Inorganic Phosphorus Species and Transfer Mechanisms in Soils to Sediments for Two Small Kansas Watersheds,

摘要

The soils of two small eastern Kansas rural watersheds and the sediments of their catchment basins were sampled during 1976and 1977. The objective of the study was to determine the nature of the chemical reaction products controlling orthophosphate availability as the sediments were subjected to varying conditions during their movement from the watershed and into the inundated soils of the basins. Samples were collected on the basis of soil use and drainage patterns. Sediments were obtained as undisturbed cores with a sampler developed during this research. Cores were frozen in liquid nitrogen upon collection and thawed just prior to sectioning and drying. Solubility criteria were used to identify the inorganic phosphate compounds in the samples. The eastern shore of one of the lakes had been fertilized with superphosphate for several years in an effort to increase the biomass. Within sediments of this lake,there was uniform availability of phosphate within strata. Intermediately stable octacalcium phosphate was found near the water-sediment interface with a shift toward hydroxyapatite in the deeper sediment layers. The smaller lake had recently been dredged. In this case it was found that in the acid lake sediments,which had been under reducing conditions, vivianite was the phosphate compound controlling phosphorus availability. By mapping the sample locations and the compounds,it was possible to follow changes in phosphorus availability throughout the watershed. A direct knowledge of the inorganic phosphate compounds present in the sediments and their relationship to the type of phosphorus compounds being added will be useful in the management of watersheds and the waters of their catchment basins.