Daniel Moraetis

Characterization and mobility of geogenic chromium in soils and river bed sediments of Asopos basin

A field and laboratory study was conducted to assess the origin and mobility of CrVI in Asopos basin in Greece. Sampling was designed in such way as to capture the spatial variability of chromium occurring in sediments and soils in different lithological units in the area. Physicochemical and geochemical characterization of surface agricultural soils obtained from river terraces and river bed sediments was conducted in order to determine the natural background of chromium. Lithologies with strong calcareous, siliceous and ultramafic components were identified using principal component analysis. Laboratory mobility studies quantified the rates of chromium sorption and release from soils and their capacity to adsorb chromium. Heavy metal analysis and local geology study support the hypothesis that the main source of chromium is of geogenic origin. Chromium distribution in Asopos river bed was influenced from the eroded products derived from extensive areas with ultramafic rocks the last 5Ma. The mobility studies showed that leaching process was very fast and sorption capacity was significant and capable to retain chromium in case of waste release in the river. Finally the mobility of chromium release is limited due to existing attenuation capacity controlled by ferric oxides coatings on the soil and sediments.

Sediment provenance, soil development, and carbon content in fluvial and manmade terraces at Koiliaris River Critical Zone Observatory

PurposeThe purpose of this study was the investigation of sediment provenance and soil formation processes within a Mediterranean watershed (Koiliaris CZO in Greece) with particular emphasis on natural and manmade terraces.Material and methodsFive sites (K1–K5) were excavated and analyzed for their pedology (profile description), geochemistry [including rare earth elements (REEs) and other trace elements], texture, and mineralogy along with chronological analysis (optical luminescence dating). The selected sites have the common characteristic of being flat terraces while the sites differed with regard to bedrock lithology, elevation, and land use.Results and discussionThree characteristic processes of soil genesis were identified: (1) sediments transportation from outcrops of metamorphic rocks and sedimentation at the fluvial sites (K1–K2), (2) in situ soil development in manmade terraces (K3, K4), and (3) strong eolian input and/or material transported by gravity from upslope at the mountainous site (K5). REE patterns verified the soil genesis processes while they revealed also soil development processes such as (a) calcite deposition (K1), (b) clay illuviation and strong weathering (K4), and (c) possibly fast oxidation/precipitation processes (K3). Carbon sequestration throughout the soil profile was high at manmade terraces at higher elevation compared to fluvial environments due to both climatic effects and possibly intensive anthropogenic impact.ConclusionsSoils at Koiliaris CZO were rather young soils with limited evolution. The different soil age, land use, and climatic effect induced various soil genesis and soil development processes. The manmade terraces at higher elevation have much higher carbon sequestration compared to the anthropogenic impacted fluvial areas.

Environmental drivers of soil microbial community distribution at the Koiliaris Critical Zone Observatory.

Data on soil microbial community distribution at large scales are limited despite the important information that could be drawn with regard to their function and the influence of environmental factors on nutrient cycling and ecosystem services. This study investigates the distribution of Archaea, Bacteria and Fungi as well as the dominant bacterial phyla (Acidobacteria, Actinobacteria, Bacteroidetes, Firmicutes), and classes of Proteobacteria (Alpha- and Betaproteobacteria) across the Koiliaris watershed by qPCR and associate them with environmental variables. Predictive maps of microorganisms distribution at watershed scale were generated by co-kriging, using the most significant predictors. Our findings showed that 31-79% of the spatial variation in microbial taxa abundance could be explained by the parameters measured, with total organic carbon and pH being identified as the most important. Moreover, strong correlations were set between microbial groups and their inclusion on variance explanation improved the prediction power of the models. The spatial autocorrelation of microbial groups ranged from 309 to 2.226 m, and geographic distance, by itself, could explain a high proportion of their variation. Our findings shed light on the factors shaping microbial communities at a high taxonomic level and provide evidence for ecological coherence and syntrophic interactions at the watershed scale.

Ion exchange equilibrium and structural changes in clinoptilolite irradiated with β- and γ-radiation: Monovalent cations

