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1

Preliminary evaluation of hybrid electrochemical-thermochemical cycles for the production of hydrogen from water. [Lead oxide cycle  

Microsoft Academic Search

Water decomposition cycles, of the hybrid type, involving an electrochemical cell producing hydrogen, and an oxide, and a subsequent thermochemical process loop which liberates oxygen and regenerates the lower oxide (or metal), are evaluated. A prototype cycle based on the oxides of lead: HO + PbO H + PbO (electrolysis) PbO PbO + ¹\\/O (thermal decomposition) is presented. In principle,

Munger

1976-01-01

2

Water Cycle  

NSDL National Science Digital Library

4th Grade Science - Water Cycle Water Cycle two day interactive lesson plan. DAY 1: Welcome to the Water Cycle! Today we are going to be exploring and finding out more about the wonderful Water Cycle! For starters we are going to start with a movie, click the following link and watch the video and ...

Mrs. Staley

2009-11-09

3

Water Cycle  

NSDL National Science Digital Library

Water Cycle fun From water cycle Web Quest Links Introduction Task Process Evaluation Conclusion Resources Teacher Guide Introduction Luke Warm, a weather man, and you will help two baseball players understand why the big game might be rained out. You will explore the Water cycle and ...

Mrs. Terry

2009-04-03

4

A hybrid water-splitting cycle using copper sulfate and mixed copper oxides  

NASA Technical Reports Server (NTRS)

The Institute of Gas Technology has derived and developed a hybrid thermochemical water-splitting cycle based on mixed copper oxides and copper sulfate. Similar to other metal oxide-metal sulfate cycles that use a metal oxide to 'concentrate' electrolytically produced sulfuric acid, this cycle offers the advantage of producing oxygen (to be vented) and sulfur dioxide (to be recycled) in separate steps, thereby eliminating the need of another step to separate these gases. The conceptual process flow-sheet efficiency of the cycle promises to exceed 50%. It has been completely demonstrated in the laboratory with recycled materials. Research in the electrochemical oxidation of sulfur dioxide to produce sulfuric acid and hydrogen performed at IGT indicates that the cell performance goals of 200 mA/sq cm at 0.5 V will be attainable using relatively inexpensive electrode materials.

Schreiber, J. D.; Remick, R. J.; Foh, S. E.; Mazumder, M. M.

1980-01-01

5

Water Cycle  

NSDL National Science Digital Library

Students will use this short interactive activity to check their understanding on what they learned about the water cycle Do you drink the same water as your great grandparents did? Check this website then answer the following questions. COLLECTION 1. How many times does water go through the cycle? 2. Explain each part of the cycle and why it is important. 3. Construct a model or diagram based off the information from this ...

Lori Peterson

2009-09-28

6

Low-temperature, manganese oxide-based, thermochemical water splitting cycle  

PubMed Central

Thermochemical cycles that split water into stoichiometric amounts of hydrogen and oxygen below 1,000?°C, and do not involve toxic or corrosive intermediates, are highly desirable because they can convert heat into chemical energy in the form of hydrogen. We report a manganese-based thermochemical cycle with a highest operating temperature of 850?°C that is completely recyclable and does not involve toxic or corrosive components. The thermochemical cycle utilizes redox reactions of Mn(II)/Mn(III) oxides. The shuttling of Na+ into and out of the manganese oxides in the hydrogen and oxygen evolution steps, respectively, provides the key thermodynamic driving forces and allows for the cycle to be closed at temperatures below 1,000?°C. The production of hydrogen and oxygen is fully reproducible for at least five cycles. PMID:22647608

Xu, Bingjun; Bhawe, Yashodhan; Davis, Mark E.

2012-01-01

7

Use of oxides in thermochemical water-splitting cycles for solar heat sources. Recent results on the copper oxide cycle  

SciTech Connect

Additional results on the low temperature reactions for reforming CuO from Cu/sub 2/O are presented. These results pertain to the following reaction in the copper oxide cycle: I/sub 2/ + Cu/sub 2/O + Mg(OH)/sub 2/ = 2CuO + MgI/sub 2/(aq) + H/sub 2/O at 448/sup 0/K, ..delta..G/sup 0/ = -78.5. 4 references, 4 figures.

Jones, W.M.; Bowman, M.G.

1984-01-01

8

The Water Cycle  

NSDL National Science Digital Library

4th Grade Science Learn all about the Water Cycle! The Water Cycle: Water Storage Learn about Evaporation, Condensation, Precipitation, and Collection! The Water Cycle Here are some activites to learn about the water cycle. Hydrologic Cycle ...

Ms. Andrus

2007-10-12

9

Discovering the Water Cycle!  

NSDL National Science Digital Library

We will be learning about what the water cycle is and how it works. Resources! The Hydrologic Cycle: Water's journey through time The Water Cycle Thirstin's Water Cycle Activity Water evaporates from the surface Water Wonders These are a collection of websites that are going to help us in our journey of discovering what the water cycle is. ...

Miss Mortensen

2009-10-09

10

The Water Cycle  

NSDL National Science Digital Library

Students will learn the process of the water cycle. Alabama Course of Study: Science. Second Grade: Standard 9: Describe evaporation, condensation, and precipitation in the water cycle. What is the water cycle? On the worksheet provided, list the 4 parts of the water cycle. Between the parts draw a small picture to represent what is happening during this cycle. The Water Cycle See how we use the water in the water cycle. Thirstins Water Cycle Name 3 ways water changes form. This is an animated diagram of the Water Cycle Here is a ...

Mrs. Lopez

2009-07-09

11

THE WATER CYCLE/ CLOUDS  

NSDL National Science Digital Library

Students will learn about the water cycle and how it works. You will explore many resources to find out many new factors about the water cycle. What is the water cycle? National water cycle Name the 4 water parts of the water cycle? Weather wonders Where are 3 places that the water cycle exists- What happens after condensation? animated water cycle Name 4 types of clouds? What is the highest level cloud called? Which cloud is associated with powerful thunderstorms? Cloud Types What do clouds have to do with the water cycle? National water cycle What is ...

Ms.Brown

2009-04-06

12

The Water Cycle  

NSDL National Science Digital Library

Students will understand and explain parts of the water cycle. First watch the video to get a background about the water cycle: water cycle video Draw and explain the water cycle in your own words (include the terms: evaporation, condensation, precipitation, at least 3 bodies of water, the sun). Before reading the experiment record your predictions: If you put a small amount of water ...

Miss Amanda

2011-02-14

13

Water, Water Everywhere! Research the Water Cycle  

NSDL National Science Digital Library

Water, Water Everywhere! Research the Water Cycle asks students to conduct their own research on the water cycle (hydrologic cycle). Working collaboratively in small groups, students will research and write about the relationships between stages in the water cycle and the three states of matter relating to water. After completing this lesson, students will be prepared to create a model of the water cycle.

Regina Bale

2012-07-17

14

Redox cycle stability of mixed oxides used for hydrogen generation in the cyclic water gas shift process  

SciTech Connect

Graphical abstract: - Highlights: • Fe{sub 2}O{sub 3} modified with CaO, SiO{sub 2} and Al{sub 2}O{sub 3} was studied in cyclic water gas shift reactor. • For the first time stability of such oxides were tested for 100 redox cycles. • Optimally added oxides significantly improved the activity and the stability of Fe{sub 2}O{sub 3}. • Increased stability was attributed to the impediment of neck formation. - Abstract: Repeated cycles of the reduction of Fe{sub 3}O{sub 4} with reductive gas, e.g. hydrogen and subsequent oxidation of the reduced iron material with water vapor can be harnessed as a process for the production of pure hydrogen. The redox behavior of iron oxide modified with various amounts of SiO{sub 2}, CaO and Al{sub 2}O{sub 3} was investigated in the present study. The total amount of the additional metal oxides was always below 15 wt%. The samples were prepared by co-precipitation using urea hydrolysis method. The influence of various metal oxides on the hydrogen production capacity and the material stability was studied in detail in terms of temperature-programmed reduction (TPR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET analysis. Furthermore, the activity and the stability of the samples were tested in repeated reduction with diluted H{sub 2} and re-oxidation cycles with H{sub 2}O. The results indicate that combination of several oxides as promoter increases the stability of the iron oxide material by mitigating the sintering process. The positive influence of the oxides in stabilizing the iron oxide material is attributed to the impediment of neck formation responsible for sintering.

Datta, Pradyot, E-mail: pradyot.datta@gmail.com

2013-10-15

15

The Water Cycle  

NSDL National Science Digital Library

Today you will explore the water cycle. Please visit the following websites (in order!) to gather information about the water cycle. Fill out your Information Sheet as you go. 1. Water cycle story 2. Water Cycle--heat 3. animation (Make sure to read the captions at the bottom!) ...

Mrs. Hauck

2006-08-26

16

Water Cycle Webquest  

NSDL National Science Digital Library

Students are introduced to the Global Precipitation Measurement (GPM) satellite mission and its role in studying the water cycle. This webquest provides links to eight websites, allowing middle school students to explore the water cycle and its impacts on Earth's weather and climate. Through online videos and articles, students follow a water molecule through the cycle, discover the connection between the water cycle and global water/heat distribution, examine the role of solar energy, and assess the importance of fresh water.

17

Human Water Cycle  

NSDL National Science Digital Library

Students learn about the human water cycle, or how humans impact the water cycle by settling down in civilizations. Specifically, they learn how people obtain, use and dispose of water. Students also learn about shortages of treated, clean and safe water and learn about ways that engineers address this issue through water conservation and graywater recycling.

Integrated Teaching and Learning Program,

18

The Water Cycle  

NSDL National Science Digital Library

This demonstration introduces the concept of water phases and cycling to younger students through observation, drawing, and writing. They will be able to explain how the Earth's water supply is recycled, form a hypothesis as to how/why the water cycle works, and use writing and drawing to explain how the cycle works.

1998-01-01

19

The Water Cycle  

NSDL National Science Digital Library

What happens in each stage of the water cycle? First, watch this video to learn about each stage of the water cycle. video Next, click on this link to read more facts about each stages of the water cycle.

Ms. Baker

2011-04-18

20

Discover the Water Cycle!  

NSDL National Science Digital Library

This interactive tour of the water cycle allows students to follow a water molecule from a home's plumbing system as it follows different routes through the hydrologic cycle. Students learn about how water is used, treated, and returned to the natural environment where it can cycle through liquid, solid, and gas phases.

21

The Water Cycle  

NSDL National Science Digital Library

This interactive diagram of the water cycle invites students to click on a part of the cycle to get information about streamflow, surface runoff, freshwater storage, ground-water discharge, ground-water storage, infiltration, precipitation, snowmelt, runoff to streams, springs, condensation, evaporation, transpiration, water in the atmosphere, ice and snow, and oceans. A summary of the water cycle on a single webpage is also available as text with pictures in about fifty languages, text only in thirteen languages, or diagram only.

2007-12-12

22

The Water Cycle  

NSDL National Science Digital Library

The representation is a detailed, labeled diagram of the water cycle. Included in the representation are the major concepts of evaporation, precipitation and ground infiltration, as well as more advanced ideas such as evapotranspiration, and water storage. Above and below the diagram are several paragraphs that provide an introduction to the water cycle, a quick summary of the parts of the water cycle and information about global water distribution.

23

Amazon Water Cycle Roleplay  

NSDL National Science Digital Library

In this creative roleplay activity, learners will explore the various processes of the water cycle using movement, sound, and props to aid in comprehension. Learners will understand that water changes forms throughout the water cycle, and that this cycle runs continuously throughout all the cycles at the same time. This standards-based lesson, which is great for the classroom, camps, or afterschool programs, includes roleplay cards and ideas for props.

2012-06-26

24

Water Cycle Animation  

NSDL National Science Digital Library

The water cycle is Earth's natural mechanism for transporting and recycling water between the surface and the atmosphere. Through the processes of condensation, precipitation, infiltration, runoff, transpiration, and evaporation, water continuously travels from the atmosphere to the ground and back again. In this animation from NASA, users can observe the steps of the water cycle. The segment is fifty-two seconds in length.

25

The Water Cycle  

NSDL National Science Digital Library

Students will work with interactive internet resources to learn all about the water cycle. Fourth Grade Science Standard 1 Objective 2: Describe the water cycle. Locate examples of evaporation and condensation in the water cycle (e.g., water evaporates when heated and clouds or dew forms when vapor is cooled). Describe the processes of evaporation, condensation, and precipitation as they relate to the water cycle. Identify locations that hold water as it passes through the water cycle (e.g., oceans, atmosphere, fresh surface water, snow, ice, and ground water). Construct a model or diagram to show how water continuously moves through the water cycle over time. Describe how the water cycle relates to the water supply in your community. Web Quest Links Introduction Task Resources Evaluation Conclusion Teacher Guide Introduction Have you ever wondered how water gets from oceans, lakes, streams, or clouds into your glass? Check out the following links to learn more about it! TASK Start out by learning the concepts in this song from Bill Nye! Bill Nye the Science Guy- Water Cycle Jump Look ...

Ms. Lish

2009-04-06

26

THE WATER CYCLE  

NSDL National Science Digital Library

DESK Standard: Understand the processes of evaporation, condensation, and precipitation as they relate to the water cycle. Water Cycle Diagram DATES: You can begin this activity on October 16. You should complete it by October 20. OBJECTIVE: You have been learning about the water cycle in class. This activity gives you the chance to review some important vocabulary: evaporation condensation precipitation collection You will watch a short video and complete a water ...

Mr. Hughes

2006-02-18

27

The Water Cycle  

NSDL National Science Digital Library

This lesson was developed to give participants an understanding of Earth's water cycle. In this one-hour long activity, students participate in a webquest to learn about the water cycle, and then build a mini-model of the water cycle to observe how water moves through Earth's four systems. The activity uses the 5E instructional model and is part of the "Survivor Earth" series of one-hour lessons.

2014-08-18

28

The Water Cycle  

NSDL National Science Digital Library

Did you know that the water we use today is the same water found on Earth millions of years ago? The Earth constantly uses and recycles water in a process called the water cycle. In this lesson, learners explore the four phases of the water cycle. In the investigation Rain in a Jar, learners use hot water and ice to create condensation and a tiny cloud. In Making a Terrarium, learners create an ecosystem and water cycle by growing plants in a closed environment. Investigation spans several days.

New Jersey

2006-01-01

29

The Water Cycle  

NSDL National Science Digital Library

In this project you will learn about the different steps of the water cycle and what happens in each step. By the end of the project you will answer the essential question: How is rain made and why does it rain? There are many important steps that take place in the water cycle. Today we are going to learn about each step and the purpose of each step. Read The Water Cycle Information and think of the key steps in the water cycle. In this graphic organizer that I give you put the ...

Ms. Johnson

2009-10-22

30

Exploring the Water Cycle  

NSDL National Science Digital Library

In this lesson, students will learn about the water cycle and how energy from the sun and the force of gravity drive this cycle. The emphasis in this lesson will be on having students understand the processes that take place in moving water through Earth’s system.

31

The Water Cycle  

NSDL National Science Digital Library

The representation features a detailed six minute animated lesson about the major processes that move water between land, the ocean and the atmosphere, and convert water between states. This brief clip, (6:05-6:20 beginning with diagram of water cycle and ending with narration ?over and over again?), reinforces the idea that water continually moves between Earth's atmosphere and its land and water.

32

NOAA Water Cycle Game  

NSDL National Science Digital Library

The resource is a role-playing game in which students take on the role of a water molecule and travel through nine compartments of the water cycle to gain a better understanding for the true complexity of the movement of water.

33

Wet oxidation of concentrated wastewaters of paper mills for water cycle closing  

Microsoft Academic Search

Experimental research into wet oxidation of concentrated wastewaters from paper mills was undertaken. Evaporation and membrane concentrates from paper mills were selected as experimental objects. The aim of the wet oxidation of the paper mill concentrates was to reduce the concentration of organics and to improve biodegradability of the concentrates. The effect of temperature, pH and the influence of homogeneous

S Verenich; A Laari; J Kallas

2000-01-01

34

Water Cycle Model Building  

NSDL National Science Digital Library

The resource is a model building activity which uses simple materials to create a working representation of the water cycle. The resource also includes background information on the water cycle for the teacher, learning goals, alignment to National Science Education Standards and AAAS Benchmarks for Science Literacy, and assessment ideas, including questions for students. The resource includes suggested modifications for classrooms with limited supplies and/or with non-English speaking students.

35

The Water Cycle  

NSDL National Science Digital Library

We are about to enter into the world of science and discover many new things about the water cycle. Introduction Below is a list of websites I have created for you to go and do certain activities. I will give you directions of things I would like for you to do at each website. All About The Water Cycle Here is a game you can play. ...

Jenny

2008-11-17

36

Global water cycle  

NASA Technical Reports Server (NTRS)

This research is the MSFC component of a joint MSFC/Pennsylvania State University Eos Interdisciplinary Investigation on the global water cycle extension across the earth sciences. The primary long-term objective of this investigation is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates change on both global and regional scales. Significant accomplishments in the past year are presented and include the following: (1) water vapor variability; (2) multi-phase water analysis; (3) global modeling; and (4) optimal precipitation and stream flow analysis and hydrologic processes.

Robertson, Franklin; Goodman, Steven J.; Christy, John R.; Fitzjarrald, Daniel E.; Chou, Shi-Hung; Crosson, William; Wang, Shouping; Ramirez, Jorge

1993-01-01

37

Global water cycle  

NASA Technical Reports Server (NTRS)

The primary objective is to determine the scope and interactions of the global water cycle with all components of the Earth system and to understand how it stimulates and regulates changes on both global and regional scales. The following subject areas are covered: (1) water vapor variability; (2) multi-phase water analysis; (3) diabatic heating; (4) MSU (Microwave Sounding Unit) temperature analysis; (5) Optimal precipitation and streamflow analysis; (6) CCM (Community Climate Model) hydrological cycle; (7) CCM1 climate sensitivity to lower boundary forcing; and (8) mesoscale modeling of atmosphere/surface interaction.

Robertson, Franklin R.; Christy, John R.; Goodman, Steven J.; Miller, Tim L.; Fitzjarrald, Dan; Lapenta, Bill; Wang, Shouping

1991-01-01

38

The Other Water Cycle  

NSDL National Science Digital Library

For students who have already been introduced to the water cycle, this lesson is intended as a logical follow-up. Students learn about human impacts on the water cycle that create a pathway for pollutants beginning with urban development and joining the natural water cycle as surface runoff. The extent of surface runoff in an area depends on the permeability of the materials in the ground. Permeability is the degree to which water or other liquids are able to flow through a material. Different substances such as soil, gravel, sand and asphalt have varying levels of permeability. In this lesson, along with the associated activity, students learn about permeability and compare the permeability of several different materials for the purpose of engineering landscape drainage systems.

Engineering K-PhD Program,

39

Reaction experiments for thermochemical water-splitting. [Classes of cycles: metal-metal oxide; metal oxide-metal hydroxide; metal oxide-metal sulfate; metal-metal halide; metal oxide-metal halide  

Microsoft Academic Search

Almost all known pure thermochemical hydrogen production cycles can be grouped into five generic classes, each involving either a metal oxide or a metal halide as an intermediate. In general, those cycles with the highest-temperature endothermic reactions and the least number of reactions are the most efficient. This is expected because thermochemical cycles are special types of heat engines. The

J. Gahimer; J. Pangborn; S. Foh; M. Mazumder; R. Stotz

1976-01-01

40

The Water Cycle  

NSDL National Science Digital Library

This site provides information about precipitation, evaporation, condensation, surface runoff, infiltration and transpiration, which are all part of the water cycle, a complex process that not only gives us water to drink and fish to eat, but also weather patterns that help grow our crops. The site has four sections. The introduction presents the overall concept while the second section covers each of the six parts of the cycle in detail. In the third part, The Cycle, the dynamic process is stressed and a diagram is included. Cloud Formation is the final section and it covers factors that control the size and shape of clouds such as heat, seasons, mountain ranges, bodies of water, volcanic eruptions, and even global warming. In addition, cloud nomenclature is discussed with an explanation of the advent of such cloud names as cumulonimbus, nimbostratus, cirrocumulus, and altostratus.

41

Make a Water Cycle Wristband  

NSDL National Science Digital Library

In this activity on page 4 of the PDF, learners thread colored beads onto string. Each beach represent a process of the water cycle. This resource contains a diagram showing the water cycle and provides definitions for related keywords.

American Chemical Society

2013-07-08

42

GEOSS Water Cycle Integrator  

NASA Astrophysics Data System (ADS)

It is critically important to recognize and co-manage the fundamental linkages across the water-dependent domains; land use, including deforestation; ecosystem services; and food-, energy- and health-securities. Sharing coordinated, comprehensive and sustained observations and information for sound decision-making is a first step; however, to take full advantage of these opportunities, we need to develop an effective collaboration mechanism for working together across different disciplines, sectors and agencies, and thereby gain a holistic view of the continuity between environmentally sustainable development, climate change adaptation and enhanced resilience. To promote effective multi-sectoral, interdisciplinary collaboration based on coordinated and integrated efforts, the intergovernmental Group on Earth Observations (GEO) is implementing the Global Earth Observation System of Systems (GEOSS). A component of GEOSS now under development is the "GEOSS Water Cycle Integrator (WCI)", which integrates Earth observations, modeling, data and information, management systems and education systems. GEOSS/WCI sets up "work benches" by which partners can share data, information and applications in an interoperable way, exchange knowledge and experiences, deepen mutual understanding and work together effectively to ultimately respond to issues of both mitigation and adaptation. (A work bench is a virtual geographical or phenomenological space where experts and managers collaborate to use information to address a problem within that space). GEOSS/WCI enhances the coordination of efforts to strengthen individual, institutional and infrastructure capacities, especially for effective interdisciplinary coordination and integration. GEO has established the GEOSS Asian Water Cycle Initiative (AWCI) and GEOSS African Water Cycle Coordination Initiative (AfWCCI). Through regional, inter-disciplinary, multi-sectoral integration and inter-agency coordination in Asia and Africa, GEOSS/WCI is now leading to effective actions and public awareness in support of water security and sustainable development.

Koike, Toshio; Lawford, Richard; Cripe, Douglas

2013-04-01

43

GEOSS Water Cycle Integrator  

NASA Astrophysics Data System (ADS)

It is critically important to recognize and co-manage the fundamental linkages across the water-dependent domains; land use, including deforestation; ecosystem services; and food-, energy- and health-securities. Sharing coordinated, comprehensive and sustained observations and information for sound decision-making is a first step; however, to take full advantage of these opportunities, we need to develop an effective collaboration mechanism for working together across different disciplines, sectors and agencies, and thereby gain a holistic view of the continuity between environmentally sustainable development, climate change adaptation and enhanced resilience. To promote effective multi-sectoral, interdisciplinary collaboration based on coordinated and integrated efforts, the Global Earth Observation System of Systems (GEOSS) is now developing a "GEOSS Water Cycle Integrator (WCI)", which integrates "Earth observations", "modeling", "data and information", "management systems" and "education systems". GEOSS/WCI sets up "work benches" by which partners can share data, information and applications in an interoperable way, exchange knowledge and experiences, deepen mutual understanding and work together effectively to ultimately respond to issues of both mitigation and adaptation. (A work bench is a virtual geographical or phenomenological space where experts and managers collaborate to use information to address a problem within that space). GEOSS/WCI enhances the coordination of efforts to strengthen individual, institutional and infrastructure capacities, especially for effective interdisciplinary coordination and integration. GEO has established the GEOSS Asian Water Cycle Initiative (AWCI) and GEOSS African Water Cycle Coordination Initiative (AfWCCI). Through regional, inter-disciplinary, multi-sectoral integration and inter-agency coordination in Asia and Africa, GEOSS/WCI is now leading to effective actions and public awareness in support of water security and sustainable development.

Koike, T.; Lawford, R. G.; Cripe, D.

2012-12-01

44

Studies of thermochemical water-splitting cycles  

NASA Technical Reports Server (NTRS)

Higher temperatures and more isothermal heat profiles of solar heat sources are developed. The metal oxide metal sulfate class of cycles were suited for solar heat sources. Electrochemical oxidation of SO2 and thermochemical reactions are presented. Electrolytic oxidation of sulfur dioxide in dilute sulfuric acid solutions were appropriate for metal oxide metal sulfate cycles. The cell voltage at workable current densities required for the oxidation of SO2 was critical to the efficient operation of any metal oxide metal sulfate cycle. A sulfur dioxide depolarized electrolysis cell for the splitting of water via optimization of the anode reaction is discussed. Sulfuric acid concentrations of 30 to 35 weight percent are preferred. Platinized platinum or smooth platinum gave the best anode kinetics at a given potential of the five materials examined.

Remick, R. J.; Foh, S. E.

1980-01-01

45

Fun with the Water Cycle  

NSDL National Science Digital Library

Science - 4th Grade Students will understand that water changes state as it moves through the water cycle. Note: this lesson plan can easily take more than one day for students to complete. Materials needed: Computers, frisbee, 2 clear plastic cups, tape, graduated cylinder, water, condensation data worksheet, 2 matches, 1 clear empty 2-liter pop bottle, 1/2 cup of warm water, flashlight, measuring cup 1. Click on the link below, then click "Thristin's Water Cycle: Water". Watch the short video about the water cycle. ...

Ms. Wirthlin

2009-11-16

46

The water cycle for kids  

USGS Publications Warehouse

The U.S. Geological Survey (USGS) and the Food and Agriculture Organization of the United Nations (FAO) have created a water-cycle diagram for use in elementary and middle schools. The diagram is available in many languages. This diagram is part of the USGS's Water Science School, in which the water cycle is described in detail.

Neno, Stephanie; Morgan, Jim; Zonolli, Gabriele; Perlman, Howard; Gonthier, Gerard

2013-01-01

47

Weather and The Water Cycle  

NSDL National Science Digital Library

Students will be able to do activities dealing with weather and water cycles. Learn what makes weather wet and wild, forcast and predict weather. Webweather For Kids Learn about tornadoes and hurricanes. Kidstorm Learn about the water cycles. water Cycles Now click on the following link: Interactive weather maker 1. How much change in temperature is needed to make it snow? On the right side of the page click on Weather Detective Web Quest. Follow the ...

Mrs. Merritt

2005-10-15

48

Biological water oxidation.  

PubMed

Photosystem II (PSII), a multisubunit pigment-protein supercomplex found in cyanobacteria, algae, and plants, catalyzes a unique reaction in nature: the light-driven oxidation of water. Remarkable recent advances in the structural analysis of PSII now give a detailed picture of the static supercomplex on the molecular level. These data provide a solid foundation for future functional studies, in particular the mechanism of water oxidation and oxygen release. The catalytic core of the PSII is a tetramanganese-calcium cluster (Mn?O?Ca), commonly referred to as the oxygen-evolving complex (OEC). The function of the OEC rests on its ability to cycle through five metastable states (Si, i = 0-4), transiently storing four oxidizing equivalents, and in so doing, facilitates the four electron water splitting reaction. While the latest crystallographic model of PSII gives an atomic picture of the OEC, the exact connectivity within the inorganic core and the S-state(s) that the X-ray model represents remain uncertain. In this Account, we describe our joint experimental and theoretical efforts to eliminate these ambiguities by combining the X-ray data with spectroscopic constraints and introducing computational modeling. We are developing quantum chemical methods to predict electron paramagnetic resonance (EPR) parameters for transition metal clusters, especially focusing on spin-projection approaches combined with density functional theory (DFT) calculations. We aim to resolve the geometric and electronic structures of all S-states, correlating their structural features with spectroscopic observations to elucidate reactivity. The sequence of manganese oxidations and concomitant charge compensation events via proton transfer allow us to rationalize the multielectron S-state cycle. EPR spectroscopy combined with theoretical calculations provides a unique window into the tetramangenese complex, in particular its protonation states and metal ligand sphere evolution, far beyond the scope of static techniques such as X-ray crystallography. This approach has led, for example, to a detailed understanding of the EPR signals in the S?-state of the OEC in terms of two interconvertible, isoenergetic structures. These two structures differ in their valence distribution and spin multiplicity, which has important consequences for substrate binding and may explain its low barrier exchange with solvent water. New experimental techniques and innovative sample preparations are beginning to unravel the complex sequence of substrate uptake/inclusion, which is coupled to proton release. The introduction of specific site perturbations, such as replacing Ca²? with Sr²?, provides discrete information about the ligand environment of the individual Mn ions. In this way, we have identified a potential open coordination site for one Mn center, which may serve as a substrate binding site in the higher S-states, such as S? and S?. In addition, we can now monitor the binding of the substrate water in the lower S-states (S? and S?) using new EPR-detected NMR spectroscopies. These studies provided the first evidence that one of the substrates is subsumed into the complex itself and forms an oxo-bridge between two Mn ions. This result places important new restrictions on the mechanism of O-O bond formation. These new insights from nature's water splitting catalyst provide important criteria for the rational design of bioinspired synthetic catalysts. PMID:23506074

Cox, Nicholas; Pantazis, Dimitrios A; Neese, Frank; Lubitz, Wolfgang

2013-07-16

49

Water Cycle in a Bag  

NSDL National Science Digital Library

In this activity, learners create a biosphere in a baggie. Learners add soil, seeds and a little water in a ziplock bag, tape the bag to a sunny window and observe a microcosm of the water cycle (hydrologic cycle) that sustains life on Earth. This resource includes tips for using this activity with older children as well as useful web links.

2012-06-26

50

The NEWS Water Cycle Climatology  

NASA Technical Reports Server (NTRS)

NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the first phase of the NEWS Water and Energy Cycle Climatology project was to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project was a multi-institutional collaboration with more than 20 active contributors. This presentation will describe the results of the water cycle component of the first phase of the project, which include seasonal (monthly) climatologies of water fluxes over land, ocean, and atmosphere at continental and ocean basin scales. The requirement of closure of the water budget (i.e., mass conservation) at various scales was exploited to constrain the flux estimates via an optimization approach that will also be described. Further, error assessments were included with the input datasets, and we examine these in relation to inferred uncertainty in the optimized flux estimates in order to gauge our current ability to close the water budget within an expected uncertainty range.

Rodell, Matthew; Beaudoing, Hiroko Kato; L'Ecuyer, Tristan; William, Olson

2012-01-01

51

The Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

The goal of the Water cycle Solutions Network is to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend research results to augment decision support tools and meet national needs. WaterNet will engage relevant NASA water cycle research resources and community-of-practice organizations, to develop what we term an "actionable database" that can be used to communicate and connect water cycle research results (WCRs) towards the improvement of water-related Decision Support Tools (DSTs). An actionable database includes enough sufficient knowledge about its nodes and their heritage so that connections between these nodes are identifiable and robust. Recognizing the many existing highly valuable water-related science and application networks, we will focus the balance of our efforts on enabling their interoperability in a solutions network context. We will initially focus on identification, collection, and analysis of the two end points, these being the WCRs and water related DSTs. We will then develop strategies to connect these two end points via innovative communication strategies, improved user access to NASA resources, improved water cycle research community appreciation for DST requirements, improved policymaker, management and stakeholder knowledge of NASA research and application products, and improved identification of pathways for progress. Finally, we will develop relevant benchmarking and metrics, to understand the network's characteristics, to optimize its performance, and to establish sustainability. The WaterNet will deliver numerous pre-evaluation reports that will identify the pathways for improving the collective ability of the water cycle community to routinely harness WCRs that address crosscutting water cycle challenges.

Houser, P.; Belvedere, D.; Imam, B.; Schiffer, R.; Schlosser, C.; Gupta, H.; Welty, C.; Vörösmarty, C.; Matthews, D.; Lawford, R.

2006-12-01

52

The Mars water cycle  

NASA Technical Reports Server (NTRS)

A model has been developed to test the hypothesis that the observed seasonal and latitudinal distribution of water on Mars is controlled by the sublimation and condensation of surface ice deposits in the Arctic and Antarctic, and the meridional transport of water vapor. Besides reproducing the observed water vapor distribution, the model correctly reproduces the presence of a large permanent ice cap in the Arctic and not in the Antarctic. No permanent ice reservoirs are predicted in the temperate or equatorial zones. Wintertime ice deposits in the Arctic are shown to be the source of the large water vapor abundances observed in the Arctic summertime, and the moderate water vapor abundances in the northern temperate region. Model calculations suggest that a year without dust storms results in very little change in the water vapor distribution. The current water distribution appears to be the equilibrium distribution for present atmospheric conditions.

Davies, D. W.

1981-01-01

53

The Water Cycle  

NSDL National Science Digital Library

This is a Macromedia Flash Player enhanced website developed by the EPA. The website is divided into four sections: rain, water storage, vapor, and clouds. In the Rain section, students can discover the forms of precipitation and why it occurs. Through the short, interactive module, individuals can learn about the development of aquifers, transpiration, and condensation. This is a great website for young students to grasp the connections between different forms of water.

54

Water 2: The Hydrologic Cycle  

NSDL National Science Digital Library

This video looks at how water is provided for our use through the hydrologic cycle. It also explains how global climate change disturbs the storage of water in the various global compartments. This video is part of the Sustainability Learning Suites, made possible in part by a grant from the National Science Foundation. See 'Learn more about this resource' for Learning Objectives and Activities.

2012-12-19

55

The Water Cycle: Infiltration  

NSDL National Science Digital Library

This site provides a discussion of the downward movement, or infiltration, of water from the surface into soil or porous rock. Graphics illustrate the processes affecting infiltration, including precipitation, soil characteristics and saturation, land cover, slope, and evapotranspiration. Links to additional sources of information are also provided.

56

Copper-catalyzed hydroquinone oxidation and associated redox cycling of copper under conditions typical of natural saline waters.  

PubMed

A detailed kinetic model has been developed to describe the oxidation of Cu(I) by O2 and the reduction of Cu(II) by 1,4-hydroquinone (H2Q) in the presence of O2 in 0.7 M NaCl solution over a pH range of 6.5-8.0. The reaction between Cu(I) and O2 is shown to be the most important pathway in the overall oxidation of Cu(I), with the rate constant for this oxidation process increasing with an increasing pH. In 0.7 M NaCl solutions, Cu(II) is capable of catalyzing the oxidation of H2Q in the presence of O2 with the monoanion, HQ(-), the kinetically active hydroquinone form, reducing Cu(II) with an intrinsic rate constant of (5.0 ± 0.4) × 10(7) M(-1) s(-1). Acting as a chain-propagating species, the deprotonated semiquinone radical (SQ(•)?(-)) generated from both the one-electron oxidation of H2Q and the one-electron reduction of 1,4-benzoquinone (BQ) also reacts rapidly with Cu(II) and Cu(I), with the same rate constant of (2.0 ± 0.5) × 10(7) M(-1) s(-1). In addition to its role in reformation of Cu(II) via continuous oxidation of Cu(I), O2 rapidly removes SQ(•)?(-), resulting in the generation of O2(•)?(-). Agreement between half-cell reduction potentials of different redox couples provides confirmation of the veracity of the proposed model describing the interactions of copper and quinone species in circumneutral pH saline solutions. PMID:23796190

Yuan, Xiu; Pham, A Ninh; Miller, Christopher J; Waite, T David

2013-08-01

57

Synthetic water-oxidation catalysts for artificial photosynthetic water oxidation  

Microsoft Academic Search

This review focuses primarily on homogeneous catalysts for the oxidation of water, but does include selected heterogeneous systems. It does not attempt to summarize all chemistry related to systems that are capable of oxidizing water. In particular, heterogeneous catalysts that have no direct relevance to understanding the WOC [water-oxidizing complex] are not discussed in detail. Neither are nonbiomimetic systems for

W. Ruettinger; G. Charles Dismukes

1997-01-01

58

Molecular water oxidation catalyst  

DOEpatents

A dimeric composition of the formula: ##STR1## wherein L', L", L'", and L"" are each a bidentate ligand having at least one functional substituent, the ligand selected from bipyridine, phenanthroline, 2-phenylpyridine, bipyrimidine, and bipyrazyl and the functional substituent selected from carboxylic acid, ester, amide, halogenide, anhydride, acyl ketone, alkyl ketone, acid chloride, sulfonic acid, phosphonic acid, and nitro and nitroso groups. An electrochemical oxidation process for the production of the above functionally substituted bidentate ligand diaqua oxo-bridged ruthenium dimers and their use as water oxidation catalysts is described.

Gratzel, Michael (St. Sulpice, CH); Munavalli, Shekhar (Bel Air, MD); Pern, Fu-Jann (Lakewood, CO); Frank, Arthur J. (Lakewood, CO)

1993-01-01

59

Natural and Urban "Stormwater" Water Cycle Models  

NSDL National Science Digital Library

Students apply their understanding of the natural water cycle and the urban "stormwater" water cycle, as well as the processes involved in both cycles to hypothesize how the flow of water is affected by altering precipitation. Student groups consider different precipitation scenarios based on both intensity and duration. Once hypotheses and specific experimental steps are developed, students use both a natural water cycle model and an urban water cycle model to test their hypotheses. To conclude, students explain their results, tapping their knowledge of both cycles and the importance of using models to predict water flow in civil and environmental engineering designs. The natural water cycle model is made in advance by the teacher, using simple supplies; a minor adjustment to the model easily turns it into the urban water cycle model.

2014-09-18

60

Catalytic water oxidation: Rugged water-oxidation anodes  

Microsoft Academic Search

The efficient catalytic oxidation of water to dioxygen in the solid state is one of the challenges to be overcome to build sun-driven and\\/or electrocatalytic water-splitting devices. Now, an effective water-oxidation hybrid catalyst system has been made by attaching a ruthenium-polyoxometallate complex to a carbon nanotube.

Antoni Llobet

2010-01-01

61

Simulating the urban water and contaminant cycle  

Microsoft Academic Search

This paper presents the water and contaminant daily simulation model of the total water cycle, called UVQ. The model has been developed to provide a means for rapidly assessing the impacts of conventional and non-conventional urban water supply, stormwater and wastewater development options on the total water cycle. UVQ provides a valuable insight into the viability of prospective alternative water

V. G. Mitchell; C. Diaper

2006-01-01

62

EMERGING CONTAMINANTS IN THE DRINKING WATER CYCLE  

EPA Science Inventory

PRESENTATION OUTLINE: I. General overview of the water cycle; II. USEPA and USGS Research; a. Wastewater treatment plant (WWTP) effluents and downstream surface waters; b. Groundwater down gradient from WW lagoon; c. Source and finished water fro...

63

GEWEX Conference considers global water cycle  

Microsoft Academic Search

The recent Intergovernmental Panel on Climate Change (IPCC) assessment of greenhouse warming scenarios suggests an intensification (increase in cycling rates) of the global hydrological cycle over the next several decades. Accurate incorporation of water and energy cycles can substantially improve the predictive capability of global climate models. The Global Energy and Water Experiment (GEWEX) Science Conference offered an opportunity to

S. Ichtiaque Rasool

1997-01-01

64

The Water Cycle in Volusia County  

USGS Publications Warehouse

Earth's water is always in motion. The water cycle, also known as the hydrologic cycle, describes the continuous movement of water on, above, and below the Earth's surface. This fact sheet provides information about how much water moves into and out of Volusia County, and where it is stored. It also illustrates the seasonal variation in water quantity and movement using data from some of the hydrologic data collection sites in or near Volusia County, Florida.

German, Edward R.

2009-01-01

65

Synthetic water-oxidation catalysts for artificial photosynthetic water oxidation  

SciTech Connect

This review focuses primarily on homogeneous catalysts for the oxidation of water, but does include selected heterogeneous systems. It does not attempt to summarize all chemistry related to systems that are capable of oxidizing water. In particular, heterogeneous catalysts that have no direct relevance to understanding the WOC [water-oxidizing complex] are not discussed in detail. Neither are nonbiomimetic systems for artificial photosynthesis or water-splitting in its elements discussed. However, a list of some of the recent references in these areas can be found in section X (Nonbiomimetic Water Oxidation Catalysts). The authors will first give a brief summary of the current view of the photosynthetic WOC and its functionality, followed by analysis of the thermodynamic and kinetic constraints for water-oxidation that have to be overcome by any catalyst. Since manganese is the metal that performs this reaction in the WOC, manganese catalysts will be discussed first, followed by other transition metals, particularly ruthenium. In the final section the authors summarize the principles of reactivity learned from theory and existing models that will guide one toward synthesis of better catalysts in the future. This review does not attempt to summarize manganese chemistry relevant to nonfunctional (structural) models of the WOC, which has been reviewed recently. Water-oxidation catalysts are intrinsically important in their own right, independent of possible biological relevance. They have direct applications as catalysts in artificial photosynthetic systems for the splitting of water that could be used in future fuel cells for the generation of electricity. 133 refs.

Ruettinger, W.; Dismukes, G.C. [Princeton Univ., NJ (United States)] [Princeton Univ., NJ (United States)

1997-01-01

66

Creative Writing and the Water Cycle.  

ERIC Educational Resources Information Center

Uses the story "The Life of a Drop of Water" to initiate a creative writing activity and teach about the water cycle. Attempts to stimulate students' understanding of a scientific concept by using their imaginations. (YDS)

Young, Rich; Virmani, Jyotika; Kusek, Kristen M.

2001-01-01

67

Getting up to Speed: The Water Cycle and Water Conservation  

NSDL National Science Digital Library

This is an introduction to a module on water conservation. It presents the concepts of limited supply, the water cycle, and the impact by and on populations. It gives an overview of water conservation and what would happen without it.

68

Modeling the Martian seasonal water cycle  

Microsoft Academic Search

Ever since the observations of Percival Lowell, the annual cycle of Martian water has been a fascinating topic in planetary exploration. Observations by the Viking Orbiter, supplemented by Earth-based microwave and infrared observations, have given us a reasonable picture of this cycle. We are now also able to model the cycle using our Mars Climate Model, a simplified atmospheric general

Howard Houben; Robert M. Haberle; Richard E. Young; Aaron P. Zent

1997-01-01

69

Water Cycle Missions for the Next Decade  

NASA Astrophysics Data System (ADS)

The global water cycle describes the circulation of water as a vital and dynamic substance in its liquid, solid, and vapor phases as it moves through the atmosphere, oceans and land. Life in its many forms exists because of water, and modern civilization depends on learning how to live within the constraints imposed by the availability of water. The scientific challenge posed by the need to observe the global water cycle is to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The vision to address that challenge is a series of Earth observation missions that will measure the states, stocks, flows, and residence times of water on regional to global scales followed by a series of coordinated missions that will address the processes, on a global scale, that underlie variability and changes in water in all its three phases. The accompanying societal challenge is to foster the improved use of water data and information as a basis for enlightened management of water resources, to protect life and property from effects of extremes in the water cycle. A major change in thinking about water science that goes beyond its physics to include its role in ecosystems and society is also required. Better water-cycle observations, especially on the continental and global scales, will be essential. Water-cycle predictions need to be readily available globally to reduce loss of life and property caused by water-related natural hazards. Building on the 2007 Earth Science Decadal Survey, NASA's Plan for a Climate-Centric Architecture for Earth Observations and Applications from Space , and the 2012 Chapman Conference on Remote Sensing of the Terrestrial Water Cycle, a workshop was held in April 2013 to gather wisdom and determine how to prepare for the next generation of water cycle missions in support of the second Earth Science Decadal Survey. This talk will present the outcomes of the workshop including the intersection between science questions, technology readiness and satellite design optimization. A series of next-generation water cycle mission working groups were proposed and white papers, designed to identify capacity gaps and inform NASA were developed. The workshop identified several visions for the next decade of water cycle satellite observations, and developed a roadmap and action plan for developing the foundation for these missions. Achieving this outcome will result in optimized community investments and better functionality of these future missions, and will help to foster broader range of scientists and professionals engaged in water cycle observation planning and development around the country, and the world.

Houser, P. R.

2013-12-01

70

ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION  

EPA Science Inventory

This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. his information is provided to assist remedial project managers, contractors ...

71

ENGINEERING BULLETIN: SUPERCRITICAL WATER OXIDATION  

EPA Science Inventory

This engineering bulletin presents a description and status of supercritical water oxidation technology, a summary of recent performance tests, and the current applicability of this emerging technology. This information is provided to assist remedial project managers, contractors...

72

Water Cycle. K-6 Science Curriculum.  

ERIC Educational Resources Information Center

Water Cycle is one of the units of a K-6 unified science curriculum program. The unit consists of four organizing sub-themes: (1) atmosphere (highlighting the processes of evaporation, condensation, convection, wind movement and air pollution); (2) water (examining the properties of liquids, water distribution, use, and quality, and the water…

Blueford, J. R.; And Others

73

Water oxidation by an electropolymerized catalyst on derivatized mesoporous metal oxide electrodes.  

PubMed

A general electropolymerization/electro-oligomerization strategy is described for preparing spatially controlled, multicomponent films and surface assemblies having both light harvesting chromophores and water oxidation catalysts on metal oxide electrodes for applications in dye-sensitized photoelectrosynthesis cells (DSPECs). The chromophore/catalyst ratio is controlled by the number of reductive electrochemical cycles. Catalytic rate constants for water oxidation by the polymer films are similar to those for the phosphonated molecular catalyst on metal oxide electrodes, indicating that the physical properties of the catalysts are not significantly altered in the polymer films. Controlled potential electrolysis shows sustained water oxidation over multiple hours with no decrease in the catalytic current. PMID:24735242

Ashford, Dennis L; Lapides, Alexander M; Vannucci, Aaron K; Hanson, Kenneth; Torelli, Daniel A; Harrison, Daniel P; Templeton, Joseph L; Meyer, Thomas J

2014-05-01

74

Natural and Urban "Stormwater" Water Cycles  

NSDL National Science Digital Library

Through an overview of the components of the hydrologic cycle and the important roles they play in the design of engineered systems, students' awareness of the world's limited fresh water resources is heightened. The hydrologic cycle affects everyone and is the single most critical component to life on Earth. Students examine in detail the water cycle components and phase transitions, and then learn how water moves through the human-made urban environment. This urban "stormwater" water cycle is influenced by the pervasive existence of impervious surfaces that limit the amount of infiltration, resulting in high levels of stormwater runoff, limited groundwater replenishment and reduced groundwater flow. Students show their understanding of the process by writing a description of the path of a water droplet through the urban water cycle, from the droplet's point of view. The lesson lays the groundwork for rest of the unit, so students can begin to think about what they might do to modify the urban "stormwater" water cycle so that it functions more like the natural water cycle. A PowerPoint® presentation and handout are provided.

2014-09-18

75

The Water Cycle - Back and Forth  

NSDL National Science Digital Library

This is the first of three lessons on the water cycle. Students create a model (drawing) after learning the parts of the water cycle. The drawing will be in their science notebooks and will be something they will build on in future lessons. At the end of the unit they will display larger finished models. Vocabulary words are defined and connected to a model of melting ice in a water bottle.

Maribel Magdaleno

2012-07-17

76

Modelling the urban water cycle  

Microsoft Academic Search

Current urban water management practices aim to remove stormwater and wastewater efficiently from urban areas. An alternative approach is to consider stormwater and wastewater as a potential resource substitute for a portion of the water imported via the reticulated supply system. A holistic view of urban water resources provides the framework for the evaluation of the demand for water supply,

V. G. Mitchell; R. G. Mein; T. A. Mcmahon

2001-01-01

77

Evolution of the Martian water cycle  

Microsoft Academic Search

The current Martian water cycle is extremely asymmetric, with large amounts of vapor subliming off a permanent north polar water ice cap in northern summer, but with no apparent major source of water vapor in the southern hemisphere. Detailed simulations of this process with a three-dimensional circulation model indicate that the summertime interhemispheric exchange (Hadley cell) is very much stronger

H. Houben; R. M. Haberle; R. E. Young; A. P. Zent

1997-01-01

78

Deep water cycle: Mantle hydration  

NASA Astrophysics Data System (ADS)

The fate of water that enters the mantle within subducting slabs is unclear. Laboratory experiments indicate that subducted crust can transport large amounts of water into the deep Earth, and the lower mantle may become more hydrated over time.

Nishi, Masayuki

2015-01-01

79

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

This paper presents an approach to measuring all major components of the water cycle from space. Key elements of the global water cycle are discussed in terms of the storage of water-in the ocean, air, cloud and precipitation, in soil, ground water, snow and ice, and in lakes and rivers, and in terms of the global fluxes of water between these reservoirs. Approaches to measuring or otherwise evaluating the global water cycle are presented, and the limitations on known accuracy for many components of the water cycle are discussed, as are the characteristic spatial and temporal scales of the different water cycle components. Using these observational requirements for a global water cycle observing system, an approach to measuring the global water cycle from space is developed. The capabilities of various active and passive microwave instruments are discussed, as is the potential of supporting measurements from other sources. Examples of space observational systems, including TRMM/GPM precipitation measurement, cloud radars, soil moisture, sea surface salinity, temperature and humidity profiling, other measurement approaches and assimilation of the microwave and other data into interpretative computer models are discussed to develop the observational possibilities. The selection of orbits is then addressed, for orbit selection and antenna size/beamwidth considerations determine the sampling characteristics for satellite measurement systems. These considerations dictate a particular set of measurement possibilities, which are then matched to the observational sampling requirements based on the science. The results define a network of satellite instrumentation systems, many in low Earth orbit, a few in geostationary orbit, and all tied together through a sampling network that feeds the observations into a data-assimilative computer model.

Hildebrand, P. H.

2004-01-01

80

Integrated urban water cycle management: the UrbanCycle model.  

