環境

学術研究成果リスト

Detail of Grant Awarded Academic Researches

Project

Survey on denitrification in Tama R with the dissolved N2/Ar measurements

Academic
Research
No.320
Principal
Investigator
Keisuke Koba
Affiliation
(at that time)
Assistant Professor, Tokyo University of Agriculture and Technology
Research
Summary

Concentrations of dissolved N2, as well as the concentrations and isotopic ratios of nitrate, nitrite, ammonium and nitrous oxide were measured at 8 stations along Tama river. In addition, we measured the abundances of functional genes related with nitrification and denitrification, together with the characterization of dissolved organic matter. Denitrification and nitrification potentials for all stations were confirmed by the high functional gene abundances and labile components of dissolved organic matter. However, we could not detect the considerable excess N2 concentrations in river water of Tama river, implying that the occurrence of nitrous oxide reduction (the last step of the denitrification) was not strong. Isotopic data indicated that not denitrification but nitrification is the main source for the nitrous oxide in Tama river, which is quite useful information for the future planning of the nitrous oxide reduction in Tama river.

Our results indicate that the denitrification is not so active in Tama river although the setting for the occurrence of denitrification is almost satisfied. This, in turn, illustrates the importance of biotic uptake of nitrogenous compounds such as nitrogen uptake by periphyton in Tama river as a strong controller of the water chemistry. For the future reduction of nitrous oxide, which is the greenhouse gas and can destroy ozone layer, not the stimulation of the complete denitrification (i.e. nitrous oxide reduction) but the reduction of nitrogen load to Tama river itself, which can reduce mineralization and nitrification, will be the appropriate way based on our current results.


Collaborators

Nguyen Cong Thuan

Akiko Makabe

Yano Midori


Full Text