Environmental Acceptability of Geotechnical Composites from Recycled Materials: Comparative Study of Laboratory and Field Investigations.

The environmental properties of three geotechnical composites made by recycling wastes were investigated on a laboratory scale and in the field with the use of lysimeters designated for the revitalization of degraded mining sites. Composites were prepared by combining the mine waste with paper-mill sludge and foundry sand (Composite 1), with digestate from municipal waste and paper ash (Composite 2), and with coal ash, foundry slag and waste incineration bottom ash (Composite 3). The results of laboratory leaching tests proved that Composites 1 and 3 are environmentally acceptable, according to the legislative limits, as the potentially hazardous substances were immobilized, while in Composite 2, the legislative limits were exceeded. In the field lysimeters, the lowest rate of leaching was determined for optimally compacted Composites 1 and 3, while for Composite 2 the leaching of Cu was high. This study proved that optimally installed Composites 1 and 3 are environmentally acceptable for use in construction as an alternative to virgin materials, for the revitalization of degraded mining sites or, along with Composite 2, for closure operations with landfills. In this way, locally available waste streams are valorised and channelized into a beneficial and sustainable recycling practice.

Comparison of prediction methods for oxygen-18 isotope composition in shallow groundwater.

Groundwater is the most important source of drinking water in the world. Therefore, information on the quality and quantity is important, as is new information related to the characteristics of the aquifer and the recharge area. In the present study we focused on the isotope composition of oxygen (δ18O) in groundwater, which is a natural tracer and provides a better understanding of the water cycle, in terms of origin, dynamics and interaction. The groundwater δ18O at 83 locations over the entire Slovenian territory was studied. Each location was sampled twice during the period 2009-2011. Geostatistical tools (such us ordinary kriging, simple and multiple linear regressions, and artificial neural networks were used and compared to select the best tool. Measured values of δ18O in the groundwater were used as the dependent variable, while the spatial characteristics of the territory (elevation, distance from the sea and average annual precipitation) were used as independent variables. Based on validation data sets, the artificial neural network model proved to be the most suitable method for predicting δ18O in the groundwater, since it produced the smallest deviations from the real/measured values in groundwater.

The isotope altitude effect reflected in groundwater: a case study from Slovenia.

This paper presents the stable isotope data of oxygen (δ(18)O) and hydrogen (δ(2)H) in groundwater from 83 sampling locations in Slovenia and their interpretation. The isotopic composition of water was monitored over 3 years (2009-2011), and each location was sampled twice. New findings on the isotopic composition of sampled groundwater are presented, and the data are also compared to past studies regarding the isotopic composition of precipitation, surface water, and groundwater in Slovenia. This study comprises: (1) the general characteristics of the isotopic composition of oxygen and hydrogen in groundwater in Slovenia, (2) the spatial distribution of oxygen isotope composition (δ(18)O) and d-excess in groundwater, (3) the groundwater isotope altitude effect, (4) the correlation between groundwater d-excess and the recharge area altitude of the sampling location, (5) the relation between hydrogen and oxygen isotopes in groundwater in comparison to the global precipitation isotope data, (6) the groundwater isotope effect of distance from the sea, and (7) the estimated relation between the mean temperature of recharge area and δ(18)O in groundwater.

Carbonate chemistry and isotope characteristics of groundwater of Ljubljansko polje and Ljubljansko Barje aquifers in Slovenia.

Ljubljansko polje and Ljubljansko Barje aquifers are the main groundwater resources for the needs of Ljubljana, the capital of Slovenia. Carbonate chemistry and isotope analysis of the groundwater were performed to acquire new hydrogeological data, which should serve as a base for improvement of hydrogeological conceptual models of both aquifers. A total of 138 groundwater samples were collected at 69 sampling locations from both aquifers. Major carbonate ions and the stable isotope of oxygen were used to identify differences in the recharging areas of aquifers. Four groups of groundwater were identified: (1) Ljubljansko polje aquifer, with higher Ca(2+)values, as limestone predominates in its recharge area, (2) northern part of Ljubljansko Barje aquifer, with prevailing dolomite in its recharge area, (3) central part of Ljubljansko Barje aquifer, which lies below surface cover of impermeable clay and is poor in carbonate, and (4) Brest and Iski vrsaj aquifer in the southern part of Ljubljansko Barje with higher Mg(2+) in groundwater and dolomite prevailing in its recharge area. The radioactive isotope tritium was also used to estimate the age of groundwater. Sampled groundwater is recent with tritium activity between 4 and 8 TU and residence time of up to 10 years.