Showing papers on "Water environment published in 2006"

Mixed atomistic and coarse-grained molecular dynamics: simulation of a membrane-bound ion channel.

Abstract: The recently developed multiscale coarse-graining (MS-CG) method (Izvekov, S.; Voth, G. A. J. Phys. Chem. B 2005, 109, 2469; J. Chem. Phys. 2005, 123, 134105) is used to build a mixed all-atom and coarse-grained (AA-CG) model of the gramicidin A (gA) ion channel embedded in a dimyristoylphosphatidylcholine (DMPC) lipid bilayer and water environment. In this model, the gA peptide was described in full atomistic detail, while the lipid and water molecules were described using coarse-grained representations. The atom-CG and CG-CG interactions in the mixed AA-CG model were determined using the MS-CG method. Molecular dynamics (MD) simulations were performed using the resulting AA-CG model. The results from simulations of the AA-CG model compare very favorably to those from all-atom MD simulations of the entire system. Since the MS-CG method employs a general and systematic approach to obtain effective interactions from the underlying all-atom models, the present approach to rigorously develop mixed AA-CG models has the potential to be extended to many other systems.

Probing the collective vibrational dynamics of a protein in liquid water by terahertz absorption spectroscopy

Abstract: Biological polymers are expected to exhibit functionally relevant, global, and subglobal collective modes in the terahertz (THz) frequency range (i.e., picosecond timescale). In an effort to monitor these collective motions, we have experimentally determined the absorption spectrum of solvated bovine serum albumin (BSA) from 0.3 to 3.72 THz (10–124 cm−1). We successfully extract the terahertz molar absorption of the solvated BSA from the much stronger attenuation of water and observe in the solvated protein a dense, overlapping spectrum of vibrational modes that increases monotonically with increasing frequency. We see no evidence of distinct, strong, spectral features, suggesting that no specific collective vibrations dominate the protein's spectrum of motions, consistent with the predictions of molecular dynamics simulations and normal mode analyses of a range of small proteins. The shape of the observed spectrum resembles the ideal quadratic spectral density expected for a disordered ionic solid, indicating that the terahertz normal mode density of the solvated BSA may be modeled, to first order, as that of a three-dimensional elastic nanoparticle with an aperiodic charge distribution. Nevertheless, there are important detailed departures from that of a disordered inorganic solid or the normal mode densities predicted for several smaller proteins. These departures are presumably the spectral features arising from the unique molecular details of the solvated BSA. The techniques used here and measurements have the potential to experimentally confront theoretical calculations on a frequency scale that is important for macromolecular motions in a biologically relevant water environment.

Integral Model for Turbulent Buoyant Jets in Unbounded Stratified Flows Part 2: Plane Jet Dynamics Resulting from Multiport Diffuser Jets

Abstract: An integral model for the plane buoyant jet dynamics resulting from the interaction of multiple buoyant jet effluxes spaced along a diffuser line is considered as an extension of the round jet formulation that was proposed in Part I The receiving fluid is given by an unbounded ambient environment with uniform density or stable density stratification and under stagnant or steady sheared current conditions Applications for this situation are primarily for submerged multiport diffusers for discharges of liquid effluents into ambient water bodies, but also for multiple cooling tower plumes and building air-conditioning The CorJet model formulation describes the conservation of mass, momentum, buoyancy and scalar quantities in the turbulent jet flow in the plane jet geometry It employs an entrainment closure approach that distinguishes between the separate contributions of transverse shear and of internal instability mechanisms, and contains a quadratic law turbulent pressure force mechanism But the model formulation also includes several significant three-dimensional effects that distinguish actual diffuser installations in the water environment These relate to local merging processes from the individual multiple jets, to overall finite length effects affecting the plume geometry, and to bottom proximity effects given by a “leakage factor” that measures the combined affect of port height and spacing in allowing the ambient flow to pass through the diffuser line in order to provide sufficient entrainment flow for the mixing downstream from the diffuser The model is validated in several stages: First, comparison with experimental data for the asymptotic, self-similar stages of plane buoyant jet flows, ie the plane pure jet, the pure plume, the pure wake, the advected line puff, and the advected line thermal, support the choice of the turbulent closure coefficients contained in the entrainment formulation Second, comparison with data for many types of non-equilibrium flows with a plane geometry support the proposed functional form of the entrainment relationship, and also the role of the pressure force in the jet deflection dynamics Third, the observed behavior of the merging process from different types of multiport diffuser discharges in both stagnant and flowing ambient conditions and with stratification appears well predicted with the CorJet formulation Fourth, a number of spatial limits of applicability, relating to terminal layer formation in stratification or transition to passive diffusion in a turbulent ambient shear flow, have been proposed In sum, the CorJet integral model appears to provide a mechanistically sound, accurate and reliable representation of complex buoyant jet mixing processes, provided the condition of an unbounded receiving fluid is satisfied

