[Problems and requirements for the development of an ecologically oriented agriculture in the surroundings of Berlin under special consideration of the heavy metal contamination of periurban agrarian areas]

aguas residuales ambiente urbano berlin carga contaminante charge polluante ciudades contamination ecologia ecologie ecology environnement urbain farmland heavy metals land management land use metales pesados pollutant load pollution du sol relaciones campo ciudad relation ville campagne rural urban relations soil pollution suburban areas terre agricole towns urban environment utilisation des terres ville wastewater zonas periurbanas