Search Results (18)

Antimony is one of the world’s scarcest metals and is listed as a Critical Raw Material (CRM) for the European Union. To meet the increasing demand for metals in a sustainable way, one of the strategies that could be implemented would be the recovery of metals as by-products. This would decrease the amount of hazardous materials filling mining dumps. The present study investigates the potential for producing antimony as a by-product at the Olympias separation plant in Northern Greece. This plant works a skarn mineralization that shows interesting amounts of Sb. Boulangerite (Pb₅Sb₄S₁₁) reports on Pb concentrate levels reached 8% in the analyzed product. This pre-enrichment is favorable in terms of boulangerite recovery since it can be separated from galena through froth flotation. Boulangerite distribution in the primary ore is quite heterogeneous in terms of the inclusion relationships and grain size. However, a qualitative assessment shows that the current Pb concentrate grain size is too coarse to successfully liberate a good amount of boulangerite. The use of image analysis and textural assessments is pivotal in determining shape factors and crystal size, which is essential for the targeting of flotation parameters during separation. The extraction of antimony as a by-product is possible through a two-step process; namely, (i) the preliminary concentration of boulangerite, followed by (ii) the hydrometallurgical extraction of the antimony from the boulangerite concentrate. The Olympias enrichment plant could therefore set a positive example by promoting the benefits of targeted Sb extraction as a by-product within similar sulfide deposits within the European territory. Full article

The use of toxic chemicals as flotation reagents raises concerns about the sustainability of the process and its environmental impact. Xanthates are a family of efficient collectors that find application in the selective recovery of lead, gold and zinc ores, but they are toxic, with the majority of them being imported from eastern countries. Recently, organosolv lignin (OLN) micro- and nanoparticles have been produced and tested as collectors in the flotation of Cu minerals with positive results. The material is attractive because it is natural, biodegradable, and possesses a low carbon footprint compared to the conventional reagents. A mixed sulphide ore deposit in Halkidiki, Greece, is operated by Hellas Gold S.A., a subsidiary of Eldorado Gold. The company produces galena (PbS), sphalerite (ZnS) and Au bearing pyrite/arsenopyrite (FeS₂/FeAsS) concentrates by applying consecutive froth flotation stages. Our previous laboratory studies have shown that the partial substitution of sodium isopropyl xanthate (SIPX) with OLN is possible, without worsening the flotation performance or downgrading the concentrates’ quality. This study presents the findings of 3-stage pilot-scale flotation tests using OLN as a partial substituent of the SIPX collector on sphalerite and pyrite/arsenopyrite circuits. In the sphalerite recovery circuit, the partial replacement of SIPX with OLN (25 and 50%) resulted in an increase in Zn grade and a similar recovery compared to the standard case, while better selectivity was achieved since the Au recovery in the Zn concentrate was lower. Similarly, with the pyrite/arsenopyrite flotation circuit, the replacement of SIPX with OLN resulted in an increase in gold recovery with a parallel reduction in Pb recovery. It appears that OLN can efficiently replace part of the SIPX collector in Zn and Au flotation, producing concentrates of similar to better purity, in terms of grade and recovery of valuable metals, because of the improved selectivity of the mixed collector. The introduction of OLN in the collector mixture and the parallel reduction of SIPX drastically reduce the environmental footprint of the process. Full article

Timely and accurate detection of diseases plays a significant role in attaining optimal growing conditions of olive crops. This study evaluated the use of two machine learning algorithms, Random Forest (RF) and XGBoost (XGB), in conjunction with the feature selection methods Recursive Feature Elimination (RFE) and Mutual Information (MI), for detecting stress in olive trees using hyperspectral data. The research was conducted in Halkidiki, Northern Greece, and focused on identifying stress caused by biotic and abiotic factors through the analysis of hyperspectral images. Both the RF and XGB algorithms demonstrated high efficacy in stress classification, achieving roc-auc scores of 0.977 and 0.955, respectively. The study also highlighted the effectiveness of RFE and MI in optimizing the classification process, with RF and XGB requiring a reduced number of hyperspectral features for an optimal performance of 1.00 on both occasions. Key wavelengths indicative of stress were identified in the visible to near-infrared spectrum, suggesting their strong correlation with olive tree stress. These findings contribute to precision agriculture by demonstrating the viability of using machine learning for stress detection in olive trees, and underscores the importance of feature selection in improving classifier performance. Full article

