Papers by Ierotheos Zacharias
Lakes and Reservoirs: Research and Management, 2002
The Institute of Inland Waters in Greece has investigated the physical, chemical and biological c... more The Institute of Inland Waters in Greece has investigated the physical, chemical and biological characteristics of major Greek lakes, with regard to water use, quality and trophic status. Based on this and other limnological investigations, Greek lakes can be divided into three ...
Annales De Limnologie-international Journal of Limnology, 2006
The project "Water Saving for Development (WaS4D)" is financed by European Territorial ... more The project "Water Saving for Development (WaS4D)" is financed by European Territorial Cooperational Programme, Greece-Italy 2007-2013, and aims at developing issues on water saving related to improvement of individual behaviors and implementing innovative actions and facilities in order to harmonize policies and start concrete actions for a sustainable water management, making also people and stakeholders awake to water as a vital resource, strategic for quality of life and territory competitiveness. Drinkable water saving culture & behavior, limited water resources, water supply optimization, water resources and demand management, water e-service & educational e-tools are the key words of WaS4D. In this frame the project objectives are: • Definition of water need for domestic and other than domestic purposes: regional and territorial hydro-balance; • promotion of locally available resources not currently being used - water recycling or reuse and rainwater harvesting; • s...
Applied Surface Science, 2015
ABSTRACT The main objective of this study is to investigate the adsorption process from both expe... more ABSTRACT The main objective of this study is to investigate the adsorption process from both experimental and modeling point of view of phosphate onto PhoslockTM4 , an increasingly used worldwide restoration tool to control phosphorus from natural water ecosystems. Bench-scale batch experiments were performed to examine its efficiency as a phosphate adsorbent and detailed simulations were carried out, allowing for a deep insight of the removal process. The adsorption efficiency calculated by the simulations is 87.41%, being in excellent agreement with that experimentally measured (approx. 87%). However, it is important to notice the discrepancy between experimental measures and simulation estimates. Although the agreement is perfect for T = 25 oC, it becomes more and more poor as temperature decreases, approaching approx. 10 % difference for the low temperature of 10 o C. This inconsistency between experiments and model can be attributed to the internal inefficiencies of unit cell approach, which in particular overestimates the adsorption efficiency.
Desalination and Water Treatment, 2015
The environmental problem of anoxia has become common nowadays, as its frequency of occurrence in... more The environmental problem of anoxia has become common nowadays, as its frequency of occurrence increases daily. In general, geomorphology and circulation patterns are the two important factors which make marine systems prone to anoxia. The main features which lead to the development of anoxia in coastal areas are the eutrophication, the low physical energy and the large freshwater input. The combination of them form stratified water masses that become anoxic when they are isolated. The case study region Amvrakikos Gulf (Western Greece), one of the most important protected wetland in Greece and in Europe. In order to determine the trophic state of the Gulf, as well as the environmental state in reference to the dissolved oxygen conditions, and finally to compare them with previous measurements in the past (1987), physicochemical characteristics of water column were measured at sixteen stations, at four different seasons during 2009-2010. Simultaneously, water samples, from different ...
Physics and Chemistry of the Earth, Part B: Hydrology, Oceans and Atmosphere, 2000
In the arid areas of the European Union there exist locations in which there is scarcity of water... more In the arid areas of the European Union there exist locations in which there is scarcity of water relative to the demand and the water demand has substantial temporal variations, rising during the summer many times over the annual average. Locales where such conditions exist ...
Environmental Modelling & Software, 1997
and eventual management of lakes depends upon iterative interactions between model-guided measure... more and eventual management of lakes depends upon iterative interactions between model-guided measurements and measurement-tested model development.
