Adriana Maria de Aguiar Accioly

Phytoextraction and fractionation of heavy metals in soil after multiple applications of natural chelants

Fitoextracao de metais induzida por quelantes e uma tecnica promissora para despoluicao de solos. Entretanto, os quelantes mais eficientes sao sinteticos e apresentam baixa taxa de biodegradacao, o que aumenta o risco de lixiviacao de metais. Acidos orgânicos tem sido propostos para auxiliar na fitoextracao, mas a sua rapida degradacao pode ser limitante para a eficiencia desta tecnica. O objetivo do trabalho foi comparar a eficiencia de aplicacoes sucessivas dos acidos citrico e galico, na disponibilidade, absorcao e acumulacao de Cd, Pb, Cu e Zn pela mucuna preta (Stizolobium aterrimum). O solo foi contaminado com Cd, Pb, Cu e Zn nas doses 20, 150, 100 e 150 mg kg-1, respectivamente, e cultivados por 35 dias. Os acidos foram aplicados de tres formas: uma aplicacao de 5 mmol kg-1 no 28° dia de cultivo da mucuna; duas aplicacoes de 5 mmol kg-1 no 28° e 31° dia; e tres aplicacoes de 5 mmol kg-1 no 28°, 31° e 34° dia de cultivo. As amostras de solo foram submetidas a extracao e fracionamento quimicos. Os acidos orgânicos testados nao foram eficientes na inducao da fitoextracao. Em geral, a aplicacao dos acidos aumentou as concentracoes de metais tanto nas fracoes soluveis como em agua e tambem na trocavel. Zinco e cobre ficaram retidos principalmente na fracao materia orgânica. O Zn, apos aplicacao dos acidos, foi remobilizado da fracao materia orgânica para as fracoes soluvel em agua e trocavel. Os acidos orgânicos mobilizaram Pb e Cu dos oxidos de ferro, mas este aumento na solubilidade nao foi suficiente para favorecer a fitoextracao.

Disponibilidade, acúmulo e toxidez de cádmio e zinco em milho cultivado em solo contaminado

A greenhouse experiment was carried out to evaluate: (a) the soil Cd and Zn availability to maize plants with and without liming, using the DTPA, EDTA, Mehlich-1, and Mehlich-3 extractants; (b) The effect of Cd and Zn doses on plant growth and metal accumulation in maize; and (c) toxicity symptoms and anatomical changes in leaves and roots exposed to Cd and zinc. Maize was grown for 30 days in soil contaminated with either Cd (0, 1, 3, 5, 10, 20 mg kg-1) or Zn (0, 10, 30, 50, 100, 150 mg kg-1). Highly significant correlations were found between all extractants tested and metal plant contents. The metal addition to soil reduced biomass production and increased Cd and Zn plant contents. The critical toxicity value for Cd in soil varied from 8.7 to 13.1 mg kg-1, whereas for Zn this value lied between 74.1 to 110.7 mg kg-1, depending on liming and extractant type. Interveinal and marginal chlorosis together with necrosis in the leaf apex and along the margins were observed for Zn treatments. On the other hand, leaf chlorosis, shriveling and curling were the most common symptoms in cadmium-damaged plants. Increased cell wall lignification in vascular tissues, epidermis, collenchyma, and endoderm cells were associated to critical toxicity values of Cd and Zn in soil.

FITORREMEDIAÇÃO DE SOLO SALINO SÓDICO POR Atriplex nummularia E GESSO DE JAZIDA (1)

The cultivation of Atriplex nummularia on saline-sodic soils is economically attractive because it can be used as a forage crop as well as in landscape projects. The potential of Atriplex nummularia for phytoextraction of Na+ from a saline-sodic soil irrigated with saline water was evaluated. Additionally, gypsum was tested for improving phytoremediation. The experiment was set up as a randomized block design, in a 2 x 3 factorial scheme. The treatments consisted of: no gypsum and 50 % of the regularly recommended gypsum dose, and three salinity levels of irrigation water: C1 = 175 μS cm -1; C2 = 500 μS cm -1; C3 = 1,500 μS cm -1. The Na concentration in plant tissues and soil were evaluated 40, 70, 100 and 130 days after A nummularia transplanting. The results showed that there was a 96 % increase in root dry matter as a result of gypsum application. Sodium accumulation in shoots increased significantly in the third (90.1 g kg-1) and fourth (109.7 g kg-1) sampling period. This effect was magnified by gypsum application. After 100 days, the soil Na+ content had decreased by 31 and 26 %, with and without gypsum addition, respectively. Our results indicate that A. Nummularia is a Na+ accumulator species. Gypsum was effective as a phytoextraction enhancer. A. nummularia irrigation aiming at Na phytoremediation is possible with saline water varying from 175 to 1,500 μS cm-1.

