ABSTRACT Ultramafic soils are originated from ultramafic rocks such as peridotite and serpentinite and are highly enriched in metals (e.g., Ni, Cr, and Co) and depleted in plant nutrients (e.g., P, K, and Ca). Such characteristics make these soils unfavorable for agriculture and have raised environmental concerns on metal release to the environment. From another perspective, ultramafic soils host a diverse flora with higher endemism than surrounding non-ultramafic areas, which has provided scientists with an opportunity to investigate the evolutionary genetics of plant adaptation. Some plant species adapted to these stressful edaphic conditions developing the ability to accumulate uncommonly high metal concentrations in the harvestable biomass. Such species, called metal hyperaccumulators, can extract metals from ultramafic soils, especially Ni, in a circular economy approach in which the metal-rich biomass is incinerated to generate valuable bio-ores. Phytomining promises to turn ultramafic soils and low-grade ore bodies into economically viable alternatives to metal extraction. Here, we review the current knowledge on ultramafic soils and the most promising hyperaccumulators used to exploit them in temperate and tropical climates. In the tropics, including Brazil, the search for new hyperaccumulator candidates for phytomining and the knowledge to crop these species is incipient and holds untapped opportunities. Despite the feasibility of the phytomining chain has been proven, large-scale demonstrations of profitability are needed to establish the technology.

ABSTRACT Soil contamination by metals threatens both the environment and human health and hence requires remedial actions. The conventional approach of removing polluted soils and replacing them with clean soils (excavation) is very costly for low-value sites and not feasible on a large scale. In this scenario, phytoremediation emerged as a promising cost-effective and environmentally-friendly technology to render metals less bioavailable (phytostabilization) or clean up metal-polluted soils (phytoextraction). Phytostabilization has demonstrable successes in mining sites and brownfields. On the other hand, phytoextraction still has few examples of successful applications. Either by using hyperaccumulating plants or high biomass plants induced to accumulate metals through chelator addition to the soil, major phytoextraction bottlenecks remain, mainly the extended time frame to remediation and lack of revenue from the land during the process. Due to these drawbacks, phytomanagement has been proposed to provide economic, environmental, and social benefits until the contaminated site returns to productive usage. Here, we review the evolution, promises, and limitations of these phytotechnologies. Despite the lack of commercial phytoextraction operations, there have been significant advances in understanding phytotechnologies' main constraints. Further investigation on new plant species, especially in the tropics, and soil amendments can potentially provide the basis to transform phytoextraction into an operational metal clean-up technology in the future. However, at the current state of the art, phytotechnology is moving the focus from remediation technologies to pollution attenuation and palliative cares.

ABSTRACT. The relationship between soil and health is important for populations that depend on the local environment to meet their nutritional needs. This study aimed to evaluate the concentrations of major and trace elements in the soils, edible parts of crops and urine of farmers in agroecological communities. We collected samples of soil, edible parts of crops and urine of farmers and family members in 23 crop fields in agroecological communities from northeast Brazil. These samples were analyzed to concentrations of Al, As, Ca, Cr, Cu, Fe, Hg, Mg, Zn, and Pb in urine and discriminant analysis and principal component analysis were used to assess the data. Concentrations of potentially toxic elements in soils and crops of agroecosystems were below regulatory levels. Farmers living in agroecological communities present most of the essential and toxic elements in urine within the reference ranges. In general, results showed that urinary concentration of toxic elements among farmers and their families were below allowable limits, which may be due to the agroecological practices.

ABSTRACT. We studied the mineralogical properties and chemical composition of different granites using energy dispersive X-ray spectroscopy coupled with scanning electron microscopy to understand the relationship between granite signatures and soil characteristics, including weathering patterns and soil fertility status. The discriminant analysis (DA) was based on soil physical and chemical properties and was used to differentiate soils developed from I- and S-type granites across contrasting climatic conditions in northeast Brazil. The DA identified the highest values of organic carbon, clay and plant nutrients as key variables to recognize soil profiles derived from I-type granites. In contrast, the greater sand contents and Al saturation distinguished soils developed from S-type granites. These results were related to the mineralogical characteristics of each granite type, such as a high percentage of silica-bearing minerals in the S-type granites. The highest concentrations of K, Ca, Mg, and P in I-type granites were found in feldspars, amphiboles, and apatite. These elements account for the majority of nutrients derived in their soil profiles. However, it seems that the harsh conditions of the humid tropical environment equalized the effect of the rocks on weathering rates-the difference in chemical index of alteration is more extreme in the dry region.