One of the main crops cultivated in Greece is the olive tree. In recent years, olives around the Mediterranean Basin and especially in Greece have been facing increasingly high temperatures and are more often exposed to water deficits, inducing severe abiotic stress, thus affecting plant physiology and productivity. Future projections point to a general increase in temperature of up to 2 °C. Precipitation is projected to decrease in northwestern Halkidiki, leading to enhanced water needs and resulting in a possible decrease in yield. The increase in temperature, especially in the winter season, seems to impact flowering buds. The small number of days with low temperatures resulting in reduced flowering during spring will decrease the quantity and quality of olives and oil. Full article

A synoptic study of the supercell of 10 July 2019, Halkidiki, Greece, shows that the gradual approach of a cold front from the north and a short-wave trough from the WSW brought into juxtaposition Saharan and polar air masses, creating a dynamical and thermodynamical environment favourable for severe convection. Full article

Analysis of table olives microbiome using next-generation sequencing has enriched the available information about the microbial community composition of this popular fermented food. In this study, 16S and 18S rRNA sequencing was performed on table olives of five Greek popular cultivars, Halkidikis, Thassou, Kalamon, Amfissis, and Konservolia, fermented either by Greek style (in brine or salt-drying) or by Spanish style, in order to evaluate their microbial communities. Moreover, analytical methods were used to evaluate their biochemical properties. The prevailing bacterial species of all olives belonged to Lactobacillaceae, Leuconostocaceae, and Erwiniaceae families, while the most abundant yeasts were of the Pichiaceae family. Principal coordinates analysis showed a clustering of samples cured by salt-drying and of samples stored in brine, regardless of their cultivar. The biochemical evaluation of total phenol content, antioxidant activity, hydroxytyrosol, oleuropein, oleocanthal, and oleacein showed that salt-dried olives had low amounts of hydroxytyrosol, while Spanish-style green olives had the highest amounts of oleocanthal. All the other values exhibited various patterns, implying that more than one factor affects the biochemical identity of the final product. The protocols applied in this study can provide useful insights for the final product, both for the producers and the consumers. Full article

High-resolution pollen analysis of a sediment core recovered from Paliouras lagoon (Greece) allowed us to reconstruct the environmental dynamics of the Halkidiki peninsula during the last 4000 years. Palynological results have been interpreted and compared with detailed historical data, showing distinct phases of human-landscape interactions from the Bronze Age until recent times. Pollen spectra revealed an environment characterized by Mediterranean vegetation, mixed deciduous forest, and pine stands from the Late Bronze Age until the 11th century CE. The first signs of human impact were attested during the Archaic period with the cultivation of Olea, Castanea, and Vitis in the inland of the study area. An intensive land management was highlighted by arboriculture and cereal cultivation (Secale and Hordeum group) in Roman times. Late Antique-Early Medieval times coincided with less human pressure due to warfare-related crises, leading to the expansion of the forest and the abandonment of fields colonized by Amaranthaceae. A massive increase in pastoral activities, suggested by the high percentages of Cichorieae during the Ottoman period, is possibly linked to the significant demographic growth of the nearby city of Thessaloniki in the 16th century CE. Full article

