Chapter 3.2 The Phosphorus Cycle: Quantitative Aspects and the Role of Man

Abstract

This chapter summarizes the main fluxes of the global phosphorus cycle and discusses the major phosphorus reservoirs. Man's transport of phosphate rock, fertilizers, meat, and cereals are of importance on a global scale, as these transports tend to concentrate phosphorus in geographically limited areas where large problems on a regional and local scale may develop. In the modern industrialized environment, man's tendency to accumulate creates a problem of a different magnitude. Regionally, man's impact on the phosphorus cycle is expressed primarily in aquatic systems. The freshwater ecosystem is very sensitive to additions of phosphorus and reacts to phosphorus additions with increased production of plants and algae. These increased amounts of plant material use large amounts of oxygen during decay, thereby creating low oxygen conditions in the bottom waters. Foul-tasting and foul-smelling algal products, and toxic compounds from the decaying plants and algae, diminish the uses of water. Heavily polluted waters may be sources of epidemic infections because of the bacterial content of the phosphorus-containing sewage. Coastal waters react to small-to-moderate additions of phosphorus only if the water exchange with the ocean is impeded, for example, in fjords and in bays with large inflows of freshwater. In short, the biogeochemical cycling of phosphorus is greatly affected by man, who thereby creates several environmental problems.