ABSTRACT Micronutrient research for sugarcane in northeastern Brazil is scarce and most works on this issue date back to the 70’s and 80’s. The objectives of this study were to assess the available and reserve pools of Fe, Mn, Cu, and Zn in soils cultivated with sugarcane under three geological contexts in northeastern Brazil as well as to diagnose the micronutrient nutritional status of sugarcane grown on these areas in order to identify pedogeological conditions in which micronutrient deficiencies are likely. Results showed that the soils cultivated with sugarcane in the states of Paraíba and Pernambuco posed available and reserve contents of micronutrients related to the parent materials and soil textural classes. The reserve contents of Fe, Mn, Zn, and Cu in all the soil samples analyzed were below the background values established for the region, which indicates a continuous exportation of micronutrients through cultivation. The mean and median contents of Mn, Zn, and Cu in diagnostic leaves of sugarcane were below their respective nutritional optimum ranges recommended to Brazil while Fe contents achieved the crop nutritional requirement. This is the first time such an approach based on pedogeological contexts is used to study the available and reserve pools of micronutrients in soils of Northeast Brazil.

ABSTRACT Soil contamination by heavy metals threatens ecosystems and human health. Environmental monitoring bodies need reference values for these contaminants to assess the impacts of anthropogenic activities on soil contamination. Quality reference values (QRVs) reflect the natural concentrations of heavy metals in soils without anthropic interference and must be regionally established. The aim of this study was to determine the natural concentrations and quality reference values for the metals Ag, Ba, Cd, Co, Cu, Cr, Mo, Ni, Pb, Sb and Zn in soils of Paraíba state, Brazil. Soil samples were collected from 94 locations across the state in areas of native vegetation or with minimal anthropic interference. The quality reference values (QRVs) were (mg kg-1): Ag (<0.53), Ba (117.41), Cd (0.08), Co (13.14), Cu (20.82), Cr (48.35), Mo (0.43), Ni (14.44), Sb (0.61), Pb (14.62) and Zn (33.65). Principal component analysis grouped the metals Cd, Cr, Cu, Ni, Pb and Sb (PC1); Ag (PC2); and Ba, Co, Fe, Mn and Zn (PC3). These values were made official by Paraíba state through Normativa Resolution 3602/2014.

ABSTRACT: Studies regarding background concentrations of rare earth elements (REEs) are scarce and have mainly focused on a limited number of soil types from the northern hemisphere. The aim of this study was to determine REE concentrations in thirty-five benchmark soils of Brazil. Composite soil samples were taken from areas under native vegetation or with minimal anthropogenic influence. Concentrations of La, Ce, Pr, Nd, Sm, Eu, Gd, Yb, Lu, Dy, Er, Ho, Tb, Tm, Y, Sc, and Fe were determined by ICP-OES using a cyclonic spray chamber/nebulizer system after microwave acid digestion. Results were assessed by descriptive statistics, Pearson correlation, and principal component analysis (PCA). Regression analyses among Fe, organic carbon, and REEs were performed to provide a tool for estimating REE concentrations in soils. The REE concentrations in the Brazilian benchmark soils were in the following order: Ce > La > Nd > Pr > Y > Sm > Gd > Sc > Dy > Yb > Eu > Er > Tb > Ho > Lu > Tm. The clear decoupling between light and heavy rare earth elements in soils, indicated by multivariate analysis, is mainly related to differences in parent material. The lowest REE concentrations were found in sandy sediments, whereas the highest REE concentrations were observed in basalt, biotite gneiss, and clayey sediments. The organic carbon and Fe concentrations can properly predict REE concentrations in soils; such a finding can assist in estimating REE concentrations in soils not only in Brazil but also in similar soils developed under tropical conditions.

