Caroline Miranda Biondi

Teores de Fe, Mn, Zn, Cu, Ni E Co em solos de referência de Pernambuco

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 Sertao), 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.

Valores de referência de qualidade para metais pesados em solos do Rio Grande do Norte

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.

Comparison of USEPA digestion methods to heavy metals in soil samples

The use of appropriate analytical methods is of paramount importance for risk assessment and monitoring of potentially toxic metals in soils. In this sense, the objective of this study was to compare the effectiveness of two sample digestion methods, recommended by the Brazilian legislation for the management of contaminated areas (CONAMA 2009), aiming at the determination of environmentally available metal concentrations (USEPA 3050B, USEPA 3051A), as well as a total digestion method (USEPA 3052). Samples from 10 classes of soils were analyzed for Cu, Zn, Cd, Pb, Ni, and Hg. The results showed that the USEPA method 3051A is more efficient than the USEPA method 3050B in the extraction of levels considered environmentally available of Zn, Cu, Cd, Pb, and Ni. Besides providing a higher recovery of these elements, the method requires shorter digestion time, lower consumption of acids, and reduced risk of contamination. The USEPA method 3051A showed greater efficiency in Hg extraction in soils with higher clay content. Therefore, it is suitable for situations where a wide range of soils with different mineralogical characteristics are analyzed or in order to decrease the losses due to volatilization of the element in open systems.

Teores naturais de bário em solos de referência do estado de Pernambuco

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.

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.

Potencial de fertilizantes e corretivos no aporte de micronutrientes ao solo

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.

Dessorção e lixiviação de chumbo em espodossolo tratado com agentes quelantes

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.

COMPARISON OF DIGESTION METHODS TO DETERMINE HEAVY METALS IN FERTILIZERS

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.