Thursday, August 18, 2011

Scientists find way to identify synthetic biofuels in atmosphere

Scientists at the University of Miami Rosenstiel School of Marine & Atmospheric Science have discovered a technique to track urban atmospheric plumes thanks to a unique isotopic signature found in vehicle emissions.

Brian Giebel, a Marine and Atmospheric Chemistry graduate student working with Drs. Daniel Riemer and Peter Swart discovered that ethanol mixed in vehicle fuel is not completely burned, and that ethanol released in the engine's exhaust has a higher 13C to 12C ratio when compared to natural emissions from most living plants. In other words, the corn and sugarcane used to make biofuels impart a unique chemical signature that is related to the way these plants photosynthesize their nutrients.

The team suggests that ethanol's unique chemical signature can be used during aircraft sampling campaigns to identify and track plumes as they drift away from urban areas. The results of their efforts, titled "New Insights to the Use of Ethanol in Automotive Fuels: A Stable Isotopic Tracer for Fossil- and Bio-Fuel Combustion Inputs to the Atmosphere" appears in the journal Environmental Science & Technology.

Giebel collected and analyzed air from downtown Miami and the Everglades National Park and found that 75% of ethanol in Miami's urban air came from synthetic biofuels, while the majority of ethanol in the Everglades air was emitted from plants, even though a small quantity of city pollution from a nearby road floats into the park.

Air samples from the two locations were subjected to a precise scientific process, first separating the elements using gas chromatography, and then burning each component. The resulting carbon dioxide was put through a mass spectrometer, where the researchers were able to measure the abundance of each carbon isotope.

"According to global emissions estimates, plants release three times as much ethanol as man-made sources," said Giebel. "However, if the amount of ethanol used in our fuel continues to increase, vehicle emissions should eventually exceed natural emissions. This is particularly critical in urban areas because the majority of ethanol in the atmosphere is converted to acetaldehyde, which is highly reactive and considered to be a toxin detrimental to human health."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Miami Rosenstiel School of Marine & Atmospheric Science, via EurekAlert!, a service of AAAS.

Journal Reference:

Brian M. Giebel, Peter K. Swart, Daniel D. Riemer. New Insights to the Use of Ethanol in Automotive Fuels: A Stable Isotopic Tracer for Fossil- and Bio-Fuel Combustion Inputs to the Atmosphere. Environmental Science & Technology, 2011; 45 (15): 6661 DOI: 10.1021/es200982t

New paper examines future of seawater desalinization

A paper co-authored by William Phillip of the University of Notre Dame's Department of Chemical and Biomolecular Engineering and Menachem Elimelech, Robert Goizueta Professor of Environmental and Chemical Engineering at Yale University, appearing in this week's edition of the journal Science offers a critical review of the state of seawater desalination technology.

Elimelech and Phillip and examine how seawater desalination technology has advanced over the past 30 years, in what ways the state-of-the-art technology can be improved, and if seawater desalination is a sustainable technological solution to global water shortages.

"At present, one-third of the world's population lives in water stressed countries, Phillip said. "Increasing population, contamination of fresh water sources and climate change will cause this percentage to increase over the coming decade. Additionally, the social and ecological benefits of adequate fresh water resources are well-documented. Therefore, it is important to find a way to alleviate this stress with a sustainable solution."

The authors point out that in recent years, large-scale seawater desalination plants have been built in water-stressed countries to augment available water resources and construction of new desalination plants is expected to increase in the near future. Despite major advancements in desalination technologies, seawater desalination is still more energy intensive compared to conventional technologies for the treatment of fresh water. There are also concerns about the potential environmental impacts of large-scale seawater desalination plants.

In their Science paper, Elimelech and Phillip review the possible reductions in energy demand by state-of-the-art desalination technologies, the potential role of advanced materials and innovative technologies in improving the performance, and the sustainability of desalination as a technological solution to global water shortages.

The authors believe that there are important policy implications in their Science paper.

"Seawater desalination is an energy-intensive process; desalinating seawater consumes significantly more energy than treating traditional fresh water sources," Phillip said. "However, these traditional sources aren't going to be able to meet the growing demand for water worldwide. Several options already exist to augment fresh water sources -- including the treatment of low-quality local water sources, water recycling and reuse and water conservation, -- understanding where seawater desalination fits into this portfolio of water supply options is critical. Hopefully, our paper helps provide some of the information needed to inform the decisions of policy makers, water resource planers, scientists, and engineers on the suitability of desalination as a means to meet the increasing demands for water."

Phillip, who joined the Notre Dame faculty this year, is interested in examining how membrane structure and chemistry affect the transport of chemicals across a variety of membranes. Understanding the connection between functionality and property enables the design and fabrication of next generation membranes that provide more precise control over the transport of chemical species. These material advantages can be leveraged to design more effective and energy-efficient systems. Chemical separations at the water- energy nexus (e.g. desalination) is one area where this knowledge can be applied.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Notre Dame, via EurekAlert!, a service of AAAS.

