Equilibrium P Concentration Research Articles

Phosphate Adsorption‐Desorption Characteristics of Suspended Sediments in the Maumee River Basin of Ohio

AbstractPhosphorus (P) adsorption‐desorption characteristics of Maumee River Basin suspended sediments were compared with those of Basin soils and stream bottom sediments. Suspended sediment contained more total P than either soils or bottom sediments. The increase in total P over soils is attributed to enrichment of P in sediment by selective erosion of fine particles and adsorption of P during fluvial transport. The suspended sediment had higher adsorption maxima than Basin soils but lower than bottom sediments and had lower adsorption energies than either soils or bottom sediments. Calcite content of the suspended sediments was positively correlated with total P, EPC (equilibrium P concentration) and P desorbed and negatively correlated with adsorption energy, implying that, although calcite is a sink for P, the adsorption is weak compared with other sites for P adsorption such as hydrous oxides of Fe and Al.

Nature of Phosphorus Retention and Adsorption with Depth in Soil Columns

AbstractSequential fractionation of adsorbed 32P and changes in equilibrium P concentration (EPC) with depth were studied in a column leaching experiment. In general, the percentage of NH4Cl‐extractable P decreased rapidly with depth; the percentage of NH4F‐extractable P decreased rapidly in the initial 2‐cm depth and then remained fairly constant. Percentage NaOH‐extractable P increased as that of NH4F‐extractable P decreased, and that of H2SO4‐extractable P increased gradually with depth.Equilibrium P concentration (EPC) decreased with depth and increased as rate of P applied increased. These EPC values reflected both depth of penetration of applied P and level of native P in the soil.