Geology Reference
In-Depth Information
monomeric aluminium that has been identified as the toxic agent for fish
which, in acidified lakes and streams at aluminium concentrations of
100-200 mgL
1
, are unable to maintain their osmoregulatory balance
and are susceptible to respiratory problems from coagulation of mucus
and Al(OH)
3
on their gills at their physiological pH of 7.2.
44
In response to a decline in acid deposition as a result of improved
atmospheric emission controls, there was a significant decline from the
early 1980s to the late 1990s in the concentrations of both inorganic and
organic monomeric aluminium in soil solutions draining from mineral
soils and in stream water in New Hampshire, USA (Figure 3).
45
These
decreases in aluminium concentration were accompanied by decreases in
SO
4
2
concentrations, but there was only a modest increase in stream
water acid-neutralizing capacity and no change in pH. The hydroxyla-
tion of aluminium appears to have been critical in buffering stream
waters against such increases. In a survey of Adirondack lakes in the
north-eastern USA, however, Driscoll and co-workers measured a
Figure 3 Long-term declines in sulfate concentrations mitigate the mobilization of
aluminium in soil solutions and stream water in the Hubbard Brook Experi-
mental Forest, New Hampshire, USA.
45
a-c, annual volume-weighted concen-
trations of a, inorganic monomeric aluminium (Al
i
); b, organic monomeric
aluminium (Al
o
); and c, sulfate (SO
4
2
) in mineral soil solutions at 750 m (
K
)
and 730 m (
J
), and in stream water (triangles)
(Reprinted with permission from ref 45,
r
Macmillan Publishing, 2002)
