MIRTHE Tests Air Quality in Beijing

The Summer 2008 in Beijing will become a testbed for MIRTHE's air quality monitoring systems.

One prototype system is the Quantum Cascade Laser Open Path System (QCLOPS), which employs mid-infrared light technology to monitor ozone, ammonia and carbon dioxide. Mid-infrared light sources have major advantages compared to lasers operating at other wavelengths for monitoring trace gases that are important for air quality and climate.

QCLOPS works by transmitting laser radiation through the air, which is then reflected back by a retro-reflector to a detector. It uses tunable, thermoelectrically cooled, pulsed Daylight Solutions quantum cascade lasers and is designed for monitoring multiple trace gases in the air.

“We are designing a field deployable quantum cascade laser-based sensor system,” said Anna Michel, postdoctoral associate at MIRTHE, and part of the scientific team finalizing the development of QCLOPS. “It is an open-path sensor and this is proof-of-concept work. The eventual goal is to build smaller, cheaper sensors that can be deployed in sensor networks. We are also linking urban air quality with regional climate. We want to use instruments like QCLOPS to obtain data for models—combine sensor measurements with modeling.”

The second system is an extractive single point nitric oxide sensor. The point sensor system is based on widely tunable mid-IR quantum cascade laser developed by MIRTHE scientists.

“The measurement technique employed, called Faraday rotation spectroscopy, uses unique paramagnetic properties of nitric oxide,” said Gerard Wysocki, Professor of Electrical Engineering at Princeton University, who leads the NO-sensor project. “This allows excellent detection limits at sub-parts-per-billion levels together with very high selectivity and immunity to interfering molecular species that possess strong absorption bands in the same spectral region such as water vapor.”

The instrument is fully automatic and autonomous and will be deployed in a field test setting in Beijing for continuous atmospheric NO monitoring over the summer. Detection of NO is of great interest in both environmental and industrial applications in which NO as a product of fossil fuel combustion processes is an environmental pollutant that is of great importance for atmospheric chemistry studies.
NO is one of the precursor molecules in acid rain formation and contributes to ozone layer depletion. Moreover, NO plays an extremely important role in biomedical applications.

In 1998 Robert F. Furchgott, Louis J. Ignarro and Ferid Murad received the Nobel Prize in Physiology or Medicine for their discoveries concerning nitric oxide as a signaling molecule in the cardiovascular system.

“After the environmental tests in Beijing, the MIRTHE technology is planned to be further developed and adopted to biomedical applications, such as detection of NO in human breath,” Wysocki said. “This is a very promising diagnostic tool for various human disease states, for example, asthma.”
This month, the QCLOPS and point sensor research teams are heading for Beijing for their first-ever field experiments deployed in an international arena.

MIRTHE researchers will work closely with the team of Professor Zifa Wang at the Nansen-Zhu International Center of the Institute of Atmospheric Physics (IAP). IAP is studying and understanding how urban aerosols influence local weather and public health through coupled modeling and monitoring analyses.

“The Beijing testbed is an early and crucial manifestation that MIRTHE is fulfilling its mission to address important societal needs, in this instance in air quality monitoring, on a global scale,” said Professor James Smith, MIRTHE co-director and professor of Civil and Environmental Engineering at Princeton University. “The Beijing testbed has an added benefit of deploying in close proximity to the many established technologies (such as mass spec, gas chromatography, FTIR, that are more expensive, bulkier, process with long measurement periods—or in batch mode—and require extensive calibration and maintenance) that will be monitoring air quality in Beijing. This will allow MIRTHE to benchmark its performance and establish its competitive advantage over these existing technologies and monitoring systems.”

“Industry is actively involved in MIRTHE, helping to grow lasers (e.g., Maxion) and providing working mid-IR sensing systems based (Daylight Solutions) on MIRTHE Quantum Cascade Laser designs,” Montemarano said. “These and other MIRTHE industry partners will play an active role in helping to take this testbed demonstration into a compelling business case for the rapid commercialization of MIRTHE technology.”

Through its core and innovation breakthrough research projects, MIRTHE seeks to advance technologies that will take precision trace gas sensing from complicated and expensive laboratory systems to compact, easy-to-use devices, inexpensive enough to be widely deployed.

“Being able to make smaller, cheaper and highly sensitive sensors will have broad applications and will enable scientists to better understand things such as the effect of pollution on air quality or to see how we are impacting our environment with emissions from factories,” Michel said. “With portable sensors, measurements can be made in more locations and can more easily be set up in arrays of multiple sensors. This will facilitate broad use by industry, government and the research community.”

For additional information, please contact:

Joseph X. Montemarano
Managing Director/Industrial Liaison
NSF-ERC MIRTHE, www.mirthecenter.org
Princeton University

[email protected]

Steven Schultz
Director of Engineering Communications
School of Engineering and Applied Science
Princeton University
609-258-3617 - office
609-751-4480 - cell
[email protected]