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W Klöpffer

Publications and source records attributed to W Klöpffer.

13 recordsLinked to original sources
PubMed2001

A multi media load model for the Baltic Sea.

The background of this work is the international decision process with regard to the selection of chemicals to be assessed with priority. In order to stress the precautionary principle, mass flows were analysed rather than concentrations, threshold values, etc., as preferred by the chemical legislation (which still excludes the marine area). Lindane, hexachlorobenzene (HCB), trichloroacetic acid and its sodium salt, medium-chained chlorinated paraffins and tributyltin (TBT) were selected due to their great relevance for the marine area. Trichloroacetic acid is an interesting model compound on account of its accidental formation by degradation of volatile chlorinated hydrocarbons and during chlorination processes. In addition, a hypothetical compound was modelled, representing a highly water-soluble substance with low vapour pressure. The balancing area is the Baltic Sea and its catchment area. In order to model the substance flows, the 'Input/Output-load model' has been developed. The model quantifies the shift and the distribution of a yearly load of the substance investigated from the terrestrial-limnic into the marine compartment (Baltic Sea). Water-soluble substances, which are usually considered to be of no concern, may enter the sea in great amounts and, if not degradable, remain there. It turned out to be necessary to take into account remobilisation, unintended formation and point as well as line-sources.

Baltic States↗
PubMed1996

Environmental hazard assessment of chemicals and products. Part VI. Abiotic degradation in the troposphere.

The atmosphere constitutes an important sink for many volatile and semivolatile organic compounds (Part II). Even non-volatile compounds may enter the troposphere due to incomplete burning of fuel and industrial, agricultural and traffic-related processes. Depending on vapour pressure, temperature and content of aerosol particles, chemicals prefer the free gas phase, the surface of the particles, or both compartments. Polar compounds (low Henry-coefficient) may dissolve in cloud- and fog droplets. Clearly, the prefered compartment influences the dominant abiotic degradation path. In this paper, a survey is given about the distribution and degradation pathways of chemicals in the troposphere. In the free gas phase of the troposphere, the reaction with OH-radicals is the dominant degradation path. In addition, the reactions with ozone and nitrate-radicals, and direct photochemical reactions also play a role in abiotic degradation.

Aerosols↗
PubMed1993

Bimolecular OH rate constants of organic compounds in solution. 2. Measurements in 1,2,2-trichlorotrifluoroethane using hydrogen peroxide as an OH source.

Semivolatile organic compounds (SOC) occur in the troposphere either adsorbed at aerosol particles or in the free gas phase, depending on temperature, vapor pressure of the compound, and total particular surface. In order to estimate the abiotic degradation of such compounds, the OH reaction rate constant must be known, which cannot be measured directly in the gas phase at the relevant temperature due to experimental difficulties. In the method proposed here, the inert solvent 1,1,2-trichlorotrifluoroethane is used as the reaction medium and hydrogen peroxide as photolytic OH source. Relative reaction rates can be measured, using a reference compound of known kOH air. The relative rates can be converted into absolute ones due to the 1:1 relationship observed by Dilling, Gonsior, Boggs, and Mendoza (1988) Environ. Sci. Technol. 22, 1447-1453, between the relative rates in the inert solvent and those in the gas phase.

Air Pollutants↗
PubMed1991

Bimolecular OH rate constants of organic compounds in solution. 1. Measurements in water using hydrogen peroxide as an OH source.

A method of measuring relative kOH rate constants in water is described. OH radicals are created by photolysis of H2O2, using a Hg high-pressure lamp. Test and reference substances are irradiated for several hours in dilute, aqueous solutions containing 0.1 to 1.0% H2O2. The relative rate constants are determined from the decay of test and reference substances as a function of time, as measured by chemical analysis. Using the known kOH of reference substances, absolute kOH data for test substances are obtained. The following rate constants at 298 K have been measured (liter mol-1 sec-1): kOH (isopropanol) = 2.7 x 10(9) (relative to kOH (methanol) = 8.46 x 10(9]; kOH (toluene) = 6.0 x 10(9); and kOH (p-xylene) = 4.5 x 10(9) (relative to kOH (benzene) = 7.8 x 10(9]. The stationary OH concentrations are on the order of 5 x 10(-14) mol/liter. The kinetics of H2O2 photolysis is discussed, including the estimation of OOH/O2- concentrations during irradiation.