PubMed

Integrated urban water cycle management presents a new framework in which solutions to the provision of urban water services can be sought. It enables new and innovative solutions currently constrained by the existing urban water paradigm to be implemented. This paper introduces the UrbanCycle model. The model is being developed in response to the growing and changing needs of the water management sector and in light of the need for tools to evaluate integrated watercycle management approaches. The key concepts underpinning the UrbanCycle model are the adoption of continuous simulation, hierarchical network modelling, and the careful management of computational complexity. The paper reports on the integration of modelling capabilities across the allotment, and subdivision scales, enabling the interactions between these scales to be explored. A case study illustrates the impacts of various mitigation measures possible under an integrated water management framework. The temporal distribution of runoff into ephemeral streams from a residential allotment in Western Sydney is evaluated and linked to the geomorphic and ecological regimes in receiving waters. PMID:16445168

Hardy, M J; Kuczera, G; Coombes, P J

2005-01-01

81

Observing the Global Water Cycle from Space  

NASA Technical Reports Server (NTRS)

This paper presents an approach to measuring all major components of the water cycle from space. The goal of the paper is to explore the concept of using a sensor-web of satellites to observe the global water cycle. The details of the required measurements and observation systems are therefore only an initial approach and will undergo future refinement, as their details will be highly important. Key elements include observation and evaluation of all components of the water cycle in terms of the storage of water-in the ocean, air, cloud and precipitation, in soil, ground water, snow and ice, and in lakes and rivers-and in terms of the global fluxes of water between these reservoirs. For each component of the water cycle that must be observed, the appropriate temporal and spatial scales of measurement are estimated, along with the some of the frequencies that have been used for active and passive microwave observations of the quantities. The suggested types of microwave observations are based on the heritage for such measurements, and some aspects of the recent heritage of these measurement algorithms are listed. The observational requirements are based on present observational systems, as modified by expectations for future needs. Approaches to the development of space systems for measuring the global water cycle can be based on these observational requirements.

Hildebrand, Peter H.; Houser, Paul; Schlosser, C. Adam

2003-01-01

82

Life Cycle Assessment of Water Recycling Technology  

Microsoft Academic Search

Environmental performance of different water recycling technologies is compared on the basis of the associated potential environmental impacts using the technique of Life Cycle Assessment (LCA). The LCA method is used here to support decision making in water recycling in terms of (1) comparison and selection of suitable technology and (2) identification of opportunities to enhance the environmental performance of

N. Tangsubkul; P. Beavis; S. J. Moore; S. Lundie; T. D. Waite

2005-01-01

83

CLOSED-CYCLE WATER-BOILER REACTOR  

Microsoft Academic Search

The design and characteristics of a liquid homogeneous reactor ; providing ultimate protection of the surrounding area against radioactive ; contamination are described. The reactor system is comprised of a water boiler ; reactor having a water solution of enriched uranyl nitrate for a core, hydrogen-; oxygen recombiner system, nitrogen-oxygen recombiner system, sealed closed cycle ; gas recirculating system operating

1962-01-01

84

The DOE water cycle pilot study.  

SciTech Connect

In 1999, the U.S. Global Change Research Program (USGCRP) formed a Water Cycle Study Group (Hornberger et al. 2001) to organize research efforts in regional hydrologic variability, the extent to which this variability is caused by human activity, and the influence of ecosystems. The USGCRP Water Cycle Study Group was followed by a U.S. Department of Energy (DOE) Water Cycle Research Plan (Department of Energy 2002) that outlined an approach toward improving seasonal-to-interannual hydroclimate predictability and closing a regional water budget. The DOE Water Cycle Research Plan identified key research areas, including a comprehensive long-term observational database to support model development, and to develop a better understanding of the relationship between the components of local water budgets and large scale processes. In response to this plan, a multilaboratory DOE Water Cycle Pilot Study (WCPS) demonstration project began with a focus on studying the water budget and its variability at multiple spatial scales. Previous studies have highlighted the need for continued efforts to observationally close a local water budget, develop a numerical model closure scheme, and further quantify the scales in which predictive accuracy are optimal. A concerted effort within the National Oceanic and Atmospheric Administration (NOAA)-funded Global Energy and Water Cycle Experiment (GEWEX) Continental-scale International Project (GCIP) put forth a strategy to understand various hydrometeorological processes and phenomena with an aim toward closing the water and energy budgets of regional watersheds (Lawford 1999, 2001). The GCIP focus on such regional budgets includes the measurement of all components and reduction of the error in the budgets to near zero. To approach this goal, quantification of the uncertainties in both measurements and modeling is required. Model uncertainties within regional climate models continue to be evaluated within the Program to Intercompare Regional Climate Simulations (Takle et al. 1999), and model uncertainties within land surface models are being evaluated within the Program to Intercompare Land Surface Schemes (e.g., Henderson-Sellers 1993; Wood et al. 1998; Lohmann et al. 1998). In the context of understanding the water budget at watershed scales, the following two research questions that highlight DOE's unique water isotope analysis and high-performance modeling capabilities were posed as the foci of this pilot study: (1) Can the predictability of the regional water budget be improved using high-resolution model simulations that are constrained and validated with new hydrospheric water measurements? (2) Can water isotopic tracers be used to segregate different pathways through the water cycle and predict a change in regional climate patterns? To address these questions, numerical studies using regional atmospheric-land surface models and multiscale land surface hydrologic models were generated and, to the extent possible, the results were evaluated with observations. While the number of potential processes that may be important in the local water budget is large, several key processes were examined in detail. Most importantly, a concerted effort was made to understand water cycle processes and feedbacks at the land surface-atmosphere interface at spatial scales ranging from 30 m to hundreds of kilometers. A simple expression for the land surface water budget at the watershed scale is expressed as {Delta}S = P + G{sub in} - ET - Q - G{sub out}, where {Delta}S is the change in water storage, P is precipitation, ET is evapotranspiration, Q is streamflow, G{sub in} is groundwater entering the watershed, and G{sub out} is groundwater leaving the watershed, per unit time. The WCPS project identified data gaps and necessary model improvements that will lead to a more accurate representation of the terms in Eq. (1). Table 1 summarizes the components of this water cycle pilot study and the respective participants. The following section provides a description of the surface observation and modeling sites. T

Miller, N. L.; King, A. W.; Miller, M. A.; Springer, E. P.; Wesely, M. L.; Bashford, K. E.; Conrad, M. E.; Costigan, K.; Foster, P. N.; Gibbs, H. K.; Jin, J.; Klazura, J.; Lesht, B. M.; Machavaram, M. V.; Pan, F.; Song, J.; Troyan, D.; Washngton-Allen, R. A.; Environmental Research; LBNL; ORNL; BNL; LANL

2005-03-01

85

The seasonal cycle of water on Mars  

NASA Technical Reports Server (NTRS)

A review of the behavior of water in the Mars atmosphere and subsurface is appropriate now that data from the Mariner and Viking spacecraft have been analyzed and discussed for several years following completion of those missions. Observations and analyses pertinent to the seasonal cycle of water vapor in the atmosphere of Mars are reviewed, with attention toward transport of water and the seasonal exchange of water between the atmosphere and various non-atmospheric reservoirs. Possible seasonally-accessible sources and sinks for water include water ice on or within the seasonal and residual polar caps; surface or subsurface ice in the high-latitude regions of the planet; adsorbed or chemically-bound water within the near-surface regolith; or surface or subsurface liquid water. The stability of water within each of these reservoirs is discussed, as are the mechanisms for driving exchange of the water with the atmosphere and the timescales for exchange. Specific conclusions are reached about the distribution of water and the viability of each mechanism as a seasonal reservoir. Discussion is also included of the behavior of water on longer timescales, driven by the variations in solar forcing due to the quasi-periodic variations of the orbital obliquity. Finally, specific suggestions are made for future observations from spacecraft which would further define or constrain the seasonal cycle of water.

Jakosky, B. M.

1985-01-01

86

General characteristics of thermally cycled tin oxide gas sensors  

Microsoft Academic Search

The response, measured as conductance, of thermally cycled tin oxide gas sensors was studied to determine the potential inherent in this technique with respect to increased selectivity and sensitivity. It was found that the range of cycle temperature as well as the period of the cycle had a critical effect on the amount of information that could be extracted from

W. M. Sears; K. Colbow; F. Consadori

1989-01-01

87

Annual cycle and temperature dependence of pinene oxidation products and other water-soluble organic compounds in coarse and fine aerosol samples  

NASA Astrophysics Data System (ADS)

Filter samples of fine and coarse particulate matter were collected over a period of one year and analyzed for water-soluble organic compounds, including the pinene oxidation products pinic acid, pinonic acid, 3-methyl-1,2,3-butanetricarboxylic acid (3-MBTCA) and a variety of dicarboxylic acids (C5-C16) and nitrophenols. Seasonal variations and other characteristic features are discussed with regard to aerosol sources and sinks and data from other studies and regions. The ratios of adipic acid (C6) and phthalic acid (Ph) to azelaic acid (C9) indicate that the investigated aerosols samples were mainly influenced by biogenic sources. An Arrhenius-type correlation was found between the 3-MBTCA concentration and inverse temperature. Model calculations suggest that the temperature dependence is largely due to enhanced emissions and OH radical concentrations at elevated temperatures, whereas the influence of gas-particle partitioning appears to play a minor role. Enhanced ratios of pinic acid to 3-MBTCA indicate strong chemical aging of the investigated aerosols in summer and spring. Acknowledgment: The authors would like to thank M. Claeys for providing synthetic 3-methyl-1,2,3-butanetricarboxylic acid standards for LC-MS analysis and J. Fröhlich for providing filter samples and related information.

Zhang, Y.; Müller, L.; Winterhalter, R.; Moortgat, G. K.; Hoffmann, T.; Pöschl, U.

2010-05-01

88

Bioelectrochemical oxidation of water.  

PubMed

The electrolysis of water provides a link between electrical energy and hydrogen, a high energy density fuel and a versatile energy carrier, but the process is very expensive. Indeed, the main challenge is to reduce energy consumption for large-scale applications using efficient renewable catalysts that can be produced at low cost. Here we present for the first time that laccase can catalyze electrooxidation of H2O to molecular oxygen. Native and laboratory-evolved laccases immobilized onto electrodes serve as bioelectrocatalytic systems with low overpotential and a high O2 evolution ratio against H2O2 production during H2O electrolysis. Our results open new research ground on H2O splitting, as they overcome serious practical limitations associated with artificial electrocatalysts currently used for O2 evolution. PMID:24725275

Pita, Marcos; Mate, Diana M; Gonzalez-Perez, David; Shleev, Sergey; Fernandez, Victor M; Alcalde, Miguel; De Lacey, Antonio L

2014-04-23

89

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

DOE Data Explorer

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Schroeder, Jenna N.

90

Geothermal Water Use: Life Cycle Water Consumption, Water Resource Assessment, and Water Policy Framework  

SciTech Connect

This report examines life cycle water consumption for various geothermal technologies to better understand factors that affect water consumption across the life cycle (e.g., power plant cooling, belowground fluid losses) and to assess the potential water challenges that future geothermal power generation projects may face. Previous reports in this series quantified the life cycle freshwater requirements of geothermal power-generating systems, explored operational and environmental concerns related to the geochemical composition of geothermal fluids, and assessed future water demand by geothermal power plants according to growth projections for the industry. This report seeks to extend those analyses by including EGS flash, both as part of the life cycle analysis and water resource assessment. A regional water resource assessment based upon the life cycle results is also presented. Finally, the legal framework of water with respect to geothermal resources in the states with active geothermal development is also analyzed.

Schroeder, Jenna N.

2014-06-10

91

Evolution of the Martian water cycle.  

PubMed

The current Martian water cycle is extremely asymmetric, with large amounts of vapor subliming off a permanent north polar water ice cap in northern summer, but with no apparent major source of water vapor in the southern hemisphere. Detailed simulations of this process with a three-dimensional circulation model indicate that the summertime interhemispheric exchange (Hadley cell) is very much stronger than transport by eddies in other seasons. As a result, water ice would be distributed globally were it not for the buffering action of regolith soil adsorption which limits the net flux of water vapor off the north polar cap to amounts that are insignificant even on the scale of thousands of years. It has been suggested that the polar layered deposits are the result of exchange on these long time scales, driven by changes in Martian orbital parameters. We therefore are conducting simulations to test the effect of varied orbital parameters on the Martian water cycle. We find that when the perihelion summer pole is charged with a polar water ice cap, large quantities of water are quickly transfered to the aphelion summer pole, setting up an annual cycle that resembles the present one. Thus, the adsorptivity of the Martian regolith may be in the narrow range where it can limit net transport from the aphelion but not the perihelion pole. PMID:11543274

Houben, H; Haberle, R M; Young, R E; Zent, A P

1997-01-01

92

Circadian Clock NAD+ Cycle Drives Mitochondrial Oxidative Metabolism in Mice  

PubMed Central

Circadian clocks are self-sustained cellular oscillators that synchronize oxidative and reductive cycles in anticipation of the solar cycle. We found that the clock transcription feedback loop produces cycles of nicotinamide adenine dinucleotide (NAD+) biosynthesis, adenosine triphosphate production, and mitochondrial respiration through modulation of mitochondrial protein acetylation to synchronize oxidative metabolic pathways with the 24-hour fasting and feeding cycle. Circadian control of the activity of the NAD+-dependent deacetylase sirtuin 3 (SIRT3) generated rhythms in the acetylation and activity of oxidative enzymes and respiration in isolated mitochondria, and NAD+ supplementation restored protein deacetylation and enhanced oxygen consumption in circadian mutant mice. Thus, circadian control of NAD+ bioavailability modulates mitochondrial oxidative function and organismal metabolism across the daily cycles of fasting and feeding. PMID:24051248

Peek, Clara Bien; Affinati, Alison H.; Ramsey, Kathryn Moynihan; Kuo, Hsin-Yu; Yu, Wei; Sena, Laura A.; Ilkayeva, Olga; Marcheva, Biliana; Kobayashi, Yumiko; Omura, Chiaki; Levine, Daniel C.; Bacsik, David J.; Gius, David; Newgard, Christopher B.; Goetzman, Eric; Chandel, Navdeep S.; Denu, John M.; Mrksich, Milan; Bass, Joseph

2014-01-01

93

Oxidation of water emulsified olive oils  

Microsoft Academic Search

The susceptibility to oxidation of water emulsified olive oils was monitored by preparing emulsions with different amounts of water.The oxidative and kinetic stability of the emulsions were studied by performing simultaneous measurements of sedimentation and oxidation. The results reveal that the greater the region of emulsion stability, the longer the resistance of oil to oxidation. The micrographs of Video-Enhanced Microscopy

L. Ambrosone; M. Mosca; A. Ceglie

2006-01-01

94

Solar High Temperature Water-Splitting Cycle with Quantum Boost  

SciTech Connect

A sulfur family chemical cycle having ammonia as the working fluid and reagent was developed as a cost-effective and efficient hydrogen production technology based on a solar thermochemical water-splitting cycle. The sulfur ammonia (SA) cycle is a renewable and sustainable process that is unique in that it is an all-fluid cycle (i.e., with no solids handling). It uses a moderate temperature solar plant with the solar receiver operating at 800°C. All electricity needed is generated internally from recovered heat. The plant would operate continuously with low cost storage and it is a good potential solar thermochemical hydrogen production cycle for reaching the DOE cost goals. Two approaches were considered for the hydrogen production step of the SA cycle: (1) photocatalytic, and (2) electrolytic oxidation of ammonium sulfite to ammonium sulfate in aqueous solutions. Also, two sub-cycles were evaluated for the oxygen evolution side of the SA cycle: (1) zinc sulfate/zinc oxide, and (2) potassium sulfate/potassium pyrosulfate. The laboratory testing and optimization of all the process steps for each version of the SA cycle were proven in the laboratory or have been fully demonstrated by others, but further optimization is still possible and needed. The solar configuration evolved to a 50 MW(thermal) central receiver system with a North heliostat field, a cavity receiver, and NaCl molten salt storage to allow continuous operation. The H2A economic model was used to optimize and trade-off SA cycle configurations. Parametric studies of chemical plant performance have indicated process efficiencies of ~20%. Although the current process efficiency is technically acceptable, an increased efficiency is needed if the DOE cost targets are to be reached. There are two interrelated areas in which there is the potential for significant efficiency improvements: electrolysis cell voltage and excessive water vaporization. Methods to significantly reduce water evaporation are proposed for future activities. Electrolysis membranes that permit higher temperatures and lower voltages are attainable. The oxygen half cycle will need further development and improvement.

Taylor, Robin [SAIC] [SAIC; Davenport, Roger [SAIC] [SAIC; Talbot, Jan [UCSD] [UCSD; Herz, Richard [UCSD] [UCSD; Genders, David [Electrosynthesis Co.] [Electrosynthesis Co.; Symons, Peter [Electrosynthesis Co.] [Electrosynthesis Co.; Brown, Lloyd [TChemE] [TChemE

2014-04-25

95

An updated view of global water cycling  

NASA Astrophysics Data System (ADS)

Unprecedented new observation capacities combined with revolutions in modeling, we are poised to make huge advances in water cycle assessment, understanding, and prediction. To realize this goal, we must develop a discipline of prediction and verification through the integration of water and energy cycle observations and models, and to verify model predictions against observed phenomena to ensure that research delivers reliable improvements in prediction skill. Accomplishing these goals will require, in part, an accurate accounting of the key reservoirs and fluxes associated with the global water and energy cycle, including their spatial and temporal variability, through integration of all necessary observations and research tools. A brief history of the lineage of the conventional water balance and a summary accounting of all major parameters of the water balance using highly respected secondary sources will be presented. Principally, recently published peer reviewed papers reporting results of original work involving direct measurements and new data generated by high-tech devices (e.g. satellite / airborne instruments, supercomputers, geophysical tools) will be employed. This work lends credence to the conventional water balance ideas, but also reveals anachronistic scientific concepts/models, questionable underlying data, longstanding oversights and outright errors in the water balance.

Houser, P. R.; Schlosser, A.; Lehr, J.

2009-04-01

96

Recent Advances in GEO Water Cycle Activities  

NASA Astrophysics Data System (ADS)

Over the past few years GEO (Group on Earth Observations) efforts within the Water Societal Benefit Area (SBA) have been coordinated by the Science Committee of the former Integrated Global Observing Strategy Partnership (IGOS-P) IGWCO (Integrated Global Water Cycle Observations) theme. Within this framework a number of projects related to data system design, product development, and capacity building are being carried out. GEO has recently consolidated the Water SBA activities into three tasks, namely Droughts, Floods and Water Resource Management; Capacity Building for Water Resource Management (in Asia, Africa and the Americas); and Integrated Products for Water Resource Management and Research. In order to strengthen interactions with the GEO and its User Interface Committee, a Water Cycle Community of Practice (COP) was initiated. In addition, within the past year, the IGWCO Science Committee has decided to also function as a Community of Practice in collaboration with the existing Water Cycle COP. This overview will provide background and an update on the GEO Water SBA activities with an emphasis of the way in which these activities are being integrated within the three tasks. It will also describe activities that are planned for 2010 to facilitate this integration. Recent advances related to drought monitoring, capacity and network building, and observational and data systems will be highlighted. New water-related activities arising from collaborations between US GEO and Canada GEO, and through activities within the GEO Architecture and Data Committee, will also be described. This presentation will conclude with a longer-term outlook for water within the GEO framework and provide some guidance for interested experts on how they can become involved in helping to implement these plans.

Lawford, R. G.

2009-12-01

97

WaterNet: The NASA Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

The water cycle is continuously being transformed by climate change, erosion, pollution, salinization, and engineering practices, and is central to drought, flood, and disease hazards. Therefore, it is a national priority is to use advancements in scientific observations and knowledge to develop solutions to society's water challenges. NASA's unique role in this national priority is to exploit its unique view from space to improve water and energy cycle monitoring and prediction. As such, NASA's Earth science programs have collected substantial water cycle information and knowledge that must be integrated and shared to develop solutions in all twelve national priority application areas. However, NASA alone cannot achieve the ultimate goal of improved operational environmental assessments, predictions and applications and therefore must establish collaborations and interoperability with existing networks and nodes of research organizations, operational agencies, the scientific community, and private industry. Therefore, we propose to develop WaterNet: The NASA Water Cycle Solutions Network whose goal is to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend NASA research results to augment decision support tools and meet national needs. We will develop WaterNet by engaging relevant NASA water and energy cycle resources and community-of-practice organizations to develop what we term an "actionable database" that can be used to communicate and connect NASA Water and energy cycle focus area research Results (NWRs) towards the improvement of water-related Decision Support Tools (DSTs). Recognizing the many existing highly valuable water-related science and application networks, we will focus a balance of our efforts to enable their interoperability in a solutions network context. We will initially focus on identifying, collecting information about, and analyzing the two end points, these being the NWRs and water related DSTs. We will then develop strategies to connect these two end points via innovative communication strategies, improved user access to NASA resources, improved water cycle research community appreciation for DST requirements, improved policymaker, management and stakeholder knowledge of NASA research and application products, and identifying pathways for progress. Finally, we will develop relevant benchmarking and metrics, to understand the network's characteristics, to optimize its performance, and to establish sustainability.

Belvedere, D. R.; Houser, P. R.; Imam, B.; Schiffer, R.; Schlosser, C. A.; Gupta, H. V.; Welty, C.; Vorosmarty, C.; Matthews, D.; Lawford, R.

2006-05-01

98

Global Changes of the Water Cycle Intensity  

NASA Technical Reports Server (NTRS)

In this study, we evaluate numerical simulations of the twentieth century climate, focusing on the changes in the intensity of the global water cycle. A new diagnostic of atmospheric water vapor cycling rate is developed and employed, that relies on constituent tracers predicted at the model time step. This diagnostic is compared to a simplified traditional calculation of cycling rate, based on monthly averages of precipitation and total water content. The mean sensitivity of both diagnostics to variations in climate forcing is comparable. However, the new diagnostic produces systematically larger values and more variability than the traditional average approach. Climate simulations were performed using SSTs of the early (1902-1921) and late (1979- 1998) twentieth century along with the appropriate C02 forcing. In general, the increase of global precipitation with the increases in SST that occurred between the early and late twentieth century is small. However, an increase of atmospheric temperature leads to a systematic increase in total precipitable water. As a result, the residence time of water in the atmosphere increased, indicating a reduction of the global cycling rate. This result was explored further using a number of 50-year climate simulations from different models forced with observed SST. The anomalies and trends in the cycling rate and hydrologic variables of different GCMs are remarkably similar. The global annual anomalies of precipitation show a significant upward trend related to the upward trend of surface temperature, during the latter half of the twentieth century. While this implies an increase in the hydrologic cycle intensity, a concomitant increase of total precipitable water again leads to a decrease in the calculated global cycling rate. An analysis of the land/sea differences shows that the simulated precipitation over land has a decreasing trend while the oceanic precipitation has an upward trend consistent with previous studies and the available observations. The decreasing continental trend in precipitation is located primarily over tropical land regions, with some other regions, such as North America experiencing an increasing trend. Precipitation trends are diagnosed further using the water tracers to delineate the precipitation that occurs because of continental evaporation, as opposed to oceanic evaporation. These diagnostics show that over global land areas, the recycling of continental moisture is decreasing in time. However, the recycling changes are not spatially uniform so that some regions, most notably over the United States, experience continental recycling of water that increases in time.

Bosilovich, Michael G.; Schubert, Siegfried D.; Walker, Gregory K.

2003-01-01

99

Investigating the Water Cycle: Using Plants to Study Evaporation  

NSDL National Science Digital Library

In this science activity, students investigate the water cycle by testing the water evaporated from leaves (transpiration) in a field experience. Students use elements of this information to track the water cycle through it's various stages.

100

Children's Views about the Water Cycle.  

ERIC Educational Resources Information Center

Israeli children's (kindergarten to grade nine) explanations about the water cycle are described. Reports the children's views about the source of clouds and the mechanism of rainfall. It was concluded that understanding evaporation is a necessary condition for explaining a mechanism of rain containing the ideas of condensation and heaviness. (YP)

Bar, Varda

1989-01-01

101

Modeling the Martian seasonal water cycle  

NASA Astrophysics Data System (ADS)

Ever since the observations of Percival Lowell, the annual cycle of Martian water has been a fascinating topic in planetary exploration. Observations by the Viking Orbiter, supplemented by Earth-based microwave and infrared observations, have given us a reasonable picture of this cycle. We are now also able to model the cycle using our Mars Climate Model, a simplified atmospheric general circulation model designed specifically for this purpose. We find that a thin adsorbing layer of the Martian regolith plays a fundamental role in the water cycle, limiting the lower atmospheric relative humidity and preventing the formation of widespread ice deposits at low latitudes. We are thus able to estimate a large-scale average value of the specific soil surface area of this regolith. Water which evaporates from the permanent north polar ice cap during summer is returned by a process of repeated evaporation and precipitation on the retreating seasonal cap the following spring, so that the global inventory of water outside the polar caps ranges within narrow limits. (There is a small net annual deposition of water ice at the south polar cap which is always at dry ice temperatures.) If ice on the residual south polar cap is exposed during the summer, it rapidly sublimes, generating vapor amounts similar to those observed in northern summer. Recovery to normal dry conditions in the southern atmosphere occurs very rapidly in the next year. Such an event could explain the otherwise anomalous Earth-based pre-Viking observations of a wet southern summer. If southern ice deposits at lower latitudes are exposed, the vapor can be transferred irreversibly through the strong Hadley cell to the north polar cap. We therefore speculate that the asymmetry of Mars' current orbit is responsible for the asymmetry of the present water distribution (with extensive permanent water ice deposits located only in the colder, aphelion summer, northern hemisphere).

Houben, Howard; Haberle, Robert M.; Young, Richard E.; Zent, Aaron P.

1997-04-01

102

Does GRACE see the water cycle 'intensifying'?  

NASA Astrophysics Data System (ADS)

Several researchers have postulated that, under a changing climate due to anthropogenic forcing, an intensification of the water cycle is already under way (Huntington, 2006). This is usually related to increases in hydrological fluxes such as precipitation (P), evapotranspiration (E), and river discharge (R). It is under debate, however, whether such observed or reconstructed flux changes are real and on what scales. Large-scale increase or decrease of the flux deficit (P-E) would lead to acceleration or deceleration of water storage anomalies possibly visible in GRACE time series, when discharge variability is small or properly accounted for. We investigate to what extent such accelerations, which are indeed found in maps of global gridded GRACE water storage anomalies, can be explained using output fields derived from global and regional atmospheric (re-)analyses and from hydrological models. We find this analysis challenging, since the GRACE time series is short and dominated by ENSO-type natural variability. Observed accelerations strongly depend on the analysis time frame, and may be explained to a large percentage by natural variability, thus masking a possible anthropogenically driven intensification of the terrestrial water cycle. This motivates us to apply statistical decomposition techniques in order to identify modes of natural variabilities and to remove them from the GRACE time series prior to the estimation of accelerations. Huntington T.G. (2006): Evidence for intensification of the global water cycle: Review and synthesis. J. Hydrology, 319:83-95

Eicker, Annette; Kusche, Jürgen; Forootan, Ehsan; Springer, Anne; Schumacher, Maike; Ohlwein, Christian

2014-05-01

103

Efficient generation of H2 by splitting water with an isothermal redox cycle.  

PubMed

Solar thermal water-splitting (STWS) cycles have long been recognized as a desirable means of generating hydrogen gas (H2) from water and sunlight. Two-step, metal oxide-based STWS cycles generate H2 by sequential high-temperature reduction and water reoxidation of a metal oxide. The temperature swings between reduction and oxidation steps long thought necessary for STWS have stifled STWS's overall efficiency because of thermal and time losses that occur during the frequent heating and cooling of the metal oxide. We show that these temperature swings are unnecessary and that isothermal water splitting (ITWS) at 1350°C using the "hercynite cycle" exhibits H2 production capacity >3 and >12 times that of hercynite and ceria, respectively, per mass of active material when reduced at 1350°C and reoxidized at 1000°C. PMID:23908235

Muhich, Christopher L; Evanko, Brian W; Weston, Kayla C; Lichty, Paul; Liang, Xinhua; Martinek, Janna; Musgrave, Charles B; Weimer, Alan W

2013-08-01

104

Multi-cycle boiling water reactor fuel cycle optimization  

SciTech Connect

In this work a new computer code, BWROPT (Boiling Water Reactor Optimization), is presented. BWROPT uses the Parallel Simulated Annealing (PSA) algorithm to solve the out-of-core optimization problem coupled with an in-core optimization that determines the optimum fuel loading pattern. However it uses a Haling power profile for the depletion instead of optimizing the operating strategy. The result of this optimization is the optimum new fuel inventory and the core loading pattern for the first cycle considered in the optimization. Several changes were made to the optimization algorithm with respect to other nuclear fuel cycle optimization codes that use PSA. Instead of using constant sampling probabilities for the solution perturbation types throughout the optimization as is usually done in PSA optimizations the sampling probabilities are varied to get a better solution and/or decrease runtime. The new fuel types available for use can be sorted into an array based on any number of parameters so that each parameter can be incremented or decremented, which allows for more precise fuel type selection compared to random sampling. Also, the results are sorted by the new fuel inventory of the first cycle for ease of comparing alternative solutions. (authors)

Ottinger, K.; Maldonado, G.I. [University of Tennessee, 311 Pasqua Engineering Building, Knoxville, TN 37996-2300 (United States)

2013-07-01

105

The artificial water cycle: emergy analysis of waste water treatment.  

PubMed

The artificial water cycle can be divided into the phases of water capture from the environment, potabilisation, distribution, waste water collection, waste water treatment and discharge back into the environment. The terminal phase of this cycle, from waste water collection to discharge into the environment, was assessed by emergy analysis. Emergy is the quantity of solar energy needed directly or indirectly to provide a product or energy flow in a given process. The emergy flow attributed to a process is therefore an index of the past and present environmental cost to support it. Six municipalities on the western side of the province of Bologna were analysed. Waste water collection is managed by the municipal councils and treatment is carried out in plants managed by a service company. Waste water collection was analysed by compiling a mass balance of the sewer system serving the six municipalities, including construction materials and sand for laying the pipelines. Emergy analysis of the water treatment plants was also carried out. The results show that the great quantity of emergy required to treat a gram of water is largely due to input of non renewable fossil fuels. As found in our previous analysis of the first part of the cycle, treatment is likewise characterised by high expenditure of non renewable resources, indicating a correlation with energy flows. PMID:12817633

Bastianoni, Simone; Fugaro, Laura; Principi, Ilaria; Rosini, Marco

2003-04-01

106

Following the Water Cycle to Sustainability  

NASA Astrophysics Data System (ADS)

For scientists, modeling the connections among the parts of complex, dynamic systems is crucial. Doing so lets us understand emergent phenomena such as ecosystem behavior and climate patterns that could not otherwise be predicted. Emergent phenomena can typically only be understood or appreciated when we stand "outside" the system. When scientists take such an outsiders view of earth's systems they can propose many ways that human activities modify the climate system (e.g., increasing or reducing GHG emissions). But what should we do to achieve a sustainable future? Sustainability is an emergent property that arises at the level of the planetary management system, of which the scientific establishment is just a part. We are "insiders" and it is impossible to completely envision the conditions for sustainability or to plan for it. The crises in our atmosphere, biosphere, oceans, and in the natural and energy resource sectors are based in science and do call for urgent changes in science education. But education that focuses solely on science to meet the challenges of sustainability may be as likely to harm humanity's long-term prospects as to improve them. I present activities and teaching strategies that I use in general education classes at West Chester University, a comprehensive institution of roughly 14,000 undergraduates. The overarching concept is to extend "modeling the connections" to the sustainability level and to train students to think outside the system. To make the ideas more accessible, I have the students become sensors at their particular point in the web of connections that constitute the planetary management system. I ask them to evaluate their connection in three domains proposed by John Ehrenfeld (Sustainability by Design, Yale University Press, 2008): sense of place in the natural world; sense of responsibility for our actions, and sense of what it is to be a human being. I have them analyze their sense of connection with reference to a systems learning model based on feedback and limits to perception. I focus on a part of the course that builds on connections that start in the hydrosphere and that includes some basic experiential learning about the water cycle and students' reliance on it. We measure and visualize aspects of the water cycle in nearby areas of campus (designated as an outdoor classroom and demonstration garden). The evapotranspiration flow is used to introduce notions of what can happen when flows are not sensed (e.g., invisible to us). Students use an online water footprint calculator to discover how large their water reliance is, particularly through energy generation, food consumption and food waste; and how far their water reach extends (virtual water trade). They consider the ethical implications of their water use in a world in which it is becoming a more rare resource and in some cases a valued commodity. They learn about non-utilitarian values of water based on an activity on the values of nature. They look at local, community-based efforts to improve water quality and to re-localize water dependence. A reading from Aldo Leopold puts the water cycle in a historical and cultural perspective. The water cycle is strongly interwoven with natural and human energy systems, the climate system, the carbon cycle, nutrient cycles, the rock cycle, and serves as a starting point to reach many other topics.

Lutz, T. M.

2012-12-01

107

Earth's Changing Energy and Water Cycles  

NASA Astrophysics Data System (ADS)

A new assessment of the flows of energy through the climate system will be presented. It features an imbalance at the top-of-atmosphere owing to an enhanced greenhouse effect that produces global warming. Most of the surplus energy trapped increases ocean heat content. Large upwards surface thermal radiation is offset by back radiation from greenhouse gases and clouds in the atmosphere. At the surface, the net losses of energy are greatest through evapotranspiration, followed closely by net radiation, while sensible heat losses are much smaller. This highlights the vital role of the hydrological cycle and why direct changes in the water cycle are a consequence of climate change. Nonetheless, net changes in surface evaporation are fairly modest and a much larger percentage change occurs in the water-holding capacity as atmospheric temperatures increase (4% per °F). A consequence is increased water vapor in the atmosphere which feeds all storms and thus leads to more intense precipitation; increased water vapor, heavier rains and stronger storms are already observed to be happening. However, the disparity between modestly enhanced evaporation and heavier rains means decreases in frequency of precipitation and enhanced droughts. With more precipitation per unit of upward motion in the atmosphere, the atmospheric circulation weakens, causing monsoons to falter. Observed changes in Atlantic hurricanes will be used to illustrate some of these aspects. Understanding these profound consequences of climate change is especially important for water managers. In reality that includes everyone.

Trenberth, K. E.

2008-05-01

108

Water Oxidation on GaN Surface  

Microsoft Academic Search

Efficient solar water-splitting requires a good catalyst to oxidize water into O2 with the photo-holes. Efficient water oxidation catalysts are hard to find. The solid solution of wurtzite GaN\\/ZnO is a water-splitting photocatalyst which works in visible light, while pure GaN is a water-splitting photocatalyst which works in UV. Unlike other semiconductors, the surfaces of both materials exhibit high efficiencies

Xiao Shen; Jue Wang; Y. A. Small; P. B. Allen; M. V. Fernandez-Serra; M. S. Hybertsen; J. T. Muckerman

2010-01-01

109

Carbon footprint estimation of municipal water cycle  

NASA Astrophysics Data System (ADS)

This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated and the use of a GIS based model as a sustainability planning framework was evaluated. The carbon footprint metric is a useful tool for prediction and measurement of a system's sustainable performance over its expected life cycle. Two metrics were calculated: tons of carbon dioxide per year to represent the contribution to global warming and watt-hrs per gallon to show the embodied energy associated with water consumption. The water delivery to the building, removal of wastewater from the building and associated treatment of water and wastewater create a sizable carbon footprint; often the energy attributed to this water service is the greatest end use of electrical energy. The embodied energy in water depends on topographical characteristics of the area's local water supply, the efficiency of the treatment systems, and the efficiency of the pumping stations. The questions answered by this research are: What is the impact of demand side sustainable water practices on the embodied energy as represented by a comprehensive carbon footprint? What are the major energy consuming elements attributed to the system? What is a viable and visually identifiable tool to estimate the carbon footprint attributed to those Greenhouse Gas (GHG) producing elements? What is the embodied energy and emission associated with water use delivered to a building? Benefits to be derived from a standardized GIS applied carbon footprint estimation approach include: (1) Improved environmental and economic information for the developers, water and wastewater processing and municipal planners; (2) Improved energy use reporting and conservation planning; (3) Establishment of a benchmark for GHG emissions attributed to the water and wastewater industry; (4) Ability to quantify relative impacts of building design options using carbon emission equivalents. The GIS based model was applied to the Dulles South and Brambelton regions in Loudoun County, Virginia. The GIS revealed the customer's embodied energy to be in the range of 4.41MWh/Mgal to 8.0 MWh/Mgal. The customer's carbon footprint is between 0.008 and18.0 Tons of CO2 for year 2008. The results of this study contributed to development of a standardized approach to estimate the GHG impact of a total water cycle, and provided a viable GIS tool resulting in visual maps as a decision support. It also showed the use of derived empirical formulas in predication of GHG impact for end users in a specific geographical area. The embodied energy in delivered water can be estimated using the devised model and be considered by the building sustainability ranking programs such as the USGBC LEED rating system. KEYWORDS. Water Life Cycle, Embodied Energy, Global Warming Potential, Energy Intensity, Energy Intensity Matrix, Emission Intensity, Emission Coefficient, Carbon Dioxide Emission, Water and Wastewater, Collection, Treatment and Distribution, Carbon Footprint, Topography, Municipality, Environmental Indicator, ArcGIS, LEED, GHG, ESI, LCA, LCEA, LCI, Sustainability, End Use, Potable Water

Bakhshi, Ali A.

2009-11-01

110

Alternating electron and proton transfer steps in photosynthetic water oxidation.  

PubMed

Water oxidation by cyanobacteria, algae, and plants is pivotal in oxygenic photosynthesis, the process that powers life on Earth, and is the paradigm for engineering solar fuel-production systems. Each complete reaction cycle of photosynthetic water oxidation requires the removal of four electrons and four protons from the catalytic site, a manganese-calcium complex and its protein environment in photosystem II. In time-resolved photothermal beam deflection experiments, we monitored apparent volume changes of the photosystem II protein associated with charge creation by light-induced electron transfer (contraction) and charge-compensating proton relocation (expansion). Two previously invisible proton removal steps were detected, thereby filling two gaps in the basic reaction-cycle model of photosynthetic water oxidation. In the S(2) ? S(3) transition of the classical S-state cycle, an intermediate is formed by deprotonation clearly before electron transfer to the oxidant (Y Z OX). The rate-determining elementary step (?, approximately 30 µs at 20?°C) in the long-distance proton relocation toward the protein-water interface is characterized by a high activation energy (E(a) = 0.46 ± 0.05 eV) and strong H/D kinetic isotope effect (approximately 6). The characteristics of a proton transfer step during the S(0) ? S(1) transition are similar (?, approximately 100 µs; E(a) = 0.34 ± 0.08 eV; kinetic isotope effect, approximately 3); however, the proton removal from the Mn complex proceeds after electron transfer to . By discovery of the transient formation of two further intermediate states in the reaction cycle of photosynthetic water oxidation, a temporal sequence of strictly alternating removal of electrons and protons from the catalytic site is established. PMID:22988080

Klauss, André; Haumann, Michael; Dau, Holger

2012-10-01

111

Hydrologic Cycle and Water Balance Equation  

NSDL National Science Digital Library

This exercise is designed to evaluate the students' understanding of both the hydrologic cycle and the water budget (mass balance) equation. In my course, the exercise is the students' first exposure to models in the course. While the exercise may seem basic, students gain experience in creating conceptual models and then generating mathematical models from the conceptual model. The exercise provides students with an introduction (or refresher) to some basic Excel formulas. Finally, the exercise can be modified to include more "what if" scenarios that require critical thinking and analysis from the students.

Eric Peterson

112

Carbon catalyzed supercritical water oxidation of phenol  

Microsoft Academic Search

Activated carbon was employed as a novel catalyst for supercritical water oxidation of phenol. High-concentrations of phenol were treated in supercritical water at 673 K and 25 MPa with an equivalent amount of oxygen in a reactor packed with activated carbon. Although activated carbon itself was oxidized in the reaction field, its weight decrease was sufficiently slow for its catalytic

Yukihiko Matsumura; Taro Urase; Kazuo Yamamoto; Teppei Nunoura

2002-01-01

113

Improved efficiency in the sulfur dioxide-iodine hydrogen cycle through the use of magnesium oxide  

SciTech Connect

The reaction of iodine with dry magnesium oxide and magnesium sulfite hexahydrate was studied experimentally as a possible means of improving the efficiency of the sulfur dioxide-iodine cycle. When no extra water was introduced, the maximum product yield was 67% obtained at 423 K. With excess water vapor, a nonporous plug was formed which prevented complete reaction. In the second case, maximum yield was 62% measured at 433 K showing that added water does not increase reaction products. This reaction gives an alternate route for producing hydrogen from water via the sulfur dioxide-iodine process.

Mason, C.F.V.; Bowman, M.G.

1981-01-01

114

Iridium oxide-polymer nanocomposite electrode materials for water oxidation.  

PubMed

Nanocomposite anode materials for water oxidation have been readily synthesized by electrodeposition of iridium oxide nanoparticles into poly(pyrrole-alkylammonium) films, previously deposited onto carbon electrodes by oxidative electropolymerization of a pyrrole-alkylammonium monomer. The nanocomposite films were characterized by electrochemistry, transmission electron microscopy, and atomic force microscopy. They showed an efficient electrocatalytic activity toward the oxygen evolution reaction. Data from Tafel plots have demonstrated that the catalytic activity of the iridium oxide nanoparticles is maintained following their inclusion in the polymer matrix. Bulk electrolysis of water at carbon foam modified electrodes have shown that the iridium oxide-polymer composite presents a higher catalytic activity and a better operational stability than regular oxide films. PMID:25045786

Lattach, Youssef; Rivera, Juan Francisco; Bamine, Tahya; Deronzier, Alain; Moutet, Jean-Claude

2014-08-13

115

Light driven water oxidation by a single site cobalt salophen catalyst.  

PubMed

A salophen cobalt(II) complex enables water oxidation at neutral pH in photoactivated sacrificial cycles under visible light, thus confirming the high appeal of earth abundant single site catalysis for artificial photosynthesis. PMID:24036577

Pizzolato, Erica; Natali, Mirco; Posocco, Bianca; Montellano López, Alejandro; Bazzan, Irene; Di Valentin, Marilena; Galloni, Pierluca; Conte, Valeria; Bonchio, Marcella; Scandola, Franco; Sartorel, Andrea

2013-11-01

116

Chromium cycling in soils and water: links, gaps, and methods.  

PubMed Central

The major links in the cycling of chromium in soils and in natural waters are between chromium(III) and chromium (VI). Between the larger links are lesser links involving processes of mobilization and oxidation of CrIII and reduction of CrVI. The gaps are mainly in our understanding of the factors that control these processes. If soluble CrIII is added to an "average" soil, a portion of it will become immediately oxidized by manganese oxides to CrVI. The rest of the CrIII may remain reduced for long periods of time, even in the presence of electron-accepting manganese oxides. However, this less available CrIII can be mobilized by low molecular weight organic complexers and then oxidized where redox conditions are optimal. Usually part of any CrVI added to a soil or sediment will be reduced instantly, especially under acid conditions. On the other hand, high concentrations of polluting CrVI may quickly exhaust the readily available reducing power of the matrix material and excess CrVI, the thermodynamically stable form in air, may persist for years in soils or lagoons without reduction. Cleanup of chromium pollution must involve the surrounding of both CrIII and CrVI with excesses of slowly available reducing substances and sealing them permanently from inputs of atmospheric oxygen. Monitoring the effectiveness of the measures is mandatory, but fortunately the chemical testing for CrVI in soil and water is simple and problem free compared with most colorimetric determinations. PMID:1935847

Bartlett, R J

1991-01-01

117

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the  

E-print Network

Plumbing the Global Carbon Cycle: Integrating Inland Waters into the Terrestrial Carbon Budget J. J components of the carbon cycle at either global or regional scales. By taking published estimates of gas constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis

Berkowitz, Alan R.

118

Highly efficient 6-stroke engine cycle with water injection  

DOEpatents

A six-stroke engine cycle having improved efficiency. Heat is recovered from the engine combustion gases by using a 6-stroke engine cycle in which combustion gases are partially vented proximate the bottom-dead-center position of the fourth stroke cycle, and water is injected proximate the top-dead-center position of the fourth stroke cycle.

Szybist, James P; Conklin, James C

2012-10-23

119

Terrestrial nitrous oxide cycles and atmospheric effects  

NASA Technical Reports Server (NTRS)

The basic processes that cause N2O emission from soils are briefly discussed, and the rate of the processes is shown to vary widely in space and time, depending on soil, climate, and agrotechnical conditions. Although significant amounts of N2O are indeed emitted from the land, the complexity of the soil processes involved and the wide variation of measured rates still prevents the quantitative evaluation, global budgeting, and reliable prediction of atmospheric N2O. Increased atmospheric N2O abundance increases the levels of odd-nitrogen in the stratosphere, which, in turn, decreases the stratospheric ozone density via a catalytic cycle. Using appropriate atmospheric models and current chemical kinetic data, it has been found that the dependence of ozone reduction on N2O increase is nearly linear; a simulated doubling of N2O leads to a predicted decrease of about 14 percent in total ozone column density. A 10 percent increase in N2O yields a predicted increase in nonmelanoma skin cancer of several percent, and a possible raising of surface temperature of 0.03 K.

Whitten, R. C.; Lawless, J. G.; Banin, A.

1984-01-01

120

The Hydrologic Cycle: Water's journey through time  

NSDL National Science Digital Library

This module discusses the hydrologic cycle and its impacts on the planet Earth. Additionally, the module addresses connections between the hydrologic cycle, climate and the impacts humans have had on the cycle.

Anne Egger

2003-08-26

121

The Water Cycle - Back and Forth (part 2)  

NSDL National Science Digital Library

Students will learn more about the water cycle components and how they work together. They will learn it is a closed system and the importance of the ocean in the cycle. Reading for understanding is a focus in this lesson.

Maribel Magdaleno

2012-07-17

122

The Water Cycle and Global Warming  

NSDL National Science Digital Library

The Baylor University College of Medicine continues to work at a furious pace on their delightful BioEd Online site, and educators everywhere love them for their work and dedication. Recently, they placed this ââ?¬Å?ready-to-goââ?¬Â lessson on the water cycle and global warming online, and itââ?¬â?¢s a true delight. As with the other lessons in this series, the materials here include a brief description of the lessonââ?¬â?¢s objective, along with information on the intended audience, the materials required to complete the lesson, and so on. Teachers will note that they will need to download a slide set, several activity sheets, and a ââ?¬Å?State of the Climate Reportââ?¬Â offered from the National Climatic Data Center.

123

8 Water Cycle in the Atmosphere and Shallow Subsurface  

Microsoft Academic Search

The global water cycle on Earth constitutes one of the most relevant components of the terrestrial ecosystem. While the vast majority of terrestrial water is stored in the world oceans, the perpetual cycle of water between ocean, atmosphere and land in all three phases is recognised as one basic feature that characterises the Earth, and is contrasted to the rest

Tetsuya Tokano

2005-01-01

124

Connecting the oxidation of soot to its redox cycling abilities.  

PubMed

Although it is known that soot particles are emitted in large quantities to the atmosphere, our understanding of their environmental effects is limited by our knowledge of how their composition is subsequently altered through atmospheric processing. Here we present an on-line mass spectrometric study of the changing chemical composition of hydrocarbon soot particles as they are oxidized by gas-phase ozone, and we show that the surface-mediated loss rates of adsorbed polycyclic aromatic hydrocarbons in soot are directly connected to a significant increase in the particle redox cycling abilities. With redox cycling implicated as an oxidative stress mechanism that arises after inhalation of atmospheric particles, this work draws a quantitative connection between the detailed heterogeneous chemistry occurring on atmospheric particles and a potential toxic mechanism attributable to that aerosol. PMID:25873384

Antiñolo, María; Willis, Megan D; Zhou, Shouming; Abbatt, Jonathan P D

2015-01-01

125

Water clustering on nanostructured iron oxide films  

NASA Astrophysics Data System (ADS)

The adhesion of water to solid surfaces is characterized by the tendency to balance competing molecule-molecule and molecule-surface interactions. Hydroxyl groups form strong hydrogen bonds to water molecules and are known to substantially influence the wetting behaviour of oxide surfaces, but it is not well-understood how these hydroxyl groups and their distribution on a surface affect the molecular-scale structure at the interface. Here we report a study of water clustering on a moiré-structured iron oxide thin film with a controlled density of hydroxyl groups. While large amorphous monolayer islands form on the bare film, the hydroxylated iron oxide film acts as a hydrophilic nanotemplate, causing the formation of a regular array of ice-like hexameric nanoclusters. The formation of this ordered phase is localized at the nanometre scale; with increasing water coverage, ordered and amorphous water are found to coexist at adjacent hydroxylated and hydroxyl-free domains of the moiré structure.

Merte, Lindsay R.; Bechstein, Ralf; Peng, Guowen; Rieboldt, Felix; Farberow, Carrie A.; Zeuthen, Helene; Knudsen, Jan; Lægsgaard, Erik; Wendt, Stefan; Mavrikakis, Manos; Besenbacher, Flemming

2014-06-01

126

Rethinking the light water reactor fuel cycle  

E-print Network

The once through nuclear fuel cycle adopted by the majority of countries with operating commercial power reactors imposes a number of concerns. The radioactive waste created in the once through nuclear fuel cycle has to ...

