3 research outputs found
Regionalisation of chemical variability in European mountain lakes
18 páginas, 6 tablas, 7 figuras.1. We carried out a coordinated survey of mountain lakes covering the main ranges across
Europe (including Greenland), sampling 379 lakes above the local tree line in 2000. The
objectives were to identify the main sources of chemical variability in mountain lakes, define
a chemical classification of lakes, and develop tools to extrapolate our results to regional
lake populations through an empirical regionalisation or upscaling of chemical properties.
2. We investigated the main causes of chemical variability using factor analysis (FA) and
empirical relationships between chemistry and several environmental variables. Weathering, sea salt inputs, atmospheric deposition of N and S, and biological activity in soils
of the catchment were identified as the major drivers of lake chemistry.
3. We tested discriminant analysis (DA) to predict the lake chemistry. It was possible to use
the lithology of the catchments to predict the range of Ca
2+
and SO4
2)
into which a lake
of unknown chemistry will decrease. Lakes with lower SO4
2)
concentrations have little
geologically derived S, and better reflect the variations in atmospheric S loading. The
influence of marine aerosols on lakewater chemistry could also be predicted from the
minimum distance to the sea and altitude of the lakes.
4. The most remarkable result of FA was to reveal a factor correlated to DOC (positively)
and NO3
)
(negatively). This inverse relationship might be the result either of independent
processes active in the catchment soils and acting in an opposite sense, or a direct
interaction, e.g. limitation of denitrification by DOC availability. Such a relationship has been reported in the recent literature in many sites and at all scales, appearing to be a
global pattern that could reflect the link between the C and N cycles.
5. The concentration of NO3
)
is determined by both atmospheric N deposition and the
processing capacity of the catchments (i.e. N uptake by plants and soil microbes). The
fraction of the variability in NO3
)
because of atmospheric deposition is captured by an
independent factor in the FA. This is the only factor showing a clear pattern when mapped
over Europe, indicating lower N deposition in the northernmost areas.
6. A classification has been derived which takes into account all the major chemical
features of the mountain lakes in Europe. FA provided the criteria to establish the most
important factors influencing lake water chemistry, define classes within them, and
classify the surveyed lakes into each class. DA can be used as a tool to scale up the
classification to unsurveyed lakes, regarding sensitivity to acidification, marine influence
and sources of S.Funding was provided by the European Union (EMERGE project EVK1-CT-1999-00032),
Spanish Ministry of Science and Technology (CICYT
grant REN2000-0889 ⁄GLO), and the Austrian Ministry
for Education, Science and Culture.Peer reviewe