George L. Baughman

Comparison of photochemical behavior of various humic substances in water: I. Sunlight induced reactions of aquatic pollutants photosensitized by humic substances

Abstract Humic substances are shown to photosensitize transformations of several types of synthethic chemicals that do not photoreact when exposed to sunlight in distilled water. In most cases, photoproducts were the same in colored natural waters and in solutions of soil-derived humic substances, including those obtained commercially. Kinetic studies in sunlight indicated that the efficiencies of the reactions photosensitized by humic substances of various origins were the same within a factor of 2.

Transformation of dyes and related compounds in anoxic sediment: kinetics and products.

The reactions of several to, anthraquinone, and quinoline dyes were studied in settled sediments. Several 1-substituted anthraquinones were lost from sediment with half-lives less than 10 days. For monosubstituted 1-amino and 1-methylamino (Disperse Red 9) compounds, the most stable product is the intramolecularly hydrogen-bonded anthrone. The 1,4-diaminoanthraquinone (Disperse Violet 1) and 1,4-diamino-2-metoxyanthaquinone (Disperse Red 11) were lost without formation of detectable products except for a demethylation product of the latter. Both the anthrone from Disperse Red 9 and the demethylation product of Disperse Red 11 reacted with halflives of a few months, but other major products were not detected

Comparison of photochemical behavior of various humic substances in water: II. Photosensitized oxygenations

Abstract The photochemical oxygenation of 2,5-dimethylfuran (DMF) in water was studied under a variety of reaction conditions employing various humic substances as photosensitizers. As predicted by theory, the reactions at low DMF concentrations were first order with respect to DMF, and the reaction rate constants were directly proportional to the average light intensity and to the concentration of humic substance. The rate of oxygenation photosensitized by the humic matter from a river was independent of hydrogen ion activity in the pH 5 to 9 range. Wavelength studies indicate that oxygenations photosensitized by humic substances are induced by ultraviolet and blue radiation. Rate constants computed for this photosensitized reaction in sunlight were in close agreement with experimental values. Calculations also show that the ratio of the sunlight rate constants to total visible solar irradiance (400 to 700 nm) is approximately constant. Therefore, it may be possible to calibrate rate constants for photosensitized reactions in terms of commonly measured units of visible light intensity such as foot candles.

Partitioning of selected polychlorinated biphenyls to natural sediments

Abstract The partitioning of two polychlorinated biphenyl mixtures (Aroclor 1016 and 1242) and two tetrachlorobiphenyl isomers (2,5,3′,4′ and 2,6,2′,6′ tetrachlorobiphenyl) between water and four natural sediments was evaluated in laboratory investigations. For both Aroclor mixtures, the extent of adsorption was comparable on all four natural sediments studied. For individual isomers, partitioning was comparable with that observed for the mixtures. Both particle size distribution and total organic carbon were important factors in determining the extent of partitioning for the two isomers; but in the case of the mixtures, there was no correlation with organic content.

Prediction of Photochemical Transformation of Pollutants in the Aquatic Environment

ABSTRACT Mathematical models that predict concentration-time profiles can be used to assess potential exposure of aquatic organisms to toxic pollutants. Such models integrate quantitative descriptions of individual transport and transformation processes that affect pollutant behavior in the environment. Discussion in this paper focuses on methods for prediction of one important transformation process, photolysis by the action of sunlight. Two general classes of photochemical transformation are direct photolysis , initiated by direct absorption of light by the pollutant, and indirect or sensitized photolysis involving light absorption by natural “photosensitizers.” At concentrations normally encountered in natural waters, direct photolysis is described by first order rate expressions. Equations that employ solar irradiance, quantum yields, and absorption spectra of pollutants are used to predict photolysis rates as a function of time of day, season, location, and water depth. Sensitized photolysis can proceed by a variety of mechanisms including energy transfer, sensitizer-pollutant reaction, and oxidation involving singlet oxygen or free radicals. Recent studies have indicated that singlet oxygen, a species that rapidly oxidizes certain pollutants such as polycyclic aromatics, is generated photochemically in a variety of natural waters. Although qualitative evidence indicates that other types of sensitized photolysis are important, mechanisms and equations required for quantitative description of these processes are still poorly defined.

