Using Lichens to Find Air Pollution Hot Spots

Lichen Training Manual 2010/2011(Good Neighbour Campaign/GNC, Environment Hamilton, 2010)

Also discussed here: Tree Lichen Monitoring - The Quick How-To Video (6 min You-Tube video, GNC)

And here: Arboreal Lichens:Preliminary Indicators of Hamilton Air Quality(48 page pdf, Dan McCarthy and Hague Vaughan, Upwind / Downwind Air Quality Conference, Hamilton, Ontario, 2004)

And here: Students Take Lead in City-Wide Pollution Study (MediaDesk, Hamilton-Wentworth District School Board, Jun. 6, 2011)

And here: Anthropogenic Environmental Aerosols:Measurements and Biological Implications(350 page pdf, Pierre Madl, PhD dissertation, University of Salzburg, Oct. 2009)

And here: Highway exhaust aerosols and their effects on alpine lichen populations(1 page pdf, Abstract, E. Heinzelmann, P. Madl and W. Hofmann, Anthropogenic Environmental Aerosols: Measurement and Biological Implications, 2009)

And here: Ecological Effects of Roads - A review(40 page pdf, Andreas Seiler, Introductory Research Essay No 9, Department of Conservation Biology, SLU, Uppsala, 2001)

 And here: Air Quality and Lichens - A Literature Review(Jenifer Hutchinson, Debbie Maynard, and Linda Geiser USDA Forest Service, Pacific Northwest Region Air Resource Management Program, Dec. 16,1996)

Today we review a project to analyse the air quality in a neighbourhood of Hamilton, Ontario, using a technique developed by George Sorger from McMaster University to link growth in two forms of lichen on maple or ash trees to air pollution levels. The preliminary results show the potential for identifying concentrations of air pollutants in an urban environment year by year without the need for expensive equipment or highly skilled technicians which are usually required.  

Key Quotes:

 “Our goal is to cover a great deal of the city in order to gain a greater understanding of the city’s pollution hotspots”

“Students used the methods of McMaster University biology professor emeritus Dr. George Sorger. Testing Ash and Maple trees, Sorger noted a link between lichen growth – specifically of greyish Physcia Millegrana and yellowish Candelaira Colcolor – and Sulphur Dioxide (SO2) and Nitrogen Dioxide (NO2) levels.”

“Areas with high SO2 and NO2 had low to non-existent levels of lichen; areas with low levels of SO2 and NO2 had high levels of lichen”

“Lichens are exposed to air pollutants at all times and, without any leafy bits that fall off, they cannot avoid the accumulation of pollutants. Without roots, lichens depend heavily on the air. This makes some lichen species great biomonitors of air quality and – because they grow slowly – monitoring is only required once a year.”

 “The process:

1. Indicate the street boundaries in which you will be canvassing.
2. Start to identify Maple and Ash Trees (see pg. 7-8) . Record their location.
3. Hold the wired quadrants up against the middle of the tree so that it is at eye level . The bottom being approximately1m above ground.
4. Beginning with one of the quadrants, check to see if the Millegrana species present. Use the scale of 0-3 to indicate the level that you see. Repeat for the rest of the 3 quadrants.
5. Repeat the same process for all cardinal directions/sides of the tree (North, East, South and West).
6. You should now have numbers for 16 quadrants (4 per side). Calculate the average and find the standard deviation. Repeat this process on the same tree for the Candelaria species.
7. Once done canvassing your area, take the average of all the trees and use that to find the standard error. Repeatfor the Candelaria species.
8. Send your information to the GNC Coordinator”

“results found lichen growth to be sparser in the industrial north end of the city, and more robust as monitors approached the Niagara Escarpment…The two different lichen species differed in their growth levels at the same sites; there were only modest levels of lichen in leafy Dundas, which may be due to a small sample size; and the Keith neighbourhood has little to no lichen, indicating a contaminated air shed”

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