Climate change and future scenarios for palisade grass production in the state of São Paulo, Brazil

The objective of this work was to analyze future scenarios for palisade grass yield subjected to climate change for the state of São Paulo, Brazil. An empirical crop model was used to estimate yields, according to growing degree-days adjusted by one drought attenuation factor. Climate data from 1963 to 2009 of 23 meteorological stations were used for current climate conditions. Downscaled outputs of two general circulation models were used to project future climate for the 2013-2040 and 2043-2070 periods, considering two contrasting scenarios of temperature and atmospheric CO2 concentration increase (high and low). Annual dry matter yield should be from 14 to 42% higher than the current one, depending on the evaluated scenario. Yield variation between seasons (seasonality) and years is expected to increase. The increase of dry matter accumulation will be higher in the rainy season than in the dry season, and this result is more evident for soils with low-water storage capacity. The results varied significantly between regions (<10% to >60%). Despite their higher climate potential, warmer regions will probably have a lower increase in future forage production.

Crescimento e produtividade do mamoeiro fertirrigado com fósforo por gotejamento superficial e subsuperficial

O presente trabalho teve como objetivo determinar o efeito da freqüência de aplicação de fósforo via água de irrigação por gotejamento superficial e subsuperficial no crescimento e na produtividade do mamoeiro (Carica papaya L.), do grupo Formosa, cultivar Tainung nº 1. As variáveis de crescimento avaliadas foram: índice de área foliar, altura da planta e diâmetro do caule, mediante amostragens aos 39; 69; 182 e 317 dias após o plantio (DAP). O experimento seguiu um delineamento em blocos casualizados, num esquema fatorial 2 x 4 + 1, com três repetições e doze plantas por parcela. Foram avaliados dois sistemas de microirrigação (gotejamento subsuperficial e superficial) e quatro freqüências de fertirrigação com fósforo (30; 60; 90 e 120 dias) via água de irrigação, utilizando como fonte o fosfato monoamônico (MAP), mais um tratamento com adubação convencional via sólida, utilizando o superfosfato simples. As análises de variância indicaram que houve efeito significativo do sistema de irrigação aos 317 DAP na variável de crescimento altura da planta e efeito da interação sistema x freqüência de fertirrigação no diâmetro do caule aos 69 DAP e índice de área foliar aos 182 DAP. O fósforo, quando aplicado via fertirrigação nas freqüências de 30 e 60 dias, nos sistemas superficial e subsuperficial, proporcionou melhores resultados nas variáveis de crescimento e na produtividade. Em todas as variáveis de crescimento analisadas, bem como na produtividade, os tratamentos fertirrigados foram, em média, superiores ao tratamento com adubação convencional.

Aplicação superficial de calcário em pomar de laranjeira pêra em produção

A citricultura paulista é a maior do mundo, sendo de extrema importância manejos que visem a aumentar e melhorar a produção de frutos. Com vistas a isso, foi instalado na EECB (Bebedouro-SP), em um Latossolo Vermelho distrófico típico, um experimento com a aplicação de cinco doses de calcário calcinado, em julho/99. Os efeitos no solo foram avaliados através de amostragens nas camadas de 0-10; 10-20; 20-40 e 40-60 cm, aos 6; 12; 18; 24; 30 e 36 meses. Através da utilização de modelos lineares, constatou-se que os efeitos da aplicação superficial de calcário no solo podem atingir até a camada de 20-40 cm, sendo a saturação por bases uma ótima característica indicadora da ação do corretivo. A máxima reação do calcário ocorreu entre 12 e 18 meses após a aplicação. O estado nutricional das plantas e a produção foram alterados, significativamente em função da aplicação superficial de calcário, sendo que melhores respostas da planta foram obtidas com saturação por bases de aproximadamente 50%.

