SEQUENTIAL EXTRACTION AND SPECIATION OF HEAVY METALS IN THE PROCESS OF COMPOSTING OF WASTE GARBAGE = EXTRA O SEQUENCIAL E ESPECIA O DE METAIS PESADOS NO DECORRER DO PROCESSO DE COMPOSTAGEM DE RESíDUOS SóLIDOS DOMICILIARES

Environmental pollution by heavy metals caused by the intensification of industrial activities, agriculture and urbanization, especially the generation of solid waste and the necessity of treat them biologically is a growing problem, causing serious ecological impacts. It carried out sequential extraction for heavy metals speciation in organic trash during composting, objecting the understanding of chemical Cu, Mn and Zn transformations and environmental risks. The extractors utilized in sequence and the respective fractions (beginning and ending of composting) were MgCl2 (soluble fraction – 5, 2% to Cu; 6, 7% to Mn; <1 to Zn; 2, 3% to Ni; 0.7, 0.1% to Pb; 24, 33% to Cd); CH3COONa (carbonate – 4, 3% to Cu; 24, 28% to Mn; 25, 20% to Zn; 6, 7% to Ni; 18, 13% to Pb; 37, 33% to Cd); Hidroxilamina+HOA (reduced/ oxidated) – 4% to Cu, 6, 21% to Mn and 22, 17% to Zn; 10, 14% to Ni, 38, 21% to Pb and 0% to Cd); H2O2+NH4OAc (organic – 22, 41% to Cu, 3, 4% to Mn; 7, 4% to Zn; 6, 14% to Ni, 39, 49% to Pb and 0% to Cd) and HNO3+HClO4 (remaining portion – 65, 50% to Cu, 61, 40% to Mn; 45, 58% to Zn; 76, 62% to Ni, 4, 17% to Pb; 38, 34% to Cd). The results show that composting process provides that the biggest fractions of Cu is organic or residual, Mn in carbonate or reduced forms and the Zn remains in the residual or reduced forms, Ni and Pb are organic or residual and the Cd remains in the residual or carbonate forms, offering bigger ambient risks. = A polui o ambiental por metais pesados, pela intensifica o das atividades industriais, agrícolas e urbaniza o, em especial a gera o de resíduos sólidos e a necessidade de tratá-los biologicamente consiste num problema crescente, responsável por sérios impactos ecológicos. Efetuou-se extra o sequencial de metais pesados para avaliar a especia o de Cu, Cd, Mn, Ni, Pb e Zn no lixo organico durante a compostagem, permitindo o entendimento das transforma es no processo e potenciais riscos ambientais destes elementos.Os extratores utilizados na extra o sequencial modificam as propriedades que influenciam fortemente na intera o do metal com a fase sólida, e as respectivas fra es solúveis no início e final da compostagem, quanticadas por Espectrometria de Emiss o ótica com fonte de plasma acoplado indutivamente - ICP OES. A sequencia dos extratores utilizada e as respectivas fra es (início e fim da compostagem) foram: MgCl2 (fra o solúvel – 5 e 2% para Cu, 6 e 7% de Mn; <1 de Zn, 2 e 3% de Ni, 0,7 e 0,1% para Pb; 24 e 33% para Cd); CH3COONa (carbonato - 4, 3% para Cu, 24 e 28% de Mn; 25 e 20% para Zn, 6 e 7% de Ni,