Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Missing chemical important to air pollution estimates

03.05.2004


Something is missing in the analysis of emissions of volatile organic compounds from a Michigan forest, and, according to a team of atmospheric scientists, what they do not know can have a large impact on air pollution in areas in and near forests.



"Organic compounds emitted by some trees play a role in ozone and aerosol production in the lower atmosphere," says Dr. William H. Brune, professor of meteorology and head of Penn State’s department of meteorology. "It appears that, at least in wooded areas, we have been underestimating the amounts of these chemicals produced."

The researchers were looking at the production of hydroxyl radical in the atmosphere. Volatile organic compounds like isoprene react with the hydroxyl radical resulting in the production of ozone and other chemicals. There has been some discrepancy between the actual measurement of hydroxyl radicals in the atmosphere and what the models predict.


"We developed a device that can measure the reactivity of hydroxyl radical in the air," says Brune. "Then we decided to measure everything in the atmosphere that reacts with the hydroxyl radical." The researchers reported the results of this experiment in today’s (April 30) issue of Science.

The researchers, who included Brune; Piero Di Carlo, a postdoctoral fellow from the Universita di L’Aquila in Italy who worked with Brune; Monica Martinez and Hartwig Harder, former post doctoral fellows, Robert Lesher, research assistant in electrical engineering, and Xinrong Ren, postdoctoral fellow, all at Penn State, measured the hydroxyl radical and the other chemicals in a forest in Northern Michigan at the University of Michigan Biological Station. The researchers took measurements from a tower above the canopy of a mixed transition forest of northern hardwood, aspen and white pine.

Over a two-year period, the researchers also collected a wide array of data on the area including temperatures, chemical constituents and where the air masses came from.

"When we measured an air mass coming from Detroit, we found all the urban pollutants one would expect, but we also found that the levels of chemicals were not dependent upon local temperature profiles," says Brune. "The urban readings were flat with respect to temperature change."

But the researchers found that chemicals in air masses that came from the forested area did change with a change in temperature. Forest-generated emissions change a lot with temperature.

Isoprene is the forest-generated chemical with the largest piece of the emission pie, but it is only produced during daylight. Other chemicals, particularly larger terpenes, are produced around the clock and are also temperature sensitive.

"We think we measured all major components of the hydroxyl radical reactants, but there is something still unaccounted for," says Brune. "We know that something we cannot identify is reacting with the hydroxyl radicals and we know it is temperature dependent and not light dependent. We just do not know what it is."

This missing substance is not trivial. It makes up a fourth to a third of the reactants, with the hydroxyl radical in the forest, which is significant. Because it is temperature sensitive, and is seen in both clean and polluted air at the forest site, it is forest-generated, not city-generated.

"We followed up the Michigan experiment with one in Houston," says Brune. "There we saw all the expected compounds from cars, oil refining, asphalt and burger joints, but the hydroxyl reactivity was not temperature dependent. We could account for all the hydroxyl reactivity." In New York City and Nashville as well as Houston, no temperature dependency was found.

Because hydroxyl radicals play an important part in the production of tropospheric ozone and are key in many of the chemical reactions that break down pollutants in the atmosphere, understanding exactly how much hydroxyl radical is actually in the atmosphere is important for measuring and predicting pollution levels. If researchers are consistently underestimating the volatile organic compounds generated by forests, their analysis of the environment, especially in cities surrounded by forests, will be incorrect.

Applying environmental regulations and assessing pollution levels becomes very difficult with incomplete information.

The researchers note that, "New, more specific and more sensitive detection techniques will likely be required to determine the identity of the biologically produced volatile organic compounds responsible for the missing hydroxyl radical reactivity and the reason they have not yet been detected."

This work was part of the PROPHET 1998 and PROPHET 2000 campaigns and was funded by the National Science Foundation, the National Oceanographic and Atmospheric Agency and the U.S. Environmental Protection Agency.

Other researchers involved in the project were Troy Thornberry, Coleen Campbell and Mary Anne Carroll, University of Michigan; Valerie Young, Ohio University; Paul B. Stepson, Purdue University; Daniel Rammer, University of Miami, and Eric Apel, NOAA.

A’ndrea Elyse Messer | EurekAlert!
Further information:
http://www.psu.edu/

More articles from Earth Sciences:

nachricht Novel method for investigating pore geometry in rocks
17.06.2018 | Kyushu University, I2CNER

nachricht Decades of satellite monitoring reveal Antarctic ice loss
14.06.2018 | University of Maryland

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

A sprinkle of platinum nanoparticles onto graphene makes brain probes more sensitive

15.06.2018 | Materials Sciences

100 % Organic Farming in Bhutan – a Realistic Target?

15.06.2018 | Ecology, The Environment and Conservation

Perovskite-silicon solar cell research collaboration hits 25.2% efficiency

15.06.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>