TOWARDS ZERO ACCUMULATION OF HEAVY-METALS IN SOILS - AN IMPERATIVE ORA FAD

Sweden has recently introduced new guidelines for the agricultural use of sewage sludge which contain successively more restrictive metal lo ading rates for soils. At the same time further efforts are made to re duce the input of heavy metals through atmospheric deposition and fert iliser use. The proposed metal loading limits are among the most restr ictive in the world, although other scandinavian countries and the Net herlands have proposed similarly low limits. It is the aim of the Swed ish Environmental Protection Board to successively reduce the metal lo ad of soils until a situation of zero accumulation is reached. With th e possible exception for Cd, there is apparently no scientific evidenc e at the moment to suggest that zero accumulation of metals in soil is required to adequately protect soil productivity, the environment, an d human and animal health. A policy which steers towards zero accumula tion may therefore seem excessively cautious. It is, however, also a p olicy which recognises the practically irreversible nature of elevated heavy metal concentrations and their effects in soil, the deficiencie s in the evidence currently available with which to establish safe met al loadings for soils, as well as the need to preserve the agronomic v alue of soils for many years to come. It is argued that the use of res trictive annual metal loading rates can be used to effectively ensure that maximum soil concentrations or cumulative pollutant loadings, con sidered to be safe are not reached in the foreseeable future.