Developing a fluorimetric sequential injection methodology to study adsorption/desorption of glyphosate on soil and sediment samples

This paper describes the development of a sequential injection method to automate the fluorimetric determination of glyphosate based on a first step of oxidation to glycine by hypochlorite at 48 degrees C, followed by reaction with the fluorogenic reagent o-phthaldialdehyde in presence of 2-mercaptoethanol in borate buffer (pH > 9) to produce a fluorescent 1-(2`-hydroxyethylthio)-2-N-alkylisoindole. The proposed method has a linear response for glyphosate concentrations between 0.25 and 25.0 mu mol L(-1), with limits of detection and quantification of 0.08 and 0.25 mu mol L(-1), respectively. The sampling rate of the method is 18 samples per hour, consuming only a fraction of reagents consumed by the chromatographic method based on the same chemistry. The method was applied to study adsorption/desorption properties in a soil and in a sediment sample. Adsorption and desorption isotherms were properly fitted by Freundlich and Langmuir equations, leading to adsorption capacities of 1384 +/- 26 and 295 +/- 30 mg kg(-1) for the soil and sediment samples, respectively. These values are consistent with the literature, with the larger adsorption capacity of the soil being explained by its larger content of clay minerals, while the sediment was predominantly sandy. (C) 2011 Elsevier B.V. All rights reserved.

Pendimethalin determination in natural water, baby food and river sediment samples using electroanalytical methods

This work describes the electroanalytical determination of pendimethalin herbicide levels in natural waters, river sediment and baby food samples, based on the electro-reduction of herbicide on the hanging mercury drop electrode using square wave voltammetry (SWV). A number of experimental and voltammetric conditions were evaluated and the best responses were achieved in Britton-Robinson buffer solutions at pH 8.0, using a frequency of 500 s(-1). a scan increment of 10 mV and a square wave amplitude of 50 mV. Under these conditions, the pendimethalin is reduced in an irreversible process, with two reduction peaks at -0.60 V and -0.71 V. using a Ag/AgCl reference system. Analytical curves were constructed and the detection limit values were calculated to be 7.79 mu g L(-1) and 4.88 mu g L(-1), for peak 1 and peak 2, respectively. The precision and accuracy were determinate as a function of experimental repeatability and reproducibility, which showed standard relative deviation values that were lower than 2% for both voltammetric peaks. The applicability of the proposed methodology was evaluated in natural water, river sediments and baby food samples. The calculated recovery efficiencies demonstrate that the proposed methodology is suitable for determining any contamination by pendimethalin in these samples. Additionally, adsorption isotherms were used to evaluate information about the behavior of pendimethalin in river sediment samples. (C) 2010 Elsevier B.V. All rights reserved.

Evaluation of the QuEChERS Method and Gas Chromatography-Mass Spectrometry for the Analysis Pesticide Residues in Water and Sediment

A method for the determination of pesticide residues in water and sediment was developed using the QuEChERS method followed by gas chromatography - mass spectrometry. The method was validated in terms of accuracy, specificity, linearity, detection and quantification limits. The recovery percentages obtained for the pesticides in water at different concentrations ranged from 63 to 116%, with relative standard deviations below 12%. The corresponding results from the sediment ranged from 48 to 115% with relative standard deviations below 16%. The limits of detection for the pesticides in water and sediment were below 0.003 mg L(-1) and 0.02 mg kg(-1), respectively.

Field report from sediment coring in peat for landscape analysis in Hjaltadalur, Skagafjörður, north Iceland 2010 : Sediment drilling in Hólar, Vidvik and Kolkuós, Hjaltadalur

This field report presents fieldwork undertaken in Hjaltadalur, Skagafjördur, northern Iceland during summer 2010. The main aim was to initiate coring in selected mires in order to determine the composition of organic material and sediments in the mires, sub-sample for sedimentological and palaeoecological analyses, and initiate advanced landscape analysis of Hjaltadalur. Three mires were selected for sediments coring in Hjaltadalur: Ástunga close to Kolkóus, Hólakot at Viðvik, and Hólar. All three represented a landscape transect in NW to SE direction, from close to the coast to valley interior, i.e. close to the old settlement at Hólar.