Shwageraus, Evgeni, 1973-

2004-01-01

127

Thermogravimetric analysis of the ZnO\\/Zn water splitting cycle  

Microsoft Academic Search

The endothermal dissociation of zinc oxide into its elements, followed by the exothermal hydrolysis of zinc, is considered as a two-step water splitting thermochemical cycle using high-temperature solar process heat. Thermogravimetric measurements were conducted on both reaction steps to elucidate the influence of temperature, oxygen partial pressure, inert gas flow rate, and chemical impurities on the reaction kinetics. The dissociation

A. Weidenkaff; A. W. Reller; A. Wokaun; A. Steinfeld

2000-01-01

128

An assessment of the thermodynamic performance of mixed gas-steam cycles. Part B: Water-injected and HAT cycles  

Microsoft Academic Search

Part B of this paper focuses on intercooled recuperated cycles where water is injected to improve both efficiency and power output. This concept is investigated for two basic cycle configurations: a Recuperated Water Injected (RWI) cycle, where water is simply injected downstream of the HP compressor, and a Humid air Turbine (HAT) cycle, where air\\/water mixing is accomplished in a

P. Chiesa; G. Lozza; E. G. Macchi; S. Consonni

1995-01-01

129

Soar's basic operation cycle Water-Jug Problem  

E-print Network

's basic operation cycle Tools Water-Jug Problem Eaters Simple Hello World Rule Hello World sp {hello-world (state ^type state) --> (write |Hello World|) (halt) } is a variable, that can be used 12/33 #12;Components Soar Rules Soar's basic operation cycle Tools Water-Jug Problem Eaters Hello

Bremen, Universität

130

GEWEX Global Data Sets for Water Cycle Research  

Microsoft Academic Search

The Global Energy and Water cycle Experiment (GEWEX) is the core project in the World Climate Research Programme (WCRP) concerned with studying the dynamics and thermodynamics of the atmosphere and interactions with the Earth's surface. Within the framework of GEWEX many global data sets related to the energy and water cycle have been developed and are still being developed. Most

P. J. van Oevelen; R. Lawford; S. Sorooshian

2008-01-01

131

Understanding water permeation in graphene oxide membranes.  

PubMed

Water transport through graphene-derived membranes has gained much interest recently due to its promising potential in filtration and separation applications. In this work, we explore water permeation in graphene oxide membranes using atomistic simulations and theoretical analysis, by considering flow through the interlayer gallery, expanded channels such as wrinkles of interedge spaces, and pores within the sheet. We find that, although flow enhancement can be established by nanoconfinement, fast water transport through pristine graphene channels is prohibited by a prominent side-pinning effect from capillaries formed within oxidized regions. We then discuss several flow enhancement mechanisms through the porous microstructures of graphene oxide membranes. These understandings are integrated into a complete picture to understand water permeation through the layer-by-layer and porous microstructure and can guide rational design of functional membranes for energy and environmental applications. PMID:24669772

Wei, Ning; Peng, Xinsheng; Xu, Zhiping

2014-04-23

132

Homogeneous and heterogenized iridium water oxidation catalysts  

NASA Astrophysics Data System (ADS)

The development of an efficient catalyst for the oxidative splitting of water into molecular oxygen, protons and electrons is of key importance for producing solar fuels through artificial photosynthesis. We are facing the problem by means of a rational approach aimed at understanding how catalytic performance may be optimized by the knowledge of the reaction mechanism of water oxidation and the fate of the catalytic site under the inevitably harsh oxidative conditions. For the purposes of our study we selected iridium water oxidation catalysts, exhibiting remarkable performance (TOF > 5 s-1 and TON > 20000). In particular, we recently focused our attention on [Cp*Ir(N,O)X] (N,O = 2-pyridincarboxylate; X = Cl or NO3) and [IrCl(Hedta)]Na water oxidation catalysts. The former exhibited a remarkable TOF whereas the latter showed a very high TON. Furthermore, [IrCl(Hedta)]Na was heterogenized onto TiO2 taking advantage of the presence of a dandling -COOH functionality. The heterogenized catalyst maintained approximately the same catalytic activity of the homogeneous analogous with the advantage that could be reused many times. Mechanistic studies were performed in order to shed some light on the rate-determining step and the transformation of catalysts when exposed to "oxidative stress". It was found that the last oxidative step, preceding oxygen liberation, is the rate-determining step when a small excess of sacrificial oxidant is used. In addition, several intermediates of the oxidative transformation of the catalyst were intercepted and characterized by NMR, X-Ray diffractometry and ESI-MS.

Macchioni, Alceo

2014-10-01

133

A Satellite View of Global Water and Energy Cycling  

NASA Astrophysics Data System (ADS)

The global water cycle describes liquid, solid and vapor water dynamics as it moves through the atmosphere, oceans and land. Life exists because of water, and civilization depends on adapting to the constraints imposed by water availability. The carbon, water and energy cycles are strongly interdependent - energy is moved through evaporation and condensation, and photosynthesis is closely related to transpiration. There are significant knowledge gaps about water storage, fluxes and dynamics - we currently do not really know how much water is stored in snowpacks, groundwater or reservoirs. The view from space offers a vision for water science advancement. This vision includes observation, understanding, and prediction advancements that will improve water management and to inform water-related infrastructure that planning to provide for human needs and to protect the natural environment. The water cycle science challenge is to deploy a series of coordinated earth observation satellites, and to integrate in situ and space-borne observations to quantify the key water-cycle state variables and fluxes. The accompanying societal challenge is to integrate this information along with water cycle physics, and ecosystems and societal considerations as a basis for enlightened water resource management and to protect life and property from effects of water cycle extremes. Better regional to global scale water-cycle observations and predictions need to be readily available to reduce loss of life and property caused by water-related hazards. To this end, the NASA Energy and Water cycle Study (NEWS) has been documenting the satellite view of the water cycle with a goal of enabling improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. NEWS has fostered broad interdisciplinary collaborations to study experimental and operational satellite observations and has developed analysis tools for characterizing air/sea fluxes, ocean circulation, atmospheric states, radiative balances, land surface states, sub-surface hydrology, snow and ice. This presentation will feature an overview of recent progress towards this challenge, and lay out the plan for coordination with complementary international efforts.

Houser, P. R.

2012-12-01

134

Supercritical water oxidation - Microgravity solids separation  

NASA Technical Reports Server (NTRS)

This paper discusses the application of supercritical water oxidation (SCWO) waste treatment and water recycling technology to the problem of waste disposal in-long term manned space missions. As inorganic constituents present in the waste are not soluble in supercritical water, they must be removed from the organic-free supercritical fluid reactor effluent. Supercritical water reactor/solids separator designs capable of removing precipitated solids from the process' supercritical fluid in zero- and low- gravity environments are developed and evaluated. Preliminary experiments are then conducted to test the concepts. Feed materials for the experiments are urine, feces, and wipes with the addition of reverse osmosis brine, the rejected portion of processed hygiene water. The solid properties and their influence on the design of several oxidation-reactor/solids-separator configurations under study are presented.

Killilea, William R.; Hong, Glenn T.; Swallow, Kathleen C.; Thomason, Terry B.

1988-01-01

135

Ceramic coating system or water oxidation environments  

DOEpatents

A process for water oxidation of combustible materials in which during at least a part of the oxidation corrosive material is present and makes contact with at least a portion of the apparatus over a contact area on the apparatus. At least a portion of the contact surface area comprises titanium dioxide coated onto a titanium metal substrate. Such ceramic composites have been found to be highly resistant to environments encountered in the process of supercritical water oxidation. Such environments typically contain greater than 50 mole percent water, together with oxygen, carbon dioxide, and a wide range of acids, bases, and salts. Pressures are typically about 27.5 to about 1000 bar while temperatures range as high as 700.degree. C. The ceramic composites are also resistant to degradation mechanisms caused by thermal stresses.

Hong, Glenn T. (Tewksbury, MA)

1996-01-01

136

MODELLING RADIATIVELY ACTIVE WATER-ICE CLOUDS: IMPACT ON THE THERMAL STRUCTURE AND WATER CYCLE.  

E-print Network

MODELLING RADIATIVELY ACTIVE WATER-ICE CLOUDS: IMPACT ON THE THERMAL STRUCTURE AND WATER CYCLE. J. The essential role of water-ice clouds in shaping the thermal structure of the martian atmosphere has been long the evolution of the water cycle in details. Since then, many evidences of the radiative effect of clouds

Madeleine, Jean-Baptiste

137

Water Decontamination With New Porous Oxide Photocatalysts  

NASA Astrophysics Data System (ADS)

Water pollution is major environmental problem worldwide. Many common industrial organic compounds that make their way into water systems can be carcinogenic at trace levels and are difficult and costly to remove completely with conventional technologies. Heterogeneous photocatalysts like titanium dioxide have the potential to completely mineralize organic compounds in water under ultraviolet light. We are proposing to develop new porous oxide semiconductor materials made up of titanium and niobium mixed oxide nanocomposites. The porous catalysts retain high catalytic activity while being easy to handle and filter out of product streams. New synthetic methods are to be developed that optimize physical properties and the catalyst's ability to photo-degrade organic contaminants in water.

Zarei Chaleshtori, M.; Saupe, G. B.

2008-12-01

138

Secular Changes in Great Lakes Water Level Seasonal Cycles  

Microsoft Academic Search

The three primary scales of Great Lakes water level fluctuations are interannual, seasonal, and episodic. Of these three, the seasonal water level fluctuations have received relatively little attention. The Great Lakes water levels have a well defined seasonal cycle driven primarily by snowmelt in the spring and summer and lake evaporation in the fall and winter. The present average seasonal

Frank H. Quinn

2002-01-01

139

Water in Terrestrial Planets: Always an Oxidant?  

NASA Technical Reports Server (NTRS)

Water is commonly assumed to be an oxidant in many planetary settings. Because it can affect Fe-FeO-Fe2O3 equilibria and thus bulk compositional properties of planets and asteroids, this is an important ingredient to understand. The role of water in two settings will be addressed - magmas, and mantles during accretion - along with the implications for planet growth and evolution.

Righter, K.

2004-01-01

140

Plans and Activities for NASA's Global Water Cycle Research  

NASA Astrophysics Data System (ADS)

Strictly speaking, the water (or hydrologic) cycle is by definition a global phenomenon. To observe, analyze, characterize, understand, and predict its structure and variations requires a coordinated, global effort of observations as well as global prediction systems which can assimilate and predict key fluxes and quantities. The National Aeronautics and Space Administration (NASA) has the unique capability of space-based experimental and research measurements that observe the Earth's system as well as core modelling activities to exploit these space-based observations for assimilation in diagnostic studies and initialization in weather and climate predictions. A summary of NASA's current water-cycle activities and implementation plans will be presented. Currently, NASA's Global Water and Energy Cycle and Terrestrial Hydrology (formally known as the Land Surface Hydrology) Programs are the key funding sources which support relevant scientific research. These programs not only fund individual scientists, but also support large-scale field missions (for example the Cold Land Processes Experiment, CLPX, and the Soil Moisture Experiment, SMEx) which are critical for calibration/validation of space instruments and retrievals as well as gaining fundamental understanding of local-scale processes which comprise the global system. In addition, a new initiative for Water and Energy cycle Research (WatER) is being formulated which responds to the recent charge of USGCRP and NRC scientific panels calling for focused and prioritized research plans that serve to make significant strides in our understanding and prediction of the global water cycle. Following NASA's unique vocation, the WatER initative sets priorities for science/research support for key observable quantities of the water cycle (precipitation and surface wetness) whose instrument technology is tactable and scientfic end-returns not only benefit water-cycle predictions, but also serve to benefit other critical cross-cutting themes (such as the carbon cycle).

Schlosser, C. A.

2002-05-01

141

A Porphyrin-Stabilized Iridium Oxide Water Oxidation Catalyst  

SciTech Connect

Colloidal solutions of iridium oxide hydrate (IrO{sub 2}·NH{sub 2}O) were formed using porphyrin stabilizers bearing malonate-like functional groups at each of the four meso positions of the porphyrin ring. Cyclic voltammetry and monitoring of solution oxygen concentrations under constant applied potential demonstrated the electrochemical catalytic activity of the porphyrin–IrO{sub 2}·NH{sub 2}O complexes for the oxidation of water to oxygen. Quenching of the porphyrin fluorescence in the complex implies strong interaction between the porphyrin and the IrO{sub 2}·NH{sub 2}O. These results mark a step toward developing a porphyrin-based photoanode for use in a photoelectrochemical water-splitting cell.

Sherman, Ben; Pillai, Smitha; Kodis, Gerdenis; Bergkamp, Jesse; Mallouk, Thomas E.; Gust, Devens; Moore, Thomas A.; Moore, Ana L.

2011-01-01

142

Oxidative treatment of pharmaceuticals in water  

Microsoft Academic Search

Environmentally relevant pharmaceuticals were chosen according to human consumption and occurrence in the aquatic environment like sewage plant effluents, rivers and groundwater to investigate their behavior during oxidative water treatment. Derived from data compilation in literature the lipid lowering agent clofibric acid and the analgesic agents ibuprofen and diclofenac were selected. Analyses of the acidic compounds were carried out after

C. Zwiener; F. H. Frimmel

2000-01-01

143

Supercritical water oxidation of landfill leachate  

SciTech Connect

Highlights: > Thermal analysis of NH{sub 3} in supercritical water oxidation reaction. > Research on the catalytic reaction of landfill leachate by using response surface method. > Kinetic research of supercritical water oxidation of NH{sub 3} with and without MnO{sub 2} catalyst. - Abstract: In this paper, ammonia as an important ingredient in landfill leachate was mainly studied. Based on Peng-Robinson formulations and Gibbs free energy minimization method, the estimation of equilibrium composition and thermodynamic analysis for supercritical water oxidation of ammonia (SCWO) was made. As equilibrium is reached, ammonia could be totally oxidized in SCW. N{sub 2} is the main product, and the formation of NO{sub 2} and NO could be neglected. The investigation on SCWO of landfill leachate was conducted in a batch reactor at temperature of 380-500 deg. C, reaction time of 50-300 s and pressure of 25 MPa. The effect of reaction parameters such as oxidant equivalent ratio, reaction time and temperature were investigated. The results showed that COD and NH{sub 3} conversion improved as temperature, reaction time and oxygen excess increased. Compared to organics, NH{sub 3} is a refractory compound in supercritical water. The conversion of COD and NH{sub 3} were higher in the presence of MnO{sub 2} than that without catalyst. The interaction between reaction temperature and time was analyzed by using response surface method (RSM) and the results showed that its influence on the NH{sub 3} conversion was relatively insignificant in the case without catalyst. A global power-law rate expression was regressed from experimental data to estimate the reaction rate of NH{sub 3}. The activation energy with and without catalyst for NH{sub 3} oxidation were 107.07 {+-} 8.57 kJ/mol and 83.22 {+-} 15.62 kJ/mol, respectively.

Wang Shuzhong, E-mail: s_z_wang@yahoo.cn [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China); Guo Yang [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China); Chen Chongming [Hebei Electric Power Research Institute, Shijizhuang, Hebei 050021 (China); Zhang Jie; Gong Yanmeng; Wang Yuzhen [School of Energy and Power Engineering of Xi' an Jiao Tong University, Xi'an 710049 (China)

2011-09-15

144

Water Quality Testing in your Local Water Cycle  

NSDL National Science Digital Library

Students analyze local water chemistry by identifying and collecting local water samples, deciding upon questions they want to answer about their local water sources, and then performing simple water quality tests on their samples.

Jennifer L. B. Anderson

145

Massive swings in the marine N cycle during the Great Oxidation Event  

NASA Astrophysics Data System (ADS)

Nitrogen isotope values preserved in sedimentary organic matter show a general increase sometime between 2.5 and 2.1 Ga (e.g., Beaumont and Robert, 1999), coincident with the initial rise of O2 in the Earth's atmosphere (the Great Oxidation Event; Holland, 2002). This shift is commonly interpreted to represent a major change in the global N cycle related to oxygenation of Earth's surficial environments. Despite the invoked connection between ?15N values and the GOE, high resolution studies of N isotopes across this critical time interval are lacking. Here we present ?15N data for kerogens from the ~2.32 Ga Rooihoogte and Timeball Hill formations, South Africa. These sediments were deposited during the GOE, when the disappearance of S-isotope mass-independent fractionation first indicates O2 levels consistently greater than 10-5 times present atmospheric level (e.g., Bekker et al., 2004). We interpret these data in the context of paleoredox indicators for ocean chemistry (Fe speciation analysis), further allowing us to explore changes in the N cycle under evolving environmental conditions. Our data show unusually 15N-depleted values (down to -13‰) at the bottom of the stratigraphic succession, in sediments deposited under a water column with dynamic redox conditions that fluctuated between oxic, ferruginous, and sulfidic states (possibly related to a shifting chemocline). The ?15N values increase dramatically (up to +14‰) across the boundary between the Rooihoogte and Timeball Hill formations, before settling to near modern values (+6‰) in sediments that were deposited under persistently oxygenated waters. We suggest that this record reflects the permanent onset of the oxidative N cycle (nitrification), which would have produced sufficient oxidized N compounds to establish denitrification and anammox as the dominant controls on ?15N values of marine organic matter. We also estimate the N fluxes required to produce this record using a global marine nitrogen cycle model.

Zerkle, A.; Poulton, S.; Newton, R.; Claire, M.; Bekker, A.

2012-12-01

146

Method of removing oxidized contaminants from water  

DOEpatents

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II).

Amonette, James E. (Richland, WA); Fruchter, Jonathan S. (Richland, WA); Gorby, Yuri A. (Richland, WA); Cole, Charles R. (West Richmond, WA); Cantrell, Kirk J. (West Richmond, WA); Kaplan, Daniel I. (Richland, WA)

1998-01-01

147

Method of removing oxidized contaminants from water  

DOEpatents

The present invention is a method for removing oxidized contaminant(s) from water. More specifically, the invention has the steps of contacting water containing the oxidized contaminant(s) with a layered aluminosilicate having Fe(II). The aluminosilicate may contain naturally occurring Fe(II), or the Fe(II) may be produced by reducing Fe(III) that is initially present. Reduction may be either by exposure to a chemical or biological reductant. Contacting the water containing oxidized contaminant(s) may be by (1) injection of Fe(II)-containing layered aluminosilicate, via a well, into a saturated zone where it is likely to intercept the contaminated water; (2) injection of contaminated water into a vessel containing the Fe(II)-bearing layered aluminosilicate; and (3) first reducing Fe(III) in the layered aluminosilicate to Fe(II) by injection of a biological or chemical reductant, into an aquifer or vessel having sufficient Fe(III)-bearing aluminosilicate to produce the necessary Fe(II). 8 figs.

Amonette, J.E.; Fruchter, J.S.; Gorby, Y.A.; Cole, C.R.; Cantrell, K.J.; Kaplan, D.I.

1998-07-21

148

Theoretical investigation of water oxidation processes on small Mn(x)Ti(2-x)O4 (x = 0-2) complexes.  

PubMed

Understanding the water oxidation process on small metal oxide complexes is fundamental for developing photocatalysts for solar fuel production. Titanium oxide and manganese oxide complexes have high potential as components of a cheap, nontoxic, and stable photocatalyst. In this theoretical work, the water oxidation process on Mn(x)Ti(2-x)O4 (x = 0-2) clusters is investigated at the BP86 level of theory using two water molecules and fully saturated systems. In the oxidation cycle using two water molecules, Mn reduces the reaction energy; however, Mn does not reduce the reaction energy on the fully saturated system. When two water molecules are used, the highest reaction energy in the water oxidation cycle is lower than 3 eV, but the highest reaction energy is higher than 3 eV on fully saturated systems except for the pure titanium oxide complex which has a highest reaction energy of 2.56 eV. Dehydrogenation processes in the water oxidation cycle require higher energy than the O-O formation or water adsorption processes. The overall dehydrogenation energy is usually smaller on complexes including at least one Mn atom and it is smallest on the Mn2O4 complex that has two water molecules. Considering the highest reaction energy in the overall water oxidation cycle, water oxidation at the manganese atom of MnTiO4 hydrated with two water molecules is the most favorable in energy. PMID:24673718

Lee, Choongkeun; Aikens, Christine M

2014-09-18

149

Economics of nuclear fuel cycles : option valuation and neutronics simulation of mixed oxide fuels  

E-print Network

In most studies aiming at the economic assessment of nuclear fuel cycles, a primary concern is to keep scenarios economically comparable. For Uranium Oxide (UOX) and Mixed Oxide (MOX) fuels, a traditional way to achieve ...

De Roo, Guillaume

2009-01-01

150

Ch.9 Water Resources ! Hydrologic cycle  

E-print Network

)? ! Evapotranspiration is a collective term (evaporation + transpiration) for all the processes by which water evaporation evaporation transpiration uptake evaporation evaporation #12;Transpiration Capillary rise Vegetated transpiration uptake evaporation evaporation dS/dt=P-ET where dS/dt is the soil water storage

Pan, Feifei

151

The Water Cycle: Snowmelt Runoff to Streams  

NSDL National Science Digital Library

This site describes how snow and ice runoff become surface water and emphasizes how runoff from snowmelt is a major component of the global movement of water. A hydrograph from the U.S. Geological Survey shows a four-year time series of streamflow and illustrates how runoff from snowmelt affects the daily mean values, particularly at certain times of the year.

152

Carbon footprint estimation of municipal water cycle  

Microsoft Academic Search

This research investigates the embodied energy associated with water use. A geographic information system (GIS) was tested using data from Loudoun County, Virginia. The objective of this study is to estimate the embodied energy and carbon emission levels associated with water service at a geographical location and to improve for sustainability planning. Factors that affect the carbon footprint were investigated

Ali A. Bakhshi

2009-01-01

153

EDITORIAL: The global atmospheric water cycle  

Microsoft Academic Search

Water vapour plays a key role in the Earth's energy balance. Almost 50% of the absorbed solar radiation at the surface is used to cool the surface, through evaporation, and warm the atmosphere, through release of latent heat. Latent heat is the single largest factor in warming the atmosphere and in transporting heat from low to high latitudes. Water vapour

Lennart Bengtsson

2010-01-01

154

Supercritical water oxidation of ammonium picrate  

SciTech Connect

This study demonstrates the feasibility of using supercritical water oxidation to destroy ammonium picrate. Analyses of reactor effluent composition at various temperatures, residence times, and oxidant concentrations were used to design an improved reactor configuration for achieving destruction with minimum corrosion. The engineering evaluation reactor, a room-sized laboratory scale reactor, was reconfigured to incorporate this design change. Destruction of ammonium picrate with minimized corrosion was demonstrated on this reconfigured reactor. Factors that must be considered in scaling up to pilot plant size are discussed.

LaJeunesse, C.A.; Mills, B.E.; Brown, B.G.

1994-11-01

155

Toward a hydro-political water cycle: virtual water,hydrology and international political economy  

NASA Astrophysics Data System (ADS)

At the light of global food trade, no water cycle can be considered "closed" under a political point of view. While the hydrological cycle is a circular closed environment, if we open up our perspectives to social sciences, we will demonstrate how, thanks to virtual water, it is today possible to elaborate how much water 'enters or leave' any water body under the form crop-export, in terms of " water used for the production of agri-food products'. This new 'hydro-political cycle' will be discussed at the light of different theoretical perspectives: food trade theories, hydrology, international water law, socio-economic metabolism, material flow analysis.

Greco, Francesca

2014-05-01

156

A model for the water-oxidation and recovery systems of the oxygen-evolving complex.  

PubMed

We propose a model for the water-oxidation and recovery systems of the oxygen-evolving complex (OEC) of the photosystem II (PSII) enzyme. The whole system is constructed from two catalytic cycles, conducted as a tandem reaction: (i) a water-oxidation loop uses cerium(IV) ammonium nitrate as an oxidant to activate a dimanganese complex for water-oxidation and thereby liberate a molecule of O2 and (ii) a recovery loop begins with photoinhibition of the dimanganese complex but then uses O2 to reactivate the manganese centre. The net result is a catalytic water-oxidation catalyst that can use self-generated O2 for recovery. PMID:24323354

Yatabe, Takeshi; Kikkawa, Mitsuhiro; Matsumoto, Takahiro; Nakai, Hidetaka; Kaneko, Kenji; Ogo, Seiji

2014-02-28

157

Solar cycle variation of thermospheric nitric oxide at solstice  

NASA Technical Reports Server (NTRS)

A coupled, two-dimensional, chemical-diffusive model of the thermosphere is used to study the role of solar activity in the global distribution of nitric oxide. The model calculates self-consistently the zonally averaged temperature, circulation, and composition for solstice under solar maximum and solar minimum conditions. A decrease of the NO density by a factor of three to four in the E region is predicted from solar maximum to solar minimum. It is found that the main features of the overall morphology and the changes induced by the solar cycle are well reproduced in the model, although some details are not satisfactorily predicted. The sensitivity of the NO distribution to eddy transport and to the quenching of metastable N(2D) atoms by atomic oxygen is also described.

Gerard, J.-C.; Fesen, C. G.; Rusch, D. W.

1990-01-01

158

What Goes Around Comes Around: Water Cycle  

NSDL National Science Digital Library

This resource guide from the Middle School Portal 2 project, written specifically for teachers, provides links to exemplary resources including background information, lessons, career information, and related national science education standards. The resources here will provide you with content information as well as lessons and activities to guide your students to deeper understandings of the nature of water, the need for and intricacies of its management, and why water management issues can be difficult and emotional.

Mary LeFever

159

Estimated Seasonal Cycle of North Atlantic Eighteen Degree Water Volume  

E-print Network

The seasonal cycle in the volume and formation rate of Eighteen Degree Water (EDW) in the North Atlantic is quantified over the 3-yr period from 2004 to 2006. The EDW layer is defined as all waters that have a temperature ...

Forget, Gael

160

GEWEX: The Global Energy and Water Cycle Experiment  

Microsoft Academic Search

The need for better quantitative understanding of energy fluxes and water exchanges is basic to all climate studies, yet our quantitative knowledge of the global hydrological cycle remains surprisingly poor. Evaporation minus precipitation or, similarly, the net flow of water from land to oceans and the net advection of moisture from the marine atmosphere to the terrestrial atmosphere is known

Moustafa T. Chahine

1992-01-01

161

Life cycle water footprints of nonfood biomass fuels in China.  

PubMed

This study presented life cycle water footprints (WFs) of biofuels from biomass in China based on the resource distribution, climate conditions, soil conditions and crop growing characteristics. Life cycle WFs including blue, green and gray water were evaluated for the selected fuel pathways. Geographical differences of water requirements were revealed to be different by locations. The results indicated that water irrigation requirements were significantly different from crop to crop, ranging from 2-293, 78-137, and 17-621 m(3)/ha, for sweet sorghum, cassava, and Jatropha curcas L., respectively. Four biofuel pathways were selected on this basis to analyze the life cycle WF: cassava based bioethanol in Guangxi, sweet sorghum based bioethanol in Northeast China, Jatropha curcal L. based biodiesel in Yunnan and microalgae based biodiesel in Hainan. The life cycle WFs of bioethanol from cassava and sweet sorghum were 3708, and 17?156 m(3) per ton of bioethanol, respectively, whereas for biodiesel produced from Jatropha curcas L. and microalgae, they were 5787, and 31?361 m(3) per ton of biodiesel, respectively. The crop growing stage was the main contributor to the whole life cycle of each pathway. Compared to blue and green water, gray water was significant due to the use of fertilizer during the growing of biomass. From the perspective of the WF, cassava based bioethanol in Guangxi and Jatropha based biodiesel in Yunnan were suitable for promotion, whereas the promotion for microalage based biodiesel in Hainan required improvement on technology. PMID:24400620

Zhang, Tingting; Xie, Xiaomin; Huang, Zhen

2014-04-01

162

Greenlighting photoelectrochemical oxidation of water by iron oxide.  

PubMed

Hematite (?-Fe2O3) is one of just a few candidate electrode materials that possess all of the following photocatalyst-essential properties for scalable application to water oxidation: excellent stability, earth-abundance, suitability positive valence-band-edge energy, and significant visible light absorptivity. Despite these merits, hematite's modest oxygen evolution reaction kinetics and its poor efficiency in delivering photogenerated holes, especially holes generated by green photons, to the electrode/solution interface, render it ineffective as a practical water-splitting catalyst. Here we show that hole delivery and catalytic utilization can be substantially improved through Ti alloying, provided that the alloyed material is present in ultrathin-thin-film form. Notably, the effects are most pronounced for charges photogenerated by photons with energy comparable to the band gap for excitation of Fe(3d)?Fe(3d) transitions (i.e., green photons). Additionally, at the optimum Ti substitution level the lifetimes of surface-localized holes, competent for water oxidation, are extended. Together these changes explain an overall improvement in photoelectrochemical performance, especially enhanced internal quantum efficiencies, observed upon Ti(IV) incorporation. PMID:25414974

Kim, Dong Wook; Riha, Shannon C; DeMarco, Erica J; Martinson, Alex B F; Farha, Omar K; Hupp, Joseph T

2014-12-23

163

Catalytic supercritical water oxidation: Stability of CrâOâ catalyst  

Microsoft Academic Search

Supercritical water oxidation has become a well-known treatment technology for conversion of aqueous wastes. By introducing a catalyst, higher conversion and selectivity to carbon dioxide can be achieved at a lower temperature and at shorter residence times. The stability of chromium oxide in supercritical water was studied to determine the feasibility of using catalysts during supercritical water oxidation. Various process

Sudhir N. V. K. Aki; Zhong-Yi Ding; Martin A. Abraham

1996-01-01

164

Oxidative coupling of methane by water as the oxidant on perovskite oxide catalysts  

Microsoft Academic Search

We found that methane was selectively oxidized by water to give C2 hydrocarbons and hydrogen on ATi1-xBxO3-d (A=Sr, Ba, B=Mg, Ca). The coupling activity and selectivity on SrTi0.4Mg0.6O3-d in the presence of steam was ~95%, which was much higher than that on pure SrTiO3. This suggests that the selective oxidative coupling of methane by water was catalyzed by the oxide

Xiaohong Li; Keiichi Tomishige; Kaoru Fujimoto

1996-01-01

165

Photosynthetic water oxidation: The protein framework  

Microsoft Academic Search

Approximately 20 protein subunits are associated with the PS II complex, not counting subunits of peripheral light-harvesting antenna complexes. However, it is not yet established which proteins specifically are involved in the water-oxidation process. Much evidence supports the concept that the D1\\/D2 reaction center heterodimer not only plays a central role in the primary photochemistry of Photosystem II, but also

Wim F. J. Vermaas; Stenbjörn Styring; Wolfgang P. Schröder; Bertil Andersson

1993-01-01

166

Water oxidation reaction in natural and artificial photosynthetic systems  

SciTech Connect

Understanding the structure and mechanism of water oxidation catalysts is an essential component for developing artificial photosynthetic devices. In the natural water oxidation catalyst, the geometric and electronic structure of its inorganic core, the Mn{sub 4}CaO{sub 5} cluster, has been studied by spectroscopic and diffraction measurements. In inorganic systems, metal oxides seem to be good candidates for water oxidation catalysts. Understanding the reaction mechanism in both natural and oxide-based catalysts will helpin further developing efficient and robust water oxidation catalysts.

Yano, Junko; Yachandra, Vittal [Physical Biosciences Division, Lawrence Berkeley National Laboratory, 1 Cyclotron Rd., Berkeley, CA 94720 (United States)

2013-12-10

167

Life Cycle Assessment of Three Water Scenarios  

E-print Network

Screen DisinfectionFiltrationAeration Reverse Osmosis Microfiltration Aquifer Storage and Recovery the Sea of Cortez Treatment Processes Filtration Reverse Osmosis Steel pipeline conveying water from the Sea of Cortez to Phoenix, AZ #12;Desalination Plant - System Diagram Screen Filtration Reverse Osmosis

Keller, Arturo A.

168

Emerging Contaminants in the Drinking Water Cycle  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-µg/L) in surface, ground and drinking water. The most common...

169

Emerging Contaminants in the Drinking Water Cycle.  

EPA Science Inventory

In the past decade, the scientific community and general public have become increasingly aware of the potential for the presence of unregulated, and generally unmonitored contaminants, found at low concentrations (sub-¿g/L) in surface, ground and drinking water. The most common...

170

Biotransformations Utilizing ?-Oxidation Cycle Reactions in the Synthesis of Natural Compounds and Medicines  

PubMed Central

?-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the ?-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via ?-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described. PMID:23443116

Œwizdor, Alina; Panek, Anna; Milecka-Tronina, Natalia; Ko?ek, Teresa

2012-01-01

171

Biotransformations utilizing ?-oxidation cycle reactions in the synthesis of natural compounds and medicines.  

PubMed

?-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the ?-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via ?-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described. PMID:23443116

Swizdor, Alina; Panek, Anna; Milecka-Tronina, Natalia; Ko?ek, Teresa

2012-01-01

172

[Comment on ``GEWEX: The Global Energy and Water Cycle Experiment''] Global water balance uncertainty  

Microsoft Academic Search

I am surprised by the opening remarks of Moustafa T. Chahine in his article, ``GEWEX: The Global Energy and Water Cycle Experiment'' (Eos, January 14, 1992, p. 9), which stated that ``our quantitative knowledge of the global hydrological cycle remains surprisingly poor. Evaporation minus precipitation or, similarly, the net flow of water from land to oceans and the net advection

Turgot Dincer

1992-01-01

173

Serpentine and the subduction zone water cycle  

Microsoft Academic Search

Abstract This study explores a chemo-thermo-dynamic subduction zone model that solves for slab dehydration during subduction. We investigate how,changes in the incoming,plate’s hydration and thermal structure may,effect the efficiency of sub-arc water release from sediments, crust, and serpentinized mantle. We find that serpentinized lithospheric mantle may not only be an important fluid source to trigger arc melting but is also

J. P. Morgan; M. Hort; J. A. D. Connolly

2004-01-01

174

Serpentine and the subduction zone water cycle  

Microsoft Academic Search

This study explores a chemo-thermo-dynamic subduction zone model that solves for slab dehydration during subduction. We investigate how changes in the incoming plate's hydration and thermal structure may effect the efficiency of sub-arc water release from sediments, crust, and serpentinized mantle. We find that serpentinized lithospheric mantle may not only be an important fluid source to trigger arc melting but

Lars H Rüpke; Jason Phipps Morgan; Matthias Hort; James A. D Connolly

2004-01-01

175

Enhanced Oxidation Catalysts for Water Reclamation  

NASA Technical Reports Server (NTRS)

This effort seeks to develop and test high-performance, long operating life, physically stable catalysts for use in spacecraft water reclamation systems. The primary goals are to a) reduce the quantity of expendable water filters used to purify water aboard spacecraft, b) to extend the life of the oxidation catalysts used for eliminating organic contaminants in the water reclamation systems, and c) reduce the weight/volume of the catalytic oxidation systems (e.g. VRA) used. This effort is targeted toward later space station utilization and will consist of developing flight-qualifiable catalysts and long-term ground tests of the catalyst prior to their utilization in flight. Fixed -bed catalytic reactors containing 5% platinum on granular activated carbon have been subjected to long-term dynamic column tests to measure catalyst stability vs throughput. The data generated so far indicate that an order of magnitude improvement can be obtained with the treated catalysts vs the control catalyst, at only a minor loss (approx 10%) in the initial catalytic activity.

Jolly, Clifford D.

1999-01-01

176

Supercritical water oxidation of products of human metabolism  

NASA Technical Reports Server (NTRS)

Although the efficient destruction of organic material was demonstrated in the supercritical water oxidation process, the reaction kinetics and mechanisms are unknown. The kinetics and mechanisms of carbon monoxide and ammonia oxidation in and reaction with supercritical water were studied experimentally. Experimental oxidation of urine and feces in a microprocessor controlled system was performed. A minaturized supercritical water oxidation process for space applications was design, including preliminary mass and energy balances, power, space and weight requirements.

Tester, Jefferson W.; Orge A. achelling, Richard K. ADTHOMASSON; Orge A. achelling, Richard K. ADTHOMASSON

1986-01-01

177

Theoretical and experimental investigation of an ammonia–water power and refrigeration thermodynamic cycle  

Microsoft Academic Search

A combined thermal power and cooling cycle proposed by Goswami is under intensive investigation, both theoretically and experimentally. The proposed cycle combines the Rankine and absorption refrigeration cycles, using a binary ammonia–water mixture as the working fluid. This cycle can be used as a bottoming cycle using waste heat from a conventional power cycle or an independent cycle using low

G Tamm; D. Y Goswami; S Lu; A. A Hasan

2004-01-01

178

DIURNAL CYCLE OF PRECIPITABLE WATER VAPOR OVER SPAIN  

SciTech Connect

Despite the importance of the diurnal cycle of precipitable water vapor (PWV), its knowledge is very limited due to the lack of data with sufficient temporal resolution. Currently, from GPS receivers, PWV can be obtained with high temporal resolution in all weather conditions for all hours of the day. In this study we have calculated the diurnal cycle of PWV for ten GPS stations over Spain. The minimum value is reached approximately at the same time at all the stations, ~0400-0500 UTC, whereas the maximum is reached in the second half of the day, but with a larger dispersion of its occurrence between stations. The amplitude of the cycle ranges between 0.72 mm and 1.78 mm. The highest values are recorded at the stations on the Mediterranean coast, with a doubling of the values of the stations on the Atlantic coast or inland. The amplitude of the PWV cycle, relative to the annual mean value, ranges between 8.8 % on the Mediterranean coast and 3.6 % on the Atlantic coast. Two distinctly different seasonal diurnal cycles have been identified, one in winter and other in summer, with spring and autumn being only transition states. The winter cycle is quite similar at all locations, whereas in summer, local effects are felt strongly, making the diurnal cycle quite different between stations. The amplitude of the summer cycle is 1.69 mm, it is almost double the winter one (0.93 mm). Analogous to the annual cycles, the seasonal cycles of the different stations are more similar during the night and early morning hours than during the afternoon. The observed features of the PWV diurnal cycle are explained in a qualitative way on the basis of the air temperature, the transport of moisture by local winds, and the turbulent vertical mixing.

Ortiz de Galisteo, J. P.; Cachorro, V. E.; Toledano, C.; Torres, B.; Laulainen, Nels S.; Bennouna, Yasmine; de Frutos, A. M.

2011-05-20

179

Black Carbon in the Soil Carbon Cycle: Is it an Oxidation Resistant End-Product?  

E-print Network

Black Carbon in the Soil Carbon Cycle: Is it an Oxidation Resistant End-Product? Simone;1 Introduction Soils represent a large carbon pool in the global carbon cycle. Estimates suggest that this pool is twice as large as the atmospheric pool. But its role in the global carbon cycle remains unclear

Fischlin, Andreas

180

Anaerobic Ammonium Oxidation (Anammox) A new sink in the marine nitrogen cycle  

E-print Network

Term paper Anaerobic Ammonium Oxidation (Anammox) ­ A new sink in the marine nitrogen cycle. By finding a new key process in the marine nitrogen cycle the question arises how important it is in a global be discussed. By looking at the "new" marine nitrogen cycle we are developing the foundation for discussing

Fischlin, Andreas

181

Water defluoridation by aluminium oxide-manganese oxide composite material.  

PubMed

In this study, aluminium oxide-manganese oxide (AOMO) composite material was synthesized, characterized, and tested for fluoride removal in batch experiments. AOMO was prepared from manganese(II) chloride and aluminium hydroxide. The surface area of AOMO was found to be 30.7m2/g and its specific density was determined as 2.78 g/cm3. Detailed investigation of the adsorbent by inductively coupled plasma-optical emission spectrometry, inductively coupled plasma-mass spectrometry, and ion chromatography (for sulphate only) showed that it is composed of Al, Mn, SO4, and Na as major components and Fe, Si, Ca, and Mg as minor components. Thermogravimetric analysis was used to study the thermal behaviour of AOMO. X-ray diffraction analysis showed that the adsorbent is poorly crystalline. The point of zero charge was determined as 9.54. Batch experiments (by varying the proportion of MnO, adsorbent dose, contact time, initial F concentration, and raw water pH) showed that fluoride removal efficiency ofAOMO varied significantly with percentage of MnO with an optimum value of about I11% of manganese oxide in the adsorbent. The optimum dose of the adsorbent was 4 g/L which corresponds to the equilibrium adsorption capacity of 4.8 mg F-/g. Both the removal efficiency and adsorption capacity showed an increasing trend with an increase in initial fluoride concentration of the water. The pH for optimum fluoride removal was found to be in the range between 5 and 7. The adsorption data were analysed using the Freundlich, Langmuir, and Dubinirn-Radushkevich models. The minimum adsorption capacity obtained from the non-linear Freundlich isotherm model was 4.94 mg F-/g and the maximum capacity from the Langmuir isotherm method was 19.2mg F-/g. The experimental data of fluoride adsorption on AOMO fitted well to the Freundlich isotherm model. Kinetic studies showed that the adsorption is well described by a non-linear pseudo-second-order reaction model with an average rate constant of 3.1 x 10(-2) g/min mg. It is concluded that AOMO is a highly promising adsorbent for the removal of excess fluoride from drinking water. PMID:24956783

Alemu, Sheta; Mulugeta, Eyobel; Zewge, Feleke; Chandravanshi, Bhagwan Singh

2014-08-01

182

Fundamental kinetics of methane oxidation in supercritical water. Summary report  

SciTech Connect

Fundamental understanding of the oxidation of compounds in supercritical water is essential for the design, development and operation of a supercritical water oxidation unit. Previous work in our group determined the oxidation kinetics of carbon monoxide and ethanol in supercritical water for temperatures ranging from 400 to 540 C. Oxidation studies of methane up to 700 C have recently been completed and are presented in this report. Theoretical studies of fundamental kinetics and mechanistic pathways for the oxidation of methane in supercritical water are discussed. Application of current gas phase elementary reaction models are briefly presented and their limitations discussed.

Webley, P.A.; Tester, J.W. [Massachusetts Inst. of Tech., Cambridge, MA (United States). Dept. of Chemical Engineering

1989-05-22

183

Supercritical water oxidation of chemical agents, and solid propellants  

Microsoft Academic Search

Supercritical water oxidation (SCWO), also referred to as hydrothermal oxidation (HTO), is a developing technology for the destruction of hazardous and nonhazardous wastes. SCWO destroys combustible materials using an oxidant in water at temperatures in the range of 350°C (662°F) to 600°C (1112°F) and pressures of 17 MPa (2500 psi) or greater. General Atomics and its subcontractors are currently conducting

M. H. Spritzer; D. A. Hazlebeck; K. W. Downey

1995-01-01

184

Land surface water cycles observed with satellite sensors  

NASA Technical Reports Server (NTRS)

Acceleration of the global water cycle may lead to increased global precipitation, faster evaporation and a consequent exacerbation of hydrologic extreme. In the U.S. national assessment of the potential consequences of climate variability and change, two GCMs (CGCM1 and HadCM2) show a large increase in precipitation in the future over the southwestern U.S. particularly during winter (Felzer and Heard, 1999). Increased precipitation potentially has important impacts on agricultural and water use in the southeast U.S. (Hatch et al., 1999) and in the central Great Plains (Nielsen, 1997). A hurricane model predicts a 40% precipitation increase for severe hurricanes affecting southeastern Florida, which provokes substantially greater flooding that could negate most of the benefits of present water-management practices in this basin (Gutowski et al., 1994). Thus, it is important to observe the hydroclimate on a continuous longterm basis to address the question of increased precipitation in the enhanced water cycle.

Nghiem, Son V.; Njoku, E. G.; Brakenridge, G. R.; Kim, Y.

2005-01-01

185

Coupled reductive and oxidative sulfur cycling in the phototrophic plate of a meromictic lake.  

PubMed

Mahoney Lake represents an extreme meromictic model system and is a valuable site for examining the organisms and processes that sustain photic zone euxinia (PZE). A single population of purple sulfur bacteria (PSB) living in a dense phototrophic plate in the chemocline is responsible for most of the primary production in Mahoney Lake. Here, we present metagenomic data from this phototrophic plate--including the genome of the major PSB, as obtained from both a highly enriched culture and from the metagenomic data--as well as evidence for multiple other taxa that contribute to the oxidative sulfur cycle and to sulfate reduction. The planktonic PSB is a member of the Chromatiaceae, here renamed Thiohalocapsa sp. strain ML1. It produces the carotenoid okenone, yet its closest relatives are benthic PSB isolates, a finding that may complicate the use of okenone (okenane) as a biomarker for ancient PZE. Favorable thermodynamics for non-phototrophic sulfide oxidation and sulfate reduction reactions also occur in the plate, and a suite of organisms capable of oxidizing and reducing sulfur is apparent in the metagenome. Fluctuating supplies of both reduced carbon and reduced sulfur to the chemocline may partly account for the diversity of both autotrophic and heterotrophic species. Collectively, the data demonstrate the physiological potential for maintaining complex sulfur and carbon cycles in an anoxic water column, driven by the input of exogenous organic matter. This is consistent with suggestions that high levels of oxygenic primary production maintain episodes of PZE in Earth's history and that such communities should support a diversity of sulfur cycle reactions. PMID:24976102

Hamilton, T L; Bovee, R J; Thiel, V; Sattin, S R; Mohr, W; Schaperdoth, I; Vogl, K; Gilhooly, W P; Lyons, T W; Tomsho, L P; Schuster, S C; Overmann, J; Bryant, D A; Pearson, A; Macalady, J L

2014-09-01

186

Nitrous Oxide Cycling and its Isotopic Signatures in South West Pacific Ocean  

NASA Astrophysics Data System (ADS)

Nitrous oxide (N2O) is a significant greenhouse gas and is also involved in ozone depletion. The contribution of N2O to both these processes is expected to increase this century. The ocean contributes about 30% to the atmospheric N2O budget so there is strong interest in the oceanic N2O cycle. In the ocean N2O is produced via a number of different processes (e.g. bacterial nitrification, and denitrification). While coastal regions are well-studied there are limited data available for open ocean N2O especially in the Southern Ocean, with few studies of the relative contribution of different bacterial processes. Here we apply new stable isotope techniques and present a detailed overview of the distribution and fate of dissolved nitrous oxide from sampling sites in the southwest Pacific Ocean near New Zealand. Samples for nitrous oxide and nutrients were collected along the depth profiles from two biophysical mooring stations (subtropical and sub- Antarctic), four Geotraces stations (GP13, subtropical Pacific) and two bloom voyage stations in the subtropical front and subtropical pacific waters. The N2O saturation ranged from near equilibrium with air at the surface to a maximum value in the oxygen minimum zone. Thus the surface water masses are not a significant sink or atmospheric source for N2O .Multi-isotope characterization of N2O including d15Nbulk, d18O, d15N? and its site preference (SP, the difference between d15N? and d15N?)indicates that nitrification is the primary process responsible for nitrous oxide production in oxic waters whereas coupling between nitrification and denitrification may be an important mechanism for production in the oxygen minimum zone with a minor contribution by nitrification.

Mullungal, M.; Van Hale, R.; Frew, R. D.; Law, C. S.

2013-12-01

187

Supercritical water oxidation technology for DWPF  

SciTech Connect

At the request of Mr. H.L. Brandt and others in the Savannah River Field Office High Level Waste Division office, DWPF, and SRL personnel have reviewed two potential applications for supercritical water oxidation technology in DWPF. The first application would replace the current hydrolysis process by destroying the organic fractions of the precipitated cesium / potassium tetraphenylborate slurry. The second application pertains to liquid benzene destruction. After a thorough evaluation the first application is not recommended. The second is ready to be tested if needed.

Carter, J.T.; Gentilucci, J.A.

1992-02-07

188

A Seamless Framework for Global Water Cycle Monitoring and Prediction  

NASA Astrophysics Data System (ADS)

The Global Earth Observation System of Systems (GEOSS) Water Strategy ('From Observations to Decisions') recognizes that 'water is essential for ensuring food and energy security, for facilitating poverty reduction and health security, and for the maintenance of ecosystems and biodiversity', and that water cycle data and observations are critical for improved water management and water security - especially in less developed regions. The GEOSS Water Strategy has articulated a number of goals for improved water management, including flood and drought preparedness, that include: (i) facilitating the use of Earth Observations for water cycle observations; (ii) facilitating the acquisition, processing, and distribution of data products needed for effective management; (iii) providing expertise, information systems, and datasets to the global, regional, and national water communities. There are several challenges that must be met to advance our capability to provide near real-time water cycle monitoring, early warning of hydrological hazards (floods and droughts) and risk assessment under climate change, regionally and globally. Current approaches to monitoring and predicting hydrological hazards are limited in many parts of the world, and especially in developing countries where national capacity is limited and monitoring networks are inadequate. This presentation describes the development of a seamless monitoring and prediction framework at all time scales that allows for consistent assessment of water variability from historic to current conditions, and from seasonal and decadal predictions to climate change projections. At the center of the framework is an experimental, global water cycle monitoring and seasonal forecast system that has evolved out of regional and continental systems for the US and Africa. The system is based on land surface hydrological modeling that is driven by satellite remote sensing precipitation to predict current hydrological conditions, flood potential and the state of drought. Seasonal climate model forecasts are downscaled and bias-corrected to drive the land surface model to provide hydrological forecasts and drought products out 6-9 months. The system relies on historic reconstructions of water variability over the 20th century, which forms the background climatology to which current conditions can be assessed. Future changes in water availability and drought risk are quantified based on bias-corrected and downscaled climate model projections that are used to drive the land surface models. For regions with lack of on-the-ground data we are field-testing low-cost environmental sensors and along with new satellite products for terrestrial hydrology and vegetation, integrating these into the system for improved monitoring and prediction. We provide an overview of the system and some examples of real-world applications to flood and drought events, with a focus on Africa.

Sheffield, J.; Wood, E. F.; Chaney, N.; Fisher, C. K.; Caylor, K. K.

