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1.
Chemosphere ; 286(Pt 1): 131609, 2022 Jan.
Artículo en Inglés | MEDLINE | ID: mdl-34315074

RESUMEN

The systematic analysis of groundwater in the Greek island of Skiathos revealed a seasonal increase of total mercury concentrations after the extensive groundwater abstraction during the busy and heavily touristic summer months. This contamination was accompanied by a corresponding increase of the chloride content of groundwater, attributed to seawater intrusion into the freshwater-depleted aquifer within mercury-rich bedrock. The effects of elevated concentrations of chloride anions in the mobilization of mercury and its speciation were addressed by geochemical equilibrium modeling, considering cinnabar (HgS) as the mineral source of mercury. Adsorption onto hydrous ferric oxide (Fe2O3·H2O) was a necessary ingredient of the geochemical model for bringing the calculated concentrations in agreement with field measurements, after optimization of the cinnabar/adsorbent mass ratio to a value of 4.9 × 10-8. The speciation of mercury was found to depend on the acidity and redox status as well as on the chloride content of groundwater. Mercury concentrations in the groundwater of Skiathos rise above the World Health Organization limit of 1 µg L-1 for a seawater intrusion higher than 3 %, with HgCl2 being the dominant species followed by HgClOH, HgCl3- and HgCl42-. The assumed concentration of dissolved organic matter in groundwater had a negligible impact on the mercury speciation and its mobilization by chloride.


Asunto(s)
Agua Subterránea , Mercurio , Contaminantes Químicos del Agua , Monitoreo del Ambiente , Agua Dulce , Mercurio/análisis , Agua de Mar , Contaminantes Químicos del Agua/análisis
2.
Sci Total Environ ; 717: 137264, 2020 May 15.
Artículo en Inglés | MEDLINE | ID: mdl-32092809

RESUMEN

Achieving the UN Sustainable Development Goals depends on using resources efficiently, avoiding fragmentation in decision-making, recognising the trade-offs and synergies across sectors and adopting an integrated Nexus thinking among policymakers. Nexus Informatics develops the science of recognising and quantifying nexus interlinkages. Nexus-coherent solutions enhance the effect of policymaking in achieving adequate governance, leading to successful strategic vision and efficient resource management. In this article, we present the structure of a System Dynamics Model-the Nexus_SDM-that maps sector-specific data from major databases (e.g., EUROSTAT) and scenario models (e.g., E3ME-FTT OSeMOSYS and SWIM) for the national case study of Greece. Disaggregation algorithms are employed on annual national-scale data, turning them into detailed spatial and temporal datasets, by converting them to monthly values spread among all 14 River Basin Districts (RBDs). The Nexus_SDM calculates Nexus Interlinkage Factors and quantifies interlinkages among Water, Energy, Food, Built Environment, Natural Land and greenhouse gas (GHG) emissions. It simulates the nexus in the national case study of Greece as a holistic multi-sectoral system and provides insights into the vulnerability of resources to future socio-economic scenarios. It calculates the link between crop type/area, irrigation water and agricultural value, revealing which crops have the highest agricultural value with the least water and crop area. It demonstrates that fossil fuel power generation and use of oil for transportation are responsible for the most GHG emissions in most RBDs and presents projections for years 2030 and 2050. The analysis showcases that to move from a general nexus thinking to an operational nexus concept, it is important to focus on data availability and scale. Advanced Sankey and Chord diagrams are introduced to show distribution of resource use among RBDs and an innovative visualisation tool is developed, the Nexus Directional Chord plot, which reveals Nexus hotspots and strong interlinkages among sectors, facilitating stakeholder awareness.

