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Highlights: [•] The samples are grouped into: ultramafic rocks, altered ultramafic rocks, troctolites, dolerites–diorites, and trachytes. [•] Factor analysis indicates a great number of interrelations between the aggregate properties. [•] The correlations among the aggregate properties reflect changes in their petrographic features. [•] Factor analysis contributes to a deeper understanding of the way that the properties of aggregates change in-service. [•] The mafic and fresh ultramafic rocks are the most suitable for use as aggregates. [Copyright &y& Elsevier]

Abstract: A soil and vegetation survey was undertaken in NW Euboea Island, Greece. The objectives of the study were to establish the geochemical baseline of soil and identify the impact of local geology on threshold values of potentially harmful elements. The studied area is characterized by complex geology comprising metamorphic and ultramafic rocks as well as active hot springs. A total of 117 soil samples were collected from 89 sites at depths of 0–25cm and 25–50cm. Eighteen vegetation samples were also collected representing prevalent indigenous perennial species in the region. Soil samples from the present study were enriched in As, Ca, Cu, Mg, Ni with concentrations reaching 233mg/kg, 38%, 336mg/kg, 10.8%, 1560mg/kg respectively. Factor analysis revealed three main factors controlling the chemical composition of soil reflecting the influence of ultramafic rocks (Cr, Ca, Mg, Ni), hot spring deposits (Ca, S, Sr, As) and paedogenesis processes (Fe, Co, V, Mn, Al). The first two of these factors showed significant spatial correlation with the geological features within the study area. Subsequently, baseline concentrations based on statistical and spatial data were estimated within sub-areas reflecting the influence of local geology in soil composition. Concentrations of potentially harmful elements in the plant tissues of indigenous perennial vegetation species showed a wide range of variation from below the detection limit up to 1700mg/kg for Ni in the hyperaccumulator Alyssum chalcidicum demonstrating that plant species have adapted to the stressful conditions caused by high elemental concentrations in soil. The results of this study can be utilized in future studies at areas of similar geology by providing an objective basis for setting realistic threshold values for pollution assessment and remediation. [Copyright &y& Elsevier]

Abstract: Lithogenic Ni and Cr enrichment in agricultural topsoils of Thiva Valley (central Greece) is the result of transport of weathered parent rock fragments from upslope ultramafic sources. Chemical and mineralogical evolution of these potentially toxic elements between the trace metal bearing bedrock and the overlying soil horizon along two weathering profiles located in an area where the ultramafic rocks are exposed was accomplished to unravel the source and mineral speciation dynamics of Ni and Cr in the soil system of Thiva Valley. Within the soil horizons, Ni primarily occurs in serpentine (average 0.5wt.% of NiO) and secondary weathering products like smectites (average 0.5wt.% of NiO) and goethite (average 1.1wt.% of NiO). Significant amounts of this element are also hosted in less abundant Mn (hydr)oxides. On the contrary, Cr is mainly bounded with inherited chromite (average 54.7wt.% of Cr2O3) and to a lesser extent with Cr-magnetite (average 12.2wt.% of Cr2O3) and Cr silicates like enstatite (average 0.8wt.% of Cr2O3). As a result of the solid speciation and the applied decomposition method (aqua regia digestion), the soil geochemical anomalies within the valley are more pronounced with respect to Ni (up to 2640mg/kg) compared to Cr (up to 856mg/kg). The geochemical baseline maps produced by the ordinary kriging interpolation method reveal a strong tendency for large Ni and Cr amounts in the southern part of the area warning about the potential occurrence of high metal values in soils of Thiva town with an approximate number of 25,000 exposed population. Based on the mineralogical residence of Ni and Cr differences in their potential bioavailability and leaching to groundwater are anticipated. [Copyright &y& Elsevier]