2013-12-01

189

Multimodal Science Teachers' Discourse in Modeling the Water Cycle  

ERIC Educational Resources Information Center

The paper presents an intensive study of a micro-event aiming at the characterization of teacher's discourse from a multimodal communication perspective in a secondary school science classroom dealing with the topic of "water cycle." The research addresses the following questions: (a) What communicative modes are used by the teacher?, (b) what…

Marquez, Conxita; Izquierdo, Merce; Espinet, Mariona

2006-01-01

190

GEWEX - The Global Energy and Water Cycle Experiment  

Microsoft Academic Search

GEWEX, which is part of the World Climate Research Program, has as its goal an order-of-magnitude improvement in the ability to model global precipitation and evaporation and furnish an accurate assessment of the sensitivity of atmospheric radiation and clouds. Attention will also be given to the response of the hydrological cycle and water resources to climate change. GEWEX employs a

M. T. Chahine

1992-01-01

191

Energy and Water Cycle Components in Regional Forecasts Final Report  

Microsoft Academic Search

For the first period of the special project we investigated the characteristics of the water cycle com- ponents simulated with the regional model REMO. For the second period our studies focussed on the high resolution regional model HRM. REMO is based on the former Europamodell of the Ger- man Weather Service (DWD), whereas HRM is a regional version of the

Burkhardt Rockel

192

Modeling of the Global Water Cycle - Analytical Models  

Microsoft Academic Search

Both numerical and analytical models of coupled atmosphere and its underlying ground components (land, ocean, ice) are useful tools for modeling the global and regional water cycle. Unlike complex three-dimensional climate models, which need very large computing resources and involve a large number of complicated interactions often difficult to interpret, analytical models are able to provide more direct and intuitive

Yongqiang Liu; Roni Avissar

193

PHOTOREACTIONS IN SURFACE WATERS AND THEIR ROLE IN BIOGEOCHEMICAL CYCLES  

EPA Science Inventory

During the past decade significant interest has developed in the influence of photochemical reactions on biogeochemical cycles in surface waters of lakes and the sea. A major portion of recent research on these photoreactions has focused on the colored component of dissolved org...

194

Containment system for supercritical water oxidation reactor  

DOEpatents

A system for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary.

Chastagner, Philippe (3134 Natalie Cir., Augusta, GA 30909-2748)

1994-01-01

195

Containment system for supercritical water oxidation reactor  

DOEpatents

A system is described for containment of a supercritical water oxidation reactor in the event of a rupture of the reactor. The system includes a containment for housing the reaction vessel and a communicating chamber for holding a volume of coolant, such as water. The coolant is recirculated and sprayed to entrain and cool any reactants that might have escaped from the reaction vessel. Baffles at the entrance to the chamber prevent the sprayed coolant from contacting the reaction vessel. An impact-absorbing layer is positioned between the vessel and the containment to at least partially absorb momentum of any fragments propelled by the rupturing vessel. Remote, quick-disconnecting fittings exterior to the containment, in cooperation with shut-off valves, enable the vessel to be isolated and the system safely taken off-line. Normally-closed orifices throughout the containment and chamber enable decontamination of interior surfaces when necessary. 2 figures.

Chastagner, P.

1994-07-05

196

Fourier transform infrared difference spectroscopy for studying the molecular mechanism of photosynthetic water oxidation  

PubMed Central

The photosystem II reaction center mediates the light-induced transfer of electrons from water to plastoquinone, with concomitant production of O2. Water oxidation chemistry occurs in the oxygen-evolving complex (OEC), which consists of an inorganic Mn4CaO5 cluster and its surrounding protein matrix. Light-induced Fourier transform infrared (FTIR) difference spectroscopy has been successfully used to study the molecular mechanism of photosynthetic water oxidation. This powerful technique has enabled the characterization of the dynamic structural changes in active water molecules, the Mn4CaO5 cluster, and its surrounding protein matrix during the catalytic cycle. This mini-review presents an overview of recent important progress in FTIR studies of the OEC and implications for revealing the molecular mechanism of photosynthetic water oxidation. PMID:23734156

Chu, Hsiu-An

2013-01-01

197

INTRODUCTION: Anticipated changes in the global atmospheric water cycle  

NASA Astrophysics Data System (ADS)

The atmospheric branch of the water cycle, although containing just a tiny fraction of the Earth's total water reserves, presents a crucial interface between the physical climate (such as large-scale rainfall patterns) and the ecosystems upon which human societies ultimately depend. Because of the central importance of water in the Earth system, the question of how the water cycle is changing, and how it may alter in future as a result of anthropogenic changes, present one of the greatest challenges of this century. The recent Intergovernmental Panel on Climate Change report on Climate Change and Water (Bates et al 2008) highlighted the increasingly strong evidence of change in the global water cycle and associated environmental consequences. It is of critical importance to climate prediction and adaptation strategies that key processes in the atmospheric water cycle are precisely understood and determined, from evaporation at the surface of the ocean, transport by the atmosphere, condensation as cloud and eventual precipitation, and run-off through rivers following interaction with the land surface, sub-surface, ice, snow and vegetation. The purpose of this special focus issue of Environmental Research Letters on anticipated changes in the global atmospheric water cycle is to consolidate the recent substantial advances in understanding past, present and future changes in the global water cycle through evidence built upon theoretical understanding, backed up by observations and borne out by climate model simulations. Thermodynamic rises in water vapour provide a central constraint, as discussed in a guest editorial by Bengtsson (2010). Theoretical implications of the Clausius-Clapeyron equation are presented by O'Gorman and Muller (2010) and with reference to a simple model (Sherwood 2010) while observed humidity changes confirm these anticipated responses at the land and ocean surface (Willett et al 2008). Rises in low-level moisture are thought to fuel an intensification of precipitation (O'Gorman and Schneider 2009) and analysis of observed and simulated changes in extreme rainfall for Europe (Lenderink and van Mijgaard 2008) and over tropical oceans by Allan et al (2010) appear to corroborate this. Radiative absorption by water vapour (Previdi 2010, Stephens and Ellis 2008) also provides a thermodynamic feedback on the water cycle, and explains why climate model projections of global precipitation and evaporation of around 1-3% K-1 are muted with respect to the expected 7% K-1 increases in low-level moisture. Climate models achieve dynamical responses through reductions in strength of the Walker circulation (Vecchi et al 2006) and small yet systematic changes in the atmospheric boundary layer over the ocean that modify evaporation (Richter and Xie 2008). A further consequence is anticipated sub-tropical drying (Neelin et al 2006, Chou et al 2007); Allan et al (2010) confirm a decline in dry sub-tropical precipitation while the wet regions become wetter both in model simulations and satellite-based observations. Discrepancies between observed and climate model simulated hydrological response to warming (Wentz et al 2007, Yu and Weller 2007) are of immediate concern in understanding and predicting future responses. Over decadal time-scales it is important to establish whether such discrepancies relate to the observing system, climate modeling deficiencies, or are a statistical artifact of the brevity of the satellite records (Liepert and Previdi 2009). Techniques for extracting information on century-scale changes in precipitation are emerging (Smith et al 2009) but are also subject to severe limitations. Past decadal-scale changes in the water cycle may be further influenced by regionally and temporally varying forcings and resulting feedbacks which must be represented realistically by models (Andrews et al 2009). The radiative impact of aerosols and their indirect effects on clouds and precipitation (Liepert et al 2004) provide an important example. Understanding surface solar 'dimming' and 'brightening' trends in th

Allan, Richard P.; Liepert, Beate G.

2010-06-01

198

The effect of different metal ions between nanolayers of manganese oxide on water oxidation.  

PubMed

Here, we used a strategy to answer to the question that whether Ca(II) ion is specific for water oxidation or not? In the procedure, first we synthesized layered Mn oxides with K(I) between layers and then replaced K(I) by Ca(II), K(I), Mg(II), La(III) or Ni(II). We proposed that Ca(II), K(I), Mg(II), La(III) and Ni(II), between layers are important to form efficient water-oxidizing catalyst, but not specific in water oxidation. However, Cu(II) ions decrease water-oxidizing activity of layered Mn oxides. The result is important to find critical factors in water oxidation by low-cost and environmentally friendly nanolayered Mn oxides. PMID:25463674

Najafpour, Mohammad Mahdi; Isaloo, Mohsen Abbasi; Ghobadi, Mohadeseh Zarei; Amini, Emad; Haghighi, Behzad

2014-12-01

199

Nano-sized layered aluminium or zinc-manganese oxides as efficient water oxidizing catalysts.  

PubMed

Nano-sized layered aluminium or zinc-manganese oxides were synthesized and characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction spectrometry, dynamic light scattering and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. Amounts of dissolved manganese, zinc or aluminium, and water oxidation activities of these oxides were reported and compared with other manganese oxides. A mechanism for oxygen evolution and possible roles for zinc or aluminium ions are also proposed. PMID:22565665

Najafpour, Mohammad Mahdi; Pashaei, Babak; Nayeri, Sara

2012-06-21

200

How Do Higher Temperatures Affect the Water Cycle?  

NSDL National Science Digital Library

This demonstration shows that an increase in temperature will speed up the water cycle. One outcome will be an increase in rainfall. A second outcome will be the increase in total evaporation of water and subsequent drought. Materials required include two aquariums, plastic wrap, 2 clamp lamps with 60 watt light bulbs, pebbles and rocks, modeling clay, blue food coloring, and water. Student worksheets, background information for teachers, and a scoring rubric are included. This is Activity 2 in Too Many Blankets, a module in the lesson series, Potential Consequences of Climate Variability and Change.

2012-08-03

201

Nanoscale manganese oxide within Faujasite zeolite as an efficient and biomimetic water oxidizing catalyst.  

PubMed

Nanoscale manganese oxides within Faujasite zeolite have been synthesized with a simple method and characterized by scanning electron microscopy, X-ray diffraction spectrometry, N(2) adsorption-desorption isotherms, transmission electron microscopy, and atomic absorption spectroscopy. These oxides showed efficient water oxidizing activity in the presence of cerium(IV) ammonium nitrate as a non-oxo transfer oxidant. PMID:22833185

Najafpour, Mohammad Mahdi; Pashaei, Babak

2012-09-14

202

Solar Metal Sulfate-Ammonia Based Thermochemical Water Splitting Cycle for Hydrogen Production  

NASA Technical Reports Server (NTRS)

Two classes of hybrid/thermochemical water splitting processes for the production of hydrogen and oxygen have been proposed based on (1) metal sulfate-ammonia cycles (2) metal pyrosulfate-ammonia cycles. Methods and systems for a metal sulfate MSO.sub.4--NH3 cycle for producing H2 and O2 from a closed system including feeding an aqueous (NH3)(4)SO3 solution into a photoctalytic reactor to oxidize the aqueous (NH3)(4)SO3 into aqueous (NH3)(2)SO4 and reduce water to hydrogen, mixing the resulting aqueous (NH3)(2)SO4 with metal oxide (e.g. ZnO) to form a slurry, heating the slurry of aqueous (NH4)(2)SO4 and ZnO(s) in the low temperature reactor to produce a gaseous mixture of NH3 and H2O and solid ZnSO4(s), heating solid ZnSO4 at a high temperature reactor to produce a gaseous mixture of SO2 and O2 and solid product ZnO, mixing the gaseous mixture of SO2 and O2 with an NH3 and H2O stream in an absorber to form aqueous (NH4)(2)SO3 solution and separate O2 for aqueous solution, recycling the resultant solution back to the photoreactor and sending ZnO to mix with aqueous (NH4)(2)SO4 solution to close the water splitting cycle wherein gaseous H2 and O2 are the only products output from the closed ZnSO4--NH3 cycle.

Huang, Cunping (Inventor); T-Raissi, Ali (Inventor); Muradov, Nazim (Inventor)

2014-01-01

203

Projections of Water-Cycle Change: Uncertainty and Utility.  

NASA Astrophysics Data System (ADS)

Climate models have proven to be invaluable tools to developing scenarios of possible future water resources. However, hydrologic simulation involves complex interactions among many processes, including precipitation, evapotranspiration, infiltration, freezing, and thawing, among others. Furthermore, the modeling of these processes and their interactions remains imperfect. Nonetheless, despite these challenges, some broad features of future water availability have emerged consistently across generations of climate models and future scenarios. One can understand these features on the basis of some fairly simple physical principles, but is this understanding useful? Is the climate community producing the information needed to address future water needs by a growing population? This talk will present perspectives on global and regional water cycles seen in ensemble simulation programs such as the Coupled Model Intercomparison Program (CMIP) for global models and the North American Regional Climate Change Assessment Program (NARCCAP) for regional models. The talk will consider global and regional models as sources of consistency and differences in their projections of climate change, through their representation of physical processes in the water cycle. The talk will also consider how water utilities previously have used climate information and what requirements this imposes on climate simulation. Finally, the talk will explore the question of how well typical diagnoses evaluate climate simulations on the basis of water resource needs, especially those for formulating management, planning and policy decisions.

Gutowski, W. J.

2012-12-01

204

Hydrogen production by water decomposition using a combined electrolytic-thermochemical cycle  

NASA Technical Reports Server (NTRS)

A proposed dual-purpose power plant generating nuclear power to provide energy for driving a water decomposition system is described. The entire system, dubbed Sulfur Cycle Water Decomposition System, works on sulfur compounds (sulfuric acid feedstock, sulfur oxides) in a hybrid electrolytic-thermochemical cycle; performance superior to either all-electrolysis systems or presently known all-thermochemical systems is claimed. The 3345 MW(th) graphite-moderated helium-cooled reactor (VHTR - Very High Temperature Reactor) generates both high-temperature heat and electric power for the process; the gas stream at core exit is heated to 1850 F. Reactor operation is described and reactor innards are illustrated. A cost assessment for on-stream performance in the 1990's is optimistic.

Farbman, G. H.; Brecher, L. E.

1976-01-01

205

Challenges and Opportunities in Water Cycle Research: WCRP Contributions  

NASA Astrophysics Data System (ADS)

The state of knowledge and outstanding challenges and opportunities in global water cycle observations, research and modeling are briefly reviewed to set the stage for the reasons behind the new thrusts promoted by the World Climate Research Programme (WCRP) as Grand Challenges to be addressed on a 5- to 10-year time frame. Those focused on water are led by the GEWEX (Global Energy and Water Exchanges) project. A number of GEWEX science questions are being brought forward within GEWEX and the WCRP under guidance of the Joint Scientific Committee. Here, we describe what are some imperatives and opportunities for major advancements in observations, understanding, modeling and product development for water resources and climate that will enable a wide range of climate services and inform decisions on water resources management and practices.

Trenberth, Kevin E.; Asrar, Ghassem R.

2014-05-01

206

Change in Water Cycle- Important Issue on Climate Earth System  

NASA Astrophysics Data System (ADS)

Change in Water Cycle- Important Issue on Climate Earth System PRATIK KUMAR SINGH1 1BALDEVRAM MIRDHA INSTITUTE OF TECHNOLOGY,JAIPUR (RAJASTHAN) ,INDIA Water is everywhere on Earth and is the only known substance that can naturally exist as a gas, liquid, and solid within the relatively small range of air temperatures and pressures found at the Earth's surface.Changes in the hydrological cycle as a consequence of climate and land use drivers are expected to play a central role in governing a vast range of environmental impacts.Earth's climate will undergo changes in response to natural variability, including solar variability, and to increasing concentrations of green house gases and aerosols.Further more, agreement is widespread that these changes may profoundly affect atmospheric water vapor concentrations, clouds and precipitation patterns.As we know that ,a warmer climate, directly leading to increased evaporation, may well accelerate the hydrological cycle, resulting in an increase in the amount of moisture circulating through the atmosphere.The Changing Water Cycle programmer will develop an integrated, quantitative understanding of the changes taking place in the global water cycle, involving all components of the earth system, improving predictions for the next few decades of regional precipitation, evapotranspiration, soil moisture, hydrological storage and fluxes.The hydrological cycle involves evaporation, transpiration, condensation, precipitation, and runoff. NASA's Aqua satellite will monitor many aspects of the role of water in the Earth's systems, and will do so at spatial and temporal scales appropriate to foster a more detailed understanding of each of the processes that contribute to the hydrological cycle. These data and the analyses of them will nurture the development and refinement of hydrological process models and a corresponding improvement in regional and global climate models, with a direct anticipated benefit of more accurate weather and climate forecasts. Aqua is a major mission of the Earth Observing System (EOS), an international program centered in NASA's Earth Science Enterprise to study the Earth in detail from the unique vantage point of space. Focused on key measurements identified by a consensus of U.S. and international scientists, EOS is further enabling studies of the complex interactions amongst the Earth's land, ocean, air, ice and biological systems. Aqua's contributions to monitoring water in the Earth's environment will involve all six of Aqua's instruments: the Atmospheric Infrared Sounder (AIRS), the Advanced Microwave Sounding Unit (AMSU), the Humidity Sounder for Brazil (HSB), the Advanced Microwave Scanning Radiometer- Earth Observing System (AMSR-E), the Moderate Resolution Imaging Spectroradiometer (MODIS), and Clouds and the Earth's Radiant Energy System (CERES). Frozen water in the oceans, in the form of sea ice, will be examined with both AMSR-E and MODIS data, the former allowing routine monitoring of sea ice at a coarse resolution and the latter providing greater spatial resolution but only under cloud-free conditions. Sea ice can insulate the underlying liquid water against heat loss to the often frigid overlying polar atmosphere and also reflects sunlight that would otherwise be available to warm the ocean. AMSR-E measurements will allow the routine derivation of sea ice concentrations in both polar regions, through taking advantage of the marked contrast in microwave emissions of sea ice and liquid water. This will continue, with improved resolution and accuracy, a 22-year satellite record of changes in the extent of polar ice. MODIS, with its finer resolution, will permit the identification of individual ice flows, when unobscured by clouds. AMSR-E and MODIS will also provide monitoring, the AIRS/AMSU/HSB combination will provide more-accurate space-based measurements of atmospheric temperature and water vapor than have ever been obtained before, with the highest vertical resolution to date as well. Since water vapor is the Earth's primary greenhouse gas and co

Singh, Pratik

207

Electrode-assisted catalytic water oxidation by a flavin derivative  

NASA Astrophysics Data System (ADS)

The success of solar fuel technology relies on the development of efficient catalysts that can oxidize or reduce water. All molecular water-oxidation catalysts reported thus far are transition-metal complexes, however, here we report catalytic water oxidation to give oxygen by a fully organic compound, the N(5)-ethylflavinium ion, Et-Fl+. Evolution of oxygen was detected during bulk electrolysis of aqueous Et-Fl+ solutions at several potentials above +1.9 V versus normal hydrogen electrode. The catalysis was found to occur on glassy carbon and platinum working electrodes, but no catalysis was observed on fluoride-doped tin-oxide electrodes. Based on spectroelectrochemical results and preliminary calculations with density functional theory, one possible mechanistic route is proposed in which the oxygen evolution occurs from a peroxide intermediate formed between the oxidized flavin pseudobase and the oxidized carbon electrode. These findings offer an organic alternative to the traditional water-oxidation catalysts based on transition metals.

Mirzakulova, Ekaterina; Khatmullin, Renat; Walpita, Janitha; Corrigan, Thomas; Vargas-Barbosa, Nella M.; Vyas, Shubham; Oottikkal, Shameema; Manzer, Samuel F.; Hadad, Christopher M.; Glusac, Ksenija D.

2012-10-01

208

Global Energy and Water Cycle Experiment mate models appear to systematically under-predict  

E-print Network

5May 2009 Global Energy and Water Cycle Experiment mate models appear to systematically under characteristics of the water cycle variables that control the design and reliability of water resource systems design; and understanding the apparent under-persistence in water cycle variable time series generated

Colorado at Boulder, University of

209

Observe a raindrop traveling through various parts of the water cycle  

NSDL National Science Digital Library

The representation is an interactive resource in which students move a raindrop through different parts of the water cycle. In each part of the cycle, a drop of water represents where the water is. Clicking on the red arrows show the process as water travels through the cycle.

210

Implications of Subduction Rehydration for Earth's Deep Water Cycle  

NASA Astrophysics Data System (ADS)

The presence of liquid water is the principle difference between our Earth and other planets in the solar system. The global ocean is the obvious surface expression of this. The 'standard model' for the genesis of the oceans is that they are exhalations from Earth's deep interior continually rinsed through surface rocks by the global hydrologic cycle. The question of how much water resides within the Earth's deep interior remains unresolved and is a matter of vigorous ongoing scientific debate. We have addressed the question of water distribution between the exosphere and the mantle throughout Earth's history with simple mass balance considerations. In our model, water is outgassed from the mantle into the exosphere (atmosphere + continental crust) during pressure-release melting at mid-ocean ridges and hotspots. Plate subduction may transport water back from the surface into the deeper mantle thereby 'closing' the global geologic water cycle. In series of some 5000 model runs we have thoroughly explored the mutual effect of model parameters. All models correctly predict the formation of the present-day oceans but differ in their predicted sea-level changes through time and in the amount of water in the present-day mantle. To distinguish which model runs are the most realistic we use geochemical constraints and observed sealevel changes during the Phanerozoic. Recently Dixon et al. [2002] estimated water concentrations for some of the major mantle components and concluded that the most primitive (FOZO) are significantly wetter than the recycling associated EM or HIMU mantle components and the even drier depleted mantle source that melts to form MORB. Sealevel changes over hundreds of million of years are notoriously bad constrained. But a maximum drop in sealevel of 400-600m appears to be an upper bound. We find that only those model runs are consistent with these constraints in which deep water subduction is limited and in which the present-day mantle is relatively dry containing much less water than the exosphere. We therefore suggest a global water cycle model in which the oceans have formed by efficient outgassing of the mantle. Deep water recycling is limited and the present-day depleted mantle will contain a small volume fraction of more primitive wet mantle in addition to drier recycling related enriched components. This scenario is consistent with the observation that hotspots with a FOZO-component in their source will make wetter basalts than hotspots whose mantle sources contain a larger fraction of EM and HIMU components.

Ruepke, L. H.; Phipps Morgan, J.; Dixon, J.

2006-12-01

211

Nanostructured transition metal oxides useful for water oxidation catalysis  

DOEpatents

The present invention provides for a composition comprising a nanostructured transition metal oxide capable of oxidizing two H.sub.2O molecules to obtain four protons. In some embodiments of the invention, the composition further comprises a porous matrix wherein the nanocluster of the transition metal oxide is embedded on and/or in the porous matrix.

Frei, Heinz M; Jiao, Feng

2013-12-24

212

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

213

RELATIONSHIPS BETWEEN OXIDATION-REDUCTION POTENTIAL, OXIDANT, AND PH IN DRINKING WATER  

EPA Science Inventory

Oxidation and reduction (redox) reactions are very important in drinking water. Oxidation-reduction potential (ORP) measurements reflect the redox state of water. Redox measurements are not widely made by drinking water utilities in part because they are not well understood. The ...

214

Exploring causes of interannual variability in the seasonal cycles of tropospheric nitrous oxide  

E-print Network

Seasonal cycles in the mixing ratios of tropospheric nitrous oxide (N[subscript 2]O) are derived by detrending long-term measurements made at sites across four global surface monitoring networks. The detrended monthly data ...

Prinn, Ronald G.

215

Nanostructured manganese oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing composites in artificial photosynthesis.  

PubMed

Herein, we report on nano-sized Mn oxide/carbon nanotubes, graphene and graphene oxide as water-oxidizing compounds in artificial photosynthesis. The composites are synthesized by different and simple procedures and characterized by a number of methods. The water-oxidizing activities of these composites are also considered in the presence of cerium(IV) ammonium nitrate. Some composites are efficient Mn-based catalysts with TOF (mmol O2 per mol Mn per second) ~ 2.6. PMID:24898625

Najafpour, Mohammad Mahdi; Rahimi, Fahime; Fathollahzadeh, Maryam; Haghighi, Behzad; Ho?y?ska, Ma?gorzata; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-07-28

216

Water Cycling in the North Polar Region of Mars  

NASA Technical Reports Server (NTRS)

To date, there has been no comprehensive study to understand the partitioning of water into vapor and ice clouds, and the associated effects of dust and surface temperature in the north polar region. Ascertaining the degree to which water is transported out of the cap region versus within the cap region will give much needed insight into the overall story of water cycling on a seasonal basis. In particular, understanding the mechanism for the polar cap surface albedo changes would go along way in comprehending the sources and sinks of water in the northern polar region. We approach this problem by examining Thermal Emission Spectrometer (TES) atmospheric and surface data acquired in the northern summer season and comparing it to Viking data when possible. Because the TES instrument spans the absorption bands of water vapor, water ice, dust, and measures surface temperature, all three aerosols and surface temperature can be retrieved simultaneously. This presentation will show our latest results on the water vapor, water-ice clouds seasonal and spatial distributions, as well as surface temperatures and dust distribution which may lend insight into where the water is going.

Tamppari, L. K.; Smith, M. D.; Bass, D. S.

2003-01-01

217

Electrochemical Assessment of Amperometric Oxidability Level in Water Pollution Monitoring  

Microsoft Academic Search

Three types of electrodes were obtained and characterized in order to use for detection of some electrochemical oxidable organics conventionally considered responsabile in COD parameter evaluation: electrodes based on undoped and Co-doped lead dioxide, electrodeposited from slight acidic solutions on stainless steel support; electrodes based on copper\\/copper oxides obtained in situ in alkaline medium by potential cycling between the selected

Florica Manea; Ciprian Radovan; Ilie Vlaicu

218

Nitrogen cycling following The Great Oxidation Event, evidence from the Paleoproterozoic of Fennoscandia.  

NASA Astrophysics Data System (ADS)

The Fennoscandia Arctic Russia - Drilling Early Earth Project (FAR-DEEP) recovered core materials spanning the early Paleoproterozoic of Arctic Russia under the auspices of the International Continental Scientific Drilling Program. Here we present N and C isotopic data documenting N and C cycle dynamics during this critical interval of Earth history. Additionally, we will discuss the challenges of nitrogen isotope studies in such ancient sediments and the methods that we have utilized to test the fidelity of our nitrogen isotope data. Nitrogen isotope studies in very ancient sedimentary rocks, like those recovered by the FAR-DEEP are plagued by the concerns of diagenetic and metamorphic overprinting. Nitrogen is often present in very low concentrations and in a variety of inorganic phases that may or may not be derived from the ambient organic matter. For these reasons, bulk sediment ?15N data can be at best, ambiguous. To overcome these issues we have utilized kerogens for ?15N and ?13C analyses. The large difference between bulk and kerogen ?15N data demonstrates that inorganic N is anomalously 15N-enriched, by up to 7% and bulk ?15N values substantially overestimate the magnitude of the 15N variability in the Onega Basin (OB) sediments. Metasomatic processes during basinal magamatic activity resulted in the addition of 15N-enriched inorganic-N. Authigenic K-bearing micas are common in intervals where bulk ?15N values are 15N-enriched, suggesting that secondary mineral phases have retained 15N-enriched ammonia generated during metsomatism. The FAR-DEEP drilling team has documented an anomalously large, and rapid ?13C shift of -17% in carbonates and organic matter of the Zhaoneskaya Formation (ZF) of the OB following the extended period of 13Ccarb-enrichment know as the Lomagundi-Jatuli event. The isotopic shift in reduced carbon has also been recognized in the Franceville Formation of Gabon, termed here as "Shunga-Francevillian" anomaly, and may reflect the global oxidation of organic matter buried during the buildup of atmospheric oxygen in response to Lomagundi-Jatuli carbon burial. The dynamic response of the nitrogen cycle in the ZF is consistent with increased availability of O2 in the water column and is similar to the response documented in Archean sequences. Kerogen ?15N values are below 2%, most likely reflecting a biological N2-fixation source for nutrient-nitrogen with little influence from denitrification. ?13C values increase from -26% to -19% signaling a transient increase in the burial of organic carbon and net production of O2. Transition from a largely anoxic OB water column to one that was oxidized in its surface waters would have allowed for redox cycling of nitrogen and accompanying 15N-enrichment. Thus, the observed ?15N increase of 5% reflects an expansion in denitrification and associated reactions and oxidation of the OB water column under elevated atmospheric O2. At the end of the precipitous decrease in ?13C values ?15N values return pre-excursion values of ~+2%. This drop in ?13C and ?15N suggests a return to less oxidizing conditions in the OB following drawdown of atmospheric O2 during organic matter oxidation.

Junium, C. K.; Kump, L.; Arthur, M. A.; Melezhik, V.; Lepland, A.; Members of the FAR-DEEP Drilling Team

2011-12-01

219

Iron-oxide catalyzed silicon photoanode for water splitting  

E-print Network

This thesis presents an integrated study of high efficiency photoanodes for water splitting using silicon and iron-oxide. The fundamental limitations of silicon to water splitting applications were overcome by an ultrathin ...

Jun, Kimin

2011-01-01

220

Diurnal Cycles in Water Quality Across the Periodic Table  

NASA Astrophysics Data System (ADS)

Diurnal cycles in water quality can provide important clues to the processes that regulate aquatic chemistry, but they often are masked by longer-term, larger-amplitude variability, making their detection and quantification difficult. Here I outline several methods that can detect diurnal cycles even when they are massively obscured by statistically ill-behaved noise. I demonstrate these methods using high-frequency water quality data from the Plylimon catchment in mid-Wales (Neal et al., 2013; Kirchner and Neal, 2013). Several aspects combine to make the Plynlimon data set unique worldwide. Collected at 7-hour intervals, the Plynlimon data set is much more densely sampled than typical long-term weekly or monthly water quality data. This 7-hour sampling was also continued for two years, much longer than typical intensive sampling campaigns, and the resulting time series encompass a wide range of climatic and hydrological conditions. Furthermore, each sample was analyzed for a wide range of solutes with diverse sources in the natural environment. However, the 7-hour sampling frequency is both coarse and irregular in comparison to diurnal cycles, making their detection and quantification difficult. Nonetheless, the methods outlined here enable detection of statistically significant diurnal cycles in over 30 solutes at Plynlimon, including alkali metals (Li, Na, K, Rb, and Cs), alkaline earths (Be, Mg, Ca, Sr, and Ba), transition metals (Al, Ti, Mn, Fe, Co, Ni, Zn, Mo, Cd, and Pb), nonmetals (B, NO3, Si, As, and Se), lanthanides and actinides (La, Ce, Pr, and U), as well as total dissolved nitrogen (TDN), dissolved organic carbon (DOC), Gran alkalinity, pH, and electrical conductivity. These solutes span every row of the periodic table, and more than six orders of magnitude in concentration. Many of these diurnal cycles are subtle, representing only a few percent, at most, of the total variance in the concentration time series. Nonetheless they are diagnostically useful, because their amplitude and phase contain important clues to the mechanisms controlling these solutes in streamwater. Examples of these cycles and their likely origins will be discussed. Neal, C., B. Reynolds, J. W. Kirchner, P. Rowland, D. Norris, D. Sleep, A. Lawlor, C. Woods, S. Thacker, H. Guyatt, C. Vincent, K. Lehto, S. Grant, J. Williams, M. Neal, H. Wickham, S. Harman, and L. Armstrong. 2013. High-frequency precipitation and stream water quality time series from Plynlimon, Wales: an openly accessible data resource spanning the periodic table. Hydrological Processes 27:2531-2539. Kirchner, J. W., and C. Neal. 2013. Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection. Proceedings of the National Academy of Sciences of the United States of America 110:12213-12218.

Kirchner, J. W.

2013-12-01

221

Enhancing water cycle measurements for future hydrologic research  

USGS Publications Warehouse

The Consortium of Universities for the Advancement of Hydrologic Sciences, Inc., established the Hydrologic Measurement Facility to transform watershed-scale hydrologic research by facilitating access to advanced instrumentation and expertise that would not otherwise be available to individual investigators. We outline a committee-based process that determined which suites of instrumentation best fit the needs of the hydrological science community and a proposed mechanism for the governance and distribution of these sensors. Here, we also focus on how these proposed suites of instrumentation can be used to address key scientific challenges, including scaling water cycle science in time and space, broadening the scope of individual subdisciplines of water cycle science, and developing mechanistic linkages among these subdisciplines and spatio-temporal scales. ?? 2007 American Meteorological Society.

Loescher, H.W.; Jacobs, J.M.; Wendroth, O.; Robinson, D.A.; Poulos, G.S.; McGuire, K.; Reed, P.; Mohanty, B.P.; Shanley, J.B.; Krajewski, W.

2007-01-01

222

Water cycles in closed ecological systems: effects of atmospheric pressure  

NASA Technical Reports Server (NTRS)

In bioregenerative life support systems that use plants to generate food and oxygen, the largest mass flux between the plants and their surrounding environment will be water. This water cycle is a consequence of the continuous change of state (evaporation-condensation) from liquid to gas through the process of transpiration and the need to transfer heat (cool) and dehumidify the plant growth chamber. Evapotranspiration rates for full plant canopies can range from 1 to 10 L m-2 d-1 (1 to 10 mm m-2 d-1), with the rates depending primarily on the vapor pressure deficit (VPD) between the leaves and the air inside the plant growth chamber. VPD in turn is dependent on the air temperature, leaf temperature, and current value of relative humidity (RH). Concepts for developing closed plant growth systems, such as greenhouses for Mars, have been discussed for many years and the feasibility of such systems will depend on the overall system costs and reliability. One approach for reducing system costs would be to reduce the operating pressure within the greenhouse to reduce structural mass and gas leakage. But managing plant growth environments at low pressures (e.g., controlling humidity and heat exchange) may be difficult, and the effects of low-pressure environments on plant growth and system water cycling need further study. We present experimental evidence to show that water saturation pressures in air under isothermal conditions are only slightly affected by total pressure, but the overall water flux from evaporating surfaces can increase as pressure decreases. Mathematical models describing these observations are presented, along with discussion of the importance for considering "water cycles" in closed bioregenerative life support systems.

Rygalov, Vadim Y.; Fowler, Philip A.; Metz, Joannah M.; Wheeler, Raymond M.; Bucklin, Ray A.; Sager, J. C. (Principal Investigator)

2002-01-01

223

Life cycle water use of low-carbon transport fuels  

Microsoft Academic Search

In society’s quest to mitigate climate change it is important to consider potential trade-offs in climate solutions impacting other environmental issues. This analysis explores the life cycle water consumption of alternative low-carbon energy sources for transportation. Energy sources analyzed include both biofuels used in internal combustion engines and low-carbon electricity generation methods used in conjunction with electric vehicles. Biofuels considered

Christopher Harto; Robert Meyers; Eric Williams

2010-01-01

224

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Numerous studies suggest that local feedback of evaporation on precipitation, or recycling, is a significant source of water for precipitation. Quantitative results on the exact amount of recycling have been difficult to obtain in view of the inherent limitations of diagnostic recycling calculations. The current study describes a calculation of the amount of local and remote sources of water for precipitation, based on the implementation of passive constituent tracers of water vapor (termed water vapor tracers, WVT) in a general circulation model. In this case, the major limitation on the accuracy of the recycling estimates is the veracity of the numerically simulated hydrological cycle, though we note that this approach can also be implemented within the context of a data assimilation system. In this approach, each WVT is associated with an evaporative source region, and tracks the water until it precipitates from the atmosphere. By assuming that the regional water is well mixed with water from other sources, the physical processes that act on the WVT are determined in proportion to those that act on the model's prognostic water vapor. In this way, the local and remote sources of water for precipitation can be computed within the model simulation, and can be validated against the model's prognostic water vapor. Furthermore, estimates of precipitation recycling can be compared with bulk diagnostic approaches. As a demonstration of the method, the regional hydrologic cycles for North America and India are evaluated for six summers (June, July and August) of model simulation. More than 50% of the precipitation in the Midwestern United States came from continental regional tracers, and the local source was the largest of the regional tracers (14%). The Gulf of Mexico and Atlantic 2 regions contributed 18% of the water for Midwestern precipitation, but further analysis suggests that the greater region of the Tropical Atlantic Ocean may also contribute significantly. In general, most North American land regions showed a positive correlation between evaporation and recycling ratio (except the Southeast United States) and negative correlations of recycling ratio with precipitation and moisture transport (except the Southwestern United States). The Midwestern local source is positively correlated with local evaporation, but it is not correlated with water vapor transport. This is contrary to bulk diagnostic estimates of precipitation recycling. In India, the local source of precipitation is a small percentage of the precipitation owing to the dominance of the atmospheric transport of oceanic water. The southern Indian Ocean provides a key source of water for both the Indian continent and the Sahelian region.

Bosilovich, Michael G.; Schubert, Siegfried; Einaudi, Franco (Technical Monitor)

2001-01-01

225

Terrestrial water cycle and the impact of climate change.  

PubMed

The terrestrial water cycle and the impact of climate change are critical for agricultural and natural ecosystems. In this paper, we assess both by running a macro-scale water balance model under a baseline condition and 2 General Circulation Model (GCM)-based climate change scenarios. The results show that in 2021-2030, water demand will increase worldwide due to climate change. Water shortage is expected to worsen in western Asia, the Arabian Peninsula, northern and southern Africa, northeastern Australia, southwestern North America, and central South America. A significant increase in surface runoff is expected in southern Asia and a significant decrease is expected in northern South America. These changes will have implications for regional environment and socioeconomics. PMID:12956596

Tao, Fulu; Yokozawa, Masayuki; Hayashi, Yousay; Lin, Erda

2003-06-01

226

Climate change and the water cycle in newly irrigated areas.  

PubMed

Climate change is affecting agriculture doubly: evapotranspiration is increasing due to increments in temperature while the availability of water resources is decreasing. Furthermore, irrigated areas are expanding worldwide. In this study, the dynamics of climate change impacts on the water cycle of a newly irrigated watershed are studied through the calculation of soil water balances. The study area was a 752-ha watershed located on the left side of the Ebro river valley, in Northeast Spain. The soil water balance procedures were carried out throughout 1827 consecutive days (5 years) of hydrological and agronomical monitoring in the study area. Daily data from two agroclimatic stations were used as well. Evaluation of the impact of climate change on the water cycle considered the creation of two future climate scenarios for comparison: 2070 decade with climate change and 2070 decade without climate change. The main indicators studied were precipitation, irrigation, reference evapotranspiration, actual evapotranspiration, drainage from the watershed, and irrigation losses. The aridity index was also applied. The results represent a baseline scenario in which adaptation measures may be included and tested to reduce the impacts of climate change in the studied area and other similar areas. PMID:25626569

Abrahão, Raphael; García-Garizábal, Iker; Merchán, Daniel; Causapé, Jesús

2015-02-01

227

Selective oxidations of activated alcohols in water at room temperature.  

PubMed

Allylic and benzylic alcohols can be selectively oxidized to their corresponding aldehydes or ketones in water containing nanoreactors composed of the designer surfactant TPGS-750-M. The oxidation relies on catalytic amounts of CuBr, bpy, and TEMPO, with N-methyl-imidazole; air is the stoichiometric oxidant. PMID:25126656

Lipshutz, B H; Hageman, M; Fennewald, J C; Linstadt, R; Slack, E; Voigtritter, K

2014-10-01

228

Proton release from water oxidation by photosystem II: similar stoichiometries are stabilized in thylakoids and PSII core particles by glycerol  

Microsoft Academic Search

During the four-stepped catalytic cycle of water oxidation by photosystemII (PSII) molecular oxygen is released in only one of the four reaction steps whereas the release of four protons is distributed over all steps. In principle, the pattern of proton production could be taken as indicative of the partial reactions with bound water. In thylakoids the extent and rate of

M Haumann; M Hundelt; P Jahns; S Chroni; O Bögershausen; D Ghanotakis; W Junge

1997-01-01

229

Sensitivity of the global water cycle to the water-holding capacity of land  

Microsoft Academic Search

The sensitivity of the global water cycle to the water-holding capacity of the plant-root zone of continental soils is estimated by simulations using a mathematical model of the general circulation of the atmosphere, with prescribed ocean surface temperatures and prescribed cloud. With an increase of the globally constant storage capacity, evaporation from the continents rises and runoff falls, because a

P. C. D. Milly; K. A. Dunne

1994-01-01

230

Assessing the combined benefits of water recycling technologies by modelling the total urban water cycle  

Microsoft Academic Search

This study investigates the potential benefits of new technologies, modern appliances, and innovative techniques that help to improve the performance of the urban water cycle. Urbanisation is a major source of additional pressures (both qualitative and quantitative) on the environment. For example abstractions to cover the increased demands for water supply or alterations of the topographic and geomorphologic properties of

Evangelos Rozos; Christos Makropoulos

2011-01-01

231

Assessing the combined benefits of water recycling technologies by modelling the total urban water cycle  

Microsoft Academic Search

This study investigates the potential benefits of new technologies, modern appliances, and innovative techniques that help to improve the performance of the urban water cycle. Urbanisation is a major source of additional pressures (both qualitative and quantitative) on the environment. For example abstractions to cover the increased demands for water supply or alterations of the topographic and geomorphologic properties of

Evangelos Rozos; Christos Makropoulos

2012-01-01

232

WATER USE IN LCA Life cycle consumptive water use for oil shale development  

E-print Network

WATER USE IN LCA Life cycle consumptive water use for oil shale development and implications Heidelberg 2013 Abstract Purpose Oil shale is an unconventional petroleum source that can be produced domestically in the USA. Oil shale resources are primarily located in Utah, Wyoming, and Colorado, within

Jaramillo, Paulina

233

Water Oxidation Catalysis DOI: 10.1002/anie.201106337  

E-print Network

energy.[1] Artificial photosynthesis is a critical technology that may afford a permanent solution chemicals that may be used as fuel. Inspired by natural photosynthesis, water oxidation is considered- ditions? The initial oxidation of water takes place commonly in a proton-coupled electron transfer process

Baik, Mu-Hyun

234

The water cycle at the Phoenix landing site, Mars  

NASA Astrophysics Data System (ADS)

The water cycle is critically important to understanding Mars system science, especially interactions between water and surface minerals or possible biological systems. In this thesis, the water cycle is examined at the Mars Phoenix landing site (68.22°N, 125.70°W), using data from the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM), High-Resolution Imaging Science Experiment (HiRISE), the Phoenix Lander Surface Stereo Imager (SSI), and employing non-linear spectral mixing models. The landing site is covered for part of the year by the seasonal ice cap, a layer of CO2 and H2O ice that is deposited in mid-fall and sublimates in mid-spring. During the mid-summer, H2O ice is deposited on the surface at the Phoenix landing site. CO2 ice forms at the site during fall. The onset date of seasonal ices varies annually, perhaps due to variable levels of atmospheric dust. During fall and winter, the CO2 ice layer thickens and sinters into a slab of ice, ˜30 cm thick. After the spring equinox, the CO2 slab breaks into smaller grains as it sublimates. Long before all of the CO2 ice is gone, H2O ice dominates the near-infrared spectra of the surface. Additional H2O ice is cold-trapped onto the surface of the CO2 ice deposit during this time. Sublimation during the spring is not uniform, and depends on the thermal inertia properties of the surface, including depth of ground ice. All of the seasonal ices have sublimated by mid-spring; however, a few permanent ice deposits remain throughout the summer. These are small water ice deposits on the north-facing slopes of Heimdal Crater and adjacent plateaus, and a small patch of mobile water ices that chases shadows in a small crater near the landing site. During the late spring and early summer, the site is free of surface ice. During this time, the water cycle is dominated by vapor exchange between the subsurface water ice deposits and the atmosphere. Two types of subsurface ice were found at the Phoenix landing site: a pore water ice that appears to be in diffusive equilibrium with the atmosphere, and an almost pure water ice deposit that is apparently not in equilibrium. In addition to vapor and solid phases of the water cycle, there is strong evidence of a liquid phase. Patches of concentrated perchlorate salt are observed in trenches dug by the lander. Perchlorate is believed to form at the landing site through atmospheric interactions, which deposit the salts on the surface. The salts are then dissolved and translocated to the subsurface by thin films of liquid water. These thin films may arise due to perchlorate interactions with the atmospheric water vapor or seasonal ices. It is possible that the winter CO2 ice slab may act as a greenhouse cap, trapping enough heat for the underlying fall-deposited water ice to react with the perchlorate to form thin films of brines. Alternatively, the brines may form when summertime water vapor interacts with perchlorate on the surface, when temperatures rise above the perchlorate brine eutectic.

Cull, Selby

2010-01-01

235

Oxidation with air by ascorbate-driven quinone redox cycling.  

PubMed

Transition metal-free oxidation with air at room temperature has been achieved by simply using ascorbate (vitamin C) and catalytic amounts of menadione (vitamin K3). A combination of the mentioned vitamins transforms atmospheric oxygen into hydrogen peroxide, which is able to oxidize arylboronic acids and other chemical moieties. PMID:25805569

Silveira-Dorta, Gastón; Monzón, Diego M; Crisóstomo, Fernando P; Martín, Tomás; Martín, Víctor S; Carrillo, Romen

2015-04-25

236

Visible Light Water Splitting Using Dye-Sensitized Oxide Semiconductors  

E-print Network

to power water electrolysis. Direct photo- catalytic water splitting is a challenging problem because, in particular the four-electron oxidation of water. The building blocks of our artificial photosynthetic systems in photochemistry.1,2 Efficient photocatalytic water-splitting systems could have practical value for solar energy

237

Life-cycle testing of receiving waters with Ceriodaphnia dubia  

SciTech Connect

Seven-day tests with Ceriodaphnia dubia are commonly used to estimate toxicity of effluents or receiving waters but can sometimes yield {open_quotes}no toxicity{close_quotes} outcomes even if pollutants are present. We conducted two sets of full life-cycle tests with C. dubia to (1) see if tests with longer exposure periods would reveal evidence for toxicity that might not be evident from 7-day tests, and (2) determine the relative importance of water quality versus food as factors influencing C. dubia reproduction. In the first set of tests, C. dubia was reared in diluted mineral water (negative control), water from a stream impacted by coal fly-ash, or water from a retention basin containing sediments contaminated with mercury, other metals and polychlorinated biphenyls. The second set of tests used water from the retention basin only, but this water was either filtered or not filtered, and food was either added or not added, prior to testing. C. dubia survival and reproduction did not differ much among the three water types in the first set of tests, but these two parameters were strongly affected by the filtering and food-addition treatments in the second set of tests. Thus, C. dubia appeared to be relatively insensitive to general water-quality factors, but quite sensitive to food-related factors. Regression analyses showed that the predictability of life-time reproduction by C. dubia from the results of 7-day tests was very low (R{sup 2}< 0.35) in five of the six experiments. The increase in predictability as a function of test duration also differed among water types in the first set of tests, and among treatments in the second set of tests. Thus, 7-day tests with C. dubia may be used to quantify water-quality problems, but it may not be possible to reliably extrapolate the results of these tests to longer time scales.

Stewart, A.J.; Konetsky, B.K.

1996-12-31

238

Competitive photoelectrochemical methanol and water oxidation with hematite electrodes.  

PubMed

Photocatalytic water and methanol oxidation were studied at thin film hematite electrodes synthesized by atomic layer deposition (ALD). Systematic photoelectrochemical characterization along with O2 evolution measurements were carried out in order to better understand the mechanisms of both water and methanol oxidation at hematite electrodes. When both water and methanol are present in the solution, they are oxidized competitively with each other, allowing the detection and assignment of distinct surface states characteristic to each process. The measurement of different surface states for methanol and water oxidation, along with the absence of measurable surface states in an inert acetonitrile electrolyte, clearly shows that the detected surface states are chemically distinct reaction intermediates of water or methanol oxidation. PMID:25804788

Klahr, Benjamin; Gimenez, Sixto; Zandi, Omid; Fabregat-Santiago, Francisco; Hamann, Thomas

2015-04-15

239

The NASA Energy and Water Cycle Extreme (NEWSE) Integration Project  

NASA Technical Reports Server (NTRS)

Skillful predictions of water and energy cycle extremes (flood and drought) are elusive. To better understand the mechanisms responsible for water and energy extremes, and to make decisive progress in predicting these extremes, the collaborative NASA Energy and Water cycle Extremes (NEWSE) Integration Project, is studying these extremes in the U.S. Southern Great Plains (SGP) during 2006-2007, including their relationships with continental and global scale processes, and assessment of their predictability on multiple space and time scales. It is our hypothesis that an integrative analysis of observed extremes which reflects the current understanding of the role of SST and soil moisture variability influences on atmospheric heating and forcing of planetary waves, incorporating recently available global and regional hydro- meteorological datasets (i.e., precipitation, water vapor, clouds, etc.) in conjunction with advances in data assimilation, can lead to new insights into the factors that lead to persistent drought and flooding. We will show initial results of this project, whose goals are to provide an improved definition, attribution and prediction on sub-seasonal to interannual time scales, improved understanding of the mechanisms of decadal drought and its predictability, including the impacts of SST variability and deep soil moisture variability, and improved monitoring/attributions, with transition to applications; a bridging of the gap between hydrological forecasts and stakeholders (utilization of probabilistic forecasts, education, forecast interpretation for different sectors, assessment of uncertainties for different sectors, etc.).

House, P. R.; Lapenta, W.; Schiffer, R.

