Fotocatálise heterogênea com TiO2 para oxidação de arsênio e sua remoção de águas por coprecipitação com sulfato férrico

The oxidation of arsenic (As(III) to As(V)) in water samples was performed by heterogeneous photocatalysis using a TiO2 film immobilized inside a photochemical reactor. After oxidation, As(V) was removed from the water samples by coprecipitation with ferric sulfate. The final conditions of oxidation and arsenic removal (TiO2 film prepared with a suspension: 10% (w/v); pH: 7.0; oxidation time: 30 min and Fe3+ concentration: 50 mg L-1) were applied in natural water samples which were supplemented with 1.0 mg L-1 of As(III) to verify the influence of the matrix. After treatment, more than 99% of arsenic was removed from the water.

Aplicação de um corante tiazolilazo como indicador ácido-base e determinação das suas constantes de ionização ácida

The pKa values of the 6-[2´-(6´-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid (Me-BDBD) have been determined at 25 °C, in 0.10 mol L-1 NaCl medium by spectrophotometric method. The SQUAD computer program was used to process experimental data in pH range 1.78 - 11.54 and 290 - 720 nm. The pKa values obtained were 4.60 ± 0.04 and 9.48 ± 0.02. The Me-BDBD reagent was applied as indicator in titration of acid-base. The results were compared with phenolphthalein and bromocresol green indicators. Statistical t and F tests indicated that there were no statistically significant differences between the results for indicators with good agreement.

Degradação de benzeno, tolueno e xilenos em águas contaminadas por gasolina, utilizando-se processos foto-Fenton

In this work the potentiality of photo-Fenton processes were investigated toward the degradation of aromatic hydrocarbons (BTXs) from water contaminated with gasoline. The main results demonstrated that BTXs can be quickly degraded by photo-Fenton process assisted by solar or artificial UV-A radiation, degradation that leads to generation of characteristic phenolic transient species (ie. phenol, hydroquinone and catechol). In the treatment of contaminated water by photo-Fenton processes assisted by solar light, complete BTXs removal was observed in reaction times of about 5 min. Mineralization of about 90% was also observed by applying a multiple H2O2 addition system.

Argilas bentoníticas da península de Santa Elena, Equador: pilarização, ativação ácida e seu uso como descolorante de óleo de soja

Two samples of calcic bentonite of the Santa Elena Peninsula, Ecuador, were pillared with Al13 ions in the ratio of 10, 15 and 20 meq of Al g-1 of clay, calcinated at 573, 723 and 873 ºK and acid activated with 4, 6 and 8 mol L-1 H2SO4. Analyses by X-ray diffraction, X-ray fluorescence, differential and gravimetric thermal, density, surface area and porosity, were applied in order to study the modifications occurred in the crystalline structure of the montmorillonite. The 8 mol L-1 H2SO4 acid-activated 15 meq of Al g-1 of clay at 573 ºK Al-pillared samples indicated the best results in the bleaching of the soybean oil measured by UV-visible spectrophotometer.

Sistema limpo em linha para extração em fase sólida de contaminantes emergentes em águas naturais

A solid-phase in-line extraction system for water samples containing low levels of emerging contaminants is described. The system was specially developed for large volume samples (up to 4 L) using commercial solid-phase extraction (SPE) cartridges. Four sets containing PTFE-made connectors, brass adapters and ball valves were used to fit SPE cartridges and sample bottles to a 4-port manifold attached to a 20 L carboy. A lab-made vacuum device was connected to the manifold cap. The apparatus is robust and less expensive than the typical available system. Its also provides less experimental handling, avoiding cross contamination and sample losses.

Estrogênios em águas naturais e tratadas da região de Jaboticabal - São Paulo

The aim of this work was to analyze 17 β estradiol and estrone, natural estrogenic hormones present in domestic effluents and animal excreta, in the public water supply system of Jaboticabal, SP. The results have shown the presence of estrogens in 22% of the samples in concentrations from 6,8 ng L-1 (treated water) to 30,6 ng L-1 (riverhead) for 17 β estradiol and 600 ng L-1 of estrone (stream), respectively. We concluded that animal wastes, discharges from the wastewater treatment station, and discharges of domestic effluent without treatment from rural proprieties were probably the cause of this contamination.

Alteração da atividade enzimática em organismos aquáticos por poluentes de origem agrícola: uma abordagem geral e sobre a suscetibilidade da fosfatase ácida

The input of agrochemicals in the aquatic compartment can results in biochemical injuries for living organisms. In this context, the knowledge of alterations of enzymatic activities due the presence of agriculture pollutants contributes for the elucidation of the mechanisms of toxicity, implementation of economic methods for monitoring purposes and establishment of maximum allowed concentrations. In the present work, the above considerations are discussed, and data concerning changes in enzymatic function by pesticides and fertilizer contaminants are reviewed. Also, we focused on the acid phosphatase due its susceptibility to several pollutants and diversity in cellular functions.

