Ariadne Argyraki

Urban soil geochemistry in Athens, Greece: The importance of local geology in controlling the distribution of potentially harmful trace elements

Understanding urban soil geochemistry is a challenging task because of the complicated layering of the urban landscape and the profound impact of large cities on the chemical dispersion of harmful trace elements. A systematic geochemical soil survey was performed across Greater Athens and Piraeus, Greece. Surface soil samples (0-10cm) were collected from 238 sampling sites on a regular 1×1km grid and were digested by a HNO3-HCl-HClO4-HF mixture. A combination of multivariate statistics and Geographical Information System approaches was applied for discriminating natural from anthropogenic sources using 4 major elements, 9 trace metals, and 2 metalloids. Based on these analyses the lack of heavy industry in Athens was demonstrated by the influence of geology on the local soil chemistry with this accounting for 49% of the variability in the major elements, as well as Cr, Ni, Co, and possibly As (median values of 102, 141, 16 and 24mg kg(-1) respectively). The contribution to soil chemistry of classical urban contaminants including Pb, Cu, Zn, Sn, Sb, and Cd (medians of 45, 39, 98, 3.6, 1.7 and 0.3mg kg(-1) respectively) was also observed; significant correlations were identified between concentrations and urbanization indicators, including vehicular traffic, urban land use, population density, and timing of urbanization. Analysis of soil heterogeneity and spatial variability of soil composition in the Greater Athens and Piraeus area provided a representation of the extent of anthropogenic modifications on natural element loadings. The concentrations of Ni, Cr, and As were relatively high compared to those in other cities around the world, and further investigation should characterize and evaluate their geochemical reactivity.

Multivariate statistics and spatial interpretation of geochemical data for assessing soil contamination by potentially toxic elements in the mining area of Stratoni, north Greece

A preliminary soil survey was undertaken in the mining region of Stratoni in Chalkidiki peninsula, north Greece. The objectives of the study were to assess the levels of soil contamination with respect to average concentrations of toxic elements in the region, to determine the associations between the different chemical elements and their spatial distribution, and to identify possible sources of contamination that can explain the spatial patterns of soil pollution in the area. Forty-nine surface soil samples were collected and analysed by inductively coupled plasma–atomic emission spectroscopy after digestion with a mixture of HClO4–HNO3– HCl–HF. The study focused on ten elements (Pb, Zn, Cu, As, Cd, Mn, Fe, Ni, Co, Cr), all of which were present in soil with concentrations well above the global soil means. Lead, As and Ni, with means of 895 μg g−1, 364 μg g−1 and 161 μg g−1 respectively, exceeded the tentative trigger concentration set by the Netherlands and the UK Interdepartmental Committee on the Redevelopment of Contaminated Land (ICRCL) regulations. Factor analysis explained 89% of the total variance of the data through four factors. Combined with spatial interpretation of its output, the method successfully grouped the elements according to their sources and provided evidence about their geogenic or anthropogenic origin.

Arsenic stress after the Proterozoic glaciations

Protection against arsenic damage in organisms positioned deep in the tree of life points to early evolutionary sensitization. Here, marine sedimentary records reveal a Proterozoic arsenic concentration patterned to glacial-interglacial ages. The low glacial and high interglacial sedimentary arsenic concentrations, suggest deteriorating habitable marine conditions may have coincided with atmospheric oxygen decline after ~2.1 billion years ago. A similar intensification of near continental margin sedimentary arsenic levels after the Cryogenian glaciations is also associated with amplified continental weathering. However, interpreted atmospheric oxygen increase at this time, suggests that the marine biosphere had widely adapted to the reorganization of global marine elemental cycles by glaciations. Such a glacially induced biogeochemical bridge would have produced physiologically robust communities that enabled increased oxygenation of the ocean-atmosphere system and the radiation of the complex Ediacaran-Cambrian life.