2008-01-01

240

AN AMMONIA-WATER ABSORPTION-HIAT-PUMP CYCLE Donald Kuhlenschmidt, Member ASHRAE  

E-print Network

#12;AN AMMONIA-WATER ABSORPTION-HIAT-PUMP CYCLE BY Donald Kuhlenschmidt, Member ASHRAE Richard H and Research of Arkla Industries Inc., Evansville, Indiana. #12;INTRODUCTION The ammonia-water absorption cycle and the chilled water returns to the cycle at 12.8 0 C(55F). Several things became apparent at the outset: 1

Oak Ridge National Laboratory

241

Hydrological consistency using multi-sensor remote sensing data for water and energy cycle studies  

E-print Network

Hydrological consistency using multi-sensor remote sensing data for water and energy cycle studies-sensor/multi-platform approach to water and energy cycle prediction is demonstrated in an effort to understand the variability to an improved understanding of water and energy cycles within the NAME region and providing a novel framework

Pan, Ming

242

Iron oxidation kinetics and phosphorus immobilization at the groundwater-surface water interface  

NASA Astrophysics Data System (ADS)

Eutrophication of freshwater environments following diffuse nutrient loads is a widely recognized water quality problem in catchments. Fluxes of non-point P sources to surface waters originate from surface runoff and flow from soil water and groundwater into surface water. The availability of P in surface waters is controlled strongly by biogeochemical nutrient cycling processes at the soil-water interface. The mechanisms and rates of the iron oxidation process with associated binding of phosphate during exfiltration of anaerobic Fe(II) bearing groundwater are among the key unknowns in P retention processes in surface waters in delta areas where the shallow groundwater is typically pH-neutral to slightly acid, anoxic, iron-rich. We developed an experimental field set-up to study the dynamics in Fe(II) oxidation and mechanisms of P immobilization at the groundwater-surface water interface in an agricultural experimental catchment of a small lowland river. We physically separated tube drain effluent from groundwater discharge before it entered a ditch in an agricultural field. The exfiltrating groundwater was captured in in-stream reservoirs constructed in the ditch. Through continuous discharge measurements and weekly water quality sampling of groundwater, tube drain water, exfiltrated groundwater, and ditch water, we quantified Fe(II) oxidation kinetics and P immobilization processes across the seasons. This study showed that seasonal changes in climatic conditions affect the Fe(II) oxidation process. In winter time the dissolved iron concentrations in the in-stream reservoirs reached the levels of the anaerobic groundwater. In summer time, the dissolved iron concentrations of the water in the reservoirs are low, indicating that dissolved Fe(II) is completely oxidized prior to inflow into the reservoirs. Higher discharges, lower temperatures and lower pH of the exfiltrated groundwater in winter compared to summer shifts the location of the redox transition zone, with Fe(II) oxidation taking place in the soil surrounding the ditch during summer and in the surface water during winter. The dynamics in Fe(II) oxidation did not affect the dissolved P concentrations. The dissolved P concentrations of the in-stream reservoirs water were an order of magnitude lower than observed in the groundwater and have no seasonal trend. Our data showed preferential binding of P during initial stage of the Fe(II) oxidation process, indicating the formation of Fe(III)-phosphate precipitates. The formation of Fe(III)-phosphates at the groundwater-surface water interface is an important geochemical mechanism in the transformation of dissolved phosphate to particulate phosphate and therefore a major control on the P retention in natural waters that drain anaerobic aquifers.

van der Grift, Bas; Rozemeijer, Joachim; Griffioen, Jasper; van der Velde, Ype

2014-05-01

243

Reversal of the ?-Oxidation Cycle in Saccharomyces cerevisiae for Production of Fuels and Chemicals.  

PubMed

Functionally reversing the ?-oxidation cycle represents an efficient and versatile strategy for synthesis of a wide variety of fuels and chemicals. However, due to the compartmentalization of cellular metabolisms, reversing the ?-oxidation cycle in eukaryotic systems remains elusive. Here, we report the first successful reversal of the ?-oxidation cycle in Saccharomyces cerevisiae, an important cell factory for large-scale production of fuels and chemicals. After extensive gene cloning and enzyme activity assays, a reversed ?-oxidation pathway was functionally constructed in the yeast cytosol, which led to the synthesis of n-butanol, medium-chain fatty acids (MCFAs), and medium-chain fatty acid ethyl esters (MCFAEEs). The resultant recombinant strain provides a new broadly applicable platform for synthesis of fuels and chemicals in S. cerevisiae. PMID:24959659

Lian, Jiazhang; Zhao, Huimin

2015-03-20

244

Single-Crystal Tungsten Oxide Nanosheets: Photochemical Water Oxidation in the Quantum Confinement Regime  

E-print Network

Single-Crystal Tungsten Oxide Nanosheets: Photochemical Water Oxidation in the Quantum Confinement, catalysis, WO3, tungsten oxide, nanosheet, nanocrystal, quantum confinement, solar energy conversion INTRODUCTION Tungsten trioxide crystallizes in the ReO3 structure type and is an n-type semiconductor with a 2

Osterloh, Frank

245

Solid Oxide Fuel Cell/Gas Turbine Hybrid Cycle Technology for Auxiliary Aerospace Power  

NASA Technical Reports Server (NTRS)

A notional 440 kW auxiliary power unit has been developed for 300 passenger commercial transport aircraft in 2015AD. A hybrid engine using solid-oxide fuel cell stacks and a gas turbine bottoming cycle has been considered. Steady-state performance analysis during cruise operation has been presented. Trades between performance efficiency and system mass were conducted with system specific energy as the discriminator. Fuel cell performance was examined with an area specific resistance. The ratio of fuel cell versus turbine power was explored through variable fuel utilization. Area specific resistance, fuel utilization, and mission length had interacting effects upon system specific energy. During cruise operation, the simple cycle fuel cell/gas turbine hybrid was not able to outperform current turbine-driven generators for system specific energy, despite a significant improvement in system efficiency. This was due in part to the increased mass of the hybrid engine, and the increased water flow required for on-board fuel reformation. Two planar, anode-supported cell design concepts were considered. Designs that seek to minimize the metallic interconnect layer mass were seen to have a large effect upon the system mass estimates.

Steffen, Christopher J., Jr.; Freeh, Joshua E.; Larosiliere, Louis M.

2005-01-01

246

Water Vapor Tracers as Diagnostics of the Regional Hydrologic Cycle  

NASA Technical Reports Server (NTRS)

Numerous studies suggest that local feedback of surface evaporation on precipitation, or recycling, is a significant source of water for precipitation. Quantitative results on the exact amount of recycling have been difficult to obtain in view of the inherent limitations of diagnostic recycling calculations. The current study describes a calculation of the amount of local and remote geographic sources of surface evaporation for precipitation, based on the implementation of three-dimensional constituent tracers of regional water vapor sources (termed water vapor tracers, WVT) in a general circulation model. The major limitation on the accuracy of the recycling estimates is the veracity of the numerically simulated hydrological cycle, though we note that this approach can also be implemented within the context of a data assimilation system. In the WVT approach, each tracer is associated with an evaporative source region for a prognostic three-dimensional variable that represents a partial amount of the total atmospheric water vapor. The physical processes that act on a WVT are determined in proportion to those that act on the model's prognostic water vapor. In this way, the local and remote sources of water for precipitation can be predicted within the model simulation, and can be validated against the model's prognostic water vapor. As a demonstration of the method, the regional hydrologic cycles for North America and India are evaluated for six summers (June, July and August) of model simulation. More than 50% of the precipitation in the Midwestern United States came from continental regional sources, and the local source was the largest of the regional tracers (14%). The Gulf of Mexico and Atlantic regions contributed 18% of the water for Midwestern precipitation, but further analysis suggests that the greater region of the Tropical Atlantic Ocean may also contribute significantly. In most North American continental regions, the local source of precipitation is correlated with total precipitation. There is a general positive correlation between local evaporation and local precipitation, but it can be weaker because large evaporation can occur when precipitation is inhibited. In India, the local source of precipitation is a small percentage of the precipitation owing to the dominance of the atmospheric transport of oceanic water. The southern Indian Ocean provides a key source of water for both the Indian continent and the Sahelian region.

Bosilovich, Michael G.; Schubert, Siegfried D.; Einaudi, Franco (Technical Monitor)

2001-01-01

247

New processes and players in the nitrogen cycle: the microbial ecology of anaerobic and archaeal ammonia oxidation  

Microsoft Academic Search

Microbial activities drive the global nitrogen cycle, and in the past few years, our understanding of nitrogen cycling processes and the micro-organisms that mediate them has changed dramatically. During this time, the processes of anaerobic ammonium oxidation (anammox), and ammonia oxidation within the domain Archaea, have been recognized as two new links in the global nitrogen cycle. All available evidence

Christopher A Francis; J Michael Beman; Marcel M M Kuypers

2007-01-01

248

Polyoxometalate water oxidation catalysts and methods of use thereof  

DOEpatents

Homogeneous water oxidation catalysts (WOCs) for the oxidation of water to produce hydrogen ions and oxygen, and methods of making and using thereof are described herein. In a preferred embodiment, the WOC is a polyoxometalate WOC which is hydrolytically stable, oxidatively stable, and thermally stable. The WOC oxidized waters in the presence of an oxidant. The oxidant can be generated photochemically, using light, such as sunlight, or electrochemically using a positively biased electrode. The hydrogen ions are subsequently reduced to form hydrogen gas, for example, using a hydrogen evolution catalyst (HEC). The hydrogen gas can be used as a fuel in combustion reactions and/or in hydrogen fuel cells. The catalysts described herein exhibit higher turn over numbers, faster turn over frequencies, and/or higher oxygen yields than prior art catalysts.

Hill, Craig L.; Gueletii, Yurii V.; Musaev, Djamaladdin G.; Yin, Qiushi; Botar, Bogdan

2014-09-02

249

Analysis of alternative light water reactor (LWR) fuel cycles  

SciTech Connect

Nine alternative LWR fuel cycles are analyzed in terms of the isotopic content of the fuel material, the relative amounts of primary and recycled material, the uranium and thorium requirements, the fuel cycle costs and the fraction of energy which must be generated at secured sites. The fuel materials include low-enriched uranium (LEU), plutonium-uranium (MOX), highly-enriched uranium-thorium (HEU-Th), denatured uranium-thorium (DU-Th) and plutonium-thorium (Pu-Th). The analysis is based on tracing the material requirements of a generic pressurized water reactor (PWR) for a 30-year period at constant annual energy output. During this time period all the created fissile material is recycled unless its reactivity worth is less than 0.2% uranium enrichment plant tails.

Heeb, C.M.; Aaberg, R.L.; Boegel, A.J.; Jenquin, U.P.; Kottwitz, D.A.; Lewallen, M.A.; Merrill, E.T.; Nolan, A.M.

1979-12-01

250

Efficiency, costs and benefits of AOPs for removal of pharmaceuticals from the water cycle.  

PubMed

Different advanced oxidation processes (AOP) were developed for the treatment of highly loaded wastewater streams. Optimisation of removal and improvement of efficiency were carried out on a laboratory, semiworks and pilot plant scale. The persistent cytostatic drug cyclophosphamide was selected as a reference substance regarding elimination and evaluation of the various oxidation processes because of its low degradability rate. The investigated processes are cost-efficient and suitable regarding the treatment of wastewater streams since they lead to efficient elimination of antibiotics and antineoplastics. A total reduction of toxicity was proven by means of the umuC-test. However, in order to reduce pharmaceuticals from the water cycle, it must be considered that the input of more than 80 % of the pharmaceuticals entering wastewater treatment systems results from private households. Therefore, advanced technologies should also be installed at wastewater treatment plants. PMID:20182078

Tuerk, J; Sayder, B; Boergers, A; Vitz, H; Kiffmeyer, T K; Kabasci, S

2010-01-01

251

Photochemical Water Oxidation by Crystalline Polymorphs of Manganese Oxides: Structural Requirements for Catalysis  

E-print Network

systems based on water electrolysis to H2 and O2 is limited by availability of low- cost, earthPhotochemical Water Oxidation by Crystalline Polymorphs of Manganese Oxides: Structural different crystal structures, providing a rigorous test system to explore the significance of atomic

Garfunkel, Eric

252

Diurnal cycles in water quality across the periodic table  

NASA Astrophysics Data System (ADS)

Diurnal cycles in water quality can provide important clues to the processes that regulate aquatic chemistry, but they often are masked by longer-term, larger-amplitude variability, making their detection and quantification difficult. Here I outline methods that can detect diurnal cycles even when they are massively obscured by statistically ill-behaved noise. I demonstrate these methods using high-frequency water quality data from the Plylimon catchment in mid-Wales (Neal et al., 2013; Kirchner and Neal, 2013). Several aspects combine to make the Plynlimon data set unique worldwide. Collected at 7-hour intervals, the Plynlimon data set is much more densely sampled than typical long-term weekly or monthly water quality data. This 7-hour sampling was also continued for two years, much longer than typical intensive sampling campaigns, and the resulting time series encompass a wide range of climatic and hydrological conditions. Furthermore, each sample was analyzed for a wide range of solutes with diverse sources in the natural environment. However, the 7-hour sampling frequency is both coarse and irregular in comparison to diurnal cycles, making their detection and quantification difficult. Nonetheless, the methods outlined here enable detection of statistically significant diurnal cycles in over 30 solutes at Plynlimon, including alkali metals (Li, Na, K, Rb, and Cs), alkaline earths (Be, Mg, Ca, Sr, and Ba), transition metals (Al, Ti, Mn, Fe, Co, Ni, Zn, Mo, Cd, and Pb), nonmetals (B, NO3, Si, As, and Se), lanthanides and actinides (La, Ce, Pr, and U), as well as total dissolved nitrogen (TDN), dissolved organic carbon (DOC), Gran alkalinity, pH, and electrical conductivity. These solutes span every row of the periodic table, and more than six orders of magnitude in concentration. Many of these diurnal cycles are subtle, representing only a few percent, at most, of the total variance in the concentration time series. Nonetheless they are diagnostically useful, because their amplitude and phase contain important clues to the mechanisms controlling these solutes in streamwater. The amplitudes of these cycles vary seasonally, and from wet to dry conditions; the phases are typically much more consistent over time. Under low-flow conditions, the diurnal cycle phases of different elements vary systematically with their electronic structure, as reflected in their placement in the periodic table. Potential mechanisms for this surprising pattern will be discussed. Neal, C., B. Reynolds, J. W. Kirchner, P. Rowland, D. Norris, D. Sleep, A. Lawlor, C. Woods, S. Thacker, H. Guyatt, C. Vincent, K. Lehto, S. Grant, J. Williams, M. Neal, H. Wickham, S. Harman, and L. Armstrong. 2013. High-frequency precipitation and stream water quality time series from Plynlimon, Wales: an openly accessible data resource spanning the periodic table. Hydrological Processes 27:2531-2539. Kirchner, J. W., and C. Neal. 2013. Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection. Proceedings of the National Academy of Sciences of the United States of America 110:12213-12218.

Kirchner, James

2014-05-01

253

Sensitizer-catalyst assemblies for water oxidation.  

PubMed

Two molecular assemblies with one Ru(II)-polypyridine photosensitizer covalently linked to one Ru(II)(bda)L2 catalyst (1) (bda = 2,2'-bipyridine-6,6'-dicarboxylate) and two photosensitizers covalently linked to one catalyst (2) have been prepared using a simple C-C bond as the linkage. In the presence of sodium persulfate as a sacrificial electron acceptor, both of them show high activity for catalytic water oxidation driven by visible light, with a turnover number up to 200 for 2. The linked photocatalysts show a lower initial yield for light driven oxygen evolution but a much better photostability compared to the three component system with separate sensitizer, catalyst and acceptor, leading to a much greater turnover number. Photocatalytic experiments and time-resolved spectroscopy were carried out to probe the mechanism of this catalysis. The linked catalyst in its Ru(II) state rapidly quenches the sensitizer, predominantly by energy transfer. However, a higher stability under photocatalytic condition is shown for the linked sensitizer compared to the three component system, which is attributed to kinetic stabilization by rapid photosensitizer regeneration. Strategies for employment of the sensitizer-catalyst molecules in more efficient photocatalytic systems are discussed. PMID:25700086

Wang, Lei; Mirmohades, Mohammad; Brown, Allison; Duan, Lele; Li, Fusheng; Daniel, Quentin; Lomoth, Reiner; Sun, Licheng; Hammarström, Leif

2015-03-16

254

Oxidation of methane in the water column of Lake Baikal  

NASA Astrophysics Data System (ADS)

The rate of aerobic oxidation of methane was calculated based on average profiles of the tritiumhelium age of the Baikal waters and concentrations of the dissolved methane in the water column. In the deep lake zone (>200 m), the intensity of oxidation vertically decreases and is (2-0.3) × 10-2 nl CH4l-1 days-1 in southern and central Baikal and (2.8-1.0) × 10-2 nl CH4 l-1 days-1 in northern Baikal. The effective coefficient of the oxidation rate in the lake depressions is 3.6 × 10-4, 3.3 × 10-4, and 3.7 × 10-4 days-1, respectively. At current methane concentrations in the water column, about 80 t of methane is oxidized per year. Oxidation of the dissolved methane in the water column was estimated at a possible increase of its concentration.

Granin, N. G.; Mizandrontsev, I. B.; Obzhirov, A. I.; Vereshchagina, O. F.; Gnatovskii, R. Yu.; Zhdanov, A. A.

2013-07-01

255

Arsenic cycling within the water column of a small lake receiving contaminated ground-water discharge  

SciTech Connect

The fate of arsenic discharged from contaminated ground water to a small, shallow lake at a hazardous waste site was examined to understand the role of iron (hydr)oxide precipitation-dissolution processes within the water column. Field and laboratory observations indicate that arsenic solubility was controlled, in part, by the extent of ferrous iron oxidation-precipitation and arsenic sorption occurring near the lake chemocline. Laboratory experiments were conducted using site-derived water to assess the impact of these coupled processes on the removal of dissolved arsenic from the water column. The measured concentration of organic carbon from epilimnetic and hypolimnetic water sampled from the lake was approximately 1.3 mM and 17.0 mM, respectively. Experiments conducted with these samples along with synthetic controls containing no organic carbon demonstrated that observed rates of formation and crystallinity of the precipitated iron (hydr)oxide were dependent on the concentration of organic carbon in the lake water. Increasing dissolved organic matter concentration did not significantly interfere with ferrous iron oxidation, but inhibited iron (hydr)oxide precipitation and subsequent sorption of arsenic. For experiments using water sampled from the lake hypolimnion there was a strong relationship between the fraction of precipitated iron and the fraction of sorbed arsenic. Laboratory- and field-derived iron (hydr)oxide precipitates were characterized to evaluate mineralogy and arsenic distribution. In-situ suspended solids and precipitates formed in laboratory experiments using hypolimnetic water were identified as poorly crystalline 2-line ferrihydrite. These solids were readily dissolved in the presence of dithionite indicating that elevated dissolved iron and arsenic observed in the hypolimnion resulted, in part, from in-situ reductive dissolution of settling 2-line ferrihydrite near the sediment-water interface. These observations support the contention that the levels of dissolved arsenic observed in the shallow lake can be attributed to ground-water discharge and internal recycling of arsenic within the water column. The efficiency of the process resulting in iron (hydr)oxide precipitation and arsenic sorption limits the downgradient export of arsenic derived from ground-water discharge.

Ford, Robert G.; Wilkin, Richard T.; Hernandez, Gina (EPA); (ECO)

2008-09-18

256

Research on Dualistic Water Cycle Simulation in the Reception Basin of South-to-North Water Diversion under Climate Change  

NASA Astrophysics Data System (ADS)

As social and economic activities is increasing day by day, interference to water cycle that made by human activities breaks principle and balance of original natural water cycle system, so that the existing water cycle system from dominated only by natural cycle to a new water cycle system dominated by combinational effect of natural and artificial system. The paper firstly developed the dualistic water cycle model in the reception basin of the Middle Route Project of South-to-North Water Diversion, which is developed under lots of problems such as inter-basin, large-scale, human activity, water cycle flux instability, and then parameter sensitivity analysis, parameter calibration, model validation are given. On the basis of dualistic water cycle model development, CMIP3 data is used to analysis temperature and precipitation, climate change scenario in the reception basin is scientifically given. Under the condition of climate change, the natural and artificial collateral water cycle effects by climate change are presented respectively.The results show that under climate change scenarios, runoff ratio changed greater in the water three geographical areas of Ziya River in Haihe River Basin, YongdingHe CeTian reservoir, and CeTian reservoir to Sanjiadian. Climate change impacts runoff in the reception basin as well as the quantity of water demand. From the view of result, climate change is not bringing large change to the water balance in the reception basin, and water supply could meet the 95% guarantee.

Yu, Tian

2010-05-01

257

Rapid thermal cycling of metal-supported solid oxide fuel cellmembranes  

SciTech Connect

Solid oxide fuel cell (SOFC) membranes were developed in which zirconia-based electrolyte thin films were supported by a composite metal/ceramic electrode, and were subjected to rapid thermal cycling between 200 and 800 C. The effects of this cycling on membrane performance were evaluated. The membranes, not yet optimized for performance, showed a peak power density of 350mW/cm2at 900 C in laboratory-sized SOFCs that was not affected by the thermal cycling. This resistance to cycling degradation is attributed to the close matching of thermal expansion coefficient of the cermet support electrode with that of the zirconia electrolyte.

Matus, Yuriy B.; De Jonghe, Lutgard C.; Jacobson, Craig P.; Visco, Steven J.

2004-01-02

258

A learning process of water cycle as complex system  

NASA Astrophysics Data System (ADS)

Water cycle is a very good example of a complex geosystem which has many societal impacts and drivers. A permanent and ubiquitous question is how to increase public awareness and understanding of its extreme behaviours, as well as of the related uncertainties. For instance, CEREVE is highly solicited to help the general public, particularly the youth, and the local politicians to get better acquainted with the new water culture in general and with flood risks in particular, in the nearby county Val-de-Marne. Since 2001, May is the month of the "Festival de l'Oh"(which sounds like "Festival de l'Eau", i.e. the water festival co-organized by the county council and city of Paris. "Oh » at the same time partly displays the chemical composition of water and is an exclamation for atonishment). This festival starts with the Scientific Days of Environment that involve researchers and students of the county, as well as collaborators of all around the world. This conference is open to the public who can be informed from the latest research developments, in particular with the help of some general synthesis and panel discussions. On the other hand, (young) researchers can present their own works to a large public. This conference is followed by a Professional Forum where students, heads of water public services or private operators can meet. In the framework of the water festival preparation, there are several water forums for the secondary schools. All along the year, there are regular pedagogical activities for secondary schools, in particular in the framework of Water Houses scattered across the county. We will discuss the importance to better evaluate the effective impact of these pedagogical events on the public awareness and understanding, and to make the learning process more adaptive and interactive, as well as to better address the underlying fundamental problems, e.g. the present limitations of current modelling and data processing.

Schertzer, D.; Deroubaix, J. F.; Tchiguirinskaia, I.; Tassin, B.; Thevenot, D.

2009-04-01

259

Think Scientifically: The Sun and The Water Cycle  

NSDL National Science Digital Library

Learners will read or listen to a story about two sisters, Marisol and Sofia, as they explore the Sun's role in the water cycle. Additionally, numerous extension resources are included in the accompanying educator guide, such as suggestions for no-cost language arts activities, links to further science activities, a book walk cue chart to guide classroom discussion before, during, and after the story, a graphic organizer, and alignments to the National Science Education Standards (NSES) and the Next Generation Science Standards (NGSS).

2014-02-27

260

GEWEX - The Global Energy and Water Cycle Experiment  

SciTech Connect

GEWEX, which is part of the World Climate Research Program, has as its goal an order-of-magnitude improvement in the ability to model global precipitation and evaporation and furnish an accurate assessment of the sensitivity of atmospheric radiation and clouds. Attention will also be given to the response of the hydrological cycle and water resources to climate change. GEWEX employs a single program to coordinate all aspects of climatology from model development to the deployment and operation of observational systems. GEWEX will operate over the next two decades. 5 refs.

Chahine, M.T. (JPL, Pasadena, CA (United States))

1992-01-01

261

GEWEX - The Global Energy and Water Cycle Experiment  

NASA Technical Reports Server (NTRS)

GEWEX, which is part of the World Climate Research Program, has as its goal an order-of-magnitude improvement in the ability to model global precipitation and evaporation and furnish an accurate assessment of the sensitivity of atmospheric radiation and clouds. Attention will also be given to the response of the hydrological cycle and water resources to climate change. GEWEX employs a single program to coordinate all aspects of climatology from model development to the deployment and operation of observational systems. GEWEX will operate over the next two decades.

Chahine, Moustafa T.

1992-01-01

262

A Strategy for Integrated Water Cycle Observations from Space  

NASA Astrophysics Data System (ADS)

The coupling of land surface hydrologic processes to atmospheric processes over a range of spatial and temporal scales is needed for understanding how atmosphere-land surface interactions operate and feed back onto the regional and larger scale climate system. An integral component of NASA's Global Water and Energy Cycle (GWEC) program and the World Climate Research is whether knowledge of land surface hydrologic states results in improved weather and short-term climate predictions. The inherent research strategy for NASA/GWEC and WCRP/GEWEX for investigating this is through the merging (assimilation) of remotely sensed observations of the surface hydrospheric state with process-based, terrestrial water and energy balance models. NASA assumes that remote sensing observations using current (TRMM, Terra, and Aqua) and planned (e.g. Global Precipitation Mission, HYDROS for surface soil moisture and freeze-thaw state, and possibly snow and surface water) platforms will provide sufficient estimates of surface hydrologic state variables. The extent to which this assumption can be realized remains an open question. The unmet needs facing the community in fully exploiting space-borne observations include: (i) having sufficiently accurate retrieval of physical surface states, including validation programs that can estimate retrieval error characteristics; (ii) overcoming satellite sensor programs that primarily focus on a single physical parameter; and (iii) having consistency between satellite observations and land surface models in terms of consistency in the retrieved variables as they relate to the spatial and temporal variability of the terrestrial hydrosphere. This presentation will offer a new vision for water cycle observation and modeling that has, at its core, the concept of integrated observations as opposed to isolated observations, and consistency between models and observations. By integrated observations, we mean the simultaneous retrieval of related water cycle variables from a single satellite platform with sensors for multiple frequencies, combining passive and active sensors, and perhaps lidar. By consistency between observations and models, we mean the satellite observations be processed and utilized in an integrated manner with water cycle models. By recognizing that there are fast and slow components to the hydrosphere, an observational strategy can be developed that combines sensors in either Geostationary Earth Obit (GEO) for the fast components or Low Earth (polar) Orbit (LEO) for the slow components. The talk will present the challenges that need to be addressed and a roadmap for this vision. The challenges in developing an integrated observation strategy include innovative sensor and antennae technology, including the identification and selection of frequencies and sensors to meet the needs of water cycle research. For the modeling component, the challenge is in developing computational solutions that extract the maximum information from the integrated observations. This includes both retrieval algorithms that better relate model variables to satellite measurements and land models that more effectively reflect and describe the retrieved variables.

Wood, E. F.; Houser, P. R.

2005-12-01

263

The Martian Water Cycle Based on 3-D Modeling  

NASA Technical Reports Server (NTRS)

Understanding the distribution of Martian water is a major goal of the Mars Surveyor program. However, until the bulk of the data from the nominal missions of TES, PMIRR, GRS, MVACS, and the DS2 probes are available, we are bound to be in a state where much of our knowledge of the seasonal behavior of water is based on theoretical modeling. We therefore summarize the results of this modeling at the present time. The most complete calculations come from a somewhat simplified treatment of the Martian climate system which is capable of simulating many decades of weather. More elaborate meteorological models are now being applied to study of the problem. The results show a high degree of consistency with observations of aspects of the Martian water cycle made by Viking MAWD, a large number of ground-based measurements of atmospheric column water vapor, studies of Martian frosts, and the widespread occurrence of water ice clouds. Additional information is contained in the original extended abstract.

Houben, H.; Haberle, R. M.; Joshi, M. M.

1999-01-01

264

Effect of oestrous cycle on the oxidative burst activity of blood polymorphonuclear leucocytes in cows.  

PubMed

Blood polymorphonuclear leucocyte (PMN) oxidative burst activity, plasma cortisol levels, and the total and differential white blood cells counts (WBC) of six cycled dairy cows were evaluated for a period of 24 days, three times a week; on Mondays, Wednesdays and Fridays. The PMN oxidative burst was indirectly evaluated by flow cytometry, measuring the intracellular oxidation of 2',7'-dichlorofluorescein diacetate to 2',7' dichlorofluorescein (DCF) by H2O2-production. Results are presented as the mean fluorescence intensity (MFI) of DCF. Cow's oestrous cycle was evaluated by following the plasma progesterone levels using a radioimmunoassay method. Levels of cortisol in the plasma were measured using a fluorimetric method. The oxidative burst activity of PMN, represented a maximum value (MFI=117.6+/-7.4) during the oestrous period. A fall was then observed, in which a steady state was observed during the lutheinic phase of the oestrous cycle, reaching the minimum value [MFI=73.2+/-11.2 (poxidative burst activity was observed. Our results demonstrated that the oestrous cycle might influence directly, or indirectly, the immune system of cows, by altering the oxidative burst of PMN. PMID:19000223

Chaveiro, A; Moreira da Silva, F

2009-12-01

265

The use of ozone and associated oxidation processes in drinking water treatment  

Microsoft Academic Search

This paper summarizes the main applications of ozonation and associated oxidation processes in the treatment of natural waters (surface and ground waters) for drinking water production. In fact, oxidants may be added at several points throughout the treatment: pre-oxidation, intermediate oxidation or final disinfection. So, the numerous effects of chemical oxidation are discussed along the water treatment: removal of inorganic

V Camel; A Bermond

1998-01-01

266

Carbon cycle. Sunlight controls water column processing of carbon in arctic fresh waters.  

PubMed

Carbon in thawing permafrost soils may have global impacts on climate change; however, the factors that control its processing and fate are poorly understood. The dominant fate of dissolved organic carbon (DOC) released from soils to inland waters is either complete oxidation to CO2 or partial oxidation and river export to oceans. Although both processes are most often attributed to bacterial respiration, we found that photochemical oxidation exceeds rates of respiration and accounts for 70 to 95% of total DOC processed in the water column of arctic lakes and rivers. At the basin scale, photochemical processing of DOC is about one-third of the total CO2 released from surface waters and is thus an important component of the arctic carbon budget. PMID:25146289

Cory, Rose M; Ward, Collin P; Crump, Byron C; Kling, George W

2014-08-22

267

Photosynthetic water oxidation: insights from manganese model chemistry.  

PubMed

Catalysts for light-driven water oxidation are a critical component for development of solar fuels technology. The multielectron redox chemistry required for this process has been successfully deployed on a global scale in natural photosynthesis by green plants and cyanobacteria using photosystem II (PSII). PSII employs a conserved, cuboidal Mn4CaOX cluster called the O2-evolving complex (OEC) that offers inspiration for artificial O2-evolution catalysts. In this Account, we describe our work on manganese model chemistry relevant to PSII, particularly the functional model [Mn(III/IV)2(terpy)2(?-O)2(OH2)2](NO3)3 complex (terpy = 2,2';6',2?-terpyridine), a mixed-valent di-?-oxo Mn dimer with two terminal aqua ligands. In the presence of oxo-donor oxidants such as HSO5(-), this complex evolves O2 by two pathways, one of which incorporates solvent water in an O-O bond-forming reaction. Deactivation pathways of this catalyst include comproportionation to form an inactive Mn(IV)Mn(IV) dimer and also degradation to MnO2, a consequence of ligand loss when the oxidation state of the complex is reduced to labile Mn(II) upon release of O2. The catalyst's versatility has been shown by its continued catalytic activity after direct binding to the semiconductor titanium dioxide. In addition, after binding to the surface of TiO2 via a chromophoric linker, the catalyst can be oxidized by a photoinduced electron-transfer mechanism, mimicking the natural PSII process. Model oxomanganese complexes have also aided in interpreting biophysical and computational studies on PSII. In particular, the ?-oxo exchange rates of the Mn-terpy dimer have been instrumental in establishing that the time scale for ?-oxo exchange of high-valent oxomanganese complexes with terminal water ligands is slower than O2 evolution in the natural photosynthetic system. Furthermore, computational studies on the Mn-terpy dimer and the OEC point to similar Mn(IV)-oxyl intermediates in the O-O bond-forming mechanism. Comparison between the OEC and the Mn-terpy dimer indicates that challenges remain in the development of synthetic Mn water-oxidation catalysts. These include redox leveling to couple multielectron reactions with one-electron steps, avoiding labile Mn(II) species during the catalytic cycle, and protecting the catalyst active site from undesired side reactions. As the first example of a functional manganese O2-evolution catalyst, the Mn-terpy dimer exemplifies the interrelatedness of biomimetic chemistry with biophysical studies. The design of functional model complexes enriches the study of the natural photosynthetic system, while biology continues to provide inspiration for artificial photosynthetic technologies to meet global energy demand. PMID:25730258

Young, Karin J; Brennan, Bradley J; Tagore, Ranitendranath; Brudvig, Gary W

2015-03-17

268

Niche differentiation among sulfur-oxidizing bacterial populations in cave waters  

Microsoft Academic Search

The sulfidic Frasassi cave system affords a unique opportunity to investigate niche relationships among sulfur-oxidizing bacteria, including epsilonproteobacterial clades with no cultivated representatives. Oxygen and sulfide concentrations in the cave waters range over more than two orders of magnitude as a result of seasonally and spatially variable dilution of the sulfidic groundwater. A full-cycle rRNA approach was used to quantify

Jennifer L Macalady; Sharmishtha Dattagupta; Irene Schaperdoth; Daniel S Jones; Greg K Druschel; Danielle Eastman

2008-01-01

269

Impact of ocean acidification on benthic and water column ammonia oxidation  

Microsoft Academic Search

Ammonia oxidation is a key microbial process within the marine N-cycle. Sediment and water column samples from two contrasting sites in the English Channel (mud and sand) were incubated (up to 14 weeks) in CO2-acidified seawater ranging from pH 8.0 to pH 6.1. Additional observations were made off the island of Ischia (Mediterranean Sea), a natural analogue site, where long-term

Vassilis Kitidis; Bonnie Laverock; Louise C. McNeill; Amanda Beesley; Denise Cummings; Karen Tait; Mark A. Osborn; Stephen Widdicombe

2011-01-01

270

AcidBase Mechanism for Ruthenium-Based Water Oxidation Catalysts  

Microsoft Academic Search

We present a detailed theoretical study of the pathway for water oxidation in synthetic ruthenium-based catalysts. As a first step, we consider a recently discovered single center catalyst, where experimental observations suggest a purely single-center mechanism. We find low activation energies (<5 kcal\\/mol) for each rearrangement in the catalytic cycle. In the crucial step of O-O bond formation, a solvent

L. P. Wang; Q. Wu; T. Van Voorhis

2010-01-01

271

The cycling and oxidation pathways of organic carbon in a shallow estuary along the Texas Gulf Coast  

NASA Astrophysics Data System (ADS)

The cycling and oxidation pathways of organic carbon were investigated at a single shallow water estuarine site in Trinity Bay, Texas, the uppermost lobe of Galveston Bay, during November 2000. Radio-isotopes were used to estimate sediment mixing and accumulation rates, and benthic chamber and pore water measurements were used to determine sediment-water exchange fluxes of oxygen, nutrients and metals, and infer carbon oxidation rates. Using 7Be and 234Th XS, the sediment-mixing coefficient ( Db) was 4.3 ± 1.8 cm 2 y -1, a value that lies at the lower limit for marine environments, indicating that mixing was not important in these sediments at this time. Sediment accumulation rates ( Sa), estimated using 137Cs and 210Pb XS, were 0.16 ± 0.02 g cm -2 y -1. The supply rate of organic carbon to the sediment-water interface was 30 ± 3.9 mmol C m -2 d -1, of which ˜10% or 2.9 ± 0.44 mmol C m -2 d -1was lost from the system through burial below the 1-cm thick surface mixed layer. Measured fluxes of O 2 were 26 ± 3.8 mmol m -2 d -1 and equated to a carbon oxidation rate of 20 ± 3.3 mmol C m -2 d -1, which is an upper limit due to the potential for oxidation of additional reduced species. Using organic carbon gradients in the surface mixed layer, carbon oxidation was estimated at 2.6 ± 1.1 mmol C m -2 d -1. Independent estimates made using pore water concentration gradients of ammonium and C:N stoichiometry, equaled 2.8 ± 0.46 mmol C m -2 d -1. The flux of DOC out of the sediments (DOC efflux) was 5.6 ± 1.3 mmol C m -2 d -1. In general, while mass balance was achieved indicating the sediments were at steady state during this time, changes in environmental conditions within the bay and the surrounding area, mean this conclusion might not always hold. These results show that the majority of carbon oxidation occurred at the sediment-water interface, via O 2 reduction. This likely results from the high frequency of sediment resuspension events combined with the shallow sediment mixing zone, leaving anaerobic oxidants responsible for only ˜10-15% of the carbon oxidized in these sediments.

Warnken, Kent W.; Santschi, Peter H.; Roberts, Kimberly A.; Gill, Gary A.

2008-01-01

272

Community of Practice Applications from WaterNet: The NASA Water Cycle Solutions Network  

NASA Astrophysics Data System (ADS)

WaterNet is a new international network of researchers, stakeholders, and end-users of remote sensing tools that will benefit the water resources management community. It addresses a means for enhancing the social and economic developments of nations by increased use of practical research products from the terrestrial water cycle for making informed decisions. This paper provides a summary of the Water Cycle Community of Practice (CoP) plans and examples of Land Surface Model (LSM) applications for extreme events - floods, droughts, and heavy snowstorms in Europe. It discusses the concept of NASA's solutions networks focusing on the WaterNet. It invites EGU teams to join our WaterNet network. The NASA Water cycle Solutions Network's goal is to improve and optimize the sustained ability of water cycle researchers, stakeholders, organizations and networks to interact, identify, harness, and extend NASA research results to augment decision support tools and meet national needs. Our team is developing WaterNet by engaging relevant NASA water cycle research and community-of-practice organizations, to develop what we term an "actionable database" that can be used to communicate and connect NASA Water cycle research Results (NWRs) towards the improvement of water-related Decision Support Tools (DSTs). Recognizing that the European Commission and European Space Agency have also developed many related research products (EWRs), we seek to learn about these and network with the EU teams to include their information in the WaterNet actionable data base. Recognizing the many existing highly valuable water-related science and application networks in the US and EU, we focus the balance of our efforts on enabling their interoperability - facilitating access and communications among decision-makers and scientists. We present results of our initial focus on identification, collection, and analysis of the two end points, these being the NWRs and EWRs and water related DSTs. We discuss strategies to connect these two end points via innovative communication strategies, improved user access to NASA resources, improved water cycle research community appreciation for user DST requirements, improved policymaker, management and stakeholder knowledge of NASA and EU research and application products, and improved identification of pathways for progress. Extreme event analysis and prediction is important to water managers, emergency managers-civil defense and local law enforcement, and the public. The paper presents examples from the extreme flash flood event of 18 September 2007 which cost over 200 M Euro in damages to roads, homes, and other infrastructure in the mountains west of Ljubljana. Results from NASA's Global Land Data Assimilation System - Land Surface Model show the precipitation, runoff, and soil moisture simulated in this extreme local flood event highlighting the limitations of coarse grid ¼ degree grid and 1 km grid spacing models. Drought simulations over Southeastern Europe also provide examples of model capabilities for drought management decision-making focusing on soil moisture, soil temperature, and precipitation simulations from GLDAS. Extreme snowfall events also pose a serious problem for emergency managers, ski industry and transportation managers. An example of GLDAS simulations of a heavy snow event in the Alps shows the capabilities of GLDAS, and contrasts results from the SLF snow and avalanche research. We seek to build on existing partnerships with EU scientific teams that represent a cross-section of individual and networked NWRs, EWRs and DSTs from government, private, and academic domains, that will enable us to quickly establish an operational solutions network, entrain more partner nodes and networks, and move WaterNet toward self-sustainability in the US and EU. EU projects like AWARE, and the flood and drought forecasting research efforts (DMCSEE) and GMES projects are potential projects that may directly benefit from this WaterNet networking. Specific goals and objectives, methods of communication,

Matthews, D.; Brilly, M.; Gregoric, G.; Polajnar, J.; Houser, P.; Rodell, M.; Lehning, M.

2009-04-01

273

Ocean Salinities Reveal AN Intensified Global Water Cycle  

NASA Astrophysics Data System (ADS)

Using new observed estimates of ocean surface salinity changes from 1950-2000, a comparison to results from the Coupled Model Intercomparison Project 3 (CMIP3) is made, with an aim to diagnose explicit rates of water cycle change expressed by this model suite. Examining 20C3M simulations (which most closely resemble the observed 20th century climate system), explicitly dealing with model drift, and using a technique to extract the broad-scale, zonal change patterns, a strong relationship is found between changes in the global surface water flux (evaporation minus precipitation; E-P) over the oceans (where 75-90% of global surface water exchange occurs) and changes to surface salinity. New observed surface salinity estimates suggest a surface salinity spatial pattern intensification of 16±7% K-1 has occurred since 1950, a marker of change to the oceanic water cycle. Using the CMIP3 modelled relationship between E-P and ocean salinity change, which suggests salinity responds at twice the rate of E-P to warming, allows a new estimate of observed E-P changes to be ascertained, yielding 4% (8±5% K-1) for 1950-2000, closely following Clausius-Clapeyron. The model ensemble mean, a frequently-used metric to express future projected changes, greatly underestimates the observed rate of ocean salinity change. Global average rainfall is confirmed to weakly change with surface warming (2-4% K-1), agreeing with past results, however the modelled pattern amplification of both E-P and ocean salinity fields indicate larger responses.The rate of observed 20th century salinity change is also underestimated in future projections under the IPCC SRES scenarios for 2050-2099, which express similar rates (% K-1) to their corresponding 20C3M simulations. This suggests CMIP3 provides conservative estimates of observed 20th century change - their rate of change around half that of new observational estimates.

Durack, P. J.; Wijffels, S. A.; Matear, R. J.

2011-12-01

274

A molecular catalyst for water oxidation that binds to metal oxide surfaces.  

PubMed

Molecular catalysts are known for their high activity and tunability, but their solubility and limited stability often restrict their use in practical applications. Here we describe how a molecular iridium catalyst for water oxidation directly and robustly binds to oxide surfaces without the need for any external stimulus or additional linking groups. On conductive electrode surfaces, this heterogenized molecular catalyst oxidizes water with low overpotential, high turnover frequency and minimal degradation. Spectroscopic and electrochemical studies show that it does not decompose into iridium oxide, thus preserving its molecular identity, and that it is capable of sustaining high activity towards water oxidation with stability comparable to state-of-the-art bulk metal oxide catalysts. PMID:25757425

Sheehan, Stafford W; Thomsen, Julianne M; Hintermair, Ulrich; Crabtree, Robert H; Brudvig, Gary W; Schmuttenmaer, Charles A

2015-01-01

275

A molecular catalyst for water oxidation that binds to metal oxide surfaces  

PubMed Central

Molecular catalysts are known for their high activity and tunability, but their solubility and limited stability often restrict their use in practical applications. Here we describe how a molecular iridium catalyst for water oxidation directly and robustly binds to oxide surfaces without the need for any external stimulus or additional linking groups. On conductive electrode surfaces, this heterogenized molecular catalyst oxidizes water with low overpotential, high turnover frequency and minimal degradation. Spectroscopic and electrochemical studies show that it does not decompose into iridium oxide, thus preserving its molecular identity, and that it is capable of sustaining high activity towards water oxidation with stability comparable to state-of-the-art bulk metal oxide catalysts. PMID:25757425

Sheehan, Stafford W.; Thomsen, Julianne M.; Hintermair, Ulrich; Crabtree, Robert H.; Brudvig, Gary W.; Schmuttenmaer, Charles A.

2015-01-01

276

Life cycle assessment for sustainable metropolitan water systems planning.  

PubMed

Life Cycle Assessment (LCA) is useful as an information tool for the examination of alternative future scenarios for strategic planning. Developing a life cycle assessment for a large water and wastewater system involves making methodological decisions about the level of detail which is retained through different stages of the process. In this article we discuss a methodology tailored to strategic planning needs which retains a high degree of model segmentation in order to enhance modeling of a large, complex system. This is illustrated by a case study of Sydney Water, which is Australia's largest water service provider. A prospective LCA was carried out to examine the potential environmental impacts of Sydney Water's total operations in the year 2021. To our knowledge this is the first study to create an LCA model of an integrated water and wastewater system with this degree of complexity. A "base case" system model was constructed to represent current operating assets as augmented and upgraded to 2021. The base case results provided a basis for the comparison of alternative future scenarios and for conclusions to be drawn regarding potential environmental improvements. The scenarios can be roughly classified in two categories: (1) options which improve the environmental performance across all impact categories and (2) options which improve one indicator and worsen others. Overall environmental improvements are achieved in all categories by the scenarios examining increased demand management, energy efficiency, energy generation, and additional energy recovery from biosolids. The scenarios which examined desalination of seawater and the upgrades of major coastal sewage treatment plants to secondary and tertiary treatment produced an improvement in one environmental indicator but deteriorations in all the other impact categories, indicating the environmental tradeoffs within the system. The desalination scenario produced a significant increase in greenhouse gas emissions due to coal-fired electricity generation for a small increase in water supply. Assessment of a greenfield scenario incorporating water demand management, on-site treatment, local irrigation, and centralized biosolids treatment indicates significant environmental improvements are possible relative to the assessment of a conventional system of corresponding scale. PMID:15296294

Lundie, Sven; Peters, Gregory M; Beavis, Paul C

2004-07-01

277

Ubiquity and diversity of ammonia-oxidizing archaea in water columns and sediments of the ocean  

PubMed Central

Nitrification, the microbial oxidation of ammonia to nitrite and nitrate, occurs in a wide variety of environments and plays a central role in the global nitrogen cycle. Catalyzed by the enzyme ammonia monooxygenase, the ability to oxidize ammonia was previously thought to be restricted to a few groups within the ?- and ?-Proteobacteria. However, recent metagenomic studies have revealed the existence of unique ammonia monooxygenase ?-subunit (amoA) genes derived from uncultivated, nonextremophilic Crenarchaeota. Here, we report molecular evidence for the widespread presence of ammonia-oxidizing archaea (AOA) in marine water columns and sediments. Using PCR primers designed to specifically target archaeal amoA, we find AOA to be pervasive in areas of the ocean that are critical for the global nitrogen cycle, including the base of the euphotic zone, suboxic water columns, and estuarine and coastal sediments. Diverse and distinct AOA communities are associated with each of these habitats, with little overlap between water columns and sediments. Within marine sediments, most AOA sequences are unique to individual sampling locations, whereas a small number of sequences are evidently cosmopolitan in distribution. Considering the abundance of nonextremophilic archaea in the ocean, our results suggest that AOA may play a significant, but previously unrecognized, role in the global nitrogen cycle. PMID:16186488

Francis, Christopher A.; Roberts, Kathryn J.; Beman, J. Michael; Santoro, Alyson E.; Oakley, Brian B.

2005-01-01

278

Unification of catalytic water oxidation and oxygen reduction reactions: amorphous beat crystalline cobalt iron oxides.  

PubMed

Catalytic water splitting to hydrogen and oxygen is considered as one of the convenient routes for the sustainable energy conversion. Bifunctional catalysts for the electrocatalytic oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) are pivotal for the energy conversion and storage, and alternatively, the photochemical water oxidation in biomimetic fashion is also considered as the most useful way to convert solar energy into chemical energy. Here we present a facile solvothermal route to control the synthesis of amorphous and crystalline cobalt iron oxides by controlling the crystallinity of the materials with changing solvent and reaction time and further utilize these materials as multifunctional catalysts for the unification of photochemical and electrochemical water oxidation as well as for the oxygen reduction reaction. Notably, the amorphous cobalt iron oxide produces superior catalytic activity over the crystalline one under photochemical and electrochemical water oxidation and oxygen reduction conditions. PMID:25469760

Indra, Arindam; Menezes, Prashanth W; Sahraie, Nastaran Ranjbar; Bergmann, Arno; Das, Chittaranjan; Tallarida, Massimo; Schmeißer, Dieter; Strasser, Peter; Driess, Matthias

2014-12-17

279

The water cycles of water-soluble organic salts of atmospheric importance  

Microsoft Academic Search

In this study, the water cycles of nine water-soluble organic salts of atmospheric interest were studied using an electrodynamic balance (EDB) at 25°C. Sodium formate, sodium acetate, sodium succinate, sodium pyruvate and sodium methanesulfonate (Na-MSA) particles crystallize as the relative humidity (RH) decreases and they deliquesce as the RH increases. Sodium oxalate and ammonium oxalate form supersaturated particles at low

Changgeng Peng; Chak K Chan

2001-01-01

280

Water activation by small free ruthenium oxide clusters.  