3.
Ecotoxicol Environ Saf ; 143: 193-200, 2017 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-28550806

RESUMEN

This study investigated the microcystins (MCs)-rich irrigation water effect on lettuce of different developmental stages, i.e. during a two months period, covering the whole period from seed germination to harvest at marketable size of the plant. We followed four lettuce plant groups receiving MCs-rich water (1.81µgl-1 of dissolved MCs), originating from the Karla Reservoir, central Greece: 1) from seeds, 2) the cotyledon, 3) two true leaves and 4) four true leaves stages, all of which were compared to control plants that received tap water. Lettuce growth, photosynthetic performance, biochemical and mineral characteristics, as well as MCs accumulation in leaves, roots and soil were measured. The overall performance of lettuce at various developmental stages pointed to increased tolerance since growth showed minor alterations and non-enzymatic antioxidants remained unaffected. Plants receiving MCs-rich water from the seed stage exhibited higher photosynthetic capacity, chlorophylls and leaf nitrogen content. Nevertheless, considerable MCs accumulation in various plant tissues occurred. The earlier in their development lettuce plants started receiving MCs-rich water, the more MCs they accumulated: roots and leaves of plants exposed to MCs-rich water from seeds and cotyledons stage exhibited doubled MCs concentrations compared to respective tissues of the 4 Leaves group. Furthermore, roots accumulated significantly higher MCs amounts than leaves of the same plant group. Concerning human health risk, the Estimated Daily Intake values (EDI) of Seed and Cotyledon groups leaves exceeded Tolerable Daily Intake (TDI) by a factor of 6, while 2 Leaves and 4 Leaves groups exceeded TDI by a factor of 4.4 and 2.4 respectively. Our results indicate that irrigation of lettuce with MCs-rich water may constitute a serious public health risk, especially when contaminated water is received from the very early developmental stages (seed and cotyledon). Finally, results obtained for the tolerant lettuce indicate that MCs bioaccumulation in edible tissues is not necessarily coupled with phytotoxic effects.


Asunto(s)
Lechuga/efectos de los fármacos , Microcistinas/farmacocinética , Microcistinas/toxicidad , Contaminantes Químicos del Agua/farmacocinética , Contaminantes Químicos del Agua/toxicidad , Riego Agrícola , Grecia , Humanos , Lechuga/crecimiento & desarrollo , Lechuga/metabolismo , Fotosíntesis/efectos de los fármacos , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/crecimiento & desarrollo , Hojas de la Planta/metabolismo , Raíces de Plantas/efectos de los fármacos , Raíces de Plantas/crecimiento & desarrollo , Raíces de Plantas/metabolismo , Medición de Riesgo
4.
Water Res ; 38(14-15): 3362-72, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-15276753

RESUMEN

We present a series of modeling cases that illustrate the trends described by the unique features of the unified multiple-component cellular automaton (UMCCA) model for a heterogeneous, two-dimensional biofilm. The outputs of the UMCCA model show five general trends. (1) The concentration profiles for the two soluble microbial products are opposite the profile for original substrate. (2) The top of the biofilm is dominated by active biomass and EPS, while the bottom is dominated by residual inert biomass. Within the top layers, active biomass has a much higher concentration than EPS. (3) The top of all biofilm is quite "fluffy," while the bottom is dense. (4) The peak of the composite density does not correspond to the peak of active biomass. (5) All biomass types show considerable local heterogeneity. The series of cases also indicate what conditions lead to particular characteristics observed in some biofilms. Biofilm clusters are promoted by substrate limitation, a high detachment rate, or strong consolidation. A high biofilm density is associated with an old biofilm, which is favored by a low substrate concentration, a high detachment rate, and strong consolidation. Old biofilms also can develop low-density pockets near the substratum, a possible cause of sloughing. Local heterogeneity is generally related to the same factors that cause a high density. We also solved the UMCCA model for conditions similar to the experiments of Bishop et al. (Water Sci. Technol. 31(1) (1995) 143), who measured the total biomass density in layers from the substratum. The model outputs captured all the major trends in the experimental data: the overall thickness and density of biofilms increase with time, and the total biomass density is 5-10 times greater near the substratum than near the top of the biofilm. Furthermore, the model indicates that the residual inert biomass becomes denser toward the substratum, a trend observed experimentally; the UMCCA model suggests that this trend is due to the combined effects of consolidation and inert biomass having a larger maximum density.


