Buffering of silica and phosphate in a turbid river1

The buffering of riverine dissolved silica and phosphate by sorption reactions between the aqueous phase and suspended sediment is examined with the turbid Colorado River system as a model. Concentrations are found to lie in a range predicted from laboratory sorption experiments with natural sediments and waters. Phosphate is probably highly buffered by suspended sediment during river flow while silica is not. Silica appreciably affects phosphate sorption reactions but not vice versa. Increased temperature results in higher silica but lower phosphate concentrations as a result of sorption. The buffering action of suspended sediments is largely complete within a few hours and is approximately proportional to the concentration of suspended sediment.