Collective dynamics of lysozyme in water: terahertz absorption spectroscopy and comparison with theory.

Abstract: To directly measure the low-frequency vibrational modes of proteins in biologically relevant water environment rather than previously explored dry or slightly hydrated phase, we have developed a broadband terahertz spectrometer suitable for strongly attenuating protein solutions. Radiation is provided by harmonic multipliers (up to 0.21 THz), a Gunn oscillator (at 0.139 THz), and the UCSB free-electron lasers (up to 4.8 THz). Our spectrometer combines these intense sources with a sensitive cryogenic detector and a variable path length sample cell to detect radiation after it is attenuated by more than 7 orders of magnitudes by the aqueous sample. Using this spectrometer, we have measured the molar extinction of solvated lysozyme between 0.075 and 3.72 THz (2.5-124 cm -1 ), and we made direct comparison to several published theoretical models based on molecular dynamics simulations and normal-mode analysis. We confirm the existence of dense, overlapping normal modes in the terahertz frequency range. Our observed spectrum, while in rough qualitative agreement with these models, differs in detail. Further, we observe a low-frequency cutoff in terahertz dynamics between 0.2 and 0.3 THz, and we see no evidence of a predicted normal mode at 0.09 THz for the protein.

Adjustable fragmentation in laser desorption/ionization from laser-induced silicon microcolumn arrays.

Abstract: Laser-induced silicon microcolumn arrays (LISMA) were developed as matrix-free substrates for soft laser desorption/ionization mass spectrometry (SLDI-MS). When low-resistivity silicon wafers were irradiated in air, sulfur hexafluoride, or water environment with multiple pulses from a 3×ω mode-locked Nd:YAG laser, columnar structures were formed on the surface. The radii of curvature of the column tips varied with the processing environment, ranging from ∼120 nm in water, to <1 μm in SF6, and to ∼2 μm in air. In turn, these microcolumn arrays were used as matrix-free soft laser desorption substrates. In SLDI-MS experiments with a nitrogen laser, the microcolumn arrays obtained in water environment readily produced molecular ions for peptides and synthetic polymers at low laser fluence. These surfaces demonstrated the best ion yield among the three arrays. The threshold laser fluence and ion yield were comparable to those observed in matrix-assisted laser desorption/ionization. Low-femtomole sensitivity an...

