Estudo multivariado de solos urbanos da cidade de Teresina

The concentrations of Cu, Pb, Zn, Cr, Ni, Al, Mn and Fe were measured by atomic absorption spectrometry, of 19 topsoil samples collected in the Teresina city urban area to discriminate natural and anthropic contributions and identify possible sources of pollution. The average concentrations of Cu, Zn, Pb and Cr of the urban soils were 6.11, 8.56, 32.12 and 7,17 mg/kg-1, respectively. Statistical analysis techniques, such as principal component analysis (PCA) and hierarchical cluster analysis (HCA), were used to analyze the data. Mn, Ni and Cr levels were interpreted as natural contributions, whereas Pb, Zn and, in part, Cu were accounted for mainly by anthropic activities. High Pb levels were observed in the ancient avenues.

Adsorção de glifosato sobre solos e minerais

Glyphosate, an enzyme inhibitor herbicide, has been widely used around the world in agriculture. Dr. John Franz from Monsanto Corporation (USA) discovered glyphosate in 1970. It has been showed that glyphosate is strongly adsorbed by inorganic soil components especially aluminium and iron oxides, and the phosphate group is involved in this interaction. The inactivation of glyphosate in soils can last for days or even months depending on soil characteristics. The addition of phosphate from fertilizers can displace glyphosate from the soils and this could be the cause of decreased productivity of some crops.

Distribuição de mercúrio em diferentes solos da Bacia do médio Rio Negro-AM: influência da matéria orgânica no ciclo biogeoquímico do mercúrio

Soils play an important role in the biogeochemical cycle of mercury as a sink for and source of this metallic species to atmospheric and hydrological compartments. In the study reported here, various types of soil were evaluated to ascertain the influence of parameters such as pH, organic matter content, Fe, Al, sand, silt, clay, C/H, C/N, C/O atomic ratios, and cation exchange capacity on the distribution of Hg in Amazonia's mid-Negro River basin. The data obtained were interpreted by multivariate exploratory analyses (hierarchical cluster analysis and principal component analysis), which indicated that organic matter plays an important role in mercury uptake in the various soils studied. The soils in floodable areas were found to contain 1.5 to 2.8-fold higher Hg concentrations than those in non-floodable areas. Since these soils are flooded almost year-round, they are less available to participate in redox processes at the soil/atmosphere interface. Hence, floodable areas, which comprise humic-rich soils, accumulate more mercury than non-floodable soils, thus playing an important role in the biogeochemical cycle of Hg in Amazonia's mid-Negro River basin.

Mercúrio total em solos de manguezais da Baixada Santista e Ilha do Cardoso, estado de São Paulo

Total Hg content in soils of Baixada Santista, affected by different sources of pollution, and Cardoso Island, which is almost free of anthropogenic activities, were determined by CVAAS. To explain the fate of Hg in the ecosystem, pH, Eh, AVS, Stotal and Total Organic Carbon were also obtained throughout the soil profiles. With the exception of two sampling sites the average content of Hg in samples obtained for Baixada Santista was 0.34 ± 0.20 mg kg-1, which was close to the average data at Cardoso Island (0.30 ± 0.21 mg kg-1). Both of them were below the limit established by CETESB - 0.50 mg kg-1.

Utilização de solos locais para tratamento de efluentes do refino de petróleo contendo metais

The employment of local soils for extraction of metallic elements was evaluated through batch tests to treat wastewaters generated in a petroleum refinery plant in southern Brazil. Clay and organic carbon content and clay mineralogy provide these soils, in principle, with moderate metal retention capacity. The following retention order was established: Cr3+ > Pb2+ > Cu2+ > Hg2+ > Cd2+, with total amount of metals retained varying from 36 to 65 meq kg-1. The results show the high efficiency of local soils for extracting metals from liquid effluents through sorption and precipitation processes under acid pH conditions.

Estudo comparativo de métodos para a determinação da concentração de carbono em solos com altos teores de Fe (Latossolos)

Soil organic matter (SOM) plays an important role in physical, chemical and biological properties of soil. Therefore, the amount of SOM is important for soil management for sustainable agriculture. The objective of this work was to evaluate the amount of SOM in oxisols by different methods and compare them, using principal component analysis, regarding their limitations. The methods used in this work were Walkley-Black, elemental analysis, total organic carbon (TOC) and thermogravimetry. According to our results, TOC and elemental analysis were the most satisfactory methods for carbon quantification, due to their better accuracy and reproducibility.

Ensaios para determinar a (Bio)disponibilidade de chumbo em solos contaminados: revisão

Incidental ingestion of contaminated soils is a major route of Pb uptake by humans, especially by children. Lead speciation in soils controls its bioavailability. Bioavailability assessment requires the determination of the amount of absorbed lead if a contaminated soil is ingested. In vivo tests, which employ animals, are considered the best model to infer absorption of Pb. But they have some logistic limitations and several authors proposed in vitro methods, which simulate conditions of human digestion. Many of them present results which correlate with in vivo essays. Several authors consider in vitro tests a good and reliable alternative to infer lead bioavailability.

Produção de matéria seca e de grãos por plantas de feijoeiro (Phaseolus vulgaris L.) cultivadas em solos tratados com metais pesados

This work aimed at evaluating the contents of extractable Cd, Pb, Zn and Cu with a solution of DTPA (diethyleneaminopentacetic acid) and to relate them with the production of dry material and grain production of bean plants under two conditions of experimentally contaminated soil materials with Cd, Pb, Cu and Zn: (i) samples of distrofic red latosol and (ii) humic yellow-red latosol. A decrease in the yield of dry matter was observed for all treatments, if compared with the zero-dose control sample; the grain yield was affected for the soil samples treated with Cd and Cu but only slightly for those treated with Pb and Zn.