Salt stress change chlorophyll fluorescence in mango

This study evaluated the tolerance of mango cultivars 'Haden', 'Palmer', 'Tommy Atkins' and 'Uba' grafted on rootstock 'Imbú' to salt stress using chlorophyll fluorescence. Plants were grown in modified Hoagland solution containing 0, 15, 30, and 45 mmol L-1 NaCl. At 97 days the parameters of the chlorophyll fluorescence (F0, Fm, Fv, F0/Fm, Fv/Fm, Fv'/Fm', ΦPSII = [(Fm'-Fs)/(Fm')], D = (1- Fv'/Fm') and ETR = (ΦPSII×PPF×0,84×0,5) were determined. At 100 days, the leaf emission and leaf area, toxicity and leaf abscission indexes were determined. In all cultivars evaluated, in different degree, there were decreases in photochemical efficiency of photosystem II, enhanced concentrations from 15 mmol L-1 NaCl. The decreases in the potential quantum yield of photosystem II (Fv/Fm) were 27.9, 18.7, 20.5, and 27.4%, for cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba', respectively, when grown in 45 mmol L-1 NaCl. It was found decreases in leaf emission and mean leaf area in all cultivars from 15 mmol L-1 NaCl. There were increases in leaf toxicity of 33.0, 67.5, 41.6 and 80.8% and in leaf abscission of 71.8, 29.2, 32.5, and 67.9% for the cultivars 'Haden', 'Palmer', 'Tommy Atkins', and 'Uba' respectively, when grown in 45 mmol L-1 NaCl. Leaf toxicity and leaf abscission were not observed in 15 mmol L-1 NaCl. The decrease in Fv/Fm ratio were accompanied by decreasing in leaf emission and increased leaf toxicity index, showing, therefore, the potential of chlorophyll fluorescence in the early detection of salt stress in mango tree.

Correlação entre a estrutura atômica superficial e o processo de adsorção-dessorção reversível de hidrogênio em eletrodos monocristalinos Pt(111), Pt(100) e Pt(110)

Platinum is widely used as electrode in electrocatalytic processes, however the use of polycrystalline electrodes introduces a series of variables in the electrochemical system due to the aleatory contribution of all the crystallographic orientations with different surface packing of atoms. Single crystal platinum electrodes of low Miller index present surface structure of high regularity and serve as model to establish a correlation among the macroscopic and microscopic properties of the electrochemical interface. Therefore, the main aim of this work is the study of the voltammetric profiles of the reversible adsorption-desorption of hydrogen on Pt(100), Pt(110) and Pt(111), in order to correlate the electrochemical properties of each different orientation with the surface atomic structure.

Adaptação no método do peso da gota para determinação da tensão superficial: um método simplificado para a quantificação da CMC de surfactantes no ensino da química

The discussion based on surfactant cleaning action is commonly used in chemistry classrooms for the comprehension of theoretical concepts related to surface tension and micelle formation. The experimental quantification of surface tension of aqueous solutions of surfactants provides the practical instruments for this discussion. The present paper describes a simplification on the common apparatus employed for the drop-weight method, making the determination of surface tension accessible to any chemistry lab. The surface tension of various liquids and the critical micelle concentration, CMC, of three commercial surfactants were measured with this modified method, and proved to be consistent with literature values.

Métodos de preparação de nanopartículas metálicas suportadas em carbono de alta área superficial, como eletrocatalisadores em células a combustível com membrana trocadora de prótons

Fuel cells are attracting much interest as efficient and clean energy conversion devices. The main components of low temperature fuel cells are the electrocatalysts used to promote the anodic and cathodic reactions, which are based on platinum and platinum alloys. These electrocatalysts are normally prepared in the form of metal nanoparticles supported on a conductive material, usually high surface area carbon, to improve catalyst utilization and reduce cost. This work presents and comments some methods used presently to produce these electrocatalysts. The performances of the produced electrocatalysts are compared to that of state-of-the-art commercial E-TEK electrocatalysts.