Avaliação da influência de sulfetos solúveis na complexação do cobre em águas superficiais empregando métodos voltamétricos

In this work a sulfide quantification protocol using voltammetric methods was developed to evaluate the effect of dissolved sulfides on copper complexation. On the basis of pH, sulfide release from the dissociation of specific metal sulfide complexes can be electrochemically measured and then removed (as H2S) by a N2 purge. Cathodic stripping square wave voltammetry (CSSWV) was conducted to quantify Cu sulfides complexes which dissociate at pH < 5.0 during the process of acid titration.

Um sistema microcontrolado para o monitoramento on-line, in situ e remoto de pH, condutividade e temperatura de águas

A portable microcontrolled system is proposed to monitor conductivity, temperature and pH in on-line, in situ and remote way from a water reservoir faraway 200 m. The system comprises two modules: one for data reception (located in laboratory) and another for data acquisition/transmission (located near water reservoir). It uses a microcontroller and a transceiver to remote data transmission/reception by radio frequency. Variations of water parameters were simultaneously monitored without interruption during a period of ten hours with a relative error about 4.0 %. The developed system showed simple, stable, accurate, robust and low-cost to determine parameters of water in field.

Determinação de bifenilos policlorados em soro de cordão umbilical através de extração por hidrólise ácida seguida de cromatografia a gás acoplada a um microdetector de captura de elétrons

The present work describes the determination of polychlorinated biphenyls in 123 umbilical cord serum samples by liquid-liquid extraction method with acid hydrolyze step and analysis by GC-mECD. The analytical method was evaluated with following figures of merit for all PCBs: linearity (>0.997); precision (<12.55%); recoveries (73-119%); limit of detection (0.1 ng mL-1); limit of quantification (0.25-0.5 ng mL-1). The results showed high contamination in the analyzed samples. PCB more frequent was 138 (66.7%), followed by 180 (55.3%) and 52 (51.3%).

Composição química das águas pluviais e deposição atmosférica anual na bacia do Alto Sorocaba (SP)

Two sampling points were chosen and forty samples were collected between January and December 2006 at Alto Sorocaba basin. The rainwater pH varied from 5.46 to 6.36 (Ibiúna) and 5.26 to 6.81 (Itupararanga), being Ca2+ the main ion responsible for controlling the rainwater pH. The ionic concentrations decreased in the following order: Ca2 +>Na+> Mg2+>K+ for cations and SO4(2-)>HCO3->NO 3->Cl- >PO4(3-) for anions. The annual atmospheric deposition appeared to be controlled mostly by following sources: mining activities and cement factories (Ca2+ and HCO3-), natural soil dust (Na+, Mg2+ and HCO3-), fossil fuel burning (SO4(2-)) and agriculture activities (K+, NO3- and PO4(3-)).

Ocorrência de agrotóxicos em águas subterrâneas de áreas adjacentes a lavouras de arroz irrigado

The objective this study was to monitor pesticide residues in groundwater at three different times and in seven regions producing rice in southern Brazil, in the 2007/08 season. Imazethapyr and fipronil were found in all regions studied. All groundwater samples from the Planície Costeira Interna to Lagoa dos Patos and Santa Catarina contained at least one pesticide. The lowest number of contaminated samples were detected in the Southern region. The highest frequency of contaminated samples was found after drainage of the rice fields. Only fipronil exceeded limits of potability, in 27% of samples, according European Community criteria.

O instituto de coimbra e a análise química de águas minerais em portugal na segunda metade do Século XIX

O Instituto, journal published by the Institute of Coimbra (IC), an academic society founded in this city in 1852, contains many articles on hydrology and chemical analysis of water for human consumption, written by well-known Portuguese chemists and physicians. Based on these papers, we analyse the evolution of hydrology in Portugal throughout the second half of the 19th century, with emphasis on the chemical studies of mineral waters by the physicians Augusto da Costa Simões, Francisco Alves and José Epifânio Marques, and by the chemists Joaquim dos Santos e Silva, António Ferreira da Silva and Charles Lepierre, all of them members of the IC.

Análise de risco de contaminação de águas superficiais e subterrâneas por pesticidas em municípios do Alto Paranaíba - MG

A preliminary analyses of the possible contamination of surface and groundwater by the active ingredients of the pesticide products used in the areas with intensive agricultural activities of Alto Paranaíba region, MG, Brazil, was carried out. The active ingredients and formulated products most used in the region were identified and their characteristics of environmental importance were presented. The EPA screening criteria, the groundwater ubiquity score (GUS) and the criteria proposed by Goss were used to evaluate which pesticides might contaminate the local waters. Among the active ingredients studied, several present risks to the local aquatic environment.

Chumbo e zinco em águas e sedimentos de área de mineração e metalurgia de metais

Lead metallurgy at Adrianópolis is the largest environmental problem of Paraná, Brazil. The objective of this study was to determine Pb and Zn levels in water and sediment in two catchments by different extraction methods. The high levels of lead in water in most of samples do not allow the human use. Total Pb concentration as high as 795.3 µg L-1 was observed in Ribeira River bank, in a pluvial water stream flowering from a abandoned factory. Due to the high Pb levels in sediments from some sites (maximum of 24,300 mg kg-1) is recommended to avoid the water turbulence.