Eduardo Simões de Almeida

Existe convergência espacial da produtividade agrícola no Brasil

This work analyzes the convergence of land productivity for Brazilian regions from 1991 to 2003. It evaluates if there is or not convergence of the agricultural productivity, controlling explicitly for spatial effects. To do so, an exploratory spatial data analysis was previously implemented and the presence of spatial autocorrelation for the land productivity was detected. In addition, spatial econometric models were developed for the convergence analysis.

Produtividade do setor agrícola brasileiro (1991-2003): uma análise espacial

Agricultural productivity is characterized by location patterns, represented by the so-called spatial effects, namely, spatial heterogeneity and spatial dependence. This paper analyzes the spatial effects which exert influence on agricultural land productivity at three points in time – 1991, 1997 and 2003 – at the microregional level, using exploratory spatial data analysis (ESDA). The main finding shows that agricultural productivity is increasingly self-correlated in space, over time. Two high-high (HH) clusters are identified consistently: one of them is located in the State of Sao Paulo and parts of the Center-West region, while the other cluster (HH) lies in the Northeastern Coast.

Comparison of analytical performance of benchtop and handheld energy dispersive X-ray fluorescence systems for the direct analysis of plant materials

The analytical performances of benchtop and handheld energy dispersive X-ray fluorescence spectrometry (EDXRF) systems were evaluated aiming at the direct and simultaneous determination of P, K, Ca, S, Fe, Mn, and Si in plant materials. Pressed pellets of comminuted leaves from 23 varieties of sugar cane were used as laboratory samples. Both systems presented similar figures of merit, and were able to provide useful data for plant nutrition diagnosis. Linear correlation between the elemental mass fractions in the test samples and characteristic X-ray intensities was obtained for all analytes with both types of equipment. Correlation coefficients from 0.9601 to 0.9918 and from 0.9094 to 0.9948 were attained for benchtop and handheld EDXRF, respectively. The coefficient of variation of measurements carried out in 3 different test samples was also appropriate, being lower than 13% for all analytes. Limits of detection were comparable for both systems (20 mg kg−1 for Fe and Mn, and approximately 0.1 g kg−1 for P, K, Ca, S and Si) and permit the evaluation of the mineral nutrition status of sugar cane crop taking into account the critical levels of these elements. The handheld system is a cost-effective and appealing option for those who intend to carry out faster in situ and laboratory analysis with equivalent performance of the benchtop equipment.

Determination of mercury in river water by diffusive gradients in thin films using P81 membrane as binding layer

In this work, a device based on diffusive gradients in thin films (DGT) was evaluated for the determination of Hg(II) in river water. The DGT device was assembled with a cellulose phosphate ion exchange membrane (P81 Whatman) as a binding phase and agarose gel 1.5% (m/v) as a diffusive layer. Laboratory deployments showed that the binding of Hg(2+) ([Hg(DGT)]/[Hg(solution)]) by P81 membrane was more effective (97%) than the Chelex 100 resin (80%).The effect of ionic strength, pH and potential interfering ions on Hg binding with DGT׳s was investigated. The results showed no significant effect on the binding of Hg(II) at pH range from 3.5 to 8.5 and at an ionic strength range from 0.0005 to 0.1 mol L(-1). Uptakes of 50 µg L(-1) Hg(II) by P81 membrane were not affected by Fe, Mn, Zn, Cu, Ca and Mg at the concentration range of 200-1800 µg L(-1). Finally, the DGT device using the P81 as the binding layer was applied for in situ measurements of Hg in river water. For in situ measurements, the labile Hg concentration (from <2 to 13 ng L(-1)) was lower than 10% of the dissolved fraction (from 155 to 446 ng L(-1)).

A hipótese da curva de Kuznets ambiental global: uma perspectiva econométrico-espacial

With the aim of checking the relationship between income growth and global warming, the present study analyzes a global environmental Kuznets curve for a sample of 187 countries through a spatial econometric approach. An EKC for conventional per capita CO2 emissions was run on per capita income and its square value, controlling for per capita exports, per capita energy consumption, a dummy variable indicating the countries that ratified the Kyoto Protocol. The results suggested that there is evidence of an inverted U shaped EKC, that is, growth reduces the environmental impact of economic activity. However, the incorporation of a cubic term for per capita income shows that emissions eventually return to increase at a very high level of growth, leading the estimated EKC has an N shape. Furthermore, another finding was that there are evidences that countries that ratified the Kyoto Protocol reduced significantly their per capita CO2 emissions.

Determination of labile barium in petroleum-produced formation water using paper-based DGT samplers.

