Virgílio Franco do Nascimento Filho

Comparison of metal analysis in sediments using EDXRF and ICP-OES with the HCl and Tessie extraction methods

The work presents an investigation on metal availability in sediments during 13 months using the dispersive-energy X-ray fluorescence (EDXRF) and atomic emission spectrometry with induced argon plasma (ICP-OES) techniques and single extraction (0.1moll(-1) HCl) and Tessies sequential speciation methods. The EDXRF technique could yield essentially the same profile as ICP-OES for the seasonal variation of metals in sediments, but in a more practical way. The sequential extraction procedure (SEP) was more efficient in metal dissolution than single extraction. The Pb, Ni, Al, Cr, and Fe elements were less efficiently extracted with single extraction in relation to sequential extraction. For Co both methodologies were equivalent, but for Cu and Mn the extraction was higher with single extraction. Single extraction does not mobilize Pb, Ni, Al, Cr, and Fe adsorbed on oxides and bound to organic matter. However for Cu and Mn, not only extracted these metals from the four fractions, but it also dissolved part of the fifth fraction (residual). Principal Component Analysis discriminated seasonal variations in the content of several metals, mainly Fe, Co, Ni, and Zn. The mobility of metallic ions in the sediments is conditioned to the seasonal flow of organic and inorganic material coming from the river or by the erosion of adjacent soils.

Processamento da cana-de-açúcar: efeitos sobre a digestibilidade, o consumo e a taxa de passagem

Four crossbred bovines (Zebu x Holstein) fed in nature, hydrolyzed, hydrolyzed sugar cane hay and silage as roughage sources constituting 70% of the diets were used to study the effect of alkali treatment of sugar cane (1.5% of NaOH at 50%) on dietary total digestibility and dry matter intake and rate of passage of sugar canes. The fiber was the most influenced fraction by the alkali treatment and increased at least by 45% of digestibility. The increases of 25.0 and 16.7% on intake of hydrolyzed- (1.5% BW) and hydrolyzed sugar cane hay-based diets (1.4% BW) were probably influenced by the higher fiber digestibility. The estimated values of ruminal and cecco-colon rate of passage and retention time in each treatment did not differ among in nature, hydrolyzed and hydrolyzed sugar cane hay-based diet, whereas the lowest rates (1.5 and 7.4%/h) and highest retention time (71.4 hours) were observed for the hydrolyzed silage. It was concluded that alkali treatment with sodium hydroxide, with or without sugar cane hay, increased fiber digestion of hydrolyzed sugar cane in total tract and increased intake, without effect on passage rate. However, post ensilage of hydrolyzed sugar cane could not show effects.

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)).

Determination of chemical elements in africanized Apis mellifera (Hymenoptera: Apidae) honey samples from the State of Piauí, Brazil

Honey is a food used since the most remote times, appreciated for its characteristic flavor, considerable nutritional value and medicinal properties; however, little information exists about the presence of chemical elements in it. The objectives of this work were to determine the chemical elements present in 38 honey samples, collected directly from beekeepers from the State of Piaui, Brazil and to verify whether they presented any contamination. The chemical elements were determined by means of Total Reflection X-ray Fluorescence. The means of three replicates were: K (109.671 ± 17.487), Ca (14.471 ± 3.8797), Ti (0.112 ± 0.07), Cr (0.196 ± 0.11), Mn (0.493 ± 0.103), Fe (1.722 ± 0.446), Co (0.038), Ni (0.728 ± 0.706), Cu (0.179 ± 0.0471), Zn (0.967 ± 0.653), Se (not detected), Br (not detected), Rb (0.371 ± 0.097), Sr (0.145 ± 0.45), Ba (11.681), Hg (not detected), and Pb (0.863) µg g-1.

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.

