Water Quality and Conditioning in Natural Ecosystems: Biomachinery Theory of Self-Purification of Water

General principles of the theory of polyfunctional role of biota in self-purification of water in aquatic ecosystems have been formulated. The theory includes the following elements: (1) energy sources for self-purification of aquatic ecosystems; (2) main functional units of the self-purification system; (3) main selfpurification processes; (4) contributions of major taxa to self-purification of aquatic ecosystems; (5) reliability of the system and mechanisms ensuring it; (6) self-regulation of biota; (7) response of the system to external stimuli (impacts); (8) analogy between an ecosystem and a bioreactor; (9) conclusions for nature conservation practice. The theory covers both freshwater and marine ecosystems.     

Acid-base properties of aquatic humic substances isolated from unpolluted tropical black water rivers

Summary The acid-base properties of tropical aquatic humic substances isolated from 2 Venezuelan black water rivers were studied. A model with discrete pK values was applied to potentiometric titration data, since direct determination of pK and concentration values from titration curves is not possible. In the computational procedure simulated curves have been compared with the titration curves to improve the calculations for pK and concentration values. Both rivers (Yuruaní and Aponwao) are located in a zone where the human influence is still negligible. The geomorphological characteristics of this remote area (Gran Sabana) are singular in relation to the rest of the world. The rivers have been monthly studied at sampling site, during the rainy season (May–September). Six discrete acidic groups represented well the acidic characteristics of aquatic humic substances under consideration. The average pK values were 2.74, 4.37, 5.67, 7.09, 8.73 and 10.30, and the average concentration values for each group were 2.50, 1.80, 0.94, 0.62, 0.66, and 1.31 mmol/g humic substance, respectively. Considering the factors month and river, significant quantitative, but not qualitative, differences were in general found. A comparison with data from temperate ecosystems showed that the three most acidic groups presented similar acid-base characteristics, wheras the three other groups are quite different for the tropical aquatic humic substances under study.     

The importance of element speciation in water analysis — a plea for further investigations

Water analysis is dominated by parameters given in laws and recommendations concerning water quality. Speciation has been broadly neglected. This might be due to the difficulties in defining speciation and in determining species at low concentrations. This paper addresses the physical, chemical and biological approaches to speciation and gives examples for methods which are suited for species determination in aquatic systems. Metals and non-metallic elements are covered as well. It is obvious that speciation is a key for understanding the function of aquatic ecosystems and their technical utilization.     

Issues of the Study of Detritus in Aquatic Systems

In this paper, we present the analysis of the ecological roles of detritus and suspended particulate matter in aquatic ecosystems. New data that have been obtained for freshwater ecosystems of the central part of Russian Federation (Moscow Region, e.g., Mozhaiskoe Reservoir) have been included in the analysis. These new data include the results of studies of samples of water and detritus from the aquatic ecosystems. The review analysis addresses both freshwater and marine ecosystems. The multifunctional important role of detritus in aquatic ecosystems has been shown and exemplified using data for aquatic bodies of different trophic level, from oligotrophic to eutrophic.     

Cell-based electrochemical biosensors for water quality assessment

During recent decades, extensive industrialisation and farming associated with improper waste management policies have led to the release of a wide range of toxic compounds into aquatic ecosystems, causing a rapid decrease of world freshwater resources and thus requiring urgent implementation of suitable legislation to define water remediation and protection strategies. In Europe, the Water Framework Directive aims to restore good qualitative and quantitative status to all water bodies by 2015. To achieve that, extensive monitoring programmes will be required, calling for rapid, reliable and cost-effective analytical methods for monitoring and toxicological impact assessment of water pollutants. In this context, whole cell biosensors appear as excellent alternatives to or techniques complementary to conventional chemical methods. Cells are easy to cultivate and manipulate, host many enzymes able to catalyse a wide range of biological reactions and can be coupled to various types of transducers. In addition, they are able to provide information about the bioavailability and the toxicity of the pollutants towards eukaryotic or prokaryotic cells. In this article, we present an overview of the use of whole cells, mainly bacteria, yeasts and algae, as sensing elements in electrochemical biosensors with respect to their practical applications in water quality monitoring, with particular emphasis on new trends and future perspectives. In contrast to optical detection, electrochemical transduction is not sensitive to light, can be used for analysis of turbid samples and does not require labelling. In some cases, it is also possible to achieve higher selectivities, even without cell modification, by operating at specific potentials where interferences are limited.     

Study of the interactions between <Emphasis Type="Italic">Elodea canadensis</Emphasis> and CuO nanoparticles

Copper is one of the key heavy metals that pollute environment and constitute a serious threat to the health of humans and ecosystems. Copper may enter the aquatic environment in both soluble and nanoparticle form. It was previously found in a series of studies that nanoparticles, including those of several metal oxides, exercise both negative and positive effects on the higher plants which makes necessary further research on the interaction between metal oxide nanoparticles and plants. Interactions between aquatic plants and copper-containing nanoparticles were not sufficiently studied. The goal of this study was to contribute to the investigation of the interactions between CuO nanoparticles and the aquatic plant Elodea canadensis under the conditions of experimental microcosms. It was found that CuO nanoparticles demonstrated some phytotoxicity to Elodea canadensis. After the incubation of Elodea canadensis in the aquatic medium contaminated with CuO nanoparticles there was a significant increase (by two orders of magnitude) of the concentration of copper in the biomass of the plants.     

