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| Titel |
Modeling nitrogen loading in a small watershed in southwest China using a DNDC model with hydrological enhancements |
| VerfasserIn |
J. Deng, Z. Zhou, B. Zhu, X. Zheng, C. Li, X. Wang, Z. Jian |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 8, no. 10 ; Nr. 8, no. 10 (2011-10-28), S.2999-3009 |
| Datensatznummer |
250006169
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| Publikation (Nr.) |
 copernicus.org/bg-8-2999-2011.pdf |
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| Zusammenfassung |
| The degradation of water quality has been observed worldwide, and inputs of
nitrogen (N), along with other nutrients, play a key role in the process of
contamination. The quantification of N loading from non-point sources at a
watershed scale has long been a challenge. Process-based models have been
developed to address this problem. Because N loading from non-point sources
result from interactions between biogeochemical and hydrological processes,
a model framework must include both types of processes if it is to be
useful. This paper reports the results of a study in which we integrated two
fundamental hydrologic features, the SCS (Soil Conservation Service) curve
function and the MUSLE (Modified Universal Soil Loss), into a biogeochemical
model, the DNDC. The SCS curve equation and the MUSLE are widely used in
hydrological models for calculating surface runoff and soil erosion.
Equipped with the new added hydrologic features, DNDC was substantially
enhanced with the new capacity of simulating both vertical and horizontal
movements of water and N at a watershed scale. A long-term experimental
watershed in Southwest China was selected to test the new version of the
DNDC. The target watershed's 35.1 ha of territory encompass 19.3 ha of
croplands, 11.0 ha of forest lands, 1.1 ha of grassplots, and 3.7 ha of
residential areas. An input database containing topographic data,
meteorological conditions, soil properties, vegetation information, and
management applications was established and linked to the enhanced DNDC.
Driven by the input database, the DNDC simulated the surface runoff flow,
the subsurface leaching flow, the soil erosion, and the N loadings from the
target watershed. The modeled water flow, sediment yield, and N loading from
the entire watershed were compared with observations from the watershed and
yielded encouraging results. The sources of N loading were identified by
using the results of the model. In 2008, the modeled runoff-induced loss of
total N from the watershed was 904 kg N yr−1, of which approximately
67 % came from the croplands. The enhanced DNDC model also estimated the
watershed-scale N losses (1391 kg N yr−1) from the emissions of the
N-containing gases (ammonia, nitrous oxide, nitric oxide, and dinitrogen).
Ammonia volatilization (1299 kg N yr−1) dominated the gaseous N
losses. The study indicated that process-based biogeochemical models such as
the DNDC could contribute more effectively to watershed N loading studies if
the hydrological components of the models were appropriately enhanced. |
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