Measuring biogenic silica in marine sediments

In the determination of biogenic silica (BSi) in marine sediments and suspe nded matter, a major difficulty is how to eliminate silica dissolved from n on-BSi compounds in the samples. To overcome this, many wet chemical method s 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 eli minates the interference of aluminosilicate compounds in the BSi determinat ion. The BSi content was estimated through linear regression of extracted S iO2 (Y-axis) plotted as a function of extracted Al2O3 (X-axis). There was a good linear relationship between the two elements. The regression extrapol ated to the Y-axis gives an intercept which can be regarded as the BSI cont ent of the sample. However, the coexistence of amorphous aluminosilicate re mains as a potential problem in the elimination of silica dissolved from th e lattice. (C) 2000 Elsevier Science B.V. All rights reserved.