O crescimento industrial e o populacional têm aumentado os teores de metais pesados nos solos e impactado a qualidade desse recurso. Nesse contexto, as agências de proteção ambiental vêm despendendo esforços para o estabelecimento de índices que possam identificar áreas suspeitas de contaminação. Valores de Referência de Qualidade para Solos (VRQs) refletem a concentração natural de determinada substância no solo, sem interferência antrópica. O trabalho objetivou estabelecer os VRQs para os metais Ag, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, V e Zn exigidos pelo Conama, para composição da legislação direcionada ao monitoramento desses elementos nos solos do Estado do Rio Grande do Norte. Foram coletadas 416 amostras de solo em áreas de mata nativa ou com mínima influência antrópica. A abertura das amostras foi efetuada pelo método EPA-3051A, sendo os metais determinados por espectrometria de emissão ótica (ICP-OES) e absorção atômica (AA). Os resultados do trabalho comprovaram que estudos regionalizados são essenciais para definição de VRQs. Os VRQs calculados para o Rio Grande do Norte foram mais restritivos que os de outros estados do país. A análise fatorial de confirmação dos dados foi útil para obtenção de VRQs mais confiáveis e demonstrou que para o Estado esses valores podem ser estabelecidos com apenas duas repetições por local de coleta. Nesse sentido, é primordial um planejamento prévio, de distribuição dos locais de amostragem, de maneira que os diversos compartimentos geomorfológicos, pedológicos e geológicos do Estado sejam representados.

Industrial development and population growth have increased heavy metal concentrations in soils and impacted soil quality. In this scenario, environmental protection agencies have been concerned with establishing heavy metal quality reference values (QRV) that may identify contaminated sites. The study was carried out to provide soil reference values for the metals Ag, Ba, Cd, Co, Cr, Cu, Ni, Pb, Sb, V, and Zn in soils of the State of Rio Grande do Norte according to Brazilian legislation. The study analyzed 416 soil samples taken from native forest or areas with minimal human interference. These samples were digested by the USEPA 3051A method, and the metals were measured by Inductively Coupled Plasma - Optic Emission Spectrometry (ICP-OES) or flame atomic absorption (FAA). The results showed that regional geochemical surveys are essential in establishing QRVs for heavy metals. For example, the QRV for the soils of Rio Grande do Norte were more restrictive than the QRVs adopted for other Brazilian states. Confirmation factorial analysis of the data was useful for obtaining more reliable QRVs and showed that for the state these values could be obtained from two replicates only per collection location. Thus, advance planning is essential in distribution of sampling locations so that the diverse geomorphological, pedological, and geological compartments of the state are represented.

A ausência de normatização de um método-padrão para determinar os metais pesados em fertilizantes no Brasil e a consequente utilização de diversos métodos de digestão têm provocado variações nos resultados, dificultando a sua interpretação. Nesse contexto, o objetivo deste trabalho foi comparar a eficiência de três métodos de digestão de fertilizantes para delimitar os metais Cd, Ni, Pb e Cr. Foram utilizadas 45 amostras de fertilizantes comercializados no nordeste do Brasil, além de uma amostra de fertilizante com teores de metais certificados pelo National Institute of Standards and Technology (NIST), incluindo fosfato natural, fertilizante organomineral com fosfato natural, superfosfato simples, superfosfato triplo, fertilizante misto e fertilizante com micronutrientes, que foram digeridos pelos métodos do Ministério da Agricultura, Pecuária e Abastecimento (MAPA) e da Agência Americana de Proteção Ambiental (USEPA): 3051A e 3052. Os resultados demonstraram que o método USEPA 3052 apresentou maiores recuperações para metais menos solúveis, como Ni e Pb, evidenciando que os teores totais desses elementos são subestimados pelos métodos convencionais de digestão para fertilizantes. O método USEPA 3051A evidenciou resultados muito semelhantes ao método atualmente em uso no Brasil (Brasil, 2006), sendo preferido seu uso em razão da diminuição dos custos com ácidos, do menor tempo de digestão e da maior reprodutibilidade.

