Comparison of the impacts of elevated CO₂ soil gas concentrations on selected European terrestrial environments

Selected European studies have illustrated the impacts of elevated CO₂ concentrations in shallow soils on pasture. For the first time, general unified conclusions can be made, providing CO₂ thresholds where effects on plants and soil microbiology are observed and making recommendations on how this information can be used when planning projects for CO₂ storage. The sites include those where CO₂ is being naturally released to the atmosphere from deep geological formations; and a non-adapted site, with no previous history of CO₂ seepage, where CO₂ has been injected into the unsaturated soil horizon. Whilst soil gas concentrations will be influenced by flux rates and other factors, the results suggest that a concentration of between 10% and 15% CO₂ soil gas at 20 cm depth, which is within the root zone, is an important threshold level for observing changes in plant coverage. Site-specific plant ‘indicators’ are also observed for CO₂ concentrations at ≥35%. Microbiological changes are seen where CO₂ soil gas concentrations are between 15% and 40%. As part of site characterisation, an evaluation of the risks of leakage and their potential environmental impacts should be undertaken

The Zeolites from evros region, northern greece: A potential use as cultivation substrate in hydroponics

Zeolite tuff deposits located in the sedimentary basins of Orestias and Ferres-Alexandroupolis, Evros County, Greece are studied to determine their suitability as hydroponic substrate, used various mineralogical and chemical techniques. Large bodies of greenish to yellowish, massive zeolitic tuffs occur in the Metaxades, Pentalofos, Twin Hills and Palestra areas of Orestias basin as well as in Makrylofos, Doriskos and Kavissos of Ferres-Alexandroupolis basin. The zeolite tuff deposits of Ferres-Alexandroupolis basin consists mainly of clinoptilolite and mordenite assemblages, accompanied by silica polymorphs and feldspars. Contrary, the zeolite tuffs of Orestias basin are very rich in clinoptilolite or heulandite (Metaxades deposit), whilst mordenite is almost absent. The tuffs from Pentalofos and nearby Twin Hills and Palestra areas are extremely rich in clinoptilolite, reaching 90% of the total mineral content, while 10%, is represented by cristobalite and/or feldspars. All the zeolite tuff deposits studied had high cation exchange capacity and almost neutral pH. The non-dependence of the ion exchange capacity to different particles size could be prove beneficial in hydroponic cultivations, as particles of large grain size may be used without any effect on the quality of the material. The tuffs contain exchangeable potassium, calcium and magnesium, and, therefore, certain plants could use them as a source for these elements. Although zeolitic tuffs of the Doriskos-Kavissos area have high Cation Exchange Capacities (CEC), the presence of chlorine ions, as well as large quantities of exchangeable sodium might lead to toxicity of plants grown in such substrates. The Metaxades tuffs display the lowest CEC of all the Greek samples examined. The Palestra-Pentalofos zeolite tuff deposits combine: high CEC, absence of chlorine ions and relatively low exchangeable sodium. The parameters above make most of the tuff deposits studied suitable for use in hydroponics

Petrogenetic constraints on the origin and formation of the Hellenic Triassic rift-related lavas

Triassic rift-related volcanic rocks outcrop over all mainland Greece, comprising of trachybasalts and basaltic trachyandesites. Relatively immobile to the effects of alteration processes major and trace element abundances classify the volcanics into OIB and E-MORB lavas. They have mainly been distinguished based upon their: i) LREE contents, ii) silica-saturation index (S·I.), iii) Zr/Nb and Nb/Y ratio values; iv) Th, U, and Ta contents v) geotectonic discrimination diagrams. Their geochemistry indicates that most rocks were affected by moderate to extensive differentiation processes, mostly expressed by clinopyroxene fractionation. Some of the OIB and E-MORB volcanics are considered as primitive undersaturated, displaying (low SiO2, Zr/Nb and S.I. values, enhanced CaO/Al2O3 ratios). Calculated average mantle potential temperatures are comparable (1410 °C OIB; 1370 °C E-MORB), with melt fractions estimated at 3–5% for primary OIB magmas and 6–8% for primary E-MORB magmas. An asthenospheric origin is inferred for the OIB lavas, with melting in the garnet stability field (75–95 km; 2.5–3.0 GPa), whereas E-MORB parent magmas were formed with melting in the garnet/spinel (transitional) stability field (55–70 km; 1.8–2.2 GPa). The Hellenic Triassic rift-related lavas were most likely generated and erupted after lithospheric attenuation and extension, followed by subsequent asthenospheric upwelling of the mantle. The high calculated partial melting degrees and the observed thick and voluminous lava formations account for fast-spreading of the Tethys ridge during the Triassic. Temperature results suggest that the Hellenic Triassic rift-related magmas were generated from mantle at ambient temperature, render a mantle plume-based scenario improbable. © 2020 Elsevier B.V

