Environmental Engineering Reference
In-Depth Information
E
F
D
G
B
H
A
B
E
G
C
A
K
B
M
C
K
J
euphotic
zone
J
I
LEGEND
A] Vegetation destruction by burial, overload and abrasion
B] Ash-leachate deposition and acidification
C] Heavy metal and fluorine poisoning
D] Increased surface albedo
E] Reduced evapotranspiration and soil moisture supply
F] Changes in cloud coverage (poorly constrained)
G] Increased surface runoff through vegetation burial and
ash-blanket emplacement
H] Clogging and changes to water courses
I] Light shading and euphotic zone shallowing from ash
deposition, ash resuspension and primary productivity
J] Physical impact of suspended ash particles
K] Increased primary production through ash fertilization
L] Enhanced carbon export by primary productivity
M] Carbon burial and preservation from ash deposition
N] Enhanced carbon export through ash settling
K
I
I
N
N
L
M
Figure 17.3 A schematic diagram illustrating the main terrestrial and oceanic
responses to volcanic ash deposition. A black and white version of this
figure will
appear in some formats.
For the colour version, please refer to the plate section
.
modifies its ability to interact with the atmosphere, altering microbial activity and
the breakdown of organic material.
The dissolution and release of ash-leachates can potentially cause acidi
ca-
tion and toxic conditions in affected environments (Blackford
et al
.,
1992
).
Ash-leachates are very soluble, dissolving within minutes of
first contact with
water. As the upper atmosphere does not support liquid H
2
O, much of these
surface coatings are still adsorbed to the particle surfaces upon deposition,
allowing rapid release into the surrounding environment (Duggen
et al
.,
2007
).
The subsequent dissolution of ash-leachates can have a strong impact on local
biota. Ecological sensitivity to ash-leachate dispersal depends on the chemistry
and volume of the ash-leachates and the ecosystem
'
s ability to buffer itself
from the effects. Systems with a low turnover rate, such as ponds, lakes and
soils, are particularly vulnerable to the remobilization of acids and toxic heavy
metals (
Figure 17.3B
; Frogner-Kockum
et al
.,
2006
). Some soils have the
capacity to buffer the effects of acid release (Delfosse
et al
.,
2005
); others can
experience microbial collapse and subsequent ecosystem stress (Kilian
et al
.,
2006
). Acids, such as HF, and heavy metals tend to accumulate in top soils