Biologia, 2008
The investigation of the zooplankton community in the upstream part of Stratos reservoir during a... more The investigation of the zooplankton community in the upstream part of Stratos reservoir during a 24 months survey (September 2004–August 2006) revealed 26 invertebrate species (14 rotifers, 6 cladocerans, 5 copepods and one mollusk larva). The mean abundance of the total zooplankton was higher in the first sampling period (2004–2005) and ranged between 8.81 and 47.74 ind. L−1, than the second period (2005–2006) when fluctuated between 1.91 and 43.09 ind. L−1. The seasonal variation was strongly influenced by the presence of rotifers, which accounting on average for 68.4% in total. Among them Keratella cochlearis and the order Bdelloidea were numerically the most important, while Macrocyclops albidus prevailed among the copepods and Bosmina longirostris among the cladocerans. Dreissena polymorpha was the only mollusk found in the zooplankton community. Rotifers, copepods and cladocerans showed a seasonal succession with the former preceding in the abundance having their first maximum in spring, while copepods and cladocerans followed, having peaks of abundance in early summer and in autumn, respectively. No seasonal succession among the cladoceran species was observed. The intense water flow in the upstream part of the reservoir, as well as temperature, conductivity, DO, pH, phosphates and silicates, were significant parameters controlling abiotic and biotic elements of the ecosystem and consequently influencing the seasonal variation and the dynamics of the zooplankton community.
A modified inorganic bentonite (Zenith/Fe) based on natural bentonite with the code name Zenith-N... more A modified inorganic bentonite (Zenith/Fe) based on natural bentonite with the code name Zenith-N, was prepared by embedding Fe ions in the interlayer space of bentonite. Bench-scale batch experiments were performed to examine its efficiency as an adsorbent for phosphate removal from natural waters. Phosphate uptake was evaluated vs. pH using adsorption kinetics and adsorption isotherms. The effects of temperature and salinity (fresh, brackish and marine waters) on phosphate-uptake capacity were also investigated. Comparative experiments were carried out for unmodified bentonite (Zenith-N) and a commercial product Phoslock (lanthanum modified clay). The results showed that phosphate-uptake capacity of Zenith/Fe [11.15 mg/g, at pH = 7] was improved by~350% compared to unmodified bentonite (Zenith-N) [4.12 mg/g, at pH = 7] and was comparable to the phosphate-uptake capacity of Phoslock [11.60 mg/g]. The optimal pH for phosphate adsorption ranged between 6 and 7. However, phosphate adsorption by Zenith/Fe and Phoslock appeared to be less pH-dependent than natural bentonite. Adsorption kinetics showed that over 80% of phosphate was removed from water within 1 h. The resulting isotherms also fit well with Langmuir and Freundlich isotherm models. The increase in adsorption capacity of Zenith/Fe at higher temperatures was caused by the enlargement of pore size and/or activation of the adsorbent surface. Finally, the phosphate adsorption capacity followed the order: fresh water b brackish b marine water.
Journal of Marine Systems, 2014
ABSTRACT In this paper we study the hypoxia dynamics in a fjord-like gulf, the Amvrakikos Gulf, i... more ABSTRACT In this paper we study the hypoxia dynamics in a fjord-like gulf, the Amvrakikos Gulf, in the Mediterranean Sea and highlight the factors which control the development of hypoxia. Bimonthly physicochemical data were collected in order to describe the hypoxic conditions and a three-dimensional model was used to describe the hydrodynamic circulation and explain the variations in hypoxic conditions. According to our results, the horizontal intrusion of well oxygenated open seawater can lead to the oxygenation of the deepest water in this semi-enclosed gulf. The key factor in determining the success of this horizontal intrusion is the density difference between the gulf's deepest area and the open sea outside the gulf. When the well oxygenated open seawater is denser than the bottom water in the gulf, it inflows into the gulf near the bottom and slowly re-oxygenates the isolated deep waters through mixing and diffusion, as the water travels eastward. However, when the gulf's deep water is denser than the open sea's water, the inflow stops. This, in combination with the eutrophic conditions which characterize the Amvrakikos, causes the re-establishment of hypoxic/anoxic conditions.
