Effect of pH, iron and humic acid on the estuarine behaviour of phosphate

Abstract
Processes controlling the estuarine behavior of phosphate were investigated using a model estuarine mixing system. Different phosphate vs. salinity profiles were produced when seawater was added to artificial freshwaters of various pH and concentrations of Fe, humic acid and phosphate. These profiles simulate observed phosphate behavior in real estuaries and are the result of a balance between phosphate adsorption onto colloidal Fe phases in the freshwater, subsequent colloidal aggregation, phosphate desorption and dilution with seawater. Changes of pH have a larger effect on phosphate behavior than do changes of salinity.