Adailson Pereira de Souza

Citric acid-assisted phytoextraction of lead: a field experiment.

Soil contamination with heavy metals has become a serious environmental problem that requires affordable strategies of remediation. This study was carried out to assess the performance of maize and vetiver in the phytoextraction of Pb from a soil contaminated by battery recycling activities. The species were planted with different spacings between rows (0.80, 0.65 and 0.50m). Citric acid (40mmolkg(-1)) was applied on each experimental plot on the 61st d of cultivation in order to solubilize the Pb and assist the phytoextraction. The results showed that the chelating agent promoted a 14-fold increase in the Pb concentration in maize shoots as compared to the control, which accumulated only 111mgkg(-1) of the metal. The citric acid induced a Pb concentration in vetiver shoots that was 7.2-6.7-fold higher than the control at both the 0.65 and 0.50m plant spacing, respectively. The use of citric acid increased substantially the uptake and translocation of Pb to the shoots, regardless of plant spacing. Citric acid was efficient in solubilizing Pb from the soil and inducing its uptake by both species. Environmentally-friendly and cost effective, commercial citric acid is recommended for assisting Pb-phytoextraction in the studied area. Due to the low natural solubility of Pb and a time frame needed of longer than 150yr to accomplish the clean-up, phytoextraction with no chelate assistance is not recommended for the area.

Nitrate production and accumulation in lettuce as affected by mineral Nitrogen supply and organic fertilization

Lettuce is one of the leading vegetables in Brazil. However, studies concerning its fertilization for the Northeastern region of the country are still scarce. This work was carried out to evaluate the effects of mineral Nitrogen supply and organic fertilization on the production and nitrate accumulation in lettuce, cultivar Elba, in the semi-arid zone of Paraiba, Brazil. A randomized block design, with four replications, was used to test five doses of cattle manure (30; 60; 90; 120, and 150 t ha-1), five doses of N supplied as urea (30; 60; 90; 120, and 150 kg ha-1), and a control without fertilization. Along with mineral N, the other nutrients were also supplied using mineral sources. No additional nutrients were supplied where organic fertilization was used. Lettuce yield was significantly higher when organic fertilization was used, compared to the mineral nutrient supply. Taking into account most of the fertilization doses recommended for growing lettuce in the Brazilian Northeastern States, N mineral fertilization in sandy soils with low organic matter contents can be fully replaced by organic fertilization with cattle manure. Plant total (PTY) and commercial yield (PCY) as affected by the mineral N supply fitted into a quadratic model, in which the doses 94.5 and 95.7 kg ha-1 corresponded to respectively the highest PTY (381.9 g plant-1) and PCY (321.6 g plant-1). Where organic fertilization was used, PTY and PCY fitted into a linear model. Therefore, the highest PTY (523.9 g plant-1) and PCY (449.48 g plant-1) were observed at the highest manure doses. Nitrate content on roots, stems, and leaves increased linearly with Nitrogen and manure application. In roots, the nitrate content (mg kg-1 of fresh matter) reached 93.96 (N mineral (Nm)) and 65.09 (organic fertilization (OF)); in stems, 183.45 (Nm) and 98.22 (OF); and in leaves, 121.98 (Nm) and 75.62 (OF). The maximum nitrate content observed in leaves was far below the risk level for human health.

Indicadores biológicos de qualidade do solo em diferentes sistemas de uso no brejo paraibano

A avaliacao da qualidade do solo e uma ferramenta importante para monitorar a sua degradacao, bem como planejar a implantacao de praticas sustentaveis de manejo. Neste trabalho, objetivou-se avaliar indicadores biologicos de qualidade do solo em um Latossolo Amarelo distrofico, submetido a diferentes sistemas de uso em Areia-PB. Foram utilizadas amostras de solo coletadas na camada aravel (0-20 cm) em areas de mata nativa, fruticultura, cana-de-acucar, sucessao de cultivos, pastagem e consorcio de culturas. Foram avaliados o carbono orgânico total (COT), carbono da biomassa microbiana (CBM), quociente microbiano (qMic), respiracao basal (RB) e quociente metabolico (qCO2). Os resultados obtidos indicaram que as areas sob gramineas apresentaram uma tendencia de manutencao do COT e menores reducoes no CBM, entretanto, apresentaram elevados valores de qCO2, indicando a ocorrencia de um processo degradativo. A area sob fruticultura apresentou leves reducoes no COT e CBM e baixos valores de qCO2, indicando que esse sistema pode estar se ajustando a um novo estado de equilibrio. As areas sob sucessao de cultivos e consorcio de culturas apresentaram as maiores reducoes no COT e CBM e elevados valores de qCO2, demonstrando um elevado estagio de degradacao desses sistemas. Pode-se concluir que todos os sistemas agricolas estudados promoveram perda de qualidade do solo, sendo esse fato mais pronunciado nas areas sob manejo mais intensivo. O CBM e qCO2 mostraram-se bastantes sensiveis as alteracoes decorrentes do uso agricola do solo, apresentando grande potencial para estudos de sua qualidade.