Review of separation methods for the determination of ammonium/ammonia in natural water

Ammonium (NH₄⁺) and ammonia (NH₃) in aquatic ecosystems are of great interest to environmental scientists because they can be used to study the nitrogen cycle and as water quality indicators. Analytical separation methods developed in recent decades have been used widely to determine NH₄⁺ and NH₃ in aqueous solutions. This review presents an overview of state-of-the-art separation methods and analytical techniques for determining NH₃/NH₄⁺ in natural water, including chromatographic methods, electrophoretic methods, extraction methods, membrane-based gas diffusion methods, membraneless gas diffusion methods, passive sampling methods, and paper-based analytical methods. Common detection techniques that can be used in conjunction with particular separation methods are described, phase-transfer strategies (liquid-liquid, liquid-solid, liquid-membrane-liquid, and liquid-gas-liquid methods) are highlighted, and the strengths and weaknesses of the separation methods are discussed. The outlook, challenges, and expected future developments in the field of separation methods for determining NH₄⁺ and NH₃ in natural water are presented.     

SPE and HPLC monitoring of 17-β-estradiol in Egyptian aquatic ecosysetms

Solid-phase extraction and HPLC methods are described for monitoring of 17-β-estradiol residues in Egyptian aquatic ecosystems (water, fish, mollusks, sediment, and drinking water) at the Nile River, Suez Canal region, and northeast of Egypt. Molecular imprinted polymer was prepared and used in extraction. High performance liquid chromatography (HPLC) columns used were Supelcosil C₁₈ and Nucleosil C₁₈. The mobile phases used were different combinations of water and acetonitrile. The concentration of 17-β-estradiol in water, aquatic animals, and sediment samples were of 265.13–7988.12 µg/L, 0.503–96.167, and 0.775–11.884 µg/kg, respectively. Marine lake was contained with high levels of 17-β-estradiol (P < 0.05). Similarly, the Nile River downstream showed high levels of 17-β-estradiol. The detected concentrations in mollusks were significantly higher than those detected in fish. Tilapia fish did not show 17-β-estradiol. Contrarily, low concentrations were detected in the rivulet streams supplied by the Nile River. Besides, 17-β-estradiol was also detected in the sediments at low levels. Detection of 17-β-estradiol in the Egyptian ecosystems attracted attention toward heavy reliance on some esterogenic medicinal products in Egypt. The monitoring of 17-β-estradiol in other water bodies was recommended. Besides, the development of methodologies of bioremediation to eliminate 17-β-estradiol from the Egyptian and other water resources of the world was also suggested.     

Migration processes of <Superscript>137</Superscript>Cs and <Superscript>90</Superscript>Sr in compartments of a lake ecosystem

Summary The dispersion of radioactive substances in the environment following nuclear weapon tests in atmosphere since 1954 and accidents to nuclear plants, like that in Chernobyl in 1986, have allowed us to study the migration processes of some radionuclides in complex ecosystems such as lakes are. In the present paper the behavior of ¹³⁷Cs and ⁹⁰Sr in different compartments of the Monterosi Lake (central Italy) was assessed. The ¹³⁷Cs concentration was measured in lake water as well as sediment, stream water, aquatic plant and fish samples. ⁹⁰Sr concentration in water and sediments was also determined. A total inventory of 4206±76 Bq ^. m^-2 and 958±79 Bq ^. m^-2 (on 27/6/01) has been found for ¹³⁷Cs and ⁹⁰Sr, respectively. The experimental data presented here allow to calibrate theoretical models predicting the temporal trend of radionuclide concentration in similar ecosystems. Moreover, information on cesium and strontium migration processes can be extended to other pollutants having similar environmental behavior.     

Analysis of thyroid hormones in raw and treated waste water

An analytical method for the quantification of thyroid hormones (3,5,3′,5′-tetraiodo-l-thyronine, 3,3′,5-triiodo-l-thyronine, 3,3′,5′-triiodothyronine, 3,5-diiodothyronine, 3,3′-diiodothyronine) in different water matrices has been developed. The method, consisting of solid phase extraction (SPE) and liquid chromatography–tandem mass spectrometry (LC–MS/MS), was validated for tap and surface water as well as raw and treated waste water. The limits of quantifications (LOQs) were lowest in tap water, where they ranged from 1.1 to 13.3 ng L⁻¹, and highest in raw wastewater (10.5–84.9 ng L⁻¹). Of the target analytes 3,5,3′,5′-tetraiodo-l-thyronine (T₄) could be quantified in the influent and effluent of a waste water treatment plant (WWTP) in Finland. The study showed that despite a relatively high removal rate during treatment (66%), part of the incoming T₄ will reach the aquatic environment and, due to the high endocrine activity of this compound, further studies are needed in order to assess its environmental fate and impact on natural ecosystems.     

