Browse Our Earth and Environmental Sciences Journals
Earth and environmental sciences cover all planetary and Earth science aspects, including solid Earth processes, development of Earth, environmental issues, ecology, marine and freshwater systems, as well as the human interaction with these systems.
Earth and Environmental Sciences
Upon completion, the National Radioactive Waste Repository in Bátaapáti will provide safe storage for low- and medium-level radioactive waste. The emplacement chambers were excavated in a fractured, blocky, granitic rock mass approximately 240 m below surface. One of the tasks related to the repository development is the feasibility demonstration of the permanent repository closure, including long-term rock mass associated issues. The required lifetime exceeds the usual one of an engineering structure. The long-term behavior of the repository needs to be extrapolated from observation over a shorter time period, or from analogous natural caverns. Numerical methods are the most promising techniques to carry out the extrapolation. It is commonly understood that there are significant uncertainties in long-term predictions. Uncertainties can be mitigated by utilizing independent methods to assess long-term behavior and by improving the prediction capability of the calculation model in the short term. The aim of the paper is to: (1) create a numerical model to effectively capture a wide range of the observed behavior of the rock mass, including tunnel-excavation-induced stress change and stress-dependent permeability and (2) identify the possible cause of long-term creep and show that the long-term creep can be captured by the selected calculation method. The moderately fractured rock mass is modeled using the Universal Distinct Element Code, released by Itasca. The joints in the rock mass are explicitly modeled; the blocky nature of the rock mass is captured. The model is verified with actual field observations and monitoring results. Based on the predicted stress state of the rock mass, the potential cause of long-term creep is identified. By fulfilling the two aims explained above, it is concluded that the model can be used to extrapolate in time and serve as a possible estimation method for the long-term behavior of the repository.
Lithofacies definition in the subsurface is an important factor in modeling, regardless of the scale being at reservoir or basin level. In areas with low exploration level, modeling of lithofacies distribution presents a complicated task as very few inputs are available. For this purpose, a case study in the Požega Valley was selected with only one existing well and several seismic sections within an area covering roughly 850 km2. For the task of expanding the input data set for lithofacies modeling, neural network analysis was performed that incorporated interpreted lithofacies (sandstone, siltite, marl, and breccia-conglomerate) in a single well and attribute data gathered from a seismic section. Three types of different neural networks were used for the analysis: multilayer perceptron, radial-basis function, and probabilistic neural network. As a result, three lithofacies models were built alongside a seismic section based upon predictions acquired from the neural networks. Three lithofacies were successfully predicted on the section while the breccia-conglomerate was either missing or underpredicted and mostly positioned in a geologically invalid interval. Results obtained by single networks differed from one another, which indicated that a result from a single network should not be treated as representative; thus, the facies distribution for modeling should be acquired from either an ensemble of neural networks or several neural networks. Analysis showed the initial potential of the usability of neural networks and seismic attribute analysis on vintage seismic sections with possible drawbacks of the applications being pointed out.
In the present explorative study, different time-series analysis methods, such as moving average, deterministic methods (linear trend with seasonality), and non-parametric Mann–Kendall trend test, were applied to monthly precipitation data from January 1871 to December 2014, with the aim of comparing the results of these methods and detecting the signs of climate change. The data set was provided by the University of Pannonia, and it contains monthly precipitation data of 144 years of measurements (1,728 data points) from the Keszthely Meteorological Station. This data set is special because few stations in Hungary can provide such long and continuous measurements with detailed historical background. The results of the research can provide insight into the signs of climate change in the past for the region of West Balaton. Parametric methods (linear trend and t-test for slope) for analyzing time series are the simplest ones to obtain insight into the changes in a variable over time. These methods have a requirement for normal distribution of the residuals that can be a limitation for their application. Non-parametric methods are distribution-free and investigators can get a more sophisticated view of the variable tendencies in time series.
Modelling the flow and transport of fluids (water and non-aqueous phase liquids or NAPLs) in porous systems or soils requires the accurate and reliable determination of basic input modelling parameters, such as liquid retention (Pc–S) and conductivity (Ksat, Kh). Methods for the determination (measurement and estimation) of water retention and conductivity have improved enormously over the last 60 years (Table 1). Promising results verified the applicability of pedotransfer functions (PTF) and their incorporated versions into software and submodels. However, the development of models was only aimed at improving methods with which these hydrological parameters could be determined for water, while calculations for NAPLs can still only be made indirectly. Several studies (e.g. in the petroleum industry, and research for environmental or hydrological purposes) revealed differences in the relationship between the hydraulic properties and pore system of the porous solid phase. Interactions (swelling-shrinking, desaggregation, etc.) between the phases may be significantly different in water/soil and NAPL/soil systems, affecting the efficiency of modelling. However, relatively few well-documented results have been published on the measurement of these hydraulic properties for NAPL-type fluids using a sufficient number of real, especially undisturbed soils. The establishment of databases of this sort might provide a basis for creating and developing PTF-type estimation methods for predicting NAPL retention and conductivity. Furthermore, it might improve our knowledge on interactions specific to the solid and fluid phases of pore systems, and also on the soil properties influencing the pore size distribution of soils (e.g. soil structure, the size distribution, morphology or stability of aggregates) and their relationship with the hydrophysical properties of the soil.
