Master of Arts (MA)
Geography & Environmental Studies
Faculty of Arts
The quantitative phosphate adsorption behaviour of ten grain size fractions of an experimental sediment (silica sand) and fluvial sediment from two Southwestern Ontario rivers, were evaluated and compared to determine the effect of particle size on phosphate absorption. In addition, the elemental composition of grain size fractions of fluvial sediment were determined by X-Ray fluorescence spectrometry to study the combined effect of particle size and sediment geochemical composition on phosphate adsorption. Results of the adsorption studies indicate that phosphate adsorption per unit mass increases in non-linear fashion with decreasing grain size. The capacity of grain size fractions of silica sand and river sediment to adsorb phosphate can be categorized into three phosphate adsorption groups according to particle size. From the poorest to the most efficient phosphate adsorption group, these groups are 1) medium sand to coarse silt, 2) medium to fine silt and 3) clay size particles. In addition to grain size, sediment geochemical composition and grain mineralogy are important parameters which influence phosphate adsorption. Increased phosphate adsorption activity in the smaller particle sizes was apparently due to the presence of metal oxides (Al, Fe, Mn and Ti) associated with clay minerals and organic material. Although small grain sizes (<23µm) adsorbed more phosphate than larger grain size fractions, the smaller fractions are also capable of desorbing large amounts of phosphate into solution. Therefore the smaller fractions may act as a phosphate source during times when the phosphate concentration of a river is below the sediment equilibrium phosphate concentration.
Stone, Michael F.A., "The effect of particle size on phosphate adsorption by fluvial sediment" (1987). Theses and Dissertations (Comprehensive). 303.