Cleide Aparecida de Abreu

ROUTINE SOIL TESTING TO MONITOR HEAVY METALS AND BORON

Microelementos tem um papel importante na agricultura, devido a sua essencialidade para plantas e tambem a possibilidade de serem toxicos as plantas e aos animais. Os cinco micronutrientes (B, Cu, Fe, Mn, e Zn) sao comumente determinados nas analises rotineiras de solos com finalidade de recomendacao de adubacao. Os outros quatro elementos (Cd, Cr, Pb, e Ni) sao metais pesados importantes para os solos agricolas e nao sao normalmente determinados em amostras de solos enviadas pelos agricultores. Portanto, altos teores desses metais pesados em terras agricultaveis poderao passar despercebidos. O objetivo deste trabalho foi usar a analise de rotina de solo para monitorar o teor dos nove elementos em amostras de solo. Um total de 13.416 amostras de solo de 21 estados brasileiros, sendo 58% delas originarias do estado de Sao Paulo, foram analisadas. O boro foi determinado usando a agua quente e os outros metais foram extraidos pelo DTPA (pH 7,3). Considerando todas as amostras, as faixas dos teores, em de mg dm-3 foram: B, 0,01-10,6; Cu, 0,1-56,2; Fe, 0,5-476; Mn, 1-325; Zn, 1-453; Cd 0,00-3,43, Cr, 0,0-42,9; Ni, 0,00-65,1; Pb, 0,00-63,9. Os valores medios para amostras originadas do Estado de Sao Paulo foram de: 0,32-B, 2,5-Cu, 36-Fe, 16,1-Mn, 4,8-Zn, 0,02-Cd, 0,03-Cr, 0,18-Ni e 0,85-Pb. Resultados semelhantes foram obtidos para amostras de outros Estados. Os valores mais altos sao indicativos de acao antropogenica, devido a aplicacao de fertilizantes ou de atividades industriais de mineracao. Analises de rotina feitas na amostras de solos do Brasil, especialmente originarias do estado de Sao Paulo, podem servir com base de dados para indicar o potencial de deficiencia de micronutrientes ou fitotoxicidade de metal pesado em solos agricultaveis, permitindo a tomada de acoes preventivas.

DISTRIBUIÇÃO DE CHUMBO NO PERFIL DE SOLO AVALIADA PELAS SOLUÇÕES DE DTPA E MEHLICH-3

Significant increase in the Pb content in cultivated soils has been observed near industrial areas. The objective of this work was to evaluate the soil Pb distribution profile near and distant of the lead emiting point, located between the Presidente Dutra highroad and the Cacapava Velha City, State of Sao Paulo, Brazil and to compare the Pb contents found by using DTPA and Mehlich-3 extracting solutions. Soil samples were collected at 500 and 1.000 m distant from the lead emiting point, in the N, S, E, and W directions, at depths of 0-5, 5-10, 10-20, 20-40 and 0-20 cm. Samples were treated separately with DTPA and Mehlich-3 solutions for the Pb extraction. The highest Pb concentrations were found in the soil samples collected close to the source of contamination. The results obtained using DTPA and Mehlich-3 solutions showed clearly that the lead tends to accumulate in the surface ground layer, decreasing with the soil depth. This indicated that the procedures using either DTPA or Mehlich-3 solutions as Pb extractor from soils should be also considered as appropriate for environmental monitoring.

Lead uptake and tolerance of Ricinus communis L.

Phytoextraction is an important technique used for the decontamination of areas polluted by lead. Consequently, an understanding of the physiological responses to tolerance of tropical species subjected to increasing levels of contamination is fundamental before considering their use as phytoextractors in contaminated areas. The objective of this study was to assess the lead (Pb) uptake and the tolerance of Ricinus communis L. The plants were cultivated in nutrient solution in a greenhouse under controlled conditions. Lead was tested at concentrations of 0, 100, 200 and 400 µmol L-1. The experimental set-up was a block design, using a 4 x 1 factorial scheme, with three replicates. Biometric analyses, photosynthesis rates, and Pb content in the nutritive solution as well as in roots and shoots were performed. In conclusion, R. communis L is a hyperaccumulator species for Pb and presents tolerance properties in lead light concentration.

