Perfil espacial e temporal de poluentes nas águas da represa municipal de São José do Rio Preto, São Paulo, Brasil

In this manuscript, seasonal and spatial trends of water collected from two sampling places in the Preto River in the Turvo-Grande watershed were evaluated. Water samples were collected during June/07 to July/08 and parameters sulphate, total organic carbon, ammonia, conductivity, dissolved oxygen, temperature, dissolved total solids and nitrate were quantified. Seasonal trend indicated sanitary effluents as a point source of contamination in both sampling points. Vertical trends demonstrated that the Municipal Dam was not stratified and received a diffuse source of pollutants from flooding and agriculture runoffs. It was also verified that there is relatively fast ammonia consumption kinetics having a half-life time of 1.43 h which can explain the low ammonia concentrations found in these aquatic bodies.

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.

Removal of phenol and conventional pollutants from aqueous effluent by chitosan and chitin

The present study deals with phenol adsorption on chitin and chitosan and removal of contaminants from wastewater of a petroleum refinery. The adsorption kinetic data were best fitted to first- and second-order models for chitosan and chitin, respectively. The results of adsorption isotherms showed Langmuir model more appropriately described than a Freundlich model for both adsorbents. The adsorption capacity was 1.96 and 1.26 mg/g for chitin and chitosan, respectively. Maximum removal of phenol was about 70-80% (flow rate: 1.5 mL/min, bed height: 18.5 cm, and 30 mg/L of phenol. Wastewater treatment with chitin in a fixed-bed system showed reductions of about 52 and 92% for COD and oil and greases, and for chitosan 65 and 67%, respectively. The results show improvement of the effluent quality after treatment with chitin and chitosan.

Degradação fotocatalítica de sulfametoxazol, trimetoprima e diclofenaco em solução aquosa

In this work the photocatalytic degradation of sulfametoxazole, trimethoprim and potassium diclofenac was evaluated by using TiO2 and ZnO photocatalysts. In optimized experimental conditions (pH 4, TiO2: 50 mg) the TiO2-photocatalysis allowed an almost total degradation of the studied drugs with mineralization of about 80% at reaction times of 120 min. Some mechanistic differences were observed between TiO2 and ZnO in the degradation study involving potassium diclofenac. At the first reaction times the use of ZnO leads to generation of transient species that strongly absorb in the UV spectral region, a fact not observed in studies involving TiO2.

Determination of polyphenol contents and antioxidant capacity of no-alcoholic red grape products (vitis labrusca) from conventional and organic crops

The polyphenol contents and antioxidant capacity of Brazilian red grape juices and wine vinegars were analyzed. Additionally, it was analyzed the human polyphenol absorption and acute effect in plasmatic oxidative metabolism biomarkers after juice ingestion. The organic Bordo grape juice (GBO) presented a higher level of trans-resveratrol, quercitin, rutin, gallic acid, caffeic acid and total flavonoids then other juices and vinegars as well as antioxidant capacity. The plasmatic polyphenol increased 27.2% after GBO juice ingestion. The results showed that juices and vinegars from Brazilian crops present similar chemical and functional properties described in studies performed in other countries.

Organic and total mercury determination in sediments by cold vapor atomic absorption spectrometry: methodology validation and uncertainty measurements

The purpose of the present study was to validate a method for organic Hg determination in sediment. The procedure for organic Hg was adapted from literature, where the organomercurial compounds were extracted with dichloromethane in acid medium and subsequent destruction of organic compounds by bromine chloride. Total Hg was performed according to 3051A USEPA methodology. Mercury quantification for both methodologies was then performed by CVAAS. Methodology validation was verified by analyzing certified reference materials for total Hg and methylmercury. The uncertainties for both methodologies were calculated. The quantification limit of 3.3 µg kg-1 was found for organic Hg by CVAAS.

Tratamentos dos efluentes gerados na produção de biodiesel

The wastewaters from biodiesel production contain as primarily wastes sodium or potassium soaps, fatty acids, glycerin, alcohol and other contaminants. In general, these waters are chemically unsuitable for release to any water body, so, it is necessary the adoption of techniques for the treatment of this effluent. In this review, electrochemical, biological, physicochemical, and combined treatments reported for the removal of the wastewater containing pollutants come from biodiesel production have been summarized. In addition, the recovery, the reuse, the energy production and the synthesis of new compounds from the organic matter contained in this kind of effluent are also reviewed.