In worst-case leakage scenarios of CO2 geological storage, CO2 or brine may contaminate shallower drinking water aquifers. This work applies an advanced geochemical modeling methodology to predict and understand the effects of the aforementioned contamination scenarios. Several possibilities, such as equilibrium batch, kinetic batch, and 1D kinetic reactive transport simulations, were tested. These have all been implemented in the widely applied PHREEQC code. The production of figures and animations has been automated by R programming. The different modeling levels provide complementary information to each other. Both scenarios (CO2 or brine leakage) indicate the increase of ion concentrations in the freshwater, which might exceed drinking water limit values. The dissolution of CO2 changes the pH and induces mineral dissolution and precipitation in the aquifer and therefore changes in solution composition. Brine replacement of freshwater due to the pressure increase in the geological system induces mineral reactions as well.
The present study investigated the quantity of total suspended solids (TSS) in three small catchments and compared the data to turbidity measurements. The TSS data were based on filtration, drying and weight measurements, while the turbidity measurements were retrieved using a handheld device with a turbidity sensor. Water was collected daily at the catchment outlets from November 1, 2016 to May 31, 2017, representing the winter and spring seasons. The lowest quantity of TSS was detected at the catchment outlet of the Esztergályi Stream; however, there were two lakes close to the monitoring point where soil particles may have settled, possibly explaining the low TSS values. The Csorsza and Tetves streams had similar TSS values during winter, but in the spring samples the TSS values were approximately three times higher in the Csorsza Stream than in the Tetves Stream. The relationship between water discharge and TSS values was also investigated for the Tetves Stream, but no significant correlations were observed between them. The results suggested that the labour-intensive TSS measurements (e.g. filtration, soil weight measurements) could be replaced to a good approximation using the handheld device. The spatial heterogeneity within and between the catchments influences the amount of suspended sediment and hence the measurement accuracy. Therefore, the use of the handheld device should also be complemented with other methods, such as the filtration used in the present study, to attain more precise values.
The Micro-Deval test method is used for testing of aggregate durability. The present paper focuses on two Hungarian andesites obtained from the quarries of Recsk (Mátra Mountains, Hungary) and of Nógrádkövesd (Cserhát Mountains, Hungary). The aim of this study is to find a simple test method based on the original Micro-Deval test method to assess the long-term durability of aggregates. An additional part of the research was to develop suitable mathematical models that can describe the behavior of the andesite aggregates under continuous abrasive impact. The relevant standard (EN 1097-1:2012) recommends 12,000 rotations to determine the Micro-Deval coefficient required for classification of the aggregates. Within the framework of this research, a modified Micro-Deval test was applied: the number of rotations was increased in several steps and the degree of abrasion was measured afterwards. Regression analyses were used to outline mathematical forms which characterize the dependence between the number of rotations and the degree of abrasion. According to the results, the long-term Micro-Deval tests significantly modify the assessed durability and thus provide information on the long-term abrasive impact. The degree of change depends on the studied material: the ratio of the long-term Micro-Deval coefficients of the two studied andesite types is larger than 3. The regression analyses of the measured Micro-Deval coefficients revealed that quadratic curves are suitable to describe these tendencies for both andesite aggregates.
The aim of the research was to study the effect of N, P and K supplies on the nutritional status of faba bean in a long-term mineral fertilisation experiment and to determine the nutrient concentrations and nutrient ratios associated with satisfactory nutritional status. The long-term fertilisation experiment was set up in 1989 on chernozem meadow soil calcareous in the deeper layers, with all possible combinations of four levels each of N, P and K supplies, giving a total of 64 treatments. The present paper discusses the results obtained in 2001 and 2002, which can be summarised as follows:
Interactions between the elements N, Cu and Mo were studied on alfalfa in 1996-1999 in a field experiment set up on chernozem loam soil with lime deposits. The ploughed layer of the soil contained 3% humus, around 5% CaCO3 and around 20% clay. Soil analysis showed that the area was well supplied with Ca, Mg, K and Mn had satisfactory Cu content, but was only poorly or moderately supplied with P and Zn. The groundwater depth was 13–15 m and the area was prone to drought. The experiment was originally set up in a split-plot design with 4N × 3Cu = 12 treatments in three replications, giving a total of 36 plots. The N rates, applied as calcium ammonium nitrate, were 0, 100, 200 and 300 kg·ha−1 and the Cu rates, in the form of CuSO4, were 0, 50 and 100 kg·ha−1. In the 5th year of the experiment the 15 m long plots were halved and the two half-plots were separated by a 1 m path. The experiment thus became a strip-split-plot design, consisting of 4N×3Cu×2Mo = 24 treatments in three replications, giving a total of 72 plots. The 48 kg·ha−1 Mo was applied in the form of (NH4)6Mo7O24·4H2O. The main results were as follows:
