Maria Aparecida Pereira Pierangeli

Efeito do pH na adsorção e dessorção de cádmio em Latossolos brasileiros

Adsorption and desorption reactions of metals in soils are influenced by the surface of the soil colloid attributes and solution composition. This study evaluated the effect of the pH on Cd adsorption (Cdads) and desorption (Cddes) in l7 Brazilian Oxisol samples that differed in their chemical, physical and mineralogical attributes. Samples of each soil, suspended in 5 mmol L-1 Ca(NO3)2 (pH adjusted to 4.5; 5.5, and 6.5; ratio soil:solution 1:67) were placed to react with 0.20 mmol L-1 Cd(NO3)2 (final ratio soil:solution 1:100) for 72 h, after which they were centrifuged and the Cd concentration of the solution determined. Thereafter, 25 mL of 5 mmol L-1 Ca(NO3)2 were added to the remaining residue to desorb the Cd retained in the soil samples. An increase of the pH solution from 4.5 to 5.5, from 4.5 to 6.5 and from 5.5 to 6.5 caused a 1.3; 2.2 and 1.7-fold increase in the Cd adsorption, respectively. The mean percentage of Cd adsorbed (Cd%ads) was 27 (pH 4.5), 35 (pH 5.5) and 55% (pH 6.5). The effect of soil attributes on Cdads was only evidenced at a pH of 5.5 and 6.5, by the correlations between Cdads and the soil organic matter, specific superficial area (SSA), CEC at pH 7.0 (CEC), kaolinite, hematite, oxalate-and-DCB-Fe and clay contents. However, only CEC and clay content, at pH 5.5 and the SSA, at pH 6.5, were included in the model of Cdads prediction, obtained through regression analyses. The adsorption in values of higher pH did not propitiate reduction in Cddes, which was around 20% for pH 4.5 and 40% for pH 5.5 and 6.5. The small proportions of Cd adsorbed by these Oxisols, mainly at lower pH values, which are an indication of high mobility and bioavailability, reinforces the need for the adoption of appropriate criteria to use or discard residues containing Cd in agricultural areas or close to aquifers.

Comportamento sortivo, individual e competitivo, de metais pesados em Latossolos com mineralogia contrastante

The pollution effect of trace elements in the environment depends mainly on the capacity of soil colloids to sorb and maintain them in high energy bonds. This study evaluated the adsorption of Cd, Cu, and Pb in A-horizon samples of Red Latosol and Red-Yellow Latosol (Udox), with similar texture and contrasting mineralogy. For this purpose, isotherms of adsorption, monoelement and multielement were built, based on the soil sample reaction in 5 mmol L-1 Ca(NO3)2 solution adjusted to pH 5.5, with metal concentrations of 0; 0.01; 0.05; 0.10; 0.15; and 0.75 mmol L-1. Desorption was then analyzed in 5 mmol L-1 Ca(NO3)2 solution. The isotherms were adjusted to the Langmuir model (P < 0.01). The maximum adsorption capacity of Cu and Pb was higher than of Cd in both soils. The simultaneous adsorption reduced the adsorption maximum capacity of the three metals. Cd was most reduced, indicating the lower competitive power than Cu and Pb. There was low reversibility of the adsorbed metals, indicating occurrence of hysteresis. The low competitive power of Cd, as indicated by the reduced maximum adsorption capacity in the presence of the other two metals, is alarming in weathered tropical soils, such as Oxisols.

