『Abstract
The influence of rock mineralogy, climate, vegetation and relief
on stream water composition and export as a result of weathering
is a major scientific concern both at the local scale, because
of the link between stream chemistry and biodiversity, and at
the global scale, in relation to global climate changes. Environmental
factors influencing stream chemistry at baseflow were studied
for 95 forested catchments located in the granite part of the
Vosges Mountains (NE France). Mean annual rainfall, slope, altitude,
catchment area, forest cover and granite composition were attributed
to each catchment using a geographic information system (GIS)
and spatially distributed databases. These variables were then
used to model stream water concentrations in SO4,
Ca, Mg, K, Na, Si, ANC (Acid Neutralizing Capacity) and pH via
linear regression analyses. Sulfate concentration is mainly negatively
correlated to the mean altitude of the catchment. Silica and Na
concentrations are strongly correlated and negatively related
to the mean annual rainfall and not to altitude. pH is positively
related to the sum of Ca, Mg and K, but not to SO4.
For any type of granite, Ca, Mg and pH are generally negatively
related to the mean annual rainfall, and positively related to
the catchment area. Calcium is best explained by the rock content
in hornblende, Mg by the rock contents of biotite and hornblende,
K by the content in K-feldspar. Nevertheless models differ for
each granite type, in relation to the availability of weatherable
minerals and, probably, to water pathways. This study shows the
interest of spatial analysis methods for understanding stream
water concentrations at the mountain range scale in combination
with local process studies and modelling at the catchment scale.
Keywords: Stream water chemistry; Acidification; Spatial analysis;
GIS; Weathering; Granite』
1. Introduction
2. Material and methods
2.1. The study area
2.2. Geological settings
2.3. Methods
3. Results
3.1. Stream water chemistry and environmental variables according
to granite type
3.2. Stream water composition according to the granite mineralogy
and environmental variables
4. Discussion
5. Conclusion
Acknowledgement
References