『Summary
The variability of hydrologically induced mobilization of nitrate
during sequences of hydrological events in different seasons was
studied through high-frequency measurements of streamwater nitrate
concentrations accompanied by a detailed hydro-meteorological
monitoring system. The study was carried out in 2006, within the
42 km2 forested Padez（zの頭にv） watershed
in the southwestern part of Slovenia, which is characterized by
distinctive flushing, an almost torrential hydrological regime
influenced by impermeable flysch geological settings. More than
15 recorded hydrographs which, in the hydrological and biogeochemical
sense, differed substantially, disclosed a highly variable but
at the same time a strong linkage between hydrological and biogeochemical
controls of nitrate exports from the spatial perspective of a
watershed. During most of the hydrographs, with the exception
of early spring rainfall events, a positive relationship between
the nitrate concentration and discharge was observed with peak
nitrate concentrations having a time delay in the order of a few
hours after the hydrograph peaks. Peak nitrate concentrations
in periods of rainfall events span from 3.5 mg/l-N in late spring
to 14 mg/l-N in the case of the autumn hydrograph. However, the
dilution effect as a consequence of high event water contributions
was observed in certain events. The role of specific hydrological
events on the nitrate mobilization proved to be important as the
size of the accumulated nitrate pool available for mobilization
was large throughout most of the hydrographs. The biogeochemical
environment of the forest soils presumably drastically alters
the size of the available nitrate pool at the studied watershed
and, together with the specific hydrological conditions, shifts
the watershed from the flush-limited state in the late spring,
summer and autumn to the source-limited state in winter and early
spring.
Keywords: Watershed hydrology; High-frequency measurements; Forest
biogeochemistry; Streamwater nitrate; Nitrate flushing』
Introduction
Study area
Methods
Results
Hydrological events
Nitrate dynamics
Discussion
Seasonal variability in hydrological mobilization of nitrate
Runoff components and nitrate concentration dynamics
Hydrograph peak vs. peak nitrate concentration formation
Where does the nitrate come from?
Conclusion
Acknowledgements
References