I completely believe that the Japanese authorities have downplayed the danger of Fukushima but at the same time if the radiation at the site is as bad as many say why are the trees not turning red like they did at Chernobyl?
How reliable are the tree colours as an indicator of how much radiation is coming out? If not much then what is different from Chernobyl where they turned red very quickly?
Quoting: Nano Bunny Chernobyl was a reactor core explosion and graphite fire.
Right but it was radiation which killed the trees and turned them red. Chernobyl was an explosion as you say and that is why they went red very very quickly but surely after 18 months at least the trees on site and around the site should have accumulated enough radiation to turn red if as much radiation has been released as many on here fear.
Comparing apples and oranges.
You might find this paper interesting.
The study doesn't deal with vegetation specifically but draws biological effects conclusions, nonetheless.
Study accepted June 1, 2012.
3.6 mb PDF
[
link to cricket.biol.sc.edu]
[snip]
There were significant differences between Fukushima and
Chernobyl in the nature of the disaster as well as the type and the
amounts of radionuclides that were released to the environment.
Currently, for terrestrial ecosystems, in Fukushima cesium-134 and
cesium-137 predominate (Kinoshita et al., 2011), while in Cher-
nobyl cesium-137, strontium-90, various isotopes of plutonium,
and americium-241 are found at biologically significant levels
across the landscape (Voitsekhovich et al., 2007), and differential
sensitivity to these mixtures could account for some of the differ-
ences in biological responses observed between sites.
Cesium 137, with a half-live of about 30 years, decays by beta
emission primarily to a meta-stable isomer of barium-137, which
is responsible for the gamma emissions of this isotope (Baum et al.,
2002). Thus if ingested, cesium-137 will generate both beta and
gamma doses for living organisms. Cesium-134 that has a half-life
of about 2 years is exclusively a beta emitter and is thus mainly a
concern if ingested.
Strontium-90, with a half-life of about 29 yrs, is almost a pure
beta emitter.
Most isotopes of plutonium are alpha emitters and are thus pri-
marily of concern if ingested. However, plutonium-241, which is
present to a significant degree in the Chernobyl region, has a half-
life of about 14 yrs, and decays via beta emissions to americium-241
(half life of 432 years), which in turn decays via alpha emissions
to neptunium-237, with gamma emissions as an additional by-
product.
Although handheld Geiger counters are likely to provide reli-
able measures of background contamination levels of radionuclides
for gamma sources, and to a lesser degree for beta emitters, if
the Geiger detector is in close proximity to the source, char-
acterization of alpha emitters usually requires more complex
measurement methods that are usually only tractable in a labora-
tory setting due to the short transmission distance of alpha particles
in air.
Given the different characteristics of radionuclides in the envi-
ronment at Fukushima and Chernobyl, field measurements of
contaminant levels are likely to underestimate biologically rel-
evant radiation levels in Chernobyl when the main exposure
pathway is via ingestion. Similarly, background radiation mea-
sures in the areas of Chernobyl closest to the reactor (e.g. the
Red Forest) are very likely to underestimate biologically rele-
vant doses given the abundance of alpha emitting actinides (e.g.
plutonium isotopes) that were differentially deposited in this
area.
