Iraklis Panagiotakis

Origin and concentration profile of chromium in a Greek aquifer

In this paper the origin and concentration of chromium (Cr) in an ophiolitic aquifer in Vergina, northern Greece were investigated. The study area has only agricultural activity so that industrial Cr contamination was precluded. Soil sampling included topsoil and drillcore samples collected down to 98 m depth. Groundwater samples were collected from three existing wells and a spring at the area and from different depths of the soil boring using the discrete sampling method. Mineralogical analysis of soils confirmed the presence of ultramafic minerals, including chrysotile and chromite. Soil elemental analysis showed significant concentration of total chromium (Crtot; max 12,000 mg/kg) and hexavalent chromium (Cr(VI); max 7.5mg/kg). Significant Crtot (91 μg/L) and Cr(VI) (64 μg/L) concentrations exceeding the drinking water limit of 50 μg/L were also detected in groundwater. In both the discrete soil and groundwater samples a decreasing trend of Cr(VI) concentration was observed with increasing depth, while Crtot increased. The increasing trend in Crtot is attributed to the increasing contribution of unweathered ultramafic minerals with depth, while the decreasing Cr(VI) may be related to the increasing soil pH that does not favor Cr(III) oxidation by Mn-oxides.

Forensic investigation of a chromium(VI) groundwater plume in Thiva, Greece

A forensic investigation was conducted with the aim of decoupling the contribution of geogenic and anthropogenic Cr(VI) sources in the wider area of Thiva. Groundwater and topsoil samples were collected from two Cr(VI) groundwater plumes of 160 μg/L and 75 μg/L. A series of evidence support the view that the origin of Cr(VI) detected in groundwater is mainly geogenic. These are: (a) the presence of Cr in topsoil of the wider area, (b) the moderate Cr(VI) groundwater concentrations, (c) the high Ni levels within the Cr(VI) plumes, (d) the predominance of Mn(IV), which is a prerequisite for Cr(III) oxidation to Cr(VI), and (e) the absence of co-contaminants. The present study also revealed that, although both Cr(VI) plumes are clearly of geogenic origin, the plume with the elevated Cr(VI) values, in the north of Thiva town, exhibits also an anthropogenic component, which can potentially be attributed to the alkaline environment associated with the old uncontrolled landfill of Thiva and the industrial cluster located in this area.

Groundwater Modeling and Remediation Scenarios of a Hexavalent Chromium Plume Released from an Industrial Site

In recent years, high concentrations of hexavalent chromium [Cr(VI)] have been found in the groundwater system of the Asopos River Basin. This work focuses on a Cr(VI) plume detected in the industrial area of Inofyta, the most important contamination hot spot of the Asopos River Basin. A groundwater flow and Cr(VI) transport model was developed to assess the behaviour of the plume and investigate the location of a suspected nearby source zone. According to the model results, the suspected source zone location is highly probable and the Cr(VI) plume does not migrate significantly. Based on the above findings, it is believed that the remediation effort could potentially be very effective in the area, if the remediation plan is designed properly. In order to assess the remediation potential of (a) natural attenuation and (b) polyphenol-coated nZVI treatment, two model scenarios were created and their results were compared and discussed.

Remediation of contaminated sites.

Remediation of contaminated sites is one of the most rapidly developing environmental restoration subjects. Site contamination results mostly from past and present anthropogenic activities and it presently constitutes one of the largest environmental liabilities for future generations to bear. The most significant categories of contaminants that are encountered in contaminated sites, typically as mixtures, are petroleum hydrocarbons, halogenated organic compounds, metals and metalloids, radionuclides, and explosives. The process of remediation of contaminated sites is a site-specific phased approach comprising site characterization, risk assessment and remediation technology selection and application. The high cost and complexity of the problem renders remediation of contaminated sites a real challenge for environmental professionals and society altogether, with far ranging implications on industrial, agricultural and other anthropogenic activities and practices in terms of pollution prevention, waste management and their overall sustainability. Although, this is not a new environmental issue, only when incidents such as the Love Canal site in New York and the Lekkerkerk site in the Netherlands were widely publicized in the 1970s, researchers around the globe started intensively studying the contaminated site problem. As a result thousands of contaminated sites have already been identified in most parts of the world, requiring hundreds of billions of US dollars to be remediated. The actual problem is even worse since very limited data are yet available for Eastern Europe, Africa, South America, and for key countries such as China and India. In the European Union (EU) alone the number of contaminated sites requiring remediation has been estimated as approximately 250,000 and the potential polluting activities have been expected to have occurred at nearly three million sites. Besides helping us comprehend the magnitude of the contaminated site problem, these numbers underline the significant lack of data for the EU and underscore the apparent differences in reporting among different geographical and other entities, both issues been applicable for the rest of the globe as well. Furthermore, taking into account the large numbers of known or estimated contaminated sites across the world and the huge budgets required for site remediation, the focus should be shifted on those contaminated sites that potentially pose the highest risks to humans and the environment. Thus, there still is a great need in applied research to fill in the aforementioned data gaps, in terms of both the magnitude and potential risk of site contamination and, more importantly, help develop the most cost-effective, yet scientifically sound and innovative, sustainable remediation approaches. This special issue of the Bulletin of Environmental Contamination and Toxicology hosts both selected papers from the conference session of the 13th International Conference on Environmental Science and Technology (http://cest2013.gnest.org/) that took place in Athens, Greece in September, 2013, and invited contributions from international researchers. This special issue aims not to cover the entire spectrum of this incredibly wide scientific area but present some interesting examples of research that is currently been carried out in several countries around the world on this subject. I. Panagiotakis (&) ENYDRON – Environmental Protection Services, 1 Ipirou str., 104 33 Athens, Greece e-mail: panagiotakis@enydron.com