Hydrological Processes, 2015
The Science of the total environment, Jan 15, 2014
Eutrophication has become the primary water quality issue for most of the freshwater and coastal ... more Eutrophication has become the primary water quality issue for most of the freshwater and coastal marine ecosystems in the world. It is one of the most visible examples of biosphere's alteration due to human activities affecting aquatic ecosystems from the Arctic to the Antarctic. As eutrophication becomes frequent and many eutrophic ecosystems have difficulties meeting the EU Water Framework Directive (WFD) criteria the removal of phosphate and/or ammonium gains great importance, in water treatment. The objective of this paper is to review the restoration methods of eutrophic ecosystems, emphasizing remediation methods of internal nutrient release budget as a major factor to control eutrophication. The use of phosphate inactivation agents as a restoration tool, their capacity and application methods, as well as the individual results (in water quality, algal blooms, flora and fauna) in areas that have been implemented were also examined. Moreover, a conceptual model was conducte...
Estuarine, Coastal and Shelf Science, 2011
Coastal hypoxia and anoxia have become a serious environmental problem in many coastal ecosystems... more Coastal hypoxia and anoxia have become a serious environmental problem in many coastal ecosystems, and recent evidence suggests an increase in the number of systems experiencing hypoxia globally and an increased frequency and duration of hypoxia in many historically hypoxic systems. Eutrophication, low physical energy and large freshwater input are some of the most important factors, which lead to the development of hypoxia in coastal areas. The Amvrakikos Gulf, located in western Greece, is one of the most important protected areas in Greece and in Europe and past studies indicated that some regions of the Gulf experience hypoxia. Despite the importance of the Amvrakikos Gulf ecosystem, little is known about key ecological, chemical, and physical processes in the Gulf and their relationship with oxygen depletion. In the present study, authors try to answer some important questions regarding the distribution and variation of the hypoxic zone. After a year of measurements, it was concluded that according to spatial distribution of DO, the gulf can be divided into two parts, the western and eastern areas, with important differences occurring between them. Within the western area, the water column was well oxygenated during winter and spring and hypoxic conditions occurred only in summer and autumn. The eastern area was hypoxic throughout the year and anoxic conditions occurred only during autumn. In conclusion, taking into account the author's measurements and previous studies, the seasonally hypoxic eastern area in 1987 converted into a seasonally anoxic area in 2009 and the western part of the gulf, remained seasonally hypoxic, indicating the degradation of the gulf's environmental state within the last 20 years.
Desalination and Water Treatment, 2013
ABSTRACT The environmental state of estuaries is often compromised by various processes with dire... more ABSTRACT The environmental state of estuaries is often compromised by various processes with direct and indirect ecological impacts such as eutrophication, harmful algal blooms, trophic interactions, and so on. In this paper, the eutrophication state of an important semi-enclosed embayment, the Amvrakikos Gulf, in Western Greece, for the first time will be examined, and the present situation will be compared with previous measurements. Field data used in this study were collected during four sampling cruises (April 2009 to March 2010) in the Amvrakikos Gulf. In compliance with the results, both the rivers’ high discharges and the high evaporation rate lead to strong stratification of the water column throughout the year due to either salinity or temperature fluctuations. In combination with the limited communication with the open sea, this has resulted in different spatial and temporal dissolved oxygen distributions, as the western part of the gulf is seasonally hypoxic, while the eastern part is seasonally anoxic. The use of fertilizers, the load from fish farming, the phosphate geological layers, and other point and nonpoint source pollutions increase the nutrient pollution of the Amvrakikos Gulf. As a consequence, according to Carlson’s trophic state index, the Amvrakikos Gulf varies from mesotrophic to eutrophic.
