Showing papers by "Swiss Federal Institute of Aquatic Science and Technology published in 1991"

Oxidation of substituted phenols in the environment: a QSAR analysis of rate constants for reaction with singlet oxygen

Abstract: Substituted phenols can be oxidized by singlet oxygen ({sup 1}O{sub 2}), which is formed in sunlit surface waters, and it has been suggested that this reaction may contribute to the environmental fate of phenolic substances. In aqueous solution, the observed rate of phenol disappearance is due to reaction of both the phenolate anion and the undissociated phenol. In order to quantify the effect of substituents on the rates of these reactions, second-order rate constants have been measured for both species for 22 substituted phenols by use of a model system containing the sensitizer rose bengal. Correlation analysis based on half-wave oxidation potentials, E{sub 1/2}, and on {sigma} constants reveals significant quantitative structure-activity relationships (QSARs) for both the undissociated phenols and the phenolate anions. Ortho- and multisubstituted phenols have been included in the correlations. These QSARs are consistent with the rate-limiting formation of a precursor complex with a small amount of charge-transfer character and can be used to predict additional rate constants for a wide range of environmentally significant substituted phenols.

On multiple-nutrient-limited growth of microorganisms, with special reference to dual limitation by carbon and nitrogen substrates

Abstract: Simultaneous limitation of microbial growth by two or more nutrients is discussed for dual carbon/nitrogen-limited growth in continuous culture. The boundaries of the zone where double-limited growth occurs can be clearly defined from both cultivation data and cellular composition and they can be also predicted from growth yield data measured under single-substrate-limited conditions. It is demonstrated that for the two nutrients carbon and nitrogen the zone of double nutrient limitation is dependent on both the C:N ratio of the growth medium and the growth (dilution) rate. The concept on double-(carbon/nitrogen)-limited growth presented here can be extended to other binary and multiple combinations of nutrients.

Anaerobic degradation of toluene by pure cultures of denitrifying bacteria.

Abstract: Several denitrifying Pseudomonas spp., isolated with various aromatic compounds, were tested for the ability to degrade toluene in the absence of molecular oxygen. Four out of seven strains were able to degrade toluene in the presence of N2O. More than 50% of the 14C from ring-labelled toluene was released as CO2, and up to 37% was assimilated into cell material. Furthermore it was demonstrated for two strains that they were able to grow on toluene as the sole carbon and energy source in the presence of N2O. Suspensions of cells pregrown on toluene degraded toluene, benzaldehyde or benzoate without a lag phase and without accumulation of intermediates. p-Cresol, p-hydroxybenzylalcohol, p-hydroxybenzaldehyde or p-hydroxybenzoate was degraded much slower or only after distinct lag times. In the presence of fluoroacetate [14C]toluene was transformed to [14C]benzoate, which suggests that anaerobic toluene degradation proceeds through oxidation of the methyl side chain to benzoate.

Organotins in Lake Sediment

Abstract: Organotin compounds are entering the aquatic environment due to their use in antifouling paints on boats and from municipal and industrial wastewaters [1]. Tributyltin (TBT) is highly toxic to aquatic life, particularly to marine molluscs (oysters) [2] and gastropods, leading to observed declines of dog-whelk populations on various coasts [3]. Chronic toxic effects on these organisms occur at aqueous concentrations of a few ng/1. TBT, dibutyltin (DBT), and monobutyltin (MBT) have been detected in the aquatic environment. Increased concentrations of TBT in water, sediment, and biota have been linked primarily to pleasure boating activities. In the water column, TBT concentrations were reported to lie in the high ng/1 range for marinas, and in the low to medium ng/1 range for open waters [4, 5]. TBT residues in sediments were found to be considerably higher, typically in the high /~g/kg range [4 6], and total butyltin concentration was shown to decrease with depth in sediment cores [7]. In the water column, TBT is biodegraded by successive dealkylation reactions leading to DBT as the principal degradation product with lesser amounts of MBT [6, 8]. In sediments, degradation was reported to be much slower with half-lives of 4 to 5.5 months [6 8]. To date, little is known about the occurrence and persistence of organotin compounds in sediments. Here, we report on the vertical distribution of a series of butyltins and phenyltins in the sediment of freshwater marinas of Lake Lucerne, Switzerland. The occurrence of phenyltin residues has not been previously reported. By using radiocesium isotopes in the sediment, we derive geochronological data. Con-

Behaviour of Detergent Derived Organic Chemicals in the Glatt River. 1. Alkylphenol Polyethoxylates and Their Metabolites

Abstract: A comprehensive study examing the occurrence and transformation of aromatic nonionic surfactants of the nonylphenol polyethoxylate type and of their metabolites in the Glatt River was performed. The longitudinal river concentration-profile has indicated that secondary effluents from municipal sewage treatment plants were the major source of investigated chemicals into the Glatt River. The majority of nonylphenolic compounds in the Glatt River were in the form of persistent metabolites, the most abundant ones being nonylphenoxy carboxylic acids. Mass flow estimates for various classes of nonylphenolic compounds indicated different metabolic pathways in the river. For nonylphenol polyethoxylates, lipophilic nonylphenol ethoxylates, and nonylphenols partial elimination was observed within the 35 km of river that was examined in the study, while for nonylphenol carboxylic acids a significant formation was observed. The lipophilic metabolites of nonylphenol polyethoxylates were found to be at considerable concentrations in the river sediments (0.24–13.1 mg/kg).

MASAS-Modelling of Anthropogenic Substances in Aquatic Systems on Personal Computers

Abstract: MASAS is a computer simulation program for the evaluation of the dynamic behavior of anthropogenic organic micropollutants in aquatic systems. It allows a user to construct models of successively increasing complexity, and to build system and compound libraries. Transformation and transport processes are described at different levels of resolution, based on the available data for the system and the compound. Empirical and theoretical functions are included in the program to approximate unknown process parameters. The program is being implemented as a user friendly tool for the Apple Macintosh personal computer in Modula-2.