Asunto(s)
Biopelículas/crecimiento & desarrollo , Reactores Biológicos , Modelos Biológicos , Automatización , Biomasa , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos
5.
Water Res ; 38(14-15): 3349-61, 2004.
Artículo en Inglés | MEDLINE | ID: mdl-15276752

RESUMEN

We present the unified multi-component cellular automaton (UMCCA) model, which predicts quantitatively the development of the biofilm's composite density for three biofilm components: active bacteria, inert or dead biomass, and extracellular polymeric substances. The model also describes the concentrations of three soluble organic components (soluble substrate and two types of soluble microbial products) and oxygen. The UMCCA model is a hybrid discrete-differential mathematical model and introduces the novel feature of biofilm consolidation. Our hypothesis is that the fluid over the biofilm creates pressures and vibrations that cause the biofilm to consolidate, or pack itself to a higher density over time. Each biofilm compartment in the model output consolidates to a different degree that depends on the age of its biomass. The UMCCA model also adds a cellular automaton algorithm that identifies the path of least resistance and directly moves excess biomass along that path, thereby ensuring that the excess biomass is distributed efficiently. A companion paper illustrates the trends that the UMCCA model is able to represent and shows a comparison with experimental results.


Asunto(s)
Fenómenos Fisiológicos Bacterianos , Biopelículas/crecimiento & desarrollo , Biomasa , Biopolímeros/química , Algoritmos , Automatización , Biopolímeros/metabolismo , Reactores Biológicos , Predicción , Modelos Biológicos , Eliminación de Residuos Líquidos/métodos , Purificación del Agua/métodos
6.
Water Res ; 36(8): 1983-92, 2002 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-12092573

RESUMEN

We present a modeling approach that quantifies the unified theory presented in the companion paper. In this approach, we use mathematical modeling to quantify the relationships among three solid species--bacteria, extracellular polymeric substances (EPS), and inert residual biomass-two soluble microbial products (SMP), original substrate, and an electron acceptor. According to the model, donor electrons are used for the synthesis of biomass, EPS, and utilization-associated products. Residual inert biomass and biomass-associated products are produced from the decay of active biomass and the hydrolysis of EPS, respectively. The model includes mass balance equations that consistently describe the flow of electrons among the components. It is solved with a set of parameters appropriate to the experimental study of Hsieh et al. (Biotech. Bioeng. 44 (1994) 219). Model outputs capture all trends observed in steady-state CSTR experiments and transient batch experiments. This agreement supports that the unified theory correctly captures the interconnections among SMP, EPS, and active and inert biomass.


Asunto(s)
Bacterias , Modelos Teóricos , Polímeros/química , Biomasa , Reactores Biológicos , Electrones , Hidrólisis , Solubilidad
7.
Water Res ; 36(11): 2711-20, 2002 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-12146858

RESUMEN

We present a critical review of the relationships among three microbial products: extracellular polymeric substances (EPS), soluble microbial products (SMP), and inert biomass. Up to now, two different "schools" of researchers have treated these products separately. The "EPS school" has considered active biomass and EPS, while the "SMP school" has considered active biomass, SMP, and inert biomass. Here, we provide a critical review of each of the microbial products. Then, we develop a unified theory that couples them and reconciles apparent contradictions. In our unified theory, cells use electrons from the electron-donor substrate to build active biomass, and they also produce bound EPS and utilization-associated products (UAP) at the same time and in proportion to substrate utilization. Bound EPS are hydrolyzed to biomass-associated products (BAP), while active biomass undergoes endogenous decay to form residual dead cells. Finally, UAP and BAP, being biodegradable, are utilized by active biomass as recycled electron-donors substrates. Our unified theory shows that the apparently distinct products from the SMP and EPS schools overlap each other. Soluble EPS is actually SMP, or the sum of UAP and BAP. Furthermore, active biomass, as defined by the SMP school, includes bound EPS, while inert biomass includes bound EPS and the residual dead cells.


Asunto(s)
Reactores Biológicos , Modelos Teóricos , Polímeros/química , Eliminación de Residuos , Biopelículas , Biomasa , Hidrólisis , Compuestos Orgánicos/metabolismo , Polímeros/metabolismo , Solubilidad
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