Pb-phytoextraction by maize in a Pb-EDTA treated Oxisol

One of the most viable strategies to restore metal contaminated soils is the introduction of plants specialized in their accumulation or able to tolerate very high metal concentrations. This research evaluated: i. the maize as a Pb-accumulator plant; ii. the effects of EDTA-chelating agent for Pb-uptake by maize; iii. amending effect of EDTA on the soil Pb-availability using different extracts. Treatments consisted of Pb rates (100; 200; 350; 1,200 and 2,400 mg kg -1 ) applied to a Rhodic Hapludox in the form of Pb 3 (NO) 2 with (0.5 g kg -1 ) and without EDTA. Lead concentrations were determined in maize plant shoots. Soil available Pb was obtained using DTPA, Mehlich-3 and saturation solutions methods. Ionic speciation in the soil solution was performed using the software Visual-Minteq. Although a low t value was found (t 1,500 mg kg -1 of Pb) in maize shoots regardless of EDTA addition. Maize plants treated with EDTA had lower dry matter yield, mainly due to toxic levels of Fe and Al of the Oxisol. All extracting solutions were effective to determine available Pb in soil samples, but the saturation extract is a more difficult and time consuming procedure. At low and medium Pb levels, the plants grew less on EDTA, therefore the phytoextration process was less efficient. The addition of EDTA to the soil is not recommended with the purpose of increasing Pb

Trace Elements Extracted by DTPA and Mehlich‐3 from Agricultural Soils with and without Compost Additions

Abstract Risks of soil contamination when waste materials are used as fertilizers have been a matter of frequent concern. The effect of compost from municipal organic waste on trace element status was examined in short‐term field trials at neighboring areas of A Coruña (northwest Spain). The study sites were characterized as medium textured soils, with a range of pHs, organic matter content, and cation exchange capacity. The objective of this work was to compare two extraction methods (DTPA and Mehlich‐3) to determine micronutrient contents in soils with and without compost additions. DTPA and Mehlich‐3 extractions were carried out, and then analyses for Fe, Mn, Cu, Zn, Ni, Cr, Pb, and Cd contents were performed by ICP‐AES. Overall, DTPA was less efficient than Mehlich‐3 for Fe and Mn extraction. Lead, Ni, and Cd were extracted more effectively by DTPA than by Mehlich‐3. In general, the efficiency of the extractants was related to compost addition, a trend that was most apparent for Zn and Cu. Levels of trace metals extracted by DTPA and Mehlich‐3 from soils without compost addition were already highly variable, because of traditional farmyard manure and slurry fertilization. Diagnostic criteria for allowable loading limits of heavy metals during compost application should take into account direct measurements of background levels and relevant soil properties such as soil acidity.

DTPA AND MEHLICH-3 MICRONUTRIENT EXTRACTABILITY IN NATURAL SOILS

Most soils of the humid area in the Iberian Peninsula are characterized by acid, desaturated, organic rich surface horizons. In this study micronutrients (Cu, Fe, Mn and Zn) were extracted using DTPA and Mehlich-3. Total contents were also determined by digestion with nitric acid. Seven natural soil profiles, representing major acid soil types developed over a wide variety of parent materials were collected. In addition, three soil profiles containing carbonates and/or a high base saturation were sampled. The organic matter content when all samples were included in the data set ranged between 0.37 and 26.51%. For the acid set of samples, Mehlich-3 extractable concentrations of Cu, Fe, Mn and Zn were higher than contents extracted by DTPA. However, DTPA extracted higher concentrations of Cu, Fe and Mn than Mehlich-3 in near neutral or calcareous soils. Correlation coefficients between DTPA and Mehlich-3 extractable amounts were in the range from 0.49 to 0.96 for the set of acid soil samples and in the range from 0.71 to 0.92 for non-acid horizons. However, for acid and non-acid samples combined, correlations between micronutrient contents extracted by both solutions were much weaker and not significant. Results illustrate difficulties for selecting a single multielement extractant for different soils of the studied region. Interactions between micronutrient extractability, pH and organic matter content were evaluated. In all of the studied soil profiles, there was a decrease in the extractable Cu, Fe, Mn and Zn contents with increasing soil depth.

Sorption and desorption of cadmium and zinc in two tropical soils amended with sugarcane-straw-derived biochar

PurposeBiochars may enhance the retention capacity of metals in soils, especially in highly weathered tropical soil whose low cation exchange capacity renders heavy metals mobile, and thus be able to leach from soils. We evaluated the effect of sugarcane-straw-derived biochar on sorption and desorption of Cd(II) and Zn(II) in two tropical soils in particular to distinguish primary and secondary mechanisms of metal retention.Material and methodsTo test the efficiency of biochar to retain heavy metals, sugarcane-straw-derived biochar was mixed with a clayey Oxisol and an Entisol both from the state of Sao Paulo, Brazil, in batch testing to obtain sorption-desorption isotherms of Cd(II) and Zn(II) and measure the release/displacement of cations (Ca2+ and Mg2+) or precipitation with phosphate during the sorption process.Results and discussionBiochar increased the sorption (including adsorption and precipitation) of both metals in both soils but that most sorption reactions were reversible under buffer acidic conditions, due to dissolution of precipitates in low pH values (<4.9). Exchange of Cd or Zn with Ca and Mg from the biochar was found to play a minor role on the retention mechanism, whereas surface precipitation (mainly in the Entisol) of the metals (e.g. with phosphate) was likely to be the main sorption mechanism.ConclusionsApplication of sugarcane-straw-derived biochar to heavy-metal-contaminated tropical soils seems justified because of its sorptive capacity for Cd and Zn. However, binding reactions on surfaces were reversible, mainly for Cd(II), resulting in the likelihood that repeat applications of biochar would be required to maintain reduced soil solution concentrations of Cd and Zn over time, thus avoiding phytotoxicity and associated environmental risks.

