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Povzetek: Remediation of contaminated soil can be performed by using various techniques, which must be adequately tailored for each specific case. The aim of this research is to critically evaluate the potential use of red mud and paper ash and a combination of the two as immobilization additives for the remediation of contaminated soil from one of the most polluted sites in Slovenia. The proposed procedure involves the preparation of geotechnical composites made from contaminated soil and mixed with 25 wt% of immobilization additives and an optimal quantity of water to achieve consistency, at which maximum compaction according to the Proctor Compaction Test procedure can be achieved. The results reveal a positive, time-dependent trend for the immobilization of potentially toxic elements in the composite with paper ash, because of the formation of the new hydration products with potentially toxic elements. In a composite containing only red mud, potentially toxic elements were immobilized by sorption mechanisms with no general time-dependent trends. The composite with a combination of additives demonstrates the remediation characteristics of both red mud and paper ash. Using this approach excavated contaminated soil, red mud and paper ash can be successfully recycled in the proposed composites, which can be beneficially used in situ for rehabilitation of contaminated sites. Nevertheless, mobilization of some potentially toxic elements at high pHs may represent a limiting factor and has to be taken into the consideration when a combination of red mud and paper ash is used as immobilization additive.
Ključne besede: red mud, paper ash, contaminated soil, potentially toxic elements, geotechnical composites
Objavljeno v DiRROS: 31.08.2023; Ogledov: 155; Prenosov: 118
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Povzetek: Paper-ash is used for remediation of heavily contaminated soils with metals, but remediation efficiency after longer periods has not been reported. To gain insights into the mechanisms of immobilization of cadmium (Cd), lead (Pb), and znic (Zn), a study was performed in the laboratory experiment in uncontaminated, artificially contaminated, and remediated soils, and these soils treated with sulfate, to mimic conditions in contaminated soil from zinc smelter site. Remediation was performed by mixing contaminated soil with paper-ash to immobilize Cd, Pb, and Zn in the geotechnical composite. Partitioning of Cd, Pb, and Zn was studied over one year in seven-time intervals applying the sequential extraction procedure and complementary X-ray diffraction analyses. This methodological approach enabled us to follow the redistribution of Cd, Pb, and Zn over time, thus, to studying immobilization mechanisms and assessing the remediation efficiency and stability of newly formed mineral phases. Cd, Pb, and Zn were effectively immobilized by precipitation of insoluble hydroxides after the addition of paper-ash and by the carbonization process in insoluble carbonate minerals. After remediation, Cd, Pb, and Zn concentrations in the water-soluble fraction were well below the limiting values for inertness: Cd by 100 times, Pb by 125 times, and Zn by 10 times. Sulfate treatment did not influence the remediation efficiency. Experimental data confirmed the high remediation efficiency and stability of insoluble Cd, Pb, and Zn mineral phases in geotechnical composites.
Ključne besede: cadmium, lead, zinc, contaminated soil, paper ash, immobilization mechanisms
Objavljeno v DiRROS: 04.07.2023; Ogledov: 213; Prenosov: 140
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Povzetek: We investigated several aspects of windthrow that are relevant to our understanding and management of forest ecosystems. As an example, we used an extreme event in December 2017, when the strongest storm in recent history occurred in the Slovenian Dinaric High Karst. We examined influential factors such as soil properties, wind speed, precipitation and ecological consequences for the affected forests. Soil properties were measured around standing and fallen silver fir trees at all three research sites. Tree species composition in the regeneration was observed on plots with chemical and acoustic ungulate deterrents and on control plots without deterrents. Economic estimates of yield loss due to damage were calculated at the national level. A model of the potential threat from windthrow was also developed based on data collected from windthrow events and meteorological data over the past 20 years. Our results indicate that soil depth and mineral fraction depth were similar at sites with and without damaged trees and were not the determining factors for tree toppling. Plots with acoustic deterrents showed the most effective regeneration development, the least decline in silver fir and the greatest increase in noble hardwood seedlings, while plots with chemical deterrents showed the least browsing damage. The estimated economic loss of €16.1 million is 6.6% less than the harvest under normal conditions. The economic loss was relatively low due to the nature of the storm, with the predominant type of damage being uprooted trees with no damaged trunks. The windthrow hazard model revealed that a large number of consecutive events with strong winds in each section weakened the stand, which was subsequently knocked down during the next extreme wind and rainfall event.
Ključne besede: natural forest regeneration, windthrow, economic loss, browsing, ungulate deterrents, forest soil properties, potential threat model
Objavljeno v DiRROS: 27.06.2023; Ogledov: 730; Prenosov: 383
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Povzetek: Sedimentation is a naturally occurring process of allowing particles in water bodies to settle out of the suspension under a gravity effect. In this study, the sediments of the Drava River were fully investigated to determine the heavy metal concentrations along the river and their potential reuse in the construction sector. Naturally dehydrated sediments from the Drava River were tested as an additive for the production of fired bricks. The dredged sediments were used as a substitute for natural brick clay in amounts up to 50% by weight, and it was confirmed that up to 20% by weight of the added sediment could be used directly in the process without critically affecting performance. Finally, the naturally dehydrated sediments were also evaluated for their use as a filling material in the construction of levees. The natural moisture content of the dehydrated sediment was too high for it to be used without additives, so quicklime was added as an inorganic binder. The test results showed an improvement in the geotechnical properties of the material to such an extent that it is suitable as a filling material for levees.
Ključne besede: sediment, pollution, clay industry, soil stabilization, open access
Objavljeno v DiRROS: 31.05.2023; Ogledov: 174; Prenosov: 93
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Povzetek: Norway spruce (Picea abies [L.] Karst.) has been at the centre of controversy for many decades. Recent evidence of its profound disturbance-induced damage and consequent stock depletions across forest landscapes in Europe has reinforced doubts regarding the sustainability and prospects of this tree species in the future. Like many other European countries, Slovenia has experienced significant Norway spruce mortality and a decrease in growing stock primarily as the result of several disturbance agents (bark beetle outbreaks, an ice storm, windthrows). We investigated a countrywide spruce growing stock decline based on data between 2010 and 2018. Particular focus was placed on identifying the main ecological drivers of this decline, namely geological conditions, climatic parameters, soil attributes, topographic factors and forest stand characteristics. The effects of potential predictors on the relative change (%) in spruce volume (m3 ha-1) during the period 2010-2018 were analysed with Generalized Additive Models. Based on a national dataset including forest compartments (n = 6355) with a spruce growing stock decline > 10%, we found mixed support for ecology-based hypotheses. While spruce decline responded to bedrock type as predicted (i.e., greater relative decline in carbonate compared to silicate compartments), higher forest naturalness (preservation of tree species composition) was not associated with a lower decline. Spruce decline was amplified by higher potential evapotranspiration and soil clay content but showed a strong negative relationship with spruce proportion in the year 2010. General trends along the gradients of other selected predictors (stoniness/rockiness and heat load index) were less pronounced. The results suggest that most of these ecological predictors interact with geology and forest naturalness in affecting Norway spruce decline. Our analysis reveals that bedrock type can play an important role due to its mitigating effects. However, forest naturalness is of secondary significance as intensified large-scale forest disturbances likely override its buffering potential.
Ključne besede: Norway Spruce, bark beetle outbreaks, ice storm, soil-geology, relationship, tree species composition, Slovenia
Objavljeno v DiRROS: 05.04.2023; Ogledov: 591; Prenosov: 129
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