Masashi Kodama

Field Observations of Sea-Salt Quantity Transported Landward by Winter Monsoon

Field observations of sea-salt quantity transported by winter monsoon have been performed on a reclaimed land facing Japan Sea. The landward transported sea-salt quantity and the deposit rate have been estimated quantitatively and the leeward profiles have been normalized by introducing representative scales. Especially, the normalization gives us a universal expression for the deposit rates by winter monsoon and Typhoon 9117. The transported sea-salt quantity decreases rapidly in the dimensionless distance less than 25 because of the settling of sea-salt particles. The representative scales introduced for the normalization depend strongly on the mean wind velocity at the height of 10m. The empirical expression for the deposit rates and the quantification of the representative scale enable us to predict the settling flux of sea-salt at an arbitrary place in the coastal area.

FIELD OBSERVATIONS ON NUTRIENT BUDGET IN WAJIRO TIDAL FLAT IN SUMMER

Tidal flat plays an important role in the water purification of a coastal region. In orderto investigate the nutrient budget on a tidal flat, field observations of water quality have been made on Wajirotidal flat at the east side of Hakata Bay in summer. The nutrient flux between sediment and seawater were estimated. Nutrients are removed from seawater in the daytime, and dissolved inorganic nitrogen and phosphate are released from sediment to seawater in the nighttime. The tidal flat functions as a sink for net budgets of nitrogen and phosphorus in the daytime, but as a source for phosphorus and as a sink for nitrogen in the nighttime. Since the uptake and release rates of nutrients per unit bed areadepend strongly on the quantity of solar radiation and DO concentration, they have spatial and temporal variations.