PubMed

The reactions of ruthenium clusters, Rux(+) (x = 2-5), and ruthenium oxide clusters, RuxOy(+) (x = 2-5, y = 1-2), with water molecules have been investigated by gas phase ion trap mass spectrometry and first principle density functional calculations. The joint experimental and theoretical study reveals that the reactions of the ruthenium oxide clusters with water are considerably more efficient. This is assigned theoretically to the stronger binding of the water molecules to RuxOy(+) and, more importantly, to water activation leading to an efficient hydrogen transfer reaction from the water molecules to the oxygen atoms of the ruthenium oxide clusters. The theoretically predicted hydrogen shift reaction has been confirmed experimentally through (16)O/(18)O isotope exchange experiments. Calculated energy profiles for the reactions of selected oxide clusters with water illustrate that the oxygen isotope exchange relies on the facile transfer of hydrogen atoms via [1,3] shift reactions between the oxygen atoms of the complexes due to the relatively low barriers involved. These findings might open perspectives for the future realization of water oxidation driven by ruthenium oxide clusters. PMID:25146165

Lang, Sandra M; Bernhardt, Thorsten M; Krsti?, Marjan; Bona?i?-Koutecký, Vlasta

2014-12-28

281

Anticipated SWOT Observations of Human Impacts on the Water Cycle  

NASA Astrophysics Data System (ADS)

The impoundment of water behind dams alters the timing and magnitude of the discharge of rivers to the ocean, and hence sea level, as well as evaporation from the global land areas, and, through irrigation, the storage of water on land in the soil column. The impact of these effects on the global hydrologic cycle globally is difficult to estimate given currently available (and shared) observations of temporally varying reservoir storage. The upcoming joint U.S.-France Surface Water and Ocean Topography (SWOT) mission* will measure terrestrial surface water storage dynamics with unprecedented global coverage for managed reservoirs, as well as natural lakes and rivers. Previous studies have investigated SWOT's potential ability to measure storage change for some lakes; however, because reservoirs are typically located in flooded river valleys, they tend to be more elongate than the high latitude lakes that have been studied, and have more complex shorelines (and hence a longer land-water boundary). Furthermore, for reservoirs in mountainous regions, SWOT observations will be prone to topographic layover effects. Finally, the temporal variability of water levels in reservoirs is determined by management goals (i.e., hydropower, flood control, irrigation, supply, recreation), rather than climate, as in the case of natural lakes. We report an investigation of the potential accuracy of SWOT observations of storage change over selected managed reservoirs in the United States. First, we developed a time series of water height maps over each reservoir by combining available bathymetry data with observations of reservoir storage. We then simulated realistic SWOT observations of water level over these water bodies, given the planned SWOT orbital parameters, anticipated noise, and topographic layover errors. We also simulated a realistic tropospheric delay, modeled from daily MERRA reanalysis data. From these synthetic observations, we estimate the number of overpasses needed to construct accurate area-elevation-volume curves. We discuss the accuracy of absolute volume estimated from an extrapolation of the smoothed elevation-volume relationship, as well as the accuracy of the directly observed storage change. SWOT performs better in terms of storage change accuracy over large reservoirs with regular boundaries and relatively flat topography. In addition, we assess the ability of SWOT's planned sampling schedule to reconstruct the variability in storage change for U.S. reservoirs as a function of their storage capacity. Estimates of absolute storage are most accurate for reservoirs that experience the most water level variation during the anticipated SWOT sampling period. *The SWOT mission has not been formally approved by NASA. The decision to proceed with the mission will not occur until the completion of the National Environmental Policy Act (NEPA) process. Material in this paper related to SWOT is for information purposes only.

Clark, E.; Andreadis, K.; Moller, D.; Lettenmaier, D. P.

2012-12-01

282

A Review of RedOx Cycling of Solid Oxide Fuel Cells Anode  

PubMed Central

Solid oxide fuel cells are able to convert fuels, including hydrocarbons, to electricity with an unbeatable efficiency even for small systems. One of the main limitations for long-term utilization is the reduction-oxidation cycling (RedOx cycles) of the nickel-based anodes. This paper will review the effects and parameters influencing RedOx cycles of the Ni-ceramic anode. Second, solutions for RedOx instability are reviewed in the patent and open scientific literature. The solutions are described from the point of view of the system, stack design, cell design, new materials and microstructure optimization. Finally, a brief synthesis on RedOx cycling of Ni-based anode supports for standard and optimized microstructures is depicted. PMID:24958298

Faes, Antonin; Hessler-Wyser, Aïcha; Zryd, Amédée; Van Herle, Jan

2012-01-01

283

Failure and Life Cycle Evaluation of Watering Valves  

PubMed Central

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves’ internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a ‘drying out’ period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure. PMID:22330720

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-01-01

284

Failure and life cycle evaluation of watering valves.  

PubMed

Automated watering systems provide a reliable source of ad libitum water to animal cages. Our facility uses an automated water delivery system to support approximately 95% of the housed population (approximately 14,000 mouse cages). Drinking valve failure rates from 2002 through 2006 never exceeded the manufacturer standard of 0.1% total failure, based on monthly cage census and the number of floods. In 2007, we noted an increase in both flooding and cases of clinical dehydration in our mouse population. Using manufacturer's specifications for a water flow rate of 25 to 50 mL/min, we initiated a wide-scale screening of all valves used. During a 4-mo period, approximately 17,000 valves were assessed, of which 2200 failed according to scoring criteria (12.9% overall; 7.2% low flow; 1.6% no flow; 4.1% leaky). Factors leading to valve failures included residual metal shavings, silicone flash, introduced debris or bedding, and (most common) distortion of the autoclave-rated internal diaphragm and O-ring. Further evaluation revealed that despite normal autoclave conditions of heat, pressure, and steam, an extreme negative vacuum pull caused the valves' internal silicone components (diaphragm and O-ring) to become distorted and water-permeable. Normal flow rate often returned after a 'drying out' period, but components then reabsorbed water while on the animal rack or during subsequent autoclave cycles to revert to a variable flow condition. On the basis of our findings, we recalibrated autoclaves and initiated a preventative maintenance program to mitigate the risk of future valve failure. PMID:22330720

Gonzalez, David M; Graciano, Sandy J; Karlstad, John; Leblanc, Mathias; Clark, Tom; Holmes, Scott; Reuter, Jon D

2011-09-01

285

Theoretical investigation of solar energy conversion and water oxidation catalysis  

E-print Network

Solar energy conversion and water oxidation catalysis are two great scientific and engineering challenges that will play pivotal roles in a future sustainable energy economy. In this work, I apply electronic structure ...

Wang, Lee-Ping

2011-01-01

286

Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape  

E-print Network

Short note Water, carbon and nitrogen cycling in a rendzina soil cropped with winter oilseed rape.) Internet database / nitrogen cycle / rendzina / oilseed rape Résumé - Une base de données sur les cycles on the dynamic fluxes of water, carbon and nitrogen within a soil-crop system at the field-scale, conducted

Paris-Sud XI, Université de

287

Proposal and analysis of a novel ammonia–water cycle for power and refrigeration cogeneration  

Microsoft Academic Search

Cogeneration has improved sustainability as it can improve the energy utilization efficiency significantly. In this paper, a novel ammonia-water cycle is proposed for the cogeneration of power and refrigeration. In order to meet the different concentration requirements in the cycle heat addition process and the condensation process, a splitting \\/absorption unit is introduced and integrated with an ammonia–water Rankine cycle

Meng Liu; Na Zhang

2007-01-01

288

A method for determining the oxidation state of uranium in natural waters  

NASA Astrophysics Data System (ADS)

Uranium exhibits radically different geochemical properties in its two oxidation states. Hexavalent uranium is quite soluble, especially when complexed by carbonate ions in alkaline solutions. Tetravalent uranium, by contrast, is very insoluble, and it would be expected to be rapidly removed from natural waters either by precipitation of a mineral phase such as UO 2(s) or by adsorption to solid surfaces. It is important to know the oxidation state in which uranium will occur under specified conditions of Eh and pH as this relates both to processes forming economically valuable uranium deposits and to the mobility of uranium released to the environment during various stages of the nuclear fuel cycle. In this work, yield monitors in each oxidation state [ 232U(IV)], 236U(VI)] are added to water samples, and uranium oxidation states are separated by a NdF 3 coprecipitation in which only the U(IV) is carried. The precipitate is removed by filtration. Subsequently, TiCl 3 is added to reduce U(IV) and the NdF 3 coprecipitation is repeated. A similar method is widely used for separating oxidation states of plutonium. Results from a meromictic lake (Fayetteville Green Lake, Syracuse, New York, USA) and from an anoxic marine basin (Cariaco Trench, Venezuela) where total H 2S concentrations in the bottom waters reach 1 mM 1 -1 and 50 ?M 1 -1 respectively show that in both cases the dissolved uranium is present in its oxidized form.

Anderson, Robert F.

1984-06-01

289

[Comment on ``GEWEX: The Global Energy and Water Cycle Experiment''] More global water balance uncertainty  

Microsoft Academic Search

I concur strongly with Chahine's January 14, 1992, Eos article on GEWEX and support his response to Dincer's letter (Eos, June 16, 1992) emphasizing that ``our quantitative knowledge of the hydrological cycle remains surprisingly poor.'' This is despite the magnificent report on the world water balance to which Dincer refers and his allusion that the existence of a low residual

John C. Rodda

1992-01-01

290

The Global Energy and Water Cycle Experiment: Applying Planetary Science to Global and Regional Water Issues  

Microsoft Academic Search

The Global Energy and Water Cycle Experiment (GEWEX) was initiated in 1988 under the auspices of the World Climate Research Programme. The first phase of GEWEX has now come to a successful conclusion and work is progressing on the Phase II objectives and goals. During Phase I, efforts were directed at the development of data bases at global and regional

R. G. Lawford

2004-01-01

291

Electrocatalytic Synthesis of Propylene Oxide During Water Electrolysis  

Microsoft Academic Search

A new method for the synthesis of propylene oxide using nascent oxygen generated during the electrolysis of water has been proposed. Among the noble metal blacks tested, the most active and selective anode electrocatalyst was Pt black. The oxidation of propylene was initiated at an applied voltage across the cell higher than ca. 1.1 V (anode potential higher than 1.1

Kiyoshi Otsuka; Tetsuya Ushiyama; Ichiro Yamanaka; K. Ebitani

1995-01-01

292

Anodic oxidation of phenol for waste water treatment  

Microsoft Academic Search

The electrochemical oxidation of phenol for waste water treatment was studied at a platinum anode. Analysis of reaction intermediates and a carbon balance has shown that the reaction occurs by two parallel pathways; chemical oxidation with electrogenerated hydroxyl radicals and direct combustion of adsorbed phenol or\\/and its aromatic intermediates to CO2.

Ch. Comninellis; C. Pulgarin

1991-01-01

293

The Urban Water Cycle and how it Modulates the Microclimate and the Energy Cycle  

NASA Astrophysics Data System (ADS)

Urbanization is the land-use modification with the largest and most manifest impacts on hydrologic storage and fluxes. This perturbation of the water cycle also has considerable ramifications on the surface energy budget and the microclimatology in built terrain: reducing the potential for water storage and subsequent evaporation reduces the fraction of incoming radiative energy dissipated through surface evaporation, and consequently increases the sensible heating of the urban atmosphere and solid surfaces (buildings, roads, …). However, the complexity of the involved physical processes and their interactions have so far been oversimplified, leading to considerable biases in model output when compared to observations. Using novel sensing techniques that include wireless sensor networks, this study seeks to build a better understanding of the Urban Water Cycle. Our findings indicate that "impervious surfaces" in urban area are not really impervious and not always dry. The role of evaporation from gravel-covered roofs and from concrete, brick, stone and asphalt surfaces can be considerable, leading to lower sensible heating. In addition, the different thermal properties of the various urban materials lead to extreme spatial heterogeneity in surface conditions that is much higher than over natural terrain. Building on this understanding, an improved urban canopy model is developed that includes much better representation of surface heterogeneity and of hydrological and thermal storage and transport processes, including analytical solutions of the heat equation and numerical solutions of the Richards equation in the urban surface. The model development will be detailed and applications focusing on the role of evaporation in mitigating summer building cooling needs and urban heat island effects will be presented.

Bou-Zeid, E.; Wang, Z.; Ramamurthy, P.; Li, D.; Sun, T.; Smith, J. A.

2012-12-01

294

Process for treating effluent from a supercritical water oxidation reactor  

DOEpatents

A method for treating a gaseous effluent from a supercritical water oxidation reactor containing entrained solids is provided comprising the steps of expanding the gas/solids effluent from a first to a second lower pressure at a temperature at which no liquid condenses; separating the solids from the gas effluent; neutralizing the effluent to remove any acid gases; condensing the effluent; and retaining the purified effluent to the supercritical water oxidation reactor.

Barnes, Charles M. (Idaho Falls, ID); Shapiro, Carolyn (Idaho Falls, ID)

1997-01-01

295

Process for treating effluent from a supercritical water oxidation reactor  

DOEpatents

A method for treating a gaseous effluent from a supercritical water oxidation reactor containing entrained solids is provided comprising the steps of expanding the gas/solids effluent from a first to a second lower pressure at a temperature at which no liquid condenses; separating the solids from the gas effluent; neutralizing the effluent to remove any acid gases; condensing the effluent; and retaining the purified effluent to the supercritical water oxidation reactor. 6 figs.

Barnes, C.M.; Shapiro, C.

1997-11-25

296

Our Environment in Hot Water: Comparing Water Heaters, A Life Cycle Approach Comparing Tank and Tankless Water Heaters in California  

SciTech Connect

Residential water heating is a large source of energy use in California homes. This project took a life cycle approach to comparing tank and tankless water heaters in Northern and Southern California. Information about the life cycle phases was calculated using the European Union?s Methodology study for EcoDesign of Energy-using Products (MEEUP) and the National Renewable Energy Laboratory?s Life Cycle Inventory (NREL LCI) database. In a unit-to-unit comparison, it was found that tankless water heaters would lessen impacts of water heating by reducing annual energy use by 2800 MJ/year (16% compared to tank), and reducing global warming emissions by 175 kg CO2 eqv./year (18% reduction). Overall, the production and combustion of natural gas in the use phase had the largest impact. Total waste, VOCs, PAHs, particulate matter, and heavy-metals-to-air categories were also affected relatively strongly by manufacturing processes. It was estimated that tankless water heater users would have to use 10 more gallons of hot water a day (an increased usage of approximately 20%) to have the same impact as tank water heaters. The project results suggest that if a higher percentage of Californians used tankless water heaters, environmental impacts caused by water heating would be smaller.

Lu, Alison; McMahon, James; Masanet, Eric; Lutz, Jim

2008-08-13

297

Heat-sterilized silver oxide-zinc cells: Cycle life studies  

NASA Technical Reports Server (NTRS)

A JPL study was conducted to evaluate the cell design parameters that contribute to the cycle life of sealed, heat-sterilized silver oxide-zinc cells. Test cells having a rated capacity of 4.2 A-h were fabricated using zinc oxide electrodes prepared by the sintered Teflon process. Two separator variations were evaluated, one having acrylic acid and the other methacrylic acid grafted to irradiated polyethylene film. Significant results of this study include the following: (1) cycle life in excess of 300 cycles was attained; (2) a zinc oxide/silver stoichiometric ratio of 1.5 resulted in greater cycle life than a ratio of 1.1, and similar cycle life to cells having a ratio of 2; (3) cells having methacrylic acid grafted separators suffered somewhat less in capacity loss due to zinc electrode shape change than cells having acrylic acid type; (4) use of acrylic acid grafted separators was slightly superior to the methacrylic acid type in respect to silver penetration; and (5) the inclusion of a layer of potassium titanate paper adjacent to the zinc electrodes resulted in cells that achieved higher cycle life before any of the group failed than that reached by cells of any other construction.

Arms, J. T.

1973-01-01

298

NEWS Climatology Project: The State of the Water Cycle at Continental to Global Scales  

NASA Technical Reports Server (NTRS)

NASA's Energy and Water Cycle Study (NEWS) program fosters collaborative research towards improved quantification and prediction of water and energy cycle consequences of climate change. In order to measure change, it is first necessary to describe current conditions. The goal of the NEWS Water and Energy Cycle Climatology project is to develop "state of the global water cycle" and "state of the global energy cycle" assessments based on data from modern ground and space based observing systems and data integrating models. The project is a multiinstitutional collaboration with more than 20 active contributors. This presentation will describe results of the first stage of the water budget analysis, whose goal was to characterize the current state of the water cycle on mean monthly, continental scales. We examine our success in closing the water budget within the expected uncertainty range and the effects of forcing budget closure as a method for refining individual flux estimates.

Rodell, Matthew; LEcuyer, Tristan; Beaudoing, Hiroko Kato; Olson, Bill

2011-01-01

299

ARSENIC CYCLING WITHIN THE WATER COLUMN OF A SMALL LAKE RECEIVING CONTAMINATED GROUND WATER DISCHARGE  

EPA Science Inventory

The fate of arsenic discharged from contaminated ground water to a small, shallow lake at a hazardous waste site is controlled, in part, by the rate of ferrous iron oxidation-precipitation and arsenic sorption occurring near the lake chemocline. Laboratory experiments were condu...

300

Conversions of Mn oxides to nanolayered Mn oxide in electrochemical water oxidation at near neutral pH, all to a better catalyst: catalyst evolution.  

PubMed

Here, for the first time, it is reported that some Mn oxides after a few hours convert to a nanolayered Mn oxide when the compounds are used as water-oxidizing catalysts in a water electrolysis device at near neutral pH and in the presence of LiClO4. The new nanolayered Mn oxide is more active than other Mn oxides toward water oxidation. This result is very important for artificial photosynthetic systems that use Mn oxides as water-oxidizing catalysts. PMID:24149796

Najafpour, Mohammad Mahdi; Haghighi, Behzad; Sedigh, Davood Jafarian; Ghobadi, Mohadeseh Zarei

2013-12-28

301

Exploring the limits of the terrestrial fresh water cycle  

NASA Astrophysics Data System (ADS)

Precipitation is the ultimate source of life on this planet: it makes our crops grow, provides drinking water, feeds rivers and replenishes groundwater aquifers. Climate modelling studies estimate changes in precipitation due to increased greenhouse gas emissions and climate impact studies use those estimates as input to their (hydrological) models to predict future water availability and societal impact. However, humans also significantly alter the land surface by, for example, deforestation and irrigation, which is not frequently taken into account in our climate studies. Here, we present an overview of several papers in the field of moisture recycling, published by our group, that show the extent to which terrestrial evaporation influences terrestrial precipitation. It is found that 38% of the terrestrial precipitation originates from terrestrial evaporation and that 58% of all terrestrial evaporation recycles, and return again as terrestrial precipitation. Knowing this, it is clear that evaporation is not necessary a loss to the hydrological cycle. We show that in some cases even transpiration during the dry season can act as a moisture source for a distant region. To assess the vulnerability of a region to local and remote land use changes we propose the concept of the precipitationshed, which maps out a region's precipitation sources. Our results are useful in mapping out possible land use change threats, but also opportunities to safeguard our water resources in the Anthropocene.

van der Ent, Ruud; Wang-Erlandsson, Lan; Keys, Patrick; Savenije, Hubert

2014-05-01

302

KINEMATIC EVALUATION OF WET OXIDATION FOR PHENOLIC CONTAMINATED WATERS  

Microsoft Academic Search

Wet oxidations catalyzed by MnO2, Co2O3, and CuSO4.5H2O, were carried out for waters containing 1000 mg\\/L phenol and 1500 mg\\/L p-chlorophenol, respectively. CuSO4-5H2O was demonstrated to be the most effective in reducing the concentration of phenols in waters. Rate constant and activation energy of the oxidation were also obtained, the enhancement of catalysts on the oxidation rate of phenol was

CHIEHMING J. CHANG; CHING-MING KO; KENT SHIHC

1997-01-01

303

Energetic basis of catalytic activity of layered nanophase calcium manganese oxides for water oxidation  

PubMed Central

Previous measurements show that calcium manganese oxide nanoparticles are better water oxidation catalysts than binary manganese oxides (Mn3O4, Mn2O3, and MnO2). The probable reasons for such enhancement involve a combination of factors: The calcium manganese oxide materials have a layered structure with considerable thermodynamic stability and a high surface area, their low surface energy suggests relatively loose binding of H2O on the internal and external surfaces, and they possess mixed-valent manganese with internal oxidation enthalpy independent of the Mn3+/Mn4+ ratio and much smaller in magnitude than the Mn2O3-MnO2 couple. These factors enhance catalytic ability by providing easy access for solutes and water to active sites and facile electron transfer between manganese in different oxidation states. PMID:23667149

Birkner, Nancy; Nayeri, Sara; Pashaei, Babak; Najafpour, Mohammad Mahdi; Casey, William H.; Navrotsky, Alexandra

2013-01-01

304

Rare earth element partitioning between hydrous ferric oxides and acid mine water during iron oxidation  

USGS Publications Warehouse

Ferrous iron rapidly oxidizes to Fe (III) and precipitates as hydrous Fe (III) oxides in acid mine waters. This study examines the effect of Fe precipitation on the rare earth element (REE) geochemistry of acid mine waters to determine the pH range over which REEs behave conservatively and the range over which attenuation and fractionation occur. Two field studies were designed to investigate REE attenuation during Fe oxidation in acidic, alpine surface waters. To complement these field studies, a suite of six acid mine waters with a pH range from 1.6 to 6.1 were collected and allowed to oxidize in the laboratory at ambient conditions to determine the partitioning of REEs during Fe oxidation and precipitation. Results from field experiments document that even with substantial Fe oxidation, the REEs remain dissolved in acid, sulfate waters with pH below 5.1. Between pH 5.1 and 6.6 the REEs partitioned to the solid phases in the water column, and heavy REEs were preferentially removed compared to light REEs. Laboratory experiments corroborated field data with the most solid-phase partitioning occurring in the waters with the highest pH. ?? 2004 Elsevier Ltd. All rights reserved.

Verplanck, P.L.; Nordstrom, D.K.; Taylor, H.E.; Kimball, B.A.

2004-01-01

305

TYPES OF FLOODING IN AUSTRALIA Floods are part of the natural water cycle or a "Hydrologic Cycle". In this natural cycle, the energy of the sun causes  

E-print Network

TYPES OF FLOODING IN AUSTRALIA Floods are part of the natural water cycle or a "Hydrologic Cycle into the soil to later form groundwater flow. Floods happen when the capacity of the rivers is not enough quite regularly is called a floodplain. Floods are caused by prolonged or heavy rainfall. Cyclones bring

Greenslade, Diana

306

Nitrogen cycling in the offshore waters of the Black Sea  

NASA Astrophysics Data System (ADS)

The purpose of this study was to measure directly the rates of several of the processes responsible for the production and utilization of nitrogenous nutrients, and to use these rates and other data to generate an annual nitrogen budget for the Black Sea. Water column samples and experimentation with 15N labeled nutrients in the offshore waters of the Black Sea reveal strong seasonal cycles in the utilization of different forms of N, the regeneration of NH 4+ and the production of NO 2- in and below the surface mixed layer. There was no opportunity to sample during winter, but historical data and contemporary satellite ocean color data for the study period allow us to make extrapolations to a full annual cycle for the Black Sea N budget. The processes supplying N to, and the microbial processes within, the Cold Intermediate Layer (CIL), which lies below the surface mixed layer, figure prominently in determining the sources of N available for primary production. The uptake of NO 3- by phytoplankton in this system was less sensitive to NH 4+ concentration than has been observed in many oceanic waters. The seasonal shift in nutrient uptake kinetics was consistent with seasonality of nutrient availability. Rates of in situ NO 2- production (and inferred nitrification) for the offshore waters was 1.6 × 10 11 mol y -1, three times the published estimates for NO 3- supplied from the NW Shelf (NWS) region, which originates from riverine discharges. Measured rates of nitrification in the CIL are about 60% of phytoplankton NO 3- + NO 2- uptake (2.8 × 10 11 mol y -1). Remineralization is about 25% of the NH 4+ phytoplankton utilization rate (3.8 × 10 11 mol y -1). Within the CIL NH 4+ is utilized in NO 2- production (and implied nitrification) at a rate that is similar to the rate of NH 4+ remineralization from organic matter. By preserving the rates that are determined with the most confidence, and making adjustments to the rates least confidently determined, nitrification (+60%, which is within the range of published values) and ammonium remineralization (+13%), the Black Sea N budget can be brought into balance. A balanced annual budget for N cycling in the offshore waters of the Black Sea estimates a particle export rate from the oxygenated surface layer to the deep anoxic waters equivalent to 8% of the total N production. We extrapolate an annual mean f-ratio of 0.38 by the conventional formulation (NO 3- uptake: total N uptake). However, the balanced N budget permits a direct comparison of allochthonous sources of N to total N production in this unusual aquatic ecosystem, resulting in an f-ratio of 0.17, which is reconciled with particulate export when the budgeted losses due to anammox and denitrification are included. The NO 3- content of the CIL is sensitive to year-to-year fluctuations in the source of N from the NWS. These processes plus the intensity of winter mixing, which supplies new N for the fall-winter bloom, are influenced by climate. Oscillations in winter temperature over the past few decades allow inference as to how the Black Sea N budget may be affected by future warmer conditions for this region.

McCarthy, James J.; Yilmaz, Aysen; Coban-Yildiz, Yesim; Nevins, John L.

2007-09-01

307

Copper as a robust and transparent electrocatalyst for water oxidation.  

PubMed

Copper metal is in theory a viable oxidative electrocatalyst based on surface oxidation to Cu(III) and/or Cu(IV) , but its use in water oxidation has been impeded by anodic corrosion. The in?situ formation of an efficient interfacial oxygen-evolving Cu catalyst from Cu(II) in concentrated carbonate solutions is presented. The catalyst necessitates use of dissolved Cu(II) and accesses the higher oxidation states prior to decompostion to form an active surface film, which is limited by solution conditions. This observation and restriction led to the exploration of ways to use surface-protected Cu metal as a robust electrocatalyst for water oxidation. Formation of a compact film of CuO on Cu surface prevents anodic corrosion and results in sustained catalytic water oxidation. The Cu/CuO surface stabilization was also applied to Cu nanowire films, which are transparent and flexible electrocatalysts for water oxidation and are an attractive alternative to ITO-supported catalysts for photoelectrochemical applications. PMID:25581365

Du, Jialei; Chen, Zuofeng; Ye, Shengrong; Wiley, Benjamin J; Meyer, Thomas J

2015-02-01

308

Nanolayered manganese oxide/C(60) composite: a good water-oxidizing catalyst for artificial photosynthetic systems.  

PubMed

For the first time, we considered Mn oxide/C60 composites as water-oxidizing catalysts. The composites were synthesized by easy and simple procedures, and characterized by some methods. The water-oxidizing activities of these composites were also measured in the presence of cerium(iv) ammonium nitrate. We found that the nanolayered Mn oxide/C60 composites show promising activity toward water oxidation. PMID:24984108

Najafpour, Mohammad Mahdi; Abasi, Mahnaz; Tomo, Tatsuya; Allakhverdiev, Suleyman I

2014-08-21

309

Evidence for intensification of the global water cycle: Review and synthesis  

Microsoft Academic Search

One of the more important questions in hydrology is: if the climate warms in the future, will there be an intensification of the water cycle and, if so, the nature of that intensification? There is considerable interest in this question because an intensification of the water cycle may lead to changes in water-resource availability, an increase in the frequency and

Thomas G. Huntington

2006-01-01

310

Future climate change, the agricultural water cycle, and agricultural production in China  

Microsoft Academic Search

Climate change would have a major impact on the hydrological cycle and consequently on available water resources, the potential for flood and drought, and agricultural productivity. In this study, the impacts of climate change on the agricultural water cycle and their implications for agricultural production in the 2020s were assessed by water-balance calculations for Chinese croplands. Temporal and spatial changes

Fulu Tao; Masayuki Yokozawa; Yousay Hayashi; Erda Lina

2003-01-01

311

The NASA Energy and Water cycle Extreme (NEWSE) Integration Project  

NASA Astrophysics Data System (ADS)

Skillful predictions of water and energy cycle extremes (flood and drought) are elusive. To better understand the mechanisms responsible for water and energy extremes, and to make decisive progress in predicting these extremes, the collaborative NASA Energy and Water cycle Extremes (NEWSE) Integration Project, is studying these extremes in the U.S. Southern Great Plains (SGP) during 2006-2007, including their relationships with continental and global scale processes, and assessment of their predictability on multiple space and time scales. It is our hypothesis that an integrative analysis of observed extremes which reflects the current understanding of the role of SST and soil moisture variability influences on atmospheric heating and forcing of planetary waves, incorporating recently available global and regional hydro- meteorological datasets (i.e., precipitation, water vapor, clouds, etc.) in conjunction with advances in data assimilation, can lead to new insights into the factors that lead to persistent drought and flooding. We will show initial results of this project, whose goals are toprovide an improved definition, attribution and prediction on sub-seasonal to interannual time scales, improved understanding of the mechanisms of decadal drought and its predictability, including the impacts of SST variability and deep soil moisture variability, and improved monitoring/attributions, with transition to applications; a bridging of the gap between hydrological forecasts and stakeholders (utilization of probabilistic forecasts, education, forecast interpretation for different sectors, assessment of uncertainties for different sectors, etc.). *The NEWSE Team is: Romanou, Anastasiam, Columbia U.; Brian Soden, U. Miami; William Lapenta, NASA- MSFC; Megan Larko, CREW; Bing Lin, NASA-LaRC; Christa Peters-Lidard, NASA-GSFC; Xiquan Dong, U. North Dakota; Debbie Belvedere, CREW; Mathew Sapiano, U. Maryland; Duane Waliser, NASA-JPL; Eni Njoku, NASA/JPL; Eric Fetzer, NASA-JPL; Eyal Amitai, NASA-GSFC; Xiaogang Gao, U. California, Irvine; George Huffman, NASA-GSFC & SSAI; Jared Entin, NASA; Joseph Santanello, NASA-GSFC; John Roads, UCSD; W. Timothy Liu, NASA-JPL; Lixin Lu, Colorado State U.; Zhengzhao Luo, Colorado State U.; Michael Bosilovich, NASA-GSFC; Michael Jasinski, NASA-GSFC; William Olson, NASA-GSFC & UMBC-GEST; Pete Robertson, NASA-MSFC; Phil Arkin, U. Maryland; Paul Houser, CREW & GMU; Ralph Ferraro, NOAA; Pete Robertson, NASA-MSFC; Robert Schiffer; UMBC-GEST; Sujay Kumar, NASA-GSFC; Joseph A. Santanello, NASA-GSFC; Tristan L'Ecuyer, Colorado State U.; Wei-Kuo Tao; NASA-GSFC; Xia Feng; George Mason U.

Houser, P. R.; Lapenta, W.; Schiffer, R.

2008-05-01

312

An improvement in the use of plutonium in pressurized water reactors; The subassembly mixed-oxide fuel management concept  

Microsoft Academic Search

An unconventional mixed-oxide (MOX) fuel management concept for a pressurized water reactor core is proposed. Subassembly management (SAM) is an in-out reloading scheme applied within MOX assemblies that are reconstructed'' at each end of cycle. The SAM concept needs only one kind of MOX fuel pin instead of the three pins necessary in the standard MOX fuel management concept; it

C. Bangil; G. Gambier; M. Soldevila

1989-01-01

313

Biomimetic metal oxides for the extraction of nanoparticles from water  

NASA Astrophysics Data System (ADS)

Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications.Contamination of nanomaterials in the environment will pose significant health risks in the future. A viable purification method is necessary to address this problem. Here we report the synthesis and application of a series of metal oxides prepared using a biological template for the removal of nanoparticles from the aqueous environment. A simple synthesis of metal oxides such as ZnO, NiO, CuO, Co3O4 and CeO2 employing eggshell membrane (ESM) as a biotemplate is reported. The morphology of the metal oxide powders was characterized using electron microscopes and the lattice structure was established using X-ray diffraction methods. Extraction of nanoparticles from water was carried out to compare the efficiency of metal oxides. NiO showed good extraction efficiency in removing gold and silver nanoparticles from spiked water samples within an hour. Easy access and enhanced stability of metal oxides makes them interesting candidates for applications in industrial effluent treatments and water purifications. Electronic supplementary information (ESI) available: XRD and EDS analysis of the prepared metal oxides, EDS analysis of nanoparticles adsorbed on the surface of metal oxides and SEM micrographs of metal oxides are included. See DOI: 10.1039/c3nr34221b

Mallampati, Ramakrishna; Valiyaveettil, Suresh

2013-03-01

314

Direct-Coupling O? Bond Forming Pathway in Cobalt Oxide Water Oxidation Catalysts  

E-print Network

We report a catalytic mechanism for water oxidation in a cobalt oxide cubane model compound, in which the crucial O–O bond formation step takes place by direct coupling between two CoIV(O) metal oxo groups. Our results are ...

Wang, Lee-Ping

315

Cyanamide route to calcium-manganese oxide foams for water oxidation.  

PubMed

In nature, photosynthetic water oxidation is efficiently catalysed at a protein-bound ?-oxido Mn4Ca cluster. This cluster consists of earth abundant, non-toxic elements and serves as a paragon for development of synthetic catalysts. In this study we developed porous calcium-manganese oxides with a unique foam-like nanostructure prepared via a facile and robust synthetic route using cyanamide as a porogen. A series of such oxide foams annealed at different temperatures was characterized by TEM, SEM, XRD, N2 physisorption, and X-ray absorption spectroscopy (XAS) in order to correlate crystallinity, atomic structure, surface area and oxidation state of the materials with catalytic activity. Some of the resulting Ca-Mn oxides show high activity as catalysts for water oxidation in the presence of cerium(iv) ammonium nitrate as a non-oxo transfer oxidant. An amorphous calcium-manganese-oxide foam with 130 m(2) g(-1) surface area and Mn oxidation state of +3.6 was identified to be most active; its activity is superior to previously reported Ca-Mn oxides. At the atomic level, this material shares structural motifs with the biological paragon as revealed by dual-edge XAS at the Mn and Ca K-edge. Rather than nanostructure and surface area, the atomic structure of the Ca-Mn oxide and the extent of structural order appear to be crucial determinants of catalytic activity. Fully disordered low-valent Mn materials as well as high-valent but crystalline Mn-Ca oxides are unreactive. Highly disordered variants of layered manganese oxide with Ca and water molecules interfacing layer fragments are most reactive. PMID:24091767

Baktash, Elham; Zaharieva, Ivelina; Schröder, Marc; Goebel, Caren; Dau, Holger; Thomas, Arne

2013-12-28

316

Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst.  

PubMed

In any artificial photosynthetic system, the oxidation of water to molecular oxygen provides the electrons needed for the reduction of protons or carbon dioxide to a fuel. Understanding how this four-electron reaction works in detail is important for the development of improved robust catalysts made of Earth-abundant materials, like first-row transition-metal oxides. Here, using time-resolved Fourier-transform infrared spectroscopy and under reaction conditions, we identify intermediates of water oxidation catalysed by an abundant metal-oxide catalyst, cobalt oxide (Co3O4). One intermediate is a surface superoxide (three-electron oxidation intermediate absorbing at 1,013 cm(-1)), whereas a second observed intermediate is attributed to an oxo Co(IV) site (one-electron oxidation intermediate absorbing at 840 cm(-1)). The temporal behaviour of the intermediates reveals that they belong to different catalytic sites. Knowledge of the structure and kinetics of surface intermediates will enable the design of improved metal-oxide materials for more efficient water oxidation catalysis. PMID:24651205

Zhang, Miao; de Respinis, Moreno; Frei, Heinz

2014-04-01

317

Time-resolved observations of water oxidation intermediates on a cobalt oxide nanoparticle catalyst  

NASA Astrophysics Data System (ADS)

In any artificial photosynthetic system, the oxidation of water to molecular oxygen provides the electrons needed for the reduction of protons or carbon dioxide to a fuel. Understanding how this four-electron reaction works in detail is important for the development of improved robust catalysts made of Earth-abundant materials, like first-row transition-metal oxides. Here, using time-resolved Fourier-transform infrared spectroscopy and under reaction conditions, we identify intermediates of water oxidation catalysed by an abundant metal-oxide catalyst, cobalt oxide (Co3O4). One intermediate is a surface superoxide (three-electron oxidation intermediate absorbing at 1,013 cm-1), whereas a second observed intermediate is attributed to an oxo Co(IV) site (one-electron oxidation intermediate absorbing at 840 cm-1). The temporal behaviour of the intermediates reveals that they belong to different catalytic sites. Knowledge of the structure and kinetics of surface intermediates will enable the design of improved metal-oxide materials for more efficient water oxidation catalysis.

Zhang, Miao; de Respinis, Moreno; Frei, Heinz

2014-04-01

318

Free amino acids in marine rains: evidence for oxidation and potential role in nitrogen cycling  

Microsoft Academic Search

Previous studies of dissolved organic nitrogen (DON) in precipitation have addressed various aspects of nutrient transport and global nitrogen cycling1. In most of these studies however, the detailed chemical composition of DON was not determined. Analyses of specific organic nitrogen compounds within precipitation can yield new information about sources and transformations of DON as well as about heterogeneous oxidative processes

Kenneth Mopper; Rod G. Zika

1987-01-01

319

Impact of Unusual Fatty Acid Synthesis on Futile Cycling through Oxidation and on Gene Expression in  

Microsoft Academic Search

Arabidopsis expressing the castor bean (Ricinus communis) oleate 12-hydroxylase or the Crepis palaestina linoleate 12- epoxygenase in developing seeds typically accumulate low levels of ricinoleic acid and vernolic acid, respectively. We have examined the presence of a futile cycle of fatty acid degradation in developing seeds using the synthesis of polyhydroxy- alkanoate (PHA) from the intermediates of the peroxisomal -oxidation

Laurence Moire; Enea Rezzonico; Simon Goepfert; Yves Poirier

320

Origin of anomalous water permeation through graphene oxide membrane.  

PubMed

Water inside the low-dimensional carbon structures has been considered seriously owing to fundamental interest in its flow and structures as well as its practical impact. Recently, the anomalous perfect penetration of water through graphene oxide membrane was demonstrated although the membrane was impenetrable for other liquids and even gases. The unusual auxetic behavior of graphene oxide in the presence of water was also reported. Here, on the basis of first-principles calculations, we establish atomistic models for hybrid systems composed of water and graphene oxides revealing the anomalous water behavior inside the stacked graphene oxides. We show that formation of hexagonal ice bilayer in between the flakes as well as melting transition of ice at the edges of flakes are crucial to realize the perfect water permeation across the whole stacked structures. The distance between adjacent layers that can be controlled either by oxygen reduction process or pressure is shown to determine the water flow thus highlighting a unique water dynamics in randomly connected two-dimensional spaces. PMID:23859009

Boukhvalov, Danil W; Katsnelson, Mikhail I; Son, Young-Woo

2013-08-14

321

Design requirements for the supercritical water oxidation test bed  

Microsoft Academic Search

This report describes the design requirements for the supercritical water oxidation (SCWO) test bed that will be located at the Idaho National Engineering Laboratory (INEL). The test bed will process a maximum of 50 gph of waste plus the required volume of cooling water. The test bed will evaluate the performance of a number of SCWO reactor designs. The goal

J. M. Svoboda; D. J. Valentich

1994-01-01

322

Designing Green Oxidation Catalysts for Purifying Environmental Waters  

E-print Network

Designing Green Oxidation Catalysts for Purifying Environmental Waters W. Chadwick Ellis, Camly T for green catalysts for water purification is the avoidance of endocrine disruptors, which can impair hormone receptors, suggesting that 2 do not bind to the receptors and reducing concerns that the catalysts

Blumberg, Bruce

323

The inorganic biochemistry of photosynthetic oxygen evolution\\/water oxidation  

Microsoft Academic Search

At the request of the organizer of this special edition, we have attempted to do several things in this manuscript: (1) we present a mini-review of recent, selected, works on the light-induced inorganic biogenesis (photoactivation), composition and structure of the inorganic core responsible for photosynthetic water oxidation; (2) we summarize a new proposal for the evolutionary origin of the water

G. M. Ananyev; L. Zaltsman; C. Vasko; G. C. Dismukes

2001-01-01

324

Thaumarchaeal ammonium oxidation and evidence for a nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps  

PubMed Central

Previous studies had suggested the presence of ammonium oxidizing Thaumarchaeota as well as nitrite oxidizing Bacteria in the subsurface spring called Franz Josef Quelle (FJQ), a slightly radioactive thermal mineral spring with a temperature of 43.6–47°C near the alpine village of Bad Gastein, Austria. The microbiological consortium of the FJQ was investigated for its utilization of nitrogen compounds and the putative presence of a subsurface nitrogen cycle. Microcosm experiments made with samples from the spring water, containing planktonic microorganisms, or from biofilms, were used in this study. Three slightly different media, enriched with vitamins and trace elements, and two incubation temperatures (30 and 40°C, respectively) were employed. Under aerobic conditions, high rates of conversion of ammonium to nitrite, as well as nitrite to nitrate were measured. Under oxygen-limited conditions nitrate was converted to gaseous compounds. Stable isotope probing with 15NH4Cl or (15NH4)2SO4as sole energy sources revealed incorporation of 15N into community DNA. Genomic DNA as well as RNA were extracted from all microcosms. The following genes or fragments of genes were successfully amplified, cloned and sequenced by standard PCR from DNA extracts: Ammonia monooxygenase subunit A (amoA), nitrite oxidoreductase subunits A and B (nxrA and nxrB), nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductases (cnorB and qnorB), nitrous oxide reductase (nosZ). Reverse transcription of extracted total RNA and real-time PCR suggested the expression of each of those genes. Nitrogen fixation (as probed with nifH and nifD) was not detected. However, a geological origin of NH+4 in the water of the FJQ cannot be excluded, considering the silicate, granite and gneiss containing environment. The data suggested the operation of a nitrogen cycle in the subsurface environment of the FJQ. PMID:24904540

Gerbl, Friedrich W.; Weidler, Gerhard W.; Wanek, Wolfgang; Erhardt, Angelika; Stan-Lotter, Helga

2014-01-01

325

Thaumarchaeal ammonium oxidation and evidence for a nitrogen cycle in a subsurface radioactive thermal spring in the Austrian Central Alps.  

PubMed

Previous studies had suggested the presence of ammonium oxidizing Thaumarchaeota as well as nitrite oxidizing Bacteria in the subsurface spring called Franz Josef Quelle (FJQ), a slightly radioactive thermal mineral spring with a temperature of 43.6-47°C near the alpine village of Bad Gastein, Austria. The microbiological consortium of the FJQ was investigated for its utilization of nitrogen compounds and the putative presence of a subsurface nitrogen cycle. Microcosm experiments made with samples from the spring water, containing planktonic microorganisms, or from biofilms, were used in this study. Three slightly different media, enriched with vitamins and trace elements, and two incubation temperatures (30 and 40°C, respectively) were employed. Under aerobic conditions, high rates of conversion of ammonium to nitrite, as well as nitrite to nitrate were measured. Under oxygen-limited conditions nitrate was converted to gaseous compounds. Stable isotope probing with (15)NH4Cl or ((15)NH4)2SO4as sole energy sources revealed incorporation of (15)N into community DNA. Genomic DNA as well as RNA were extracted from all microcosms. The following genes or fragments of genes were successfully amplified, cloned and sequenced by standard PCR from DNA extracts: Ammonia monooxygenase subunit A (amoA), nitrite oxidoreductase subunits A and B (nxrA and nxrB), nitrate reductase (narG), nitrite reductase (nirS), nitric oxide reductases (cnorB and qnorB), nitrous oxide reductase (nosZ). Reverse transcription of extracted total RNA and real-time PCR suggested the expression of each of those genes. Nitrogen fixation (as probed with nifH and nifD) was not detected. However, a geological origin of NH(+) 4 in the water of the FJQ cannot be excluded, considering the silicate, granite and gneiss containing environment. The data suggested the operation of a nitrogen cycle in the subsurface environment of the FJQ. PMID:24904540

Gerbl, Friedrich W; Weidler, Gerhard W; Wanek, Wolfgang; Erhardt, Angelika; Stan-Lotter, Helga

2014-01-01

326

Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation  

Microsoft Academic Search

A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient

Yi Wei Chen; Jonathan D. Prange; Simon Dühnen; Yohan Park; Marika Gunji; Christopher E. D. Chidsey; Paul C. McIntyre

2011-01-01

327

Oxidation of arsenate(III) with manganese oxides in water treatment  

Microsoft Academic Search

Arsenate(III) is the more toxic form of inorganic arsenic and its removal from drinking water is less effective as compared to arsenate(V). Arsenate(III) persists in aerated water, even at high pH, but is easily oxidized by managanese dioxides. The oxidation of As(III) follows a second order rate law with respect to As(III). The reaction rate is effected by the initial

Wolfgang Driehaus; Reiner Seith; Martin Jekel

1995-01-01

328

Nanostructured manganese oxides as highly active water oxidation catalysts: a boost from manganese precursor chemistry.  

PubMed

We present a facile synthesis of bioinspired manganese oxides for chemical and photocatalytic water oxidation, starting from a reliable and versatile manganese(II) oxalate single-source precursor (SSP) accessible through an inverse micellar molecular approach. Strikingly, thermal decomposition of the latter precursor in various environments (air, nitrogen, and vacuum) led to the three different mineral phases of bixbyite (Mn2 O3 ), hausmannite (Mn3 O4 ), and manganosite (MnO). Initial chemical water oxidation experiments using ceric ammonium nitrate (CAN) gave the maximum catalytic activity for Mn2 O3 and MnO whereas Mn3 O4 had a limited activity. The substantial increase in the catalytic activity of MnO in chemical water oxidation was demonstrated by the fact that a phase transformation occurs at the surface from nanocrystalline MnO into an amorphous MnOx (1oxidizing agent. Photocatalytic water oxidation in the presence of [Ru(bpy)3 ](2+) (bpy=2,2'-bipyridine) as a sensitizer and peroxodisulfate as an electron acceptor was carried out for all three manganese oxides including the newly formed amorphous MnOx . Both Mn2 O3 and the amorphous MnOx exhibit tremendous enhancement in oxygen evolution during photocatalysis and are much higher in comparison to so far known bioinspired manganese oxides and calcium-manganese oxides. Also, for the first time, a new approach for the representation of activities of water oxidation catalysts has been proposed by determining the amount of accessible manganese centers. PMID:25044528

Menezes, Prashanth W; Indra, Arindam; Littlewood, Patrick; Schwarze, Michael; Göbel, Caren; Schomäcker, Reinhard; Driess, Matthias

2014-08-01

329

Ice haze, snow, and the Mars water cycle  

NASA Technical Reports Server (NTRS)

Light curves and extinction profiles derived from Martian limb observations are used to constrain the atmospheric temperature structure in regions of the atmosphere with thin haze and to analyze the haze particle properties and atmospheric eddy mixing. Temperature between 170 and 190 K are obtained for three cases at levels in the atmosphere ranging from 20 to 50 km. Eddy diffusion coefficients around 100,000 sq cm/s, typical of a nonconvecting atmosphere, are derived in the haze regions at times when the atmosphere is relatively clear of dust. This parameter apparently changes by more than three orders of magnitude with season and local conditions. The derived particle size parameter varies systematically by more than an order of magnitude with condensation level, in such a way that the characteristic fall time is always about one Martian day. Ice hazes provide a mechanism for scavenging water vapor in the thin Mars atmosphere and may play a key role in the seasonal cycle of water on Mars.

Kahn, Ralph

1990-01-01

330

Plumbing the global carbon cycle: Integrating inland waters into the terrestrial carbon budget  

USGS Publications Warehouse

Because freshwater covers such a small fraction of the Earth's surface area, inland freshwater ecosystems (particularly lakes, rivers, and reservoirs) have rarely been considered as potentially important quantitative components of the carbon cycle at either global or regional scales. By taking published estimates of gas exchange, sediment accumulation, and carbon transport for a variety of aquatic systems, we have constructed a budget for the role of inland water ecosystems in the global carbon cycle. Our analysis conservatively estimates that inland waters annually receive, from a combination of background and anthropogenically altered sources, on the order of 1.9 Pg C y-1 from the terrestrial landscape, of which about 0.2 is buried in aquatic sediments, at least 0.8 (possibly much more) is returned to the atmosphere as gas exchange while the remaining 0.9 Pg y-1 is delivered to the oceans, roughly equally as inorganic and organic carbon. Thus, roughly twice as much C enters inland aquatic systems from land as is exported from land to the sea. Over prolonged time net carbon fluxes in aquatic systems tend to be greater per unit area than in much of the surrounding land. Although their area is small, these freshwater aquatic systems can affect regional C balances. Further, the inclusion of inland, freshwater ecosystems provides useful insight about the storage, oxidation and transport of terrestrial C, and may warrant a revision of how the modern net C sink on land is described. ?? 2007 Springer Science+Business Media, LLC.

Cole, J.J.; Prairie, Y.T.; Caraco, N.F.; McDowell, W.H.; Tranvik, L.J.; Striegl, R.G.; Duarte, C.M.; Kortelainen, P.; Downing, J.A.; Middelburg, J.J.; Melack, J.

2007-01-01

331

Stoichiometry of Reducing Equivalents and Splitting of Water in the Citric Acid Cycle.  

ERIC Educational Resources Information Center

Presents a solution to the problem of finding the source of extra reducing equivalents, and accomplishing the stoichiometry of glucose oxidation reactions. Discusses the citric acid cycle and glycolysis. (CW)

Madeira, Vitor M. C.

1988-01-01

332

Fatigue oxidation interaction in a superalloy—application to life prediction in high temperature low cycle fatigue  

Microsoft Academic Search

A study of the interaction between fatigue and oxidation has been carried out in the case of a cast cobalt base superalloy\\u000a MARM 509 tested in laboratory air at 900 C. The influence of fatigue cycling on oxidation of this alloy has been studied\\u000a by quantitative metallography on polished specimens exposed to air in a furnace and on strain-cycled low-cycle

J. Reuchet; L. Remy

1983-01-01

333

Atomic layer-deposited tunnel oxide stabilizes silicon photoanodes for water oxidation  

NASA Astrophysics Data System (ADS)

A leading approach for large-scale electrochemical energy production with minimal global-warming gas emission is to use a renewable source of electricity, such as solar energy, to oxidize water, providing the abundant source of electrons needed in fuel synthesis. We report corrosion-resistant, nanocomposite anodes for the oxidation of water required to produce renewable fuels. Silicon, an earth-abundant element and an efficient photovoltaic material, is protected by atomic layer deposition (ALD) of a highly uniform, 2?nm thick layer of titanium dioxide (TiO2) and then coated with an optically transmitting layer of a known catalyst (3?nm iridium). Photoelectrochemical water oxidation was observed to occur below the reversible potential whereas dark electrochemical water oxidation was found to have low-to-moderate overpotentials at all pH values, resulting in an inferred photovoltage of ~550?mV. Water oxidation is sustained at these anodes for many hours in harsh pH and oxidative environments whereas comparable silicon anodes without the TiO2 coating quickly fail. The desirable electrochemical efficiency and corrosion resistance of these anodes is made possible by the low electron-tunnelling resistance (<0.006???cm2 for p+-Si) and uniform thickness of atomic-layer deposited TiO2.