Respiração microbiana do solo sob doses de glyphosate e de imazapyr

A degradacao microbiana dos herbicidas no solo e influenciada por diversos fatores, dentre esses as caracteristicas fisicas e quimicas do solo e da propria molecula, que agem continuamente determinando a sua magnitude. Em razao da grande variabilidade de respostas apresentadas por essas moleculas no solo e das poucas informacoes sobre o seu comportamento em ambientes tropicais, no que diz respeito a sua degradacao, e que foi realizada uma serie de experimentos, em laboratorio, objetivando verificar a resposta da atividade microbiana do solo, pelo metodo da evolucao do CO2 do solo, sob doses crescentes do glyphosate e do imazapyr (0; 4; 8 e 12 L ha-1 do produto comercial Roundup S.Aq.C. e Arsenal 250 S.Aq.C., respectivamente), em solos de diferentes texturas e composicao quimica, sob tres conteudos de umidade (40, 70 e 100% do equivalente de umidade). Os resultados obtidos permitiram concluir que: a) a microbiota do solo e capaz de utilizar o glyphosate e o imazapyr como fontes de carbono; b) a umidade do solo influencia a capacidade de os microrganismos degradarem o glyphosate e o imazapyr; c) a umidade de 40%, nos solos avaliados, proporcionou as menores respostas da atividade dos microrganismos, independentemente das doses dos herbicidas; e d) o efeito das doses do imazapyr sobre a atividade microbiana do solo e influenciado pelas caracteristicas fisicas e quimicas dos solos.

Accumulation of dry matter and macronutrient in cultivars of irrigated banana tree

ABSTRACT - The knowledge about the quantity of dry matter and nutrients accumulated and exported by banana is important for the development of fertilizer recommendations. The objective of this study was to evaluate the accumulation of dry matter and macronutrients by six cultivars of irrigated banana crop. Plants of Grande Naine, Pacovan, Pacovan-Apodi, Prata-Ana, Terrinha and Gross Michel cultivars were sampled in a commercial plantation in the municipality of Limoeiro do Norte, state of Ceara, Brazil. At harvest, four plants of each cultivar were selected for sampling. The “mother-plant” was divided into rhizome, pseudo stem, petiole, leaf blade, stalk and fruits. In the dry matter of these parts, the contents of macronutrients were determined. The cultivars Pacovan, Prata Ana and Pacovan-Apodi, in general, extracted from the soil the largest amounts of macronutrients and these cultivars accumulated higher quantities of dry matter. The potassium and nitrogen were the most accumulated and exported macronutrients by the six cultivars of ir-rigated banana followed by sulphur, calcium, magnesium and phosphorus.ABSTRACT - The knowledge about the quantity of dry matter and nutrients accumulated and exported by banana is important for the development of fertilizer recommendations. The objective of this study was to evaluate the accumulation of dry matter and macronutrients by six cultivars of irrigated banana crop. Plants of Grande Naine, Pacovan, Pacovan-Apodi, Prata-Ana, Terrinha and Gross Michel cultivars were sampled in a commercial plantation in the municipality of Limoeiro do Norte, state of Ceara, Brazil. At harvest, four plants of each cultivar were selected for sampling. The “mother-plant” was divided into rhizome, pseudo stem, petiole, leaf blade, stalk and fruits. In the dry matter of these parts, the contents of macronutrients were determined. The cultivars Pacovan, Prata Ana and Pacovan-Apodi, in general, extracted from the soil the largest amounts of macronutrients and these cultivars accumulated higher quantities of dry matter. The potassium and nitrogen were the most accumulated and exported macronutrients by the six cultivars of ir-rigated banana followed by sulphur, calcium, magnesium and phosphorus.

