Input-output models - With special reference to the phosphorus loading concept in limnology

Abstract

Elementary mass balance and export models are explored in relation to eutrophication as caused by phosphorus and nitrogen. New criteria for phosphorus loading are given in relation to the ratio 'mean depth-water fill-in-time' {Mathematical expression}. The results suggest that lakes having long water renewal times are much more sensitive to phosphorus loading than would appear from mean depth only. Further, from comparison of the relative residence time of nitrogen and phosphorus, it is deduced that-with increasing eutrophication-the nitrogen metabolism is speeded up beyond the point of simple proportionality which would explain the transition from phosphorus to nitrogen limitation in highly eutrophied lakes. It is further suggested that the principles derived from eutrophication in regard to the metabolism of phosphorus and nitrogen in lakes are applicable also to other environmental compartments and stress factors. © 1975 Birkhäuser Verlag Basel.