The lack of a standard method to regulate heavy metal determination in Brazilian fertilizers and the subsequent use of several digestion methods have produced variations in the results, hampering interpretation. Thus, the aim of this study was to compare the effectiveness of three digestion methods for determination of metals such as Cd, Ni, Pb, and Cr in fertilizers. Samples of 45 fertilizers marketed in northeastern Brazil were used. A fertilizer sample with heavy metal contents certified by the US National Institute of Standards and Technology (NIST) was used as control. The following fertilizers were tested: rock phosphate; organo-mineral fertilizer with rock phosphate; single superphosphate; triple superphosphate; mixed N-P-K fertilizer; and fertilizer with micronutrients. The substances were digested according to the method recommended by the Ministry for Agriculture, Livestock and Supply of Brazil (MAPA) and by the two methods 3051A and 3052 of the United States Environmental Protection Agency (USEPA). By the USEPA method 3052, higher portions of the less soluble metals such as Ni and Pb were recovered, indicating that the conventional digestion methods for fertilizers underestimate the total amount of these elements. The results of the USEPA method 3051A were very similar to those of the method currently used in Brazil (Brasil, 2006). The latter is preferable, in view of the lower cost requirement for acids, a shorter digestion period and greater reproducibility.

O monitoramento dos teores de metais pesados nas áreas com uso intensivo de insumos agrícolas é de grande importância para a sustentabilidade agrícola e para a segurança alimentar. O objetivo deste trabalho foi avaliar os teores totais de metais pesados em solo e planta em áreas de mangueira com diferentes tempos de cultivo (6, 7, 8, 9, 10, 11, 14, 16, 17, 19 e 26 anos), em Petrolina (PE). Foram coletadas amostras de solo nas profundidades de 0-20 e 20-40 cm e de folhas de mangueira na fase vegetativa. Áreas de vegetação nativa (caatinga), adjacentes às áreas cultivadas, foram utilizadas para comparação. As concentrações totais de metais pesados (Cu, Cr, Fe, Zn, Mn, Ni e Pb) foram determinadas em solos e folhas. O cultivo de mangueira proporcionou acúmulo superficial dos metais Cu e Zn e redução dos teores de Ni, Pb, Mn e Fe, tanto em superfície como em subsuperfície. As áreas cultivadas apresentaram contaminação por Cu, Zn e Cr, devendo ser feitos monitoramentos nessas áreas para evitar impactos ambientais. Os diferentes tipos de manejo das empresas no cultivo de manga proporcionaram deficiência e excesso de alguns micronutrientes nas áreas avaliadas. Ferro e Mn, no entanto, supriram a nutrição mineral da mangueira em todas as áreas. A presença de Cr nas folhas de mangueira sugere a necessidade de investigação da ocorrência desse metal nessas áreas cultivadas.

The monitoring of heavy metal concentrations in areas under intensive agriculture is essential for the agricultural sustainability and food safety. This paper evaluates the total contents of heavy metals in soils and mango trees in orchards of different ages (6, 7, 8, 9, 10, 11, 14, 16, 17, 19, and 26 years) in Petrolina, Pernambuco, Brazil. Soil samples were taken from the layers 0-20 cm and 20-40 cm, and mango leaves were collected in the growth stage. Areas of native vegetation (Caatinga) adjacent to the cultivated areas were used for comparison. The total concentrations of heavy metals (Cu, Cr, Fe, Zn, Mn, Ni, and Pb) were determined in soils and leaves. In general, mango cultivation led to Cu and Zn accumulation in the soil surface and to a reduction in the contents of Ni, Pb, Mn, and Fe in surface and subsurface. Since contamination by Cu, Zn, and Cr was detected, these areas must be monitored to prevent negative environmental impacts. For instance, the presence of Cr in mango tree leaves indicates the need to investigate the source of the element in these orchards. The management strategies of the different companies led to deficiency or excess of some metals in the evaluated areas. However, the Fe and Mn levels were adequate for the mineral nutrition of mango in all areas.

Fertilizantes e corretivos, ao serem aplicados nos solos, fornecem micronutrientes como impurezas residuais da sua fabricação, os quais podem ser importantes fontes para as culturas. Em decorrência disso, o objetivo deste trabalho foi quantificar os teores dos micronutrientes Zn, Cu, Fe, Mn e Ni em fertilizantes e corretivos comercializados no Nordeste brasileiro, visando avaliar o potencial desses insumos no fornecimento indireto de micronutrientes às culturas agrícolas. Os insumos analisados neste estudo (24 amostras de fertilizantes e 26 de corretivos) foram coletados nos Estados da Bahia e Pernambuco pelo Ministério da Agricultura, Pecuária e Abastecimento (MAPA) e digeridos pelo método 3051A (USEPA, 1998). As determinações dos micronutrientes foram feitas por espectrofotometria de absorção atômica. Amostras de fertilizante SRM 695 (National Institute of Standards and Technology - NIST) e spikes foram adicionadas para controle de qualidade das análises. Os fertilizantes fosfatados, em geral, apresentaram maiores teores de micronutrientes do que os demais produtos testados. Os fertilizantes e corretivos avaliados representam uma fonte de micronutrientes ao solo que não pode ser desprezada. No entanto, a real disponibilidade desses elementos aportados ao solo necessita ser avaliada em estudos com plantas, pois fatores como solubilidade dos insumos, absorção pelas culturas, reações com o solo e perdas por precipitação e lixiviação devem ser considerados.

