Quantification of internal phosphorus loading in polymictic lakes

摘要

Internal phosphorus (P) loading as P released from anoxic sediment surfaces often represents the main summer P load to lakes. Determining its exact quantity is not easy, especially in shallow polymictic lakes, because of an apparent lack of bottom water anoxia and simultaneous external loading. There are various procedures to determine internal load depending on available information. Nuernberg & LaZerte (2001) proposed three principally different procedures. 1. A partially net estimate from in situ summer increases 2. Net and gross estimates from complete P budgets (mass balance approach) 3. A gross estimate from anoxia (as the anoxic factor, AF in days per summer) in stratified lakes and P release (anoxic areal P release rate, RR in mg m~(-2) d~(-1)).