Multiresidue method for the determination of 13 pesticides in three environmental matrices: water, sediments and fish muscle

Pesticides residues in aquatic ecosystems are an environmental concern which requires efficient analytical methods. In this study, we proposed a generic method for the quantification of 13 pesticides (azoxystrobin, clomazone, diflufenican, dimethachlor, carbendazim, iprodion, isoproturon, mesosulfuron-methyl, metazachlor, napropamid, quizalofop and thifensulfuron-methyl) in three environmental matrices. Pesticides from water were extracted using a solid phase extraction system and a single solid-liquid extraction method was optimized for sediment and fish muscle, followed by a unique analysis by liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). Limits of quantification were below 5 ng L⁻¹ for water (except for fluroxypyr and iprodion) and ranged between 0.1 ng g⁻¹ and 57.7 ng g⁻¹ for sediments and regarding fish, were below 1 ng g⁻¹ for 8 molecules and were determined between 5 and 49 ng g⁻¹ for the 5 other compounds. This method was finally used as a new routine practice for environmental research.     

Investigation of interaction strategies between pyrazolone dyes and poly(acrylamide-co-acrylic acid)

The removal of dyes from waste water before their discharge into aquatic ecosystems is of substantial concern. Amongst functional macromolecules, the combination of polymers with dyes is a research field of enormous potential with regard to high-performance materials. The present study investigates interactions strategies between P(AM-co-AA) polymer with pyrazolone azo dyes in water as green solvent. These interactions were confirmed by FTIR spectroscopy, Ultra-visible spectroscopy, EDAX analysis, and FE-SEM analysis. Polymer P(AM-co-AA) has porous structure in which dyes present in the water get absorb hence it is use to remove pyrazolone dyes from water.

     

Development of ICP-MS and ICP-OES methods for determination of gadolinium in samples related to hospital waste water treatment

A suitable analytical method making possible the determination of Gd and other rare-earth elements in samples related to hospital waste water treatment was sought with regard to various aspects of the experiment aimed at monitoring the fate of Gd-based contrast agents in the aquatic environment. The discrepancies and pitfalls of the proposed methodology were considered, resulting in a functional experimental plan. The inductively coupled plasma mass spectrometry (ICP-MS) method was used for the determination of Gd and other rare earth elements in river and hospital waste water and algae Parachlorella kessleri cultured in laboratory experiments. The sample preparation of algae prior to analysis was optimised. The ICP-MS method was validated using a recovery study, sample blanks, reference materials, and comparison with the inductively coupled plasma optical emission spectrometry (ICP-OES) method. The ICP-MS method was confirmed as suitable for monitoring the biosorption/bioaccumulation of Gd in algae and for evaluating the Gd anomaly in hospital waste water and rivers of Eastern Bohemia. In the laboratory experiments, the bioconcentration factors were calculated (all in L kg^?1) for algae cultured in inorganic Gd salt (about 1100), in waste water from a magnetic resonance workplace (2300) and in waste water from a hospital waste water treatment plant (4400). A positive Gd anomaly in waters from the river Elbe in the Eastern Bohemia region was found less pronounced in the areas unaffected than in the areas affected by waste waters from hospital.     

On the SCF theory of continuum solvent effects representation: Introduction of local dielectric effects

The introduction of local dielectric effects within the SCF theory of continuum solvent effects representation is examined at a semiempirical level. The formalism is developed in the frame of the reaction field theory within the effective charge approximation. The solvation free energies of Li⁺, Na⁺, F^?, and Cl^? ions in water were calculated in order to illustrate the reliability of the proposed model. The extension to molecules and molecular ions was performed including a desolvation corrective term related to the specific neighborhood of each atomic center. The results show a qualitative agreement with experimental data. A comment on the solvatonlike models for incorporating the solvent effect into the Hamiltonian is also given.     

Thermodynamics of supercooled water

We review the available experimental information on the thermodynamic properties of supercooled water and demonstrate the possibility of modeling these thermodynamic properties on a theoretical basis. We show that by assuming the existence of a liquid-liquid critical point in supercooled water, the theory of critical phenomena can give an accurate account of the experimental thermodynamic-property data up to a pressure of 150 MPa. In addition, we show that a phenomenological extension of the theoretical model can account for all currently available experimental data in the supercooled region, up to 400 MPa. The stability limit of the liquid state and possible coupling between crystallization and liquid-liquid separation are also discussed. It is concluded that critical-point thermodynamics describes the available thermodynamic data for supercooled water within experimental accuracy, thus establishing a benchmark for further developments in this area.     

Association of Am with humic substances isolated from river waters with different water quality

The association properties of Am with aquatic humic substances in a 0.01M NaClO₄ solution at pH 6-8 were studied on the basis of molecular size distribution. Ten humic substances isolated from river water with different water quality (pH 3.9-8.0 and dissolved organic carbon (DOC) concentration of 2-40 mg/l) were used for comparing their effects on the association of Am. The molecular size distribution of Am in the presence of humic substances from an uncolored river water (DOC 2 mg/l) was different from that at the experimental systems using humic substances from brownish and high DOC (14-40 mg/l) river waters.