Applied Numerical Analysis & Computational Mathematics, 2005
Hydrodynamic numerical models nowadays offer great aid when studying the physical behavior of coa... more Hydrodynamic numerical models nowadays offer great aid when studying the physical behavior of coastal waters. However, the calibration and furthermore the verification of such models, is a difficult process that should be applied carefully, especially when little direct hydrodynamic data has been collected from the study area. This paper suggests a methodology for indirect verification of mathematical coastal circulation models, by means of image processing and interpretation of Landsat's TM reflective bands 3 and 6 imagery. This approach is an efficient practice and is easily available even though no field survey was carried out. This method was successfully applied to Saronikos Gulf and in particular to gulf of Megara, located westwards of Salamis Island, where the dispersion of a plume formed by urban waste waters was examined. The satellite data processing derivatives were found to be in accordance with the results of the circulation simulation and thus the parameters used for the calibration of the model can be considered successfully selected.
Mediterranean temporary ponds (MTPs) is a priority habitat according to the Natura 2000 network o... more Mediterranean temporary ponds (MTPs) is a priority habitat according to the Natura 2000 network of the European Union (Natura code 3170, Habitats Directive 92/43/ EEC) and is located in various Mediterranean countries. Priority habitats are those habitattypes or elements with a unique or important significance to a diverse group of species. They consist of a unique flora composition, succession stage and/or structural factor. Increased urbanisation and agriculture in addition to climate change, in the Mediterranean region, has led to the extinction of a very large number of temporary ponds. This paper is a review of the value and the numerous threats, concerning MTPs. Protection and conservation of the ponds is very important and appropriate managerial measures should be immediately taken, to save such a vulnerable ecosystem.
A novel composite material was prepared by embedding Fe, Cu and HA into bentonite. Batch experime... more A novel composite material was prepared by embedding Fe, Cu and HA into bentonite. Batch experiments studied its efficiency as adsorbent of PO À3 4 and NH þ 4 . Adsorption isotherms, kinetics, pH, temperature and salinity effect, were examined. Bephos™ is very effective under a wide range of physicochemical conditions. Bephos™ exhibits higher adsorption than other materials from the literature.
Hydrobiologia, Feb 27, 2010
This study explores the past, present and future ecological changes in the highest Mediterranean ... more This study explores the past, present and future ecological changes in the highest Mediterranean temporary pond (Omalos pond) in western Crete, Greece. Data from downcore pollen analysis (including pollen and spores from both aquatic vegetation, and terrestrial herbaceous, arboreal and shrub vegetation), modern vegetation monitoring and existing climate scenarios have been combined to provide a picture of the ecological changes in the pond over the last 13,600 years. Downcore pollen analysis throughout the last 13,600 years indicated the presence of species typical of Mediterranean Temporary Pond (MTP) habitats and suggested relatively drier conditions towards the present. The low number of non-native, cultivated species (such as herbaceous Trifolium and Plantago species) observed over this period suggested relatively low impact from crop agriculture, despite the increasing grazing pressure in the area. In the absence of independent proxies, we cannot reliably distinguish between natural and human-induced changes. The presence of aquatic Isoetes in the palaeo-record indicates the existence of an ephemeral pond in the area as early as the beginning of the Holocene suggesting resilience of the ecosystem over time. However, the degraded state of pollen in depths over 55 cm (i.e. 3600 year BP) increases the uncertainty of the interpretation. Currently, the pond holds 76 plant species belonging to 25 families. Therophytes and chamaephytes were the most frequent, suggesting a typical ephemeral habitat life form spectrum. Species richness was found to increase during spring surveys whereas the highest turnover was observed between summer surveys of consecutive years. Cluster analysis demonstrated a distinct zonation in four vegetation belts from the periphery to the centre of the pond which is typical of these environments. Modelling, based on two IPPC scenarios (A2 and B2), predicted relatively low climate change impacts on the pond's hydroperiod for the next 100 years (i.e. a decrease of 16 and 24 days, respectively). This reduction in the hydroperiod of the pond will have an effect on the physiognomy and spatial extent of vegetation,
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Papers by Ierotheos Zacharias