The appearance of online map services and frameworks (e.g., KML, QGIS) has increased the possibilities to easily, quickly and—in many cases—cost-effectively publish spatial data stored in databases. The aim of this study is to present the geovisualization of spatial databases of a Hungarian settlement on the web, using the open source webGIS system and Google application programming interfaces (APIs). The interactive point and interpolated distribution maps available online provide a detailed picture of the level of contamination, the spatial distribution of the ground water supply of the investigated settlement, and the changes which have occurred following the establishment of the sewage system. In the case of PO43− we determined that in the year before the sewage system was constructed, most of the area of the settlement could be considered contaminated, with the highest level of contamination measured in the central area of the settlement. Five years after the construction of the sewage system, the ratio of the contaminated areas had significantly decreased. In the case of NO3− we found a high level of contamination before the construction of the sewage system with a concentration increase in a North–West direction. After the establishment of the sewage system, the increase in concentration was the most intense in the central parts of the settlement, while the characteristic spatial distribution could no longer be observed. The geovisualization techniques developed are able to provide information about the different spatial data for users in a visual way, and also help to understand better the spatial information using a cognitive approach. The advantage of interactive web maps created with the technologies applied over traditional static maps is a new approach, which allows the user to manipulate the temporal and spatial data directly in the most appropriate way.
In our study we attempt to demonstrate the effects of uninsulated sewage tanks, which are the most important sources of contamination in settlements without sewage systems, on groundwater quality. We compared the results of measurements carried out before and one and a half years after the construction of the sewage system. We established 3 m deep monitoring wells within a 25 m radius of a sewage tank, which were then sampled, and the level of groundwater was recorded. The 3D model constructed on the basis of the saturated zone shows that the effluent wastewater formed a groundwater level dome with a height of more than 1 m. After the sewage tank was taken out of use the difference between the highest and lowest groundwater levels decreased to a few centimetres. In our study we investigated the spatial distribution of NH4+(ammonium). Using the 3D model we were able to precisely determine the volume of water bodies with different levels of contamination. In an approximately 25 m3water body, in the immediate environment of a sewage tank in use we detected NH4+at a concentration which was characteristic of undiluted wastewater (>90 mg·dm−3). After the sewage tank was taken out of use, the concentration in its immediate environment decreased by more than 50%, although almost everywhere in the modelled area concentrations were measured above the limit value. Based on the above, we can conclude that the cleaning process has started, but the complete decontamination of the groundwater will take several years.
In this study the effects of nitrogen effluent from a permeable constructed sewage tank on groundwater quality were investigated. Sampling took place before and 1.5 years after the closure. Using a 3D hydrogeological model, the spatial distribution of dissolved inorganic nitrogen (DIN), comprising the species NH4+, NO2- and NO3-, was modelled in the saturated zone and the amounts and changes in the ratio of NH4-N, NO2-N, NO3-N were determined. The first part of our general hypothesis, that the groundwater was heavily contaminated in the area surrounding the sewage tank, was clearly verified, since every investigated nitrogen compound exceeded the contamination limit values; but the second part of our hypothesis, that the degree of contamination would significantly decrease after the sewage tank was taken out of use has not been confirmed, since the amount of nitrogen present in inorganic forms increased in the modelled zone. The increase in DIN and the relatively high concentration of NH4+ (35 mg/L) in the immediate vicinity of the tank can be explained by the fact that organic matter (OM) accumulated over the decades provided a constant supply of inorganic nitrogen forms.
This research aims to assess the hydrogeochemical evolution of the groundwater in Oued souf valley for drinking and irrigation purposes. To achieve this, 49 groundwater samples from the complex terminal were examined and treated concurrently with multivariate statistical methods, geostatistical modeling and the WQI (water quality index). Focusing on the physico-chemical parameters, Q mode clustering analysis detected four major water groups, where the mineralization augmented from group 1 to group 4. The hydro-chemical type was the same, Ca-Mg-Cl-SO4 for all the groups. Calcite, dolomite, anhydrite, and gypsum would be the dominant reactions with the undersaturation of evaporates minerals, based on geochemical modeling, while the carbonate minerals are precipitating. Geostatistical analysis using ordinary Kriging demonstrated the exponential semi-variogram model fitted for EC (electrical conductivity), Ca2+ (calcium), Mg2+ (magnesium), K+ (potassium), HCO3− (bicarbonate), Cl− (chloride), and SO42− (sulfate). At the same time, the rational quadratic model was the best-fitted semi-variogram model for Na+ (sodium) and NO3− (nitrate). EC, SO42−, and NO3− have a strong spatial structure, while Ca2+, Na+, K+, and HCO3− have a moderate spatial structure. Moreover, there was a weak spatial structure for Mg2+ and Cl−. The WQI shows that CT (complex terminal groundwater aquifers) are not suitable for drinking and their quality for irrigation fluctuates from excellent to moderate quality.
Abstract:In our study, we tested the existing and freely accessible soil databases covering a smaller geographical region surveyed and classified according to the Hungarian classification in order to approximate the WRB soil reference groups (RSG). We tested the results and applicability of approximation for the RSG with three different methods on 12 soil profiles. First, RSGs were assigned to Hungarian soil taxa based on results of previous correlation studies, secondly, a freely accessible online database of ISRIC was applied furthermore, and an automated reclassification developed and programmed by us was used, which takes the original soil data as input.
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