Abstract Thermodynamic calculations of ion-exchange reactions were applied for clinoptilolite in a natural state and after irradiation with three doses of β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation (70 Mrad). Samples were equilibrated with binary systems of K+ ↔ Na+ and Cs+ ↔ Na+ at 25° and a total normality of 0.025 N. Selectivity for K was not affected after β-radiation with doses of 1012 and 1015 e/cm2 (ΔG° = -6.37 kJ/equiv, lnKα = 2.58 for the original clinoptilolite), whereas it increased considerably after 70 Mrad of γ-radiation (ΔG° = -7.88 kJ/equiv, lnKα = 3.18). Selectivity for Cs+ increased for the clinoptilolite irradiated with β-radiation (1012, 1015, 3 × 1016 e/cm2) and γ-radiation (70 Mrad). ΔG° and lnKα for original sample and Cs+ ↔ Na+ were -7.33 kJ/equiv and 2.96, respectively. Irradiated samples with β-radiation 1012, 1015, 3 × 1016 e/cm2 and 70 Mrad γ-radiation yielded ΔG° and lnKα -7.41, -8.83, -8.60, -8.25 kJ/equiv and 2.99, 3.57, 3.47, 3.33 for Cs+ ↔ Na+, respectively. Remarkable amorphization of clinoptilolite was observed after exposure at the highest dose of β-radiation (3 × 1016 e/cm2) with a concomitant decrease in cation-exchange capacity (CEC). Crystallographic parameters and especially exchangeable cation site coordinates were refined for all samples with the Rietveld method. Cesium-saturated samples exhibited changes in the cation sites Cs2 and Cs3, which are next to clinoptilolite channel walls with lower Al3+ for Si4+ substitution. The observed changes include a shift in cation sites Cs2 and Cs3 toward channel walls and occupancy decrease in site Cs2.

Effect of zeolite application on potassium release in sandy soils amended with municipal compost

The use of compost in enhancing organic carbon content and aggregation in soil has been widely studied in the last decades. Recently, compost is used in new environmental applications for the remediation of both contaminated groundwater and soil. However, compost addition increases by 10 orders of magnitude the soil electrical conductivity and the nutrient content such as potassium. Subsequently, nutrient leaching in groundwater may increase water salinity. The present study investigates the effect of zeolite application on potassium release in sandy soils amended with municipal compost. Kinetic experiments show that zeolite addition in soil-compost mixtures have no effect on potassium desorption rate while it results in an 18-fold increase in bio-available potassium. Column tests show that zeolite application results up to six times decrease in total potassium leaching. Experimental results show high potassium affinity for the mixture soil-compost-zeolite in pH > 7, which is of paramount importance, considering that soils in southern Europe (Italy, Spain, south France, Albania and Greece) exhibit slightly alkaline pH in most cases. The findings of this study may be also used to predict the potential of groundwater contamination in agricultural areas as well as during the implementation of preventive measures.

Ion exchange equilibrium and structural changes in clinoptilolite irradiated with β- and γ-radiation. Part II: Divalent cations

Thermodynamic calculations of ion exchange for divalent cations were made for clinoptilolite in natural state and after irradiation with three different doses of β-radiation (10 12 , 10 15 and 3 × 10 16 e/cm 2 ) and γ-radiation (70 Mrad). The samples were equilibrated with binary systems of divalent cations, namely Sr 2+ ↔ 2Na + , Ca 2+ ↔ 2Na + and Mg 2+ ↔ 2Na + at 25 °C and total solution normality of 0.025 N. The selectivity order Sr 2+ > Ca 2+ > Mg 2+ was observed in non-irradiated clinoptilolite. After irradiation with γ-radiation the affinity of clinoptilolite for Sr 2+ increased and that for Mg 2+ decreased, whereas the affinity for Ca 2+ remained unchanged. Irradiation with β-radiation influences selectivity order and clinoptilolite affinity decreases for Sr 2+ , whereas it increases for Ca 2+ . For the sample irradiated with maximum dose of β-radiation the selectivity was almost identical for Ca 2+ and Sr 2+ . The crystallographic parameters and exchangeable cation site coordinates were refined for all samples with the Rietveld method. The structure refinement of Sr 2+ -saturated samples yielded changes both in exchangeable sites and site occupancy in channels A and B after irradiation with β-and γ-radiation. The cation sites Sr1 and Sr3 exhibit major changes both in site coordinates and site occupancy after irradiation with β-radiation. In addition, irradiation with γ-radiation yielded major changes in Sr1 occupancy, whereas coordinates changed only slightly. These structural modifications control the observed changes in thermodynamic parameters after irradiation.

Chemical and physical characteristics in uncultivated soils with different lithology in semiarid Mediterranean clima

The aim of this study is to identify the chemical and physical characteristics in uncultivated soils derived from different parent materials under semiarid Mediterranean climatic conditions which favoured the formation of fragile soils. The current work is of great interest in the agriculture and environmental stakeholders for providing a “benchmark” of undisturbed soil quality regarding organic content and nutrients availability. Principal Component Analysis (PCA) was used as the primary tool to demonstrate the soil quality stage, regarding nutrient availability. The statistical analysis revealed that one of the major physicochemical characteristics such as cation exchange capacity (CEC) is controlled exclusively from mineralogy and not from organic matter. Mineralogy and bulk chemical analysis is directly related to soil parent material lithology. The availability of inorganic nutrients (macro- and micronutrients) is low and relatively identical to most of the soils. PCA shows the unusual correlation of K