----- Original Message ----- From: "Karen Claxon" <kclaxon at earthlink.net> To: <ECOLOG-L at LISTSERV.UMD.EDU> Sent: Friday, June 28, 2002 4:12 PM Subject: Trees may contribute to ozone problem
> http://www.eurekalert.org/pub_releases/2002-06/tau-tmc062502.php
> Contact: Judith White
> jw at univrel.tamu.edu
> 979-845-4664
> Texas A&M University
>
> Trees may contribute to ozone problem
> COLLEGE STATION - Trees may not actually commit suicide, but
certain
> species do produce pollutants that hamper their own growth while
> contributing to global climate changes and causing harm to other
life
> forms, contend two Texas A&M University researchers.
> Renyi Zhang, an atmospheric chemist, is studying one such
substance,
> isoprene, given off by oak trees and leading to increased ozone
in our
> atmosphere. Working under a $300,000 grant from the National
Science
> Foundation, Zhang and chemistry professor Simon North have taken
on the
> challenge of unraveling the more than 1,000 reactions that
transform
> organically released isoprene into toxic atmospheric pollutants.
>
> "Air pollution is probably one of the most serious problems
facing
> humankind in the 21st century," said Zhang, a professor in the
College
> of Geosciences. "And certainly, much of that pollution results
from
> human activities. But most people are not aware of the role
played by
> chemical reactions which change substances produced by biogenic
species
> into harmful airborne pollutants.
>
> "Isoprene - C5H8 - is released by the respiration of oak trees
and is
> the second-most abundant naturally produced hydrocarbon (after
methane)
> in our atmosphere," he continued.
>
> "After a complicated series of chemical reactions, isoprene
facilitates
> ozone production, so increased isoprene means more ozone in the
air."
>
> Ozone in the upper atmosphere blocks out harmful ultraviolet
radiation
> from the sun, Zhang explained, but nearer the ground, it traps
infrared
> radiation reflected back up from Earth and contributes to
heating the
> air near the planet's surface, the so-called "Greenhouse
Effect." So,
> more ozone can mean rising temperatures near ground-level,
contributing
> to global warming.
>
> "Although near-ground ozone has some beneficial effects,
providing
> excited oxygen atoms needed to produce the free OH radicals that
help to
> bind other chemicals like sulfur and cleanse them from the
atmosphere,
> excess ozone proves harmful to the health of humans and plants,"
Zhang
> said. "For example, too much ozone can retard tree growth or
even kill
> trees. And if too many trees die, there will be more CO2 in the
air,
> further trapping heat and raising the temperature of the
planet."
>
> Zhang and North are studying isoprene oxidation related to oak
trees in
> the Houston area, where ozone is contributing to increasing air
> pollution. They are seeking to understand the critical reactions
out of
> the 1,000 in the isoprene to ozone chain in order to find ways
to abate
> air pollution and allow trees to continue their life-cycle
without
> increasing environmental damage.
>
> Zhang will be using laboratory apparatus to study isoprene using
> chemical ionization mass spectrometry, while North will look at
the
> chemical process using laser-induced fluorescence. Both
researchers also
> employ methods of quantum chemical calculation to analyze their
> experimental results. In addition to the NSF grant, their work
is being
> funded by the Welch Foundation, the Texas Advanced Research
Program
> (Chemistry) and the U.S. Department of Energy (DOE).
>
> "The isoprene chain reaction is very complicated - in fact, it's
been
> studied for over 30 years without significant results with
regard to
> fundamental details," said Zhang. "Dr. North and I seeking to
discover
> the direction in which reaction pathways proceed. If we can
fully
> understand the critical steps in the reaction, maybe we can
determine
> where best to intervene in the process to keep both our oak
trees and
> ourselves healthier."
>
>
> ###
> Contact: Judith White, 979-845-4664, jw at univrel.tamu.edu; Renyi
Zhang,
> 979-845-7656, zhang at ariel.met.tamu.edu
>
> (See, among others: Zhang, D., and R. Zhang, Unimolecular
decomposition
> of nitrooxyalkyl radicals from isoprene reaction with NO3, J.
Chem.
> Phys., 116, 9721-9728 (2002); and Zhang, D., R. Zhang, C.
Church, and
> S.W. North, Experimental study of hydroxylalkyl peroxy radicals
from
> OH-initiated reactions of isoprene, Chem. Phys. Lett., 343,
49-54
> (2001)).