Showing papers on "Water environment published in 2009"

Antibiotic resistance genes in water environment.

Abstract: The use of antibiotics may accelerate the development of antibiotic resistance genes (ARGs) and bacteria which shade health risks to humans and animals. The emerging of ARGs in the water environment is becoming an increasing worldwide concern. Hundreds of various ARGs encoding resistance to a broad range of antibiotics have been found in microorganisms distributed not only in hospital wastewaters and animal production wastewaters, but also in sewage, wastewater treatment plants, surface water, groundwater, and even in drinking water. This review summarizes recently published information on the types, distributions, and horizontal transfer of ARGs in various aquatic environments, as well as the molecular methods used to detect environmental ARGs, including specific and multiplex PCR (polymerase chain reaction), real-time PCR, DNA sequencing, and hybridization based techniques.

Vesicular perylene dye nanocapsules as supramolecular fluorescent pH sensor systems.

Abstract: Water-soluble, self-assembled nanocapsules composed of a functional bilayer membrane and enclosed guest molecules can provide smart (that is, condition responsive) sensors for a variety of purposes. Owing to their outstanding optical and redox properties, perylene bisimide chromophores are interesting building blocks for a functional bilayer membrane in a water environment. Here, we report water-soluble perylene bisimide vesicles loaded with bispyrene-based energy donors in their aqueous interior. These loaded vesicles are stabilized by in situ photopolymerization to give nanocapsules that are stable over the entire aqueous pH range. On the basis of pH-tunable spectral overlap of donors and acceptors, the donor-loaded polymerized vesicles display pH-dependent fluorescence resonance energy transfer from the encapsulated donors to the bilayer dye membrane, providing ultrasensitive pH information on their aqueous environment with fluorescence colour changes covering the whole visible light range. At pH 9.0, quite exceptional white fluorescence could be observed for such water-soluble donor-loaded perylene vesicles.

Nitrogen removal in constructed wetland systems

Abstract: Since the mid 1990s, constructed wetlands have been increasingly used as a low-energy ‘green’ technique, in the treatment of wastewater and stormwater, driven by the rising cost of fossil fuels and increasing concern about climate change. Among various applications of these wetlands, a significant area is the removal of nitrogenous pollutants to protect the water environment and to enable effective reclamation and reuse of the wastewater. This paper provides a review of the current state of nitrogen removal technology, focusing on existing types of wetlands, the mechanisms of nitrogen removal, major environmental factors relative to nitrogen removal, and the operation and management of the wetlands.

Design of a Water Environment Monitoring System Based on Wireless Sensor Networks

Abstract: A water environmental monitoring system based on a wireless sensor network is proposed. It consists of three parts: data monitoring nodes, data base station and remote monitoring center. This system is suitable for the complex and large-scale water environment monitoring, such as for reservoirs, lakes, rivers, swamps, and shallow or deep groundwaters. This paper is devoted to the explanation and illustration for our new water environment monitoring system design. The system had successfully accomplished the online auto-monitoring of the water temperature and pH value environment of an artificial lake. The system's measurement capacity ranges from 0 to 80 °C for water temperature, with an accuracy of ±0.5 °C; from 0 to 14 on pH value, with an accuracy of ±0.05 pH units. Sensors applicable to different water quality scenarios should be installed at the nodes to meet the monitoring demands for a variety of water environments and to obtain different parameters. The monitoring system thus promises broad applicability prospects.

Pakistan's Water Economy Running Dry

Abstract: Pakistan is one of the world's most arid countries, with an average rainfall of under 240 mm a year. The population and the economy are heavily dependent on an annual influx into the Indus river system (including the Indus, Jhelum, Chenab, Ravi, Beas, and Sutlej rivers) of about 180 billion cubic meters of water, that emanates from the neighboring countries and is mostly derived from snow-melt in the Himalayas. Throughout history, people have adapted to the low and poorly distributed rainfall by either living along river banks or by careful husbanding and management of local water resources. One of the greatest of human civilizations-the Indus Valley Civilization (Harappa and Mohenjodaro) flourished along the banks of the Indus. This precarious, low-level balance between man and water was decisively shifted with the advent of large-scale irrigation technology in the nineteenth century. The Indus irrigation system became the largest contiguous irrigation system in the world. The water economy of Pakistan depends fundamentally on a gigantic and complex hydraulic infrastructure system. Pakistan has overcome major water challenges in the past. Pakistan has a remarkable history of successfully confronting major water challenges. There are now a set of related challenges which have to be addressed how to maintain what has been built, what major new system-wide infrastructure needs to be built, what infrastructure needs to be built for populations who have not been served and for environmental protection, and how to build institutions that will manage the resource effectively in the looming era of scarcity. Pakistan needs to develop its indigenous capacity and make a major push to establish and nurture a new set of institutions that will provide the scientific, technical, and policy support for the management of increasingly scarce water. Experience in other countries shows that if this is not done there will be serious economic, social, and environmental consequences.