Distribution of chemical compartments of soil organic matter and c stocks of a cambisol from south Brazil as affected by Pinus afforestation

Distribution and stocks of soil organic matter (SOM) compartments after Pinus monoculture introduction in a native pasture area of a Cambisol, Santa Catarina, Brazil, were investigated. Pinus introduction increased soil acidity, content of exchangeable Al+3 and diminished soil nutrients. Nevertheless, soil C stock increased in all humic fractions of the 0-5 cm layer after Pinus afforestation. In the subsurface, the vegetation change only promoted SOM redistribution from the NaOH-extractable humic substances to a less hydrophobic humin fraction. Under Pinus, soil organo-mineral interactions were relevant up to a 15 cm depth, while in pasture environment, this mechanism occurred mainly in the surface layer.

Oxidação eletroquímica do herbicida tebutiuron utilizando eletrodo do tipo DSA

Tebuthiuron (TBH) is a herbicide widely used in different cultures and known for its toxic effects. Electrochemical methods are promising for removing pollutants such as pesticides. This study showed the degradation of TBH using a DSA® anode operated at current densities of 50 to 200 mA cm-2. Removal presented pseudo-first order kinetics while high-pressure liquid chromatography (UV detection) showed two peaks, ascribed to degradation intermediates. The maximum percentage of total organic carbon removed was 12.9%. Ion chromatography revealed that higher concentrations of nitrate and nitrite ions formed with increasing current density.

Dispersive liquid-liquid microextraction based on solidification of floating organic drop for simultaneous separation/preconcentration of nickel, cobalt and copper prior to determination by electrothermal atomic absorption spectrometry

A dispersive liquid-liquid microextraction based on solidification of floating organic drop for simultaneous extraction of trace amounts of nickel, cobalt and copper followed by their determination with electrothermal atomic absorption spectrometry was developed. 300 µL of acetone and 1-undecanol was injected into an aqueous sample containing diethyldithiocarbamate complexes of metal ions. For a sample volume of 10 mL, enrichment factors of 277, 270 and 300 and detection limits of 1.2, 1.1 and 1 ng L-1 for nickel, cobalt and copper were obtained, respectively. The method was applied to the extraction and determination of these metals in different water samples.

A Química na agricultura: perspectivas para o desenvolvimento de tecnologias sustentáveis

Food production and preservation of the environment are among the challenges faced by contemporary society. In Brazil, as in most parts of the world, the possibility of increasing the agricultural area is limited by several factors. Thus, an increase in productivity through the application of innovative technologies is regarded as the best solution to overcome such a problem. For long, chemistry has contributed to agricultural innovations such as synthetic pesticides for pest management. However, due to the well-known adverse effects of these compounds, new "greener" strategies are being explored. Research in chemical ecology, in combination with other emerging sciences, is leading to the development of new technologies such as plant-based pesticides (biopesticides); synthetic pheromones and plant volatile organic compounds, both of them to manipulate insect behavior; chemical elicitors to boost plant resistance; and genetic engineering of plant varieties. In these, chemistry plays an important role in the identification and synthesis of functional compounds. These techniques may be incorporated in integrated pest management programs and may contribute to a sustainable agriculture in the future.

Method for determining the photocatalytic potential of portland cement mortar containing TiO2 for decomposing the pollutant nitrogen monoxide

Photocatalytic materials can minimize atmospheric pollution by decomposing certain organic and inorganic pollutants using sunlight as an energy source. In this paper, the development of a methodology to measure the photocatalytic potential of mortar containing TiO2 nanoparticles is reported. The results indicate that up to 40% of NOx can be degraded by Portland cement mortar containing 30-50% of TiO2, which validates the method developed for evaluating the photocatalytic potential of materials.

Química entre a microcamada superficial oceânica e os aerossóis marinhos

The sea surface microlayer (SML), although poorly understood, is important in biogeochemical cycling and sea - air exchanges; it is a source or a sink for a range of pollutants. In this paper, an overview of sampling techniques and the role of SML in biogeochemical cycles and climate is presented. The chemical and biological nature of the ocean surface film and its interaction with atmospheric aerosols are discussed. Special attention is given to organic constituents, gel-like compounds, surfactants, halogenated compounds, and metals. Estimates of air - sea exchange fluxes-with focus on organic carbon, polycyclic aromatic hydrocarbons, and polychlorinated biphenyls-are compiled. In addition, research gaps in the chemical composition of marine aerosols and their relationship with SML are described.