FORM OF DISSOLVED SILICON IN SEAWATER

Concentrations of dissolved silicon in 83 seawater samples obtained from various depths at seven stations in the North Pacific, the Japan Sea, and the Eastern China Sea were determined by the molybdenum blue method and by inductively coupled argon plasma atomic emission spectrometry. The silicon concentrations ranged from 0.6 to 169.0-mu-mol l-1 at the North Pacific stations, from 1.9 to 83.3-mu-mol l-1 at the Japan Sea stations, and from < 0.1 to 129.5-mu-mol l-1 at the Eastern China Sea stations. The concentrations obtained by the two methods were the same within experimental error, indicating that dissolved silicon is present in seawater as 'reactive silica'. Other silicon species cannot be present at concentrations higher than a few micromoles per liter.