Assessing Lead, Nickel, and Zinc Pollution in Topsoil from a Historic Shooting Range Rehabilitated into a Public Urban Park

Soil contamination is a persistent problem in the world. The redevelopment of a site with a historical deposition of metals might conceal the threat of remaining pollution, especially when the site has become a public place. In this study, human health risk assessment is performed after defining the concentrations of Pb, Ni, and Zn in the topsoil of a former shooting range rehabilitated into a public park in the Municipality of Kesariani (Athens, Greece). A methodology that uses inductively coupled plasma mass spectrometry (ICP-MS, 13 samples), another that uses portable X-ray fluorescence (XRF) following a dense sample design (91 samples), and a hybrid approach that combines both, were used to obtain the concentrations of the trace elements. The enrichment factor and geoacummulation index were calculated to define the degree of pollution of the site. The hazard quotient and cancer risk indicators were also computed to find the risk to which the population is exposed. The present study reveals high non-carcinogenic health risk due to Pb pollution with ingestion as the main exposure pathway. The carcinogenic risk for Pb is within tolerable limits, but the definition of land use might alter such a statement. Lastly, regarding Ni and Zn, the site is unpolluted and there is insignificant carcinogenic and non-carcinogenic risks.

The Kallisti Limnes, carbon dioxide-accumulating subsea pools

Natural CO2 releases from shallow marine hydrothermal vents are assumed to mix into the water column, and not accumulate into stratified seafloor pools. We present newly discovered shallow subsea pools located within the Santorini volcanic caldera of the Southern Aegean Sea, Greece, that accumulate CO2 emissions from geologic reservoirs. This type of hydrothermal seafloor pool, containing highly concentrated CO2, provides direct evidence of shallow benthic CO2 accumulations originating from sub-seafloor releases. Samples taken from within these acidic pools are devoid of calcifying organisms, and channel structures among the pools indicate gravity driven flow, suggesting that seafloor release of CO2 at this site may preferentially impact benthic ecosystems. These naturally occurring seafloor pools may provide a diagnostic indicator of incipient volcanic activity and can serve as an analog for studying CO2 leakage and benthic accumulations from subsea carbon capture and storage sites.

Pilot-Scale Application of Attapulgitic Clay for Stabilization of Toxic Elements in Contaminated Soil

AbstractThis study presents an in situ pilot-scale application of attapulgitic clay for stabilization of toxic metals and metalloids in contaminated soil. The selected field for the pilot-scale experiment was heavily contaminated with toxic metals and metalloids in total (Cu: 122  mg/Kg, Pb: 6,610  mg/Kg, Zn: 3,630  mg/Kg, Cd: 26.3  mg/Kg, Ag: 9.4  mg/Kg, As: 802  mg/Kg, Mn: 1,435  mg/Kg, Ba: 304  mg/Kg, Sb: 95.3  mg/Kg) and leachable concentrations. Geochemical and physical properties of treated soil were thoroughly studied before and after mixing with the attapulgitic clay. Soil mineralogy was determined by X-ray diffraction (XRD) and scanning electron microsope (SEM) techniques. On the basis of the site-specific soil geochemical properties, an appropriate proportion of specific grain-size attapulgitic clay was added and mixed in situ with simultaneous adjustment of soil moisture content to reach saturation. Analytical data of amended soil samples collected 1 month after the application showed a signifi...

Modes of carbon fixation in an arsenic and CO2-rich shallow hydrothermal ecosystem