Liquefaction Resistance of Undisturbed and Reconstituted Samples of a Natural Coarse Sand from Undrained Cyclic Triaxial Tests

Abstract: The paper deals with an experimental study of the undrained cyclic behavior of a natural coarse sand and gravel deposit located in Gioia Tauro, a town situated on the continental side of the Messina Strait in Italy. The study was conducted through cyclic undrained triaxial tests carried out on both undisturbed and reconstituted samples. Undisturbed samples were recovered by an in situ freezing technique and the sample quality was carefully assessed. Reconstituted samples were prepared by using two different reconstitution methods, namely air pluviation (AP) and water sedimentation (WS), and tested under the same in situ initial relative density and effective overburden stress. Tests were carried out on both isotropically and anisotropically consolidated specimens. The results obtained from this study provide direct evidence that cyclic liquefaction resistance obtained from water sedimented samples closely approximates that exhibited by undisturbed samples in both isotropically and anisotropically consolidated tests. Conversely, AP leads to a marked underestimation. Since the investigated deposit is considered to have been formed by the marine water environment, these results can be regarded as proof that WS closely replicates the in situ fabric of the investigated deposit allowing the substitution of the expensive undisturbed samples with their reconstituted counterparts. Anisotropically consolidated specimens respectively exhibit "cyclic liquefaction" or "cyclic mobility" depending on whether or not they are loaded under the shear stress reversal mode.

Environmental significance of atrazine in aqueous systems and its removal by biological processes: an overview

Abstract: Atrazine, a chlorinated s-triazine group of herbicide is one of the most widely used pesticides in the World. Due to its extensive use, long half-life and various toxic properties, it has very high environmental significance. Up to 22 mg l -1 of atrazine was found in ground water whereas permissible limit of atrazine is in ppb level in drinking water. As per Indian standard there should not be any pesticide present in drinking water. Among many other treatment processes available, Incineration, adsorption, chemical treatment, phytoremediation and biodegradation are the most commonly used ones. Biological degradation of atrazine depends upon various factors like the operating environment, external carbon and nitrogen sources, carbon/ nitrogen ratio (C/N), water content and the bacterial strain. Although, general atrazine degradation pathways are available, the specific pathways in specific conditions are not yet clearly defined. In this paper extensive review has been made on the occurrence of atrazine in surface and ground water bodies, probable sources and causes of its occurrence in water environment, the toxicity of atrazine on various living organisms and its removal by biological processes.

Practical Wastewater Treatment

Abstract: 1 Introduction. Introduction. Water Composition. Pure Water. Salts and Ions in Water. Principal Contaminants and Ions in Water and Measurement Methods. Sources of Water. Water Quality. Water Quality Regulations-Legal Structure. Rules and Regulations for Water Quality Control. Applications. Sample Problem. Solution. Drinking Water Quality Standards: USA and International Standards. 2 Effects of Pollution. Effluent Toxicity Testing. Oxygen Depletion-Biochemical Oxygen Demand. Oxygen Uptake in a Stream-The Oxygen Sag Equation. Biology of Polluted Water. 3 Flow Measurement. Review of Open Channel Hydraulics. Determining Normal and Gradually Varied Flows. Types of Flowmeters. Weir Plates. 4 Sampling and Statistical Considerations. Errors in Process Measurements. Statistical Distributions. Lognormal Distributions. Weibull Distributions. Probable Error. Repeat Measurements. Sampling. 5 Important Concepts from Aquatic Chemistry. Common Ion Species. Most Important Chemicals in the Water Environment. Carbonate Chemistry. Chemical Water Softening. Excess Lime Process. Metals Removal by Precipitation. Heavy Metals. Chromium Reduction and Metals Precipitation. Silicates in Treatment Systems. Nitrogen. Sulfur. Phosphorous. 6 Elements of Biological Treatment. Introduction. BOD and COD Solids. Suspended Solids. Biological Growth Equation. Biological Growth & the Monod Equation. Principles of Biological Treatment Systems. Activated Sludge & Its Varations. Biological Treatment of Difficult Wastes. Modeling the Biological Process. Steady. JASS. Scilab/SeTS. Available Commercial Modeling Tools. Modeling Guidance. The IWA Models for Activated Sludge. 7 Precipitation and Sedimentation. Theory of Sedimentation. Clarifiers and Their Design. Lamellas and Specialty Devices. 8 Filtration Theory and Practice. Depth Filters Design: Theory and Practice. Filtration Hydraulics. Hydraulics of Filter Washing. Skin Filters. Filter Elements and Design. 9 Disinfection. General. Rate of Kill-Disinfection Parameters. Status of U.S. Drinking Water. Chlorine. Ozone. Ultraviolet Light. Other Disinfecting Compounds. 10 Nitrogen Removal. Nitrogen Chemistry and Forms. Ammonia Toxicity and Nitrogen Loading. Nitrate. Nitrogen Removals. Mixed Media and Attached Growth Systems. Conclusions. 11 Phosphorous Removal. General. Biological Phosphorous Removal. Chemical Phosphorous Removal. 12 Anaerobic Treatment. Basic Anaerobic Processes. Anaerobic Pretreatment. Sludge Digestion. Sludge Treatment. Anaerobic Digester Model ADM1. 13 Micro/Ultrafiltration. Introduction to Membrane Separations and Microfiltration. Design Values. Process Selection. 14 Reverse Osmosis. Introduction. Mass Transfer Theory. Membrane Selection. Membrane Materials. Membrane Configurations. RO Design Considerations. Design Parameters. 15 Carbon Adsorption. Breakthrough Curves. The Freundlich and the Langmuir Equations. Carbon Adsorption Physical Coefficients and Economics. PACTTM Process. 16 Ion Exchange. Introduction. Resins. Selectivity. Selectivity Coefficient. Design Considerations. 17 Dissolved Air Flotation and Techniques. Design Basics for DAF. Operating Parameters. Electroflotation. Electrocoagulation. 18 Coagulation, Flocculation, and Chemical Treatment. Introduction. Flocculation and Mixing. Practice. Modeling. 19 Waste Topics. Oily Wastewaters. Blood and Protein. Milk Wastes. Refinery Wastes. Metal Plating Wastes. Starch Wastes. Phenols and Chemical Plant Wastes. Small Waste Flows. Final Thoughts. Index.