Chen, Yi Wei; Prange, Jonathan D.; Dühnen, Simon; Park, Yohan; Gunji, Marika; Chidsey, Christopher E. D.; McIntyre, Paul C.

2011-07-01

334

TRMM and Its Connection to the Global Water Cycle  

NASA Technical Reports Server (NTRS)

The importance of quantitative knowledge of tropical rainfall, its associated latent heating and variability is summarized in the context of the global hydrologic cycle. Much of the tropics is covered by oceans. What land exists, is covered largely by rainforests that are only thinly populated. The only way to adequately measure the global tropical rainfall for climate and general circulation models is from space. The TRMM orbit is inclined 35' leading to good sampling in the tropics and a rapid precession to study the diurnal cycle of precipitation. The precipitation instrument complement consists of the first rain radar to be flown in space (PR), a multi-channel passive microwave sensor (TMI) and a five-channel VIS/IR (VIRS) sensor. The precipitation radar operates at a frequency of 13.6 GHz. The swath width is 220 km, with a horizontal resolution of 4 km and the vertical resolution of 250 in. The minimum detectable signal from the precipitation radar has been measured at 17 dBZ. The TMI instrument is designed similar to the SSM/I with two important changes. The 22.235 GHz water vapor absorption channel of the SSM/I was moved to 21.3 GHz in order to avoid saturation in the tropics and 10.7 GHz V&H polarized channels were added to expand the dynamic range of rainfall estimates. The resolution of the TMI varies from 4.6 km at 85 GHz to 36 km at 10.7 GHz. The visible and infrared sensor (VIRS) measures radiation at 0.63, 1.6, 3.75, 10.8 and 12.0 microns. The spatial resolution of all five VIRS channels is 2 km at nadir. In addition to the three primary rainfall instruments, TRMM will also carry a Lightning Imaging Sensor (LIS) and a Clouds and the Earth's Radiant Energy System (CERES) instrument.

Kummerow, Christian; Hong, Ye

1999-01-01

335

Sunlight-induced photochemical decay of oxidants in natural waters: implications in ballast water treatment.  

PubMed

The transport and discharge of ship ballast water has been recognized as a major vector for the introduction of invasive species. Chemical oxidants, long used in drinking water and wastewater treatment, are alternative treatment methods for the control of invasive species currently being tested for use on ships. One concern when a ballasted vessel arrives in port is the adverse effects of residual oxidant in the treated water. The most common oxidants include chlorine (HOCl/OCl-), bromine (HOBr/OBr-), ozone (03), hydrogen peroxide (H2O2), chlorine dioxide (ClO2), and monochloramine (NH2Cl). The present study was undertaken to evaluate the sunlight-mediated photochemical decomposition of these oxidants. Sunlight photodecomposition was measured at various pH using either distilled water or oligotrophic Gulf Stream water for specific oxidants. For selected oxidants, quantum yields at specific wavelengths were obtained. An environmental photochemical model, GCSOLAR, also provided predictions of the fate (sunlight photolysis half-lives) of HOCI/OCl-, HOBr/OBr-, ClO2, and NH2Cl for two different seasons at latitude 40 degrees and in water with two different concentrations of chromophoric dissolved organic matter. These data are useful in assessing the environmental fate of ballast water treatment oxidants if they were to be discharged in port. PMID:17547204

Cooper, William J; Jones, Adam C; Whitehead, Robert F; Zika, Rod G

2007-05-15

336

Photoassisted oxidation of oil films on water  

SciTech Connect

The objective of the project is to develop TiO{sub 2}-based photocatalysts for the solar assisted oxidative dissolution of oil slicks. In a TiO{sub 2} crystal, absorption of a photon generates an electron-hole pair. The electron reacts with surface-adsorbed oxygen, reducing it to hydrogen peroxide; the hole directly oxidizes adsorbed organic compounds, usually via an intermediate OH radical. Since the density of TiO{sub 2} (3.8g/cc for anatase, 4.3 g/cc for rutile) is greater than that of either oil or seawater, TiO{sub 2} crystals are attached to inexpensive, engineered hollow glass microspheres to ensure flotation on the oil slick surface. Portions of the microsphere surface not covered by TiO{sub 2} are made oleophilic so that the microbeads will be preferentially attracted to the oil-air interface.

Heller, A.; Brock, J.R.

1991-08-01

337

Roles of surface water areas for water and solute cycle in Hanoi city, Viet Nam  

NASA Astrophysics Data System (ADS)

Hanoi city, the capital of Viet Nam, has developed beside the Red river. Recent rapid urbanization of this city has reduced a large number of natural water areas such as lakes, ponds and canals not only in the central area but the suburban area. Contrary, the urbanization has increased artificial water areas such as pond for fish cultivation and landscaping. On the other hand, the urbanization has induced the inflow of waste water from households and various kinds of factories to these water areas because of delay of sewerage system development. Inflow of the waste water has induced eutrophication and pollution of these water areas. Also, there is a possibility of groundwater pollution by infiltration of polluted surface water. However, the role of these water areas for water cycle and solute transport is not clarified. Therefore, this study focuses on the interaction between surface water areas and groundwater in Hanoi city to evaluate appropriate land development and groundwater resource management. We are carrying out three approaches: a) understanding of geochemical characteristics of surface water and groundwater, b) monitoring of water levels of pond and groundwater, c) sampling of soil and pond sediment. Correlation between d18O and dD of precipitation (after GNIP), the Red River (after GNIR) and the water samples of this study showed that the groundwater is composed of precipitation, the Red River and surface water that has evaporation process. Contribution of the surface water with evaporation process was widely found in the study area. As for groundwater monitoring, the Holocene aquifers at two sites were in unconfined condition in dry season and the groundwater levels in the aquifer continued to increase through rainy season. The results of isotopic analysis and groundwater level monitoring showed that the surface water areas are one of the major groundwater sources. On the other hand, concentrations of dissolved Arsenic (filtered by 0.45um) in the pore water of the pond sediments were much higher than the pond water and closed to that of groundwater. Also, other metal elements showed the same trend. This result suggested that Arsenic and other metal elements recharged to these ponds is probably adsorbed and removed by sediments (including organic matters). That is, pond sediment plays an important role for solute transport as a filter of Arsenic and metal elements. The results of this study strongly suggest that the natural and artificial surface water areas have important roles for water cycle and solute transport in Hanoi city. Although the number of the natural water areas is decreasing, dredging of artificial water areas increases the infiltration from the surface to aquifers. Therefore, qualitative and quantitative preservation of the surface water areas is important for conservation of groundwater environment and contribute to sustainable groundwater management in Hanoi city.

Hayashi, Takeshi; Kuroda, Keisuke; Do Thuan, An; Tran Thi Viet, Nga; Takizawa, Satoshi

2013-04-01

338

SHORTER MENSTRUAL CYCLES ASSOCIATED WITH CHLORINATION BY-PRODUCTS IN DRINKING WATER  

EPA Science Inventory

Shorter Menstrual Cycles Associated with Chlorination by-Products in Drinking Water. Gayle Windham, Kirsten Waller, Meredith Anderson, Laura Fenster, Pauline Mendola, Shanna Swan. California Department of Health Services. In previous studies of tap water consumption we...

339

Salty-ocean water cycle variability and change (Invited)  

NASA Astrophysics Data System (ADS)

Previous work has highlighted a clear long-term salinity pattern amplification (PA) in both observations and modelled historical and future climate simulations. These results suggest that fresh ocean regions are becoming fresher, and salty regions saltier in response to evaporation minus precipitation (E-P) changes driven by a warming Earth - an ocean proxy for the ';rich get richer' (wet gets wetter, dry gets drier) mechanism. These global evaporation (E) and precipitation (P) surface fluxes over the ocean comprise 75-85% of the climatological annual mean global water cycle across the entire Earth surface and so are clearly a good place to look for temporal variations in the observed record. Using CMIP models we extend upon previous work to investigate the influence of climate variability on previously resolved PA estimates. Using the CMIP (Coupled Model Intercomparison Project phase 3 & 5) 20C3M/historical (20th century), SRES/RCP (future 21st century) and pre-industrial (piControl; unforced) simulations, we diagnose the relationship between the simulated ocean surface salinity and the simulated E-P (water cycle) changes. We investigate the intrinsic variability of both the modelled salinity and E-P fields to ascertain an envelope of modelled unforced (piControl) climate variability. We compare these unforced distributions to those of weakly- (20C3M/historical) and strongly-forced (SRES/RCP) simulations to determine the emergence of an anthropogenic-forced fingerprint from intrinsic variability as defined by the models. Using these forced-signal versus variability estimates from models, we revisit the observed salinity PA, investigate differences between the CMIP5 and CMIP3 models suites, and investigate the significance of resolved changes over 1950-present and discuss any implications to previous conclusions discovered by this updated analysis. Work undertaken at Lawrence Livermore National Laboratory is supported by the U.S. Department of Energy under contract DE-AC52-07NA27344. LLNL IM release number: LLNL-CONF-641935

Durack, P. J.; Gleckler, P. J.; Bindoff, N. L.

2013-12-01

340

Subcritical and supercritical water oxidation of CELSS model wastes  

NASA Technical Reports Server (NTRS)

A mixture of ammonium hydroxide with acetic acid and a slurry of human feces, urine, and wipes were used as CELSS model wastes to be wet-oxidized at temperatures from 250 to 500 C, i.e. below and above the critical point of water (374 C and 218 kg/sq cm or 21.4 MPa). The effects of oxidation temperature ( 250-500 C) and residence time (0-120 mn) on carbon and nitrogen and on metal corrosion from the reactor material were studied. Almost all of the organic matter in the model wastes was oxidized in the temperature range from 400 to 500 C, above the critical conditions for water. In contrast, only a small portion of the organic matter was oxidized at subcritical conditions. A substantial amount of nitrogen remained in solution in the form of ammonia at temperatures ranging from 350 to 450 C suggesting that, around 400 C, organic carbon is completely oxidized and most of the nitrogen is retained in solution. The Hastelloy C-276 alloy reactor corroded during subcritical and supercritical water oxidation.

Takahashi, Y.; Wydeven, T.; Koo, C.

1989-01-01

341

The Use of Water Vapor as a Refrigerant: Impact of Cycle Modifications on Commercial Viability  

SciTech Connect

This project investigated the economic viability of using water as the refrigerant in a 1000-ton chiller application. The most attractive water cycle configuration was found to be a flash-intercooled, two-stage cycle using centrifugal compressors and direct contact heat exchangers. Component level models were developed that could be used to predict the size and performance of the compressors and heat exchangers in this cycle as well as in a baseline, R-134a refrigeration cycle consistent with chillers in use today. A survey of several chiller manufacturers provided information that was used to validate and refine these component models. The component models were integrated into cycle models that were subsequently used to investigate the life-cycle costs of both an R-134a and water refrigeration cycle. It was found that the first cost associated with the water as a refrigerant cycle greatly exceeded the savings in operating costs associated with its somewhat higher COP. Therefore, the water refrigeration cycle is not an economically attractive option to today's R-134a refrigeration system. There are a number of other issues, most notably the requirements associated with purging non-condensable gases that accumulate in a direct contact heat exchanger, which will further reduce the economic viability of the water cycle.

Brandon F. Lachner, Jr.; Gregory F. Nellis; Douglas T. Reindl

2004-08-30

342

Water oxidation by manganese oxides, a new step towards a complete picture: simplicity is the ultimate sophistication.  

PubMed

We, for the first time, report that many Mn oxides (Mn3O4, ?-Mn2O3, ?-MnO2, CaMnO3, Ca2Mn3O8, CaMn3O6 and CaMn4O8) in the presence of cerium(IV) ammonium nitrate, in the water oxidation, convert to layered Mn oxide. This layered Mn oxide is an efficient water oxidizing catalyst. PMID:23838901

Najafpour, Mohammad Mahdi; Sedigh, Davood Jafarian

2013-09-14

343

Alternative water sources: Desalination model provides life-cycle costs of facility  

E-print Network

Story by Danielle Supercinski tx H2O | pg. 8 Alternative water sourcees Desalination model provides life-cycle costs of facility platform and design standards as DESAL ECONOMICS?, but created to analyze con- ventional surface water treatment... to determine the economic and financial life-cycle costs of building and operating four water treatment facilities in South Texas. One facility was the Southmost Regional Water Authority Regional Desalination Plant near Brownsville. Sturdi- vant said...

Supercinski, Danielle

2009-01-01

344

Multiple Observation Types Jointly Constrain Terrestrial Carbon and Water Cycles  

NASA Astrophysics Data System (ADS)

Information about the carbon cycle potentially constrains the water cycle, and vice versa. This paper explores the utility of multiple observation sets to constrain carbon and water fluxes and stores in a land surface model, and a resulting determination of the Australian terrestrial carbon budget. Observations include streamflow from 416 gauged catchments, measurements of evapotranspiration (ET) and net ecosystem production (NEP) from 12 eddy-flux sites, litterfall data, and data on carbon pools. The model is a version of CABLE (the Community Atmosphere-Biosphere-Land Exchange model), coupled with CASAcnp (a biogeochemical model) and SLI (Soil-Litter-Iso, a soil hydrology model including liquid and vapour water fluxes and the effects of litter). By projecting observation-prediction residuals onto model uncertainty, we find that eddy flux measurements provide a significantly tighter constraint on Australian continental net primary production (NPP) than the other data types. However, simultaneous constraint by multiple data types is important for mitigating bias from any single type. Results emerging from the multiply-constrained model are as follows (with all values applying over 1990-2011 and all ranges denoting ±1 standard error): (1) on the Australian continent, a predominantly semi-arid region, over half (0.64±0.05) of the water loss through ET occurs through soil evaporation and bypasses plants entirely; (2) mean Australian NPP is 2200±400 TgC/y, making the NPP/precipitation ratio about the same for Australia as the global land average; (3) annually cyclic ("grassy") vegetation and persistent ("woody") vegetation respectively account for 0.56±0.14 and 0.43±0.14 of NPP across Australia; (4) the average interannual variability of Australia's NEP (±180 TgC/y) is larger than Australia's total anthropogenic greenhouse gas emissions in 2011 (149 TgCeq/y), and is dominated by variability in desert and savannah regions. The mean carbon budget over 1990-2011 reveals that climate variability and rising CO2 respectively contributed 12±29 and 68±35 TgC/y to Net Biosphere Productivity (NBP, positive to land). However these terrestrial carbon gains were partially offset by fire and land use change (mainly clearing of woody savannah), which caused net losses of 31±5 TgC/y and 18±7 TgC/y respectively. The resultant overall NBP of 31±35 TgC/y offset fossil fuel emissions (95±6 TgC/y) by 32±36%. However, territorial fossil fuel emissions are increasingly being dwarfed by fossil fuel exports: in 2009-2010, Australia exported 2.5 times more carbon in fossil fuels than it emitted by burning fossil fuels for domestic use.

Raupach, M. R.; Haverd, V.; Briggs, P. R.; Canadell, J.; Davis, S. J.; Isaac, P. R.; Law, R.; Meyer, M.; Peters, G. P.; Pickett Heaps, C.; Roxburgh, S. H.; Sherman, B.; van Gorsel, E.; Viscarra Rossel, R.; Wang, Z.

2012-12-01

345

In vitro antimicrobial activity of Medilox® super-oxidized water  

PubMed Central

Aim Super-oxidized water is one of the broad spectrum disinfectants, which was introduced recently. There are many researches to find reliable chemicals which are effective, inexpensive, easy to obtain and use, and effective for disinfection of microorganisms leading hospital infections. Antimicrobial activity of super-oxidized water is promising. The aim of this study was to investigate the in-vitro antimicrobial activity of different concentrations of Medilox® super-oxidized water that is approved by the Food and Drug Administration (FDA) as high level disinfectant. Material and methods In this study, super-oxidized water obtained from Medilox® [Soosan E & C, Korea] device, which had been already installed in our hospital, was used. Antimicrobial activities of different concentrations of super-oxidized water (1/1, 1/2, 1/5, 1/10, 1/20, 1/50, 1/100) at different exposure times (1, 2, 5, 10, 30 min) against six ATCC strains, eight antibiotic resistant bacteria, yeasts and molds were evaluated using qualitative suspension test. Dey-Engley Neutralizing Broth [Sigma-Aldrich, USA] was used as neutralizing agent. Results Medilox® was found to be effective against all standard strains (Acinetobacter baumannii 19606, Escherichia coli 25922, Enterococcus faecalis 29212, Klebsiella pneumoniae 254988, Pseudomonas aeruginosa 27853, Staphylococcus aureus 29213), all clinical isolates (Acinetobacter baumannii, Escherichia coli, vancomycin-resistant Enterococcus faecium, Klebsiella pneumoniae, Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, Bacillus subtilis, Myroides spp.), and all yeastsat 1/1 dilution in ??1 minute. It was found to be effective on Aspergillus flavus at 1/1 dilution in ??2 minutes and on certain molds in ??5 minutes. Conclusion Medilox® super-oxidized water is a broad spectrum, on-site producible disinfectant, which is effective on bacteria and fungi and can be used for the control of nosocomial infection. PMID:25023905

2014-01-01

346

Oxidation and Volatilization of Silica-Formers in Water Vapor  

NASA Technical Reports Server (NTRS)

At high temperatures SiC and Si3N4 react with water vapor to form a silica scale. Silica scales also react with water vapor to form a volatile Si(OH)4 species. These simultaneous reactions, one forming silica and the other removing silica, are described by paralinear kinetics. A steady state, in which these reactions occur at the same rate, is eventually achieved, After steady state is achieved, the oxide found on the surface is a constant thickness and recession of the underlying material occurs at a linear rate. The steady state oxide thickness, the time to achieve steady state, and the steady state recession rate can all be described in terms of the rate constants for the oxidation and volatilization reactions. In addition, the oxide thickness, the time to achieve steady state, and the recession rate can also be determined from parameters that describe a water vapor-containing environment. Accordingly, maps have been developed to show these steady state conditions as a function of reaction rate constants, pressure, and gas velocity. These maps can be used to predict the behavior of silica formers in water-vapor containing environments such as combustion environments. Finally, these maps are used to explore the limits of the paralinear oxidation model for SiC and Si3N4

Opila, E. J.; Gray, Hugh R. (Technical Monitor)

2002-01-01

347

Emerging contaminants of public health significance as water quality indicator compounds in the urban water cycle.  

PubMed

The contamination of the urban water cycle (UWC) with a wide array of emerging organic compounds (EOCs) increases with urbanization and population density. To produce drinking water from the UWC requires close examination of their sources, occurrence, pathways, and health effects and the efficacy of wastewater treatment and natural attenuation processes that may occur in surface water bodies and groundwater. This paper researches in details the structure of the UWC and investigates the routes by which the water cycle is increasingly contaminated with compounds generated from various anthropogenic activities. Along with a thorough survey of chemicals representing compound classes such as hormones, antibiotics, surfactants, endocrine disruptors, human and veterinary pharmaceuticals, X-ray contrast media, pesticides and metabolites, disinfection-by-products, algal toxins and taste-and-odor compounds, this paper provides a comprehensive and holistic review of the occurrence, fate, transport and potential health impact of the emerging organic contaminants of the UWC. This study also illustrates the widespread distribution of the emerging organic contaminants in the different aortas of the ecosystem and focuses on future research needs. PMID:24972248

Pal, Amrita; He, Yiliang; Jekel, Martin; Reinhard, Martin; Gin, Karina Yew-Hoong

2014-10-01

348

Uncovering structure-activity relationships in manganese-oxide-based heterogeneous catalysts for efficient water oxidation.  

PubMed

Artificial photosynthesis by harvesting solar light into chemical energy could solve the problems of energy conversion and storage in a sustainable way. In nature, CO2 and H2 O are transformed into carbohydrates by photosynthesis to store the solar energy in chemical bonds and water is oxidized to O2 in the oxygen-evolving center (OEC) of photosystem II (PS II). The OEC contains CaMn4 O5 cluster in which the metals are interconnected through oxido bridges. Inspired by biological systems, manganese-oxide-based catalysts have been synthesized and explored for water oxidation. Structural, functional modeling, and design of the materials have prevailed over the years to achieve an effective and stable catalyst system for water oxidation. Structural flexibility with eg (1) configuration of Mn(III) , mixed valency in manganese, and higher surface area are the main requirements to attain higher efficiency. This Minireview discusses the most recent progress in heterogeneous manganese-oxide-based catalysts for efficient chemical, photochemical, and electrochemical water oxidation as well as the structural requirements for the catalyst to perform actively. PMID:25641823

Indra, Arindam; Menezes, Prashanth W; Driess, Matthias

2015-03-01

349

The diel cycle of water vapor in west Greenland  

NASA Astrophysics Data System (ADS)

We present a study of the dynamics of small-scale (~100 km) atmospheric circulation in west Greenland which is dominated by interactions of marine and continental air masses. Water vapor concentration and isotopic ratios measured continuously over a 25 day period in Kangerlussuaq, Greenland were used to monitor the convergence of easterly katabatic winds and westerly sea breezes that form a front between the dry, isotopically depleted, glacial air mass and the moist, isotopically enriched, marine air mass. During the latter 16 days of the measurement period, an interval with no large-scale synoptic interference, the inland penetration of the sea breeze controlled the largest day-to-day humidity and vapor isotopic variations. Kangerlussuaq experienced sea breezes in the afternoon on 9 days, consistent with the long-term average of such occurrences on 56% of days in July and August. The inland position of the sea breeze front is controlled by the katabatic wind strength, which is stronger during times of reduced cloud coverage and/or higher-pressure gradient between the coast and the Greenland ice sheet. The position and movement of the front will likely respond to changes in the general atmospheric circulation and regional radiation balance resulting from global warming, which will, in turn, impact the local hydrological cycle and ecosystem processes.

Kopec, B. G.; Lauder, A. M.; Posmentier, E. S.; Feng, X.

2014-08-01

350

Caffeinated nitric oxide-releasing lozenge improves cycling time trial performance.  

PubMed

Boosting nitric oxide production during exercise by various means has been found to improve exercise performance. We investigated the effects of a nitric oxide releasing lozenge with added caffeine (70?mg) on oxygen consumption during steady-state exercise and cycling time trial performance using a double-blinded randomized, crossover experimental design. 15 moderately trained cyclists (7 females and 8 males) were randomly assigned to ingest the caffeinated nitric oxide lozenge or placebo 5?min before exercise. Oxygen consumption and blood lactate were assessed at rest and at 50%, 65% and 75% maximal oxygen consumption. Exercise performance was assessed by time to complete a simulated 20.15?km cycling time-trial course. No significant treatment effects for oxygen consumption or blood lactate at rest or during steady-state exercise were observed. However, time-trial performance was improved by 2.1% (p<0.01) when participants consumed the nitric oxide lozenge (2,424±69?s) compared to placebo (2,476±78?s) and without a significant difference in rating of perceived exertion. These results suggest that acute supplementation with a caffeinated nitric oxide releasing lozenge may be a practical and effective means of improving aerobic exercise performance. PMID:25285468

Lee, J; Kim, H T; Solares, G J; Kim, K; Ding, Z; Ivy, J L

2015-02-01

351

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part I to assess the role of forested areas in the global carbon cycle and in the continental water balance. During with a carbon allocation model and coupled with a soil model. CASTANEA describes canopy photosynthesis

Boyer, Edmond

352

Ecological Modelling xxx (2005) xxxxxx Modelling carbon and water cycles in a beech forest  

E-print Network

Ecological Modelling xxx (2005) xxx­xxx Modelling carbon and water cycles in a beech forest Part II A forest ecosystem model (CASTANEA) simulating the carbon balance (canopy photosynthesis, autotrophic and heterotrophic respirations, net ecosystem exchange, wood and root growth) and the water cycle (transpiration

Boyer, Edmond

353

Perceptions of the Water Cycle among Primary School Children in Botswana.  

ERIC Educational Resources Information Center

Describes qualitative and quantitative methods used to elucidate the nature of the perception of the water cycle held by Botswana primary-grade pupils in three different geographic areas. Concludes that the students' perception of the water cycle was positively influenced by schooling but negatively impacted upon, to some extent, by the untutored…

Taiwo, A. A.; Motswiri, M. J.; Masene, R.

1999-01-01

354

Ecological controls on water-cycle response to climate variability in deserts  

Microsoft Academic Search

The impact of climate variability on the water cycle in desert ecosystems is controlled by biospheric feedback at interannual to millennial timescales. This paper describes a unique field dataset from weighing lysimeters beneath nonvegetated and vegetated systems that unequivocally demonstrates the role of vegetation dynamics in controlling water cycle response to interannual climate variability related to El Niño southern oscillation

B. R. Scanlon; D. G. Levitt; R. C. Reedy; K. E. Keese; M. J. Sully

2005-01-01

355

Impact of ocean acidification on benthic and water column ammonia oxidation  

NASA Astrophysics Data System (ADS)

Ammonia oxidation is a key microbial process within the marine N-cycle. Sediment and water column samples from two contrasting sites in the English Channel (mud and sand) were incubated (up to 14 weeks) in CO2-acidified seawater ranging from pH 8.0 to pH 6.1. Additional observations were made off the island of Ischia (Mediterranean Sea), a natural analogue site, where long-term thermogenic CO2 ebullition occurs (from pH 8.2 to pH 7.6). Water column ammonia oxidation rates in English Channel samples decreased under low pH with near-complete inhibition at pH 6.5. Water column Ischia samples showed a similar though not statistically significant trend. However, sediment ammonia oxidation rates at all three locations were not affected by reduced pH. These observations may be explained by buffering within sediments or low-pH adaptation of the microbial ammonia oxidizing communities. Our observations have implications for modeling the future impact of ocean acidification on marine ecosystems.

Kitidis, Vassilis; Laverock, Bonnie; McNeill, Louise C.; Beesley, Amanda; Cummings, Denise; Tait, Karen; Osborn, Mark A.; Widdicombe, Stephen

2011-11-01

356

The Mars water cycle at other epochs: History of the polar caps and layered terrain  

NASA Technical Reports Server (NTRS)

The atmospheric water cycle at the present epoch involves summertime sublimation of water from the north polar cap, transport of water through the atmosphere, and condensation on one or both winter CO2 caps. Exchange with the regolith is important seasonally, but the water content of the atmosphere appears to be controlled by the polar caps. The net annual transport through the atmosphere, integrated over long timescales, must be the driving force behind the long-term evolution of the polar caps; clearly, this feeds back into the evolution of the layered terrain. We have investigated the behavior of the seasonal water cycle and the net integrated behavior at the pole for the last 10 exp 7 years. Our model of the water cycle includes the solar input, CO2 condensation and sublimation, and summertime water sublimation through the seasonal cycles, and incorporates the long-term variations in the orbital elements describing the Martian orbit.

Jakosky, Bruce M.; Henderson, Bradley G.; Mellon, Michael T.

1992-01-01

357

The Effects of Radiatively Active Water Ice Clouds on the Martian Global Seasonal Water Cycle  

NASA Astrophysics Data System (ADS)

Recently, Mars General Circulation Models (MGCM) have begun implementing cloud microphysics packages to better account for their role in the water cycle. Here, we discuss the importance of their radiative effects. For the past several years we have been implementing and testing a state-of-the-art cloud microphysics package into the NASA/Ames MGCM. This package accounts for the nucleation, growth, transport, and settling of a size distribution water ice cloud particles in a self-consistent fashion. The model also has flags to activate their solar and infrared radiative effects, which depend on the size and dust content of the ice particles. We have performed two simulations of the global water cycle on Mars: one in which the clouds are radiatively inert, and one in which they are radiatively active. We find that the thermal structure of the atmosphere in the radiatively active cloud run compares better with MGS TES and MRO MCS data. However, the water cycle dries out considerably with radiatively active clouds. There are several reasons for this but the main reason appears to be related to a cooling of the North Polar Residual Cap (NPRC) in the model that is brought about by the reflective nature of the clouds that develop in the lower atmosphere immediately above the NPRC. These clouds increase the planetary albedo at these latitudes and reduce the solar flux at the surface, which is not sufficiently compensated for by an increase in downward infrared emission. Our conclusion at this point, based upon comparison with MRO MCS and MARCI data, is that the model is overpredicting the cloud fields in the vicinity of the NPRC.

Haberle, Robert M.; Montmessin, F.; Kahre, M. A.; Hollingsworth, J. L.; Schaeffer, J.; de Brouchoven de Bergeyck, A.; Wilson, J.

2010-10-01

358

Enhancing catalytic activity by narrowing local energy gaps-x-ray studies of a manganese water oxidation catalyst.  

PubMed

Changes in the local electronic structure of the Mn?3d orbitals of a Mn catalyst derived from a dinuclear Mn(III) complex during the water oxidation cycle were investigated ex?situ by X-ray absorption spectroscopy (XAS) and resonant inelastic X-ray scattering (RIXS) analyses. Detailed information about the Mn?3d orbitals, especially the local HOMO-LUMO gap on Mn sites revealed by RIXS analyses, indicated that the enhancement in catalytic activity (water oxidation) originated from the narrowing of the local HOMO-LUMO gap when electrical voltage and visible light illumination were applied simultaneously to the Mn catalytic system. PMID:25605663

Xiao, Jie; Khan, Munirah; Singh, Archana; Suljoti, Edlira; Spiccia, Leone; Aziz, Emad F

2015-03-01

359

Improvement of chemical control in the water-steam cycle of thermal power plants  

Microsoft Academic Search

A more effective chemical control in the water-steam cycle (WSC) of thermal power plants (TPP) is proposed in this paper. Minimization of corrosion effects by the production of ultra pure water and its strict control is the basis of all the investigated processes. The research involved the analysis of water samples in the WSC through key water quality parameters and

Vladana N. Rajakovi?-Ognjanovi?; Dragana Z. Živojinovic; Branimir N. Grgur; Ljubinka V. Rajakovi?

2011-01-01

360

Mercury cycling between the water column and surface sediments in a contaminated area  

Microsoft Academic Search

Mercury cycling in the water column and upper sediments of a contaminated area, the Largo do Laranjo, Aveiro (Portugal), was evaluated after determination of reactive and non-reactive mercury concentrations in the water column and pore waters of sediments, collected in several places of this bay. In the water column, reactive mercury concentrations varied between 10 and 37pmoldm?3, the highest values

Elsa Ramalhosa; Susana Río Segade; Eduarda Pereira; Carlos Vale; Armando Duarte

2006-01-01

361

Pulsed-laser deposition of nanostructured iron oxide catalysts for efficient water oxidation.  

PubMed

Amorphous iron oxide nanoparticles were synthesized by pulsed-laser deposition (PLD) for functionalization of indium-tin oxide surfaces, resulting in electrodes capable of efficient catalysis in water oxidation. These electrodes, based on earth-abundant and nonhazardous iron metal, are able to sustain high current densities (up to 20 mA/cm2) at reasonably low applied potential (1.64 V at pH 11.8 vs reversible hydrogen electrode) for more than 1 h when employed as anodes for electrochemical water oxidation. The good catalytic performance proves the validity of PLD as a method to prepare nanostructured solid-state materials for catalysis, enabling control over critical properties such as surface coverage and morphology. PMID:24742340

Orlandi, Michele; Caramori, Stefano; Ronconi, Federico; Bignozzi, Carlo A; El Koura, Zakaria; Bazzanella, Nicola; Meda, Laura; Miotello, Antonio

2014-05-14

362

Visible light water splitting using dye-sensitized oxide semiconductors.  

PubMed

Researchers are intensively investigating photochemical water splitting as a means of converting solar to chemical energy in the form of fuels. Hydrogen is a key solar fuel because it can be used directly in combustion engines or fuel cells, or combined catalytically with CO(2) to make carbon containing fuels. Different approaches to solar water splitting include semiconductor particles as photocatalysts and photoelectrodes, molecular donor-acceptor systems linked to catalysts for hydrogen and oxygen evolution, and photovoltaic cells coupled directly or indirectly to electrocatalysts. Despite several decades of research, solar hydrogen generation is efficient only in systems that use expensive photovoltaic cells to power water electrolysis. Direct photocatalytic water splitting is a challenging problem because the reaction is thermodynamically uphill. Light absorption results in the formation of energetic charge-separated states in both molecular donor-acceptor systems and semiconductor particles. Unfortunately, energetically favorable charge recombination reactions tend to be much faster than the slow multielectron processes of water oxidation and reduction. Consequently, visible light water splitting has only recently been achieved in semiconductor-based photocatalytic systems and remains an inefficient process. This Account describes our approach to two problems in solar water splitting: the organization of molecules into assemblies that promote long-lived charge separation, and catalysis of the electrolysis reactions, in particular the four-electron oxidation of water. The building blocks of our artificial photosynthetic systems are wide band gap semiconductor particles, photosensitizer and electron relay molecules, and nanoparticle catalysts. We intercalate layered metal oxide semiconductors with metal nanoparticles. These intercalation compounds, when sensitized with [Ru(bpy)(3)](2+) derivatives, catalyze the photoproduction of hydrogen from sacrificial electron donors (EDTA(2-)) or non-sacrificial donors (I(-)). Through exfoliation of layered metal oxide semiconductors, we construct multilayer electron donor-acceptor thin films or sensitized colloids in which individual nanosheets mediate light-driven electron transfer reactions. When sensitizer molecules are "wired" to IrO(2).nH(2)O nanoparticles, a dye-sensitized TiO(2) electrode becomes the photoanode of a water-splitting photoelectrochemical cell. Although this system is an interesting proof-of-concept, the performance of these cells is still poor (approximately 1% quantum yield) and the dye photodegrades rapidly. We can understand the quantum efficiency and degradation in terms of competing kinetic pathways for water oxidation, back electron transfer, and decomposition of the oxidized dye molecules. Laser flash photolysis experiments allow us to measure these competing rates and, in principle, to improve the performance of the cell by changing the architecture of the electron transfer chain. PMID:19905000

Youngblood, W Justin; Lee, Seung-Hyun Anna; Maeda, Kazuhiko; Mallouk, Thomas E

2009-12-21

363

Potential Seasonal Predictability of the Global Water Cycle  

NASA Astrophysics Data System (ADS)

The potential predictability of seasonal means of water cycle components, specifically precipitation and evaporation, are estimated using recently developed methods based on Analysis of Covariance (ANOCOVA) and the bootstrap, and the previous methods proposed by Katz (KZ), Shukla-Gutzler (SG) and Madden (MN). The ANOCOVA method has the advantage of not only taking into account autocorrelation structure in the daily time series but also accounting for the uncertainty of the estimated parameters in the significance test. This method tests whether interannual variability of seasonal means exceeds that due to weather noise under the null hypothesis that seasonal means are identical every year. The second method is based on the bootstrap technique that makes few assumptions about physical process, model structure and underlying distribution. The essence of the bootstrap is to randomly resample the daily time series to build up an empirical distribution of the variance of seasonal means under the null hypothesis that seasonal mean is independent of year. The predictability of the observed precipitation estimated by ANOCOVA, the bootstrap and KZ reveals similar spatial distribution patterns: large fraction of predictable variance (FPV) in tropics and low FPV over extatropics where interannual variability is not significantly distinguished from the weather noise. There are more regions identified potentially predictable in December-January-February (DJF) and March-April-May (MAM) than in June-July-August (JJA) and September-October-November (SON). The ANOCOVA method exhibits the highest predictability of the three methods and is close to the bootstrap, while KZ shows the smallest FPV due to the dominance of noise. Seasonal evaporation over global land from ANOCOVA, bootstrap, SG and MN indicates that high predictability occurs predominately over tropical and southern mid-latitude land areas, and modest predictability occurs over North America and Europe. The potential predictability of evaporation also exhibits a prominent seasonal cycle with JJA and SON having the most predictable area. The bootstrap suggests that 58% of land is potentially predictable, the largest predictable area of the four methods. The ANOCOVA method also has larger FPV than SG and MN, while it generally produces estimates similar to those of the bootstrap. The predictable area suggested by MN barely exceeds 30% of the globe, the smallest area of predictable estimated among all the four methods.

Feng, X.; DelSole, T. M.; Houser, P. R.

2011-12-01

364

TRMM and Its Connection to the Global Water Cycle  

NASA Technical Reports Server (NTRS)

The importance of quantitative knowledge of tropical rainfall, its associated latent heating and variability is summarized in the context of the global hydrologic cycle. Much of the tropics is covered by oceans. What land exists, is covered largely by rainforests that are only thinly populated. The only way to adequately measure the global tropical rainfall for climate and general circulation models is from space. The TRMM orbit is inclined 35 degrees leading to good sampling in the tropics and a rapid precession to study the diurnal cycle of precipitation. The precipitation instrument complement consists of the first rain radar to be flown in space (PR), a multi-channel passive microwave sensor (TMI) and a five-channel VIS/IR (VIRS) sensor. The precipitation radar operates at a frequency of 13.6 GHz. The swath width is 220 km, with a horizontal resolution of 4 km and the vertical resolution of 250 m. The minimum detectable signal from the precipitation radar has been measured at 17 dBZ. The TMI instrument is designed similar to the SSM/I with two important changes. The 22.235 GHz water vapor absorption channel of the SSM/I was moved to 21.3 GHz in order to avoid saturation in the tropics and 10.7 GHz V&H polarized channels were added to expand the dynamic range of rainfall estimates. The resolution of the TMI varies from 4.6 km at 85 GHz to 36 km at 10.7 GHz. The visible and infrared sensor (VIRS) measures radiation at 0.63, 1.6, 3.75, 10.8 and 12.0 microns. The spatial resolution of all five VIRS channels is 2 km at nadir. In addition to the three primary rainfall instruments, TRMM will also carry a Lightning Imaging Sensor (LIS) and a Clouds and the Earth's Radiant Energy System (CERES) instrument. This presentation will focus primarily on the advances in our understanding of tropical rain systems needed to interpret the TRMM data. Global averages, as well as case studies from TRMM radar (PR), the TRMM Microwave Imager (TMI) and Visible and Infrared Sensor (VIRS) will be presented. Comparisons and contrasts among the different sensors will be drawn. Results will also be compared to previous rainfall climatologies generated from the SSM/I instrument. In particular this paper will focus on the synergy between the TRMM radar and passive microwave radiometer and what we have learned from is synergy.

Kummerow, Chiristian

1999-01-01

365

TRMM and its Connection to the Global Water Cycle  

NASA Technical Reports Server (NTRS)

The importance of quantitative knowledge of tropical rainfall, its associated latent heating and variability is summarized in the context of the global hydrologic cycle. Much of the tropics is covered by oceans. What land exists, is covered largely by rainforests that are only thinly populated. The only way to adequately measure the global tropical rainfall for climate and general circulation models is from space. The Tropical Rainfall Measuring Mission (TRMM) orbit is inclined 35 degrees leading to good sampling in the tropics and a rapid precession to study the diurnal cycle of precipitation. The precipitation instrument complement consists of the first rain radar to be flown in space (PR), a multi-channel passive microwave sensor (TMI) and a five-channel VIS/IR (VIRS) sensor. The precipitation radar operates at a frequency of 13.6 GHz. The swath width is 220 km, with a horizontal resolution of 4 km and the vertical resolution of 250 m. The minimum detectable signal from the precipitation radar has been measured at - 17 dBZ. The TMI instrument is designed similar to the SSM/I with two important changes. The 22.235 GHz water vapor absorption channel of the SSM/I was moved to 21.3 GHz in order to avoid saturation in the tropics and 10.7 GHz V&H polarized channels were added to expand the dynamic range of rainfall estimates. The resolution of the TMI varies from 4.6 km at 85 GHz to 36 km at 10.7 GHz. The visible and infrared sensor (VIRS) measures radiation at 0.63, 1.6, 3.75, 10.8 and 12.0 microns. The spatial resolution of all five VIRS channels is 2 km at nadir. In addition to the three primary rainfall instruments, TRMM will also carry a Lightning Imaging Sensor (LIS) and a Clouds and the Earth's Radiant Energy System (CERES) instrument. This presentation will focus primarily on the advances in our understanding of tropical rain systems needed to interpret the TRMM data. Global averages, as well as case studies from TRMM radar (PR), the TRMM Microwave Imager (TMI) and Visible and Infrared Sensor (VIRS) will be presented. Comparisons and contrasts among the different sensors will be drawn. Results will also be compared to previous rainfall climatologies generated from the SSM/I instrument. In particular this paper will focus on the synergy between the TRMM radar and passive microwave radiometer and what we have learned from its synergy.

Kummerow, Christian; Hong, Ye

1999-01-01

366

Water oxidation catalysis by birnessite@iron oxide core-shell nanocomposites.  

PubMed

In this work, magnetic nanocomposite particles were prepared for water oxidation reactions. The studied catalysts consist of maghemite (?-Fe2O3), magnetite (Fe3O4), and manganese ferrite (MnFe2O4) nanoparticles as cores coated in situ with birnessite-type manganese oxide shells and were characterized by X-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermal, chemical, and surface analyses, and magnetic measurements. The particles were found to be of nearly spherical core-shell architectures with average diameter of 150 nm. Water oxidation catalysis was examined using Ce(4+) as the sacrificial oxidant. All core-shell particles were found to be active water oxidation catalysts. However, the activity was found to depend on a variety of factors like the type of iron oxide core, the structure and composition of the shell, the coating characteristics, and the surface properties. Catalysts containing magnetite and manganese ferrite as core materials displayed higher catalytic activities per manganese ion (2650 or 3150 mmolO2 molMn(-1) h(-1)) or per mass than nanoiron oxides (no activity) or birnessite alone (1850 mmolO2 molMn(-1) h(-1)). This indicates synergistic effects between the MnOx shell and the FeOx core of the composites and proves the potential of the presented core-shell approach for further catalyst optimization. Additionally, the FeOx cores of the particles allow magnetic recovery of the catalyst and might also be beneficial for applications in water-oxidizing anodes because the incorporation of iron might enhance the overall conductivity of the material. PMID:25710557

Elmaci, Gökhan; Frey, Carolin E; Kurz, Philipp; Zümreo?lu-Karan, Birgül

2015-03-16

367

Photocatalytic water oxidation by Nafion-stabilized iridium oxide colloids Michikazu Hara and Thomas E. Mallouk*  

E-print Network

Photocatalytic water oxidation by Nafion-stabilized iridium oxide colloids Michikazu Hara IrO2·xH2O stabilized by soluble Nafion, tris(2,2A-bipyridyl)ruthenium(II), and persulfate efficiently conventional catalysts. In this paper, we report O2 evolution from a [Ru(bpy)3]2+­Nafion- stabilized IrO2·xH2O

368

Metal Oxide Photoanodes for Water Splitting  

Microsoft Academic Search

\\u000a Solar hydrogen production through photocatalytically assisted water splitting has attracted a great deal of attention since\\u000a its first discovery almost 30 years ago. The publication of investigations into the use of TiO2 photoanodes has continued apace since and a critical review of current trends is reported herein. Recent advances in the\\u000a understanding of the behaviour of nanoparticulate TiO2 films is summarized

J. Augusty?ski; B. Alexander; R. Solarska

369

Oxidation of Carbon Fibers in Water Vapor Studied  

NASA Technical Reports Server (NTRS)

T-300 carbon fibers (BP Amoco Chemicals, Greenville, SC) are a common reinforcement for silicon carbide composite materials, and carbon-fiber-reinforced silicon carbide composites (C/SiC) are proposed for use in space propulsion applications. It has been shown that the time to failure for C/SiC in stressed oxidation tests is directly correlated with the fiber oxidation rate (ref. 1). To date, most of the testing of these fibers and composites has been conducted in oxygen or air environments; however, many components for space propulsion, such as turbopumps, combustors, and thrusters, are expected to operate in hydrogen and water vapor (H2/H2O) environments with very low oxygen contents. The oxidation rate of carbon fibers in conditions representative of space propulsion environments is, therefore, critical for predicting component lifetimes for real applications. This report describes experimental results that demonstrate that, under some conditions, lower oxidation rates of carbon fibers are observed in water vapor and H2/H2O environments than are found in oxygen or air. At the NASA Glenn Research Center, the weight loss of the fibers was studied as a function of water pressure, temperature, and gas velocity. The rate of carbon fiber oxidation was determined, and the reaction mechanism was identified.

Opila, Elizabeth J.

2003-01-01

370

Global Climate Modeling of the Martian water cycle with improved microphysics and radiatively active water ice clouds  

E-print Network

Radiative effects of water ice clouds have noteworthy consequences on the Martian atmosphere, its thermal structure and circulation. Accordingly, the inclusion of such effects in the LMD Mars Global Climate Model (GCM) greatly modifies the simulated Martian water cycle. The intent of this paper is to address the impact of radiatively active clouds on atmospheric water vapor and ice in the GCM and improve its representation. We propose a new enhanced modeling of the water cycle, consisting of detailed cloud microphysics with dynamic condensation nuclei and a better implementation of perennial surface water ice. This physical modeling is based on tunable parameters. This new version of the GCM is compared to the Thermal Emission Spectrometer observations of the water cycle. Satisfying results are reached for both vapor and cloud opacities. However, simulations yield a lack of water vapor in the tropics after Ls=180{\\deg} which is persistent in simulations compared to observations, as a consequence of aphelion c...

Navarro, Thomas; Forget, François; Spiga, Aymeric; Millour, Ehouarn; Montmessin, Franck

2013-01-01

371

How surface potential determines the kinetics of the first hole transfer of photocatalytic water oxidation.  

PubMed

Interfacial hole transfer between n-SrTiO3 and OH(-) was investigated by surface sensitive transient optical spectroscopy of an in situ photoelectrochemical cell during water oxidation. The kinetics reveal a single rate constant with an exponential dependence on the surface hole potential, spanning time scales from 3 ns to 8 ps over a ?1 V increase. A voltage- and laser illumination-induced process moves the valence band edge at the n-type semiconductor/water interface to continuously change the surface hole potential. This single step of the water oxidation reaction is assigned to the first hole transfer h(+) + OH(-) ? OH(•). The kinetics quantify how much a change in the free energy difference driving this first hole transfer reduces the activation barrier. They are also used to extrapolate the kinetic rate due to the activation barrier when that free energy difference is zero, or the Nernstian potential. This is the first time transient spectroscopy has enabled the separation of the first hole transfer from the full four hole transfer cycle and a direct determination of these two quantities. The Nernstian potential for OH(-)/OH(•) is also suggested, in rough agreement with gas-phase studies. The observation of a distinct, much longer time scale upon picosecond hole transfer to OH(-) suggests that a dominant, more stable intermediate of the water oxidation reaction, possibly a surface bound oxo, may result. PMID:25029360

Waegele, Matthias M; Chen, Xihan; Herlihy, David M; Cuk, Tanja

2014-07-30

372

Development of Bioinspired Mn4O4-Cubane Water Oxidation Catalysts: Lessons from Photosynthesis  

E-print Network

efficient system that uses solar energy to oxidize water is the photosystem II water-oxidizing complex (PSII-activated electrolysis of water. The [Mn4O4]6+ cubane core assembles spontaneously in solution from monomeric precursorsDevelopment of Bioinspired Mn4O4-Cubane Water Oxidation Catalysts: Lessons from Photosynthesis G

Lawson, Catherine L.

373

Kinetics of acetic acid oxidation in supercritical water  

SciTech Connect

Acetic acid was oxidized in supercritical water in batch microreactors at temperatures between 380 and 440[degrees]C. The acetic acid concentrations ranged from 1.0 [times] 10[sup [minus]4] to 5.2 [times] 10[sup [minus]3] M, the oxygen concentrations ranged from 5.7 [times] 10[sup [minus]3] to 7.1 [times] 10[sup [minus]2] M, and the water density ranged from 6.7 to 25 M. Oxygen was always present in at least 3.5 times the stoichiometric amount required for complete oxidation. Analysis of the kinetics data showed that the global oxidation rate law was first order in acetic acid, 0.6 order in oxygen, and second order in water. The global rate constant has a pre-exponential factor of 10[sup 19.8] M[sup [minus]26] S[sup [minus]1] and an activation energy of 73.6 kcal/mol. This rate law also satisfactorily describes other sets of experimental data in the literature for the oxidation of acetic acid in supercritical water. 19 refs., 5 figs., 3 tabs.

Savage, P.E.; Smith, M.A. (Univ. of Michigan, Ann Arbor, MI (United States))

1995-01-01

374

Water vapor detection with individual tin oxide nanowires  

Microsoft Academic Search

Individual tin oxide nanowires (NWs), contacted to platinum electrodes using focused ion beam assisted nanolithography, were used for detecting water vapor (1500-32 000 ppm) in different gaseous environments. Responses obtained in synthetic air (SA) and nitrogen atmospheres suggested differences in the sensing mechanism, which were related to changes in surface density of the adsorbed oxygen species in the two cases.

F. Hernandez-Ramirez; S. Barth; A. Tarancon; O. Casals; E. Pellicer; J. Rodriguez; A. Romano-Rodriguez; J. R. Morante; S. Mathur

2007-01-01

375

Electrophotolysis oxidation system for measurement of organic concentration in water  

NASA Technical Reports Server (NTRS)

Methods and apparatus for determining organic carbon in aqueous solution are described. The method comprises subjecting the aqueous solution to electrolysis, for generating oxygen from water, and simultaneously to ultraviolet radiation, for oxidation of substantially all organic carbon to carbon dioxide. The carbon dioxide is measured and the value is related to the concentration of organic carbon in the aqueous solution.

