Fukada et al.(2004)による〔『A dual-isotope approach to the nitrogen hydrochemistry of an urban aquifer』(709p)から〕

『都市の帯水層における窒素の水文化学的性質に対する二対の同位体アプローチ』


Abstract
 The potential for exploitation of urban aquifers is partly dependent on understanding the distribution and fate of urban N sources, such as sewage and fertilisers, that can limit the use of groundwater for public supplies. To investigate the application of the dual-isotope approach to understanding that N hydrochemistry of urban groundwater, this paper presents δ15N-NO3- and δ18O-NO3- data collected from two multi-level piezometers in the Sherwood sandstone aquifer beneath Nottingham in the English Midlands, UK. At one multi-level piezometer (Old Basford), depth sample measurements of δ15N-NO3- in the range +9.2 to +11.4‰ and δ18O-NO3- in the range +8.2 to +10.9‰, together with NO3- nitrate concentrations from 31.7 to 66.7 mg/l, are evidence for nitrification of sewage-derived inputs. In contrast, at the other multi-level piezometer (the Meadows), isotopically enriched samples (δ15N-NO3- in the range +24.3 to +42.2‰ and δ18O-NO3- in the range +20.5 to +29.4‰) are evidence for denitrification, although the compositional range of δ15N-NO3- does not identify the N source without corroborating data. For the Meadows location, a cross-plot of δ15N-NO3- versus δ18O-NO3- gave an enrichment of the 15N isotope relative to the 18O isotope by a factor of 1.9, within the range of 1.3-2.1 reported for denitrification in other studies. This study has shown that the dual-isotope approach provides improved understanding of N sources and fate in the urban environment but further work is required to identify nitrification pathways to provide more confidence in the application and interpretation of δ18O-NO3- measurements.』

1. Introduction
2. Study area
3. Methods and materials
4. Results and discussion
 4.1. Old Basford
 4.2. The Meadows
5. Conclusions
Acknowledgements
References


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