Elemental chemical analysis of submerged targets by double-pulse laser-induced breakdown spectroscopy

Abstract: Double-pulse laser-induced plasma spectroscopy (DP-LIPS) is applied to submerged targets to investigate its feasibility for elemental analysis. The role of experimental parameters, such as inter-pulse delay and detection time, has been discussed in terms of the dynamics of the laser-induced bubble produced by the first pulse and its confinement effect on the plasma produced by the second laser pulse. The analytical performance of this technique applied to targets in a water environment are discussed. The elemental analysis of submerged copper alloys by DP-LIPS has been compared with conventional (single-pulse) LIBS in air. Theoretical investigation of the plasma dynamics in water bubbles and open air has been performed.

Evaluating stream water quality through land use analysis in two grassland catchments: impact of wetlands on stream nitrogen concentration.

Abstract: We evaluated the impacts of natural wetlands and various land uses on stream nitrogen concentration in two grassland-dominated catchments in eastern Hokkaido, Japan. Analyzing land use types in drainage basins, measuring denitrification potential of its soil, and water sampling in all seasons of 2003 were performed. Results showed a highly significant positive correlation between the concentration of stream NO3-N and the proportion of upland area in drainage basins in both catchments. The regression slope, which we assumed to reflect the impact on water quality, was 24% lower for the Akkeshi catchment (0.012 +/- 0.001) than for the Shibetsu catchment (0.016 +/- 0.001). In the Akkeshi catchment, there was a significant negative correlation between the proportion of wetlands in the drainage basins and stream NO3-N concentration. Stream dissolved organic nitrogen (DON) and carbon (DOC) concentrations were significantly higher in the Akkeshi catchment. Upland and urban land uses were strongly linked to increases in in-stream N concentrations in both catchments, whereas wetlands and forests tended to mitigate water quality degradation. The denitrification potential of the soils was highest in wetlands, medium in riparian forests, and lowest in grasslands; and was significant in wetlands and riparian forests in the Akkeshi catchment. The solubility of soil organic carbon (SOC) and soil moisture tended to determine the denitrification potential. These results indicate that the water environment within the catchments, which influences denitrification potential and soil organic matter content, could have caused the difference in stream water quality between the two catchments.