The Late Cretaceous magmatic arc of the south Aegean: Geodynamic implications from petrological and geochemical studies of granitoids from Anafi island (Cyclades–Greece)

In the Aegean region (Cyclades–Greece), a large part of the Island of Anafi consists of exhumed high-grade metamorphic sequences (amphibolites, serpentinites and metasediments) that have been intruded by Late Cretaceous intermediate and felsic granitoids. These correspond to I-type arc-related rocks, displaying calc-alkaline geochemical affinities. Variability in their petrographic features, mineral composition and geochemistry is assigned to differentiation processes that mostly involved plagioclase and/or K-feldspar, and to a lesser extent amphibole and biotite. Mineral chemistry and geochemical results suggest that the Anafi granitoids are highly comparable with the Late Cretaceous granitoid intrusive rocks from East Crete and Donousa island. The amphibole and zircon saturation thermometry yields relatively moderate temperature crystallization conditions (~790°C) for the intermediate granitoids and lower for the felsic granitoids (~630°C). Geobarometric calculations based upon the chemistry of magnesiohornblende, as well as the normative (Qz), (Ab) and (Or) contents clearly point to shallow intrusion conditions (~2.0–6.5 kbar), corresponding to an estimated depth of crystallization of ~12 ± 4 km. The thrust sheets that overly the Palaeogene flysch in Anafi (metasediments with serpentinized peridotites, amphibolites and metabasites), constitute a subducted and metamorphosed oceanic sequence. These metamorphic units likely represent a part of the Pindos–Cycladic Blueschist Unit domain that was subducted at an earlier pre-Campanian stage. In the hydrated mantle wedge, incorporation of shallow level granitoids within metamorphic units was likely facilitated via corner flow intrusion mechanisms. Following the intrusion, the granitoid rocks were exhumed in a syn-convergent setting, along with the metamorphic thrust sheets, by continuous underplating of more external units, thus, escaping penetrative ductile deformation. © 2021 Informa UK Limited, trading as Taylor & Francis Group

Removal of Cu (II) from industrial wastewater using mechanically activated serpentinite

We investigate with this study the effectiveness of mechanically activated serpentinite in capturing Cu (II) from the multi-constituent acidic wastewater of the pit lakes of the Agios Philippos mine (Greece), proposing specific areas with serpentinites suitable for such environmental applications. For this purpose ultramafic rock samples that are characterized by variable degrees of serpentinization from ophiolitic outcrops exposed in the regions of Veria-Naousa and Edessa have been examined regarding their capacity to remove the toxic load of Cu (II) from wastewater after having been mechanically activated through a Los Angeles (LA) machine (500, 1000 and 1500 revolutions). The more serpentinized and mechanically activated samples, as they have been characterized after a combination of various mineralogical, petrographic, geochemical analyses as well as after different stresses of abrasion and attrition, seem to be more effective in Cu removal than the less serpentinized ones. Selective removal of Cu (II) in the wroewolfeite phase was obtained by using the mechanically activated highly serpentinized ultramafic rocks. Furthermore, areas with highly serpentinized ultramafic rocks defined after petrographic mapping, using GIS method, which can potentially be used as filters for the effective Cu (II) removal from industrial wastewater are suggested. © 2020 by the authors