No abstract

O efeito da aplicação de biossólido na distribuição e extração de Cr, Cu, Ni, Pb e Zn foi avaliado em solos Molisol de uma importante zona destinada à agricultura no Chile central. Massas de 15 e 30 Mg ha -1 de biossólidos foram adicionadas aos solos e os mesmos foram incubados por 60 dias sob condições controladas de umidade e temperatura. Quatro biossólidos domésticos foram obtidos em uma das plantas de tratamento de águas residuárias de Santiago. As extrações sequenciais a partir de amostras de biossólido e solo foram efetuadas de acordo com o procedimento recomendado pelo BCR, que se baseia em quatro extrações para obter uma fração solúvel em ácido (trocável, carbonatos), uma fração reduzível (óxidos de ferro/manganês), uma fração oxidável (matéria orgânica e sulfetos) e uma fração residual. Os metais traço foram determinados por espectrometria de absorção atômica com chama e espectrometria de massa acoplada ao plasma indutivo. Dentre os metais determinados em biossólidos, Zn apresentou a concentração mais alta. A quantidade de metais traço determinada em alguns biossólidos, exceto para Ni, foi abaixo dos limites permitidos pela legislação Chilena para biossólidos. Em geral, desconsiderando-se a fração residual, os metais foram encontrados predominantemente nas frações reduzíveis e oxidáveis. Um planejamento multifatorial foi empregado para avaliar os efeitos da quantidade de biossólido aplicada, do tipo de biossólido e do tempo de incubação. A incorporação do biossólido à razão de 30 Mg ha -1 produziu um aumento na disponibilidade de Zn e Ni em todos os solos e de Cu na maioria deles. Por outro lado, Cr e Pb não variaram significativamente. Em geral, os fatores incubação e tipo de biossólido não apresentaram efeitos pronunciados quando comparados com as condições iniciais.The effect of biosolid application on the distribution and extractability of Cr, Cu, Ni, Pb, and Zn was assessed in Mollisol soils from an important agricultural zone in central Chile. These were amended with biosolids at the amounts of 15 and 30 Mg ha -1 and incubated for 60 days under controlled conditions of moisture and temperature. Four domestic biosolids were obtained from the monofill at one of the Santiago wastewater treatment plants. Biosolid and soil sequential extraction was performed according to the procedure recommended by BCR, which considers four extractions to obtain an acid-soluble fraction (exchangeable, carbonates), a reducible fraction (iron/manganese oxides), an oxidizable fraction (organic matter and sulfides) and the residual one. Trace metals were determined by flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry. Among the metals determined in biosolids, Zn had the highest concentration. Total trace metal contents found, except for Ni in some biosolids, was below the limits allowed by the Chilean regulation for biosolids. In general, without considering the residual fraction, the metals were found predominantly as reducible and oxidizable fractions. A multifactorial design was appl...

This study assessed the effect of biosolids applied at rates, 0, 30, 45, and 60 Mg ha −1 on the chemical associations and bioavailability of Cu and Zn in soils from an important agricultural zone of the Metropolitan Region in Central Chile. Three methods were used to determine the bioavailability of Cu and Zn in soils: ryegrass (Lolium perenne) plants, diffusive gradients in thin films (DGT) technique, and Community Bureau of Reference (BCR) sequential extraction. The DGT effective concentration (C E ) and sequential extract acid soluble fraction of the BCR extraction (most labile fraction of the soils, normally associated with bioavailability) were compared with total metal concentration in ryegrass plants as a means to compare the chemical and biological measures of bioavailability. Total Zn was higher in comparison to Cu for all treatments. Concentrations were within the limits set by the Chilean regulations for land-applied biosolids. Metals in the control soil were primarily found in the residual fraction of soils. Biosolids application generally decreased this fraction, with a subsequent increase observed mainly in the acid soluble fraction. The contents of Cu and Zn in ryegrass plants increased with increasing rates of biosolids. Comparison of the Cu and Zn content in ryegrass plants with C E , showed a good correlation for Zn. However, the C E for soil Cu was only related to plant Cu for some of the soils studied. Correlation between Zn in ryegrass plants and the labile fraction of Zn as measured by the sequential extraction was excellent, with correlation coefficients >0.9, while for Cu, correlation coefficients were lower.