Soil and Groundwater Contamination and Remediation

The next two studies investigate the effect of inadequate waste management practices to groundwater and soil quality. The first study by Kavvadias et al. investigates the extent in which the long-term disposal of olive mill wastewaters in evaporation ponds in Greece can affect the soil properties of the area located outside the evaporation pond, while Eze et al. investigate groundwater contamination following improper hospital wastes disposal in Nigeria. The next part of this special issue focuses on soil and groundwater contaminated with chromium (Cr). In particular, Dermatas et al. compare a site with geogenic Cr(VI) and a site with anthropogenic Cr(VI) and demonstrate how important is the origin of the contaminant for the remediation measures selected, while Dokou et al. develop a groundwater flow and Cr(VI) transport model for the same anthropogenic Cr(VI)-contaminated site. Molla et al. evaluate the removal of chromium from soils cultivated with maize using soil amendments, while Chrysochoou and Reeves study nanoremediation of Cr(VI)-contaminated groundwater using green tea solution and nano zero valent iron (nZVI). Another study investigating nanoremediation is that of Vilardi and Di Palma who, however, examine the nitrate removal by Cu–Fe nanoparticles and evaluate the optimal ratio between reductant and pollutant. Soil remediation is also studied by Mukhopadhyay et al. who investigate soil washing of arsenic from an iron rich soil using phosphate and colloidal gas aphrons generated from saponin extracted from Sapindus mukorossi fruit. The next two studies investigate contaminant transport through soil. The first is by Smilek et al. investigating the transport of organic compounds through porous systems containing humic acids and the second by Bourazanis et al. investigating chloride transport through the soil. This is a special issue dedicated to soil and groundwater contamination and remediation. Most of the studies included herein were presented in the 14th International Conference on Environmental Science and Technology (http://cest2015.gnest.org/) that took place in Rhodes Island, Greece in September, 2015. This special issue also hosts studies by other researchers working in this field. Similar to the first special issue (2015), the current special issue does not focus on a specific part of this topic but presents a wide range of different research studies highlighting the topic’s diversity and complexity. The first part of the special issue hosts studies investigating contamination and remediation in mining sites. In particular, Erdemir et al. evaluate the elemental composition of plant species spread around an abandoned tungsten mining area in Turkey, while Rojo et al. analyze the electrical behavior of tailings in Electro-Kinetic Remediation experiments. Tamburini et al. focus on developing a bioaugmentation-assisted phytostabilization technology based on autochthonous plant species and plant growth promoting bacteria from an abandoned mining area in Italy, which constituted one of the most important mining districts for Pb and Zn extraction. A study investigating also phytoremediation is that of Lai et al., who examine the suitable breeding conditions of Impatiens walleriana, which is a potential cadmium (Cd) hyperaccumulator.

Effects of different electron donor feeding patterns on TCE reductive dechlorination performance.

Abstract This study investigates how the feeding pattern of e− donors might affect the efficiency of enhanced in situ bioremediation in TCE-contaminated aquifers. A series of lab-scale batch experiments were conducted using butyrate or hydrogen gas (H2) as e− donor and a TCE-dechlorinating microbial consortium dominated by Dehalococcoides spp. The results of these experiments demonstrate that butyrate is similarly efficient for TCE dechlorination whether it is injected once or in doses. Moreover, the present work indicates that the addition of butyrate in great excess cannot be avoided, since it most likely provide, even indirectly, significant part of the H2 required. Furthermore, methanogenesis appears to be the major ultimate e− accepting process in all experiments, regardless the e− donor used and the feeding pattern. Finally, the timing of injection of H2 seems to significantly affect dechlorination performance, since the injection during the early stages improves VC-to-ETH dechlorination and reduce methanogenic activity.

Nano-Zero-Valent Iron: An Emerging Technology for Contaminated Site Remediation

Soil contamination is by definition a very complex and expensive problem to solve, because a three-phase medium is contaminated by chemicals, commonly as mixtures, which not only interact together but also with each phase of the soil concurrently. Although pump-and-treat, monitored natural attenuation, and vertical engineered barriers are the most frequently applied groundwater treatment technologies for contaminated sites, new remediation technologies have appeared as emerging trends. The most promising among them is nanoremediation, a technology based on the injection of nanoparticles (NPs) into contaminated aquifers for transformation and detoxification of pollutants. The most widely NPs among them is nanoscale zero-valent iron (nZVI), which may be used for organic or inorganic contaminants such as heavy metals and especially hexavalent chromium (Cr(VI)). The present study aims at reviewing the current knowledge on Cr(VI) remediation by nZVI, focusing on the mechanisms by which Cr(VI) is treated by nZVI, the fate and transport of these NPs in the subsurface, the modifications of nZVI, and the removal efficiency that have been published. Finally, the potential toxicity created after the injection of nZVI particles in aquifers is also discussed.