Measuring biogenic silica in marine sediments

In the determination of biogenic silica (BSi) in marine sediments and suspended matter, a major difficulty is how to eliminate silica dissolved from non-BSi compounds in the samples. To overcome this, many wet chemical methods have been proposed and tested, but none have been completely acceptable. The dissolution processes of BSi, clay minerals and sediment were tested by alkaline solutions, and a more reasonable method was established which eliminates the interference of aluminosilicate compounds in the BSi determination. The BSi content was estimated through linear regression of extracted SiO2 (Y-axis) plotted as a function of extracted Al2O3 (X-axis). There was a good linear relationship between the two elements. The regression extrapolated to the Y-axis gives an intercept which can be regarded as the BSi content of the sample. However, the coexistence of amorphous aluminosilicate remains as a potential problem in the elimination of silica dissolved from the lattice.