Estudo do efeito do tratamento superficial por moagem sobre as propriedades das partículas de uma liga de hidreto metálico

This work reports results of studies on the electrochemical and structural properties of a Ti/Zr-based metal hydride alloy covered by Ni and LaNi4,7Sn0,3 powder additives by ball milling. The effect of this treatment is investigated for the activation time, hydrogen storage capacity and equilibrium pressure, cycling stability and the hydration/dehydration kinetics. Charge and discharge cycles show a significant decrease of the activation time due to an increase of the active area caused by the milling treatment, independent of the additive. However, other results have evidenced little effect of the milling surface treatment on the charge storage capacity, hydrogen equilibrium pressure, and hydration/dehydration kinetics, for both the Ni and LaNi4,7Sn0,3 covered materials.

Medidas de tensão superficial pelo método de contagem de gotas: descrição do método e experimentos com tensoativos não-iônicos etoxilados

Surface tension knowledge of surfactants aqueous solutions is important during amphiphilic molecule manufacturing and new product development, as feedback information to handle synthesis parameters to target performance. Drop counting method is an interesting simplification of drop weight method for surface tension measurements. A simple laboratory measurement device, with capability for temperature control, was assembled to allow investigation of ethoxylated surfactants. The implementation of the method was preceded by a detailed investigation of two factors that may affect the measured surface tension: drop formation velocity and surfactant ethoxylation degree. The limitations of the method are discussed on this basis.

Adsorção e propriedades de volume de misturas binárias água álcool: um experimento didático com base em medidas de tensão superficial

An undergraduate physical chemistry experiment based on the drop counting method for surface tension measurements is proposed to demonstrate adsorption isotherms of binary aqueous solutions of ethanol, n-propanol, and n-butanol. Excess surface is obtained by the derivative of surface tension taken with respect to alcohol activity, after this activity calculation using van Laar equation. Laboratory class contents are surface tension, excess surface, percolation of hydrogen bonds, micelle, activity, and ideal solution.

Reator de UV-Ozônio com lâmpada a vapor de mercúrio a alta pressão modificada para tratamento superficial de óxidos transparentes condutivos utilizados em dispositivos poliméricos eletroluminescentes

An UV-Ozone reactor was developed with an ignition tube extracted into HID mercury lamp used to irradiation on zinc oxide (ZnO) and fluorinated tin oxide (FTO) films for PLEDs devices. Different exposures times were used. In contact angle measurements revealed better results for ZnO and FTO by 15 and 5 min, respectively. In Diffuse Reflectance Infra-red Fourier Transformed (DRIFT) spectroscopy allowed the observation of water, hydrocarbon and carbon dioxide adsorbed on the untreated TCO surfaces. After the UV-Ozone treatment the contaminants were significantly reduced or eliminated and the PLEDs devices decreased threshold voltages in comparison with respectively untreated TCOs.

Transporte de glifosato pelo escoamento superficial e por lixiviação em um solo agrícola

Glyphosate was determined in runoff and leaching waters in agricultural soil that received an application of active ingredient and was exposed to simulated intensive rain conditions. The concentrations decreased during the simulation period and the concentrations of the runoff were higher than those achieved in the samples of leaching waters. The concentrations were lower than the pattern in the Brazilian Regulation MS N. 518/2004 for drinking water. The transported load of the applied active ingredient by the leaching was of 15.4% (w/w) and for the runoff was of 1.7% (w/w).

Distribuição de Zn, Pb, Ni, Cu, Mn e Fe nas frações do sedimento superficial do Rio Cachoeira na região sul da Bahia, Brasil

The metal distribution in the surface sediment fractions of the Cachoeira River was evaluated based on the fractionation method using a five-step sequential extraction. The determination of metals was made by flame atomic absorption spectrophotometry (F AAS). Zn, Pb and Cu exhibit higher concentrations in the residual fraction of the sediment from sites that receive discharges from urban and industrial zones. High levels of Ni (60 ± 1 to 447 ± 9 µg L-1) were found in the river water, which may be detrimental to the "health" of rural communities that utilize the river water for domestic purposes without treatment.

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.