The seafloor sediments of Spathi Bay, Milos Island, Greece, are part of the largest arsenic-CO2-rich shallow submarine hydrothermal ecosystem on Earth. Here, white and brown deposits cap chemically distinct sediments with varying hydrothermal influence. All sediments contain abundant genes for autotrophic carbon fixation used in the Calvin-Benson-Bassham (CBB) and reverse tricaboxylic acid (rTCA) cycles. Both forms of RuBisCO, together with ATP citrate lyase genes in the rTCA cycle, increase with distance from the active hydrothermal centres and decrease with sediment depth. Clustering of RuBisCO Form II with a highly prevalent Zetaproteobacteria 16S rRNA gene density infers that iron-oxidizing bacteria contribute significantly to the sediment CBB cycle gene content. Three clusters form from different microbial guilds, each one encompassing one gene involved in CO2 fixation, aside from sulfate reduction. Our study suggests that the microbially mediated CBB cycle drives carbon fixation in the Spathi Bay sediments that are characterized by diffuse hydrothermal activity, high CO2, As emissions and chemically reduced fluids. This study highlights the breadth of conditions influencing the biogeochemistry in shallow CO2-rich hydrothermal systems and the importance of coupling highly specific process indicators to elucidate the complexity of carbon cycling in these ecosystems.

Characterization of phosphogypsum deposited in Schistos remediated waste site (Piraeus, Greece)

The operation of a phosphate fertilizer industry in Drapetsona, near Piraeus port (Greece), resulted in the deposition of 10 million tons of phosphogypsum (PG) into an old limestone quarry, in the period 1979-1989. The whole deposit has been recently remediated using geomembranes and thick soil cover with vegetation. The purpose of the present study was to characterize representative samples of that phosphogypsum, using diffraction (powder-XRD), microscopic (SEM-EDS), analytical (ICP-MS), and spectroscopic techniques (High-resolution γ-ray spectrometry and XRF). The material contains crystalline gypsum (CaSO4.2H2O) and Ca-Si-Al-S-F (chukhrovite-type/meniaylovite) phases. The natural radioactivity is mainly due to the 238U series and particularly 226Ra (average: 462 Bq/kg), which is relatively low compared to PG from the rest of the world. Furthermore, leaching experiments using local (Attica) rainwater, together with ICP-MS, were performed to assess the potential release of elements in the environment.

Factors controlling major ion and trace element content in surface water at Asprolakkas hydrological basin, NE Chalkidiki: Implications for elemental transport mechanisms

Chemical characteristics of stream water at Asprolakkas hydrological basin were determined in February 2009 in order to examine the main factors controlling the hydrogeochemistry of the drainage system. A total of 20 surface water samples were collected and analyzed for the major ions K, Na, Ca, Mg, HCO3, SO4 and the trace elements Fe, Pb, Zn, Mn, Cu, Ni, As, Sb, Mo and Ba. The application of R-mode factor analysis revealed that the polymetallic carbonate replacement type sulfide deposits, together with the porphyritic intrusions and the associated porphyry copper style mineralization, occurring in the studied area, impose fundamental control on the water chemistry. A third influencing factor includes the parameters As and HCO3 and is attributed to the competitive behavior of As and bicarbonate ions, for filling in available absorption space on Fe(III) oxides. SEM-EDS methods, performed on retained filters from the filtration of representative water samples, showed that Pb is mainly transported by fine particulate matter. The chemical elements Mn, Zn, Mo and Sb are predominantly present as dissolved free ions, and correlate strongly with the electrical conductivity of the water samples.

Inorganic Pollutants in Soils

Abstract Soil is a major reservoir for Potential Toxic Elements (PTEs). These PTEs can occur in various forms in soil and different bonding forces keep them bound to soil particles. The high concentrations, form and availability of PTEs in environment, can compromise the soil ecosystem and the growth of plants. At the end of the chain PTEs may entering in human body by direct (inhalation or ingestion of soil particles) or indirect (plant consumption) routes, which may cause physiological or metabolic disruptions. This chapter discusses the PTEs, their sources and implications for soils, and the methodologies used for monitoring such pollutants in soil. In addition, three case studies are presented: one related with agricultural Cu inputs in vineyard soils of Douro Region (Portugal) by its use as fungicide on grapes; another focused in urban soil pollution in Athens (Greece); and the last one related to a typical mining pollution case with As in Mexico.