Lixiviação de glyphosate e imazapyr em solos com diferentes texturas e composição química: I - método do bioensaio

A mobilidade dos herbicidas no perfil do solo e influenciada por varios processos, tais como, retencao, transformacao e transporte. O conhecimento destes fenomenos e fundamental para a perfeita compreensao do destino de tais produtos no ambiente. Dentre as varias tecnicas utilizadas nesses estudos, o metodo do bioensaio apresenta-se como de otima representatividade e reprodutibilidade. Em razao dessas caracteristicas, associadas a poucas informacoes sobre a mobilidade de herbicidas nos solos sob condicoes tropicais, foi conduzido um bioensaio objetivando verificar o movimento vertical do glyphosate e do imazapyr, em colunas de solos de diferentes texturas e composicao quimica, utilizando-se o tomateiro (Lycopersicon esculentum Mill var. Santa Clara) como planta-teste. Os resultados desse estudo permitiram concluir que: a) o limite de deteccao do bioensaio para o glyphosate e para o imazapyr corresponde ao menor valor de I50, obtido na curva padrao, 331,52 e 5,4 µg L-1, respectivamente; b) as concentracoes do glyphosate biologicamente ativo nos lixiviados dos solos de Vicosa e de Sabara encontram-se abaixo do limite de deteccao do bioensaio; c) o glyphosate apresentou, na coluna de 1 cm, mobilidade muito baixa nos solos estudados; d) a mobilidade do imazapyr, na coluna de 30 cm, e maior no solo de textura francoarenosa de Vicosa; e) o alto teor de argila e de materia orgânica do solo de Sabara apresentam-se como os principais fatores de retencao do imazapyr nesse solo.

Absorção e distribuição de chumbo em plantas devetiver, jureminha e algaroba

SUMMARY : ABSORPTION AND DISTRIBUTION OF LEAD IN VETIVER,MIMOSA AND MESQUITE PLANTS The use of plants for phytoremediation of metal-contaminated areas is an emergingtechnology, and studies concerning heavy metal tolerance, absorption and distribution inplants are essential for the success of such programs. This study was carried out to evaluatethe tolerance, absorption and distribution of lead (Pb) in vetiver grass [ Vetiveria zizanioides(L.) Nash], mimosa [ Desmanthus virgatus (L.) Willd] and mesquite trees [ Prosopis juliflora(SW) DC] subjected to increasing lead doses in solution. The experiment was conductedunder a screenhouse, at the DSER/CCA/UFPB, Areia-PB, Brazil. The species were grownin nutrient solution containing increasing Pb levels (0, 50, 100 and 200 mg L -1 ) during a 45-day exposure period. An entirely randomized split-plot design was used with threereplicates. The main plot was represented by the plant species and the subplot by Pblevels. The increased Pb levels caused significant reductions of dry mass of the root, shootand whole plant (root + shoot) in the three species under study. Based on critical toxicitylevels, the tolerance of vetiver to Pb contamination was higher than in the other species. Invetiver and mesquite plants, the roots were the component most sensitive to Pbcontamination, whereas a similar response to Pb by all plant components was observed formimosa. Total Pb concentrations and content in plant compartments were significantlyaffected by the increasing Pb levels in solution, and a higher accumulation of this elementwas observed in the roots of the three species under study. The highest Pb concentrationand content were found in all compartments of vetiver, which suggests a high potential ofthis grass for phytoremediation of Pb-contaminated areas.Index terms: pollution, heavy metal, phytotoxicity, tolerance, phytoremediation.