Hydrolysis and photolysis of oxytetracycline in aqueous solution.

Abstract: Oxytetracycline ((2Z,4S,4aR,5S,5aR,6S,12aS)-2-(amino-hydroxy-methylidene)-4-dimethylamino-5,6,10,11,12a-pentahydroxy-6-methyl-4,4a,5,5a-tetrahydrotetracene-1,3,12-trione) is a member of tetracycline antibiotics family and is widely administered to farm animals for the purpose of therapeutical treatment and health protection. Increasing attention has been paid to the environmental fate of oxytetracycline and other veterinary antibiotics with the occurrence of these antibiotics in the environment. The hydrolysis and photolysis degradation of oxytetracycline was investigated in this study. Oxytetracycline hydrolysis was found to obey the first-order model and similar rate constant values ranging from 0.094 +/- 0.001 to 0.106 +/- 0.003 day(-1) were obtained at different initial concentration ranging from 10 to 230 microM. Solution pH and temperature were shown to have remarked effects on oxytetracycline hydrolysis. The hydrolysis in pH neutral solution appeared to be much faster than in both acidic and alkaline solutions. Oxytetracycline half-life decreased from 1.2 x 10(2) to 0.15 day with the increasing temperature from 4 +/- 0.8 to 60 +/- 1 degrees C. The presence of Ca(2+) made oxytetracycline hydrolytic degradation kinetics deviate from the simple first-order model to the availability-adjusted first-order model and greatly slowed down the hydrolysis. Oxytetracycline photolysis was found to be very fast with a degradation rate constant at 3.61 +/- 0.06 day(-1), which is comparable to that of hydrolysis at 60 degrees C. The presence of Ca(2+) accelerated oxytetracycline photolysis, implying that oxytetracycline become more vulnerable to sunlight irradiation after chelating with Ca(2+). The photolysis may be the dominant degradation pathway of oxytetracycline in shallow transparent water environment.

Particle size distribution and pollutants in road-deposited sediments in different areas of Zhenjiang, China

Abstract: An understanding of road-deposited sediment (RDS) characteristics on an impervious surface is essential to estimate pollutant washoff characteristics and to minimise the impacts of pollutants on the water environment. A total of 62 RDS samples were collected from four different land-use types (commercial, residential, intense traffic and riverside park) in Zhenjiang City, China. The samples were fractionated into seven grain-size classes and analysed for particle size distribution and concentrations of pollutants. The samples are found to consist predominantly of fine particles (60-80%, <250 microm). The maximum mean concentrations of zinc, lead and copper were 686.93, 589.19 and 158.16 mg/kg, respectively, with the highest metal concentrations found in samples from the intense traffic area. The maximum mean contents of organic matter (12.55%), nitrogen (6.31 mg/g) and phosphorus (5.15 mg/g) were found in samples from the commercial area. The concentrations of heavy metals were highest in the smallest particle size fraction analysed (63 microm). The organic matter and nitrogen content generally increased with decreasing particle sizes in the <500-microm particle size range. The results also revealed that most of the total nitrogen (TN) is attached to the finer sediments and that to effectively reduce TN loads in particulates, treatment facilities must be able to remove the finer particles (down to 125 microm for TN).

New exploration and understanding of traditional Chinese medicine.