A polyacrylamide hydrogel containing the Chelex-100 resin has traditionally been used as the binding agent for the diffusion gradients in thin films (DGT) technique. The Chelex-100 resin, although important for the determination of various transition metals, is unsatisfactory for the determination of alkaline earth metals, particularly Ba. In this paper, a cellulose membrane, treated with phosphate (P81 membrane), was evaluated as a binding agent for DGT devices for the determination of Ba in produced formation water (PFW) samples. In addition, diffusive layers of filter paper (cellulose) were tested to diffuse Ba through the DGT devices. Experiments to evaluate the key variables of the technique (pH, deployment time, and ionic strength/salinity) were performed. The Ba sampled by these DGT devices was measured using inductively coupled plasma optical emission spectrometry. Aiming to generate information (related to bioavailability of Ba) on the reuse of PFW for irrigation, the determination of Ba in onshore and offshore samples was performed. The new approach was effective for determination of Ba in onshore samples. To determine Ba in offshore samples, it was necessary to use an alternative calibration procedure due to the high NaCl concentration in these samples.

Determination of Trace Elements in Honey from Different Regions in Rio de Janeiro State (Brazil) by Total Reflection X-Ray Fluorescence

Trace and minor elements in Brazilian honey were analyzed by total reflection X-ray fluorescence spectroscopy. Up to 12 elements (K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Se, Br, and Sr) were detected in 160 samples of honey from 4 regions of Rio de Janeiro State (Barra Mansa, Teresópolis, northern and southern Nova Friburgo). The results showed the samples from Teresópolis had higher rates of essential and nonessential elements than samples from the other regions, except for Ni. K and Ca were the most abundant elements in all samples, in the range of 116.5 to 987.0 μg g(-1) . Ni, Cu, Zn, Se, and Sr were identified in small concentrations (0.01 to 12.08 μg g(-1) ) in all samples, indicating a low level of contamination in all the regions.

Dinâmica espacial e temporal da inovação no estado de São Paulo: uma análise das externalidades de diversificação e especialização

O trabalho avalia em que medida o grau de especializacao ou diversidade pode afetar o desempenho inovador regional. Alem disso, outros fatores determinantes da inovacao sao considerados, como a capacidade de realizacao de P&D, o nivel de escolaridade e a defasagem temporal da inovacao. A base de dados e organizada em funcao das 63 microrregioes do Estado de Sao Paulo no periodo entre 1996 e 2003, e submetida a modelos de dados em painel espacial dinâmico. Os principais resultados revelam que a diversidade e a especializacao produtiva sao igualmente importantes para explicar o desempenho inovador das microrregioes.

A contribuição da pesquisa para convergência e crescimento da renda agropecuária no Brasil

O setor agropecuario no Brasil passou por diversas mudancas nas ultimas decadas, tanto na composicao das politicas publicas voltadas ao setor, quanto no aspecto tecnologico. Este artigo estuda a influencia dos investimentos em pesquisa agropecuaria para o crescimento economico e a convergencia de renda agropecuaria no periodo de 1986 a 2004. Para isso, utiliza-se um modelo econometrico de efeitos fixos, controlando-se os efeitos espaciais, ou seja, a dependencia espacial e a heterogeneidade espacial. Alem de comprovar convergencia condicional, o modelo revelou que o crescimento do PIB per capita agropecuario foi afetado por variaveis como capital fisico agropecuario, infra-estrutura telefonica, infra-estrutura de armazenagem, credito rural, numero de trabalhadores rurais e externalidades espaciais. Alem disso, ficou evidenciada a importância de P&D agropecuario para o crescimento e convergencia de renda per capita no setor agropecuario.

Direct analysis of plant leaves by EDXRF and LIBS: microsampling strategies and cross-validation

Microsampling strategies were evaluated for the direct analysis of dried sugar cane leaves by energy-dispersive X-ray fluorescence spectrometry (EDXRF) and laser-induced breakdown spectroscopy (LIBS). The analysis by EDXRF was carried out by irradiating each leaf fragment in its middle portion with a collimated 5 mm X-ray spot size for 50 s, allowing the determination of P, K, Ca, S, Fe, Mn and Si. EDXRF was also useful to conclude that 15 leaf fragments (37.5% of the recommended sampling area) were enough for attaining a representative analytical response from the whole diagnostic leaf. Regarding LIBS, which employs a substantial smaller ablation area (i.e., 750 µm laser spot size), sampling strategies were defined by taking into account the microchemical distribution of P, Ca, Mg, Fe, Mn, B and Si in a 9 mm × 9 mm leaf fragment area. The proposed sampling protocol relied on the interrogation (rastering) of 3 equally spaced sampling lines in each leaf fragment with 48 accumulated laser pulses per line (Nd:YAG at 1064 nm, 5 ns, 10 Hz, 50 J cm−2) perpendicular to the leaf midrib. This strategy enabled the simultaneous determination of P, K, Ca, Mg, Fe, Cu, Mn, Zn, B and Si by LIBS. Cross-validation between LIBS and EDXRF for P, K, Ca, Fe, Mn and Si predicted mass fractions presented high linear correlation coefficients of up to 0.9778 (selecting 15 leaf fragments per diagnostic leaf from 10 different sugar cane varieties). The results provide insights into a novel and promising strategy for direct and fast plant nutrition diagnosis, fostering further studies for in situ analysis of fresh leaves, strengthening the implementation of Precision Agriculture and Green Chemistry concepts.