Journal Reference:

Menachem Elimelech, William A. Phillip. The Future of Seawater Desalination: Energy, Technology, and the Environment. Science, 5 August 2011: Vol. 333 no. 6043 pp. 712-717 DOI: 10.1126/science.1200488

New sensor promises rapid detection of dangerous heavy metal levels in humans

 Work by University of Cincinnati researchers to create a sensor that provides fast feedback related to the presence and levels of heavy metals -- specifically manganese -- in humans is published in the August issue of the journal, Biomedical Microdevices.

Described in the article is the development of a low-cost, disposable lab-on-a-chip sensor that detects highly electronegative heavy metals more quickly than current technology generally available in health-care settings. It's envisioned that the new UC sensor technology will be used in point-of-care devices that provide needed feedback on heavy-metal levels within about ten minutes.

It's expected that the sensor will have potential for large-scale use in clinical, occupational and research settings, e.g., for nutrition testing in children.

The new sensor is environmentally friendly in that its working electrode is made of bismuth vs. the more typical mercury, and it's child friendly in that it requires only a droplet or two of blood for testing vs. the typical five-milliliter sample now required.

Explained one of the researchers, UC's Ian Papautsky, "The conventional methods for measuring manganese levels in blood currently requires about five milliliters of whole blood sent to a lab, with results back in 48 hours. For a clinician monitoring health effects by measuring these levels in a patient's blood -- where a small level of manganese is normal and necessary for metabolic functions -- you want an answer much more quickly about exposure levels, especially in a rural, high-risk area where access to a certified metals lab is limited. Our sensor will only require about two droplets of blood serum and will provide results in about ten minutes. It's portable and usable anywhere."

Papautsky, UC associate professor of electrical and computer engineering, is co-author of the Biomedical Devices-published research, "Lab-on-a-Chip Sensor for Detection of Highly Electronegative Heavy Metals by Anodic Stripping Voltammetry." Other co-authors are Erin Haynes, assistant professor of environmental engineering; William Heineman, distinguished research professor of chemistry; and just-graduated electrical and computer engineering doctoral student Preetha Jothimuthu, just-graduated chemistry doctoral student Robert Wilson, and biomedical engineering undergraduate research co-op student Josi Herren.

First Field Test of Sensor Expected in in Marietta, Ohio

One specific motivation for developing the sensor was an ongoing project by UC's Erin Haynes, who is studying air pollution and the health effects of manganese and lead in Marietta, Ohio. Manganese is emitted in that area because it is home to the only manganese refinery in the United States and Canada. Preliminary results from UC's Mid-Ohio Valley Air Pollution Study (M.A.P.S.) found elevated levels of manganese in Marietta residents when compared to those who live in other cities.

How the UC Sensor Works

The new UC sensor uses a technology called anodic stripping voltammetry that incorporates three electrodes: a working electrode, a reference electrode and an auxiliary electrode.

A critical challenge for such sensors is the detection of electronegative metals like manganese. Detection is difficult because hydrolysis, the splitting of a molecule into two parts by the addition of a water molecule, at the auxiliary electrode severely limits a sensor's ability to detect an electronegative metal.

To resolve this challenge, the UC team developed a thin-film bismuth working electrode vs. the conventional mercury or carbon electrode. The favorable performance of the bismuth working electrode combined with its environmentally friendly nature means the new sensor will be especially attractive in settings where a disposable lab-on-a-chip is wanted.

In addition, the UC team also optimized the sensor layout and working-electrode surface to further reduce the effects of hydrolysis and to boost the reliability and sensitivity in detecting heavy metals. The new sensor layout better allowed for its functioning, which consists of taking of a blood serum sample, stripping out the heavy metal and then measuring that heavy metal.

The end result is the first lab-on-a-chip able to consistently pinpoint levels of highly electronegative manganese in humans. The new sensor also exhibits high reliability over multiple days of use, with hours of continuous operation. With further developments, the chip may even be converted into a self-check mechanism, such as with glucose screening for diabetics.

Funding for this research has been provided by the National Institute of Environmental Health Sciences, the National Institute of Occupational Safety and Health Pilot Research Project Training Program and the University of Cincinnati.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by University of Cincinnati.