Fertilizers and lime can carry several micronutrients as residual impurities, which can become a source of these elements for crops. This study quantified the concentrations of Zn, Cu, Fe, Mn, and Ni in fertilizers and lime sold in northeastern Brazil. The effect of these inputs on the indirect micronutrient supply to crops was evaluated. Extracts were obtained from 24 fertilizer and 26 lime samples, using the method 3051A (USEPA) and atomic absorption spectrophotometry for elemental analysis. A fertilizer sample (SRM 695 - National Institute of Standards and Technology - NIST) and spikes were added to monitor the analysis quality. In general, micronutrient concentrations were highest in phosphate fertilizers. Fertilizers and lime represent an important secondary source of micronutrients for the soil and should be considered in the management of soil fertility. However, the real availability of micronutrients from these materials must be assessed with plants in field experiments, since aspects such as solubility, reactions with soil, and leaching losses can affect the actually available amount for plant uptake.

O bário (Ba) é um metal alcalino terroso de ocorrência natural no solo. É constituinte de carbonatos, sulfatos e silicatos e ocorre como substituto isomórfico de elementos como Ca e K nos minerais. Quando disponível em elevados teores no solo, o Ba pode causar toxidez a diversos organismos vivos. Para considerar que determinado solo está livre de contaminação por esse elemento, faz-se necessário conhecer os teores de Ba nesse solo em condição natural. Portanto, a determinação de teores naturais de Ba em solos é essencial para a construção de uma legislação que sirva de base ao monitoramento e remediação de áreas contaminadas por esse elemento e que seja adequada à realidade pedológica local. Nesse contexto, o objetivo desta pesquisa foi determinar os teores naturais de Ba como base de referência de qualidade para os Solos de Referência do Estado de Pernambuco. Foram coletadas amostras dos dois primeiros horizontes dos 35 perfis de referência, as quais foram submetidas à digestão ácida em micro-ondas (método 3051A). Nos extratos obtidos foi efetuada a determinação dos teores de Ba por ICP-OES. Observaram-se teores de Ba superiores aos valores de prevenção e de investigação estabelecidos pela legislação brasileira (CONAMA, 2009), corroborando a necessidade de maior conhecimento das diversidades regionais para a elaboração de normas nacionais. Os teores naturais de Ba determinados nos solos podem ser utilizados como base para a definição dos valores de referência de qualidade para Ba nos solos de Pernambuco, de acordo com o preconizado pela legislação nacional.

Barium is an alkaline-earth metal that occurs naturally in soils. It is present in soil in carbonates, sulphates and silicates as well as in the isomorphic substitution of calcium and magnesium in clay minerals. When available at high soil concentrations, Ba is toxic to several living organisms. To rule out the possibility of metal contamination of a particular soil, the natural metal concentrations of this soil must be known. Therefore, the natural soil concentrations of metals must be determined for soil monitoring and remediation, taking the local soil conditions into account. This study determined the natural Ba concentrations as threshold levels of this metal in reference soils of the state of Pernambuco. Samples from the two upper horizons of the 35 benchmark soil profiles were submitted to microwave-assisted acid digestion using method 3051A. Afterwards, the Ba concentration in extracts was obtained by ICP-OES. Ba concentrations above the prevention and investigation values according to the Brazilian guidelines (CONAMA, 2009) were observed. This corroborates the importance of a deeper knowledge of the regional soil diversity underlying national guidelines. The natural Ba concentrations determined in the soils can be used to define the Reference Quality Levels (natural concentration) in soils of Pernambuco, according to the Brazilian legislation.

