11:25 AM - 11:40 AM
[AHW23-09] Composition of ammonium nitrogen isotope in Oita Plain, eastern Kyushu Island, Japan
Keywords:Oita Plain, Hot spring water, Nitrogen isotope in Ammonium
To identify the composition of ammonium nitrogen isotope in hot spring water, the water samples from hot spring, as well as deep groundwater wells and surface spring, were collected from Oita city in Kyusyu island, Japan. Major dissolved ions were then analyzed from the collected samples, while the ammonium nitrogen isotope from the samples was determined by the ammonium diffusion method (Cao et al., 2018).
The Cl- and NH4-N concentrations in hot spring samples were detected ranging from 2506 to 19395 mg/L and 14.4 to 53.9 mg/L, respectively. The positive relationship between Cl- and NH4-N concentrations (R2=0.49) suggests the nitrogen load from deep-seated saline layers. The d15N-NH4 values of the hot spring range from -2.6 to +2.0 per mil. On the other hand, a relatively high isotopic value (+5.5 per mil) was detected in the groundwater sample collected from a deep tube well. These nitrogen isotope values showed relatively low values in high Cl- concentration (>13000mg/L) and high values samples in low Cl- concentrations. Similarly, the highest isotopic values obtained from the collected deep well samples were located close to the end-member of the trend line observed between Cl- concentration, and d15N-NH4 values. These results presumably suggest the origin of the ammonium nitrogen in hot spring as mixed water from deep-seated layer and surface layer.
Acknowledgment: This study was financially supported by Grants-in-Aid for Scientific Research (KAKENHI No.19H0199, PM: Takao Hirashima).
Reference: Thi Thuy Hai Cao et al. (2018) Effect of dissolved organic nitrogen contamination on d15N-NH4 determination in water samples by modification of the diffusion method with gas-phase trapping. Rapid Communications in Mass Spectrometry. DOI: 10.1002/rcm.8091
The Cl- and NH4-N concentrations in hot spring samples were detected ranging from 2506 to 19395 mg/L and 14.4 to 53.9 mg/L, respectively. The positive relationship between Cl- and NH4-N concentrations (R2=0.49) suggests the nitrogen load from deep-seated saline layers. The d15N-NH4 values of the hot spring range from -2.6 to +2.0 per mil. On the other hand, a relatively high isotopic value (+5.5 per mil) was detected in the groundwater sample collected from a deep tube well. These nitrogen isotope values showed relatively low values in high Cl- concentration (>13000mg/L) and high values samples in low Cl- concentrations. Similarly, the highest isotopic values obtained from the collected deep well samples were located close to the end-member of the trend line observed between Cl- concentration, and d15N-NH4 values. These results presumably suggest the origin of the ammonium nitrogen in hot spring as mixed water from deep-seated layer and surface layer.
Acknowledgment: This study was financially supported by Grants-in-Aid for Scientific Research (KAKENHI No.19H0199, PM: Takao Hirashima).
Reference: Thi Thuy Hai Cao et al. (2018) Effect of dissolved organic nitrogen contamination on d15N-NH4 determination in water samples by modification of the diffusion method with gas-phase trapping. Rapid Communications in Mass Spectrometry. DOI: 10.1002/rcm.8091