Abstract: Traditional Chinese Medicine (TCM), originating from oriental philosophy and culture, has been developing through a series of special research and experiments with meditation, accumulation of experiences, and a complete comprehension of ancient theories and methods. However, compared with Conventional Western Medicine (CWM), the theory of TCM is complicated and not easily accepted by Westerners. It is important to explore TCM by using modern scientific techniques and theories. Utilizing his frontier experience and up-to-date scientific knowledge, Dr. Qian Xuesen has been trying to incorporate some key principles with the comprehensive understanding of TCM and clarify difficult but important concepts and principles. Some examples are the existence of invisible matter; 'Qi' and 'Qi monism'; the Heart representing the 'whole will' of human beings; the water environment functioning as a fundamental condition of life; the human body being united with nature and universe as one; the spirit and physical body always being considered unified and connected with the five viscera, especially with the Heart; and the Chinese herbal formula working with different principles than CWM drugs. These works are important for understanding the essence of TCM, the promoting of the modernization of TCM theories by means of the latest of achievements in scientific developments, establishing the direction for future medicines with TCM characteristics, uniting Chinese and Western medicines, and exploiting a bright future for the health of mankind.

Class 1 integronase gene and tetracycline resistance genes tetA and tetC in different water environments of Jiangsu Province, China.

Abstract: Class 1 integronase gene (intI1) and tetracycline resistance genes (tetA and tetC) from various environmental sites in Jiangsu Province (China) were detected using qualitative PCR (polymerase chain reaction) and quantified with SYBR Green-based qRT-PCR (quantitative real-time PCR) in this study. Qualitative PCR assays demonstrated that intI1, tetA and tetC occurred in the water environments of Taihu Lake, the Nanjing section of the Yangtze River, a sewage treatment plant (STP) in Nanjing City, and two drinking water treating bioreactors. qRT-PCR results showed that abundance of intI1 in lake water and sediments was lower than the tet genes, for a given sample site and date (P < 0.05). On a volumetric basis, lake sediments contained higher concentrations of the three genes by four to five orders of magnitude than water samples, and lake water and sediments sampled in April contained fewer copies of all the genes than the samples collected in June and August (P < 0.05). The levels of intI1, tetA and tetC in the Yangtze River water increased significantly after the river flowed through Nanjing City (P < 0.05). 94.1% integron, 97.2% tetA and 98.3% tetC were removed by the activated sludge process in the STP, and more than 80% of each gene was removed in both of the two biofilters in terms of relative concentration based on sample volume. However, on the basis of DNA mass, lower removals were obtained for both the activated sludge and biofiltration processes.

Norovirus distribution within an estuarine environment.

Abstract: Human norovirus (NoV) has been studied extensively as an important cause of gastroenteritis outbreaks worldwide While oysters are a primary vehicle for infection, few studies have examined the wider distribution of NoV in the estuarine environment Active shellfish-harvesting areas in Georgia were examined for the prevalence, genotype diversity, and concentrations of NoV in a variety of estuarine sample types over the course of 1 year Of the 225 samples (9 oyster, 72 water, 72 63- to 200-μm plankton, and 72 >200-μm plankton) collected from 12 stations across two estuaries, 21 samples (93%) tested positive for NoV By sample type, 550% (5/9) of oysters, 83% (6/72) of water samples, 111% (8/72) of 63- to 200-μm plankton samples, and 28% (2/72) of >200-μm plankton samples were positive for human NoV The two NoV-positive >200-μm plankton samples, which contained mainly zooplankton, had the greatest quantity of NoV genomes (35 × 1013 and 17 × 1015 genomes g−1) of any sample tested The majority, 905% (19/21), of the samples tested positive for genogroup I NoV, and only 95% (2/21) of the samples tested positive for genogroup II The high concentrations of NoV in plankton samples compared to water and oyster samples were unexpected and provide new insights into the presence and distribution of human NoV in the water environment

Exploring molecular mechanisms of ligand recognition by opioid receptors with metadynamics.

Abstract: Opioid receptors are G protein-coupled receptors (GPCRs) of utmost significance in the development of potent analgesic drugs for the treatment of severe pain. An accurate evaluation at the molecular level of the ligand binding pathways into these receptors may play a key role in the design of new molecules with more desirable properties and reduced side effects. The recent characterization of high-resolution X-ray crystal structures of non-rhodopsin GPCRs for diffusible hormones and neurotransmitters presents an unprecedented opportunity to build improved homology models of opioid receptors, and to study in more detail their molecular mechanisms of ligand recognition. In this study, possible pathways for entry of the nonselective antagonist naloxone (NLX) from the water environment into the well-accepted alkaloid binding pocket of a delta opioid receptor (DOR) molecular model based on the β2-adrenergic receptor crystal structure are explored using microsecond-scale well-tempered metadynamics simulations. ...