Winkler, H. E. (inventor)

1981-01-01

376

Nickel oxide water electrolysis diaphragm fabricated by a novel method  

Microsoft Academic Search

We have been studying small-scale, dispersed hydrogen production by water electrolysis by using renewable energy such as solar light. In order to fabricate the compact nickel oxide diaphragms used in such system, a novel method was devised where Ni deposition was applied in combination with a masking process. The method has the merits of being controllable in thickness and porous

Takashi Ohmori; Kenjiro Tachikawa; Katsuyuki Tsuji; Katsuhiro Anzai

2007-01-01

377

Cobalt porphyrin electrode films for electrocatalytic water oxidation.  

PubMed

Catalysts play very important roles in artificial photosynthesis for solar energy conversion. In this present study, two water-insoluble cobalt porphyrin complexes, cobalt(II) meso-tetraphenylporphyrin (CoP-1) and cobalt(II) 5,10,15,20-tetrakis-(4-bromophenyl)porphyrin (CoP-2), were synthesized and coated as thin films on the FTO working electrode. The films showed good activities for electrocatalytic water oxidation in aqueous solutions at pH 9.2. The Faradaic efficiencies of both films approached to ~100%, measured using a fluorescence-based oxygen sensor. The turnover frequencies were close to 0.50 s(?1) and 0.40 s(?1) for CoP-1 and CoP-2, respectively, under an applied anodic potential of 1.3 V (vs. Ag/AgCl) at pH 9.2. Importantly, no cobalt oxide particles were observed on the working electrode after catalysis. The stability of the catalyst films was further evaluated by UV-vis spectroscopy, inhibition measurements, mass spectrometry, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The pH dependence of water oxidation on CoP-1 and CoP-2 suggested a proton-coupled electron transfer (PCET) mechanism. The catalyst films could be recycled and showed almost unchanged catalytic activities when they were reused in new electrocatalytic studies of water oxidation. PMID:24777036

Han, Ali; Jia, Hongxing; Ma, Hao; Ye, Shifan; Wu, Haotian; Lei, Haitao; Han, Yongzhen; Cao, Rui; Du, Pingwu

2014-06-21

378

A Study of Junior High Students' Perceptions of the Water Cycle  

NSDL National Science Digital Library

This study explores junior high school students' perceptions of the water cycle. Data were collected from 1,000 7th and 9th grade students in Israel using a series of quantitative and qualitative research tools that were specifically developed for the study. The findings indicated that the students understood some of the processes involved, but most lacked the dynamic, cyclic, and systemic perceptions of the system. Moreover, they possessed an incomplete picture of the water cycle including many preconceptions and misconceptions about it. Most of the students were aware of the atmospheric part of the water cycle, but ignored its groundwater part. Moreover, those who included part of the underground system in the water cycle perceived the underground water as static, subsurface lakes which reflect the traditional teaching of the subject of water in the science curricula.

Orit Ben-zvi-Assarf

379

Seasonal variations of gene expression biomarkers in Mytilus galloprovincialis cultured populations: temperature, oxidative stress and reproductive cycle as major modulators.  

PubMed

The blue mussel Mytilus galloprovincialis has been used as monitoring organism in many biomonitoring programs because of its broad distribution in South European sea waters and its physiological characteristics. Different pollution-stress biomarkers, including gene expression biomarkers, have been developed to determine its physiological response to the presence of different pollutants. However, the existing information about basal expression profiles is very limited, as very few biomarker-based studies were designed to reflect the natural seasonal variations. In the present study, we analyzed the natural expression patterns of several genes commonly used in biomonitoring, namely ferritin, metallothionein, cytochrome P450, glutathione S-transferase, heat shock protein and the kinase responsive to stress KRS, during an annual life cycle. Analysis of mantle-gonad samples of cultured populations of M. galloprovincialis from the Delta del Ebro (North East Spain) showed natural seasonal variability of these biomarkers, pointing to temperature and oxidative stress as major abiotic modulators. In turn, the reproductive cycle, a process that can be tracked by VCLM7 expression, and known to be influenced by temperature, seems to be the major biotic factor involved in seasonality. Our results illustrate the influence of environmental factors in the physiology of mussels through their annual cycle, a crucial information for the correct interpretation of responses under stress conditions. PMID:25203829

Jarque, Sergio; Prats, Eva; Olivares, Alba; Casado, Marta; Ramón, Montserrat; Piña, Benjamin

2014-11-15

380

Study of nickel electrode oxidation as a function of 80% depth of discharge cycling  

SciTech Connect

Oxidation of nickel sinter used in nickel oxide electrodes in aerospace nickel cadmium cells leads to hydrogen gassing and the potential for cell rupture. The oxidation is directly related to loss of overcharge protection built into the cell during manufacturing. In nickel hydrogen cells, excessive oxidation of the nickel sinter can eventually lead to a burst before leak situation and is a potential source of failure. It is well known that nickel cadmium cells having nylon separators contribute to loss of overcharge via a hydrolysis reaction of the nylon in the potassium hydroxide electrolyte environment in the cell. The hydrolysis reaction produces lower chain organics which are oxidized by the positive electrode and oxygen. Oxidation of the organics diminishes the overcharge protection. With introduction of the Super NiCd{trademark} and the Magnum{trademark} nickel cadmium cells the nylon hydrolysis reaction is eliminated, but any reducing agent in the cell such as nickel or an organic additive can contribute to loss of overcharge protection. The present effort describes chemical analyses made to evaluate the extent of overcharge protection loss in nickel cadmium cells which do not have nylon hydrolysis, and quantifies the amount of hydrogen buildup in nickel hydrogen cells which are subjected to 80% depth of discharge cycling with and without the presence of cadmium in the positive electrode.

Pickett, D.F. Jr.; Scoles, D.L.; Johnson, Z.W.; Hayden, J.W.; Pennington, R.D. [Eagle-Picher Industries, Inc., Colorado Springs, CO (United States)

1997-12-31

381

Destruction of energetic materials by supercritical water oxidation  

SciTech Connect

Supercritical water oxidation is a relatively low-temperature process that can give high destruction efficiencies for a variety of hazardous chemical wastes. Results are presented examining the destruction of high explosives and propellants in supercritical water and the use of low temperature, low pressure hydrolysis as a pretreatment process. Reactions of cyclotrimethylene trinitramine (RDX), cyclotetramethylene tetranitramine (HMX), nitroguanidine (NQ), pentaerythritol tetranitrate (PETN), and 2,4,6-trinitrotoluene (TNT) are examined in a flow reactor operated at temperatures between 400{degrees}C and 650{degrees}C. Explosives are introduced into the reactor at concentrations below the solubility limits. For each of the compounds, over 99.9% is destroyed in less than 30 seconds at temperatures above 600{degrees}C. The reactions produce primarily N{sub 2}, N{sub 2}O,CO{sub 2}, and some nitrate and nitrite ions. The distribution of reaction products depends on reactor pressure, temperature, and oxidizer concentration. Kinetics studies of the reactions of nitrate and nitrite ions with various reducing reagents in supercritical water show that they can be rapidly and completely destroyed at temperatures above 525{degrees}C. The use of slurries and hydrolysis to introduce high concentrations of explosives into a supercritical water reactor is examined. For some compounds the rate of reaction depends on particle size. The hydrolysis of explosives at low temperatures (<100{degrees}C) and low pressures (<1 atm) under basic conditions produces water soluble, non-explosive products which are easily destroyed by supercritical water oxidation. Large pieces of explosives (13 cm diameter) have been successfully hydrolyzed. The rate, extent, and products of the hydrolysis depend on the type and concentration of base. Results from the base hydrolysis of triple base propellant M31A1E1 and the subsequent supercritical water oxidation of the hydrolysis products are presented.

Beulow, S.J.; Dyer, R.B.; Harradine, D.M.; Robinson, J.M.; Oldenborg, R.C.; Funk, K.A.; McInroy, R.E.; Sanchez, J.A.; Spontarelli, T.

1993-10-01

382

Steam Oxidation of Fossil Power Plant Materials: Collaborative Research to Enable Advanced Steam Power Cycles  

DOE PAGESBeta

Research into improved materials systems and associated manufacturing and reliability issues is a major part of initiatives to produce cleaner and cheaper energy systems in the UK and the USA. Under the auspices of a Memorandum of Understanding on Energy R&D, a work programme concerned with steam oxidation has been conducted. The focus was on the generation of definitive information regarding the oxidation behaviour in steam of current and developmental ferritic steels, austenitic steels, and nickelbased alloys required to enable advanced steam power cycles. The results were intended to provide a basis for quantifying the rate of metal loss expected under advanced steam cycle conditions, as well as understanding of the evolution of oxide scale morphologies with time and temperature to identify features that could influence scale exfoliation characteristics. This understanding and acquired data were used to develop and validate models of oxide growth and loss by exfoliation. This paper provides an overview of the activity and highlights a selection of the results coming from the programme.

A. T. Fry; I. G Wright; N. J Simms; B. McGhee; G. R. Holcomb

2013-11-19

383

A half-reaction alternative to water oxidation: chloride oxidation to chlorine catalyzed by silver ion.  

PubMed

Chloride oxidation to chlorine is a potential alternative to water oxidation to oxygen as a solar fuels half-reaction. Ag(I) is potentially an oxidative catalyst but is inhibited by the high potentials for accessing the Ag(II/I) and Ag(III/II) couples. We report here that the complex ions AgCl2(-) and AgCl3(2-) form in concentrated Cl(-) solutions, avoiding AgCl precipitation and providing access to the higher oxidation states by delocalizing the oxidative charge over the Cl(-) ligands. Catalysis is homogeneous and occurs at high rates and low overpotentials (10 mV at the onset) with ?M Ag(I). Catalysis is enhanced in D2O as solvent, with a significant H2O/D2O inverse kinetic isotope effect of 0.25. The results of computational studies suggest that Cl(-) oxidation occurs by 1e(-) oxidation of AgCl3(2-) to AgCl3(-) at a decreased potential, followed by Cl(-) coordination, presumably to form AgCl4(2-) as an intermediate. Adding a second Cl(-) results in "redox potential leveling", with further oxidation to {AgCl2(Cl2)}(-) followed by Cl2 release. PMID:25700124

Du, Jialei; Chen, Zuofeng; Chen, Chuncheng; Meyer, Thomas J

2015-03-11

384

A soluble form of nano-sized colloidal manganese(IV) oxide as an efficient catalyst for water oxidation.  

PubMed

A soluble form of colloidal manganese(IV) oxide showed efficient oxygen evolution or water oxidation in presence of oxone, H(2)O(2), cerium(IV) ammonium nitrate and tris(2,2'-bipyridyl)ruthenium(III). PMID:21359392

Najafpour, Mohammad Mahdi

2011-04-21

385

Peracetic acid oxidation of saline waters in the absence and presence of H ?O ?: secondary oxidant and disinfection byproduct formation.  

PubMed

Peracetic acid (PAA) is a disinfectant considered for use in ballast water treatment, but its chemical behavior in such systems (i.e., saline waters) is largely unknown. In this study, the reactivity of PAA with halide ions (chloride and bromide) to form secondary oxidants (HOCl, HOBr) was investigated. For the PAA-chloride and PAA-bromide reactions, second-order rate constants of (1.47 ± 0.58) × 10(-5) and 0.24 ± 0.02 M(-1) s(-1) were determined for the formation of HOCl or HOBr, respectively. Hydrogen peroxide (H2O2), which is always present in PAA solutions, reduced HOCl or HOBr to chloride or bromide, respectively. As a consequence, in PAA-treated solutions with [H2O2] > [PAA], the HOBr (HOCl) steady-state concentrations were low with a limited formation of brominated (chlorinated) disinfection byproducts (DBPs). HOI (formed from the PAA-iodide reaction) affected this process because it can react with H2O2 back to iodide. H2O2 is thus consumed in a catalytic cycle and leads to less efficient HOBr scavenging at even low iodide concentrations (<1 ?M). In PAA-treated solutions with [H2O2] < [PAA] and high bromide levels, mostly brominated DBPs are formed. In synthetic water, bromate was formed from the oxidation of bromide. In natural brackish waters, bromoform (CHBr3), bromoacetic acid (MBAA), dibromoacetic acid (DBAA), and tribromoacetic acid (TBAA) formed at up to 260, 106, 230, and 89 ?g/L, respectively for doses of 2 mM (ca. 150 mg/L) PAA and [H2O2] < [PAA]. The same brackish waters, treated with PAA with [H2O2] ? [PAA], similar to conditions found in commercial PAA solutions, resulted in no trihalomethanes and only low haloacetic acid concentrations. PMID:25611970

Shah, Amisha D; Liu, Zheng-Qian; Salhi, Elisabeth; Höfer, Thomas; von Gunten, Urs

2015-02-01

386

K562 cells display different vulnerability to H?O? induced oxidative stress in differing cell cycle phases.  

PubMed

Oxidative stress can be defined as the increase of oxidizing agents like reactive oxygen and nitrogen species, or the imbalance between the antioxidative defense mechanism and oxidants. Cell cycle checkpoint response can be defined as the arrest of the cell cycle functioning after damaging chemical exposure. This temporary arrest may be a period of time given to the cells to repair the DNA damage before entering the cycle again and completing mitosis. In order to determine the effects of oxidative stress on several cell cycle phases, human erytroleukemia cell line (K562) was synchronized with mimosine and genistein, and cell cycle analysis carried out. Synchronized cells were exposed to oxidative stress with hydrogen peroxide (H2O2) at several concentrations and different times. Changes on mitochondria membrane potential (??m) of K562 cells were analyzed in G1, S, and G2 /M using Rhodamine 123 (Rho 123). To determine apoptosis and necrosis, stressed cells were stained with Annexin V (AnnV) and propidium iodide (PI) for flow cytometry. Changes were observed in the ??m of synchronized and asynchronized cells that were exposed to oxidative stress. Synchronized cells in S phase proved resistant to the effects of oxidative stress and synchronized cells at G2 /M phase were sensitive to the effects of H2O2 -induced oxidative stress at 500??M and above. PMID:25181960

Akcakaya, Handan; Dal, Fulya; Tok, Sabiha; Cinar, Suzan-Adin; Nurten, Rustem

2015-02-01

387

Water-Mediated Proton Hopping on an Iron Oxide Surface  

SciTech Connect

The diffusion of hydrogen atoms across solid oxide surfaces is often assumed to be accelerated by the presence of water molecules. Here we present a high-resolution, high-speed scanning tunneling microscopy (STM) study of the diffusion of H atoms on an FeO thin film. STM movies directly reveal a water-mediated hydrogen diffusion mechanism on the oxide surface at temperatures between 100 and 300 kelvin. Density functional theory calculations and isotope-exchange experiments confirm the STM observations, and a proton-transfer mechanism that proceeds via an H3O+-like transition state is revealed. This mechanism differs from that observed previously for rutile TiO2(110), where water dissociation is a key step in proton diffusion.

Merte, L. R.; Peng, Guowen; Bechstein, Ralf; Rieboldt, Felix; Farberow, Carrie A.; Grabow, Lars C.; Kudernatsch, Wilhelmine; Wendt, Stefen; Laegsgaard, E.; Mavrikakis, Manos; Besenbacher, Fleming

2012-05-18

388

NASA Contributions to Improve Understanding of Extreme Events in the Global Energy and Water Cycle  

NASA Technical Reports Server (NTRS)

The U.S. Climate Change Science Program (CCSP) has established the water cycle goals of the Nation's climate change program. Accomplishing these goals will require, in part, an accurate accounting of the key reservoirs and fluxes associated with the global water and energy cycle, including their spatial and temporal variability. through integration of all necessary observations and research tools, To this end, in conjunction with NASA's Earth science research strategy, the overarching long-term NASA Energy and Water Cycle Study (NEWS) grand challenge can he summarized as documenting and enabling improved, observationally based, predictions of water and energy cycle consequences of Earth system variability and change. This challenge requires documenting and predicting trends in the rate of the Earth's water and energy cycling that corresponds to climate change and changes in the frequency and intensity of naturally occurring related meteorological and hydrologic events, which may vary as climate may vary in the future. The cycling of water and energy has obvious and significant implications for the health and prosperity of our society. The importance of documenting and predicting water and energy cycle variations and extremes is necessary to accomplish this benefit to society.

Lapenta, William M.

2008-01-01

389

High temperature oxidation of molybdenum in water vapor environments  

NASA Astrophysics Data System (ADS)

Molybdenum has recently gained attention as a candidate cladding material for use in light water reactors. Its excellent high temperature mechanical properties and stability under irradiation suggest that it could offer benefits to performance under a wide range of reactor conditions, but little is known about its oxidation behavior in water vapor containing atmospheres. The current study was undertaken to elucidate the oxidation behavior of molybdenum in water vapor environments to 1200 °C in order to provide an initial assessment of its feasibility as a light water reactor cladding. Initial observations indicate that at temperatures below 1000 °C, the kinetics of mass loss in water vapor would not be detrimental to cladding integrity during an off-normal event. Above 1000 °C, degradation is more rapid but remains slower than observed for optimized zirconium cladding alloys. The effect of hydrogen-water vapor and oxygen-water vapor mixtures on material loss was also explored at elevated temperatures. Parts-per-million levels of either hydrogen or oxygen will minimally impact performance, but hydrogen contents in excess of 1000 ppm were observed to limit volatilization at 1000 °C.

Nelson, A. T.; Sooby, E. S.; Kim, Y.-J.; Cheng, B.; Maloy, S. A.

2014-05-01

390

Origin and role of water ice clouds in the Martian water cycle as inferred from a general circulation model  

Microsoft Academic Search

In this paper, we present the results obtained by the general circulation model developed at the Laboratoire de Météorologie Dynamique which has been used to simulate the Martian hydrological cycle. Our model, which employs a simplified cloud scheme, reproduces the observed Martian water cycle with unprecedented agreement. The modeled seasonal evolution of cloudiness, which also compares well with data, is

F. Montmessin; F. Forget; P. Rannou; M. Cabane; R. M. Haberle

2004-01-01

391

Light-harvesting photocatalysis for water oxidation using mesoporous organosilica.  

PubMed

An organic-based photocatalysis system for water oxidation, with visible-light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd-PMO), a visible-light harvesting antenna, was supported with [Ru(II)(bpy)3(2+)] complex (bpy = 2,2'-bipyridyl) coupled with iridium oxide (IrO(x)) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd-PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer. The excited state of Ru complex is oxidatively quenched by a sacrificial oxidant (Na2S2O8) to form Ru(3+) species. The Ru(3+) species extracts an electron from IrO(x) to oxidize water for oxygen production. The reaction quantum yield was 0.34?%, which was improved to 0.68 or 1.2?% by the modifications of PMO. A unique sequence of reactions mimicking natural photosystem?II, 1)?light-harvesting, 2)?charge separation, and 3)?oxygen generation, were realized for the first time by using the light-harvesting PMO. PMID:24890840

Takeda, Hiroyuki; Ohashi, Masataka; Goto, Yasutomo; Ohsuna, Tetsu; Tani, Takao; Inagaki, Shinji

2014-07-14

392

Fatigue oxidation interaction in a superalloy—application to life prediction in high temperature low cycle fatigue  

NASA Astrophysics Data System (ADS)

A study of the interaction between fatigue and oxidation has been carried out in the case of a cast cobalt base superalloy MARM 509 tested in laboratory air at 900 °C. The influence of fatigue cycling on oxidation of this alloy has been studied by quantitative metallography on polished specimens exposed to air in a furnace and on strain-cycled low-cycle fatigue specimens. The oxidation kinetics were determined by thickness measurements for matrix oxidation and by oxidized depth measurements for the preferential oxidation of MC carbides. In both cases the oxidation kinetics were found to be dramatically enhanced by cycling for the matrix oxidation according to a linear relationship with plastic strain amplitude and less dramatically for carbides according to an exponential relationship with the maximum cyclic stress. From these observations a damage equation which describes fatigue damage as a crack growth process has been proposed: the elementary crack advance is a summation of a mechanical contribution due to the fatigue process itself which is described by Tomkins’ equation and of an oxidation contribution which has been evaluated from metallographic measurements. Integration of this crack growth equation gives predicted fatigue lives which are in good agreement with experimental results within a factor of two.

Reuchet, J.; Remy, L.

1983-01-01

393

Oxide-carbon composites and porous oxides prepared via water-swellable polymer networks  

SciTech Connect

Water-swellable polymer networks (WSPN) were employed as media for lodging metal nitrate salts or partially hydrolyzed tetraethyl orthosilicate (TEOS), which are precursors for inorganic oxides. The loading achieved either via the polymerization of a suitable monomer and a cross-linker in an aqueous solution of the precursor or, in the case of TEOS, via the simultaneous polymerization of both monomers. The pyrolysis of the precursor loaded network under N{sub 2} flow generated interpenetrating networks of carbon and metal oxide. The combustion of the composite in air removed the carbon network and a porous metal oxide framework remained. On the basis of the methodology, a coating layer of C-SiO{sub 2} composite was generated on a carbon-fiber, and a porous powders of SiO{sub 2}, ZrO{sub 2}, MgO, and CuO-ZnO-Al{sub 2}O{sub 3} oxide(s) were synthesized. It was found that the specific surface area of the oxides is affected by the nature of the WSPN. Two methodologies which lead to particles were developed. In one of them, sedimentation polymerization, large particles of about 1 mm size were obtained. In the other one, which starts from an emulsion of a water solution in an organic liquid (toluene, cyclohexane), micrometer size particles were prepared. 16 refs., 10 figs., 6 tabs.

Ruckenstein, E.; Hong, L. [State Univ. of New York, Buffalo, NY (United States)] [State Univ. of New York, Buffalo, NY (United States)

1996-02-01

394

Photocatalytic oxygen evolution from non-potable water by a bioinspired molecular water oxidation catalyst  

Microsoft Academic Search

We report that a model complex of the Photosystem II-Water Oxidizing Complex (PSII-WOC) facilitates, exclusively, photocatalytic water oxidation from non-potable water sources like seawater, under suitable conditions. When the manganese cubane cluster [Mn4O4L6]+, (L=(p-MeO-Ph)2PO2), 1+, is incorporated within a Nafion membrane deposited on an electrolytic anode that is poised at 1.00V (vs. Ag\\/AgCl) and illuminated with light, catalysis of only

Robin Brimblecombe; Jun Chen; Pawel Wagner; Timothy Buchhorn; G. Charles Dismukes; Leone Spiccia; Gerhard F. Swiegers

2011-01-01

395

Ferrates: greener oxidants with multimodal action in water treatment technologies.  

PubMed

Conspectus One of the biggest challenges for humanity in the 21st century is easy access to purified and potable water. The presence of pathogens and toxins in water causes more than two million deaths annually, mostly among children under the age of five. Identifying and deploying effective and sustainable water treatment technologies is critical to meet the urgent need for clean water globally. Among the various agents used in the purification and treatment of water, iron-based materials have garnered particular attention in view of their special attributes such as their earth-abundant and environmentally friendly nature. In recent years, higher-valent tetraoxy iron(VI) (Fe(VI)O4(2-), Fe(VI)), commonly termed, ferrate, is being explored for a broad portfolio of applications, including a greener oxidant in synthetic organic transformations, a water oxidation catalyst, and an efficient agent for abatement of pollutants in water. The use of Fe(VI) as an oxidant/disinfectant and further utilization of the ensuing iron(III) oxides/hydroxide as coagulants are other additional attributes of ferrate for water treatment. This multimodal action and environmentally benign character of Fe(VI) are key advantages over other commonly used oxidants (e.g., chlorine, chlorine dioxide, permanganate, hydrogen peroxide, and ozone). This Account discusses current state-of-the-art applications of Fe(VI) and the associated unique chemistry of these high-valence states of iron. The main focus centers around the description and salient properties of ferrate species involving various electron transfer and oxygen-atom transfer pathways in terms of presently accepted mechanisms. The mechanisms derive the number of electron equivalents per Fe(VI) (i.e., oxidation capacity) in treating various contaminants. The role of pH in the kinetics of the reactions and in determining the removal efficiency of pollutants is highlighted; the rates of competing reactions of Fe(VI) with itself, water, and the contaminants, which are highly pH dependent, determine the optimum pH range of maximum efficacy. The main emphasis of this account is placed on cases where various modes of ferrate action are utilized, including the treatment of nitrogen- and sulfur-containing waste products, antibiotics, viruses, bacteria, arsenic, and heavy metals. For example, the oxidative degradation of N- and S-bearing contaminants by Fe(VI) yields either Fe(II) or Fe(III) via the intermediacy of Fe(IV) and Fe(V) species, respectively (e.g., Fe(VI) ? Fe(IV) ? Fe(II) and Fe(VI) ? Fe(V) ? Fe(III)). Oxidative transformations of antibiotics such as trimethoprim by Fe(VI) generate products with no residual antibiotic activity. Disinfection and inactivation of bacteria and viruses can easily be achieved by Fe(VI). Advanced applications involve the use of ferrate for the degradation of cyanobacteria and microcystin originating from algal blooms and for covalently embedding arsenic and heavy metals into the structure of formed magnetic iron(III) oxides, therefore preventing their leaching. Applications of state-of-the-art analytical techniques, namely, in situ Mössbauer spectroscopy, rapid-freeze electron paramagnetic resonance, nuclear forward scattering of synchrotron radiation, and mass spectrometry will enhance the mechanistic understanding of ferrate species. This will make it possible to unlock the true potential of ferrates for degrading emerging toxins and pollutants, and in the sustainable production and use of nanomaterials in an energy-conserving environment. PMID:25668700

Sharma, Virender K; Zboril, Radek; Varma, Rajender S

2015-02-17

396

On the Design of Oxide Films, Nanomaterials, and Heterostructures for Solar Water Oxidation Photoanodes  

NASA Astrophysics Data System (ADS)

Photoelectrochemistry and its associated technologies show unique potential to facilitate the large-scale production of solar fuels—those energy-rich chemicals obtained through conversion processes driven by solar energy, mimicking the photosynthetic process of green plants. The critical component of photoelectrochemical devices designed for this purpose is the semiconductor photoelectrode, which must be optically absorptive, chemically stable, and possess the required electronic band alignment with respect to the redox couple of the electrolyte to drive the relevant electrochemical reactions. After many decades of investigation, the primary technological obstacle remains the development of photoelectrode structures capable of efficient and stable conversion of light with visible frequencies, which is abundant in the solar spectrum. Metal oxides represent one of the few material classes that can be made photoactive and remain stable to perform the required functions. The unique range of functional properties of oxides, and especially the oxides of transition metals, relates to their associated diversity of cation oxidation states, cation electronic configurations, and crystal structures. In this dissertation, the use of metal oxide films, nanomaterials, and heterostructures in photoelectrodes enabling the solar-driven oxidation of water and generation of hydrogen fuel is examined. A range of transition- and post-transition-metal oxide material systems and nanoscale architectures is presented. The first chapters present results related to electrodes based on alpha-phase iron(III) oxide, a promising visible-light-active material widely investigated for this application. Studies of porous films fabricated by physical vapor deposition reveal the importance of structural quality, as determined by the deposition substrate temperature, on photoelectrochemical performance. Heterostructures with nanoscale feature dimensionality are explored and reviewed in a later chapter, which describes the methodologies to combine the unique and complimentary functional properties of dissimilar oxides to optimize the water photo-oxidation process Experimental results based on an iron(III) oxide-tungsten(VI) oxide system show enhancements associated with the heterostructure, which may indicate the presence of unexpected minority carrier dynamics, as observed additionally by ultrafast transient absorption spectroscopy. Next, a new conceptual framework for the design of solar water oxidation photoelectrodes based on the spatially inhomogeneous doping of wide-bandgap metal oxide nanostructures is introduced and experimentally verified. It is found that optical absorption and electronic conduction can be decoupled and optimized by spatially segregating the functional impurity species that facilitate their associated physical processes. In the final chapters of this dissertation the electronic structures of key oxide-oxide interfaces, relevant to the operation of efficient photoanodes, are examined using synchrotron-based soft x-ray spectroscopy. These studies indicate that the interfacial regions of electrodes possess distinct electronic structures, which deviate in terms of orbital character and occupancy from those of their constituent bulk oxides. These observations inform methodology to address certain operational deficiencies associated with the use of metal oxides for solar energy conversion applications.

Kronawitter, Coleman Xaver

397

Life-cycle analysis on biodiesel production from microalgae: Water footprint and nutrients balance  

Microsoft Academic Search

This research examines the life-cycle water and nutrients usage of microalgae-based biodiesel production. The influence of water types, operation with and without recycling, algal species, geographic distributions are analyzed. The results confirm the competitiveness of microalgae-based biofuels and highlight the necessity of recycling harvested water and using sea\\/wastewater as water source. To generate 1kg biodiesel, 3726kg water, 0.33kg nitrogen, and

Jia Yang; Ming Xu; Xuezhi Zhang; Qiang Hu; Milton Sommerfeld; Yongsheng Chen

2011-01-01

398

Paralinear Oxidation of CVD SiC in Water Vapor  

NASA Technical Reports Server (NTRS)

The oxidation kinetics of CVD SiC were monitored by thermogravimetric analysis (TGA) in a 50% H2O/50% O2 gas mixture flowing at 4.4 cm/s for temperatures between 1200 and 1400 C. Paralinear weight change kinetics were observed as the water vapor oxidized the SiC and simultaneously volatilized the silica scale. The long-term degradation rate of SiC is determined by the volatility of the silica scale. Rapid SiC surface recession rates were estimated from these data for actual aircraft engine combustor conditions.

Opila, Elizabeth J.; Hann, Raiford E., Jr.

1997-01-01

399

GEWEX: The Global Energy and Water Cycle Experiment  

NASA Technical Reports Server (NTRS)

GEWEX is one of the world's largest global change research programs. Its purpose is to observe and understand the hydrological cycle and energy fluxes in the atmosphere, at land surfaces and in the upper oceans.

Chahine, M.; Vane, D.

1994-01-01

400

eWaterCycle: A high resolution global hydrological model  

NASA Astrophysics Data System (ADS)

In 2013, the eWaterCycle project was started, which has the ambitious goal to run a high resolution global hydrological model. Starting point was the PCR-GLOBWB built by Utrecht University. The software behind this model will partially be re-engineered in order to enable to run it in a High Performance Computing (HPC) environment. The aim is to have a spatial resolution of 1km x 1km. The idea is also to run the model in real-time and forecasting mode, using data assimilation. An on-demand hydraulic model will be available for detailed flow and flood forecasting in support of navigation and disaster management. The project faces a set of scientific challenges. First, to enable the model to run in a HPC environment, model runs were analyzed to examine on which parts of the program most CPU time was spent. These parts were re-coded in Open MPI to allow for parallel processing. Different parallelization strategies are thinkable. In our case, it was decided to use watershed logic as a first step to distribute the analysis. There is rather limited recent experience with HPC in hydrology and there is much to be learned and adjusted, both on the hydrological modeling side and the computer science side. For example, an interesting early observation was that hydrological models are, due to their localized parameterization, much more memory intensive than models of sister-disciplines such as meteorology and oceanography. Because it would be deadly to have to swap information between CPU and hard drive, memory management becomes crucial. A standard Ensemble Kalman Filter (enKF) would, for example, have excessive memory demands. To circumvent these problems, an alternative to the enKF was developed that produces equivalent results. This presentation shows the most recent results from the model, including a 5km x 5km simulation and a proof of concept for the new data assimilation approach. Finally, some early ideas about financial sustainability of an operational global hydrological model are presented.

van de Giesen, Nick; Bierkens, Marc; Drost, Niels; Hut, Rolf; Sutanudjaja, Edwin

2014-05-01

401

Effects of tempol and redox-cycling nitroxides in models of oxidative stress.  

PubMed

Tempol is a redox-cycling nitroxide that promotes the metabolism of many reactive oxygen species (ROS) and improves nitric oxide bioavailability. It has been studied extensively in animal models of oxidative stress. Tempol has been shown to preserve mitochondria against oxidative damage and improve tissue oxygenation. Tempol improved insulin responsiveness in models of diabetes mellitus and improved the dyslipidemia, reduced the weight gain and prevented diastolic dysfunction and heart failure in fat-fed models of the metabolic syndrome. Tempol protected many organs, including the heart and brain, from ischemia/reperfusion damage. Tempol prevented podocyte damage, glomerulosclerosis, proteinuria and progressive loss of renal function in models of salt and mineralocorticosteroid excess. It reduced brain or spinal cord damage after ischemia or trauma and exerted a spinal analgesic action. Tempol improved survival in several models of shock. It protected normal cells from radiation while maintaining radiation sensitivity of tumor cells. Its paradoxical pro-oxidant action in tumor cells accounted for a reduction in spontaneous tumor formation. Tempol was effective in some models of neurodegeneration. Thus, tempol has been effective in preventing several of the adverse consequences of oxidative stress and inflammation that underlie radiation damage and many of the diseases associated with aging. Indeed, tempol given from birth prolonged the life span of normal mice. However, presently tempol has been used only in human subjects as a topical agent to prevent radiation-induced alopecia. PMID:20153367

Wilcox, Christopher S

2010-05-01

402

Effects of tempol and redox-cycling nitroxides in models of oxidative stress  

PubMed Central

Tempol is a redox cycling nitroxide that promotes the metabolism of many reactive oxygen species (ROS) and improves nitric oxide bioavailability. It has been studied extensively in animal models of oxidative stress. Tempol has been shown to preserve mitochondria against oxidative damage and improve tissue oxygenation. Tempol improved insulin responsiveness in models of diabetes mellitus and improved the dyslipidemia, reduced the weight gain and prevented diastolic dysfunction and heart failure in fat-fed models of the metabolic syndrome. Tempol protected many organs, including the heart and brain, from ischemia/reperfusion damage. Tempol prevented podocyte damage, glomerulosclerosis, proteinuria and progressive loss of renal function in models of salt and mineralocorticosteroid excess. It reduced brain or spinal cord damage after ischemia or trauma and exerted a spinal analgesic action. Tempol improved survival in several models of shock. It protected normal cells from radiation while maintaining radiation sensitivity of tumor cells. Its paradoxical pro-oxidant action in tumor cells accounted for a reduction in spontaneous tumor formation. Tempol was effective in some models of neurodegeneration. Thus, tempol has been effective in preventing several of the adverse consequences of oxidative stress and inflammation that underlie radiation damage and many of the diseases associated with aging. Indeed, tempol given from birth prolonged the life span of normal mice. However, presently tempol has been used only in human subjects as a topical agent to prevent radiation-induced alopecia. PMID:20153367

Wilcox, Christopher S.

2010-01-01

403

Ground Water Sampling at ISCO Sites - Residual Oxidant Impact on Sample Quality and Sample Preservation Guideline  

EPA Science Inventory

In-situ chemical oxidation (ISCO) involves the delivery of a chemical oxidant into the subsurface where oxidative reactions transform ground water contaminants into less toxic or harmless byproducts. Due to oxidant persistence, ground water samples collected at hazardous waste si...

404

Research and development of an air-cycle heat-pump water heater. Final report  

Microsoft Academic Search

A prototype reverse Brayton air cycle heat pump water heater has been designed and built for residential applications. The system consists of a compressor\\/expander, an air-water heat exchanger, an electric motor, a water circulation pump, a thermostat, and fluid management controls. The prototype development program consisted of a market analysis, design study, and development testing. A potential residential market for

J. T. Dieckmann; A. J. Erickson; A. C. Harvey; W. M. Toscano

1979-01-01

405

A preliminary study of the tropical water cycle and its sensitivity to surface warming  

Microsoft Academic Search

This paper presents preliminary findings of an investigation of the water budget of tropical cumulus convection using the Goddard Cumulus Ensemble Model (GCEM). Results of an experiment designed to obtain a [open quotes]fingerprint[close quotes] in the tropical hydrologic cycle in response to surface warming are also presented. The ensemble mean water budget shows the distribution of water vapor and cloud

K. M. Lau; W. K. Tao; C. H. Sui

1993-01-01

406

ESA's STSE WACMOS Project: Towards a Water Cycle Multimission Observation Strategy  

Microsoft Academic Search

Understanding the role of the global water cycle in the Earth system it is essential to be able to measure from space hydro-climatic variables, such as radiation, precipitation, evapotranspiration, soil moisture, clouds, water vapour, surface water and runoff, vegetation state, albedo and surface temperature, etc. Such measurements are required to further increase not only our understanding of the different components

Diego Fernández Prieto; Bob Su

2010-01-01

407

Deep Water Cycle: its Role in Earth's Thermal Evolution and Plate Tectonics  

Microsoft Academic Search

Earth is unique among the terrestrial planets in our solar system because it has plate tectonics and abundant surface water. It has long been suggested that these two salient features are intimately related. New constraints on water concentrations in the Earth's interior and on mechanisms for mantle degassing and regassing have improved our knowledge of Earth's deep water cycle; however,

T. W. Becker; J. W. Crowley; M. Gérault; T. Höink; A. J. Schaeffer; P. H. Barry; J. Frost; J. Girard; M. Nunez-Valdez; M. Hirschmann; S. Hier-Majumder; R. J. O'Connell

2010-01-01

408

Theoretical study of catalytic mechanism for single-site water oxidation process  

PubMed Central

Water oxidation is a linchpin in solar fuels formation, and catalysis by single-site ruthenium complexes has generated significant interest in this area. Combining several theoretical tools, we have studied the entire catalytic cycle of water oxidation for a single-site catalyst starting with [RuII(tpy)(bpm)(OH2)]2+ (i.e., [RuII-OH2]2+; tpy is 2,2??6?,2??-terpyridine and bpm is 2,2?-bypyrimidine) as a representative example of a new class of single-site catalysts. The redox potentials and pKa calculations for the first two proton-coupled electron transfers (PCETs) from [RuII-OH2]2+ to [RuIV = O]2+ and the following electron-transfer process to [RuV = O]3+ suggest that these processes can proceed readily in acidic or weakly basic conditions. The subsequent water splitting process involves two water molecules, [RuV = O]3+ to generate [RuIII-OOH]2+, and H3O+ with a low activation barrier (?10 kcal/mol). After the key O---O bond forming step in the single-site Ru catalysis, another PECT process oxidizes [RuIII-OOH]2+ to [RuIV-OO]2+ when the pH is lower than 3.7. Two possible forms of [RuIV-OO]2+, open and closed, can exist and interconvert with a low activation barrier (< 7 kcal/mol) due to strong spin-orbital coupling effects. In Pathway 1 at pH = 1.0, oxygen release is rate-limiting with an activation barrier ?12 kcal/mol while the electron-transfer step from [RuIV-OO]2+ to [RuV - OO]3+ becomes rate-determining at pH = 0 (Pathway 2) with Ce(IV) as oxidant. The results of these theoretical studies with atomistic details have revealed subtle details of reaction mechanisms at several stages during the catalytic cycle. This understanding is helpful in the design of new catalysts for water oxidation. PMID:22615356

Lin, Xiangsong; Hu, Xiangqian; Concepcion, Javier J.; Chen, Zuofeng; Liu, Shubin; Meyer, Thomas J.; Yang, Weitao

2012-01-01

409

Effects of microbial redox cycling of iron on cast iron pipe corrosion in drinking water distribution systems.  

PubMed

Bacterial characteristics in corrosion products and their effect on the formation of dense corrosion scales on cast iron coupons were studied in drinking water, with sterile water acting as a reference. The corrosion process and corrosion scales were characterized by electrochemical and physico-chemical measurements. The results indicated that the corrosion was more rapidly inhibited and iron release was lower due to formation of more dense protective corrosion scales in drinking water than in sterile water. The microbial community and denitrifying functional genes were analyzed by pyrosequencing and quantitative polymerase chain reactions (qPCR), respectively. Principal component analysis (PCA) showed that the bacteria in corrosion products played an important role in the corrosion process in drinking water. Nitrate-reducing bacteria (NRB) Acidovorax and Hydrogenophaga enhanced iron corrosion before 6 days. After 20 days, the dominant bacteria became NRB Dechloromonas (40.08%) with the protective corrosion layer formation. The Dechloromonas exhibited the stronger corrosion inhibition by inducing the redox cycling of iron, to enhance the precipitation of iron oxides and formation of Fe3O4. Subsequently, other minor bacteria appeared in the corrosion scales, including iron-respiring bacteria and Rhizobium which captured iron by the produced siderophores, having a weaker corrosion-inhibition effect. Therefore, the microbially-driven redox cycling of iron with associated microbial capture of iron caused more compact corrosion scales formation and lower iron release. PMID:25150521

Wang, Haibo; Hu, Chun; Zhang, Lili; Li, Xiaoxiao; Zhang, Yu; Yang, Min

2014-11-15

410

Photochemical, electrochemical, and photoelectrochemical water oxidation catalyzed by water-soluble mononuclear ruthenium complexes.  

PubMed

Two mononuclear ruthenium complexes [Ru(H2tcbp)(isoq)2] (1) and [Ru(H2tcbp)(pic)2] (2) (H4tcbp=4,4',6,6'-tetracarboxy-2,2'-bipyridine, isoq=isoquinoline, pic=4-picoline) are synthesized and fully characterized. Two spare carboxyl groups on the 4,4'-positions are introduced to enhance the solubility of 1 and 2 in water and to simultaneously allow them to tether to the electrode surface by an ester linkage. The photochemical, electrochemical, and photoelectrochemical water oxidation performance of 1 in neutral aqueous solution is investigated. Under electrochemical conditions, water oxidation is conducted on the deposited indium-tin-oxide anode, and a turnover number higher than 15,000 per water oxidation catalyst (WOC) 1 is obtained during 10?h of electrolysis under 1.42?V vs. NHE, corresponding to a turnover frequency of 0.41?s(-1). The low overpotential (0.17?V) of electrochemical water oxidation for 1 in the homogeneous solution enables water oxidation under visible light by using [Ru(bpy)3](2+) (P1) (bpy=2,2'-bipyridine) or [Ru(bpy)2(4,4'-(COOEt)2-bpy)](2+) (P2) as a photosensitizer. In a three-component system containing 1 or 2 as a light-driven WOC, P1 or P2 as a photosensitizer, and Na2S2O8 or [CoCl(NH3)5]Cl2 as a sacrificial electron acceptor, a high turnover frequency of 0.81?s(-1) and a turnover number of up to 600 for 1 under different catalytic conditions are achieved. In a photoelectrochemical system, the WOC 1 and photosensitizer are immobilized together on the photoanode. The electrons efficiently transfer from the WOC to the photogenerated oxidizing photosensitizer, and a high photocurrent density of 85??A?cm(-2) is obtained by applying 0.3?V bias vs. NHE. PMID:25205065

Li, Ting-Ting; Zhao, Wei-Liang; Chen, Yong; Li, Fu-Min; Wang, Chuan-Jun; Tian, Yong-Hua; Fu, Wen-Fu

2014-10-20

411

Results of the Collaborative Energy and Water Cycle Information Services (CEWIS) Workshop on Heterogeneous Dataset Analysis Preparation  

Microsoft Academic Search

In support of the NASA Energy and Water Cycle Study (NEWS), the Collaborative Energy and Water Cycle Information Services (CEWIS), sponsored by NEWS Program Manager Jared Entin, was initiated to develop an evolving set of community-based data and information services that would facilitate users to locate, access, and bring together multiple distributed heterogeneous energy and water cycle datasets. The CEWIS

S. J. Kempler; W. L. Teng; J. G. Acker; D. R. Belvedere; Z. Liu; G. G. Leptoukh

2010-01-01

412

Biological water oxidation: Lessons from Nature Mohammad Mahdi Najafpour a,b,  

E-print Network

. An efficient system for water oxidation exists in the water oxidizing complex in cyanobacteria, algae already evolved in cya- nobacteria, algae and plants [19­35]. The biological water oxidation, it is necessary to first synthesize a stable, low cost, and effi- cient, envi

Govindjee

413

Progress in base-metal water oxidation catalysis.  

PubMed

This minireview provides a brief overview of the progress that has been made in developing homogeneous water oxidation catalysts based on base metals (manganese, iron, cobalt, nickel, and copper) from the 1990s to mid-2014. The impact of each contribution is analyzed, and opportunities for further improvement are noted. In addition, the relative stabilities of the base-metal catalysts that have been reported are compared to illustrate the importance of developing more robust catalytic systems by using these metals. This manuscript is intended to provide a firm foundation for researchers entering the field of water oxidation based on base metals and a useful reference for those currently involved in the field. PMID:25066264

Parent, Alexander Rene; Sakai, Ken

2014-08-01

414

Thorium fuel for light water reactors—reducing proliferation potential of nuclear power fuel cycle  

Microsoft Academic Search

The proliferation potential of the light water reactor fuel cycle may be significantly reduced by utilization of thorium as a fertile component of the nuclear fuel. The main challenge of thorium utilization is to design a core and a fuel cycle, which would be proliferation?resistant and economically feasible. This challenge is met by the Radkowsky Thorium Reactor (RTR) concept presented

Alex Galperin; Paul Reichert; Alvin Radkowsky

1997-01-01

415

Method of water level control for a combined cycle power plant and control system therefor  

Microsoft Academic Search

A method and system for controlling water level of a drum of a heat recovery steam generator for a combined cycle power plant is provided. The combined cycle power plant includes gas and steam turbines and the steam generator for recovering heat in exhaust gases from the gas turbine and for using the recovered heat to produce and supply steam

1982-01-01

416

The Role of the Global Energy and Water Cycle EXperiment (GEWEX) in Advancing Hydrologic Sciences  

Microsoft Academic Search

The NRC study which resulted in the 1991 ``Opportunities in the Hydrologic Sciences'' report, discussed the importance of integrated and comprehensive programs that addressed data, modeling, and process studies of the components of the hydrologic process cycle. Simultaneously, an international effort was being organized that became known as the Global Energy and Water Cycle EXperiment (GEWEX), an initiative of the

S. Sorooshian; M. T. Chahine; T. P. Ackerman; R. G. Lawford; P. D. Try; P. J. van Oevelen

2009-01-01

417

Examining Language To Capture Scientific Understandings: The Case of the Water Cycle.  

ERIC Educational Resources Information Center

Presents units that address states of matter and changes of states of matter linked with the water cycle and integrates literacy and science. Discusses the language in science books. Lists characteristics of good science inquiry units. (Contains 11 references.) (ASK)

Varelas, Maria; Pappas, Christine; Barry, Anne; O'Neill, Amy

2001-01-01

418

Germanium cycling in the waters across a frontal zone: the Chatham Rise, New Zealand  

E-print Network

Germanium cycling in the waters across a frontal zone: the Chatham Rise, New Zealand Michael J for inorganic Ge, the profiles for monomethyl and dimethyl germanium (MMGe and DMGe) are conservative (Lewis et

Canberra, University of

419

Water-oxidation catalysis by synthetic manganese oxides--systematic variations of the calcium birnessite theme.  

PubMed

Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction for the conversion of renewable energy into storable fuels. High catalytic rates were especially observed for birnessites which contain calcium as part of their structures. With the aim to systematically improve the catalytic performance of such oxide materials, we used a flexible synthetic route to prepare three series of calcium birnessites, where we varied the calcium concentrations, the ripening times of the original precipitates and the temperature of the heat treatment following the initial synthetic steps (tempering) during the preparation process. The products were carefully analysed by a number of analytical techniques and then probed for WOC activity using the Ce(4+)-system. We find that our set of twenty closely related manganese oxides shows large, but somewhat systematic alterations in catalytic rates, indicating the importance of synthesis parameters for maximum catalytic performance. The catalyst of the series for which the highest water-oxidation rate was found is a birnessite of medium calcium content (Ca?:?Mn ratio 0.2?:?1) that had been subjected to a tempering temperature of 400 °C. On the basis of the detailed analysis of the results, a WOC reaction scheme for birnessites is proposed to explain the observed trends in reactivity. PMID:24225769

Frey, Carolin E; Wiechen, Mathias; Kurz, Philipp

2014-03-21

420

Breakdown of fast water transport in graphene oxides.  

PubMed

Fast slip flow was identified for water inside the interlayer gallery between graphene layers or carbon nanotubes. We report here that this significant flow rate enhancement (over two orders) breaks down with the presence of chemical functionalization and relaxation of nanoconfinement in graphene oxides. Molecular dynamics simulation results show that hydrodynamics applies in this circumstance, even at length scales down to nanometers. However, corrections to the slip boundary condition and apparent viscosity of nanoconfined flow must be included to make quantitative predictions. These results were discussed with the structural characteristics of liquid water and hydrogen-bond networks. PMID:24580178

Wei, Ning; Peng, Xinsheng; Xu, Zhiping

2014-01-01

421

Conversion of hazardous materials using supercritical water oxidation  

DOEpatents

A process for destruction of hazardous materials in a medium of supercritical water without the addition of an oxidant material. The harzardous material is converted to simple compounds which are relatively benign or easily treatable to yield materials which can be discharged into the environment. Treatment agents may be added to the reactants in order to bind certain materials, such as chlorine, in the form of salts or to otherwise facilitate the destruction reactions.

Rofer, Cheryl K. (Los Alamos, NM); Buelow, Steven J. (Los Alamos, NM); Dyer, Richard B. (Los Alamos, NM); Wander, Joseph D. (Parker, FL)

1992-01-01

422

Photoassembly of the water-oxidizing complex in photosystem II  

Microsoft Academic Search

The light-driven steps in the biogenesis and repair of the inorganic core comprising the O2-evolving center of oxygenic photosynthesis (photosystem II water-oxidation complex, PSII-WOC) are reviewed. These steps, known collectively as photoactivation, involve the photoassembly of the free inorganic cofactors to the cofactor-depleted PSII-(apo-WOC) driven by light and produce the active O2-evolving core comprised of Mn4CaOxCly. We focus on the

Jyotishman Dasgupta; Gennady M. Ananyev; G. Charles Dismukes

2008-01-01

423