Nutrient dynamics with groundwater-seawater interactions in a beach slope of a steep Island, Western Japan

Shin Ichi Onodera, Mitsuyo Saito, Masaki Hayashi, Misa Sawano

Research output: Chapter in Book/Report/Conference proceedingConference contribution

7 Citations (Scopus)

Abstract

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.

Original languageEnglish
Title of host publicationIAHS-AISH Publication - A New Focus on Groundwater - Seawater Interactions
Pages150-158
Number of pages9
Edition312
Publication statusPublished - Dec 1 2007
Externally publishedYes
EventInternational Symposium: A New Focus on Groundwater - Seawater Interactions - 24th General Assembly of the International Union of Geodesy and Geophysics (IUGG) - Perugia, Italy
Duration: Jul 2 2007Jul 13 2007

Publication series

NameIAHS-AISH Publication
Number312
ISSN (Print)0144-7815

Other

OtherInternational Symposium: A New Focus on Groundwater - Seawater Interactions - 24th General Assembly of the International Union of Geodesy and Geophysics (IUGG)
CountryItaly
CityPerugia
Period7/2/077/13/07

Keywords

  • Groundwater
  • Nitrate contamination
  • Nutrient dynamics
  • Recirculated seawater

ASJC Scopus subject areas

  • Earth and Planetary Sciences(all)

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