Transport and adsorption of antibiotics by marine sediments in a dynamic environment

Abstract: Bed sediments are the major sink for many contaminants in aquatic environments. With increasing knowledge of and research on the environmental occurrence of antibiotics, there has been growing interest in their behaviour and fate in aquatic environments. However, there is little information about the behaviour of antibiotics in a dynamic water/sediment environment, such as river and coastal marine water. Therefore, the aims of the present study were: (1) to study the transport and distribution of four common antibiotics between water and sediment in both dynamic and quiescent water/sediment systems and (2) to understand the persistence and possible degradation of the four antibiotics in the two different systems. A lid-driven elongated annular flume, designed to reduce the centrifugal effect, was used to simulate a dynamic water environment. In addition, a quiescent water/sediment experiment was conducted for comparison with the dynamic water system. The seawater and sediment, used in both experiments of flowing and quiescent water/sediment systems, were collected from Victoria Harbour, a dynamic coastal environment in an urban setting. The four antibiotics selected in this study were ofloxacin (OFL), roxithromycin (RTM), erythromycin (ETM), and sulfamethoxazole (SMZ), the most commonly used antibiotics in South China. Antibiotics in an overlying solution decreased very quickly in the flume system due to the sorption to suspended particles and surface sediment. There were significant differences in the adsorption of the four antibiotics in sediment. OFL showed a high tendency to be adsorbed by sediment with a high K (d) value (2980 L/Kg), while the low K (d) values of SMZ indicated that there was a large quantity in water. The four antibiotics reached a depth of 20-30 mm in the sediment over a period of 60 days in the flume system. However, the compounds were only found in surface sediment (above 10 mm) in the quiescent system, indicating the influence of the dynamic flume system on the distribution of antibiotics in sediment. OFL showed a moderate persistence in the dynamic flume system, while other three antibiotics had less persistence in sediment. However, all of the four compounds showed moderate persistence in the quiescent system. The study showed the rapid diffusive transfer of antibiotics from water to sediment in the dynamic flume system. The four antibiotics exhibited larger differences in their adsorption to sediment in both dynamic and quiescent systems due to their different K (d) values. The high sorption of antibiotics to marine sediment may reduce their availability to benthic invertebrates.

Aspirations and Realities under the Water Framework Directive: Proceduralisation, Participation and Practicalities

Abstract: The European Community Water Framework Directive (2000/60/EC) adopts an innovative, holistic and target-orientated approach to the management of relevant waters, with the ambitious aim of achieving ‘good status’ for all relevant waters by 2015. At a ‘half-way’ stage towards full implementation, this article takes stock of practical implementation in England and Wales, and reflects more generally upon the challenges of implementation. On proceduralisation, the discussion suggests that substantive elements are seen to be greatly overshadowed by the breadth of national implementation discretion. Avoiding realisation of good status is allowed and broadly worded derogation provisions are interpreted to enable this. Incongruities between the ideals underlying public engagement and the realities of applying complex environmental legislation are evident. Issues for resolution shift from broad concerns about the desired state of the water environment to highly technical questions about operationalising methodologies (that are likely to exclude public engagement).

Influence of water on elementary reaction steps in electrocatalysis

Abstract: We studied simple reaction pathways of molecules interacting with Pt(111) in the presence of water and ions using density functional theory within the generalized gradient approximation. We particularly focus on the dissociation of H2 and O2 on Pt(111) which represent important reaction steps in the hydrogen evolution/oxidation reaction and the oxygen reduction reaction, respectively. Because of the weak interaction of water with Pt(111), the electronic structure of the Pt electrode is hardly perturbed by the presence of water. Consequently, processes that occur directly at the electrode surface, such as specific adsorption or the dissociation of oxygen from the chemisorbed molecular oxygen state, are only weakly influenced by water. In contrast, processes that occur further away from the electrode, such as the dissociation of H2, can be modified by the water environment through direct molecule–water interaction.

