Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

City-grown air pollution is tougher on country trees

10.07.2003


CITY TREES VERSUS COUNTRY COUSINS. Dug up after a growing season in two kinds of air pollution, cottonwood trees show the retardant effects of ozone. From left, five city trees from the Bronx, where nitric-oxide pollution reduced the ozone exposure period; Cornell ecologist Jillian Gregg; and five country trees that grew in a high ozone rural environment in Riverhead, Long Island. Photo provided by Jilian Gregg. Copyright © Cornell University



NOT SO LUCKY. Examining tree growth in New York City, Cornell ecologist Jillian Gregg says low-ozone "footprints" in urban areas occur because high nitric-oxide concentrations scavenge ozone from the urban atmosphere. But rural areas aren’t so "lucky". These same nitric oxide compounds are one of the primary precursors that react to form high ozone concentrations that are blown to rural environments. Once there, nitric oxide is very low in concentration so ozone remains in the atmosphere for a longer period. While individual one-hour peak ozone concentrations are often higher in urban environments, the extended exposure period outside the urban center cause some rural trees to grow only half as fast as their city cousins. Photo provided by Jillian Gregg.Copyright © Cornell University


A tree grows in Brooklyn -- despite big-city air pollutants. Meanwhile, identical trees planted downwind of city pollution grow only half as well -- a surprising finding that ecologists at Cornell University and the Institute of Ecosystem Studies (IES) reported in the current issue of Nature (July 10, 2003). They attribute the effect to an atmospheric-chemistry "footprint" that favors city trees.

"I know this sounds counterintuitive but it’s true. City-grown pollution -- and ozone in particular -- is tougher on country trees," says Jillian W. Gregg, lead author of the Nature cover article, "Urbanization effects on tree growth in the vicinity of New York City." Other authors of the Nature report are Clive G. Jones, an ecologist at the Institute of Ecosystem Studies in Millbrook, N.Y., where some of the field studies were conducted, and Todd E. Dawson, professor of integrative biology at the University of California, Berkeley, and a professor at Cornell when the study began.

Gregg was a joint Cornell/IES graduate student, pursuing a Ph.D. in ecology, when she started planting identical clones of cottonwood trees (also known as poplars, or by the scientific name Populus deltoides ) in and around New York City. Test sites included the New York Botanical Garden and the Hunts Point water works in the Bronx; a Consolidated Edison fuel depot in Astoria, Queens; as well as Long Island’s Brookhaven National Laboratory in Upton; Eisenhower Park in Hempstead; and the Cornell Horticultural Research Laboratory in Riverhead. About 50 miles north of Manhattan, in the Hudson River valley, she also planted cottonwood clones at the Millbrook institute.



One aim of the study was to show the impact on plants of a tough life in the city, where a variety of gaseous, particulate and photochemical pollutants from fossil-fuel combustion bombard plants as they struggle to grow in heavy metal-laden soils. The fast-growing poplars were to serve as a kind of "phytometer" to gauge the net effect of urban and industrial pollutants on urban and rural ecosystems.

For three consecutive growing seasons Gregg returned to the sites to plant cottonwoods, harvesting them to weigh their biomass and to perform other kinds of analyses. She controlled for differences in light, precipitation, season length and soil factors, making air quality the primary factor of concern. The experimental cottonwoods growing in Queens and the Bronx "breathed" the same pollutants as did other plants (and people) in the boroughs. So did cottonwoods along the Hudson and on Long Island.

Unexpectedly, the city trees thrived. As reported in Nature , "…urban plant biomass was double that of rural sites." But in some areas of metropolitan New York City, as well as in other polluted cities, Gregg and her colleagues have found "footprints" of lower-than-expected ozone exposures. As Gregg explains the facts of atmospheric chemistry in the city, "Ozone is what we call a secondary pollutant. So while the primary precursors for ozone are emitted in the city, they must act in the presence of sunlight, over time, before ozone is formed. By then, the air mass has moved to rural environments."

The Big Apple air situation is even more complicated, Gregg notes, because the city is downwind from New Jersey, another densely populated and industrialized region. "A lot of the ozone moving into New York City was formed in the so-called Garden State," the ecologist says. However, the reactions of ozone formation are cyclical, with the presence of one of the primary precursors, nitric oxide (NO) -- which occurs in high concentrations in the urban atmosphere -- destroying ozone once it has formed. As new NO compounds develop, three-atom oxygen is reduced to the more benign, two-atom kind.

Ironically, NO concentrations are very low in most rural areas, so ozone remains in the atmosphere there and plants’ exposure period to the harmful gas is extended. (Although one-hour peak ozone exposures can be high in urban centers, exposure periods last longer in rural environments, resulting in higher cumulative exposures.) Trees and other plants growing within the lower cumulative ozone exposures of the urban-ozone footprints benefit from the NO scavenging reactions that reduce the ozone-exposure period. Trees growing in the purportedly clean rural areas aren’t so lucky.

The study was supported, in part, by the U.S. Environmental Protection Agency, the Edna Bailey Sussman Fund for Environmental Internships, the New York State Heritage Foundation, the Mellon Foundation , Cornell’s Department of Ecology and Systematics, the Institute of Ecosystem Studies, the Cornell Center for the Environment and Sigma Xi.

Roger Segelken | Cornell University
Further information:
http://www.news.cornell.edu/releases/July03/ozone_trees.hrs.html

More articles from Ecology, The Environment and Conservation:

nachricht Despite government claims, orangutan populations have not increased. Call for better monitoring
06.11.2018 | Deutsches Zentrum für integrative Biodiversitätsforschung (iDiv) Halle-Jena-Leipzig

nachricht Increasing frequency of ocean storms could alter kelp forest ecosystems
30.10.2018 | University of Virginia

All articles from Ecology, The Environment and Conservation >>>

The most recent press releases about innovation >>>

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

Im Focus: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

Epoxy compound gets a graphene bump

14.11.2018 | Materials Sciences

Microgel powder fights infection and helps wounds heal

14.11.2018 | Health and Medicine

How algae and carbon fibers could sustainably reduce the athmospheric carbon dioxide concentration

14.11.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>