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| Titel |
A model-based assessment of the potential use of compound-specific stable isotope analysis in river monitoring of diffuse pesticide pollution |
| VerfasserIn |
S. R. Lutz, H. J. van Meerveld, M. J. Waterloo, H. P. Broers, B. M. van Breukelen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 17, no. 11 ; Nr. 17, no. 11 (2013-11-14), S.4505-4524 |
| Datensatznummer |
250085995
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| Publikation (Nr.) |
 copernicus.org/hess-17-4505-2013.pdf |
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| Zusammenfassung |
| Compound-specific stable isotope analysis (CSIA) has, in combination with
model-assisted interpretation, proven to be a valuable approach to quantify
the extent of organic contaminant degradation in groundwater systems. CSIA
data may also provide insights into the origin and transformation of diffuse
pollutants, such as pesticides and nitrate, at the catchment scale. While
CSIA methods for pesticides have increasingly become available, they have
not yet been deployed to interpret isotope data of pesticides in surface
water. We applied a coupled subsurface-surface reactive transport model
(HydroGeoSphere) at the hillslope scale to investigate the usefulness of
CSIA in the assessment of pesticide degradation. We simulated the transport
and transformation of a pesticide in a hypothetical but realistic
two-dimensional hillslope transect. The steady-state model results
illustrate a strong increase of isotope ratios at the hillslope outlet,
which resulted from degradation and long travel times through the hillslope
during average hydrological conditions. In contrast, following an extreme
rainfall event that induced overland flow, the simulated isotope ratios
dropped to the values of soil water in the pesticide application area. These
results suggest that CSIA can help to identify rainfall-runoff events that
entail significant pesticide transport to the stream via surface runoff.
Simulations with daily rainfall and evapotranspiration data and one
pesticide application per year resulted in small seasonal variations of
concentrations and isotope ratios at the hillslope outlet, which fell within
the uncertainty range of current CSIA methods. This implies a good
reliability of in-stream isotope data in the absence of transport via
surface runoff or other fast transport routes, since the time of measurement
appears to be of minor importance for the assessment of pesticide
degradation. The analysis of simulated isotope ratios also allowed
quantification of the contribution of two different reaction pathways
(aerobic and anaerobic) to overall degradation, which gave further insight
into the transport routes in the modelled system. The simulations supported
the use of the commonly applied Rayleigh equation for the interpretation of
CSIA data, since this led to an underestimation of the real extent of
degradation of less than 12% at the hillslope outlet. Overall, this
study emphasizes the applicability and usefulness of CSIA in the assessment
of diffuse river pollution, and represents a first step towards a
theoretical framework for the interpretation of CSIA data in agricultural
catchments. |
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