Olives are an essential crop for Greece and constitute a major economic and agricultural factor. Diseases, pests, and environmental conditions are all factors that can deteriorate the health status of olive crops by causing plant stress. Researchers can utilize remote sensing to assist their actions in detecting these sources of stress and act accordingly. In this experiment, Sentinel-2 data were used to create vegetation indices for commercial olive fields in Halkidiki, Northern Greece. Twelve machine learning algorithms were tested to determine which type would be the most efficient to detect plant stress in olive trees. In parallel, a test was conducted by testing 26 thresholds to determine how setting different thresholds for stress incidence affects model performance and which threshold constitutes the best choice for more accurate classification. The results show that among all tested classification algorithms, the quadratic discriminant analysis provided the best performance of 0.99. The stress incidence threshold used in the current case to generate the best-performing model was 6%, but the results suggest that setting customized thresholds relevant to specific cases would provide optimal results. The best-performing model was used in a one-vs.-rest multiclass classification task to determine the source of the stress between four possible classes: “healthy”, “verticillium”, “spilocaea”, and “unidentified”. The multiclass model was more accurate in detection for the “healthy” class (0.99); the “verticillium” and “unidentified” classes were less accurate (0.76); and “spilocaea” had the lowest score (0.72). Findings from this research can be used by experts as a service to enhance their decision-making and support the application of efficient strategies in the field of precision crop protection. Full article

In every mine in the world, the result of the process is a slurry material called tailings. Today, more than ever before, the mining industry is looking for technical solutions to dewater mine tailings to eliminate the risk of tailings dam failures. In the Kassandra Mines in NE Chalkidiki, the Kokkinolakas Tailings Management Facility (KTMF) is currently in operation as a “dry stack” disposal area, by incorporating materials generated from the removal, cleaning, and rehabilitation of every old, non-operating tailings area from the extended past mining activities (1960–1995) as well as the tailings and wastes produced from the operations of the Olympias and Stratoni mines. Recently, the Kassandra Mines was also permitted to use the same dry stack technology at the Skouries project, providing the huge benefit for the environment of the full release of the Lotsaniko valley. Full article

The area of the old arsenopyrites concentrate storage area is located at the Olympias Mining Facilities. The area was formed in the 1970s as a temporary storage area for the produced concentrate of gold-bearing arsenopyrite of Olympias. The total area is 11 hectares, and in the 1980s, the concentrate was removed from the site and arsenopyrite residues, which remained on the deforested surface, were major sources of pollution of the surface and ground waters of the wider area. The remediation and restoration works of this area were initiated by Hellas Gold as a priority immediately after taking over the Kassandra Mines property. After the restoration of the area, a nursery was installed with more than 1,000,000 plants. Full article

A Knowledge, Attitudes and Practices (KAP) study was conducted at the end of May 2021 engaging 1456 healthcare workers (HCWs) from 20 hospitals throughout Greece. Acceptance of vaccination against coronavirus disease 2019 (COVID-19) was estimated at 77.7%, with lower vaccine acceptance identified in nurses compared to physicians. Fears related to vaccine safety, lack of information and general knowledge about vaccinations, influenza vaccine acceptance, education level and years of practice were among the factors independently associated with vaccine acceptance. A strong association was identified between vaccination of HCWs in each health region and the population coverage, indicating that HCWs may be role models for the general population. Information campaigns should continue despite decisions taken regarding mandatory vaccinations. Full article

The market demand for interesting varieties and cultivars of Ilex aquifolium necessitates the exploration and sustainable exploitation of plant individuals thriving in nature without human care. In this work, an effort was made to develop a simple and reliable protocol for vegetative propagation of I. aquifolium plants, with desirable-for-market characteristics, grown in a mountain area of Halkidiki, Greece, and at the same time to proceed with their genetic identification using molecular markers. From these plants, new plants were vegetatively produced which afterward were used as stock plants for providing the needed shoot cuttings for the experiments of rooting and leaves for their genetic analysis. Factors studied in formulating a propagation protocol included the season of cutting collection and the application of 0.2% 1-naphthaleneacetic acid (NAA), as well as the type of shoot cuttings (terminal, subterminal) and the application of auxin. It was found that application of NAA was crucial for rooting response and number of roots formed, whereas the season effect was not significant on rooting. Terminal cuttings treated with 0.2% NAA exhibited the highest rooting percentage (100%) and formed abundant roots (25.7) compared to subterminal ones. All rooted cuttings, after being potted and transferred to acclimatization greenhouse, were successfully hardened. In the spring of the next year, the produced plants blossomed abundantly and formed fruits (bright red berries) presenting their characteristic ornamental appearance that was maintained until Christmas. For the identification procedure, the genotypic profile of the stock plants was also investigated by inter-simple sequence repeat (ISSR) genetic analysis, revealing that they were genetically the same both among themselves and when compared with a certified I. aquifolium ‘Agrifoglio Commune’ individual, but they differed genetically from I. aquifolium ‘Argentea Marginata’ and I. aquifolium ‘Hellas’. Full article

