Fig. 4. Dissolution of reactive Si in samples of different river compartments after exposure to rain water during 24 hours (1440 min).

Results are expressed as percentage (%) of the total reactive Si (reported as mass of Si) in the samples [biogenic Si in grass and feces and alkaline-extractable Si (AlkExSi) determined with the continuous analysis method (42) for other samples] and are plotted as mean values (symbols) with SDs (error bars; n = 5). Series are fresh feces (order of hours old), dried feces (order of days old), old feces (order of weeks old), grass, sediment, and savannah soil.