Poly(N-isopropylacrylamide) Thin Films Densely Grafted onto Gold Surface: Preparation, Characterization, and Dynamic AFM Study of Temperature-Induced Chain Conformational Changes

Abstract: Thermally responsive poly(N-isopropylacrylamide) (PNIPAM) films are attracting considerable attention since they offer the possibility to achieve reversible control over surface wettability and biocompatibility. In this paper, we first report a new and simple method for the grafting under melt of amine-terminated PNIPAM chains onto gold surfaces modified with a self-assembled monolayer (SAM) of reactive thiols. The formation of homogeneous tethered PNIPAM films, whose thickness can be tuned by adjusting polymer molecular weight or SAM reactivity, is evidenced by using the combination of ellipsometry, X-ray photon spectroscopy, infrared spectroscopy (PM-IRRAS), and atomic force microscopy. The calculation of grafting parameters from experimental measurements indicated the synthesis of densely grafted PNIPAM films and allowed us to predict a "brushlike" regime for the chains in good solvent. In a second part, the temperature-induced responsive properties are studied in situ by conducting dynamic AFM measurements using the amplitude modulation technique. Imaging in water environment first revealed the reversible modification of surface morphology below and above the theoretical lower critical solution temperature (LCST) of PNIPAM. Then, the determination of amplitude and phase approach curves at various temperatures provided direct measurement of the evolution of the damping factor, or similarly the dissipated energy, as a function of the probe indentation into the PNIPAM film. Most interestingly, we clearly showed the subtle and progressive thermally induced chain conformational change occurring at the scale of several nanometers around the expected LCST.

Surface Phase Diagram and Oxygen Coupling Kinetics on Flat and Stepped Pt Surfaces under Electrochemical Potentials

Abstract: Electrochemical reactions catalyzed by metal electrode, despite their huge importance in industry, are not well understood at the atomic level. In relevance to water electrolysis, the oxygen coupling reaction on Pt metal surfaces is systematically investigated in this work by combining periodic density functional theory calculations with a new theoretical approach to mimic the electrochemical environment. In our approach, the surface is explicitly polarized by adding/subtracting charges and the counter charges are placed as Gaussian-distributed plane charges in a vacuum. With this method, the surface phase diagrams for both the closed-packed Pt(111) and stepped Pt(211) are determined, which demonstrates that stepped surface sites can better accumulate oxidative species and thus reach to a higher local O coverage compared to Pt(111) at a given potential. The water environment is proved to affect the phase diagram marginally. By fully exploring the possible oxygen coupling channels on Pt surfaces, we show t...

Superlow friction behavior of Si-doped hydrogenated amorphous carbon film in water environment

Abstract: Si-doped hydrogenated amorphous carbon (a-C:H:Si) film was prepared using hybrid radio frequency plasma-enhanced chemical vapor deposition (R.F. PECVD) and non-balanced magnetron sputtering deposition technique. The microstructure of the film was characterized by means of Raman spectrometry, X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD), while its friction behavior in water environment was investigated using a ball-on-disc tribometer. Results show that the a-C:H:Si film has typical diamond-like characteristics, and Si doped with a relative atomic concentration of about 3.9% in the film mainly exists in the form of Si, SiC, and SiO 2 , while it shows a superlow friction coefficient of about 0.005 in water environment when sliding against Si 3 N 4 ball. The superlow friction behavior of the hybrid diamond-like-carbon (DLC) film could be attributed to the formation of a tribochemical reaction film and boundary lubrication layer mainly consisting of colloidal silica generated from tribochemical reactions between silicides and water molecules.

The water environment of cities

Abstract: The Urban Water Budget.- Groundwater in the Urban Environment.- Urban Infrastructure and Use of Mass Balance Models for Water and Salt.- New Concepts for Managing Urban Pollution.- Streams and Urbanization.- Urban Water Recreation: Experiences, Place Meanings, and Future Issues.- Urban Design and Urban Water Ecosystems.- Legal Framework for the Urban Water Environment.- Institutions Affecting the Urban Water Environment.- Institutional Structures for Water Management in the Eastern United States.- Adaptive Water Quantity Management: Designing for Sustainability and Resiliency in Water Scarce Regions.- Demand Management, Privatization, Water Markets, and Efficient Water Allocation in Our Cities.- Principles for Managing the Urban Water Environment in the 21st Century.

Nanotechnologies for Water Environment Applications

Abstract: This book is useful to undergraduate and graduate students in engineering and practicing engineers, as well as educators, scientists, government officials, policymakers, and industrial process managers.