simplistic idea that chemicals emitted to the atmosphere were somehow “diluted”
down to no-effect levels, i.e. virtually disappearing, research has shown that pollutants may undergo preferential accumulation. By entering the biogeochemical
cycles they can be directed to some particular sites where they accumulate to reach
significant concentration. This is worsened by the fact that humans have developed
a capacity to mobilise chemicals in amounts comparable to (or even much higher
than) the global natural fluxes. As a result, accumulated chemicals are not merely a
“footprint” of human actions, but they are present in large pools in the environment.
Examples of this are the accumulation of trace elements in Pyrenean lakes sediments, and the reactive nitrogen saturation exhibited by streams.
A second important notion is that these pools are a pollutant legacy that may not
be the ultimate fate of contaminants. Chemicals stored over time can be remobilised
and constitute a secondary source of delayed pollution. There is a legacy of pollution
that span not only over space, but also over time. The export of polluting lead
accumulated during millennia from catchments in the Pyrenees is an example of that.
Another important emerging idea is that there are synergistic effects caused
either by several pollutants or by the interaction between pollutants and climate
change. For instance, the combined effect of human nitrogen emissions together
with changes in natural emissions of phosphorus-bearing dust (with a possible
connection to climate changes) is changing the trophic status of Pyrenean lakes.
Such combined effects add complexity to the picture. Knowledge about multi-factor
synergistic and confounding effects is still missing, as well as on effects caused by
long-term chronic exposure to environmental doses of multi-pollutant mixtures.
And finally, there are also findings that bring some hope. Sulphate decline in
surface waters as recorded in the Pyrenees (and other sensitive areas worldwide)
suggests that perhaps it is not too naive to think that global actions are still possible
to preserve nature. Despite there is a hysteresis in the reversibility of acidification,
and that climate change has confounding (or even counteracting) effects on it, it
seems that recovery of ecosystems may proceed, provided that polluting emissions
are abated and sufficient time is allowed to natural processes to act. In this sense,
remote ecosystems such as high mountain catchments have a role not only as
warning systems, but also as indicators to assess the effectiveness of policies and
efforts for global conservation.
References
Bacardit M, Camarero L (2009) Fluxes of Al, Fe, Ti, Mn, Pb, Cd, Zn, Ni, Cu, and As in monthly
bulk deposition over the Pyrenees (SW Europe): the influence of meteorology on the
atmospheric component of trace element cycles and its implications for high mountain lakes.
J Geophys Res 114:G00D02
Bacardit M, Camarero L (2010) Atmospherically deposited major and trace elements in the winter
snowpack along a gradient of altitude in the Central Pyrenees: the seasonal record of
long-range fluxes over SW Europe. Atmos Environ 44:582–595
14 Atmospheric Chemical Loadings in the High Mountain: Current …
339
down to no-effect levels, i.e. virtually disappearing, research has shown that pollutants may undergo preferential accumulation. By entering the biogeochemical
cycles they can be directed to some particular sites where they accumulate to reach
significant concentration. This is worsened by the fact that humans have developed
a capacity to mobilise chemicals in amounts comparable to (or even much higher
than) the global natural fluxes. As a result, accumulated chemicals are not merely a
“footprint” of human actions, but they are present in large pools in the environment.
Examples of this are the accumulation of trace elements in Pyrenean lakes sediments, and the reactive nitrogen saturation exhibited by streams.
A second important notion is that these pools are a pollutant legacy that may not
be the ultimate fate of contaminants. Chemicals stored over time can be remobilised
and constitute a secondary source of delayed pollution. There is a legacy of pollution
that span not only over space, but also over time. The export of polluting lead
accumulated during millennia from catchments in the Pyrenees is an example of that.
Another important emerging idea is that there are synergistic effects caused
either by several pollutants or by the interaction between pollutants and climate
change. For instance, the combined effect of human nitrogen emissions together
with changes in natural emissions of phosphorus-bearing dust (with a possible
connection to climate changes) is changing the trophic status of Pyrenean lakes.
Such combined effects add complexity to the picture. Knowledge about multi-factor
synergistic and confounding effects is still missing, as well as on effects caused by
long-term chronic exposure to environmental doses of multi-pollutant mixtures.
And finally, there are also findings that bring some hope. Sulphate decline in
surface waters as recorded in the Pyrenees (and other sensitive areas worldwide)
suggests that perhaps it is not too naive to think that global actions are still possible
to preserve nature. Despite there is a hysteresis in the reversibility of acidification,
and that climate change has confounding (or even counteracting) effects on it, it
seems that recovery of ecosystems may proceed, provided that polluting emissions
are abated and sufficient time is allowed to natural processes to act. In this sense,
remote ecosystems such as high mountain catchments have a role not only as
warning systems, but also as indicators to assess the effectiveness of policies and
efforts for global conservation.
References
Bacardit M, Camarero L (2009) Fluxes of Al, Fe, Ti, Mn, Pb, Cd, Zn, Ni, Cu, and As in monthly
bulk deposition over the Pyrenees (SW Europe): the influence of meteorology on the
atmospheric component of trace element cycles and its implications for high mountain lakes.
J Geophys Res 114:G00D02
Bacardit M, Camarero L (2010) Atmospherically deposited major and trace elements in the winter
snowpack along a gradient of altitude in the Central Pyrenees: the seasonal record of
long-range fluxes over SW Europe. Atmos Environ 44:582–595
14 Atmospheric Chemical Loadings in the High Mountain: Current …
339