JpGU-AGU Joint Meeting 2017

Presentation information

[EE] Poster

A (Atmospheric and Hydrospheric Sciences) » A-HW Hydrology & Water Environment

[A-HW32] [EE] Biodiversity, nutrients and other materials in ecosystems from headwaters to coasts

Sat. May 20, 2017 5:15 PM - 6:30 PM Poster Hall (International Exhibition Hall HALL7)

[AHW32-P18] Estimation of recharge temperature, flow and denitrification in coastal groundwater, using dissolved gas.

*Yusuke Tomozawa1, Shin-ichi Onodera1, Mitsuyo Saito2, Daiki Aritomi3 (1.Graduate School of Integrated Arts and Sciences Hiroshima University, 2.Graduate School of Environmental and Life Science,Okayama University, 3.Yamaguchi prefectural government)

Nitrogen load to the groundwater by application of fertilizer in the farmlands has affected nitrogen cycle processes and water environment. Nitrate pollution occurs and denitrification process increases with producing N2 and N2O gas. In addition, recharge water in various altitudes converges in coastal groundwater and transports nitrate.

In this study, we examined to confirm recharge temperature, flow and denitrification in coastal groundwater, using dissolved N2 and Ar gas. Our study site is located on a small and steep catchment covered by citrus grove of Ikuchi Island in Hiroshima prefecture, western Japan. We collected groundwater samples at the observation wells with the depth of 3m, 10m, 15m, 20m, 30m and 40m. After collecting without mixing of air, dissolved N2 and Ar gas concentrations were analyzed by gas chromatography.

As a result, when the excessive amount of dissolved N 2 gas concentration was estimated from the groundwater temperature,
There was a negative correlation with dissolved oxygen content. It is thought that this is because denitrification · N 2 production is considered to be carried out so that there is less dissolved oxygen, suggesting the activity of anaerobic denitrifying bacteria.

This is also compatible with the results of previous studies, and it can be considered that the evaluation of denitrification state becomes possible by considering more diversely.