Notice of RetractionNitrate Fate and Origin in a Typical Karst Subterranean River System, Southwest China

Notice of Retraction

After careful and considered review of the content of this paper by a duly constituted expert committee, this paper has been found to be in violation of IEEE´s Publication Principles.

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Groundwater in Qingmuguan subterranean river system was investigated using hydrogeochemistry and nitrogen isotope approaches to understand the nitrate fate and origin from November, 2007 to October, 2008. The results show that the karst aquifer was a highly inhomogeneous mixing system, which make the nitrate variation easy to be influenced by the natural changes and human activities, such as rainfall and agricultural fertilization. The nitrate concentrations of the subterranean river were higher in summer and autumn than those in winter and spring. The δ¹⁵N value of precipitation nitrate was 1.10⁰/₀₀, associated with vehicle NOx emissions. δ¹⁵N_NO3 value of surface runoff was 1.62⁰/₀₀, affected by both precipitation and fertilizers. δ¹⁵N_NO3 value of epikarst spring, lateral fissure water and cave drip-water were +4.60⁰/₀₀, +4.75⁰/₀₀ and +6.23⁰/₀₀, respectively, indicating their nitrate came from soil organic matters. δ¹⁵N_NO3 value (4.22⁰/₀₀) of the subterranean river suggested that the nitrate was derived mainly from the mixture of precipitation, surface runoff, epikarst water and the water filled in karst fissures and saturated zone. From July to next March, δ¹⁵N_NO3 values of +4.77⁰/₀₀±0.73⁰/₀₀ s- owed that the nitrate originated from soil organic matters, while values of +3.16⁰/₀₀±0.39⁰/₀₀ indicated that the nitrate derived from the mixture of fertilizers and soil organic nitrogen from April to June.