A liquid chromatography/tandem mass spectrometric approach for the determination of gangliosides GD3 and GM3 in bovine milk and infant formulae.

Abstract: A liquid chromatographic/tandem mass spectrometric method using pneumatically assisted electrospray ionisation (LC/ESI-MS/MS) was developed for the determination of gangliosides GD3 and GM3 in milk and infant formulae. The gangliosides were extracted in a chloroform/methanol/water environment and cleaned up by solid-phase extraction (SPE) on an end-capped C8 sorbent. The gangliosides were detected in negative ion mode after separation on a reversed-phase (RP) C5 analytical column. From the different ganglioside molecular species, product ions at m/z 290 corresponding to an N-acetylneuraminic acid fragment were produced in the collision cell and used in selected reaction monitoring. A standard addition technique was applied for quantification. The relative repeatability standard deviations were less than 5% for GD3 (level 10 mg/L) and 14% for GM3 (level 0.1–0.2 mg/L). Copyright © 2006 John Wiley & Sons, Ltd.

Contingent valuation approach in measuring the multifunctionality of agriculture and rural areas in Japan

Abstract: The purpose of this study was to measure the economic value of the multifunctionality of agriculture and rural areas based on a more realistic assumption than that adopted in previous studies. Willingness to pay (WTP) for implementing a policy that would maintain a level of multifunctionality corresponding to a 20% decrease in the farmland area in Japan was measured by the double-bounded dichotomous choice contingent valuation method (CVM). According to a country-wide survey, the overall median WTP was 4,144 yen per household annually. The multifunctionality of agriculture and rural areas was classified into eight functions. The WTP for each of these functions was calculated taking into account the ratings assigned to the functions by the respondents. The WTP was 649 yen for flood prevention, 505 yen for recharging groundwater, 642 yen for water environment conservation, 445 yen for soil erosion prevention, 579 yen for organic resource utilization, 394 yen for the development of favorable landscapes, 290 yen for recreation and relaxation, and 641 yen for wildlife protection.

Eco-environmental degradation in the source region of the Yellow River, Northeast Qinghai-Xizang Plateau.

Abstract: The Yellow River is the second longest river in China and the cradle of the Chinese civilization. The source region of the Yellow River is the most important water holding area for the Yellow River, about 49.2% of the whole runoff comes from this region. However, for the special location, it is a region with most fragile eco-environment in China as well. Eco-environmental degradation in the source region of the Yellow River has been a very serious ecological and socially economic problem. According to census data, historical documents and climatic information, during the last half century, especially the last 30 years, great changes have taken place in the eco-environment of this region. Such changes are mainly manifested in the temporal-spatial changes of water environment, deglaciation, permafrost reduction, vegetation degeneracy and desertification extent, which led to land capacity decreasing and river disconnecting. At present, desertification of the region is showing an accelerating tendency. This paper analyzes the present status of eco-environment degradation in this region supported by GIS and RS, as well as field investigation and indoor analysis, based on knowledge, multi-source data is gathered and the classification is worked out, deals with their natural and anthropogenic causes, and points out that in the last half century the desertification and environmental degradation of this region are mainly attributed to human activities under the background of regional climate changes. To halt further degradation of the environment of this region, great efforts should be made to use land resources rationally, develop advantages animal agriculture and protect the natural grassland.