Metais pesados formam um grupo de elementos com particularidades relevantes e de ocorrência natural no ambiente, como elementos acessórios na constituição de rochas. Esses elementos, apesar de associados à toxidez, exigem tratamento diferenciado em relação aos xenobióticos, uma vez que diversos metais possuem essencialidade (Fe, Mn, Cu, Zn e Ni) e benefício (Co) comprovados para as plantas. Nesse contexto, o objetivo deste trabalho foi determinar os teores naturais dos metais Fe, Mn, Zn, Ni, Cu e Co nos solos de referência de Pernambuco. Foram coletadas amostras de solo nas três regiões fisiográficas (Zona da Mata, Agreste e Sertão), dos dois primeiros horizontes dos 35 solos de referência do Estado de Pernambuco. A digestão das amostras baseou-se no método 3051A (USEPA, 1998), e a determinação foi efetuada em ICP-OES. Correlações significativas foram estabelecidas entre os metais e entre estes e a fração argila do solo, em ambos os horizontes, indicando a associação comum da maioria dos metais com solos mais argilosos. A maioria dos solos apresentou teores de Fe, Mn, Zn, Cu, Ni e Co menores que os de solos de outras regiões do País, com litologia mais máfica, o que corrobora o fato de que os teores desses elementos são mais diretamente relacionados aos minerais Fe-magnesianos. Os resultados indicam baixo potencial dos solos de Pernambuco em liberar Cu, Co e Ni para plantas, enquanto deficiências de Zn, Fe e Mn são menos prováveis. Os teores naturais de Fe, Mn, Zn, Cu, Ni e Co determinados podem ser utilizados como base para definição dos Valores de Referência de Qualidade para os solos de Pernambuco, de acordo com o preconizado pela legislação nacional.

Heavy metals are a group of elements with specific features and natural occurrence in the environment, representing an accessory in the formation of rocks. These elements, although associated with toxicity, must be treated different from xenobiotics, since many metals are evidentially essentials (Fe, Mn, Cu, Zn, and Ni) and beneficial (Co) for plants. In this context, the objective was to determine the natural contents of the metals iron (Fe), manganese (Mn), zinc (Zn), nickel (Ni), copper (Cu) and cobalt (Co) in benchmark soils of Pernambuco. Soil samples were collected in the three physiographic regions of the state (Zona da Mata, Agreste and Sertão), in the first two horizons of the 35 benchmark soils of the state of Pernambuco. Sample digestion was based on the method 3051A (USEPA, 1998) and determined by ICP-OES. Significant correlations were found between these metals and those with the clay soil fraction in both horizons, indicating the general association of most metals to the most clayey soils. The Fe, Mn, Zn, Cu, Ni, and Co contents of most soils were lower than in soils from other regions of the country and more mafic lithology, which confirms that the contents of these elements are more directly related to iron-magnesium minerals. The results indicate a low capacity of the soils of Pernambuco to release Cu, Co and Ni to plants, while deficiencies of Zn, Fe and Mn are less likely. The natural contents of Fe, Mn, Zn, Cu, Ni, and Co determined here can be used as a basis for defining the Quality Reference Values for soils of Pernambuco, as stipulated by the Brazilian legislation.

A baixa degradabilidade no solo de quelantes sintéticos usados para induzir a fitoextração pode significar elevado risco ambiental pela lixiviação de metais pesados. Agentes quelantes naturais, mais rapidamente degradados no solo, podem ser uma alternativa para os quelantes sintéticos. Este trabalho objetivou avaliar a capacidade de três agentes quelantes sintéticos e dois quelantes naturais de cadeia alifática na dessorção de Pb de um Espodossolo contaminado pela deposição de escórias resultantes da reciclagem de baterias automotivas. A lixiviação de Pb promovida pelos quelantes foi também estudada. O trabalho compreendeu dois experimentos: (1) dessorção de Pb utilizando as concentrações de 0, 2, 5, 10, 20 e 30 mmol kg-1 dos ácidos cítrico e oxálico e dos quelantes sintéticos EDTA, DTPA e NTA; (2) lixiviação realizada em colunas de PVC com concentrações de 0, 10 e 20 mmol kg-1 de ácido cítrico, ácido oxálico, EDTA e NTA. O uso do EDTA promoveu elevada dessorção e lixiviação de Pb, não sendo recomendado para programa de fitoextração na área em estudo. A elevada dessorção de Pb, aliada à baixa lixiviação promovida pelo NTA, qualifica o quelante para indução da fitoextração de Pb no solo. Os quelantes naturais não apresentaram riscos para a lixiviação de Pb nas concentrações estudadas, mas parecem pouco promissores para a fitoextração do elemento, devido à baixa dessorção.