Table olives represent one of the most important fermented products in Greece. Their highly appreciated flavor is directly associated with the volatile composition. However, extensive data on the volatile profile of table olives from Greek cultivars are scarce in the literature. For this reason, the volatile components of industrially fermented table olives from Kalamata, Conservolea and Halkidiki cultivars grown in different geographical areas within Greece were determined using headspace solid-phase microextraction combined with gas chromatography–mass spectrometry. More than 100 volatile compounds were identified and distributed over different chemical classes. All samples were rich in esters, alcohols and acids, whereas the samples of cv. Halkidiki were also characterized by increased levels of volatile phenols. Both qualitative and quantitative differences were observed, which resulted in the discrimination of the table olives according to olive cultivar and growing location. To the best of our knowledge, this is the first systematic study on the volatile profiles of table olives from Greek cultivars that also highlights the pronounced effect of olives’ growing location. Full article

Olives are characterized by a wide variety of volatile compounds, which are primarily products of microbial metabolism that contribute to the organoleptic characteristics of the final product and especially to its flavor. The volatilome in Spanish-style processed green olives of Conservolea and Halkidiki cultivars were analytically characterized. A solid phase micro-extraction (SPME) technique was used for the extraction of volatile components from the olive samples that were further identified and quantified by gas chromatography coupled to mass spectrometry (GC–MS). Eighty-eight (88) compounds were identified, including several aldehydes, ketones, acids, terpenes, but mainly esters and alcohols. Results showed that there were no significant differences in the qualitative composition of the volatile profiles between the two varieties. Acetic and propanoic acids, thymol, ethanol, 2-butanol, 1-propanol, ethyl acetate as well as ethyl propanoate were the most dominant compounds found in both cultivars. However, some quantitative differences were spotted between the two varieties regarding some of the identified volatile compounds. The quantity of 2-butanol was higher in the Halkidiki variety, while propanoic acid ethyl ester was found in higher amounts in the Conservolea variety. Furthermore, differences in the quantities of some volatile compounds over time were observed. Most of the identified compounds presented an increasing trend during storage. Full article

Spanish-style green olives are among the main trade preparations in the international market. The purpose of this work was to investigate the effect of the modified atmosphere packaging of Spanish-style green olives in multi-layered pouches on the microbiological and physicochemical characteristics of olives. Green pitted olives of cv. Conservolea and Halkidiki were packaged in high-barrier multi-layered pouches under modified atmospheres and stored at room temperature for 12 months. Microbiological (lactic acid bacteria (LAB), yeasts, and Enterobacteriaceae) and physicochemical changes (pH, acidity, salt content, texture and color) were monitored throughout storage together with sensory assessment. Results showed that the initial microbiota consisted of LAB (5.9–6.3 log CFU/g) and yeasts (4.8–5.3 log CFU/g). Yeasts started to decline and could not be detected after 90 days of storage. In the end, LAB dominated in populations exceeding 5.4 and 6.1 log CFU/g for cv. Halkidiki and Conservolea, respectively. No Enterobacteriaceae could be detected in both olive varieties. In addition, pH values increased gradually from 3.51 to 4.19, the mean acidity was ca. 0.2% (expressed as lactic acid) and the salt content fluctuated between 2.0–4.4%. Color parameters L* (luminance), a* (greenness/redness) and b* (yellowness/blueness) did not change during storage in both varieties. Texture analysis showed a decrease in olive hardness from 15–20 N to 8 N throughout storage. Sensory analysis revealed that cv. Halkidiki olives were crisper with increased fibrousness compared to cv. Conservolea. Full article