TY - GEN
T1 - Nutrient dynamics with groundwater-seawater interactions in a beach slope of a steep Island, Western Japan
AU - Onodera, Shin Ichi
AU - Saito, Mitsuyo
AU - Hayashi, Masaki
AU - Sawano, Misa
PY - 2007
Y1 - 2007
N2 - To confirm the semi-diurnal and seasonal variation in nutrient flux with the dynamics in groundwater-seawater interaction, we conducted intensive observations at 25 piezometers in a tidal flat over a distance of 100 m across a steep-sloped island. Based on the chloride balance, groundwater was very well-mixed with seawater under the tidal flat. Nitrate-nitrogen (NO 3--N) concentrations declined from >20 to near 0 mg L-1 along the groundwater flowpath from the hillslope to the tidal flat. In addition, nitrate concentrations in pore water of the tidal flat were lower (at 0.1 mg L-1) than in seawater. These results suggest that the reduction process of NO3--N occurred in both contaminated groundwater and seawater. Discharge of inorganic nitrogen by groundwater was confirmed offshore. The suspected source was nitrogen mineralization of organic compounds and seawater recirculation. Phosphorus was produced offshore and transported from the land area. Seasonal variations in nutrient dynamics at the tidal flat were also confirmed.
AB - To confirm the semi-diurnal and seasonal variation in nutrient flux with the dynamics in groundwater-seawater interaction, we conducted intensive observations at 25 piezometers in a tidal flat over a distance of 100 m across a steep-sloped island. Based on the chloride balance, groundwater was very well-mixed with seawater under the tidal flat. Nitrate-nitrogen (NO 3--N) concentrations declined from >20 to near 0 mg L-1 along the groundwater flowpath from the hillslope to the tidal flat. In addition, nitrate concentrations in pore water of the tidal flat were lower (at 0.1 mg L-1) than in seawater. These results suggest that the reduction process of NO3--N occurred in both contaminated groundwater and seawater. Discharge of inorganic nitrogen by groundwater was confirmed offshore. The suspected source was nitrogen mineralization of organic compounds and seawater recirculation. Phosphorus was produced offshore and transported from the land area. Seasonal variations in nutrient dynamics at the tidal flat were also confirmed.
KW - Groundwater
KW - Nitrate contamination
KW - Nutrient dynamics
KW - Recirculated seawater
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M3 - Conference contribution
AN - SCOPUS:55849139109
SN - 9781901502046
T3 - IAHS-AISH Publication
SP - 150
EP - 158
BT - IAHS-AISH Publication - A New Focus on Groundwater - Seawater Interactions
T2 - International Symposium: A New Focus on Groundwater - Seawater Interactions - 24th General Assembly of the International Union of Geodesy and Geophysics (IUGG)
Y2 - 2 July 2007 through 13 July 2007
ER -