Journal Reference:

Preetha Jothimuthu, Robert A. Wilson, Josi Herren, Erin N. Haynes, William R. Heineman, Ian Papautsky. Lab-on-a-chip sensor for detection of highly electronegative heavy metals by anodic stripping voltammetry. Biomedical Microdevices, 2011; 13 (4): 695 DOI: 10.1007/s10544-011-9539-1

Fusion diagnostic sheds light on plasma behavior

 An instrument developed by researchers at the U.S. Department of Energy's Princeton Plasma Physics Laboratory (PPPL) has enabled a research team at a fusion energy experiment in China to observe--in startling detail--how a particular type of electromagnetic wave known as a radiofrequency (RF) wave affects the behavior of hot ionized gas.

In the experiment at EAST (the Experimental Advanced Superconducting Tokamak located at the Institute of Plasma Physics in Hefei, China), scientists employed a high-resolution, X-ray imaging crystal spectrometer (XICS) to observe how an RF wave changed the way a hot ionized gas known as a plasma moved in a vacuum vessel. Radiofrequency waves are similar to microwaves and are used to heat and drive current in plasma.

The experimenters already knew that the RF wave, also called a lower-hybrid wave, drives current in the plasma. What they found was that the lower-hybrid wave also caused the plasma to flow as a whole and at high velocities through the vacuum vessel, a property they refer to as toroidal rotation. The spectrometer provided a two-dimensional look at the plasma, recording data at a rate of about 50 frames a second. That's important because not all parts of the plasma move uniformly. For example, if the inner part of the plasma near the vessel's core is moving at a different rate -- or even in a different direction -- than the rest of the gas, researchers want to know those details. Understanding the plasma flows is vital because it could lead to better approaches to confinement.

The results were published in the June 6 edition of Physical Review Letters by researchers from the EAST team and PPPL's Manfred Bitter and Kenneth Hill. Bitter and Hill are experimentalists who have collaborated for more than 35 years.

"With plasmas, you are dealing with very high temperatures and flow velocities," Bitter said. "Those must be determined from the radiation emitted by the plasma." The spectrometer designed by Bitter and Hill measures both the plasma temperatures and flow velocities, and it appears to offer a window onto the world of fusion plasmas.

The observed plasma flow could be beneficial to progress in fusion research, according to the PPPL scientists. "ITER and future reactors cannot rely on the injection of neutral beams to impart momentum to the plasma and control the toroidal flow," Bitter said, noting that this is due to the scale of the experimental reactor presently under construction in France. ITER must rely on self-generated or RF-driven flow, meaning that this research is highly relevant to those projects.

The new spectrometer allows researchers to study self-generated and RF-driven flow with the goal to control it in future reactors so that plasmas can be more carefully contained.

The DOE Office of Science supports the spectrometer collaboration between the U.S. and the People's Republic of China (PRC) through the U.S.-PRC Fusion Cooperation Program. The spectrometer project includes researchers from EAST, PPPL, and the National Fusion Research Institute (NFRI) in Korea. Bitter and Hill helped design the instrument, which was installed on EAST.

X-ray crystal spectrometers measure the frequencies and intensities of X-rays emitted by plasma impurities. Researchers can identify the impurity by the pattern of frequencies, or spectrum, of the X-ray light emitted to help them determine the plasma ion temperature, as well as the rotational velocity of the bulk plasma, from the Doppler broadening and Doppler shift of an X-ray peak. "This Doppler shift or change in frequency is exactly the same phenomenon as the change in the pitch of a train horn as the train passes by an observer," Hill said.

The spectrometer designed by Bitter and Hill is made up of several components. It includes a "spherically bent crystal," a tiny piece of quartz that has been molded into a sphere. It also contains a two-dimensionally imaging X-ray detector and a beryllium window. EAST scientists have installed a second spectrometer on the tokamak based on the first spectrometer's design. Similar spectrometers designed by Bitter and Hill have been installed on experimental fusion machines in Korea and Japan, and at the Plasma and Fusion Science Center at the Massachusetts Institute of Technology, as well.

Researchers at PPPL, managed by Princeton University and funded by the DOE's Office of Science, collaborate with scientists around the world to develop fusion as an energy source for the world. Fusion is the process that powers the Sun and other stars. In the interior of stars, matter is converted into energy by the fusion, or joining, of the nuclei of light atoms to form heavier elements.

Story Source:

The above story is reprinted (with editorial adaptations ) from materials provided by DOE/Princeton Plasma Physics Laboratory.

Journal Reference:

Yuejiang Shi, Guosheng Xu, Fudi Wang, Mao Wang, Jia Fu, Yingying Li, Wei Zhang, Wei Zhang, Jiafeng Chang, Bo Lv, Jinping Qian, Jiafang Shan, Fukun Liu, Siye Ding, Baonian Wan, Sang-Gon Lee, Manfred Bitter, Kenneth Hill. Observation of Cocurrent Toroidal Rotation in the EAST Tokamak with Lower-Hybrid Current Drive. Physical Review Letters, 2011; 106 (23) DOI: 10.1103/PhysRevLett.106.235001