Vägprojektering för minskade drift- och underhållskostnader : Brister och möjligheter

För att kunna bygga en ny väg måste den först planeras och projekteras. Vägplanering innebär att man undersöker förutsättningarna för att bygga vägen t.ex. konsekvenser för miljö, samhälle, trafiksäkerhet, framkomlighet, tillgänglighet samt tekniska och ekonomiska förutsättningar. Vägprojektering innebär att man bestämmer vägens utformning på detaljnivå t.ex. vägsträckning, bredd, profil, vägutrustning, etc. Planering och projektering av vägar är en komplicerad process med tanke på alla komponenter som en väg består av samt alla aspekter som man måste ta hänsyn till under vägens livstid. Planerings- och projekteringsprocessen utgör en avvägning av många aspekter för att hitta den optimala lösningen. Drift- och underhållsåtgärder på vägnätet föranleds ofta av att problem uppstått på ett fåtal ställen. Kostnaden för att åtgärda dessa ställen kan uppgå till stora belopp under vägens livslängd. Med en lämpligare utformning av vägen hade dessa problem i en del fall sannolikt kunnat undvikas. Bland de aktörer, som är inblandade i planerings- och projekteringsprocessen, finns det olika åsikter om orsaken till att man inte tar tillräcklig hänsyn till drift- och underhållaspekten under planerings- och projekteringsskedet. Vissa aktörer tycker att det är projektörens kunskapsbrister som leder till att vägen får olämplig utformning avseende drift och underhåll. Andra tycker att det är en kombination av olika brister hos väghållaren. Dessa brister kan då finnas i såväl planerings- och projekteringsprocessen som i drift- och underhållsprocessen. Denna rapport presenterar resultatet för en förstudie som har utförts inom doktorandprojektet ”Vägprojektering för minskade drift- och underhållskostnader”. Syftet med förstudien var att identifiera brister och problem på övergripande nivå som leder till att man inte tar tillräcklig hänsyn till drift- och underhållsaspekten vid planerings- och projekteringsprocessen. Ett annat syfte med förstudien var att föreslå förändringsbehov inom planerings- och projekteringsprocessen genom att analysera de identifierade problemen, analysera verksamheten vid planering och projektering, analysera verksamhetens mål, formulera nya mål för verksamheten och fastställa de nödvändiga förändringsbehoven.

Calibration Strategies Designed For Long Term Sediment Transport Modelling

The presented work deals with the calibration of a 2D numerical model for the simulation of long term bed load transport. A settled basin along an alpine stream was used as a case study. The focus is to parameterise the used multi fractional transport model such that a dynamically balanced behavior regarding erosion and deposition is reached. The used 2D hydrodynamic model utilizes a multi-fraction multi-layer approach to simulate morphological changes and bed load transport. The mass balancing is performed between three layers: a top mixing layer, an intermediate subsurface layer and a bottom layer. Using this approach bears computational limitations in calibration. Due to the high computational demands, the type of calibration strategy is not only crucial for the result, but as well for the time required for calibration. Brute force methods such as Monte Carlo type methods may require a too large number of model runs. All here tested calibration strategies used multiple model runs utilising the parameterization and/or results from previous run. One concept was to reset to initial bed elevations after each run, allowing the resorting process to convert to stable conditions. As an alternative or in combination, the roughness was adapted, based on resulting nodal grading curves, from the previous run. Since the adaptations are a spatial process, the whole model domain is subdivided in homogeneous sections regarding hydraulics and morphological behaviour. For a faster optimization, the adaptation of the parameters is made section wise. Additionally, a systematic variation was done, considering results from previous runs and the interaction between sections. The used approach can be considered as similar to evolutionary type calibration approaches, but using analytical links instead of random parameter changes.

