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| Titel |
Identifying nitrate sources and transformations in surface water by
combining dual isotopes of nitrate and stable isotope mixing model in a
watershed with different land uses and multi-tributaries |
| VerfasserIn |
Meng Wang, Baohong Lu |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140575
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| Publikation (Nr.) |
 EGU/EGU2017-3981.pdf |
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| Zusammenfassung |
| Nitrate is essential for the growth and survival of plants, animals and humans. However,
excess nitrate in drinking water is regarded as a health hazard as it is linked to infant
methemoglobinemia and esophageal cancer. Revealing nitrate characteristics and identifying
its sources are fundamental for making effective water management strategies, but nitrate
sources in multi-tributaries and mixed land covered watersheds remain unclear. It is difficult
to determine the predominant NO3− sources using conventional water quality monitoring
techniques. In our study, based on 20 surface water sampling sites for more than two years’
monitoring from April 2012 to December 2014, water chemical and dual isotopic approaches
(δ15N-NO3− and δ18O-NO3−) were integrated for the first time to evaluate nitrate
characteristics and sources in the Huashan watershed, Jianghuai hilly region, East China. The
results demonstrated that nitrate content in surface water was relatively low in the
downstream (<10 mg/L), but spatial heterogeneities were remarkable among different
sub-watersheds. Extremely high nitrate was observed at the source of the river in one of the
sub-watersheds, which exhibited an exponential decline along the stream due to dilution,
absorption by aquatic plants, and high forest cover. Although dramatically decline of
nitrate occurred along the stream, denitrification was not found in surface water by
analyzing δ15N-NO3− and δ18O-NO3− relationship. Proportional contributions of five
potential nitrate sources (i.e., precipitation; manure and sewage; soil nitrogen; nitrate
fertilizer; nitrate derived from ammonia fertilizer and rainfall) were estimated using
a Bayesian isotope mixing model. Model results indicated nitrate sources varied
significantly among different rainfall conditions, land use types, as well as anthropologic
activities. In summary, coupling dual isotopes of nitrate (δ15N-NO3− and δ18O-NO3−,
simultaneously) with a Bayesian isotope mixing model offers a useful and practical way to
qualitatively analyze nitrate sources and transformations as well as quantitatively
estimate the contributions of potential nitrate sources in surface water. With the
assessment of nitrate sources and characteristics, effective management strategies
can be implemented to reduce N export and improve water quality in this region. |
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