RESUMO

Novel green technologies for soil remediation have been focusing on altering soil properties and improving soil health. Hydrothermally-altered feldspar (HYP, HydroPotash), recently developed, is being related as both an efficient amendment to immobilize heavy metals in soils and a plant nutrients source, consisting in a promising technology for revegetation of contaminated sites. In order to evaluate the effectiveness of using HYP for phytostabilization programs, two different soils (Technosol and Oxisol) collected from a smelting site were amended with increasing doses of HYPs (HYP-1 and HYP-2): 15, 30, 60, and 120 Mg ha-1. For comparison, a control (soil without amendment) and a soil amended with zeolite (clinoptilolite) were also included as treatments. After 90 days of incubation, HYPs decreased up to 83.8 % of Cd availability and reduced exchangeable Al up to 100 %. HydroPotash increased pH, cation exchange capacity, and contents of potassium, calcium, and phosphorus, as well as microbial biomass carbon, and fluorescein diacetate hydrolysis of soils. Andropogon gayanus, Eucalyptus grandis, and Heterocondylus vitalbae started growing from the dose of 15 Mg ha-1 HYPs in the Oxisol and 60 Mg ha-1 HYPs in the Technosol. Principal component analysis indicates that plant shoot dry weight was negatively correlated with extractable Cd and Zn and positively with pH, CEC, and Ca content. Besides promoting plant growth, HYPs reduced heavy metals (Cd and Zn) absorption by plants, indicating that HYP has potential use as an amendment in phytostabilization programs.

Assuntos

RESUMO

Coffee is considered an important source of organic nutrients and minerals, and these resources are strongly affected by agricultural management. Among the minerals, the element Mg is important, which is essential for both plants and humans. In this work, the effects of agricultural management on the absorption and storage of Mg by commercial, ground, roasted Arabica coffee were investigated. For this purpose, some Mg and P fractions were evaluated. It was observed that Mg stored in the grain was concentrated in the inorganic fraction, with an average extraction of 102% and in conventional samples and 119% in organic samples. These results suggest that in these samples Mg is probably largely presented as different inorganic salts. Phytate and organic acid salts are two possibilities discussed in this work that could explain this hypothesis. This can be corroborated by the extraction of Mg in the infusion of hot water.

Assuntos

RESUMO

The availability of cadmium (Cd) for plants and its impact in the environment depends on Cd sorption in soil colloids. The study of Cd sorption in soil and its fractionation is an interesting tool for the evaluation of Cd affinity with soil pools. The objective with this study was to evaluate Cd sorption and desorption in tropical soils with variable charge (three Oxisols), in a Mollisol and in two Entisols with diverse physical, chemical, and mineralogical attributes. We used a thermodynamic approach to evaluate Cd sorption and performed a chemical fractionation of Cd in the six soils. Data from Cd sorption fit the Langmuir model (r > 0.94), and the sorption capacity ranged from 0.33 to 11.5 mmol kg-1. The Gibbs standard free energy was positively correlated to Cd sorption capacity (r = 0.74, except for the Quartzipsamments), and it was more favorable in soils with great sorption capacity. Distribution of Cd among fractions was not affected (t test, α = 0.05) by initial concentration, and there was a predominance of Cd extractable in 0.1 mol L-1 CaCl2.

Assuntos

RESUMO

Contents of heavy metal on agricultural soils have been raised by land applications of sewage sludge and may constitute a hazard to plants, animals and humans. A field experiment was carried out from 1983 to 1987, to evaluate the long-term effect of sewage sludge application, with and without liming, on heavy metal accumulation and availability in a Rhodic Hapludox soil grown with maize (HMD 7974 hybrid). Trials were set up in a completely randomized blocks design with four replications. Each block was split in two bands, one with and another without liming. The sludge was applied in each band at rates: 0, 20, 40, 60 and 80 Mg ha-1 (dry basis) in a single application; and 40, 60 and 80 Mg ha-1 split in two, three and four equal yearly applications, respectively. The soil was sampled for chemical analysis each year after harvest. Soil samples were analysed for Cu, Ni and Zn in extracts obtained with DTPA and Mehlich-3 solutions, and in extracts obtained by digestion with nitric-perchloric acid (total metal contents), using an inductively coupled plasma (ICP) spectrometer. In general, Zn, Cu and Ni concentrations in DTPA and Mehlich-3 extracts increased linearly with sludge application. Total Cu and Zn concentrations increased when sludge was applied, whereas total Ni concentrations were not affected. Both extractants were suitable to evaluate Cu and Zn availability to corn in the soil treated with sewage sludge. Liming reduced the DTPA extractability of Zn. DTPA-extractable Cu concentrations were not significantly affected by liming. Mehlich-3-extractable Cu and Zn concentrations increased with liming. Only DTPA extractant indicated reduction of Ni concentrations in the soil after liming.

