Abstract
Concentrations of nitrate in deep seawater pumped up from 321 m in Toyama Bay were determined at an hour interval between September 2001 and March 2003 with a newly designed continuous fully-automated ion chromatography. Nitrate concentrations were usually around 24μM, but sometimes suddenly changed to 10.1 to 24.8μM for periods of several hours to several days. The decrease of nitrate concentration was found to be closely associated with temperature rise. It was thought that seawater masses having low nitrate concentration and high temperature might occasionally reach the inlet of the deep seawater intake pipe due to possible vertical and horizontal movements of seawater masses. Stormy weather in winter and typhoon in summer could be responsible for such seawater mass movements.
