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Nitrate contamination in groundwater of the Yellow River Delta and its effect on the marine environment

Mitsuyo Saito¹, Shin-ichi Onodera², Kunihide Miyaoka³, Jianyao Chen⁴, Makoto Taniguchi⁵, Guanqun Liu⁶ & Yoshihiro Fukushima⁵

1 Graduate School of Biosphere Sciences, Hiroshima University, 1-7-1, Kagamiyama, Higashi-Hiroshima, Hiroshima, 7398521, Japan

misaito@hiroshima-u.ac.jp

2 Graduate School of Integrated Arts and Sciences, Hiroshima University, Japan

3 Faculty of Education, Mie University, Japan

4 School of Geography Sciences and Planning, Zhongshan University, China

5 Research Institute for Humanity and Nature (RIHN), Japan

6 College of Environmental Science and Engineering, Ocean University of China, China

Abstract The current condition of nitrate (NO₃^-) contamination in groundwater and its effect on the marine environment were evaluated in the Yellow River Delta, northeastern China. In the groundwater recharge area, NO₃^- contamination is suggested to be more severe compared with that in the groundwater discharge area. Also a relatively large amount of nitrogen is estimated to have accumulated in the aquifer of the recharge area. However, distribution of nitrate-nitrogen (NO₃^--N) concentrations and δ¹⁵N implied a denitrification process in the aquifer of the coastal area. In addition, a high rate of denitrification was indicated there by in situ experiments involving injected tracer water with high concentrations of NO₃^--N. Based on these results, it is suggested that a large amount of nitrate will be removed before it reaches the sea.

Key words Yellow River Delta; nitrate contamination; denitrification process; marine environment

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