Distribuição de metais pesados em plantas de milho cultivadas em Argissolo tratado com lodo de esgoto

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.

ÁCIDOS HÚMICOS E CARVÃO VEGETAL ATIVADO COMO AMENIZANTES EM SOLO CONTAMINADO POR CHUMBO (1)

Soil contamination by Pb poses a significant risk to human health. The municipality of Santo Amaro da Purificacao, Bahia, Brazil, has one of the most severe cases of contamination of this metal in the world. The objective of this study was to evaluate the effect of humic acids and activated charcoal as soil amendments for reducing the toxicity of Pb to corn plants grown in contaminated soil collected near the area of the company responsible for the contamination. Application rates were based on the C content of the materials (humic acid from composting -AHv, commercial humic acid - AHc, and charcoal - CV) and corresponded to 0, 0.75, 1.5, 3 and 7.5 g kg-1 of C in the soil. At 43 days of growth, the plants were cut at ground level, separated into shoots and roots, and Pb contents were determined by nitro-perchloric digestion. The concentrations of chlorophyll a and b were also evaluated to evaluate the effect of the metal on the photosynthetic apparatus. The soil amendments applied to contaminated soil were effective in reducing the stress of Pb in corn plants. The highest efficiency was obtained from AHv, followed by CV and AHc. All the soil amendments tested decreased translocation of Pb to the shoots. This implies a greater fixation of the metal in the soil and, consequently, a reduction in the risk of transfer to the food chain. For this reason, these materials can be recommended as soil amendments for Pb phytostabilization in soils.

Silicato de cálcio como amenizante da toxidez de metais pesados em mudas de eucalipto

The objective of this study was to evaluate the effect of calcium silicate to reduce heavy metal toxicity in Eucalyptus camaldulensis seedlings. Five doses of calcium silicate (0, 1.6, 3.2, 4.8, and 6.4 g kg -1 ) were used in soils with increasing levels of contamination. The experiment was carried out in pots with 1.5 kg of soil, with one plant each, in a 4x5 factorial array (four levels of contamination x five silicate doses). Calcium silicate minimized heavy metal toxicity to E. camaldulensis, delayed the onset of toxicity symptoms, and decreased zinc and cadmium shoot concentrations. However, calcium silicate did not completely overcome the depressive effect upon plant growth in soils with high metal concentrations. Calcium silicate effects increased with increasing doses and were more evident in highly contaminated soils. The beneficial effects of calcium silicate on metal toxicity were highly related to the decrease in zinc translocation to the eucalyptus shoots.

Industrial and urban organic wastes increase soil microbial activity and biomass

Microbial processes have been used as indicators of soil quality, due to the high sensitivity to small changes in management to evaluate, e.g., the impact of applying organic residues to the soil. In an experiment in a completely randomized factorial design 6 x 13 + 4, (pot without soil and residue or absolute control) the effect of following organic wastes was evaluated: pulp mill sludge, petrochemical complex sludge, municipal sewage sludge, dairy factory sewage sludge, waste from pulp industry and control (soil without organic waste) after 2, 4, 6, 12, 14, 20, 28, 36, 44, 60, 74, 86, and 98 days of incubation on some soil microbial properties, with four replications. The soil microbial activity was highly sensitive to the carbon/nitrogen ratio of the organic wastes. The amount of mineralized carbon was proportional to the quantity of soil-applied carbon. The average carbon dioxide emanating from the soil with pulp mill sludge, corresponding to soil basal respiration, was 0.141 mg C-CO2 100 g-1 soil h-1. This value is 6.4 times higher than in the control, resulting in a significant increase in the metabolic quotient from 0.005 in the control to 0.025 mg C-CO2 g-1 Cmic h-1 in the soil with pulp mill sludge. The metabolic quotient in the other treatments did not differ from the control (p < 0.01), demonstrating that these organic wastes cause no disturbance in the microbial community.

Bioconcentração de chumbo e micronutrientes em hortaliças cultivadas em solo contaminado

