RESUMEN
Surface sediment from three Louisiana Lakes containing overlying water layer spiked with 2 microg/g (2 ppm) mercury were incubated under oxygenated (air) and nonoxygenated (N2) conditions for determining the impact of oxygen status of overlying water on methylation of Hg in surface sediment from these lakes. The added mercury resulted in a greater than ten fold increase in methyl mercury (MeHg) as compared to native concentration of MeHg. The increase in methyl Hg production was less in sediment in which overlying water was exposed to oxygen rather than nitrogen. Results suggest that methyl Hg production would be less in lakes containing an oxygenated water column. In parallel microcosm studies without added mercury. MeHg decreased in sediment when redox potential of sediment suspension was increased from -200mV to +50mV. Results of these studies demonstrate the importance of oxygenation or redox condition of surface sediment on mercury methylation and demethylation. Sediment conditions, which either reduce methylation or enhance demethylation in surface sediment, will limit the bioavailability of MeHg to the aquatic environment.
Asunto(s)
Sedimentos Geológicos/química , Compuestos de Metilmercurio/análisis , Compuestos de Metilmercurio/química , Contaminantes Químicos del Agua/análisis , Monitoreo del Ambiente , Louisiana , Mercurio/química , Metilación , Oxidación-Reducción , Abastecimiento de AguaRESUMEN
The effectiveness of various oxidants or redox buffers (ferric chloride, sodium hypochlorite, potassium permanganate, hydrogen peroxide and potassium nitrate) for controlling or reducing emission of reduced sulfur gases (hydrogen sulfide, carbonyl sulfide, methanethiol, dimethyl sulfide and carbon disulfide) produced from sewage sludge collected from a wastewater treatment plant was studied under laboratory conditions. Sludge was treated with 0, 30, 300 and 1000 ppm of each chemical and changes in emission of the various reduced sulfur gases were monitored over a period of 24 hours. Potassium permanganate and hydrogen peroxide were shown to be the best chemicals for reducing hydrogen sulfide (the dominant reduced sulfur gas measured) emission. Sodium hypochlorite was also effective in reducing hydrogen sulfide emission followed by the ferric chloride addition. Since considerably smaller quantities of other reduced sulfur gases were evolved, the influence of the various chemical additions were not as significant as the reduction observed for hydrogen sulfide emission. Potassium permanganate and hydrogen peroxide were effective in reducing methanethiol and dimethyl sulfide emission. To a lesser degree sodium hypochlorite and ferric chloride also reduced emission of these two reduced sulfur gases. Potassium nitrate had no effect on reducing hydrogen sulfide or any of the reduced sulfur gases over the 24 hour experimental period. Each of the chemicals used in the study had a little or no effect in reducing carbonyl sulfide and carbon disulfide emission from the sludge material.
Asunto(s)
Contaminación del Aire/prevención & control , Odorantes , Aguas del Alcantarillado/química , Azufre/química , Eliminación de Residuos Líquidos , Gases , Oxidantes/química , Oxidación-Reducción , VolatilizaciónRESUMEN
The effects of different sulphonylureas on the electrical cardiac activity were studied in 145 rabbits and in 103 rats as well as in 278 digitalis-treated, non-smoker non-insulin-dependent diabetics on the same therapy at least during the previous three months. In rabbits and rats glibenclamide (0.0032-100 mumol. kg-1) decreased, while tolbutamide and carbutamide (0.008-1000 mumol. kg-1) increased strophantidin toxicity and myocardial ischaemia induced transitory ventricular fibrillation dose-dependently. The differences between the dose-response curve of glibenclamide and those of tolbutamide or carbutamide were significant. In digitalized non-insulin-dependent diabetics, multifocal ectopic ventricular beats could be observed in none among the 80 glibenclamide-treated diabetics, while in 12 cases of the 71 tolbutamide and in 10 cases of the 61 carbutamide treated diabetics. Two of the 66 non-insulin-dependent diabetics receiving only diet and 7 of the 278 age and sex matched, non-smoker, metabolically healthy patients had multifocal ectopic ventricular beats. No significant difference could be found between the therapeutical groups. It was concluded that instead of tolbutamide, glibenclamide must be preferred in digitalis-treated diabetics, when metabolic control is not satisfactorily achieved by diet and regime alone.