A reciclagem agrícola do lodo de esgoto tem provocado o acúmulo de metais pesados no solo e na água, podendo atingir níveis tóxicos e causar danos às plantas cultivadas, aos animais e ao homem, por meio da cadeia trófica. Foi desenvolvido um experimento, em condições de campo entre 1983 e 1987, onde foram avaliados os efeitos da aplicação de lodo de esgoto por quatro anos, com e sem calagem, sobre a acumulação e disponibilidade de metais pesados em um Latossolo Vermelho distrófico típico cultivado com milho (HMD 7974). O delineamento utilizado foi o de blocos completos ao acaso, com quatro repetições. Cada bloco foi dividido em duas faixas nas quais foram aplicados os tratamentos com e sem calcário, e em cada faixa foi aplicado o lodo nas seguintes doses: 0, 20, 40, 60 e 80 Mg ha-1 (material seco) de lodo de esgoto, em aplicação única; e as doses de 40, 60 e 80 Mg ha-1, parceladas em dois, três e quatro anos, respectivamente. A fitodisponibilidade dos metais foi avaliada pelos extratores DTPA e Mehlich-3. Os teores extraíveis de Cu, Ni e Zn no solo aumentaram linearmente com as doses de lodo de esgoto, para os dois extratores usados. A adição de lodo de esgoto elevou os teores totais de Cu e Zn, mas não afetou os teores de Ni no solo. Os extratores DTPA e Mehlich-3 foram igualmente eficientes na predição da fitodisponibilidade de Cu e Zn. A adição de calcário reduziu a extratabilidade de Zn-DTPA, não alterou a de Cu-DTPA e aumentou os teores de Cu e Zn extraíveis do solo por Mehlich-3. Somente o extrator DTPA mostrou a redução do teor de Ni extraível do solo com a adição de calcário.

RESUMO

Contents of heavy metal on agricultural soils have been raised by land applications of sewage sludge and may constitute a hazard to plants, animals and humans. A field experiment was carried out from 1983 to 1987, to evaluate the long-term effect of sewage sludge application, with and without liming, on heavy metal accumulation and availability in a Rhodic Hapludox soil grown with maize (HMD 7974 hybrid). Trials were set up in a completely randomized blocks design with four replications. Each block was split in two bands, one with and another without liming. The sludge was applied in each band at rates: 0, 20, 40, 60 and 80 Mg ha-1 (dry basis) in a single application; and 40, 60 and 80 Mg ha-1 split in two, three and four equal yearly applications, respectively. The soil was sampled for chemical analysis each year after harvest. Soil samples were analysed for Cu, Ni and Zn in extracts obtained with DTPA and Mehlich-3 solutions, and in extracts obtained by digestion with nitric-perchloric acid (total metal contents), using an inductively coupled plasma (ICP) spectrometer. In general, Zn, Cu and Ni concentrations in DTPA and Mehlich-3 extracts increased linearly with sludge application. Total Cu and Zn concentrations increased when sludge was applied, whereas total Ni concentrations were not affected. Both extractants were suitable to evaluate Cu and Zn availability to corn in the soil treated with sewage sludge. Liming reduced the DTPA extractability of Zn. DTPA-extractable Cu concentrations were not significantly affected by liming. Mehlich-3-extractable Cu and Zn concentrations increased with liming. Only DTPA extractant indicated reduction of Ni concentrations in the soil after liming.

A reciclagem agrícola do lodo de esgoto tem provocado o acúmulo de metais pesados no solo e na água, podendo atingir níveis tóxicos e causar danos às plantas cultivadas, aos animais e ao homem, por meio da cadeia trófica. Foi desenvolvido um experimento, em condições de campo entre 1983 e 1987, onde foram avaliados os efeitos da aplicação de lodo de esgoto por quatro anos, com e sem calagem, sobre a acumulação e disponibilidade de metais pesados em um Latossolo Vermelho distrófico típico cultivado com milho (HMD 7974). O delineamento utilizado foi o de blocos completos ao acaso, com quatro repetições. Cada bloco foi dividido em duas faixas nas quais foram aplicados os tratamentos com e sem calcário, e em cada faixa foi aplicado o lodo nas seguintes doses: 0, 20, 40, 60 e 80 Mg ha-1 (material seco) de lodo de esgoto, em aplicação única; e as doses de 40, 60 e 80 Mg ha-1, parceladas em dois, três e quatro anos, respectivamente. A fitodisponibilidade dos metais foi avaliada pelos extratores DTPA e Mehlich-3. Os teores extraíveis de Cu, Ni e Zn no solo aumentaram linearmente com as doses de lodo de esgoto, para os dois extratores usados. A adição de lodo de esgoto elevou os teores totais de Cu e Zn, mas não afetou os teores de Ni no solo. Os extratores DTPA e Mehlich-3 foram igualmente eficientes na predição da fitodisponibilidade de Cu e Zn. A adição de calcário reduziu a extratabilidade de Zn-DTPA, não alterou a de Cu-DTPA e aumentou os teores de Cu e Zn extraíveis do solo por Mehlich-3. Somente o extrator DTPA mostrou a redução do teor de Ni extraível do solo com a adição de calcário.