SUBSTÂNCIAS HÚMICAS, ATIVIDADE MICROBIANA E CARBONO ORGÂNICO LÁBIL EM AGREGADOS DE UM LATOSSOLO VERMELHO DISTRÓFICO SOB DUAS COBERTURAS VEGETAIS

Organic matter is an indicator of the soil quality. Knowledge about its different components, explaining the influence of management practices on organic matter and soil aggregation, is essential for the sustainability of agricultural systems. In the present work, we evaluated humic substances, microbial activity and labile organic carbon in a Dystrophic Red Latosol from Minas Gerais state, Brazil, under natural vegetation (Cerradao) or under 30-years of conventional corn cultivation. Soil samples were collected from depths of 5-10 and 15-20 cm at four different sites. Then the samples were dried and fractioned in aggregate classes (diameter 4.75-2.0; 2.0-1.0; 1.0-0.5; 0.5-0.25; 0.25-0.105; and less than 0.105 mm). Furthermore, organic carbon of fulvic acid (AF), humic acids (AH) and humins (HUM) fractions, and labile organic carbon (COL) using KMnO4 15.6 and 33.0 mmol L-1 of the samples were determined. The material was further subjected to a respirometry test, in which CO2 production values were adjusted to logistic equations [Y = a/1 + e-(b + cx)] to estimate the time needed to achieve half of the maximum CO2 (t1/2), production. Results showed higher mean organic carbon contents in the AH fraction and COL with KMnO4 33.0 mmol L-1 of soil aggregates under conventional tillage. For AF and HUM fractions and COL with KMnO4 15.6 mmol L-1 this behavior was only observed in the 15-20 cm layer. The highest CO2 production was observed in the aggregates of the soil under Cerradao. The smaller aggregates tended to present higher organic carbon contents in the AF and AH fractions and COL. These were responsible for the highest CO2 production and constituted favorable sites of organic matter storage, due to the physical and chemical protection, as well as for mineralization, since microorganisms prefer these sites. The coefficients of the logistic equation (a, b, c) and the t1/2 can be considered important indicators of organic matter quality and lability under different managements.

Doses de nitrogênio no acúmulo de nitrato e na produção da alface em hidroponia

Lettuce production in hydroponic system presents growing expansion in Brazil, but still there are problems of quality and risk of nitrate accumulation. This work was carried out to evaluate the lettuce production and nitrate accumulation in hydroponic system depending on the increasing levels of nitrogen in the nutrient solution. The experiment was conducted in greenhouse of the Universidade Federal da Paraiba, Brazil. The lettuce plants were grown in nutrient solution containing increasing levels of N (11, 13, 15, 17, 19 and 21 mmol L-1) during a 25-day period. An entirely randomized design with four replications was used. Plant total yield (PTT), plant commercial yield (PCM) and nitrate contents in the fresh matter of roots, stems and leaves of the lettuce were evaluated. There were no significant effects of increasing levels of N in nutrient solution on PTT and PCM, average values of 357.3 and 352.5 g/plant being observed, respectively. The increased levels of N in nutrient solution increased linearly nitrate content on all lettuce parts. The nitrate content reached 659, 623 and 615 mg/kg in the fresh matter of roots, stems and leaves, respectively, at the highest N level. Nevertheless, the maximum nitrate content observed in leaves was far below the risk level for human health.

Kinetics of phosphorus sorption in soils in the state of Paraíba

The soil P sorption capacity has been studied for many years, but little attention has been paid to the rate of this process, which is relevant in the planning of phosphate fertilization. The purpose of this experiment was to assess kinetics of P sorption in 12 representative soil profiles of the State of Paraiba (Brazil), select the best data fitting among four equations and relate these coefficients to the soil properties. Samples of 12 soils with wide diversity of physical, chemical and mineralogical properties were agitated in a horizontal shaker, with 10 mmo L-1 CaCl2 solution containing 6 and 60 mg L-1 P, for periods of 5, 15, 30, 45, 60, 90, 120, 420, 720, 1,020, and 1,440 min. After each shaking period, the P concentration in the equilibrium solution was measured and three equations were fitted based on the Freundlich equation and one based on the Elovich equation, to determine which soil had the highest sorption rate (kinetics) and which soil properties correlated to this rate. The kinetics of P sorption in soils with high maximum P adsorption capacity (MPAC) was fast for 30 min at the lower initial P concentration (6 mg L-1). No difference was observed between soils at the higher initial P concentration (60 mg L-1). The P adsorption kinetics were positively correlated with clay content, MPAC and the amount of Al extracted with dithionite-citrate-bicarbonate. The data fitted well to Freundlich-based equations equation, whose coefficients can be used to predict P adsorption rates in soils.