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| Titel |
A high-resolution conceptual model for diffuse organic micropollutant loads in streams |
| VerfasserIn |
Christian Stamm, Mark Honti, Nico Ghielmetti |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250077436
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| Zusammenfassung |
| The ecological state of surface waters has become the dominant aspect in water quality
assessments. Toxicity is a key determinant of the ecological state, but organic micropollutants
(OMP) are seldom monitored with the same spatial and temporal frequency as for
example nutrients, mainly due the demanding analytical methods and costs. However,
diffuse transport pathways are at least equally complex for OMPs as for nutrients and
there are still significant knowledge gaps. Moreover, concentrations of the different
compounds would need to be known with fairly high temporal resolution because acute
toxicity can be as important as the chronic one. Fully detailed mechanistic models of
diffuse OMP loads require an immense set of site-specific knowledge and are rarely
applicable for catchments lacking an exceptional monitoring coverage. Simple empirical
methods are less demanding but usually work with more temporal aggregation and
that’s why they have limited possibilities to support the estimation of the ecological
state.
This study presents a simple conceptual model that aims to simulate the concentrations of
selected organic micropollutants with daily resolution at 11 locations in the stream network
of a small catchment (46 km2). The prerequisite is a known hydrological and meteorological
background (daily discharge, precipitation and air temperature time series), a land use map
and some historic measurements of the desired compounds.
The model is conceptual in the sense that all important diffuse transport pathways are
simulated separately, but each with a simple empirical process rate. Consequently, some
site-specific observations are required to calibrate the model, but afterwards the model can be
used for forecasting and scenario analysis as the calibrated process rates typically describe
invariant properties of the catchment.
We simulated 6 different OMPs from the categories of agricultural and urban pesticides
and urban biocides. The application of agricultural pesticides was also simulated with the
model using a heat-sum approach. Calibration was carried out with weekly aggregated
samples covering the growing season in 2 years. The model could reproduce the observed
OMP concentrations with varying success. Compounds that are less persistent in the
environment and thus have a dominant temporal dynamics (pesticides with a short half-life)
could be simulated in general better than the persistent ones. For the latter group the relatively
stable available stock meant that there were no clear seasonal dynamics, which
revealed that transport processes are quite uncertain even when daily rainfall is used as
the main driver. Nevertheless the daily concentration distribution could still be
simulated with higher accuracy than the individual peaks. Thus we can model the
concentration-duration relationship for daily resolution in an acceptable way for each
compound. |
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