The hydrogeochemical processes and natural background levels (NBLs) of chromium in the ultramafic environment of Vermio Mountain, Western Macedonia, Greece, were studied. Seventy groundwater samples were collected from 15 natural springs between 2014–2020, and an extensive set of physical and chemical parameters were determined. The ultramafic-dominated environment of western Vermio Mt. favors elevated groundwater concentrations of dissolved magnesium (Mg2+), silicon (Si), nickel (Ni), and Cr in natural spring waters. Chromium was the principal environmental parameter that exhibited a wide range of concentrations, from 0.5 to 131.5 μg/L, systematically exceeding the permissible limit of 50 μg/L for drinking water. Statistical evaluation of hydrogeological, hydrochemical, and hydrological data highlighted the water-ultramafic rock process as the predominant contributor of Cr in groundwater. The NBL assessment for Cr and Cr(VI) was successfully applied to the typical ultramafic-dominated spring "Potistis" that satisfied all the methodology criteria. The NBLs of Cr and Cr(VI) were defined at 130 μg/L and 100 μg/L, respectively, revealing that a natural ultramafic-dominated environment exhibits the geochemical potential to contribute very high concentrations of geogenic Cr to groundwater. The holistic methodology, proposed herein, could be implemented in any catchment scale to assess geogenic and anthropogenic Cr-sources that degrade groundwater quality. [ABSTRACT FROM AUTHOR]

The holistic approach of Driver-Pressure-State-Impact-Response (DPSIR) methodology was applied to selected Cr(VI) impacted groundwater bodies of Central Greece. The main driving forces in the study areas are agricultural activities, urban and industrial development as well as tourism. The main pressures induced by the anthropogenic activities are fertilizer use, uncontrolled urban sewage disposal and industrial effluents discharges. Groundwater stress is caused by the qualitative degradation due to Cr(VI), NO 3 - , Cl - and SO 4 2- contamination. Hexavalent chromium occurrence is attributed to both geogenic and anthropogenic sources. The maximum Cr(VI) concentration (11.7 mg/L) was measured in Oinofyta area. Important impacts are the deterioration of groundwater body chemical status as well as the decline of groundwater use efficiency. Based on the applied DPSIR, a management framework is proposed in order to address the complex environmental issue of Cr(VI) in the study areas.

The aim of this paper is to provide a methodology including statistical tools and spatial techniques, in order to identify the various potential sources of chromium (Crtot) in the Sarigkiol basin, Western Macedonia, Greece, where elevated concentrations of Crtot in groundwater have been recorded since 1996. Integrated hydrochemical approach and statistical analyses including Pearson's correlation coefficient, multivariate statistical analyses (factor analysis and hierarchical cluster analysis), and spatial techniques (Moran's I spatial autocorrelation index and bivariate local indicator spatial association cluster map) were applied to evaluate the chemical analyses of 73 water samples, from irrigation wells, natural springs, and surface water. Both natural and anthropogenic sources of Crtot were recorded; the first (ultramafic-dominated environment) is strongly depicted on the natural spring water, in which Crtot concentrations as high as ~ 130 μg/L were recorded, whereas the second (agricultural activities) acts synergistically in the irrigation wells of the Sarigkiol basin, in which strong correlations of Crtot, P, and NO3− were defined. The paper highlights its findings by outlining the potential sources of elevated concentrations of Cr6+ in the Sarigkiol basin, stressing the need for a closer attention on the role of agricultural activities as an important, though commonly neglected, anthropogenic source of Crtot in groundwater. [ABSTRACT FROM AUTHOR]

This study provides a survey on potential Cr(VI) exposure attributed to drinking water in Greece. For this reason, a wide sampling and chemical analysis of tap waters from around 600 sites, supplied by groundwater resources, was conducted focusing on areas in which the geological substrate is predominated by ultramafic minerals. Results indicate that although violations of the current chromium regulation limit in tap water are very rare, 25% of cases showed Cr(VI) concentrations above 10 μg/L, whereas Cr(VI) was detectable in 70% of the samples (>2 μg/L). Mineralogy and conditions of groundwater reservoirs were correlated to suggest a possible Cr(VI) leaching mechanism. Higher Cr(VI) values are observed in aquifers in alluvial and neogene sediments of serpentine and amphibolite, originating from the erosion of ophiolithic and metamorphic rocks. In contrast, Cr(VI) concentration in samples from ophiolithic and metamorphic rocks was always below 10 μg/L due to both low contact time and surface area, as verified by low conductivity and salt concentration values. These findings indicate that under specific conditions, pollution of water by Cr(VI) is favorable by a slow MnO2-catalyzed oxidation of soluble Cr(III) to Cr(VI) in which manganese products [Mn(III)/Mn(II)] are probably re-oxidized by oxygen., (Copyright © 2014 Elsevier B.V. All rights reserved.)