Measurement of biogenic silicon (BSi) in suspended matter and sediments is not simple because of the interference of lithogenic silicon (LSi) in the samples, particularly in coastal waters. We tested applicability and limits of a wet-alkaline digestion method for BSi analysis in suspended matter and sediments collected at Suo-nada, Seto Inland Sea.
For suspended matter, a digestion (using 1%Na2CO3) at 85 ℃ for 60 min was appropriate, and digestion for 120-180 min was suitable for sediments. We also tested the interference of alkaline solution to the Si analysis using by the molybdenum blue method. Dilution factor more than 5 times by MQ water or neutralizing the pH by 0.5N HCl was recommended for the method. By applying this method, a preliminary investigation on BSi in suspended matter at Suo-nada was conducted in April 2004.