Synthetic chelants used to induce phytoextraction are barely degraded in the soil and pose high environmental risks owing to metal leaching. Natural chelating agents can be an alternative to synthetic chelates thanks to their rapid biodegrability. The study was carried out to evaluate the efficiency of Pb desorption of three synthetic chelators and two natural aliphatic acids from a soil contaminated with Pb from a car battery recycling. Additionally, effects of the amendments on Pb leaching from soil were also studied. The study was based on two experiments carried out to investigate: (1) Pb desorption from soil using 0, 2, 5, 10, 20, and 30 mmol kg-1 of citric and oxalic acids, and synthetic chelators EDTA, DTPA and NTA; (2) Pb leaching from soil columns by applying citric and oxalic acids, EDTA, and NTA to the soil at concentrations of 0, 10, and 20 mmol kg-1. EDTA application resulted in the highest Pb desorption and leaching; the substance is therefore not recommended for phytoextraction programs in the area. NTA caused high Pb desorption along with low leaching, which qualifies the substance for enhancing Pb phytoextraction in field conditions. Neither citric nor oxalic acid posed risks regarding Pb leaching. On the other hand, they seem little promising for enhancing Pb phytoextraction in view of the low Pb desorption.

Apesar da reciclagem agrícola de lodo de esgoto ser uma das formas mais viáveis de disposição final deste resíduo, plantas cultivadas em áreas que receberam aplicações de lodo podem apresentar risco de contaminação por metais pesados. O objetivo deste trabalho foi estudar a distribuição dos metais Cd, Cu, Zn, Mn e Fe em plantas de milho cultivadas em solo adubado com lodo de esgoto da Companhia Pernambucana de Saneamento - COMPESA. Com esta finalidade, seis doses do resíduo (0; 7,7; 15,4; 29,7; 45,1 e 60,5t ha-1) foram aplicadas a um Argissolo Amarelo em condições de campo. Os teores dos metais foram determinados em cinco partes das plantas de milho: colmo, folha, pendão, palha que envolve a espiga e grãos. Os resultados demonstraram que a absorção de Zn pelas plantas de milho aumentou com a adição de lodo de esgoto, sendo o elemento acumulado principalmente na palha que envolve a espiga e na folha. Este aumento de absorção de Zn provocou diminuição dos teores de Cu nas plantas tratadas com lodo. A adição de lodo proporcionou aumentos na concentração de Fe em todas as partes da planta, com exceção dos grãos. O Mn foi acumulado, principalmente, no pendão e no colmo das plantas de milho. A aplicação de lodo de esgoto em solo cultivado com milho não proporcionou fitotoxicidade ou contaminação dos grãos produzidos por nenhum dos metais estudados.

Despite of sewage sludge agricultural recycling is one of the most adequate forms for sludge final disposal, plants grown in sludge-amended areas are under the risk of heavy metal contamination. This study was aimed at studying the distribution of Cd, Cu, Zn, Mn, and Fe in corn plants grown on soil treated with the sewage sludge from Companhia Pernambucana de Saneamento (COMPESA), Pernambuco state, Brazil. The sludge was applied to an Ultisol at six doses (0, 7.7, 15.4, 29.7, 45.1, and 60.5t ha-1). Heavy metal concentrations were determined in various plant parts (stem, leaves, stalk, straw involving the cob, and grains). The results showed that addition of sludge increased the Zn uptake by plants, with Zn accumulating mainly in the straw involving the cob and leaves. This increase in Zn absorption decreased Cu concentration in plants grown in sludge-treated soils. Except for grains, Fe concentrations were increased in all the plant parts due to sludge addition. On the other hand, most Mn was mainly accumulated in stalk and stem of the corn plants. Sewage sludge application on soil cultivated with corn did provoke neither phytotoxicity nor grains contamination with the heavy metals studied.