RESUMO - A crescente poluicao ambiental nas ultimas decadas vem tornando os metais pesados uma ameaca constante aos seres vivos. Entre estes, o chumbo (Pb) e um dos mais importantes, devido a quantidade de areas contaminadas e seus efeitos deleterios para saude humana. Este estudo objetivou avaliar a producao de biomassa e absorcao de micronutrientes por olericolas cultivadas em Espodossolo contaminado por Pb. Adicionalmente, a distribuicao de Pb entre as fracoes do solo e a relacao dessas fracoes com a disponibilidade do Pb para hortalicas foi tambem estudado. O experimento foi conduzido em blocos casualizados no esquema fatorial 5x3x4. Os tratamentos foram constituidos por cinco doses de Pb (0,0; 20; 50; 72 e 180 mg kg -1 de solo), tres especies vegetais (quiabo, cenoura e couve-manteiga) e quatro partes das plantas (raiz, caule, folha e partes comestiveis), sendo a ultima dose equivalente ao valor de investigacao para solos agricolas. De acordo com os resultados, o Pb promoveu reducao da materia seca nas plantas de cenoura e quiabeiro, enquanto nao influenciou a producao de biomassa da couve manteiga. O Pb afetou a concentracao de micronutrientes nos orgaos das hortalicas, sendo observado na cenoura reducao no teor de ferro enquanto na couve manteiga houve aumento do teor de Zn nas raizes. O Pb apresentou-se, preferencialmente, adsorvido a fracao materia orgânica. Plantas cultivadas em solo contaminado com a dose de investigacao estabelecida pelo CONAMA, alem de apresentarem desbalanco nutricional, podem tornar-se inadequadas ao consumo humano, devido ao elevado teor deste metal nas partes comestiveis. Palavras-chave: Hortalicas. Solo-poluicao. Plantas-efeito de metais pesados.

Parâmetros indicadores do potencial de mineralização do nitrogênio de compostos orgânicos

EnglishThe objective of the present study was to evaluate the relationships between the chemical characteristics of 15 types of organic composts and the release of nutrients to the soil. Laboratory soil incubations were carried using plastic cups, where 50 g of a dystrophic Red Yellow Argisol (Ultisol) were amended with 0.374 g of each compost. The design was in randomized blocks with 16 treatments (15 types of compost plus a control) and 4 incubation periods (3, 7, 14 and 28 days) with three replications. At the end of each period, the soil inorganic N was determined, but soil P, K, Ca and Mg were determined only at day 28. The composts had different effects on soil N, causing from mineralization to immobilization. Among the evaluated characteristics of the composts (lignin, poliphenols, ashes, C, N, P, K, Ca, Mg, lignin:N, and C:N) only the C:N ration had a significant correlation with N mineralization. The composts also varied regarding the supply of P and K to the soil, but there were no differences in the supply of Ca and Mg. In conclusion, the chemical characteristics of the composts that were evaluated were not useful indicators of the potential nutrient supply by the composts portuguesO presente trabalho objetivou avaliar as relacoes entre caracteristicas quimicas de 15 tipos de compostos orgânicos e o fornecimento de nutrientes para as plantas. Para isso, experimentos de incubacao de solo foram montados em laboratorio, utilizando-se copos plasticos contendo 50 g de um Argissolo Vermelho-Amarelo distrofico, no qual foram incorporados 374 mg de massa seca dos compostos. O delineamento experimental foi em blocos casualizados com 16 tratamentos (15 compostos e testemunha), 4 tempos de incubacao (3, 7, 14 e 28 dias) e 3 repeticoes. Em cada data de coleta analisou-se o teor de N inorgânico do solo e, aos 28 dias, determinaram-se o P, K, Ca e Mg do solo. Das variaveis estudadas (lignina, polifenois, cinzas, C, N, P, K, Ca, Mg, lignina/N e C/N), apenas a relacao C/N apresentou uma fraca correlacao positiva com a mineralizacao de nitrogenio. Observaram-se diferencas entre os compostos no fornecimento de P e K ao solo, mas nao houve diferencas quanto ao Ca e Mg. Conclui-se que as caracteristicas quimicas avaliadas dos compostos testados nao demonstraram promissoras como indicadoras do potencial de fornecimento de nutrientes pelos compostos

Guideline Values and Metal Contamination in Soils of an Environmentally Impacted Bay

Estimating soil guideline values for metals in environmentally impacted areas is challenging due to the contamination spreading. All Saints Bay holds the most important petrochemical complex in the southern hemisphere and an abandoned Pb smelter plant that left tons of slag rich in Pb, Cd, and Zn untreated. The aim of the study was to determine the background concentration of the metals Pb, Cr, Zn, Cu, Ni, Cd, and Co in topsoils of this environmentally impacted bay in order to establish soil guideline values and pollution indices for the monitoring of metal contamination. A total of 114 soil samples across the bay were taken from 38 samplings sites with minimal human activity. Concentrations of Pb, Cr, Zn, Cu, Ni, Cd, and Co in extracts were determined by inductively coupled plasma optical emission spectroscopy after microwave digestion. Soil guideline values, geo-accumulation, and pollution index were estimated. The natural concentration of Pb in soils was clearly influenced by smelting activities and hindered the establishment of a soil guidelines value for lead. Geo-accumulation data indicated that soils are contaminated with Pb, Co, Ni, Zn, and Cu. High pollution indices for Co, Pb, and Ni in the vicinity of the abandoned Pb plant smelter demonstrate that soils were influenced by this anthropogenic source of metals. Soils around the biggest city in the bay were also contaminated with Pb and chromium.