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 Conservationists are sounding the alarm: parrots much more threatened than assumed
15.09.2017 | Justus-Liebig-Universität Gießen

nachricht A new indicator for marine ecosystem changes: the diatom/dinoflagellate index
21.08.2017 | Leibniz-Institut für Ostseeforschung Warnemünde

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: The pyrenoid is a carbon-fixing liquid droplet

Plants and algae use the enzyme Rubisco to fix carbon dioxide, removing it from the atmosphere and converting it into biomass. Algae have figured out a way to increase the efficiency of carbon fixation. They gather most of their Rubisco into a ball-shaped microcompartment called the pyrenoid, which they flood with a high local concentration of carbon dioxide. A team of scientists at Princeton University, the Carnegie Institution for Science, Stanford University and the Max Plank Institute of Biochemistry have unravelled the mysteries of how the pyrenoid is assembled. These insights can help to engineer crops that remove more carbon dioxide from the atmosphere while producing more food.

A warming planet

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Rainbow colors reveal cell history: Uncovering β-cell heterogeneity

22.09.2017 | Life Sciences

Penn first in world to treat patient with new radiation technology

22.09.2017 | Medical Engineering

Calculating quietness

22.09.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>