Free Newsletters - Space News - Defense Alert - Environment Report - Energy Monitor
. Earth Science News .




BLUE SKY
Compact device has sensitive nose for greenhouse gases
by Staff Writers
Houston TX (SPX) Jan 24, 2014


The QEPAS sensor, seen in a Rice University lab, is capable of detecting trace amounts of methane and nitrous oxide. The portable unit was tested during NASA's recent DISCOVER-AQ survey of Houston air quality and proved itself the equal of far larger instruments. (Credit: Rice University Laser Science Group).

Rice University scientists have created a highly sensitive portable sensor to test the air for the most damaging greenhouse gases. The device created by Rice engineer and laser pioneer Frank Tittel and his group uses a thumbnail-sized quantum cascade laser (QCL) as well as tuning forks that cost no more than a dime to detect very small amounts of nitrous oxide and methane. The QCL emits light from the mid- to far-infrared portion of the spectrum.

That allows for far better detection of gases than more common lasers that operate in the near-infrared. The technique called quartz-enhanced photoacoustic absorption spectroscopy (QEPAS), invented at Rice by Tittel, Professor Robert Curl and their collaborators in 2002, offers the possibility that such devices may soon be as small as a typical smartphone. The Rice team's device was detailed this month in the Royal Society of Chemistry journal Analyst.

Tittel's team tested the small device at a Houston dump, and found it capable of detecting trace amounts of methane, 13 parts per billion by volume (ppbv), and nitrous oxide, 6 ppbv.

"Methane and nitrous oxide are both significant greenhouse gases emitted from human activities," Tittel said. "Methane is emitted by natural sources, such as wetlands, and human activities, such as leakage from natural gas systems and the raising of livestock.

"Human activities such as agriculture, fossil fuel combustion, wastewater management and industrial processes are increasing the amount of nitrous oxide in the atmosphere. The warming impact of methane and nitrous oxide is more than 20 and 300 times, respectively, greater compared to the most prevalent greenhouse gas, carbon dioxide over a 100-year period. For these reasons, methane and nitrous oxide detection is crucial to environmental considerations."

The small QCL has only become available in recent years, Tittel said, and is far better able to detect trace amounts of gas than lasers used in the past. Previous versions of the QCL are just as effective, but far too bulky for mobile use. What makes the technique possible is the small quartz tuning fork, which vibrates at a specific frequency when stimulated. "The ones we use are made for digital watches, and are very cheap," said Rice postdoctoral researcher and co-lead author Wei Ren.

"The fundamental theory behind this is the photoacoustic effect." The laser beam is focused between the two prongs of the quartz tuning fork. When light at a specific wavelength is absorbed by the gas of interest, localized heating of the molecules leads to a temperature and pressure increase in the gas. "If the incident light intensity is modulated, then the temperature and pressure will be as well," Ren said.

"This generates an acoustic wave with the same frequency as the light modulation, and that excites the quartz tuning fork. "The tuning fork is a piezoelectric element, so when the wave causes it to vibrate, it produces a voltage we can detect. That signal is proportional to the gas concentration."

The unit can detect the presence of methane or nitrous oxide in as little as a second, he said. To field test the device, the Rice team installed it on a mobile laboratory used during NASA's DISCOVER-AQ campaign, which analyzed pollution on the ground and from the air last September. (Results from DISCOVER-AQ were discussed in a meeting of air quality scientists at Rice in January.) The lab analyzed emissions from a Houston landfill, and the QEPAS sensor's findings compared favorably to the lab's much larger instrument, Tittel said.

"This was a milestone for trace-gas sensing," Ren said. "Now we're trying to minimize the size of the whole system." Tittel said smaller QEPAS device will be added this year to the mobile monitoring van currently carrying out a Rice/University of Houston survey of pollutants in the city.

Rice postdoctoral researcher Mohammad Jahjah is co-lead author of the paper. Co-authors include Rice graduate student Wenzhe Jiang and former Rice Laser Science Group members Przemystaw Stefanski, Rafat Lewicki, Jiawei Zhang and Jan Tarka. Tittel is the J.S. Abercrombie Professor in Electrical and Computer Engineering and a professor of bioengineering. Read the abstract here.

.


Related Links
Rice University
The Air We Breathe at TerraDaily.com






Comment on this article via your Facebook, Yahoo, AOL, Hotmail login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News





BLUE SKY
NASA: Cracked Sea Ice Stirs Up Arctic Mercury Concern
Pasadena CA (JPL) Jan 22, 2014
Vigorous mixing in the air above large cracks in Arctic sea ice that expose seawater to cold polar air pumps atmospheric mercury down to the surface, finds a NASA field campaign. This process can lead to more of the toxic pollutant entering the food chain, where it can negatively affect the health of fish and animals who eat them, including humans. Scientists measured increased concentrati ... read more


BLUE SKY
Indonesia increases maritime patrols

Mayor of scandal-hit Italy quake town withdraws resignation

UK charity expands Philippine anti-trafficking work

Tornadoes, flood, drought cost US billions in 2013

BLUE SKY
Google says buys artificial intelligence firm DeepMind

'Gears of War' videogame will stay in Xbox arsenal

MDA awarded key development work for exploration and communications

Lenovo to buy IBM's low-end server business for $2.3bn

BLUE SKY
War on lionfish shows first promise of success

WTO sets up panel to rule on Mexico-US tuna label feud

Great Lakes study dispels many misconceptions

Australia's drinking water at risk from extreme weather events

BLUE SKY
Arctic Warmth Unprecedented in 44,000 Years

North and Tropical Atlantic Ocean bringing climate change to Antarctica

Polar bear diet changes as sea ice melts

New sea anemone species discovered in Antarctica

BLUE SKY
Pathogenic plant virus jumps to honeybees

Hong Kong to cull 20,000 chickens after H7N9 found

Halting crop destruction in India saves up to $309 million

No-till soybean fields give (even some rare) birds a foothold in Illinois

BLUE SKY
More Precise Hurricane Forecasts with NASA-NOAA Suomi NPP VIIRS Satellite Sensor

New, younger age determined for the Grand Canyon

Two dead, 27 missing as flood engulfs Indonesia boat

"Sedimentary Bathtub" Amplifies Earthquakes

BLUE SKY
Chinese ivory smuggler in Kenya to test tough new law

Talks to end Mozambique skirmishes resume

Mozambique president inaugurates Chinese-built palace

Sudan warplanes hit rebel-held town: Kordofan insurgents

BLUE SKY
Putting 'Adam' in his rightful place in evolutionary history

Finland's education success opens new business niches

Blue eyes and dark skin, that's how the European hunter-gatherer looked

Calcium absorption not the cause of evolution of milk digestion in Europeans




The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement