C. Forsberg, THE LARGE-SCALE FLUX OF NUTRIENTS FROM LAND TO WATER AND THE EUTROPHICATION OF LAKES AND MARINE WATERS, Marine pollution bulletin, 29(6-12), 1994, pp. 409-413
The large-scale flux of nitrogen and phosphorus in modern society is c
oupled to the exponentially growing world population. During the last
three decades there has been a several-fold growth in use of nitrogen
(N) and phosphorus (P), for example, for agriculture production, in ch
emical products such as in detergents, and as food additives. Feeding
a growing population means increased human nutrient excretion. The mob
ility of N differs from that of P. For the easily mobile nitrate ion,
river exports are positively correlated to the size of local human pop
ulations. P on the other hand is fixed in different systems, at least
temporarily. Modern agro-ecosystems accumulate about 60% of the annual
input of P. The Stockholm region representing an urban ecosystem serv
ed by dephosphatation in sewage, accumulated about 80% of imported P d
uring 1990. With increasing accumulation there is an apparent risk for
increasing non-point source pollution. In some shallow recipient lake
s the sediments have been saturated with P. Even after the reduction o
f external loading these lakes are exporting more P than they are impo
rting. Lakes normally are traps for P. In order to prevent damage to n
atural resources and to stop the large-scale flux of nutrients from la
nd to water, the world population growth rate must be decreased and a
number of measures taken: agricultural structures must be changed incl
uding new concepts for the use of fertilizers; new municipal sewage tr
eatment processes must be developed permitting high-degree recycling o
f nutrients; unnecessary use of nutrients must be stopped, for example
, in detergents and by reducing nutrient additives in food and drinks.
Cola drinks, for example, contain 180 mg P l(-1), a concentration abo
ut 350 times higher than that of the effluent (0.5 mg P l(-1)) from mo
dern sewage treatment plants operating with dephosphatation. Financial
resources and effort are required to stop large-scale eutrophication
of marine waters.