Extraction of phytoavailable trace metals from tropical soils by mixed ion exchange resin modified with inorganic and organic ligands

Abstract Chelating agents and organic acid ligands readily solubilize trace and heavy metals in soils. We compared Fe, Mn, Cu and Zn extracted from 16 soils by a mixed ion exchange resin (Amberlite IRA-120+ Amberlite IRA-400) modified with six simple inorganic and organic acid ligands with a conventional chelating agent (DTPA) and bioassay. The mixed cation–anion exchange resins were saturated with Na-salts of chloride (R–CHL), bicarbonate (R–BIC), fluoride (R–FLU), acetate (R–ACT), citrate (R–CIT) and tartrate (R–TAR). Solubilization and adsorption of Fe and Cu from the soils by resin–ligand systems decreased in the order R–CIT≥R–FLU≥R–TAR=R–ACT>R–CHL=R–BIC reflecting differential stability of Fe- and Cu–organic/inorganic complexes. The R–CHL solubilized and adsorbed more Mn and Zn than other resin–ligand systems because of the relatively low pH maintained by the R–CHL-soil suspension. Extraction with DTPA gave similar amounts of Fe and Mn as resin–ligand systems, but DTPA extracted two to three times more Cu and Zn than resin. Resin-extractable Fe, Mn and Cu correlated with the corresponding DTPA-extractable metal contents, while both resin- and DTPA-extractable Cu correlated with the bioassay results. The R–ACT and R–TAR extractable Zn correlated more strongly with the bioassay results than DTPA-extractable Zn. Mixed ion exchange resin is apparently feasible for characterizing plant available Fe, Mn, Cu and Zn in soils.

Efeito da reação do solo no zinco extraído pelas soluções de dtpa e Mehlich-1

A analise do solo e uma ferramenta eficiente para avaliar a disponibilidade de Zn, desde que seja escolhido adequadamente o processo de extracao. Neste trabalho, desenvolvido em casa de vegetacao, em Campinas, em 1993, avaliou-se a influencia da calagem no Zn extraivel do solo, usando-se o milho como planta-teste. Utilizaram-se amostras de cinco solos, sendo duas de latossolo vermelho-amarelo, uma de latossolo humico, uma de latossolo roxo e uma de terra roxa estruturada, as quais receberam cinco doses de calcario. Antes e depois do cultivo do milho, retiraram-se amostras de solos para analise de Zn, usando-se os extratores DTPA e Mehlich-1. Na fase inicial, as plantas de milho apresentaram sintomas de deficiencia de Zn, caracterizados por uma coloracao amarelo-clara e altura reduzida. 0 extrator DTPA mostrou os melhores resultados com valores altos e positivos de correlacao entre os teores de Zn na planta e no solo. Concluiu-se que a mudanca na disponibilidade de Zn, decorrente da reacao do solo, foi mais bem avaliada pela solucao de DTPA.

Efficiency of multinutrient extractants for the determining of available zinc in soils

The increasing use of the ICP-AES (inductively coupled plasma atomic emission spectrophotometry) as a multielement analytical technique has stressed the preference for the use of multinutrient extractants in routine soil analysis. However, few studies relating the extraction of zinc (Zn) from soil with such extractants and the absorption of the element by plants have been published. Two experiments under greenhouse conditions were carried out in order to determine the efficiency of some multinutrient extractants for the determination of available Zn in 44 soils from the State of São Paulo, Brazil, for corn and soybean. All soil samples were limed to increase the CECs base saturation at pH 7 to 70%. Twenty-two soil samples with DTPA (diethylenetriaminepentaacetic acid) extractable Zn concentration lower than 0.6 mg dm−3 received either the application of B, Cu, Mn, Zn or of these micronutrients excluding Zn. The remaining 22 soil samples, with Zn concentration above 0.6 mg dm−3, received application of three micronutrients (B, Cu and Mn). Macronutrients were applied to all pots as needed for crop development. Zinc was extracted from the soils before each planting using the extracting solutions, DTPA, Mehlich 1 (M-1), Mehlich 3 (M-3) and AB-DTPA (ammonium bicarbonate-DTPA) and determined by ICP-AES. The results showed significant correlations between plant Zn concentration and soil Zn concentration. The correlation values between soil-Zn and plant-Zn were of 0.74 (M-3), 0.73 (DTPA), 0.62 (AB-DTPA) and 0.61 (M-1) for corn, and of 0.71 (DTPA), 0.63 (M-1), 0.58 (M-3) and 0.46 (AB-DTPA) for soybean. Thus, the DTPA solution was the most efficient extractant for the determination of bioavailable Zn when both crops are considered together.