Load–deflection behavior of RC beams strengthened with GFRP sheets subjected to different environmental conditions

Abstract: An investigation to examine the durability of reinforced concrete beams strengthened with glass fiber reinforced polymer (GFRP) laminates is performed. A total of 84 beam specimens were prepared for this study. The performance of these specimens was assessed through evaluating the flexural capacity and load–deflection relationships of the beams after placing them in different environments directly or indirectly with simulated field condition for a specified period of time. The specimens were divided into six categories which include controlled laboratory environment (unexposed category), outside environment (direct exposure to hot–dry field conditions), wet–dry normal water environment, wet–dry saline (NaCl) water environment, and wet–dry alkaline (NaOH) environment. Each category consisted of unstrengthened and strengthened beams. Furthermore, some of the specimens of the hot–dry field exposure were coated with protection paint against ultra violet (UV) rays. The specimens of different wet–dry environments were exposed to a time cycle of two weeks inside the solution and two weeks outside the solution. The test results carried out after 6, 12 and 24 months of exposure to different environmental conditions, show that none of the aforesaid environmental conditions have a noticeable influence on the flexural strength of the beams.

Development of an electrochemical antifouling system for seawater cooling pipelines of power plants using titanium

Abstract: Biofouling is the undesirable adhesion and development of microorganisms and macroorganisms in a water environment. An electrochemical antifouling system based on management of primary adhesion of microorganisms was developed employing titanium electrode for antifouling of seawater cooling pipes and marine infrastructures. The system consists of an electrochemical reaction-monitoring unit, a power control unit, and a potential/current remote monitoring and a control unit. Titanium plates and iron plates were used as the working and counter electrode, respectively. Field experiment was conducted in the seawater cooling pipeline system of a thermal power station. Four titanium electrodes with 1.0 m length and 3.0 m width were set in the seawater intake pit and current density was controlled at 50-100 mA/m(2). The electrode surface maintained clean conditions for 2 years. The average wet weight of fouling organisms on the titanium electrode surface was below 100 g/m(2) whereas the corresponding wet weight was above 10 kg/m(2) on the control surface. Using titanium as the electrode material, chlorine and hypochlorite are not generated. The developed electrochemical antifouling system provided an effective, environmentally friendly, and feasible techniques for remote operations.

Ethical issues in water use and sustainability

Abstract: The modern debate on water use and sustainability starts with the assumption that protecting the water environment is an ethical imperative, but rarely questions the basis for this viewpoint. This paper aims to identify some of the bases that could underlie such a position, seeking to locate value in the natural world beyond anthropocentric utilitarianism. Only when there is a clear basis for this discussion is it possible to discuss and resolve issues and conflicts that arise in the management of water: between present and future users, between human and non-human users, or between competing human users. We then attempt to develop a ‘water ethic’, parallel to the famous ‘land ethic’ of Aldo Leopold, in which we see water as the centre of the web of life in the landscape. Protecting water, its quality and its availability, for all present and future users, is one touchstone for the evaluation of environmental action and policy.

Water Management and N, P Losses From Paddy Fields in Southern Korea

Abstract: Assessment and control of nutrient losses from paddy fields is important to protect water quality of lakes and streams in Korea A four-year field study was carried out to investigate water management practices and losses of nitrogen (N) and phosphorus (P) in rice paddy irrigation fields in southern Korea The amount and water quality of rainfall, irrigation, surface drainage, and infiltration were measured and analyzed to estimate inputs and losses of N and P The observed irrigation amount surpassed consumptive use, and approximately 52 to 69 percent of inflow (precipitation plus irrigation) was lost to surface drainage Field data showed that significant amounts of irrigation water and rainfall were not effectively used for rice paddy culture Water quality data indicated that drainage from paddy fields could degrade the recipient water environment The nutrient balance indicated that significant amounts of nutrients (295 percent of total N and 86 percent of total P compared to input) were lost through surface drainage Furthermore, up to half the nutrient losses occurred during nonstorm periods The study results indicate that inadequate water management influences N and P losses during both storm and nonstorm periods Proper water management is required to reduce nutrient losses through surface drainage from paddy fields; this includes such measures as minimum irrigation, effective use of rainfall, adoption of proper drainage outlet structures, and minimized forced surface drainage