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A close up of U. carpinifolia leaves
https://www.portlandoregon.gov/parks/article/479621?
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Since when are leave magnetized?
By: Andrea Semlow
Air pollution is a prominent concern in urban areas around the world. Dry regions in particular have higher particulate matter air pollution in high traffic areas. These high traffic areas are usually areas near streets with high vehicle density that kick-up dust containing heavy metals from brake systems and industrial facilities. These tiny airborne particles are highly hazardous because they can lead to lethal respiratory and cardiovascular diseases. Due to these pressing concerns, researchers have been searching for inexpensive, rapid air pollution monitoring techniques. Over the past twenty years, studies on tree leaves' ability to proxy as a bio-monitoring systems have resulted in a variety of new techniques. Tree leaves in urban and roadside areas have been proven to be good accumulators of atmosphere dusts. Recent studies have even shown that along with dust particles, leaves also accumulate magnetic particles. So leaves are magnetized, so what?
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A zoomed in
photo of a leaf surface
with arrows indicating magnetic particles.
http://www.academia.edu/7334220
/BIOMAGENTIC_MONITORING_OF_AIR_POLLUTION_USING_DUST_
PARTICLES_OF_URBAN_TREE_LEAVES_AT_UPPER_EGYPT
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Mohammad
Mehdi Sadeghian conducted a study in 2011 that utilized this magnetized quality
of leaves to find out the quantity and quality of vegetation in different areas
of Isfahan, Iran, specifically looking at the magnetic properties of Elm (Ulmus carpinifolia) leaves. His goal was
to determine if magnetic material on leaves could be a possible proxy to
monitor regional distribution of air particulate matter (PM) pollution. A close
up of the magnetic particles on a leaf surface is depicted on the right. The magnetic
particles associated with atmospheric particles arise from domestic heating,
vehicle exhaust and brake systems, and industrial facilities (Sadeghian et al
2011).This method is non-destructive, inexpensive, easily detected, and rapid. Sadeghian
collected from four spaces, a park, square, street, and control station, in
order to determine urban landscape areas with the highest density of air
pollutants. This method is unique because he has accounted for the leaf surface
composition change due to rain as well as water evaporation (Sadeghian et al
2011). Leaves from each site were collected and a magnetometer, an instrument
used for measuring magnetic forces, measured magnetized susceptibility with a
pulsed field (Sadeghian et al 2011). The study found the highest concentration
of magnetic properties were trees found in squares and streets. Streets had the
highest concentration of particles most likely because high traffic roads re-suspend
road dust resulting in higher magnetization of the U. carpinifolia leaves (Sadeghian et al 2011).
Future
use of this method will hopefully allow for cities to develop less expensive
monitoring systems; however, it appears this particularly approach would be quite
labor intensive. My potential future project would be in a similar vein utilizing
tree leaves as a bio-monitoring system, only a little closer to home in
Phoenix, Arizona. If you have never heard of a COTS monitoring system, it
stands for commercial off the shelf monitoring system. Basically a miniaturized
version of the really expensive air pollution monitor currently in place in
urban areas around the world. These devices will allow for more localized air
pollutant detection, increasing our knowledge of on the ground conditions in
cities. This will be extremely beneficial to updating the urban landscapes of
not only Phoenix, but numerous dry urban areas.
Reference: Sedeghian, M.M. (2011) “Biomonitoring of
particulate matter by magnetic properties of Ulmus carpinifolia leaves” African
Journal of Biotechnology 11 (73): 13827-13830.
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