dolomite, quartz sand, marble, and gravel. In addition, photographs of 1 ideal cone and 4 CAD drawing models are provided. These images are processed using specialized software to create detailed 2D and 3D models of the heaps. The generated STL and point-cloud models can be used to calculate the AoR with high accuracy, taking into account the complex surface morphology that traditional methods may overlook. Additionally, these models enable standardized comparisons and can be used for calibration purposes. This data facilitates the development and validation of new AoR measurement methods, enhancing the reliability and consistency of granular material analysis