Dynamics of pollutant photoreactions in the hydrosphere

ZusammenfassungUm kinetische Daten über den Einfluß von Sonnenlicht auf das Verhalten von Verunreinigungen in Seen und Flüssen zu erhalten, wurden licht-induzierte Umwandlungsreaktionen von organischen Chemikalien untersucht. Es ergab sich, daß die Humuskomponente der in natürlichen Wässern gelösten organischen Substanzen auf zwei Arten die aquatischen Photoreaktionen beeinflußt. durch Schwächung des Sonnenlichtes und durch Sensibilisierung der Photoreaktionen. Humus-sensibilisierte Photoreaktionen von Furanen, Sulfiden, Dienen, nitroaromatischen Verbindungen u.a. werden diskutiert. Ein Überblick wird gegeben über die Wirkung aquatischer Partikel auf die Geschwindigkeit der Photoreaktion von Verunreinigungen. Suspendierte Sedimente wirken hauptsächlich durch Lichtabschwächung und Streuung auf die Photolysegeschwindigkeit. Algen, Diatomeen und Bakterien beschleunigen lichtinduzierte Umwandlungen von Anilinen und Phosphorthioat-Insecticiden, was darauf hindeutet, daß photobiologische Prozesse eine bedeutende Rolle beim Abbau gewisser Verunreinigungen in aquatischer Umgebung spielen könnten. Es wird gezeigt, daß Nitrat, Eisenverbindungen und Peroxide für die Sonnenlicht-induzierte Oxidation freier Radikale von Verunreinigungen in natürlichen Wässern verantwortlich sein können.SummaryLight-induced transformations of organic chemicals have been studied to provide kinetic results concerning the influence of sunlight on pollutant behavior in lakes and rivers. A review of these studies shows that the humus component of the dissolved organic matter in natural water affects aquatic photoreactions in two important ways: by attenuating sunlight and by sensitizing photoreactions. Studies of humus-sensitized photoreactions of furans, sulfides, dienes, nitroaromatic compounds, and other chemicals are discussed. Research concerning effects of aquatic particulates on pollutant photoreaction rates are reviewed. Suspended sediments mainly affect photolysis rates through light attenuation and scattering. Algae, diatoms, and bacteria accelerate light-induced transformations of anilines and phosphorothioate insecticides, suggesting that photobiological processes may play a significant role in the breakdown of certain pollutants in aquatic environments. Evidence is presented that nitrate, iron species, and peroxides may be responsible for sunlight-initiated free radical oxidations of pollutants in some natural waters.

Identification of reactive dyes in spent dyebaths and wastewater by capillary electrophoresis-mass spectrometry.

Capillary electrophoresis with diode array detection and mass spectrometry combined with solid-phase extraction were employed for the identification of reactive vinylsulfone and chlorotriazine dyes and their hydrolysis products in spent dyebaths and raw and treated wastewater. Recoveries of dyes from treated wastewater as their tetrabutylammonium ion-pairs using C18 reversed-phase cartridges ranged from 81 to 121%. Detection limits in sewage effluent of the different dyes and hydrolysis products ranged from 23 to 42 microg/l. The method was successfully applied to the detection of the hydrolysis products of five reactive dyes in influents and effluents of a municipal wastewater treatment plant receiving dyehouse effluents.

Analysis of anionic metallized azo and formazan dyes by capillary electrophoresis-mass spectrometry

Capillary electrophoresis-mass spectrometry was applied to the separation of several anionic dyes containing copper(II), chromium(III), or cobalt(III) as part of the dye molecule. The dyes were separated using a 110 cm x 50 microm uncoated fused-silica capillary and a 5 mM ammonium acetate buffer (pH 9) containing 40% acetonitrile. Excellent separation efficiencies (N = 500,000 plates/column) and low detection limits of 20-50 pg (selected ion monitoring, S/N = 10) were achieved. Mass spectra were acquired at different cone voltages. At low cone voltages (low collision energies), sensitivity was maximized and the mass spectra contained only signals of the (multiply charged) molecular ions and low levels of sodium ion and proton adducts. At higher cone voltages, the 2:1 (ligand:metal) chromium and cobalt dyes showed losses of one of the two dye ligands, accompanied by a reduction of the metal. The copper dyes showed signals due to loss of SO2 and SO3-, but no release of metal. Azo cleavage, otherwise typical of azo dyes, was not observed with the metallized dyes.

Methylmercuric complexes in aquatic systems.

Abstract Equilibrium calculations indicate that methylmercuric ion is almost completely complexed under conditions that exist in fresh waters. Sulfur-bonded complexes, CH3HgS−, (CH3Hg)2S, and CH3HgSR, are likely to be the predominant forms of methylmercury in fresh natural waters. With no reduced sulfur species or sulfhydryl-containing organics present, methyl-mercuric hydroxide or methylmercuric chloride would predominate. Common chemical species such as orthophosphate, ammonia, phenolic groups, and protein amino groups have little effect upon complexation of methylmercury.

Transformation of malathion by a fungus,Aspergillus oryzae, isolated from a freshwater pond

Although fungi proliferate in aquatic environments under conditions of high nutrient availability, their role in pesticide transformation in aquatic ecosystems has received little attention. This has been partly due to the difficulties involved in quantification of fungal growth and metabolism. The purpose of this work was to investigate the rates and products of malathion [0,0-dimethyl S-(I,2 dicarbethoxy)ethylphosphorodithioate] transformation by a fungus, commonly isolated from aquatic environments, in order to indicate whether or not transformation rates and products are similar to those resulting from bacterial metabolism or chemical reaction.