Numerical Simulation Of Sediment Transport And Bedmorphology Around A Hydraulic Structure On A River

Scour around hydraulic structures is a critical problem in hydraulic engineering. Under prediction of scour depth may lead to costly failures of the structure, while over prediction might result in unnecessary costs. Unfortunately, up-to-date empirical scour prediction formulas are based on laboratory experiments that are not always able to reproduce field conditions due to complicated geometry of rivers and temporal and spatial scales of a physical model. However, computational fluid dynamics (CFD) tools can perform using real field dimensions and operating conditions to predict sediment scour around hydraulic structures. In Korea, after completing the Four Major Rivers Restoration Project, several new weirs have been built across Han, Nakdong, Geum and Yeongsan Rivers. Consequently, sediment deposition and bed erosion around such structures have became a major issue in these four rivers. In this study, an application of an open source CFD software package, the TELEMAC-MASCARET, to simulate sediment transport and bed morphology around Gangjeong weir, which is the largest multipurpose weir built on Nakdong River. A real bathymetry of the river and a geometry of the weir have been implemented into the numerical model. The numerical simulation is carried out with a real hydrograph at the upstream boundary. The bedmorphology obtained from the numerical results has been validated against field observation data, and a maximum of simulated scour depth is compared with the results obtained by empirical formulas of Hoffmans. Agreement between numerical computations, observed data and empirical formulas is judged to be satisfactory on all major comparisons. The outcome of this study does not only point out the locations where deposition and erosion might take place depending on the weir gate operation, but also analyzes the mechanism of formation and evolution of scour holes after the weir gates.

Post-earnings announcement drift no mercado de ações brasileiro

Este trabalho busca testar a eficiência do mercado de ações brasileiro através da identificação da existência de post-earnings announcement drift, fenômeno já bastante estudado e reproduzido no mercado norte-americano. Segundo a literatura existente a respeito do assunto, a informação contida na divulgação de resultados de uma firma é relevante para a formação de preço de suas ações. Além disso, os retornos anormais acumulados de ações de firmas que divulgam resultados com “surpresas positivas” possuem tendência positiva por algum tempo após a divulgação do resultado. Por outro lado, os retornos anormais acumulados de ações de empresas que divulgam resultados com “surpresas negativas” possuem tendência negativa por algum tempo após a divulgação do resultado. A identificação de post-earnings announcement drift no mercado acionário brasileiro pode ser de grande utilidade para a estruturação de estratégias de arbitragem e gestão de portfólios. Após uma revisão teórica, o resultado é apresentado e se mostra parcialmente consistente com a literatura existente.

Kinetics and Adsorption Isotherms of Bisphenol A, Estrone, 17 beta-Estradiol, and 17 alpha-Ethinylestradiol in Tropical Sediment Samples

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

SEDIMENT BIOTURBATION POTENTIAL of UCA RAPAX and UCA URUGUAYENSIS AS A RESULT of THEIR FEEDING ACTIVITY

Bioturbation of mangrove sediments by Uca uruguayensis (Nobili, 1901) and U. rapax (Smith, 1870) was compared based on the grain-size composition and organic content in surface sediment around the burrow and feeding pellets in two mangrove zones of the Sao Vicente Estuary, state of São Paulo, Brazil. For each species, 25 burrows with active crabs were selected. All pellets within a 15-cm radius of each burrow were carefully collected; samples of substrate were taken; and the crab occupant was excavated, sexed, and measured for carapace width (CW). The number of spoon-tipped setae on the second maxilliped of each species was estimated; U. uruguayensis showed more of these setae than U. rapax. For both species, the sediment post-processed by feeding activity (feeding pellets) showed a similar increase of coarser fractions and a smaller organic content. However. U. uruguayensis was more efficient in removing organic matter (88.1%) from the sediment than U. rapax (37.5%). These results suggest that different numbers of spoon-tipped setae on the second maxillipeds of the fiddler crabs do not affect the potential for grain-size selection, but result in differing abilities to remove organic matter from the sediment.

Integrated sediment quality assessment in Paranagua Estuarine System, Southern Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)