On-line preconcentration flow system for multi-elemental analysis by total reflection X-ray fluorescence spectrometry

Abstract A scaled-down preconcentration flow system coupled with total reflection X-ray fluorescence spectrometry is proposed for the simultaneous determination of Co, Cu, Mn, Ni, Pb and Zn. The flow system, assembled with an 11-μl column of AG50W-X8 resin and three-way solenoid valves commanded by a computer program, permits the automatic preconcentration, addition of internal standard (Ga) and the deposition of the eluate on the reflector plate. Interferences due to Na and Ca were evaluated. When compared with conventional flow systems, the proposed approach allows a significant reduction in the consumption of eluent (200 μl per determination) and only 1075 μl of sample is required to obtain enrichment factors of approximately 20. Detection limits of Co, Cu, Mn, Ni, Pb and Zn were improved 11, 13, 13, 12, 17 and 14 times, respectively. The proposed system was applied to analyze human saliva and river water samples. Analysis of a Natural Water Standard Reference Material-1640 (Natural Institute of Standard and Technology) showed excellent agreement with certified values. The recoveries for Co, Cu, Mn, Ni, Pb and Zn in a spiked saliva sample were between 64 and 108%.

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.

Avaliação de indicadores para estimar a digestilidade dos nutrientes em novilhos Nelore alimentados com dietas contendo alto teor de concentrado e fontes nitrogenadas

Six Nellore bulls, with initial body weight of 420 kg, were used to evaluate cromium oxide determined by X-ray fluorescence as an external markers of digestibility. Cromium oxide was compared to internal indicators: indigestible NDF (NDFi) incubated in vitro for 144 hours and acid detergent lignin and total feces collection. Digestibility coefficients of DM, OM, NDF, ADF, CP and EE were estimated. Experimental diets were: 1) soybean meal, in a RDP deficient diet; 2) urea; 3) starea (non protein nitrogen source supposedly of slow release), both diets with adequate RDP. Experimental diets were composed of 80% of concentrate and 20% of forage (in natura sugarcane bagasse) on dry matter basis. Digestibility estimation by using cromium oxide showed similar results with total feces collection. Lignin determination was similar to feces collection when soybean was used; however, when urea and starea were fed, the digestibility coefficient were underestimated. NDFi underestimated digestibility for all nitrogen sources. X-ray fluorescence showed to be a promising technique for cromium determination. Internal markers, NDFi incubated in vitro for 144 hours and the acid detergent lignin did not estimated the indigestible portion of the diet.

Use of cesium-137 methodology in the evaluation of superficial erosive processes

Superficial erosion is one of the main soil degradation agents and erosion rates estimations for different edaphicclimate conditions for the conventional models, as USLE and RUSLE, are expensive and time-consuming. The use of cesium-137 antrophogenic radionuclide is a new methodology that has been much studied and its application in the erosion soil evaluation has grown in countries as USA, UK, Australia and others. A brief narration of this methodology is being presented, as the development of the equations utilized for the erosion rates quantification through the cesium-137 measurements. Two watersheds studied in Brazil have shown that the cesium-137 methodology was practicable and coherent with the survey in field for applications in erosion studies.

Valor nutritivo e estudo cinético do trato digestivo de dietas contendo grãos secos ou ensilados de sorgo de baixo e alto tanino para eqüinos

Four crosbred mares averaging six years and 400 kg BW were allotted to latin square design. The objective was to evaluate the nutritive values and kinetics of digestive tract of dry grains or high-moisture grains silage of sorghum with low and high tannin in the feeding of equines. The treatments consisted of diets containing two hybrids of sorghum grains (low and high tannin) and to methods of conservation (dry an ensiled). Diets were formulated to be isoprotein (12.4% CP) with daily DM intake established in 1.5% BW (hay to concentrate ratio of 50:50). The parameters of gastrointestinal transit were: k1 (passage rate in the large intestine); k2 (passage rate in the stomach); TT (transit time); MRT (mean retention time) and TMRT (mean total retention time). No effect treatment was observed for aCD of DM and starch, whose means values were 54.04 and 98.91%, respectively. A benefic effect of the ensiling of high tannin and high-moisture sorghum grains on digestibility of CP and NDF. The aCD of CP and NDF for diets containing high tannin and dry grains of sorghum was of 49.76% and 32.20% and for diets containing of low tannin sorghum grains (dry and ensiled) and high tannin and high-moisture sorghum grains was of 65.63 and 43.32%, respectively. There was effect only of the conservation method of the sorghum grains (dry versus ensiled) on the TMR, where the value for the diets with silages of high-moisture grains and dry grains was, respectively, of 40.08 and 37.9h. In conclusion, high tannin sorghum dry grains should not be used as the main grain in energetic concentrates for horses, because they reduced the digestion of protein and fiber.