May 18, 2009 -- Silently lining the roads, shading lush parks, and softening the hard angles of an urban landscape, trees seem passive garnish to a bustling, humming human society. But they are also sentinels, their leaves taking careful measurements of the microscopic particles of pollution that humans generate. They are so precise in this task that Barbara Maher and a group of scientists at the University of Lancaster in the United Kingdom are turning to them as reliable, street-level pollution monitors. Particulate air pollution is an insidious, deadly cocktail of chemicals leftover when power plants or car engines burn fossil fuels. Noxious compounds like volatile organic compounds (VOCs), polycyclic aromatic hyrdrocarbons (PAHs), and toxic heavy metals combine to form fine dust that inflames the lungs and invades the bloodstream, liver, even the brain when inhaled. Related Content:
Maher's team measured pollution based on magnetic signatures from tiny bits of iron in the particles. They found that lime trees scattered throughout Lancaster gradually collected particles over a period of seven to 10 days, until they accurately reflected ambient levels of pollution. Leaf samples were analyzed from 30 trees as a pilot study, but Maher sees every roadside tree in the city of 133,000 people as a pollution monitor. "We haven't measured all of the 1,650 trees, but we plan to," she said. "We're going to generate a map of particulate pollution for the whole of Lancaster." Maher will present the team's finding later this month at the American Geophysical Union's joint assembly in Toronto. Monitoring particulate pollution on small scales is crucial, because concentrations can fluctuate by a factor of 10 or more over a few city blocks. People living near a traffic light or busy intersection may therefore have much higher exposures to the toxins than those who live on a quiet street. Get More NewsSpiders, Scorpions Among World's Oldest CreaturesMany creepy crawlies have been on Earth much longer than previously believed.Blood-Sucking Vampire Bats Sing DuetsWhite-winged vampire bats "harmonize" with separated roost mates.Oldest Hebrew Writing Possibly FoundAncient inscriptions on a 3,000-year-old pottery shard could make history.Rare, Prehistoric-Age Reptile Found in N.Z.A tuatara has been spotted on the New Zealand mainland for the first time in 200 years.Iceman Has No Living RelativesOetzi, the 5,300 year-old frozen mummy, left no living genetic legacy.SLIDE SHOW: Landscapes of TerrorWhat makes a place feel scary? There are scientific explanations.It's Official: People Are Warming the PolesHumans are conclusively to blame for polar warming, say scientists.Eight-Armed Animal Preceded DinosaursWhat may be one of Earth's first animals was no bigger than a coaster and had eight arms.Phoenicians Live on in People's GenesOne in 17 Mediterranean men may be descended from ancient Phoenicians.Pesticides, Fertilizers Linked to Frog DeclineA pesticide is found to promote parasites among amphibians.Hubble Telescope Taking Photos AgainThe Hubble Space Telescope is once again snapping stunning photos of the universe.Andean Mummy Hairs Show Hallucinogen UseScientists find direct evidence of hallucinogenic drug use among ancient Andeans.Opals on Mars Reveal Planet's Long Wet PastOpals found on Mars suggest the planet has been wet for much longer. |
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