Lead adsorption-desorption in Brazilian Oxisols as a function of pH

Reações de adsorção-dessorção de chumbo em solos são influenciadas por atributos de superfície dos colóides dos solos e pela composição da solução do meio. Este estudo avaliou o efeito do pH sobre a adsorção-dessorção de chumbo em Latossolos brasileiros. Amostras do horizonte A de cada solo, suspensas em Ca(NO3)2 5 mmol L-1, foram tituladas com HNO3 7 mmol L-1 ou solução saturada de Ca(OH)2, para que fosse atingido o valor de pH estipulado em cada experimento (4,5, 5,5 e 6,5). Atingido o pH de equilíbrio, as amostras foram equilibradas com Pb(NO3)2, com vistas em obter uma concentração final de 0,15 mmol L-1 (relação solo:solução 1:100; força iônica 15 mmol L-1), por um período de 72 h. A dessorção foi realizada em Ca(NO3)2 5 mmol L-1, pH 5,5. O aumento do pH de 4,5 para 6,5 causou aumento da adsorção de até 16,7 vezes, um aumento médio de 2,9 vezes de pH 4,5 para 5,5; 1,4 vez de pH 5,5 para 6,5 e 4,2 vezes de pH 4,5 para 6,5. A relação Pbadsorvido/Pbadicionado foi, em média, de 0,33 para pH 4,5; 0,75 para pH 5,5 e 0,94 para pH 6,5. A fração média de Pb dessorvido (Pbdessorvido/Pbadsorvido) decresceu de 0,36 a pH 4,5, para < 0,06 a pH 6,5. O efeito dos atributos do solo sobre a adsorção-dessorção de chumbo decresceu quando o pH aumentou, evidenciado por uma maior diferenciação na quantidade adsorvida pelos solos em valores mais baixos de pH. A adsorção de Pb foi positivamente correlacionada (e geralmente a fração dessorvida foi negativamente correlacionada) com área superficial específica, CTC a pH 7,0, teores de caulinita, hematita, Fe2O3 extraídos pelo ditionito-citrato-bicarbonato de sódio e oxalato ácido de amônio e SiO2 e Fe2O3 extraídos pelo ataque sulfúrico. O fato de considerável fração de chumbo permanecer adsorvida em pH 4,5 mostra a reduzida disponibilidade deste metal em Latossolos, mesmo em baixos valores de pH.

Teores de As, Pb, Cd e Hg e fertilidade de solos da região do Vale do Alto Guaporé, sudoeste do estado de Mato Grosso

The fertility and trace elements diagnosis of soils is important for agricultural and environmental purposes, because there is little data available on the Pantanal-Cerrado-Floresta Amazonica transitional areas. This work evaluated many parameters relative to the fertility, Fe, Mn, Zn, Cu and B bioavailability, and total content of As, Cd, Hg and Pb in soils of the Vale do Guapore, in the south-western region of Mato Grosso. Soil samples were collected in depths of 0-0,2 and 0,20-0,40 m in native vegetation, pasture, annual crop and gold mineration areas. These samples were analyzed for fertility according to Embrapa methodologies and trace elements by the SW3051 methods; and the average results were compared with quality reference values (VRQ) of soils of Sao Paulo stipulated by the Company of Technology of Environment Sanitation (CETESB). The Pb contents in the majority of samples were below the VRQ. In relation to As, many samples showed contents above the VRQ: 45,8% in native vegetation areas; 60% in the gold mineration areas; 28% in annual crop areas; and 44% in the pasture areas. The Cd contents too were above the VRQ: 20,8; 50; 55,5; and 22% for native vegetation, gold mineration, annual crop and pasture areas. Similar behavior was observed for Hg, which presented 75; 65; and 67% for native vegetation; gold mineration; and annual crop and pasture areas, respectively, with mean contents above the VRQ. About pH, around 68% of the samples presented values between 6,1 and 7,0 and the values of base saturation (V) were high (60-80%) for 51,5% of the points sampled. However, the mean P content was short in the whole area. The comparison of As, Cd and Hg contents with the VRQ of soils showed that it is necessary to determine these values for the state of Mato Grosso, keeping in view that the total contents of these elements observed in native areas were superior to the VRQ.

Compaction of an Oxisol and chemical composition of palisadegrass

Compaction is an important problem in soils under pastoral land use, and can make livestock systems unsustainable. The objective of this research was to study the impact of soil compaction on yield and quality of palisade (UROCHLOA BRIZANTHA cv. Marandu). The experiment was conducted on an Oxisol in the State of Mato Grosso, Brazil. Treatments consisted of four levels of soil compaction: no compaction (NC), slight compaction (SC), medium compaction (MC) and high compaction (HC). The following soil properties were evaluated (layers 0-0.05 and 0.05-0.10 m): aggregate size distribution, bulk density (BD), macroporosity, microporosity, total porosity (TP), relative compaction (RC), and the characteristics of crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF) and dry matter yield (DMY) of the forage. Highly compacted soil had high BD and RC, and low TP (0-0.05 m). Both DMY and CP were affected by HC, and both were strongly related to BD. Higher DMY (6.96 Mg ha-1) and CP (7.8 %) were observed in the MC treatment (BD 1.57 Mg m-3 and RC 0.91 Mg m-3, in 0-0.05 m). A high BD of 1.57 Mg m-3 (0-0.05 m) did not inhibit plant growth. The N concentration in the palisade biomass differed significantly among compaction treatments, and was 8.72, 11.20, 12.48 and 10.98 g kg-1 in NC, SC, MC and HC treatments, respectively. Increase in DMY and CP at the MC level may be attributed to more absorption of N in this coarse-textured soil.

