Interpretation of Si concentrations in lake sediments: three case studies

The biogenic Si concentration in a sediment can be determined as the non-de trital Si concentration by normalization of the total Si concentration with Al. This procedure is based upon the assumptions that (1) that Al exists p redominantly in detrital, i.e. minerogenic, particles and (2) that biogenic Si (mainly diatom frustules) is the dominating non-detrital Si phase. This paper focuses on the reasons for the variations of the non-detrital Si con centration in these lake sediments. Data from three lakes are presented, re presenting three principally different cases regarding the Si concentration . The processes controlling the concentrations of detrital and non-detrital Si are discussed.