Chemical Phenomena↗
PubMed1988

Testing of the abiotic degradation of chemicals in the atmosphere: the smog chamber approach.

Methods for measuring the hydroxyl-, ozone-, and direct photochemical reactivity of a substance in one specially designed medium size smog chamber are described. Rate coefficients for the reaction of OH with n-hexane, n-heptane, ethene, ethyne, chloroform, trichloroethene, methanol, 2-propanol, benzene, o-xylene, 1,4-dichlorobenzene, 1,2,4-trichlorobenzene, p-chloroaniline, naphthalene, acenaphthene, 1,4-dichloronaphthalene, biphenyl, and fluorenone are given and discussed. An upper limit of 5 X 10(-13) cm3/sec is given for the sum penta- and hexa-chlorobiphenyls (PCB). Rate coefficients for the ozone reaction are given for beta-pinene, limonene, delta 3-carene, cineol, vinyl chloride and 1,3-butadiene. In cases where the literature data are available for comparison, the rate coefficients (kappa OH and kappa O3) reported here compare favorably with the best data reported. The direct photochemical reactivity has been shown to be measurable if the chamber is cleaned carefully. Preliminary results on benzophenone are reported. The methods described here, except that of direct photochemical reactivity, are in agreement with those proposed to OECD. Moreover, part of the Draft OECD Test Guideline (Berlin, 1987) on "Photochemical-Oxidative Degradation in the Atmosphere" is based on work described here and on closely related work in other laboratories (Becker et al., 1984).

Benzophenones↗
PubMed1984

The Environmental Model Segment Approach for estimating potential environmental concentrations. I. The model.

Global distribution models which can be used for evaluating the environmental impact of persistent chemicals are not well suited to assess the environmental impact of less persistent substances; this is due to the fact that the environmental effects caused by the latter substances--if there are any--are only local or regional (close to the emission source), but not ubiquitous. As a tool for estimating potential regional exposure concentrations, the Environmental Model Segment Approach (EMSA) is presented. This model yields information about possible concentrations in reasonable worst-case situations.

Air Pollutants↗
PubMed1984

The Environmental Model Segment Approach for estimating potential environmental concentrations. II. Application of the model to p-dichlorobenzene and trichloroethene.

The Environmental Model Segment Approach introduced in Part I (R. Frische, W. Klöpffer, G. Rippen, and K. O. Günther, 1984, Ecotoxicol. Environ. Safety 8, 352-362) is applied to estimate potential environmental concentrations of p-dichlorobenzene and trichloroethene. Environmental concentrations of these chemicals can be estimated only with difficulty by other models because of many diffuse emission sources emitting mainly into the air. By comparison of the estimated with the measured environmental concentrations it is found that the claim of the model to yield values which apply to reasonable unfavorable environmental boundary conditions is satisfied for the medium air and for the biota (fish). Soil concentrations calculated by means of the model, assuming equilibrium with high air concentrations, are higher than the measured ones, while the calculated water concentrations are lower than the values often measured for river waters. The latter fact may be attributed to direct input of the substances into water which is not being taken into account.

Air Pollutants↗
PubMed1982

A laboratory method for testing the volatility from aqueous solution: first results and comparison with theory.

The mobility of a chemical in the environment is often determined by its volatilization from aqueous solution, especially if it shows poor water solubility and/or high vapor pressure. A small laboratory apparatus is described which allows the simulation of the volatilization process from a stirred water body with well-defined wind velocities and water temperatures. In experiments with naphthalene, pentachlorophenol, trichloroethene, and di(2-ethylhexyl)phthalate, substance concentrations in the water body decrease exponentially, in accordance with theory. Half-residence times are found to be independent of wind velocity (v less than 1 m sec-1) or air humidity, but are strongly dependent on temperature. The measured substance fluxes through the water surface are comparable with theoretical values. In the case of pentachlorophenol, which partly dissociates in aqueous solution, the volatility is controlled by the pH value of the solution.

Diethylhexyl Phthalate↗