Espectroscopia Mössbauer na caracterização de compostos ferrosos em solos e sua relação com retenção de fósforo

The chemical role of iron-bearing compounds on the dynamics of phosphorus in selected Brazilian latosols was investigated. The iron oxides were characterized in an attempt to assess their main chemical-mineralogical properties influencing the ion sorption mechanisms in those pedosystems. It was found that increasing total iron contents tend to increase the phosphorus adsorption capacity in the selected soils. 110 K-Mössbauer data reveal that the dominant iron oxides are hematite and goethite. Particularly for the yellower soil samples some prominent doublets, more certainly due to superparamagnetic relaxation, may be assigned to corresponding fractions of relatively small-sized particles.

Biodegradação de tolueno e óleo de pescado em solos impactados utilizando surfactantes químico e biológico

The process of biodegradation of soils contaminated by animal (raw fish oil) and mineral (toluene) origin compounds was studied, verifying the influence of adding biosurfactants and chemical surfactants and nutrients in the media. The highest removal rate of fish oil was 59.47% obtained in the experiments containing biosurfactant and biostimulate in 90 days process. The highest removal rate of toluene was achieved in 14 days for experiments containing biosurfactant, chemical spreading and biosurfactant with biostimulation, showing great influence of evaporation on the process. The use of surfactants has shown to increase the contaminant bioavailability due to its higher degradation rate.

Nutrientes (K, P, Ca, Na, Mg e Fe) em sedimentos (solos aluviais) e cultivares (feijão e milho) de praias e barrancos de rios de água branca: a bacia do purus no estado do Acre, Brasil

The present research highlights the macronutrient abundance in the sediments of beaches and cliffs and cultivates in the river Purus and flowing, southwest of Amazon. The concentrations found in leaves and bean seeds and corn leaves reflect the mineralogical and chemical nature of those rich sediments in K2O and Na2O, which are formed by smectite, illite and K-feldspar. The factors of transfer of the elements in the corn leaves and bean (Ca>K>Na) and bean seeds (Na>K>Ca) demonstrate that the nutrient needs of the cultivate were found appropriately in the sediments (soils) of the beaches and cliffs.

Distribuição e biodisponibilidade de crômio em solos contaminados por resíduos de couro

Samples of soil, water and sediment were collected and analyzed in order to evaluate chromium contamination due to deposition of tannery residues onto soils under different management regimes. The results showed that soils used for sugar cane cultivation were not adversely impacted. However, in the case of mango plantations, variable concentrations of chromium were measured in the soil profile, with 22.2% of values being higher than permitted legal limits, and 38.9% being at levels requiring remediation. Concentrations of bioavailable chromium were lower than the detection limit of the method (0.01 mg of chromium kg-1 of soil), indicating that all of the chromium present in the samples was either complexed or in an insoluble form. Chromium concentrations measured in samples of water and sediments were indicative of low mobility of the metal in soils. The main cause of differences found between soil samples obtained from different cultivations was the type of soil management.

Avaliação de solventes de extração por ultrassom usando-se cromatografia líquida de alta eficiência para a determinação de hidrocarbonetos policíclicos aromáticos em solos contaminados

A method using ultrasonication extraction for the determination of 17 polycyclic aromatic hydrocarbons (PAHs), selected by the USEPA and NIOSH as "consent decree" priority pollutants, in soil by High Performance Liquid Chromatography (HPLC) was studied. Separation and detection were completed in 20 min with a C18 columm, acetonitrile-water gradient elution and ultraviolet absorption and fluorescence detections. The detection limits, for a 10 µL of solution injection, were less than 9,917 ng/g in UV detection and less than 1,866 ng/g in fluorescence detection. Several organic solvents were tested for extraction of the 17 PAHs from soils. Acetone was the best solvent among the three solvents tested, and the order of the extraction efficiencies was: acetone>methanol>acetonitrile. Ultrasonication using acetone as solvent extraction was used to evaluate the biodegradation of those compounds in contaminated soil during a vermicomposting process.

Avaliação da potencialidade de processos pseudo-fenton para remediação de solos contaminados por diesel

The use of the Fenton's reagent process has been investigated for the remediation of a Brazilian soil contaminated by diesel. Laboratory experiments were conducted in batch experiments. Slurries, consisting of 10 g of diesel-contaminated soil and 30 mL of Fenton's Reagent (0.41 mol L-1 H(2)0(2) and 0.18 mol L-1 FeSO4). The experiments were monitored during 24, 48 and 72 h. The efficiency of the Fenton treatment was dependent on the time of contact between soil and Fenton's reagents and matrix characteristics, probably iron content. Data suggested that no iron addition is needed for the application of Fenton-like treatment for the remediation of diesel-contaminated iron rich soils after 72 h reaction.

Matéria orgânica em quatro tipos de solos brasileiros: composição química e sorção de atrazina

Soil organic matter is the main sorptive soil compartment for atrazine in soils, followed in a minor scale by the inorganic fraction. In this study, the soil organic matter quality and atrazine sorption were investigated in four different soil types. The pedogenic environment affected the humification and therefore the chemical composition of the organic matter. The organic matter contribution to atrazine sorption was larger (60-83%) than that of the inorganic fraction. The organic matter capacity in retaining the herbicide was favoured by a higher decomposition degree and a smaller carboxylic substitution of the aliphatic chains.