22
BAMOS
Mar 2020
Blue haze
Priya Mohandoss
Priya has a Bachelor of Science, a Master of Journalism
and a Masters of Communications and Media Studies from
Monash University.
While travelling through the Yarra Ranges in Victoria, be it
the winding road from St Andrews to Kinglake or a stretch of
the Melba Highway, you will most likely notice a bluish haze
resonating from the mountains above. This phenomenon
happens as a result of the emission of biogenic volatile organic
compounds (BVOCs) that are released from the abundance of
eucalyptus in these areas. Consequently, when the oils from this
genus, dust particles and water vapour combine and then react
with sunlight, a scattering of short wavelengths are produced,
creating an optical illusion, causing a blue colour to appear in
the atmosphere (Littman, 2018).
The BVOC that is the source of this reaction is called isoprene
and it is a major chemical in trees. Globally, trees and shrubs
are able to release over 500 million tonnes of isoprene per
year and in Australia, eucalypts emit one of the highest levels
of this chemical into the surrounding air. (Matos et al., 2015). It
is biogenic in character as it comes from living organisms or is
formed through biological processes.
Apart from being a natural air pollutant and the main
component in the composition of photochemical smog,
isoprene also acts as a defense mechanism in plants. As a result,
it is capable of deterring insects and also shields plants from
other hazards, such as heating, as this can create havoc for the
process of photosynthesis (Visakorpi, et al., 2018).
In general, BVOCs vary in their method of emission processes.
Some of the chemicals are found inside the tissues of plants that
are kept insulated from the atmosphere and are only released
when there is some form of tissue damage (Ciccioli et al.,
1999). Other compounds, kept within structures are regularly
Article
Blue haze from eucalyptus forest in the Yarra Valley region.
Source: Priya Mohandoss
Fun fact: the Blue Mountains in New South
Wales got their name from this phenomenon
transmitted into the open air. In addition to this, some BVOCs
spread after being made instead of being stored. This reaction
oocurs in order to counteract stress or in certain environmental
events such as bushfires. (Dudareva et al., 2006).
While we are fortunate enough to witness the beauty of this
blue haze, we also must acknowledge its perils too.
References
Ciccioli, P., Brancaleoni, E. and Frattoni, M. et al., 1999. Emission
of reactive terpene compounds from orange orchards and their
removal by within‑canopy processes, Journal of Geophysical
Research D, 104, 8077–8094.
Dudareva N., Negre F., Nagegowda D.A., and Orlova I., 2006.
Plant volatiles: recent advances and future perspectives, Critical
Reviews in Plant Sciences, 25, 417–440.
Littman, G. “Why does Australia burn?” Opinions, Bilan, October
29 2013. Accessed February 19, 2020. https://www.bilan.ch/
opinions/garry-littman/why_does_australia_burn_
Matos, C.T., Gouveia, L., Morais, A.R.C., Reis, A. and Bogel‑Łukasik,
R., 2015. Green metrics evaluation of isoprene production by
microalgae and bacteria. Green Chemistry, 17, 1318–1318.
Visakorpi, K., Gripenberg, S., Malhi, Y., Bolas, C., Oliveras, I.,
Harris, N., Rifai, S. and Riutta, T., 2018. Small‐scale indirect plant
responses to insect herbivory could have major impacts on
canopy photosynthesis and isoprene emission. New Phytologist,
220, 799–810.