Levels of As, Cd and Pb in soils and sediments from gold mining areas in the municipalities of Pontes e Lacerda and Nova Lacerda, in the Vale do Alto Guaporé, (Valley of the High Guaporé ), MT

Soils act as source or drain of trace elements (ETs) in the environment. The study was conducted in three areas of gold mining in the Valley Region of Guaporé, in the counties of Nova Lacerda and Pontes e Lacerda, in the southwestern part of the state of Mato Grosso, having the purpose of assessing the concentration of As, Cd and Pb in sediments and soils at two depths of 0-20 and 20-40 cm. The trace elements (ETs) were determined in graphite furnace after acid extraction according to USEPA SW-846-3050. The soil analysis results were compared with the resolution of CETESB n°. 195/2005 and the sediments with CONAMA 344/2004 and CCME EPC-1999. The average contents of trace elements (ETs) found in sediments were (As 0,413; Cd 0.021; Pb 1.618 mg kg) in the Lavrinha mine; (As 1,343, 0,037 Cd, Pb and 3.198 mg kg) in the Pau a Pique mine; and (As 1,093; Cd 0,020 and Pb: 2,060 mg kg) in the São Francisco mine.. The average contents in soils were (As 0,772; Cd 0,017 and Pb 2, 515 mg kg) in the Lavrinha mine; (As 2,579; Cd 0,021; and Pb 4,373 mg kg) in the Pau a pique mine and (As 0,920; Cd 0,018, and Pb 3,198 mg kg) in the São Francisco mine. The values of As, Cd and Pb in soils and sediments of these areas are below the reference values, according to the Brazilian and Canadian laws.

Atributos químicos, físicos e estoque de cálcio, magnésio, potássio e fósforo em solos de campos de murundus no Brasil

Fields of murundus (FM) are wetlands that provide numerous ecosystem services. The objectives of this study were to evaluate the chemical [organic carbon (OC), P, K + , Ca 2+ , Mg 2+ , Al 3+ and H+Al] and physical [texture and bulk density (Bd)] soil attributes and calculate the organic matter (OM) and nutrient stock (P, Ca, Mg, and K) in soils of FM located in the Guapore River basin in Mato Grosso. Thirty-six sampling points were selected, and soil samples were collected from two environments: the murundu and plain area surrounding (PAS). At each sampling point, mini trenches of 0.5 × 0.5 × 0.4 m were opened and disturbed and undisturbed soil samples were collected at depths of 0–0.1, 0.1–0.2, and 0.2–0.4 m. In the Principal Component Analysis the variables H+Al (49%) and OM (4%) were associated with the F1 component and sand content (47%) with the F2 component. The FM had lower pH values and higher concentrations of K + , P, and H+Al than PAS at all depths (p < 0.05). Additionally, FM stocked up to 433, 360, 205, and 11 kg ha -1 of Ca, Mg, K, and P, respectively, for up to a depth of 0.2 m. The murundu stored two times more K and three times more P than that in the PAS. Our results show that the FM has high sand content and Bd greater than 1.5 Mg m -3 , high acidity, low OC content, and low nutrient concentrations. Thus, special

Desenvolvimento de capim Xaraés e fertilidade de Latossolo Vermelho adubado com resíduo ruminal bovino

This study evaluated the application of increasing doses (0, 10, 21 and 84 Mg ha-1) of the dried bovine rumen residue (BRR) (90.00% DM) or wet (7.16% DM) with nitrogen content (N) of 1.43% in the DM, considering that only 33% of N of the BRR would be available to meet the requirement of Urochloa brizantha cv. Xaraes of 0, 50, 100 and 400 kg N ha-1, on the fertility of an Oxisol (pH in water, exchangeable cations, P, N and organic matter) after 30 days of organic fertilization and on the production of dry biomass (BIO), height, levels of nitrogen (N) and crude protein (CP) after 60 and 120 days of cultivation of the Xaraes. A completely randomized design was used in 4 x 2 factorial (four doses of fertilizer BRR and two conditions of RRB dry matter) with three replications. The application of increasing doses of dry or wet BRR increased linearly (p < 0.05) the levels of N, P, K and organic matter of soil. Different doses of dry or wet BRR increased linearly (p <0.05) the dry BIO, the contents of N and CP of the grass Xaraes after 60 days of cultivation, but a quadratic effect (p < 0.05) was verified for the contents of N and CP of the grass Xaraes after 120 days of cultivation. Thus, the Urochloa brizantha cv. Xaraes presented higher production of dry BIO, regardless of the harvest period and the condition of the DM of BRR at the application time.